Model Engine Maker
Engines => Your Own Design => Topic started by: Brian Rupnow on October 31, 2021, 07:27:23 PM
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Yesterday I finished designing a welding fixture for one of my old customers. Earlier this week I redesigned one of the cylinder heads for my opposed twin engine, seeing how I could relocate the sparkplug up near the top of the cylinder head. I don't really want to mess with a finished engine, so I decided to design a new engine to go with my redesigned cylinder head today. Of course this leads me right down the garden path, and seven or eight hours after I think of it, I've designed it. This engine will be air cooled, and will have two valves and a throttled carburetor. I've put a 2" diameter fan on it, and even designed a fancy fan shroud to support and guard the fan blades. I'm not sure when I will get around to building this one, but winters coming and I will need something to do----
(https://imagizer.imageshack.com/img924/2545/nWVNtb.jpg)
(https://imagizer.imageshack.com/img922/3485/0f9Zkj.jpg)
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And a couple more views so you can see where this one is going---
(https://imagizer.imageshack.com/img922/87/Y5B7PG.jpg)
(https://imagizer.imageshack.com/img922/1671/4NMolm.jpg)
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There's always another idea to try :) :) :) :ThumbsUp: My list is still expanding ::)
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Looks fine to me :cheers:
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Today I made the first part for this engine, the cylinder mounting plate. I used my new bandsaw, and what a wonderful bandsaw it is. It zipped thru the aluminum as if it was butter. This is the first part I have made using the new bandsaw, and all I can say is, I wish I'd bought it ten years ago!!!
(https://imagizer.imageshack.com/img923/3639/OqVkaw.jpg)
(https://imagizer.imageshack.com/img924/6316/BYl6MT.jpg)
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People on another forum commented on how ugly that carburetor arrangement was. The more I looked at it the uglier it looked. I haven't built anything on the head yet, so I was able to go in and change it---carb comes straight out the side now. I left that big air horn that was on the front of the carburetor off too
(https://imagizer.imageshack.com/img922/2361/R0YeSh.jpg)
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Earlier this week I redesigned one of the cylinder heads for my opposed twin engine, seeing how I could relocate the sparkplug up near the top of the cylinder head. I don't really want to mess with a finished engine, so I decided to design a new engine to go with my redesigned cylinder head today.
Brian unless I'm missing something how will this redesigned head get the spark plug near the top of the cylinder on the opposes twin. That has the pushrods above the cylinder which will put the new angled sparkplug at the bottom where it was before :headscratch:
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Your break from engine building did not last very long. It is hard to break old habits/hobbies.
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Jason--Look at the very top model. You will see what I had in mind to turn the cylinder head upside down so the sparkplug would be at the top of the cylinder head.
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But the push rods are at the top on the twin and the rocker support would go right across the spark plug and the original carb layout would also have got in the way? You will still have the arching issue even if you can get the spark plug at the top.
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Jason - he is not remaking the twin, he is designing a new engine, it has the pushrods at the bottom in his new design, look at the pictures in this thread again.
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Chris, see my quote from earlier today, Brian says he has designed this engine to test the redesigned head for the twin as he wants to test the head design before pulling the twin apart unless I'm not reading it right.
"Earlier this week I redesigned one of the cylinder heads for my opposed twin engine, seeing how I could relocate the sparkplug up near the top of the cylinder head. I don't really want to mess with a finished engine, so I decided to design a new engine to go with my redesigned cylinder head today."
No problem with turning the head upside down but I can't see it working on the twin unless the crankcase is also turned upside down to put the pushrods at the bottom like this single.
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Hi jason,
The last sentence of what you quoted says it, he is designing a whole new engine. Not a twin. The cad renders all show a single, pushrods on the bottom.
:cheers:
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I don't disagree with that but as it is the redesigned head also destined for the twin how will it work with the pushrods so close to the plug when Brian makes a pair to put on the twin?
The image i poste din post #9 shows how this redesigned head would fit if put on a twin, see how the plug is positioned. Mine and Brian's are both based on the Nemett design so unless major work was also done to the rockers, rocker bracket and rods there is the problem or arcing and maybe even the rods hitting the plug cap.
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Today was spent making sideplates. They are finished except for tapping a bunch of holes. I have used up my entire day machining these parts, and will do the tapping tomorrow.
(https://imagizer.imageshack.com/img923/8755/YsnfKJ.jpg)
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I had a stroke of good luck this morning. After tapping something like 20 holes, and assembling things, I discovered a length of 01 steel with two cams cut on it. The last time I set up to cut cams I decided to cut over-length while I was in the set-up for use on a potential future engine. The future has arrived!!!
(https://imagizer.imageshack.com/img922/3540/3dee7P.jpg)
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Brian, I very much like the look of this engine! I'll be following along closely!
Mike
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Thanks Mike.---I picked up my cast iron today to make the cylinder. The only material that my supplier had in stock was 2.1" diameter ($25 for 4"). I haven't made the cylinder yet, but this gave me an idea. Without changing anything, I can make it look like this if I want to. This shape harkens back to some of the early model two cycle airplane engines that were made in the 1930's to 1950's. I kind of like it.
(https://imagizer.imageshack.com/img924/5984/PWR3EJ.jpg)
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Brian, that's an interesting shape for the cylinder! Very retro looking.
BTW, what's the bore and stroke of this engine? I didn't see it your previous posts? And as a bonus what's your valve steam and head dimensions?
Thanks!
Mike
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This engine is 7/8" bore x 1.25" stroke. The valve stems are 1/8" diameter and the head of the valve is 3/8" diameter.
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Brian,
I like the progression, improving on an earlier design, seeing the faults/problems & correcting them. Looks good!
Art
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Hi Art--Hope you are doing well!! Are you building anything these days?---Brian
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This morning I made up the main baseplate. This plate has an interesting feature in it. In order to keep everything small, a scallop was cut from the baseplate to clear the 40 tooth cam gear.
(https://imagizer.imageshack.com/img923/8448/GnCQ7I.jpg)
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This afternoon I machined a cast iron cylinder. I like that shape a lot. I've got a temporary clamp on there right now, because I haven't drilled any bolt holes yet. I'll do that tomorrow.
(https://imagizer.imageshack.com/img924/285/AOlBap.jpg)
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Since I have to build a complete cylinder head, I may as well get crazy and make a finned cylinder head. It isn't a lot more work to do this. It just means the overall height of the cylinder head increases by 1/4". The valves get 1/4" longer, and the blue rocker arm support gets 1/4" taller, and the pushrods get 1/4" longer.
(https://imagizer.imageshack.com/img924/416/I6IUHS.jpg)
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Today I drilled clearance holes in the cylinder base flange and drilled and tapped holes in the other end of the cylinder, and attached the cylinder to the frame. I really suffered getting the cylinder bolted to the chassis, and I'm going to change the design drawings of this to give a bit more wrench clearance. I also made the fan housing and installed it. I'm not really sure of how the finished fan and bearings are going to be attached, but for now I will just call it a work in progress.
(https://imagizer.imageshack.com/img922/7302/CSZidU.jpg)
(https://imagizer.imageshack.com/img922/4307/QvX0GI.jpg)
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Brian,
You are making good progress. I like the addition of cooling fins to the head. I'm sure it will run much cooler. I am doing well, staying healthy although I've lost some elderly church friends to Covid. I also have been busy at work, 50 hour weeks since a year ago January. I have been slowly progressing on a mill enclosure but that is about all I'm getting done in the shop. We sold my parents house this summer so that consumed a lot of time and energy both mental and physical. I did get plans for George's flat head V8 and have begun cad on the bell housing. This is taxing my skill level in cad.
Art
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This cylinder head is a complex little guy to machine. None of the individual steps are difficult by themselves, but the hard part is having something to hold onto while you do them.---And if you don't do things in the correct sequence, you can easily "paint yourself into a corner". I do have a plan, and the first part of my plan is using my four jawed chuck in the lathe to turn a "stem" to hold onto with the chuck mounted on my rotary table for all of the following steps.
(https://imagizer.imageshack.com/img924/4664/gQNYja.jpg)
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There is a lot of work to this cylinder head, and I am only about half done with it. However, it's a beautiful day here, sunny and 64 degrees F, so I'm going to put my tools away and take my good wife somewhere for lunch. This is probably one of the nicer days that November will offer, before we have snow up to our armpits. The slots were cut with a slitting saw.
(https://imagizer.imageshack.com/img922/9445/BBWYpe.jpg)
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So here we have most of a days work. I took good wife out for lunch, then came back and started laying out, drilling, and tapping holes and the main 1" counterbore in the cylinder head. So far, so good. I am rather amazed at how small this thing is. That's a standard size pocket calculator laying in the foreground to give you some ides of a size comparison.
(https://imagizer.imageshack.com/img923/4551/7OoufV.jpg)
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Today I finished and mounted the bracket which supports the rocker arms, and finished and mounted the bar which the cooling fan will mount to. The cylinder head is finished except for some cosmetic work.
(https://imagizer.imageshack.com/img922/4434/Mv10ue.jpg)
(https://imagizer.imageshack.com/img923/6673/ODljP0.jpg)
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I have scrapped the old "Rupnow Engine" that I built about 10 years ago, and am gradually salvaging the parts. I have two bronze flywheels that are the right diameter, and I'm thinking of salvaging the outer rims and turning new aluminum centers. I have never made solid flywheels with no holes in them, and I'm thinking of doing that. Many of the old hit and miss water cooled engines had solid webs in the flywheels---I remember. If I don't like them I can always add holes in the webs later. What do you think?
(https://imagizer.imageshack.com/img924/5949/BRqHXy.jpg)
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I like the looks of the parts you have made so far :ThumbsUp:
So for the rest - do what pleases you :cheers:
Per
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I've decided I don't care that much for the solid flywheel web. I have an idea that is easy to machine and makes the flywheel action more visible as they turn. I think this will be what the finished flywheels look like.
(https://imagizer.imageshack.com/img924/5453/Mh4pCM.jpg)
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Today was intake and exhaust day. I had just enough brass around the shop to make these two assemblies. I have to go buy some more 1/2" diameter brass rod to make tappet guides and valve cages with. All or at least most of the brass will get polished as I get deeper into this engine.
(https://imagizer.imageshack.com/img922/753/5miCwx.jpg)
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The morning was spent cutting out the centers of the brass flywheels on the old Rupnow Engine to give me two nice outer rims for my new flywheels, and cutting two aluminum centers from a piece of 3 1/2" diameter aluminum that I had left over from another project. I still have miles to go before I sleep, but so far things are looking good.
(https://imagizer.imageshack.com/img923/1608/2YLNrZ.jpg)
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Today I did something for the very first time!!! Those reliefs in the face of each flywheel are 3/16" deep, and they have a 1/8" radius in the corners. I have always known that there should be radius there. I know the whole tune about sharp inside corners causing stress risers and are more apt to fracture in use. It's just that I never actually did it before. I have about 40 engines running just fine without a radius in the corners of the flywheels. Today I actually ground an HSS tool and machined the radius. The outer brass rims are loctited to the inner aluminum flywheel body (That's why they look dirty--that dirt will all come off with a "clean up" pass in the lathe.) Drilling and reaming the center hole for the shaft is one of the last things I will do.
(https://imagizer.imageshack.com/img924/9349/xAigqy.jpg)
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The flywheels are finished except for keyways, and I like this new variation on round holes cut in the webs. This gives the flywheels an interesting look, and it will still make it highly visible when they are rotating under power.
(https://imagizer.imageshack.com/img923/1811/jGK0vM.jpg)
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Thats a good look on the flywheels.
:popcorn: :popcorn:
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Brian,
Those are some nice looking flywheels. I like the slots in them.
Art
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The flywheels are very interesting looking, Brian. Kind of like an inverse spoke or something :)
Kim
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Just catching up here...
A very nice design Brian! Very appealing to the eye. It's kind of nice seeing something different with the flywheels as well.
:popcorn:
John
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Thanks John--I've built so many engines over the last 12 or 13 years that I'm always looking for a way to make them a bit different and more interesting. I'm not really interested in building something with multiple cylinders, so I try to do something a bit different with every engine I design now. I really like the looks of this new engine.---Brian
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I spent yesterday afternoon and this morning preparing blanks for my 20 and 40 tooth gears, and sawing a slab of 1144 stress-proof steel from the round to make a crankshaft. These are all somewhat brainless operations, but they have to be done, and they take time. The gear blanks are finished outside diameter, thickness, hub diameter and bore, but the hub is a couple of inches too long, which gives me something to grip in the 3 jaw chuck on my rotary table while the teeth are being cut. This over-length hub will be cut off after all of the gear teeth are cut.
(https://imagizer.imageshack.com/img923/7035/HyKxP1.jpg)
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Now I've got to ask---Is that a beautiful thing, or is that a beautiful thing!! Both gears turned out fine, the large gear fits into the cavity prepared for it in the base, and they mesh just the way they are supposed to. I always feel good when I've cut a pair of gears and they turn out the way I had hoped for.
(https://imagizer.imageshack.com/img924/511/PPz7Lv.jpg)
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Happiness is well meshing gears!
:popcorn: :popcorn:
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That IS a beautiful thing ;D :ThumbsUp: :popcorn:
Kim
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That's an interesting take on flywheel design :ThumbsUp: :ThumbsUp: :ThumbsUp:
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Today, since I had to take the sideplates off to fit the crankshaft and camshaft, I decided to go full ball bearings on the crank and camshafts. I was originally going to run the camshaft in bronze bushings, but decided that since I had the correct size of sealed ball bearing, I might as well add the counterbores to the sideplates and go full ball bearing.
(https://imagizer.imageshack.com/img922/25/Bv9fyl.jpg)
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So, at the end of a long and hard fought day, I have a one piece crankshaft and a cam shaft. It's been a long day!!
(https://imagizer.imageshack.com/img923/5167/Cq9TOB.jpg)
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Brian,
It does sound like you had a busy day. I did ball bearings for the cam & crank on my Upshur single. I think you will be glad down the road.
Art
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And here we have a video of all the bits and pieces I machined yesterday, working in harmony. This is my horizontal air cooled engine, 7/8" bore. The cylinder is not mounted in this video, although it is finished.
https://www.youtube.com/watch?v=is736m32OJQ
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This morning I machined a con rod. My digital camera shows up things I missed when sanding the finish.--Oh well, I'll sand it a bit more to take out those tool marks. I always have trouble getting a perfect fit between the big end of the con rod and the crank journal. When I bore the big end of he con rod, my biggest fear is that I will go oversize, and there really is no good fix for that except to make another con rod. So, I end up marginally undersize and then have to screw around for an hour with emery paper and lapping compound to get the fit exactly what I want it to be.
(https://imagizer.imageshack.com/img924/9255/bwaLRe.jpg)
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I am rapidly approaching the point where I have to finish the cylinder and make a piston. When I first designed this engine, I never noticed that I couldn't remove the sideplates without first removing the cylinder, which is a giant PITA. I am going to modify the cylinder flange where the grey arrow is pointing, by putting in a couple of clearance holes in the flange, which will then let me remove the bolt which was previously trapped under the edge of the cylinder flange.
(https://imagizer.imageshack.com/img923/2326/amASfG.jpg)
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This afternoon I managed to machine a piston. I'm tired, and suppers ready.---Enough work for one day!!!
(https://imagizer.imageshack.com/img922/5714/PJFWjt.jpg)
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The engine is completely assembled except for the cylinder head. Everything has a coat of 10w 30 lubricating oil, and the rod cap bolts are snugged up. It is currently out on my workbench being "ran in" at about 450 rpm driven by my electric motor via v-belt. Every 10 minutes I will go out and snug up the con rod bolts a little more. I will let it run for about half an hour and by the end of that time the rod bolts will be fully tightened.
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And here we have one more step in the evolution of an engine. This video was made after the engine was "ran in" for about half an hour, and the rod bolts were progressively tightened after each ten minutes of running in until they were cinched down tight and everything ran freely with no binding. There are no rings on the piston yet.
https://www.youtube.com/watch?v=2HcudYlK3fA
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Brian, great progress! The engine is looking really good. I'm looking forward to seeing it running!
Mike
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Earlier in this thread I mentioned that I had some cams left over from some other engine build. At the time I made those cams, I remember thinking "Since I have to go thru all the motions to make these cams, I'll cut the stock long enough to get a second pair of cams from." The time has come!! ---and I can't be happier. These cams were bored for a 3/8" shaft, and since I had 1/4" sealed ball bearings on hand, the camshaft is 1/4" diameter on both ends but 3/8" diameter where the cams will fit on. Things are very tight where they have to go, but my computer tells me there is just enough room for the cams to fit in there with enough gap between them to let the con-rod swing thru between them. The cam without a hub (for the exhaust) will be pinned to the shaft, the one with a hub will have set screws to hold it in place rotationally.
(https://imagizer.imageshack.com/img924/6056/irIjtQ.jpg)
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No real work accomplished today, other than mounting the cams where they will go on the camshaft and taking a picture of it with one sideplate removed. I have to pick up some 1/2" diameter brass tomorrow to make valve cages and tappet guides from, and a piece of 1/16" diameter drill rod to cross-pin the cam to the camshaft. The woman who runs BusyBee tools in Barrie called and told me about an old fellow in town who built "Steam engines and things" but was too old to work in his shop anymore. I called him and arranged a visit this afternoon and went to see what I might want to buy. He was a nice old fellow of 90, but was selling off all his shop toys. unfortunately, I have everything he has, only bigger and better. I did buy eight small cast steel C-clamps for $25, but that was all I bought.
(https://imagizer.imageshack.com/img922/4070/4SJWdA.jpg)
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You can never have too many clamps! :ThumbsUp:
Kim
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You can never have too many clamps! :ThumbsUp:
Kim
Absolutely not. I have a lot, and still had to borrow a bunch for this glue-up of a boat coaming lamination...
(https://i.postimg.cc/V6M1Gpth/100-0411.jpg)
Sorry Brian, couldn't resist throwing that picture in. Watching along on your build as usual!
:popcorn: :popcorn: :popcorn:
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WOW!!! I've never seen so many clamps together in one place. I have a lot of clamps, but nothing close to that.---Brian
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This morning I went down street and bought my ignition points and condenser. I machined an ignition cam and fitted it in between the sideplate and the flywheel on the side opposite from the timing gears. I flame hardened and quenched my cams in oil, and after clean up got them mounted on the camshaft. The con rod clears the cams when it rotates, by about a gnats hair. (That's about .001"-.003").
(https://imagizer.imageshack.com/img924/4059/ICYNzS.jpg)
(https://imagizer.imageshack.com/img924/7900/MP8joj.jpg)
(https://imagizer.imageshack.com/img923/6858/tuoL60.jpg)
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And at the closing of the day---I have tappet guide bushings made and installed, and valve cages made and installed. Setting out by itself on the end of the engine baseplate, is one lonely valve cage that ended up being too short. I thought it looked too short when I made it (it was the first one) and after doing some checking I found that I had modelled it too short. Ahh poop!!!--Thats why, when you buy a set of drawings from me, the mistakes have already been found and corrected. My original plan was to make the rocker arms out of steel, but I found an offcut of brass that might work for me. I'll figure that one out tomorrow.
(https://imagizer.imageshack.com/img922/8335/T1QOES.jpg)
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One step forward, two steps back. I realized after loctiting the valve cages into the cylinder head that I hadn't put the counterbores in the cylinder head for the valve cage flanges to fit down into. I don't have a great deal of free room in the combustion chamber, so it's pretty important that the flange sets down into a counterbore. Sparky asked me about that, and I thought about it to the point where I pulled the valve cages out of the cylinder head before the Loctite had a chance to set up. What I really need is a 13/32" diameter reamer with no chamfer on the end, with the end drilled and tapped for a pilot. If I put a counterbore in, I have to do the main hole and the counterbore all in one set-up, otherwise I can never get the counterbore concentric with the main hole. After doing some frantic Googling, I find that there are reamers with pilots available, but the reamers all have a chamfer on the end. I need a reamer with no chamfer on the end and with the end drilled and tapped so I can put different size pilots on it. Does anyone know of a commercial source for such a thing? I do have a guy near Barrie who sharpens endmills and drills and can make a custom cutter for me, but he's not cheap.---Brian
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Take a bit of drill rod turn to the required OD and drill and ream for your pilot. Cut a few teeth in the end (file will do) then harden.
This will be like a counterbor that can be used,
Though as there is little sealing going on around the edge you could just as easily use a 7/16" milling cutter
If you want to buy something then look up aircraft counterbores
(https://hosting.photobucket.com/albums/v156/jasonballamy/Hit%20n%20Miss/Third%20Scale%20VJ%20Monitor/.highres/DSC00185_zpsiyydhiel.jpg)
(https://hosting.photobucket.com/albums/v156/jasonballamy/Hit%20n%20Miss/Third%20Scale%20VJ%20Monitor/.highres/DSC00188_zpshwm5zlbf.jpg)
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I used a similar method as Jason's for the internal facings for the main bearings on my Centaur engine, the cutter was made from mild steel with hand filed teeth and case hardened, fitted onto a hand driven mandrel using a ratchet Handel and Socket.
I,m sure you could use similar methods as these.
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Yesterday I was chasing all over the internet trying to find what I wanted but had no luck.---I was calling it the wrong thing!!! This morning I woke up realizing that I should have been searching for a "piloted counterbore". Ran downstairs and checked the internet again and found out that everybody and their dog is selling "piloted counterbores"!!! I started phoning around and then realized that this is Saturday and all the shops are closed. This is a tool I could make but would rather buy. ---Will find out more on Monday.---Brian
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I hope you have success with your counterbore hunt :) In the picture with the contact breaker fitted there looks to be very little clearance between the terminal nuts and the end of the camshaft :thinking: Maybe it's just the camera angle ::)
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It's just the camera angle. I have enough clearance for what I need to do. Nothing big or fabulous machined today. Just a pair of brass rocker arms and axles and hardened 01 steel round contact pads on the end that touches the end of the valves.
(https://imagizer.imageshack.com/img924/9947/zDwCxH.jpg)
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These two little guys that look like tubes are actually the tappets. They have a short counterbore in the end you can see and are solid at the other end where they rub against the cams. The counterbore which is about 0.350" deep holds the end of the pushrods for the valves. The cams have been flame hardened and quenched, and the tappets have also been flame hardened and quenched. They are made form 01 steel and quenched in old motor oil. Once the engine is fully assembled, you won't see these tappets anymore, as they are mostly contained in the tappet guides.
(https://imagizer.imageshack.com/img923/2857/28RJoX.jpg)
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At this point, I don't know exactly how long the pushrods are going to be. I can get a length from my 3D model, but in situations like this I just make the pushrods 1/2" longer than what the computer said and will trim them to length on finished assembly.
(https://imagizer.imageshack.com/img922/5889/wHN3Af.jpg)
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This afternoon I finished all of the fan mechanical parts except the fan blade. The fan is represented by the disc of cardboard, 2 1/4" diameter.---I don't know why it isn't centered in the shroud, but I can move the hole in that brass strap enough to center the fan, and nobody'll know. There is a lot going on in that fan hub. There are two 3/16" diameter ball bearings in there that were originally intended for a router, and a spacer between them.---I like it.
(https://imagizer.imageshack.com/img923/226/5yKxqG.jpg)
(https://imagizer.imageshack.com/img923/8261/2V8kSh.jpg)
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Great progress Brian, hard to keep up! :popcorn:
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Brian,
Everything looks good! Glad you built some flex room in the bracket. The two bearings with the spacer reminds me of my motorcycle's front hub.
Art
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Great job. I am following with great interest.
Mike
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This morning I cut keyways in both flywheels and the crankshaft. I fabricated a fan, silver soldered it to the fan hub, and installed the fan and hub in the fan housing. (It is now centered in the housing). We got about 8" of new snow last night in Barrie.
(https://imagizer.imageshack.com/img923/8936/56jwHU.jpg)
(https://imagizer.imageshack.com/img924/160/lHZQ9W.jpg)
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Some of that snow spilled over across Lake Ontario, but its the scale version, only 1/8" down here.
:popcorn:
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And I think this is it!! I machined the valves this afternoon and I don't think there is anything left to machine. I'm waiting for a piloted counterbore to come in from my supplier so I can finish up the valve cage counterbores in the cylinder head. I have to build some kind of starter hub, and maybe some kind of take-off pulley to attach to the offside flywheel. I have left the "handles" on the valves so I have something to grip when I lap the valve faces into the valve cages.---and oh Yes---I have to make rings.---Cast iron rings.
(https://imagizer.imageshack.com/img922/9468/heYtH2.jpg)
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This is shaping up to being a "no machining day". However, I have modelled a starter hub to one side of the engine and a power take-off pulley to the other side. I might get a chance to machine them today, but I have a lot of "Honey Do" things to look after.
(https://imagizer.imageshack.com/img923/677/Ansa8I.jpg)
(https://imagizer.imageshack.com/img922/4127/iYVjqd.jpg)
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Today was not one of my stellar days. I machined the drive hub and the power take off pulley, and they turned out well. They are held onto the flywheels by four #4-40 socket head capscrews. Drilling the four holes in the starter side flywheel went well. Tapping the first flywheel hole went well. Tapping the second hole didn't. I broke the tap off flush with the surface of the flywheel. After repeated tries to get the broken tap out, I went across town to my tool shop and bought two new taps, two new drills and two 1/16" diameter center cutting carbide endmills. On arriving home, I discovered that my newest Diana Gabbeldon book had arrived, so I made an executive decision to read for the rest of the day. Something of interest--that #4 hand tap and it's drill are about 13 years old, and gets used fairly often. I measured the drill, and it measures at 0.088" diameter. the man who sold me the new taps and drills said that the standard tap drill for a #4-40 bolt is 0.094" diameter.---Who knew--
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The charts I use show the smaller drill size for brass/etc, the larger for steel...
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Once again the old and arthritic have defeated the powers of darkness. It cost me a 13 year old #4-40 tap and a new 1/16" carbide endmill, but in the end the broken tap was removed and the hole was rethreaded at the correct size. (on #4 taps, that trick actually works about one time out of three for me.) So, the engine now has a starter hub on one side and a power take-off pulley on the other.
(https://imagizer.imageshack.com/img924/884/0kgKd5.jpg)
(https://imagizer.imageshack.com/img923/6091/ztqkh4.jpg)
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The engine is almost fully assembled. I had trouble with the first cylinder head, so had to machine a second one. The engine is pretty well finished except for "tidy up" and cosmetic stuff. I'm not sure you can see it, but the camshaft gear ended up hanging below the baseplate by about 0.020", so I've had to epoxy a pair of filler plates on the bottom of the base to raise everything so the gear doesn't rub on the table top. This was an easy change to the engine plans, I just made the base out of 5/8" stock rather than 3/8" thick. I didn't want to remake the baseplate, so the filler plates will do for me---I have to tidy them up to match the contours of the engine base. The only remaining things to be made are the cast iron piston rings.
(https://imagizer.imageshack.com/img922/7331/TOCgNI.jpg)
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Does anyone have a source for 1/4"-32 Helicoils? I've managed to bugger up the threads in my sparkplug hole in the aluminum cylinder head. There is a considerable amount of time and work involved in making these heads, and I don't want to scrap this one. My options are #1--Find someone who manufactures a sparkplug with a 5/16" thread---(That would be my absolute best option)---Or find a source for 1/4"-32 Helicoils,----Or ---Make my own sparkplug with a 5/16" thread. I have made my own sparkplug before, but I don't really want to. Thank You----Brian
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Something more--There are manufacturers of M8 metric sparkplugs, which are very close to 5/16". M8 is 0.315" diameter. 5/16" is 0.312" diameter. Perhaps my easiest fix here is to buy an M8 sparkplug and an M8 tap. They seem to be readily available on the internet.
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Hello Brian:
I have some that are made by Recoil in Australia. Size UNEF 1/4-32, P/N: 34040-32, and uses a 6.5mm drill. I looked on Travers but they did not list this size. It may be worth a call to them. If all else fails, I would be happy to send you a couple via USPS.
Regards....Rick
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Thanks for the kind offer Rick, but tomorrow when the stores are open I'm going to chase some more information on an M8 sparkplug.---Brian
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:ThumbsUp: :ThumbsUp:
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Having a very wimpy day here in the great white north. It has snowed here all day and I haven't been outside. I did a little tidy up work on the cylinder head and the rocker arms, and added a screw to the base to mount the condenser. Other than chasing down an 8mm sparkplug and making rings, the engine is completely "built". I have successfully made and ran cast iron rings in my last two or three i.c. engines, and now I will pull out all the notes I made with respect to 1" diameter pistons and see if there are any real changes to make rings for a 7/8" bore engine.
(https://imagizer.imageshack.com/img922/443/l5uKuA.jpg)
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I ordered an M8 A.C. Delco sparkplug this morning. Cost $14 delivered. I will post a picture when it comes.---Brian
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Paging Steve Hucks---Hi Steve--I am currently building an engine which takes a spark plug with a 1/4"-32 thread. Unfortunately, I screwed up the threads in the sparkplug hole. I don't want to have to remake the head, so I have to either find a sparkplug with a 5/16" thread or build my own custom sparkplug. I much prefer to buy a plug, but haven't had much luck finding one with either a 5/16" thread or a 8mm thread.--Do you sell anything like that, or have a link to where I can buy one.---Brian Rupnow
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I have spent the last two days designing some light automation for an old customer. My new sparkplug will be here on Saturday, and if it doesn't have an 8mm thread I am going to buy a 1/4"-32 helicoil kit from a source provided by Brian Lawrence from Calgary. Tomorrow I will begin the task of making rings for a 7/8" diameter piston. I have the grey cast iron material, but will have to build a new heat treat fixture to accommodate the new ring size. The rings will have the same cross section as the ones I made earlier this year for my T-head engine.
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Todays job was to make a whole armada of 7/8" rings. The material is fine grained grey cast iron, same as I made my other 1" rings from. The o.d. of the ring is turned to 0.875" diameter and polished with 200 grit aluminum oxide strip and a fine India stone, to the best finish I can get. The i.d. is drilled and bored out to leave the rings 0.038" wide axially, which is what I was aiming for. The rings are then parted off, and with some luck will all be slightly greater than 0.045" width, which is the width of the ring grooves in my piston. They will be finished on both sides with some 600 grit aluminum oxide paste on a sheet of glass, rubbing round and round until they are a sliding fit into the ring grooves in the piston. After they are "sized" for width, I will break them in my bench vise. I don't like the fancy fixture which I made to split them because it has a tendency to bend the rings. The last rings I made were cut with a sharp cold chisel, but I felt that doing that deformed the ring on both sides of the cut.
(https://imagizer.imageshack.com/img924/1675/pybDvY.jpg)
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Okay---Just to set the record straight---My rings came off the lathe about 0.003" to 0.004" too wide (as I had planned). I tried polishing that 0.003" to 0.004" off using 600 grit compound on a piece of glass, but it took so long I thought I might not live long enough to get all the rings done.---So---I used a sheet of 600 grit paper laying on a finished cast iron surface, and my handy dandy piece of steel with a 0.875" dia. x 0.025" deep hole in it to hang onto the rings with while I polished them. That went more quickly, but even so it took a lot of scrubbing in circles before the rings came down to 0.044" thick and would fit into the 0.045" grooves in my piston.
(https://imagizer.imageshack.com/img924/6707/LSkGP5.jpg)
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This was something new---The material didn't want to break in the vice. Damn stuff wanted to bend, which is unusual. When I seen that it didn't just snap quickly like other rings have made, I sharpened up my big cold chisel and cut them with the chisel and a pall peen hammer. Whack---and it was done. All the rings in this picture are finished, deburred, and split. Tomorrow I will machine a heat treat fixture and into the heat treat oven they go.---Brian
(https://imagizer.imageshack.com/img922/74/GgFtY4.jpg)
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A couple of picture worthy things going on here. One picture shows a good way of filing the ends of the ring at the ring gap. That is an ignition points file gripped in the vice, and a ring spread over it. I grip the ring with thumb and forefinger of each hand and slide it back and forth on the file, keeping it "square" to the file. Give it 20 strokes and try it for fit in the cylinder--You are aiming for a gap of 0.004" between the ring ends when the ring is slid into the cylinder. Keep track of the number of strokes you take, because whatever it took for that first ring will work for all the rest of the rings. The other picture shows the heat treat fixture I machined this morning, made specifically for 7/8" rings. The drawing I am working from specifies a 0.131" diameter spreader rod. Closest I had was an 0.135" drill, so thats what I used, and the drill will be sacrificed as my spreader rod. Once the cap is bolted on, compressing all of the rings to ensure that they are all laying flat and tight next to each other, the fixture and rings go into my heat treat furnace for 4 hours.
(https://imagizer.imageshack.com/img923/2645/jclJHH.jpg)
(https://imagizer.imageshack.com/img924/9784/cMNSCT.jpg)
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Bad on me---I ordered an M8 sparkplug from A.C. Delco, assuming it would have an M8 thread on it.---it doesn't. It has a 10 mm thread on it. However, all is not lost. As we speak, Stephen Hucks is making me a "one of" sparkplug with a 5/16"-24 threaded end. As luck would have it, I do have a 5/16"-24 tap and die as part of a set I inherited from my dad.
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This chart may be of future help - shows thread sizes for a number of brands. The NGK section, row E, shows an M8x1 thread size.
https://www.gsparkplug.com/identifying-spark-plugs
Chris
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After four hours at 1100 degrees F and then an overnight cooling off period, the fixture comes out of the oven looking like this. There is a lot of black crud on the outside of the fixture (Don't know what it is) but it cleans off very easily. When the fixture is taken apart, the rings come off easily, but they are all stuck together. A bit of finessing with a jacknife gets them apart, and as you can see in the picture they have all taken a set to the new gap of 0.135".
(https://imagizer.imageshack.com/img923/4332/U6bBlD.jpg)
(https://imagizer.imageshack.com/img923/8352/8SFUqE.jpg)
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The rings are on the piston and the piston is back in the engine, and everything goes round and round and up and down like it's supposed to. Out of 8 rings four were damaged, two are on the engine, and I have two left over for some other project.---I would not recommend putting new rings on a new piston to anyone who was looking for a way to pass a tranquil afternoon. There is no cylinder head on the engine right now, but it does have lots of "suck" when I put my hand over the cylinder and turn the engine over with the flywheels.----thats a good thing!!!!
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The engine is basically finished. I'm just waiting for a new sparkplug from Steve Hucks. In the meantime, this things needs a gas tank. I've built about a zillion round gas tanks, but this time I decided to try something a bit different. I went out into my "junk steel closet" and found a piece of 1 1/2" square tube. It will be the basis for my new rectangular tank, and I have a piece of 3 1/2" x 1/2" aluminum flat bar that will make a good sub base to hold the engine and the gas tank.
(https://imagizer.imageshack.com/img922/5015/zZd1OP.jpg)
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Got this far today, and just run out of ambition. Tomorrow I will finish the gas tank and the sub base.
(https://imagizer.imageshack.com/img922/6572/M4jMwF.jpg)
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Today the gas tank was assembled. There is a lot going on here that you can't see, but the ends of the tank are assembled to the body using J.B. Weld. The tank assembly is bolted down to the sub base, and the big vice grip clamp is on there as secondary means of clamping things tight for the next 24 hours. The sub base has had all of the holes added to hold the engine and the gas tank. Tomorrow I will leak test the gas tank, and if all is well I will paint the gas tank and the fan assembly.
(https://imagizer.imageshack.com/img924/9704/R1CzS9.jpg)
(https://imagizer.imageshack.com/img924/7237/IcmbJ6.jpg)
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Every day I do a little bit more (gas tank out spout), but I'm almost out of little things to do. That red gas cap is "borrowed" from another engine, so I still have to make one of them for this tank. The filler spout is made from a 1/2" standard pipe nipple and the cap is machined from a 1/2" standard pipe plug. This is the best solution I have found for a nice big filler spout that has a cap that screws on tight---and yes, there is a one mm hole in that cap.
(https://imagizer.imageshack.com/img923/4112/MFqqed.jpg)
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This morning was "Leaktest morning". I sat the gas tank on a sheet of white printer paper, plugged the outspout, and very carefully filled the tank with naptha gas. Almost immediately my white paper started showing evidence of a leak.---CRAP!!!---Closer investigation showed that it wasn't any of the j.b. welded joints that were leaking. It was leaking where outspout #1 was brazed to outspout #2. Dumped the gas back into the bottle, ran out to my main garage and re-brazed that joint. Second leaktest went fine---No leaks. Then I went to grab a can of dark blue enamel to paint the tank and fan assembly, and sure enough--I have every color under the rainbow, but not dark blue. Wife has gone out to a spa with daughter, and I am baby setting our Grand-dog. I'm not sure what kind of dog it is, but it just looks like a larger version of the old pit bull we had for many years. She's very quiet and well mannered so I talk to her while I'm working and take her out to pee every hour.
(https://imagizer.imageshack.com/img923/3776/f55wuw.jpg)
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At noon I went out and bought a can of Tremclad blue spray enamel and some brass pipe caps to turn into gas tank caps. I machined both gas caps and screwed one onto an engine which I had robbed the cap off and screwed the other onto the tank for this engine. Both tank and fan assembly have been painted, and I see as I posed them for this camera shot that the cap on this current tank needs a bit more paint on it. That was my work for today. My new sparkplug from Steve Hucks should be here this week, and if I have lived a clean and useful life I may have a running engine by this time next week.
(https://imagizer.imageshack.com/img924/3626/hhT6IY.jpg)
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Time to stop and consider---What is left to do? My new sparkplug will be here this week. Head has to be bolted in place and a head gasket made. Valve lash has to be adjusted and valve timing set up with a degree wheel. Ignition timing has to be set. Painted gas tank and fan have to be bolted back into position. I find that with these spray cans of enamel, it is much safer to not handle the painted parts for about three days so as not to get marks all over them during handling them. I have to make a special wrench. It is very, very tight where the base of the cylinder bolts to the vertical frame plate. I can get the bolts started with a ball end Allen wrench, but I'm going to have to fabricate a special wrench to actually get in there and tighten them properly. I will post a picture of the wrench I'm going to have to build-----it's quite simple.
(https://imagizer.imageshack.com/img922/512/U0UkZ9.jpg)
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I like the blue colour (and the dog's chew Trump) :) :) :ThumbsUp:
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In this picture you can see both valves after they have been lapped using 600 grit aluminum oxide paste. The valves have the contacting surface of the face smeared with 600 grit paste and then (while the handles are still attached) they are placed into the respective valve cages and spun back and forth against the valve seats under slight pressure. This is not done with any kind of power tool---fingers only. I hold the handle between thumb and finger and spin them back and forth 10 times--Then lift up. Turn about 30 to 40 degrees then repeat. After a total of 100 "back and forths" they are finished. Then the "handles" are parted off in the lathe. Beyond this point, the valves must go back into the valve cage in which they were lapped. Don't mix them up. Normally, at this point they are finished, but to make it clear for the picture, I put some blue machinists die on the valves, and using the pin vice in the foreground I gave each valve 50 additional turns in their cages with 600 grit. This clearly shows the contact area on the face of the valves, because all the machinists die is worn away at this point.
(https://imagizer.imageshack.com/img924/1749/vOX3AO.jpg)
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Great stuff Brian, I'm about to make up some valves very much like these on my build, going to look back on yours for more tips!
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Brian,
Its good to see the progress you've made. It won't be long now! One of those tools I inherited from my dad is a valve lapping tool. As it's cranked it spins cw then reverses ccw. I just haven't figured how to make it work on the miniature scale.
Art
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Art--I actually designed and built a valve lapping tool as you describe. It was one of those times when I just HAD to build something. It was a few years ago, and I had forgotten all about it until now. I don't think I ever used it, and like many things that don't actually get used, it got cannibalized for parts.---Brian
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Beautiful engine Brain, how did you get cut a nice radius on the cams? I will try it myself.
Alex
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Alex--I did that in my vertical mill, with the cam material held in the 3 jaw chuck on my rotary table. I will post a link here for you.---Brian
https://www.homemodelenginemachinist.com/threads/quick-way-to-cut-a-cam.26315/
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I have reached a point where I can not go any farther with this engine until I receive my new sparkplug. This morning I pulled both flywheels off and set the engine's ignition timing. (I realized after the fact that I didn't have to remove the flywheel from the side with the timing gears on it). Basically, the way I do this is loosen off the set screws in the ignition cam then turn the crankshaft in it's normal rotation until the piston is about 1/16" before top dead center. At this point, without moving the crankshaft, I rotate the cam in it's normal direction until I get a big fat spark from the sparkplug laying out on top of the engine. Then I tighten the setscrews in the cam to lock it in place. After that I turn the engine over by hand a few times just to assure that the spark will come every time the piston reaches that spot 1/16" before top dead center. On my engines I run the ignition points off the crankshaft, so it is a "waste spark system". I get spark every time the piston comes up to top dead center, but it only ignites a charge of fuel every other revolution of the crankshaft.
(https://imagizer.imageshack.com/img923/953/mKB1lb.jpg)
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Now Brian, if you had posted this a few days ago it would have saved me a ton of time getting the timing on my Upshur engine sorted out! (Just kidding, of course, that's a great tip. Thank you.)
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Today I received a new mail order piloted counterbore from Travers. I have a set of counterbores for all of the different socket head cap screws that I have, but this one is a bit different. This one was purchased for the sole use of putting counterbores into aluminum cylinder heads where the flanged end of a valve cage goes, so that the face of the cage sets down flush with the inside of the cylinder head. I have found, by experience, that when I drill and ream these holes, then change to an unpiloted counterbore in the same set-up , that the unpiloted counterbore always pulls a bit to one side and is never totally concentric with the 0.375" reamed hole which the cage body sets into. For this first shot, I have made my own pilot, which sets inside the 7/16" counterbore tool and is held in place with a pair of set screws. I wanted to have the capability of using different size pilots, that's why I didn't buy a one piece counterbore with a pilot ground onto the end of it. It's not too often that I buy a new piece of tooling, so figured it was worth posting about. I'm still waiting for my new sparkplug to arrive, so I can go ahead and finish up the horizontal i.c. that I have been working on.
(https://imagizer.imageshack.com/img924/8779/y6fY8C.jpg)
(https://imagizer.imageshack.com/img923/2514/9WBD1E.jpg)
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That's an interesting gadget, Brian. I've not seen one like that before, with the changeable pilot.
Kim
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I have completely forgot about those. My boss has a few that match standard electronic connectors, but we haven't used them in the last 25 years - hence the lack of memory ...
They do work very well :)
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HURAYYYY-My sparkplugs came in the mail today from Steve Huck--And what beautiful sparkplugs they are!!! I had only ordered one with a 5/16"-24 thread, because I buggered up the threads for 1/4"-32 in my aluminum cylinder head. There was too much work in that cylinder head for me to scrap it, so I decided to go up to the next larger thread size and re-tap it. Steve has sent me what I needed and also samples of his "standard" plug with a 1/4"-32 thread on them to show me the quality of his work. I think the quality is excellent, and Steve's business card is in the picture for anyone who wants to order spark plugs for their project. Thank You Steve Huck!!---Brian Rupnow
(https://imagizer.imageshack.com/img924/9113/jtzDZT.jpg)
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I used one of Steve's 10-40 plugs in my just finished Upshur. Cute little bugger, very well made, and works great.
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And here we are, head rethreaded and new sparkplug installed. Engine build can now resume.
(https://imagizer.imageshack.com/img924/4578/fRxyXU.jpg)
(https://imagizer.imageshack.com/img924/3920/dfvejt.jpg)
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Thrilled to announce that the engine is back together, valves and pushrods are installed, head and head gasket are installed, and flywheels do seem to have "bounce back" when given a flick by hand (which is a sure sign of compression). Valve timing and valve gap (between pushrods and shcs has not been set yet. I don't need the fan housing and fan on there yet. Also still have to make a gasket to fit between intake manifold and cylinder head. Tomorrow---tomorrow---
(https://imagizer.imageshack.com/img922/5029/s8uskL.jpg)
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Brian/Steve, can I ask what sealing method is used on the 5/16" plugs as the hex looks to also be about 5/16 and I'm not sure if i'm seeing a chamfered edge to mate with a chamfer to the hole or not, certainly no washer?
Also Brian what was the thinking on this second head as I see you have a much deeper recess than that shown in post #64 and on your drawing or did I miss it being mentioned?
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Jason--I misread the drawing when I made the con rod and it ended up about 2.5mm too long. Not wanting to make it over again, I just made the head with a 2.5 mm deeper recess.
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Everything is buttoned up and I am just at the point of setting the valve timing with a degree wheel. You can see that I have a pointer attached to the crankshaft, and by loosening the set screws on the small crankshaft gear and loosening the set screws on the intake cam, I am able to move things around until the intake and exhaust valve begin to open at the correct time in the cycle. This particular degree wheel was originally designed for a vertical cylinder engine. It still works for me here, even though the "0" degree marker is at the top of the dial.
(https://imagizer.imageshack.com/img924/1842/Gail40.jpg)
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Brian/Steve, can I ask what sealing method is used on the 5/16" plugs as the hex looks to also be about 5/16 and I'm not sure if i'm seeing a chamfered edge to mate with a chamfer to the hole or not, certainly no washer?
The Diameter is larger than the hex. I'm not sure if a washer will be used. The Plug was machined to within a few thou of Brian's drawing. I'm sure he has a plan.
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Thanks Steve, I've just blown it up to 500% and can make it out now, as you say will have to see how they seal as the round dia does not look much more than that of the thread.
Brian, that deeper head also explains why my question on HMEM about the larger threaded hole cutting into the area where head meets cylinder were unfounded as the head no longer seals against that small raised lip on the end of the cylinder. :)
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The plugs are exactly as I requested. The amount of compression lost around the plug threads is practically unmeasurable.--Certainly not enough to keep the engine from firing.
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Yesterday afternoon I tried everything I can think of to start the engine. Not happening. Valves lash and valve timing is set "by the book" and ignition timing is correct. Tried a fresh can of fuel, made no difference. After about 4 hours messing with things, I thought "Everything is set perfectly but the engine won't fire.--Maybe it's my new cast iron rings." I squirted 30 weight oil down the sparkplug hole, and compression rose a great deal---that must be it---my c.i. rings are no good. So---today I made a new piston and put a Viton ring on it. Changed pistons about half an hour ago---and---it didn't make any difference. Engine refuses to fire with cast iron rings and with Viton ring. Sparkplug from Steve Huck is firing fine when removed from sparkplug hole and laid out on top of the cylinder head. But when cranking it over, not a pop, not a fart----nothing. I haven't seen an engine act like this before. Both intake and exhaust valves are sealing very well. If I choke it with my finger over the carb air intake while cranking it over with my electric drill, it will pull fuel up from the tank, and spit it out the exhaust pipe. But not firing at all. Thinking---thinking---
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Glad - well I'm not really, can sympathise, only a bit mollified - that someone else is having the same sort of problem, in my case it's a sleeve valve engine that refuses to fire. Not that its any consulation Brian, but I have not succeded at all either yet, despite all I know being thrown at it, so can offer no advice that you have not already tried.
But one continues to perserve.
Chris
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I am using a transparent sparkplug boot. I can see the spark jumping from the high tension lead to the tip of the sparkplug while I am cranking the engine. The engine has good compression, and it's not radically different with the viton ring from what it was with the cast iron rings. One thing I really do notice is how much more drag the engine has when running the viton o-ring.--Very curious that it doesn't want to fire.
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Before I take anything apart, or change any settings, there is one more thing I will try. That is to try using automotive gasoline instead of Coleman fuel. I'm not sure why that sometimes works, and it probably has to do with the volatility of automotive gasoline. This gets a bit too scary for me to do on my side-desk in my office. Tomorrow I will move operations out to my main garage, where there is more of a chance to put out any catastrophic unexpected fire disasters.
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Brian, Before you start pulling your engine apart I would check your spark timing again, you know the plug is firing but is it firing at the right time, as you say you have fuel getting to the cylinder I would have thought you should at least get some sort of pop, backfire, or even some gassing from the exhaust.
Just a thought.
Michaelr
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Yesterday was a complete write off, machine wise. Spent half the day designing something for a customer and half the day doing pre-Christmas things. Today however, I got really bold and tried to start the engine with automotive gasoline in the tank. No difference at all!! Engine will not fire. It is definitely sucking gas up to carburetor but not igniting it in the cylinder. Engine has good compression. Even if timing is out of whack, I should be getting some pops and farts while turning engine over with drill, but it's not happening. Can it possibly be the sparkplugs?---surely not. Steve Huck sent me two new sparkplugs and they both fire like crazy when laying out on the cylinder body. It has to be something deeper. I will now pull the cylinder head off and see if something is funky with the head gasket.
(https://imagizer.imageshack.com/img923/1610/ttDDOH.jpg)
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have you tried turning it over in near darkness as that will show if the sparks are taking a short cut from plug lead to cylinder head.
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Okay---Just pulled the head off. This is a view of the inside of the cylinder head. There was nothing funky about the head gasket. There was nothing funky about the position of the sparkplug relative to the valves. The only thing I can see is that the spark from the center electrode to the side of the plug is happening on the side away from the valves. If I put a small brass washer between the sparkplug and the cylinder head, I hope to be able to re-tighten the sparkplug and have it so that the spark jumps to the valve side of the sparkplug. It seems highly improbable that this would cause a "no fire" situation, but when everything else has been checked, we start to seek out the improbable and correct it.
(https://imagizer.imageshack.com/img924/3138/aXrIaU.jpg)
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YES!!!!--That did it. Engine is now finally firing. Turning the sparkplug 180 degrees so that the spark was occurring closest to the valves done the trick.---I'm happy--happy--happy. Next amazing stunt will be getting an extended run and making a video.
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The holes for the head fixings seem much to close to the combustion chamber :headscratch: Will the head gasket actually seal or will the compression leak past? I would plan for at least 2mm sealing surface.
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And since we last spoke---things have went off the rails. I had reached a point in my trouble shooting where I had discovered that the engine WOULD fire if I rotated the sparkplug 180 degrees to bring the spark closer to the valves. And immediately after I discovered that it would fire, I started loosing head gaskets. Multiple fixes were tried, but sadly there was no good way to fix it. Ultimately, I have decided to make a new cylinder and cylinder head. And yes, we're going to try something different. All of my previous i.c. engines have worked just fine using head gaskets made of 0.031" thick general purpose water pump gasket material. Now we're going to go away from conventional head gaskets and try our luck with a Viton o-ring head gasket. The two highlighted areas in this model indicate where the o-ring is going to go. These 1/16" o-rings actually measure 0.070" in cross section. The annular groove will be plunge cut with an 0.094" wide cut-off tool and will be cut 0.018" deep in both the cylinder and the cylinder head. This will give me 0.034" of "squeeze" when the head is bolted to the cylinder. The fact that the groove is 0.094" wide will give the o-ring material somewhere to be displaced into when the head is fully tightened down on the cylinder. A day will make me a new cylinder, and the new cylinder design will leave more clearance between the base flange and the first "cooling fin" (I had a horrible time getting the bolts in that hold the cylinder to the vertical plate). There won't be much visual difference in the new design, except the top ring on the cylinder will be slightly larger in diameter, as will the head. I can probably make a new cylinder head in a day, but with Christmas it will probably be more like two days.
(https://imagizer.imageshack.com/img924/1438/LhjqTN.jpg)
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Could you not have just redone the head as it was originally drawn with the shallow recess. That way like many other engines the seal is on the narrow raised "ring" around the top of the cylinder or liner not the flat area beyond with the risk of pressure escaping up the screw holes as on yours now there is no seal from combustion chamber to these holes.
You don't even need a gasket with the head sealing against the narrow "ring" at least mine run that way, I think Keep it Simple is what they say.
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So, here is the new assembly.--Looks just like the old assembly. The only difference is that the cylinder head and the very top of the cylinder are slightly larger than the previous version.
(https://imagizer.imageshack.com/img922/2544/Gxfwb0.jpg)
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So, here we go. Out with the old cylinder and in with the new cylinder. You will notice that the new cylinder has a much wider "land" at the cylinder head end. This is to allow for the o-ring seal and so that the counterbored holes in the cylinder head don't break out past the edges of the cylinder head. You will also note that I have left much greater space between the bottom cooling fin and the mounting flange to make it easier to get that ring of bolts in place.
(https://imagizer.imageshack.com/img924/337/f8yDRC.jpg)
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The new cylinder is finished and the o-ring groove is cut into it's mating face. I probably would have liked it better if the o-ring groove had ended up concentric with the bore, but when it's all buttoned up, nobody will see that. It won't have any effect on the way the o-ring seals. That ring was machined in there with a 3/32" endmill while the cylinder was held in the chuck mounted on the rotary table. I might have ended up with a truer set-up if the cylinder had been mounted on a four jaw chuck in the lathe, but I'll remember that for next time.
(https://imagizer.imageshack.com/img922/906/40eprV.jpg)
(https://imagizer.imageshack.com/img924/8154/iKFxGl.jpg)
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Okay!!!---Christmas is over. Santa did come. Second son showed up for Christmas dinner and brought his new Ojibway girlfriend. (she is a very nice girl). Everybody else stayed home and "Christmassed" with their families---Too much Covid around for big family get togethers. When I put that o-ring groove in the top of the cylinder, I grabbed the wrong size endmill.---Poop!!! It has been fixed with a steel back-up ring to fill up the extra space, and now the groove is 3/32" wide to accept the 1/16" o-ring.. Work is proceeding on the engine. New cylinder is finished. New cylinder head is 3/4 finished.
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The engine has been reassembled with a new cylinder, a new cylinder head, and a Viton o-ring head gasket. I'm not going to try and start it today, as I've just Loctited the carburetor into the brass adapter and I want it to set up good before I start messing with it. Somebody on one of the forums I post on has recently built a multi cylindered radial engine, and he said that he didn't put any angle on the valve seats, just left them sharp cornered, and that he got great compression with no lapping. This didn't seem reasonable to me, but I thought "If it worked for him, maybe it would work for me."---It doesn't. Tomorrow I will pull the head off and use my magic George Britnell tool to put an angle on the valve seats the way I usually do. I'm getting awfully good at pulling the head of this engine.
(https://imagizer.imageshack.com/img922/458/JFUnmF.jpg)
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Following along here, someday I'll take the leap and try an IC engine, for now am learning by watching...!
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I ran a die all the way up to the hex shape on the sparkplug, which gained me about 0.100" of sparkplug sticking into the combustion chamber. That didn't help---engine still won't fire. Tried advancing the spark timing a little---engine won't fire. tried indexing the plug--engine wouldn't fire. Tried retarding the spark a little----engine won't fire. Got really, really desperate and tried some ether---engine won't fire. Took out piston with cast iron rings and put in a piston with viton o-ring---engine won't fire. Tried holding a spare finger over the carb air horn to choke it while spinning engine with my "starter-drill"---choked it until raw gas was coming out the exhaust.---engine didn't fire. I'm just about out of tricks. If I pull the plug and lay it out on the deck, plug fires like crazy while engine is being cranked. My sparkplug boot is transparent, and I can see fire jumping like crazy from the end of the wire to the top end of the plug when engine is being cranked over. (It wouldn't do that if plug wasn't firing.) Compression isn't real great, but then with these engines I build, the compression generally isn't great until the engine starts and runs for 10 or 15 minutes to seat the valves 100%--then they have crazy compression. Bottom line is, that in all of this head changing and sparkplug changing, the engine has only fired once and that was a result of indexing the sparkplug. It fired once and immediately blew the head gasket. Valve lash is set at "about" 0.010", valves are definitely closed when not up on the cam lobes. The internal shape of the combustion chamber is the same as countless other engines I have made, that ran successfully. I'm totally buffaloed for the moment.
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Are you sure it is firing at the correct TDC (or does this one fire every TDC)?
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Even so you would expect the odd pop as residual fuel gets ignited at some point, one of the reasons I like to hand start as you can feel and hear what is going on when there is no drill whizzing away.
To totally rule out the spark shorting somewhere you could take the head off and check that the plug is still sparking OK when screwed into the head rather than unscrewing it and trying away from the engine.
The other simple thing is make sure your battery if fully charged particularly at this colder time of year so it puts out as big a spark as possible under compression.
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So, here I am at the end of a 9 week build. To achieve this build in that time span required that I worked on some aspect of the engine every day of that 9 weeks. The engine looks good, I am satisfied with that. I am confused as to why the engine won't fire. There is nothing here that is different from all of my other running engines, other than the sparkplug. The sparkplugs are brand new, from a different supplier, and far be it for me to question a brand new sparkplug. There is a possibility that the plug is shorting out internally, but if it was shorting out internally, then it would short out internally when laid out on the block. It doesn't. It gives a bright blue spark just like a good sparkplug should. My "need to machine something" has been satisfied (for now). Now I go into the detective phase of this build, and that is the part I don't really care for. I know I have fuel. I know I have compression. I'm not 100% sure I have spark. Even an engine with screwed up valve or ignition timing will fire when the engine is being turned by an electric drill. It may fire at the wrong time in the cycle, it may just give "pops and farts", but it will fire. You can hear it fire, and you can see smoke, and the cylinder will get warm. You can feel it kicking back against the drill when it fires. I'm undecided where this will take me now, but I will be sure to keep you informed.---Brian
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There is a possibility that the plug is shorting out internally, but if it was shorting out internally, then it would short out internally when laid out on the block. It doesn't. It gives a bright blue spark just like a good sparkplug should.
Not so. the spark will take the easiest route with least resistance. I the open air that is likely to be from electrode to body as it should but once inside the combustion chamber under pressure that may not be the case and the spark could be going elsewhere.
You should just about be able to make up an adaptor 5/16 x 24 external and 1/4 x 40 internal and then try it with another plug, plus first doing the test I suggested with the head off the engine but plug in place
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I think there was some question of the spark plug sealing properly in the head without a gasket? If air is leaking past the threads on the intake stroke, there may never be a combustible mixture in the vicinity of the spark.
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The sparkplug is not leaking around the threads. Someone on one of my forums didn't believe me when I said that the engine did have adequate compression, so they wanted a visual on it. Here it is. This doesn't get me anywhere closer to having the engine run, but it is kind of a fun video.
https://www.youtube.com/watch?v=jJEAny_Toh8
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Why would the spark arc occur anywhere but at the gap? Maybe try to ground the head directly with a ground wire. Just a shot in the dark
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+1 on ground the head! and +1 on Jason's idea to trying with the head off but plug in place. All to do with eliminating the possibles, it leaves you with the probables.
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The engine just ran!!! God loves me after all. When all probable things have been tried, it is time to try the improbable. There was only one thing left to try that didn't involve machining something. I kept getting mixed signals about whether the sparkplug was really sealing against compression leakage or not.----So----Ten minutes ago I backed out the sparkplug, coated the threads with green 638 Loctite, then reinstalled the plug. Waited ten minutes and engine started up and ran like a trooper. I will get a video up tomorrow morning. I am so relieved. :pinkelephant: :pinkelephant: :pinkelephant:
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Woohoo! :pinkelephant:
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Congratulations Brian! :ThumbsUp: :popcorn:
This one has been quite the battle!
So, was it just your compression leaking around the spark plug? Or was there anything with the sparkplug getting shorted out and the green Loctite provided some insulation?
Kim
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All the Loctite did was to prevent compression from leaking around the sparkplug threads. 638 is my "go-to" choice for Loctite. It is an excellent sealant, but releases very easily with a bit of torque. Like I said, all of my engines run---eventually. Some run right away and surprise me. Some require much thought and fiddling with. Out of about 20 engines, I haven't seen this happen before. I keep thinking that if I build enough of these small engines, I will get to the point where I can diagnose whatever is wrong and fix it immediately. The most difficult thing is knowing that everything is adjusted and set properly, and still the engine won't run. Thank you all for your suggestions and your interest.
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Well done, Brian. That one certainly tried your persistence.
Looking forward to the video.
MJM460
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Good to hear it is running and also know that the problem was one I raised as soon as I saw the photo of the new plugs.
Do be carful using 638 as a sealer, it should not release that easily being a retainer not a thread lock/sealer, don't want to strip the thread in the head trying to get a plug out :'( Maybe the heat of the head is weakening it.
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The fuel I used was new fuel. The battery is fully charged. There is nothing wrong with Steve Huck's sparkplugs. they work fine. I had Steve make two "special" plugs for me, and I knew there was very little shoulder on these plugs to snug down against the top of the cylinder. I didn't think they would leak around the plug threads, but I was wrong. We live, we learn.
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So, here we are. The culmination of a two month thrash!!! I had a few problems sorting out a reliable head gasket, but solved that by going to a Viton o-ring head gasket instead of the treated cardboard that I have used on previous i.c. engines. I had major issues getting the engine to fire, but traced that back to leaking threads around the sparkplug. There was nothing wrong with the sparkplug, it was my funky threads in the cylinder head that were causing me grief. Once I got that sorted, the engine ran like a race-horse. These Traxxas carburetors have the touchiest throttle lever in the world. That throttle is intended to be operated by a servo, so is very touchy indeed. That is why during the video my finger doesn't leave the throttle lever--if I take my finger off the throttle the engine tries to run wide open and scares me half to death. I miss-spoke in the video and said the motor has a 1" stroke---that's not correct, it is actually 1 1/4" stroke. I will sell these plans (about 50 sheets) for $25 paid to my Paypal account. Contact me if you want to purchase a set of plans. Thank you for following my build on the forum.---Brian Rupnow
https://www.youtube.com/watch?v=00mC276bYLA
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Wonderful sound to it! Glad you got it sorted. :ThumbsUp:
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Glad you got it fixed Brian, sounds really good, runs very nicely
Chris
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Glad to see your success with this engine - congratulations, you have a fine runner :cheers:
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Tomorrow I'll make up a "Casey Jones" throttle lever and linkage from it to the carburetor. A couple of Belleville washers between the throttle lever and the baseplate will add enough friction to keep the throttle from vibrating out of place.
(https://imagizer.imageshack.com/img922/6739/oeZgnu.jpg)
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Brian,
Glad to see you sorted out the problems and have it running!
Art
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Today, after some minor tweaking and tuning and the addition of a Casey Jones style throttle lever, the engine is running much more sedately. The folks who I generally buy Belleville washers from are temporarily out of stock, so even with the addition of my throttle lever the engine wants to "creep" to a higher rpm.--That gets scary as heck when the engine pulls the throttle wide open. My next trick will be to add the piston with cast iron rings and see how well it runs.---Brian
https://www.youtube.com/watch?v=M47bVIBb6tw
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Brian, another great build! I'm glad you found the issue and that the engine is running so well!
I really like the looks of it!
Mike
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Thanks Mike. I'm really interested in what it will do with the other piston with cast iron rings.---Brian
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Thanks Mike. I'm really interested in what it will do with the other piston with cast iron rings.---Brian
Brian, I'll certainly be interested in your testing of cast iron piston rings vs the Viton o-rings. I've only build 2 I/C engines so far and I've used Viton o-rings on both of them and they've run really well. I do use a much lower 'squeeze' on the o-ring than you seem to though and I wonder if that make a big difference. I've heard the claim that C/I rings are lower friction and work better, but I'm not sure about that. I'm guessing that there's no doubt that they'll last longer, but I do wonder about the friction. I've followed the advise of Bob Nawa and I size the o-ring groove diameter for very minimal squeeze which is definitely not what Parker or National recommend.
Again, great work and I'll be watching your tests!
Mike
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Mike---I've built model engines now for about 13 years, and always used Viton o-rings, because they are so easy and work so well. It's only within the last year that I've gotten serious about cast iron rings. For me that was a huge learning curve and the cost of a heat treating oven and controller. You heard right---Viton rings seal well, but have a much higher "stiction" than cast iron rings. Cast iron rings slide in the cylinder much easier, but for me it was a difficult learning curve. I have two 1" bore engines working very well with cast iron rings, and this will be my first 7/8" bore with cast iron rings.---Brian
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Today I removed the piston with the Viton ring on it and installed the piston with the two cast iron rings. The engine tried it's best to run, but never quite made it. The engine would fire and start, but after I removed the drill/starter the engine would gradually slow down and quit. I thought that perhaps if the flywheels were a bit heavier it would let the engine "carry thru" from one power stroke to the next and help the engine to keep running. I dug around in my "shorts" bin and found a piece of round cast iron that I set up in the lathe and bored it to fit over the drive pulley on the back side of the engine, held in place by a 1/4" set screw. It didn't help. Tomorrow I will investigate why the cast iron rings aren't holding compression properly and see what can do about that.
(https://imagizer.imageshack.com/img922/3042/8HPaXZ.jpg)
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It takes a very small leak to loose compression. My diesel is of similar size to your engine (20cc) and leakage through the 0.2 mm (8 thou) injector nozzle hole when the needle is removed destroys the compression.
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When you can take a heat treated ring and bend it like this, it's a pretty good indicator that you have used the wrong cast iron to make the ring. It will also bend like that before heat treat. It will work as rings---I have two engines operating quite fine using rings made from this material. Today I am going to use the two remaining cast iron rings that were made in that batch to see if they will run my engine. I am also going to take steps to buy the correct cast iron for ring making. My local supplier doesn't know squat about the cast iron he is selling.
(https://imagizer.imageshack.com/img923/7861/2P1ayO.jpg)
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Brian, what is the proper type to use?
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Chris--Doing some research on that right now. right now I'm seeing "unalloyed grey cast iron and "meehanite grade 17" and "centrifugally cast iron". I have to call around and see delivery and pricing.---Brian
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GR17 is what we tend to use over here but expect it has a different code number stateside. Yours look more like ductile iron as mentioned earlier.
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A little help here please--from North America--I have determined that the material I am using for piston rings is the wrong kind. I buy it from a local steel supply shop and they don't really seem to know much about the cast iron which they are selling me. I am sure they are selling me ductile iron, because when piston rings are made from it, they bend easily. Not break!!! Even after heat treat they bend. I have just about worn out the internet this morning searching for correct ring material. My research tells me that cast iron material for rings should be A--Pearlitic grey cast iron with a low modulus of elasticity. B--centrifugally cast, not ductile C--Durabar cast grey iron D ---fine grained grey cast iron E--pulltruded .
If you live in the U.K. you should use class 17 Mehanite (I don't live in the U.K.)
I need a foot of this material in 1" diameter (well actually it's a bit more than 1" because it is cast) but I am having a terrible time figuring where to buy this stuff in Canada. It's heavy, so shipping charges will be high. If I buy from USA and can get a foot of the proper material I can probably eat the shipping cost. What I really need to know is where the heck I can buy this material (preferably in Canada but USA will do).---and what exactly is it that it's called when I go to order it?---Brian Rupnow
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McMaster Carr has this, which I am pretty sure is what you want.
https://www.mcmaster.com/8909K78/
McMaster Tech support are very helpful (I have found) so you can always call them and confirm (they can look up material cert and spec), but this is specifically gray cast iron, and is identified as brittle. MCMaster also sell ductile cast ironm which is not what you want of course.
The only other sources I have are wholesalers. Online metals and metals depot don't seem to stock cast iron any more.
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Another source is Hobby Metals Kits. Call & talk to Bernie. He’ll help find what you need.
https://hobbymetalkits.com/
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Most excellent! I was not aware of them. Probably the better source - McMaster is very convenient and very fast, but you pay extra for that.
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Hard to find stuff. As mentioned McMaster Carr has a good selection of Gray Cast Iron (A247) and Ductile Iron (A536). MSC Industrial has some, Gray Iron and Ductile Iron. They give "Manufacturers Part #" as GR12 and DR12 which may or may not be a material spec. On Line Metals does have cast iron, but only drop shipped in 6' lengths.
If you find a great source let us know. Thanks.
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On Line Metals does have cast iron, but only drop shipped in 6' lengths.
So they do - you just have to use their search. They don't have it on their material headings. Bad assumption made on my part.
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I talked to Bernie at https://hobbymetalkits.com/ and this man seems to know what he's talking about. I ordered a foot of the 1" diameter cast iron which meets all of the specs for making rings. The material itself is only about $14, USA but the shipping from Wisconsin is going to be horrendous. This will last me for the rest of my life making rings. I'm sure that there are companies in Ontario that sell exactly the same material, but I haven't been able to find them or contact them.
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Propforward, McMaster is normally my go to source & has been for over 30 years. Their customer service is old school & shipping is more than fair.
Brian, I’m glad Bernie was able to help find what you need. He knows his stuff.
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Propforward, McMaster is normally my go to source & has been for over 30 years. Their customer service is old school & shipping is more than fair.
Oh yes, a great company to deal with - plus what they sell is only good quality stuff.
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Today is a "machining free" day. Hooray!!! My little machine shop doesn't have a spare inch of room anywhere in it. I wanted to have some dedicated cabinets for small bits and bobs that were important, and didn't have room for anymore cabinets inside my shop. I didn't want them too far away either. A quick survey of the wall space I had available outside of the machine shop showed that I had a 12" wide area of free wall space between my shop door and the wall adjacent to it. A quick search thru the Princess Auto website showed almost exactly what I wanted 11" wide for $14. I bought two of them and mounted them in the wall space, and spent a good part of this morning moving things and making labels so I would know what was in the cabinets. As much as I like machining things, it's quite nice to have a rather laid back day where I do something else that needed doing.
(https://imagizer.imageshack.com/img922/1286/etT0hg.jpg)
(https://imagizer.imageshack.com/img924/3491/EA5x1u.jpg)
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Great spot for the storage, room for more above/below if needed. Now, will you let us know when you spend an hour looking for something you relocated to the new units but forgot that you did? I've done that many times after rearranging...!
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Now, will you let us know when you spend an hour looking for something you relocated to the new units but forgot that you did? I've done that many times after rearranging...!
Ain't that the way it always goes :facepalm2:
Though at least you remembered to write what's inside from the beginning :ThumbsUp:
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And now---I have a strange story to tell (but it has a happy ending). Couple of days ago I had the engine setting on my side desk, chugging away happily, and I was congratulating myself on what a clever fellow I was to build an engine like that. And then----it quit!!!
Well Poop!!--Must be out of gas. Opened my fancy blue gas tank, and it had lots of fuel. Okay, if it isn't fuel. it has to be spark. I pulled the sparkplug out and laid it on the cylinder head and cranked the engine. Lots of spark!! Well sir--What do I do now? The automotive gasoline in the tank had been changed out for Coleman fuel, because Coleman fuel doesn't stink when it's being burned. Maybe the engine was seizing up, but I've never really had that happen. I grabbed the flywheel and gave it a couple of spins, and it turned freely, so determined that the engine hadn't seized. Maybe the set screws in my ignition cam had slipped and the engine had "jumped time". Checked those screws out and they were tight. Maybe the set screws in one of my timing gears had slipped and the valve timing had gone screwball. Checked those set screws and they were still tight. Maybe the Viton piston ring had failed and I had lost compression--but no, engine still has terrific compression when turned over by hand. Maybe something wrong with the carburetor--but no, those carbs don't have any small moving parts that can fail or vibrate out of place. How strange!! My engine won't run, and I can't diagnose what is wrong. Had some serious thoughts about making another head with a vertical sparkplug in it (A 1/4-32 sparkplug would fit beside the valve cages)--I laid it out on my 3D program and it would work, but Damn, there's a lot of work in making a cylinder head. I looked at my files from ten or eleven years ago when I built my own sparkplug for the Kerzel engine, but I really didn't want to do that. Went to bed, disgusted with small engines in general. Today I thought, "If the engine ran okay (which it did) and the engine then stopped without any clanks or bangs or obvious signs of distress (which it did), then what can possibly have changed? I pulled the sparkplug out and looked at it under my lighted magnifier, and seen that the spark gap was only about .005". Enough to give a bright spark when laying out on the cylinder head but not enough to light the charge of fuel under compression. Fetched out my trusty jacknife and opened the gap to about .025" and reinstalled the plug. Engine started right up and ran like a race horse. Relief, relief!!! I have no idea what closed the spark gap up while in the engine. Maybe a piece of dirt from when I was trying the piston with the cast iron rings. Maybe it was the bad engine fairy.--I don't know, but man, I'm glad I got it sorted out without having to remake anything.
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Today I'm just piddling around putting in time. I had to look thru all my various bins of junk to find something, and what I actually found was a plethora of pistons. I see two with Viton rings, one with cast iron rings, one with no rings, and one that had been lapped into a cylinder without even any ring grooves. I have no idea why I saved these, nor what was wrong with them. I guess it's part of the "Never throw anything out" syndrome that I have. I'll keep them. Most of them have a thick enough wall that I could perhaps use them in an engine with a 31/32" bore some day.
(https://imagizer.imageshack.com/img922/5788/ZhdewW.jpg)
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Today I went digging thru my stock of brass, and found a length of 1.25" diameter brass. This will be big enough to make a 7/8" external lap from. I may make a new piston from cast iron, and lap it to be a very precision fit into the cylinder bore. This will definitely help with the compression issues. I will still make new cast iron rings for the piston, when my length of cast iron specifically for making rings from arrives here from Wisconsin. Right now my aluminum piston has about 0.002" diametral clearance in the cylinder. I should be able to bring that down to 0.0002" diametral clearance with the lap and a cast iron piston.
(https://imagizer.imageshack.com/img923/2876/oY9RVn.jpg)
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So---this is the external lap for a 7/8" piston. It is drilled and reamed to 0.875" thru. I've stuck a 7/8" piston into one end of it for "show and tell". In actual use, there are no rings installed on the piston. The sawcut lets it open to greater than 0.875", and lets it close to less than 0.0875". The single shcs in the center provides the clamping force to close it. In use, the piston is mounted on an arbor of lesser diameter that fits into the counterbore in the piston and cross-pinned thru the piston pin bore, and is held in the lathe chuck. The brass lap is coated with 600 grit lapping paste on the inside and held in your hand, and is worked back and forth on the rotating piston at about 70 rpm. You start with a slightly oversize piston and work it with the lap until it will just fit (somewhat tightly) into the cylinder. then everything is disassembled and brushed with dishsoap and an old toothbrush to clean away any remaining lapping paste. You have to be ready to quickly let go of the lap if it "grabs". Don't want your arm wound up in the lathe!!! If it does "grab", you let it go, shut off the lathe, and then walk everything out to your bench press, press the piston out, then back into your lathe to finish it up.
(https://imagizer.imageshack.com/img923/6031/kl7IeN.jpg)
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When I made this external lap, I reamed it with a 0.875" reamer. After I put in the saw cut, it closed up a bit due to internal stresses in the brass and reads about 0.870". Next step will be to coat a piece of 7/8" round cold rolled in my lathe, add some lapping compound to it, and lap to an even 0.875" inside diameter. At that point I will tighten the cross bolt and close the sawcut up a bit more, and again lap it on the 7/8" diameter rod until I reach a point where the i.d. is 0.880" inside diameter when the clamp screw is backed off. This way I can make my piston .002" to 0.003" oversize, then using my external lap and lapping paste bring the piston down to an exact 0.875" diameter for a snug fit inside the cylinder.
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Don't make the pistons too close in diameter. An aluminium piston in a cast iron/steel bore needs some space for expansion. I used a cast iron piston in a cast iron bore for my diesel, around 40 Bar compression, to reduce the expansion problem. My horizontal engine initially would start and run without piston rings (ali. piston in ci liner) but would then sieze as it warmed up. I had to take a few 0.01mm off the piston and add ci piston rings to get it where it is today.
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Okay--Back to the external lap. When I made this lap, I drilled and reamed it with a 7/8" reamer, and it was a perfect 0.875" i.d. Then after I put the sawcut in it, it closed up to something less than 7/8". I thought about this for a while and decided to set it back up in my mill and run the reamer thru it again. That worked, but the lap still wanted to close up a bit. I mounted a piece of 7/8" cold rolled steel in the lathe and turned a 1 degree taper on it. Then I coated the cold rolled with 600 grit aluminum oxide paste and with the lathe turning about 70 rpm I worked the lap back and forth slowly over the tapered end by hand until it slid freely over the 7/8" cold rolled steel shaft. This was done without the clamp screw in place. After it slid freely over the shaft, I took it out to my bandsaw and ran the blade thru the existing cut again. Then back into the shop to run it over the shaft a few more times to knock down any internal burrs from the sawcut. Cold rolled steel comes in about half a thou undersize, so I know that at this point my lap is 0.8745" inside diameter. Next step will be to gradually tighten the clamp bolt and continue running the lap over the cold rolled with the 600 grit paste. When the clamp bolt has been tightened up enough to close the sawcut, then I know that when I release the clamp bolt the lap will spring open to something greater than 0.875". Not sure how much greater, but then it will be at a point where I can begin lapping my cast iron piston from "oversize" to a "perfect fit" in the cylinder.
(https://imagizer.imageshack.com/img922/4383/ReQLGo.jpg)
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Good that you found out why Brian :ThumbsUp:
I think I would not close the clamp all the way for the last pass, as that will not give you total ajustability / possible compensation for gritsize ....
Per
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The external lap is finished. When the clamp bolt is loose, the lap measures about 0.880" inside. When the clamp bolt is tightened, it measures 0.870" inside. I will machine my cast iron piston to 0.880" diameter, and then with the lap I will lap it down to a point where it is a snug fit into the cast iron cylinder.
(https://imagizer.imageshack.com/img923/9538/0PCwr9.jpg)
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A bit of explanation now, on what I've been doing. I was very surprised when the engine didn't want to run with the new cast iron rings I made for it. And then, I figured out that I had used the wrong kind of iron to make the rings from. This was surprising, because the rings were made from the same stick of iron that made two or three sets of rings that did work in the engines they were made for. The shop I buy my iron from didn't seem to know if this was ductile iron or the other type of iron. I found out after the fact by seeing how easily the rings bend. My current piston is aluminum and is 0.873" diameter, riding in a cast iron cylinder. When the engine wouldn't run, I made a second aluminum piston the same diameter with a viton ring for a reality check, and the engine ran fine with a viton ring. I then ordered a stick of the correct type of iron for making cast iron rings from Wisconsin, and it showed up here yesterday. I have a choice now--I can make new rings and put them on the existing aluminum piston----or---I can make a new cast iron piston which is a closer fit in the cylinder and put new cast iron rings on it. This is why I made the brass external lap, to lap the new cast iron piston so it would be a closer fit in the cylinder.-not an air tight seal, but much closer to it than the aluminum piston was. I'm not worried about thermal expansion, because the piston and cylinder will be the same material so if the piston grows a bit from heat, the cylinder will grow as well so it shouldn't seize on the piston. At the same time I was waiting for my new iron, I started a new thread about the possibility of using my Toolpost Grinder from Little Machine shop to grind the piston to the exact outside diameter instead of lapping it. I got so many varied answers to that question that I decided not to do it. So, armed with the knowledge I have collected, I will now make a new lapped cast iron piston from the old stick of cast iron from my local supplier and new cast iron rings from the new correct material from Wisconsin.
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Meet the new piston--Looks an awful lot like the old piston. However, it's made of cast iron, not aluminum, and it's 0.003" larger in diameter than the old piston (the one with rings on it). I had hoped for 0.005" larger in diameter, but you work with what you get. If it works better than the old piston, we're golden. If it doesn't, I had the material anyways and it's 2 1/2 hors out of my life that I can spare. Sometimes I'd swear that my lathe is bewitched.--It never takes off less than I wanted it to, but frequently takes off more!! Tomorrow I'll make some new rings and heat treat them.
(https://imagizer.imageshack.com/img923/2335/XniATk.jpg)
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Things didn't go the way I had it planned. My plan was to turn the new piston to about 0.880" diameter, and then use my external lap to bring it down to around 0.877" for a snug fit into the cylinder. On the last pass, which was intended to bring the piston down to 0.880"', the machine Gods laughed and when I measured the piston with my micrometer it was 0.876". Didn't leave enough on the diameter to even bother using the lap. I think it's probably time to pull the topslide off my lathe and tighten up the nut which the cross-feed screw engages with, and then tighten up all the gibs. The new piston is good enough to use, but I would have been happier if things had worked out the way I planned.
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What are you measuring the bore with ? a few posts up it was "a perfect 0.875" ?
Brian, did you read my post else where about TCGT inserts or sharp HSS, you will be able to sneak up on the size far easier with them as a standard TCMT insert being blunter tends to ride over the surface when a small cut is applied until you sudden lt find it cuts but will be several times more than the feed.
Two small grub screws in the back of the cross slide nut to adjust backlash but that is not likely to be the cause of your overcutting.
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Jason--thank you for posting. I do read your suggestions.--Brian
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Okay--I'm going to run with what I got. The new cast iron piston is marginally smaller than I had intended, but it is still within the recommended 0.002" smaller in diameter than the cylinder bore. The piston rings will be cut from my new piece of iron from Wisconsin, and the o.d. will be turned to match the cylinder bore of 0.878". The o.d. of my piston is 0.876" dia. and I cut the ring grooves to be .046" wide x 0.045" deep. So---the rings will be cut to 0.045" thick, and 0.876-(.042+.042)=.792" i.d. That will give 0.001" total side clearance when the ring is setting in the .046" wide groove, and 0.792" i.d. will give 0.003" radial clearance between the inside of the ring and the bottom of the groove on the piston.
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When I part these rings off from the parent stock, there are a few things to consider. First, I know the ring thickness I want. My target figure is 0.045". Second thing is that I must know the thickness of my parting off tool, which in this case is 0.039". Third thing to know is that I want to make the rings about about .004 to .005" thicker than my target figure, because each side has to be lapped against a cast iron surface plate. Fourth thing to keep in mind is that every time I part off a ring, I must sand and deburr the end of the parent metal before I cut the next ring. That means that I only have one face on each ring that must be lapped. So, in my case, it meant that every time I parted off a ring, I had to move the carriage 0.088" before I parted off the next ring. Then I go thru all the parted off rings and check to see which side is the "bad side" and needs to be lapped. When all of the rings are brought down to "finished thickness" they have to be split. Then the ends are filed so that when the ring is in the cylinder there is a 0.004" gap between the ends. Then they go into my oven, mounted on a special fixture that spreads the ends apart to a "target dimension" for a four hour heat treatment to "set" the gap .
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So, as of this morning I have parted off 13 cast iron rings from my new stick of iron from Wisconsin. The o.d. is equal to the bore of my cylinder. The i.d. is calculated so that when installed there will be 0.003" radial gap between the inside of the ring and the bottom of the groove in the piston. The rings have been deburred and had the edges broke on one side---they were deburred and sanded on the exposed side before they were individually parted off. They are all "over thickness " by .004 to .005 and that will be addressed when I dress the side which is not deburred on a cast iron surface plate with a sheet of 600 grit aluminum oxide paper on it. They have all been examined under a magnifying light and the "bad side" marked with a black marker.
(https://imagizer.imageshack.com/img924/7599/FWxKhG.jpg)
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The rings have been fully deburred and taken down to the correct thickness. They have been split using a very sharp cold chisel, then the ends have been filed so that when inserted into my cast iron cylinder they have a 0.004" gap. Here they are mounted on my heat treat fixture and spread over a 0.131" drill and ready to go into my heat treat oven for 4 hours at 1100 degrees. The extra rings which didn't fit on the fixture will be appropriately identified and kept for a future build.
(https://imagizer.imageshack.com/img923/8799/VyWNGk.jpg)
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This is a picture of the rings on the heat treat fixture after 4 hours at 1100 degrees. The fixture and the rings look like crispy critters, but some scrubbing with a brass bristle brush and liquid dish soap cleans them up to a much better look.
(https://imagizer.imageshack.com/img924/863/dJ3qXF.jpg)
(https://imagizer.imageshack.com/img924/4672/wfcDM0.jpg)
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This is the rings after removal from the heat treat fixture. They will still require a bit of clean up, but they are essentially finished. Note that each ring has now taken a "set" to the 0.131" diameter of the drill between the ends of the rings. When compressed into the cylinder, that gap narrows down t 0.004", and that spring force is what keeps the ring tight against the cylinder sides.
(https://imagizer.imageshack.com/img922/782/0Jbn48.jpg)
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:ThumbsUp:
Nice work Brian!
John
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After more trials and tribulations than you want to hear about, this is my 7/8" horizontal engine running with cast iron rings. This was much more of a struggle than I anticipated, but the fault was mostly that the grub screws holding the bottom timing gear had slipped enough that the engine was out of "correct valve timing". To me, this is wonderful. This is the first 7/8" bore engine that I have installed cast iron rings in. In this video my engine is running on Coleman fuel.---Brian
https://www.youtube.com/watch?v=WifDJa8tBZ4
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Today I'm going to call this engine "finished". It is doing everything I set out to accomplish, and is running with cast iron rings. There is a bit of a write up with the video. Thank you all for watching the build and for the helpful hints and suggestions. ---Brian
https://www.youtube.com/watch?v=2j1gQ2O3dDs
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Lots of work, but a wonderful result!!
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Great final result Brian :cheers:
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Very nice, Brian! :ThumbsUp:
Kim
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Brian,
Good to see you have a runner!
Art
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This video, made 17-Feb 2022 shows my most recently designed and built single cylinder horizontal engine running with a home made sparkplug. I had issues with the cylinder head, mainly because I messed up the 1/4"-32 threads for a standard sparkplug, so had to redrill and tap to a 5/16" fine thread. I had Steve Huck make me a "special" sparkplug with a 5/16" fine thread, but could never get it to work consistently. Then I made a sparkplug, but my design was a bit fishy, with a 0.060" spark gap. It would spark to get the engine running, but as soon as it warmed up, the spark would jump across the outside of the sparkplug to ground and the engine would stall. Finally, a redesign of the sparkplug with an 0.025" spark gap worked successfully, and the fact that the sparkplug is 3/8" longer than the first home made sparkplug keeps it from arcing to ground on the outside of the sparkplug. I am happy, the engine runs fine, and now I can put this project to bed. If you want to buy a complete set of plans to build this engine, contact me at brianrupnow@gmail.com---Brian https://www.youtube.com/watch?v=gTnwDFAI-MU