Vertical Cylinder I.C. Rupnow engine

[Brian Rupnow]

And the last few pieces for now.

[Art K]

Brian,
You know what they say, It's 5:00 somewhere.
Art

[Brian Rupnow]

I have been asked about how I fit the piston to the cylinder. I haven't really got into piston/cylinder fits yet, but this is how I do it--the cylinder is finish reamed (or bored, I have a 1" reamer) to 1.000" diameter. After initial machining, a brake cylinder 3 stone hone powered by a variable speed drill is ran through it back and forth thru the bore dry at about 150 rpm, and only for about a dozen times to knock off any high spots.  Do NOT let the hone spring out either end of the cylinder while you are doing this. A piece of 1" diameter aluminum about 6" long is 'polished' with 220 grit carborundum paper until it just fits into the end of the cylinder. (this will mean that the 1" aluminum will be at about 0.998" diameter.) The very end of the aluminum is chucked in the lathe, and coated with a slurry of 600 grit carborundum paste and oil, and with the lathe NOT RUNNING the cylinder is held in your hand and slowly pushed and rotated onto the aluminum until it will fit right over the aluminum and have about 1" to 1 1/2" of the aluminum sticking out the other end of it. This is a slow procedure and not a lot of force should be used. It will feel tight and gritty at first--it is supposed to--You are polishing the bore to take it to a very smooth finish. Once the cylinder can be moved from one end of the aluminum to the other without "grabbing", remove it from the round aluminum completely and start the lathe at a low 50 to 60 rpm. Add a little more slurry to the aluminum surface. Very carefully slide the cylinder over the revolving aluminum and slide it back and forth about 20 times, making sure to not slide it so far that the aluminum disappears into the bore. Be ready, if it grabs, to let go very quickly and shut down the lathe, then work it off by hand. This is very dangerous and scary as Hell, but it's the way to do it. Turn the piston outer diameter down in very small increments until it just starts into the cylinder bore but doesn't slide in. I have made up a handle somewhat like a long connecting rod with a T handle on the end of it. I put the handle on the piston with a short piece of material to act as a wrist-pin, put the cylinder into the lathe 3 jaw, and coat the bore with a bit more slurry. Using the T handle, with the lathe OFF, work the piston back and forth thru the bore until it moves freely. Once this is done, wash the inside of the cylinder and the outside of the piston with soap and water and scrub with a toothbrush and wipe with laquer thinners, to be sure to remove any remaining carborundum paste. Now--You are set up to use a Viton o-ring for your piston ring. The procedure is the same for the piston regardless of whether it is cast iron or aluminum. This will be a relatively slow revving engine, so we are not worried about the mass of the piston, and as I said in an earlier post, cast iron has it's own inherent lubricating properties because of the graphite which is part of its metallurgical make up.---Also---the crankshaft web has a pretty massive counterweight built into it, so I like the mass of an iron piston to avoid over-counterbalancing the engine, as might happen with a light aluminum piston.------------Lubrication--Well, the crankshaft runs in sealed ball bearings, so needs no lubrication. Both ends of the con-rod are going to be running sintered bronze Oilite bushings, so a squirt from an oilcan before running will be quite good enough. The camshaft doesn't rotate. It is stationary, and the exhaust cam is bolted to the face of the cam gear, which rotates on an Oilite bushing. And--I always run about a 50:1 mix of synthetic 2 cycle oil with my fuel to lubricate the Viton ring and the piston/cylinder interface.

[Brian Rupnow]

I just received my Tecumseh ignition points #30547A for use on this engine. I can probably figure out a mounting system on my own, but I would really like to see someones installation of these points either in an engine they have built or in an original engine. These points don't rub on the ignition cam. They are remotely mounted, and a pushrod opens them. I can only assume that the other end of the pushrod rides on a cam, but I would really like to see some pictures of the points, pushrod, and cam mounted. I did a Google image search and although I found a thousand pictures of the points, I didn't find any of the points "in place". Can someone help please.----Brian

[Jasonb]

Don't know where you are searching brian but there are plenty of pics of them inplace, try third image down here

The slotted end is rigidly fixed to ground. The other end need s to be rigid so it provides the spring to keep follower on the cam but must still be insulated

[Tennessee Whiskey]

Brian, I think you may be thinking of an Onan points system. I'm on my phone now and hard to link, but, I'm seeing the push rod setup in some Onan point ignition picture searches however all Tehcumsa ones show a cam

Cletus

[Brian Rupnow]

The 1/8" i.d. x 1/4: o.d. roller bearing which goes on the end of the pushrod is no longer carried at Busybee Tools. I have found an alternate supplier of the same size bearing made by INA part number #R144-2Z. They are $5.40 each, minimum quantity of 5 on each order.  I will buy a package, and when anybody gets far enough with the engine to need one, I will mail one to them.

[Brian Rupnow]

Guys, somewhere along the way, I got lead down the garden path. It was my understanding that the Tecumseh points were operated by a pushrod which rode on the cam. I was wrong. I'm busy on some "real work" for a couple of days, but will sort the points out next week. thanks for your help.---Brian

[Jasonb]

It would be easy enough to trim that black plastic arm and have it ride on the end of a push rod. Then again why not just make a nice neat set of points rather than try and cram on an automotive part. This is one I made for the current project engine the bronze block rides on the cam which is on the end of the crankshaft, alloy housing clamps around end of crankcase and timing can be advanced & retarded by loosening clamping screw and rotating the assembly.

[Brian Rupnow]

Jason--You do some very nifty things!!! ---Brian

[Art K]

Brian,
I was looking up maintenance manuals, the points fit 3-10hp but couldn't find what vintage. I don't see why you couldn't use some sort of pushrod to run them remotely. In a guide block one end running off the cam lobe the other pushing the rubbing block. A bit complex but would allow them to be mounted elsewhere.
Art

[Brian Rupnow]

http://i68.photobucket.com/albums/i16/itshim1/IMG_1413_zpscal2m8r4.jpg---This was a picture put up by a gentleman on another forum I post on, showing the points operated by a pushrod set-up that he made.---Very clever!!!

[Brian Rupnow]

Too soon we get old---Too late we get smart----These are the points I was thinking about that are operated by a pushrod. Look at the way they mount. Instead of a "flange/face" mount like the Chrysler and the Tecumseh, these ones mount at 90 degrees, which is what I actually wanted. I will call and get a price on them tomorrow.
http://thumbs2.picclick.com/d/l400/pict/272031848569_/John-Deere-Original-Equipment-Point-HE1601183.jpg

[Brian Rupnow]

A little of the rationale behind using a roller on the end of the pushrod. If the cam has curved sides on it, then the lifter can be flat on the bottom and not need a roller. However, cams with curves sides are relatively complicated to make. Now, if you used a flat sided cam with a flat bottomed lifter, then every time the cam revolved, the flat side of the cam would "slap" the flat bottomed lifter, and make it bounce. That would cause problems. However, if the cam is made with flat sides and used with a cam follower bearing instead of a flat bottom lifter, then the "roller" will ride up and down, following the contour of the flat sided cam closely without the "slap and bounce" that you get with a flat sided cam and a flat bottomed lifter.----Brian

[cfellows]

Brian, don't know if you've considered this or not, but you could mount the cam which operates the points on the crankshaft instead of the camshaft.  The contact on every crankshaft revolution wouldn't hurt anything and would open up some options about where to mount the points.  For example you could mount the points underneath the engine or in a hollow engine base.

Chuck