Author Topic: Pottymill horizontal engine build  (Read 59515 times)

Offline tinglett

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Pottymill horizontal engine build
« on: December 28, 2014, 03:36:23 PM »
Here's another start for a beginner build.  This will be my fourth engine and my first non-oscillator so I'm pretty excited.  I'll post more detail than most on this board need to see in the hopes that it helps other beginners, but keep in mind I'm no expert and hopefully others will chime in with alternative ways of doing things.

Update:  The prints are in metric for this engine, but I built it in imperial.  I posted notes here http://www.modelenginemaker.com/index.php/topic,4919.msg94957.html#msg94957 for those who want to do the same.

This is a horizontal mill engine designed by Stewart Hart who kindly sent updated plans to me a couple months ago.  He designed it as a beginner engine.  The prints I am using are Binder1V3.pdf for future reference.  Stew created a thread in Plans & Drawings for this almost two years ago (http://www.modelenginemaker.com/index.php?topic=1388.0) but beware that anything you find over there is a bit out of date.   Here is a rendering from that thread:



Again, thanks to Stew, and I hope I don't embarrass him too much with my stumbling through this :).  BTW, I have both a lathe and mill (7x12 Harbor Freight lathe and LMS 3990 HiTorque X2 mini mill) as well as a bunch of new tools I'd like to try out on this engine.  That means some of my setups will be overkill, but I need to learn how to use all this stuff sometime.  And finally, I'd better mention that Stew's prints are metric and my hobby shop is setup for imperial.  I can measure metric easy enough with digital calipers, but my tooling is imperial (mainly drill bits and taps) and my stock also starts as imperial.  I decided that in general I'll stick to metric, but I'll need to do some adaptation along the way.  Hopefully I won't mess up anything critical doing this.

I decided to start with the cylinder.  It's easy enough and I know I can turn a piston to fit the cylinder much easier than the other way around.  The cylinder is a generic design for use with multiple engines.  Here it what it looks like, but for this engine it will have a second flat.  The first flat as shown is for mounting the slide valve, and the extra flat at 90 degrees is for a mounting block for attaching it to the base.



I first faced a length of 1 3/8" aluminum rod.  This is nearly exactly 35mm which will be the size of the cylinder covers.  I could have used 1 1/4" which is just a bit under 32mm, but I didn't have any in the shop...so I decided to turn the rod to exactly 32mm.



Here I am starting to drill the 16mm opening, which is slightly over 5/8".  I had original intended to flip the part end-for-end and cut the cylinder covers before doing this.  At my skill level I've learned it is very hard to do this and keep the hole perfectly centered, but with the cylinder this wouldn't matter.  However, the blank turned out to be a bit short, so I decided to drill it in place and use another part to make the cylinder covers.  You'll see that in the next post.


My largest drill and reamer are 1/2" so I had to bore this one.  This was a new operation for me as I just got a new AXA toolpost for my lathe.  Yes, it's monster-big on this thing, but so far it's working very well.  The boring tools I had are too small so I had to spend a little time to make them fit.  It seemed to work well.  My 4-jaw is pretty big so it all matches :).  NOTE:  why am I using a 4-jaw chuck?  It was already on the lathe and I was too lazy to change it...and besides I needed practice centering.


I turned it around using soda can to protect it.  I indicated it again, even though this was really unnecessary since I'm only parting it off.  Extra practice.


I faced it for good measure.  This brought the length down to 44mm (well, actually 43.87mm, but that was close enough for this).


Next it went into the mill to make the flat.


And finally I rotated it to make the other flat.


Stew's instructions say the cylinder can be made without a mill.  I was tempted to try making it from square stock just to see if I could get the math right.  The plan shows the flat area as 29.86mm vs the overall diameter of 32mm.  I think I could have chosen an edge and moved it out 13.86mm, rather than actually centered at 16mm, and turned it down to 32mm to get the same effect.

Next I need to drill the intake/exhaust passages and make the covers I mentioned earlier.  I think I'll wait with the bolt pattern for the slide valve and drill the parts together.  I don't have a DRO so it would be difficult for me to do them individually and expect them to line up.  I plan to do the same for the cylinder covers, too.

Todd
« Last Edit: May 23, 2015, 07:31:06 PM by tinglett »

Online b.lindsey

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Re: Pottymill horizontal engine build
« Reply #1 on: December 28, 2014, 03:42:41 PM »
Nice start and excellent pictures Todd...I'll be looking forward to following along on your build of this one.

Bill

Edit: Todd, I see Binder1 in the thread you noted but not a V3 version.
« Last Edit: December 28, 2014, 04:33:04 PM by b.lindsey »

Offline Johnmcc69

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Re: Pottymill horizontal engine build
« Reply #2 on: December 28, 2014, 05:19:04 PM »
A very nice start....Stew has made some really great drawings & designs & offers them free. My hat's off to him for offering all his talent & all the other members here who have done so.

 You're doing a fine job Todd, nice pix & you have obviously put some time into thinking through your setups. You'll have this built with no problems.

 Keep the updates coming, it's going to be a beautiful engine.  :)

 John

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #3 on: December 28, 2014, 08:58:21 PM »
Bill,

I got Binder1V3.pdf direct from Stew.  I'm sure he's made updates, though I haven't studied both sets close enough to see what changed.  For a general overview, Binder1.pdf over in that thread is good enough to see what you are getting into, but I believe Stew is attempting to keep it updated.

Todd

Offline sbwhart

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Re: Pottymill horizontal engine build
« Reply #4 on: December 28, 2014, 09:37:18 PM »
Hi Chaps

Thanks for your interest in my little engine, there have been quite a few made, the design is quite robust to the odd mistake and inaccuracy.

Nice start on the cylinder Todd  :ThumbsUp: for some reason I always like to make the cylinder of engine first.

Binder1v3 is the up to date version of the drawing, as I said there have been quite a few engines made to these drawing so they should be mistake free but if any of you guys spot any errors just let me know and I'll correct them and up date the version.

Cheers

Stew
A little bit of clearance never got in the way

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #5 on: December 28, 2014, 09:40:17 PM »
Another update.  I've been getting good time in the shop! :)

Next, I decided to make the intake/exhaust ports.  I figure it would be easy to mess this up and I'd rather get it over before going to all the work of attaching matching covers and slide valve.

From the diagram in my previous post you can see these are routed from the center of a side on the flat to the outer edge where they sneak into the cylinder.  I decided to start with the two ports on the side which go half way through the cylinder wall.  I calculated this at about 0.100"

To locate these ports I used the edge finder on the movable jaw of the vise.  I knew the cylinder is 32mm diameter and I didn't want to calculate offsets from the flat.


I dialed the mill into the centerline at 16mm (0.630"), locked the Y, and then located in to drill the ports.  Note that I have a DI setup to measure depth.  My mill has a micro depth control, but it's not trustworthy.  I use the microadjust to move the head, and use the DI to know how far I've really gone.


These ports are 4mm.  I decided that a #21 bit was the closest match and made a note in my notebook so I'd make them all that way.



Now I flipped the cylinder on edge.  The flat that was against the fixed jaw is still there, and my Y is locked, so everything should line up.  Here I'm finding the edge again.


Then I dialed in to the center of the cylinder wall.  If you are *real* observant, you might see that I started drilling and then moved back to the left slightly.  The hole was uncomfortably close to the inside wall so I brought it back 0.020".  Here is where I realized there is either a discrepancy in the prints, or I made a bad assumption.  The second page of the plans shows the flat reduces the diameter from 32mm to 29.5mm, but I failed to notice the detail of the cylinder shows the flat containing these ports has a diameter of 29.86mm.  That would have given me a bit extra working room.  I think the plans intended the two flats to be different and I made them the same.


Here I'm drilling to a depth of (44-12)/2 = 16mm ~ 0.630".  That's a lot of spins of my DI to count!  This is a 3mm hole and I used a #31 drill bit.


And here is victory.  It's good when the drill bit shows up where it is supposed to be :)


The final bit of this port is to open it up on the edge into the cylinder.  I decided to do this with a tiny 1/8" end mill in my chuck.  This was a BAD IDEA because I was reminded (again!) that chucks don't hold end mills that well.  The chuck started slipping and made a tiny mess of it, but it worked out well enough.  I need a better way to hold these tiny (< 1/4") end mills.



Then I flipped it end for end and repeated the operations on the other end.  That other flat remains against the fixed jaw so everything stays lined up.


This time I went *much* more carefully with the 1/8" end mill and got a nice result.  This is 2mm deep which I calculated to about 0.080"


Everything didn't go perfect, but so far so good!

Todd

Online b.lindsey

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Re: Pottymill horizontal engine build
« Reply #6 on: December 28, 2014, 10:16:51 PM »
More nice progress Todd...looking good.

Bill

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #7 on: December 29, 2014, 02:47:39 AM »
And yet more progress.  Thankfully, I'm getting more time in the shop than in front of the computer :)

Next I made the cylinder covers.   Here's the plan:



For both I chose to create the inset that fits the cylinder first, for a snug fit, and then do the rest.  That turned out to be a not-so-great idea, but I got through it anyway.  My working theory was that when I'd turn the part around and chuck it, some imperfections from chucking it would be hidden from view.  The problem is that 1.5mm isn't much to chuck.  I had to be very careful.

Recall I didn't have enough material when I did the cylinder (poor math on my part), so I had to hack off another length of 1 3/8" (35mm) aluminum rod.  Here you can see my spiffy new Enco bandsaw.  Well, maybe spiffy isn't the word for it...the instructions were the worst I'd ever seen and it was out of adjustment as bad as you can possibly imagine, but I got it running.  A nice Christmas present and saved me from getting a workout from the hacksaw (if that's a good thing...).


I faced it and skimmed it very lightly.  It came out at about 34.6mm.


I turned it down close to matching the cylinder.  I tried a couple different cutters, but none would produce a nice crisp shoulder.


So I cheated and used my parting tool.   It did a nice job cleaning it up.


I measured until I got real close, then I tested every few thousandths.  It will be held on with screws, but I wanted a reasonably snug fit.  It came out pretty good.


I'm making the front cover.  At this point I decided there is no way I can grip it well enough by the 1.5mm, so I used my parting tool to turn it down.  Is there a better cutter for doing this?  I have a wider pre-made carbide tool, but it chatters up a storm.



I added chamfers per the plan...


And then parted it off...


I made the rear cover the same way.  Here I am adding the chamfers just ahead of parting it off.


Now, the fun part.  Chucking 1.5mm wasn't easy.  I needed to switch back to my tiny 3" 3-jaw chuck.  My 4-jaw had a bigger chamfer on the jaw tips that simply wouldn't grip something that small.  Here I am carefully facing the rear cover with a few very light skimming cuts.  It held ok.



The front cover was more difficult.  Here I am finishing up, but I needed to make several passes to shorten the nub to spec, and I got too aggressive.  Fortunately it fell away rather than jamming and tearing to pieces.  It only got banged up on the nub which I was facing down anyway.  A few more passes and all evidence was gone.


Next I needed to drill for the piston rod.  This raised the question, what size piston rod should I use?  The plan calls for 4mm, but I don't have any of that, and it would certainly be crazy to try to turn such a thing.  I could go with 5/32 (0.156" / 3.97mm) or 3/16 (0.188" / 4.76mm).  I decided to go with 3/16 for a couple of reasons.  Looking ahead, I saw that the piston rod was to be threaded on both ends.  The plan calls for M3 on the piston end, and M4 on the crosshead end.  I'm sure both could be the same, but I decided I would stick to the spirit of it and go with 6-32 and 8-32.  The major diameter of #8 is 0.1640 which is a bit too big for 5/32.  The other reason was that I had 3/16 on hand! :).   So I cut a length of 3/16 stainless rod to have on hand for test fits, and got out a 3/16 drill bit.  I used a starter bit (not shown) and then drilled it through.


The rod fit nice and smooth.  Maybe I should have drilled undersized and reamed it, but too late for that now.  I'm a little more worried about it being ever-so-slightly off center, though, since I had to take it out of the chuck.  Maybe there was no way to avoid that, even if I turned the nub side first.


Next I needed to drill and tap for a piston rod guide.  This is marked as M8.   I decided to go with 5/16-24 which is 7.94mm.  This called for an I drill bit.  You metric guys must be laughing right now.  Depth was 6mm which I rounded to 1/4" by eyeballing the tailstock depth markings.


Tapping was quick work in aluminum


Next was time to make the piston rod guide that threads into that hole I just tapped.  It's made of hex brass and here is the plan for it.



I chucked some 3/8" hex brass (9.53mm), turned it and threaded it for 5/16-24 threads to match the front cover.  Not much to say here, so enjoy the slide show :)







And here's the piston so far.


It'll mount horizontally, of course, but for the moment I'm not drilling for the screws just yet.  I'd like to make and test the piston with the piston rod to make sure the front cover fits well enough.  If it doesn't I'll remake it without worrying about how to line up the holes.  Hopefully that will get done tomorrow, and I'll clean up the piston rod guide a bit, too.

Todd

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #8 on: December 29, 2014, 02:56:33 AM »
By the way, I thought I should mention that I've been finding this chart to be very useful for metric/imperial conversions:

http://www.smithbearing.com/pdf/ENG-FractionalChart.pdf

Rather than get out a calculator, I can eyeball for the metric or imperial number I am trying to find.   And it works better than a calculator because if I look up 4mm I see that is 0.1575 for which there is no imperial drill bit.  However, it is quick to see the slightly larger #21 and smaller #22 glancing at this chart.

The only error I've spotted is that it lists 13/16 for 3/16ths -- an obvious typo.  The only thing lacking from the imperial side of things is another column indicating screw sizes.  I have a second chart for that.

Todd

Offline arnoldb

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Re: Pottymill horizontal engine build
« Reply #9 on: December 29, 2014, 06:03:24 PM »
Good going Todd - you're moving right along with this one  :praise2:

From a "Metric" guy looking in from the other side of the imperial/metric divide: There's nothing wrong at all about how you're going about your measurements, and definitely no laughing.  It's really great to see someone just get on with things and using the best/closest equivalents  :ThumbsUp:

As far as using the parting tool the way you did, I see nothing wrong with that.  From my point of view, there's no fixed "rules" in model engineering, other than keeping things as safe as possible. If a tool and method works in that framework, it's a good way to get the job done.

The cutter in the drill chuck (or lathe chuck from my own experience  ;) )...  Yes, it will "walk out" if pushing the cuts a bit hard.  Unlike the shanks of drill bits which are usually not hardened, both the milling cutter's shank and the chuck jaws are hardened.  This results in a poor grip.  If at all possible, save up a bit, and buy some collets and a collet chuck (or make the collets and/or chuck yourself - it's good machining exercise).  Even el-cheapo collets work better than the drill chuck  :ThumbsUp:

Kind regards, Arnold
Building an engine takes Patience, Planning, Preparation and Machining.
Procrastination is nearly the same, but it precludes machining.
Thus, an engine will only be built once the procrastination stops and the machining begins!

Offline Roger B

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Re: Pottymill horizontal engine build
« Reply #10 on: December 29, 2014, 06:32:01 PM »
Good start on the engine  :ThumbsUp:  :ThumbsUp: As Arnold says, I you feel it's safe and it works that's a solution to the problem  :) No one ever has all the tools and fixtures to do everything the "correct" way  :headscratch:
Best regards

Roger

Online b.lindsey

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Re: Pottymill horizontal engine build
« Reply #11 on: December 29, 2014, 06:54:11 PM »
Dizzying progress there Todd  :insane:  but I a thoroughly enjoying it!!

Bill

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #12 on: December 30, 2014, 04:27:25 AM »
I got lots more progress today after a root canal.  I bet that's the first use of that opening sentence here on MEM :).  Yeah, a root canal sucks, but it's amazing how much better it feels when it is all done.

Making the piston and piston rod

The piston in this engine has graphite packing, which is unlike the other engines I have made previously.  Those engines had carefully fit pistons with no such seal.  I decided I would fit it well anyway and use the graphite packing simply for a better seal.  Since I know nothing about this, I figured that if the packing doesn't do any good, the piston will be in good shape.

I started with the piston rod.  The plan called for this to be threaded M3 on the piston end and M4 on the other end.  Yesterday I declared they could just as well be the same, but today I noticed a little detail in the plan.  On the piston end the piston rod sits in a shallow hole before it threads.  I suppose that makes the joint stronger, and it does require it be a smaller thread so the rod has a bit of a shoulder.   Since I am working imperial, I decided 6-32 would work nicely for the piston and, and 8-32 for the other end.   Nothing complicated but here is the 6-32 end.




And here is the result of the 8-32 end which is much longer for an adjustment nut.


Now it was time for the piston since I have the rod to thread into it.  The piston is 16mm which is a bit larger than 5/16".  I indicated a length of 3/4" brass using my little indicator holder I made a few months ago (thread over here:  http://www.modelenginemaker.com/index.php?topic=3936.0).


I turned it until I got a good fit with the cylinder.



I cut a practice groove with my parting tool.  This groove is where I will need to part off the brass anyway and here I am testing fit of the graphite.  Stew's drawing showed this groove as 2mm wide, but I suppose it's all dependent on the packing used.  I picked up some packing and it seemed to fit pretty well in a groove this wide (2nd photo).



The packing seemed to be rather deep in my test, so I decided my final depth would be a bit lighter.  I believe it was 0.080".  I eyeballed the center of the piston and cut this groove.  From the photo it appears I leaned to the left a little, but it won't matter.


Next I drilled and tapped for 6-32 going a bit extra deep since I was going to part it off anyway.



And finally I drilled a recess hole for fitting the piston rod.  This was 5/16" to match the rod.


Here's a test fit.  Looking good.


And then I parted it off.  My AXA tool post along with tuning my lathe has made this *much* easier than it was 6 months ago.  The tuning provided most of the help, but the mass of the toolpost doesn't hurt (ok, I'm trying to justify the purchase :)).


And here's the piston with rod.


I noticed the piston was a little sloppy, so I chucked the piston rod and lightly faced the piston.  Yeah, nobody will see it, but I knew it looked yucky.   All fixed now.


Finally I did a little polishing to get a nice fit with the cylinder.  One end of the cylinder was a bit tighter than the other -- evidence of poor boring I suppose.  I used the fine metal grinding compound to work through that, then finished off with simichrome.


Bolting on the front cover

I took the cylinder, front cylinder cover, and piston over to the mill.  The piston served as a nice means to center the mill without indicators.


The cover has a simple 4-bolt pattern that's a square.  The cylinder is already square to my vice since it has a flat, so all I needed to do was move the table to a corner of the square.  The plan called for the pattern in a 24mm diameter.  That's a 12mm radius, but since I'm going diagonal to a corner I needed to divide by sqrt(2).  I thought about setting up my RT, but decided the practice I would get wouldn't be worth the effort.


I drilled and tapped for 4-40 bolts I got from microfasteners a while back.


They looked nice indeed.  When I worked on the rear cylinder cover I changed the procedure a bit for the better.  Here I was installing the nice little bolts, but later I realized I should be using SHCS since it's much less fussy and takes much less room to install those temporarily in the tight space within my mill.  I wanted to bolt it down so it doesn't move for the remaining holes.


Since this post is long enough already, I'll skip ahead to the last hole.  I don't have DRO, but they came out real close to perfect, but not quite good enough.  I marked the first hole on the back side of the cover with a scratch so I could align it properly for the best fit as I disassembled and reassembled the cylinder.


Next I drilled out the top cover holes.  I set the Z stop on the mill and did them all by rotating each hole to this position.  For the rear cover I changed this procedure, too.


Bolting on the rear cover

As I mentioned earlier, I tried a slightly different procedure for the rear cover.  I thought I'd document it for anyone else making this engine.  I think it worked slightly better.  I started by centering the cylinder on the back side.  Note that I used the front cover and piston assembly for this.  Why not? :)


I'll show this starting with the third hole.  Each was the same.  I simply held the cover with my hand for the first hole, and the later holes were held by bolts in the earlier holes.  Note that I'm using temporary socket head cap screws here.  Much easier to tighten them in the cramped space.   Here I have already made a starter hole and I'm about to drill to depth.  My bolts are 0.375" so I'm drilling to 0.450" and using a DI in the back to measure my progress.


Next I installed a larger drill for a clearance hole for the cover.  Here I am setting the Z depth stop on my mill.  On the last hole I realized the shim wasn't necessary.  Just let the bit settle in the hole and it will make a nice chamfer for starting the tap.  After setting the stop, I'd place the cover on and let the drill settle into the hole.  It worked well, although I had to remove the cover for each hole.  But with SHCS's that wasn't difficult.


After drilling the cover, I'd chuck the tap and make the threads with the mill powered off.  This was a bit tricky for 4-40 (i.e. tiny) threads in aluminum.  I needed a light touch to make sure I didn't strip them out.


Adding the Graphite Packing

The last step for the cylinder was adding the graphite packing.  I have no real experience with this.   Here I jammed it in.  Pretty messy and it won't fit the cylinder of course.


I took it over to a hard surface, my vice, and pressed it in.  Looking better.


I could actually press it into the cylinder.  Here the back cylinder cover is removed for this.  It shaved off some excess :).


I dusted off the excess and scraped other obvious bits off with a razor.  Now it was looking good, and fit pretty good too.  I had to use a bit of simichrome on the piston rod (not shown) but other than that, it didn't require more tuning.  With the covers on it almost makes a chuff chuff when I slide it back and forth.  Feeling pretty good about it.


Here are some shots of the final cylinder.  It needs a little cleanup and polish of course, and also needs the slide valve which I'll make next.




Thanks for looking in...

Todd

Offline sbwhart

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Re: Pottymill horizontal engine build
« Reply #13 on: December 30, 2014, 05:59:19 AM »
Hi Todd

From your pictures it looks like you've over packed the piston with the graphite, you don't need to pack it solid just enough fill the groove it will swell a little and hold oil, these little engines don't produce a lot of spare power to overcome any tightness so its better to keep things on the slack side. Instead of graphite you could pack the piston with PTFE plumbing tape just twist it into a rope and wrap it into the groove.

The same goes for the piston rod and valve stem glands, for these first pack the gland and tighten up the stuffing nut to consolidate the packing then slacken it off a touch for running

Air/steam engines don't need the same close fitting pistons the same as a Petrol engine.

Hope this helps

Stew

A little bit of clearance never got in the way

Offline vcutajar

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Re: Pottymill horizontal engine build
« Reply #14 on: December 30, 2014, 12:48:15 PM »
I had that exact same problem like you when I used the graphite yarn in my Corliss piston. Messy process.  Like you it was also my first time using using the yarn.  I tend to learn these things by trial and error, hopefully not many errors.

Most probably your engine would also work without the packing.

Vince