Author Topic: Pottymill horizontal engine build  (Read 79580 times)

Offline wagnmkr

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Re: Pottymill horizontal engine build
« Reply #60 on: February 05, 2015, 11:33:05 AM »
This is looking quite good so far.

Well Done

Tom
I was cut out to be rich ... but ... I was sewn up all wrong!

Offline b.lindsey

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Re: Pottymill horizontal engine build
« Reply #61 on: February 05, 2015, 12:17:21 PM »
Well done Todd. Are you going to try to lessen the clearance between the slide bars?

Bill

Offline Hans

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Re: Pottymill horizontal engine build
« Reply #62 on: February 05, 2015, 02:27:34 PM »
Todd,

It is taking shape quite nicely.

As a beginner, I very much appreciate you taking the time to document and share the process. I learn more from studying these build threads than any other resource and the time it takes to upload photos along with the narrative is no small task.

Often the most helpful parts are the mis-steps followed by your description and implementation of a solution. Your willingness to include these in the story is appreciated.

Hans

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #63 on: February 05, 2015, 08:12:16 PM »
Bill,

For sure I'll tighten up the slides a little when I remake the valve guide.  The problem is that the slides are 1/4" and so is the stock I'm using.  The little spacers are larger, but the valve guide is 1/4" also.  I'd like to avoid using the shim.  So that leaves a couple possibilities.  I could make the valve guide from thicker stock, which is my current plan, or I could slightly skim off the slides so they have some clearance.  This is only 5-8 thousandths so that's probably reasonable.  If I had used an 8-32 thread on the cross slide I'd have much more material for such an adjustment.  BTW, I have thought about running those 10-32 threads down to 8-32.  Since they are the same TPI, I'm guessing that will work, but I've never done that before.  I'd have to re-make the slides if I did this so it isn't top on my list.

Hans,

Thanks for the feedback!  I've been wondering how much detail to include as I'm sure there are yawns from many on the forum due to the great volume of pictures.  But I found this level to be VERY useful in my early days, which weren't that long ago.  I recall re-watching Jose Rodriguez videos after I had spent a little time in the shop, and when I did this I noticed many many things that I hadn't seen on the first pass.  Mainly how to deal with mistakes, as you say, but also how to setup things.  What side of the mill do you work on, what angle do you put the compound and/or cutter at, etc.  I still don't have answers for all that, but I found it helped seeing what others did.  I figure even if what I was looking at wasn't a perfect setup, it was still a reasonable setup since it worked for "that guy." :)  The thing I need to remember to do once in a while is back up and get a wider view shot so you can see setups.

BTW, if you follow any of my pictures over to photobucket you'll find I have many more pictures that I'm not showing here.  Feel free to do that, especially if you come back to this thread some day and build this particular engine.  I've been taking pictures with my Nexus 5 mobile phone.  It does an excellent job getting focus tight in spaces, and it's handy right there in my pocket.  I sometimes need to wipe the lens on my shirt, but that's about it.  No tripods, no extra gear.

Todd

Offline b.lindsey

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Re: Pottymill horizontal engine build
« Reply #64 on: February 06, 2015, 12:46:45 AM »
Hi Todd, guess I misunderstood, I thought you meant there was too much clearance between the slides and the slide bars. It sounds like you are wanting more clearance now rather than less. Still watching and following along with interest.

Bill

Offline rodw

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Re: Pottymill horizontal engine build
« Reply #65 on: February 06, 2015, 04:08:37 AM »
Todd, this is an awesome build (and Instruction manual) I've been following along for a while. I don't have a lot of spare time right now and I've been getting withdrawal symptoms as I have not been in my shed for weeks. I'm very keen to attempt this build. I think a novice like me (with one simple engine under his belt) could do this by following this howto thread. I've been looking round for some metric plans so it fits the bill perfectly.
RodW
Brisbane, Australia

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #66 on: February 06, 2015, 09:46:17 PM »
Bill,

Your original understanding was correct.  I must've worded my response poorly.  It does have too much clearance right now.  Well, really I'm sure it would be fine, but I'd like to tighten it up a bit.  I hope to get some time to tune it up yet today.

The real trouble is that I'm trying to make the slides and the valve guide from the same stock.  The valve guide acts as a spacer, so either I need to make it thicker (e.g. using a shim or thicker stock), or I need to skim the slides to make them a little thinner.  Maybe I should consider skimming a few thousandths even though that 10-32 screw hole is mighty close to the edges on the slides.

I could keep the shim and skim the new valve guide (I'm re-making that, regardless) thinner.  That possibility just occurred to me now.

Todd

Offline sbwhart

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Re: Pottymill horizontal engine build
« Reply #67 on: February 07, 2015, 07:45:49 AM »
Bill,

Your original understanding was correct.  I must've worded my response poorly.  It does have too much clearance right now.  Well, really I'm sure it would be fine, but I'd like to tighten it up a bit.  I hope to get some time to tune it up yet today.

The real trouble is that I'm trying to make the slides and the valve guide from the same stock.  The valve guide acts as a spacer, so either I need to make it thicker (e.g. using a shim or thicker stock), or I need to skim the slides to make them a little thinner.  Maybe I should consider skimming a few thousandths even though that 10-32 screw hole is mighty close to the edges on the slides.

I could keep the shim and skim the new valve guide (I'm re-making that, regardless) thinner.  That possibility just occurred to me now.

Todd

Hi Todd:- I made the slides and the guide out of the same size bar also, I simply shimmed the guide using a piece of kitchen baking foil folded over a few times to get a reasonable thickness. As an aside there have been a few of these engines made that run well without the valve guide, so you have that option also.

Keep up the good work

Stew
A little bit of clearance never got in the way

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #68 on: February 07, 2015, 04:16:17 PM »
Finishing the Cross Head Slide Assembly

I decided I'd try skimming down the slides rather than shim up the spacers.  Here's how that went.

First I had to re-make the valve guide.  It acts as a spacer (the small hole) and a guide for the valve rod (the large hole).  Sorry about the blurry pic...looks like the back of the vise got in focus.  But you get the idea.  The previous part was a little too short and the large hole was just about cutting through the end.  The valve rod is 0.125 inch, so I drilled with a #29 (0.136) for some extra clearance.  Previously I reamed to 0.126 and there was no way it was going to slide.


Next I skimmed the spacers all to 0.250 inch.  In the vise you'll see the old valve guide on the right, the new one on the left, and four spacers in the middle.  I only needed three spacers, but I made four for testing and in case one jumped ship (which always happens to me).  My working theory was that I'd slowly run the mill down until I could hear it barely skimming the old guide on the right, then I'd skim across.  I actually made 3 passes going a little closer each time.  Note the folded paper was required.  I tried without and the first round spacer started spinning!  There is a single parallel holding them up on the back side.


Now that my spacers are a matched set, any irregularity must be either the brass pillars, or the base plate, or the parallelism of the cylinder to the base.  Nice to rule things out.  In the end I skimmed off an extra thousandth.


I tried bolting down the guides, but of course they pinched the slides so it couldn't move.  Next was time to skim a few thousandths off the slides.  I took 4 thousandths off the top of the slides and then did a test fit.


Here's the test fit.  I managed to turn on my brain and think about using feeler gauges to see where I was at.  3 thousandths at the bottom, and snug on the top.   The cylinder is riding slightly high because it measured consistently down the length.  At least that gave me some confidence the piston rod wasn't going uphill.  This means I need to skim more off the top of the slides, and also means I need to keep track of up vs. down when I install them.


While I was at it, I had a look at how the valve guide was doing.  It's riding a little high as can sort-of be seen in this photo.  Rather than try to elongate the hole, I decided to drill it larger until it fit all around.  Worse case I'll need to make that part a third time and shift the hole down a bit.  If that's the case, I can do the math based on the enlarged hole size that worked.  So I may as well drill it out.


Here we are, two drill sizes larger.  This was a #27 (0.144).  I'll leave it like this for now.  If it runs sloppy, I'll need to account for needing to expand the radius by 10 thousandths.  That is, shift the center down 10 thousandths.  All in all, I don't think this is so bad considering I didn't adjust the cylinder base.  Remember it was undersized by 5 thousands to start (16mm vs 0.625 inch), so half the problem came from that.  The valve chest might shift a bit if I unbolt it as well.  So  I'm leaving it for now.


Next is finally time to make those thrust washers.  I measured with calipers and found they needed to be roughly 0.125 inch.   Since they are so small, I decided to make a pair and see how they fit using the feeler gauge again.  I'll remake them to fit correctly.  So face and drill some 3/8 inch brass rod (~10mm).  I used a D drill initially but had to change to 0.250 to get a slip fit.




Here it is.  Not bad :)


And here they are on the cross head.  Brass looks nice in there.


With feelers I found one side needs to be 0.008 thicker and the other closer to 0.018.  So I made new ones.  Here's a new one on the far side that's now 0.130.  The slide is aligned with the guide rail, but I need to screw down the rails to get an accurate reading.  But it's easy to see what's going on with it partially disassembled.  Note the close side washer is pretty far off yet.


Here the close side washer is also replaced.  I ended up at about 0.140 for this one.  Things are still a bit adjustable as the guides can slip around a little when I loosen the bolts.


And here it is from a nice side angle.  I'm still thinking about some bling to go around the exhaust holes.  Recall the valve chest got drilled upside down and my air inlet is on the bottom.  That worked out ok.


Now I think I'll turn to the crankshaft and bearings.  I can mount the bearing stands on the base and finally wipe off that ugly blue :).  The flywheel remains as well as the eccentric mechanism to operate the value.

I'm thinking about what to do for a wood base for the engine, but I'll wait until I have the crank and flywheel done. The flywheel will hang low so I'll need to account for that.

Todd

Offline smfr

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Re: Pottymill horizontal engine build
« Reply #69 on: February 07, 2015, 04:45:22 PM »
Nice write-up, Todd. I feel we often "sweep under the rug" the tricky fitting and finishing part of engine building here, where you have to shim a few thous here, and take off a thou or two over there, and it's nice to see it described in detail. It does take a certain mindset to figure out all the alignment issues.

Simon

Offline b.lindsey

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Re: Pottymill horizontal engine build
« Reply #70 on: February 07, 2015, 09:30:37 PM »
Glad you got it all sorted Todd and it looks great too!!

Bill

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #71 on: February 11, 2015, 08:40:48 PM »
Here's another installment in the pottymill horizontal engine building saga.  I have loads of pictures this time, so butter up the popcorn and enjoy the slide show.  Be thankful you aren't about to view one of my vacations :)

The Crankshaft

The crankshaft is built up as an assembly of several components.  I looked at it for a bit and, perhaps in a moment of foolishness, I decided to go out of my comfort zone and build it out of a solid hunk of cold rolled (bright) steel.   I happened to have a bit of the stuff that was nearly perfect in size.  I thought my little Harbor Freight 7x12 lathe was up to the job.  Those intermittent cuts give me the heebie-jeebies so this effort might rid me of such worries.

I started by inking it out so I could keep my bearings as I turn it.  Later on I etched in some big X's over the areas that would be removed.


The CRS was a bit wide so I used my bandsaw to chop off the excess.  It gave me a bit for another project.  I need to build up my metal supply so I have pieces closer in size when I do this stuff, but the cutting went good and didn't waste much metal.


Next I drilled for centers.   This bar is 0.5 inch thick and it's sitting on a 0.5 inch center that's laying flat so I used a little paper to let it snug up in the vise.


I placed it between centers...but now was at a little bit of a loss how to drive it.  I could have created some kind of dog that would clamp to this surface.  In fact, a bunch will get cut away, so I could have drilled/tapped and installed a stud of some kind, too.  Instead I decided I could chuck it in the 4-jaw and use the tailstock as a support.    Note that my bandsaw cut fairly straight along the top edge.


In order to chuck it, I need both sides flat and parallel.  So I cleaned them up over on the mill.


I indicated and adjusted, indicated and adjusted, ... and got nowhere after quite a bit of time fiddling around.


The problem was that when I'd run it, I'd notice the tailstock wiggling.  It was clearly out of alignment, but I was damned to see how.  I checked it along the length and it was perfect.   Later I realized the root cause of the problem was that the center holes on the end were ever so slightly off the center line of the bar.  I skimmed over the crank web to round the ends, but by the time I was done I decided I'd need a different approach.




So I turned a bigger stubby temporary center so I could embed the crankshaft bar into the chuck in a manner similar to the connecting rod a few weeks earlier.   The alternative would have been to make a general purpose dog to clamp onto the bar.   Either way I'd end up with a little "tool" for the next job.  So here goes...





Now I'm able to turn on centers.  I know the little stubby center isn't perfect since I had to move it into the chuck, but it should be pretty darn close.  Here I'm using the parting tool to start opening up the web.   It wasn't going so well.  The bar really pounded on my parting tool.  I needed a better way to clear out the metal.


Well, duh.  Time to drill out a bunch.  I was a little sloppy, but it took a pile of metal out fast.




Now back to the lathe.  It was going ok, but I got to the point where I needed to extend the parting tool further.  This wasn't going to work.  The tool was just too wiggly being extended so far and this being such a nasty intermittent cut.


I thought a new cutter might be in order.  For giggles, I placed a 5/16 inch HSS blank in my toolholder.  It came with a pre-made 10 degree relief angle on the end.  I honed it a little, but didn't grind any other relief angles.  I wanted to see if it might work, first.  It actually worked crazy-good.  Go figure.  It's really a big fat parting tool.  I had to go slow, but it worked.  And remember much of the material was drilled out already.  The end had a bit of an angle, but that was ok for this rough shaping.




To remove the taper, I went back to my parting tool for some very light cuts.  It was now that I carefully turned it down to size.  I did some test fits with the connecting rod and repeated until it was just right.



And there it is...half way done.


Clearly I need to collect more ways to drive work on centers as this was the main problem today.  Once I got that figured out, and figured out what cutter to use, my little lathe handled the intermittent cuts for this "deep" (14mm) web just fine.

Stay tuned for the next part where this turns into something that actually looks like a crankshaft.

Todd

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #72 on: February 12, 2015, 04:54:26 PM »
The Crankshaft, continued.

Today's installment is mainly a slide show.  I took lots of pretty pictures so you can see the block of metal transform into a crankshaft.

Fortunately I have a metal cutting bandsaw which made quick work of chopping off the extra material.  It's already starting to look like a crankshaft even though it's a bit square-ish.  Note that I scribed X's so I'd have half-a-chance of chopping off the right bits.





Now the square shaft is small enough for my lathe dogs to fit without trouble.  At some point I took out the lathe dog's pin because the socket head screw worked good enough.


I cleaned up the outside edges of the webs first.  This is a big intermittent cut and I thought it best to get most of it done while the shaft was still very thick.


Next I started turning down the shaft.  I switched to a tough carbide cutter.   It worked good, but at some point it started interfering with the live center.  While it fit, I was able to cut about 0.050 inch per pass.  That was quite a bit for an intermittent cut on this little lathe.  It took a few passes to get to the point in the picture.


I switched to an HSS cutter and continued making heavy cuts.  I think I was doing 0.030 inch per pass here, so the finish was a bit rough.  I was spraying with WD40 and it smoked a bit.  No fires, though :)




I got to within 0.030 of final diameter and switched sides.  Back to the carbide cutter.  I was using the autofeed geared for the finest passes I could get.  That's 1/256 inch per turn on this lathe.




Now I've switched back to HSS.



And just a little cleaning on the web is needed...





And now I switched sides to do a "final" pass.  This isn't really final, though.  I'm leaving it with 10 thousandths extra.  When I make the bearings I'll adjust the crankshaft to fit the bearings rather than the other way around.  I think that will be easier for me.



And here it is.  The finish could be a bit better, but I'll fix that with lighter passes to fit the bearings.


It fits the engine nicely too.  Remember I did take time to get the connecting rod fitting correctly.


It's still amazing to me that a part like that can pop out of a bar of steel.  And really it wasn't difficult.  I'm happy I took this route for the part.

Next up, the bearings and bearing stands to hold this crankshaft.

Todd

Offline b.lindsey

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Re: Pottymill horizontal engine build
« Reply #73 on: February 12, 2015, 06:52:32 PM »
Very well done Todd and an excellent write up for those wishing to make a similar crankshaft!! You are getting closer to a runner by the day now :)

Bill

Offline Roger B

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Re: Pottymill horizontal engine build
« Reply #74 on: February 12, 2015, 07:06:00 PM »
Good work on the crankshaft  :praise2:  :praise2: The headstock centre on the Minilathes does seem to stick out a long way  ::) Like you I found it best to saw/drill as much away as possible before starting to turn. When I was turning the crank shaft for my horizontal engine I screwed a block between the webs to take the thrust from the centres. The holes will then be used to fix the balance weights.
Best regards

Roger

 

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