Author Topic: Pottymill horizontal engine build  (Read 62417 times)

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #30 on: January 05, 2015, 02:41:23 AM »
In reference to a fix for my dilemma from the previous post, I created an elbow that would allow the air fitting to work on the underside of the valve chest.




Not bad, but what should I do with those ugly exhaust ports?  Two small flanges?

Todd

Offline wagnmkr

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Re: Pottymill horizontal engine build
« Reply #31 on: January 05, 2015, 12:09:28 PM »
Looking good so far ... a couple of minor problems, but everyone has them.

For the exhaust you could create two short pieces of brass pipe that are a tight push fit into the exhaust holes on the one end, and have those two merge into one, either going vertical or horizontal. Like a set of headers for a car.

I am starting on Stew's vertical, which has the same cylinder arrangement and that is what I am going to do.

Cheers

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

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #32 on: January 05, 2015, 01:58:07 PM »
Thanks Tom...

I had forgotten about the other cylinder arrangements.  I should be careful not to call the holes "ugly" because they are certainly visible in those configs.  It's just that the brass looks so much more pimped :).  I'll experiment, but really I can put this off for a long time.  It will work fine without doing anything.

I am thinking about redoing the piston rod.  I wasn't too worried about the looks as the cross slide is a distraction from it, but it does bind a little and I don't need that.  If I sand it down it's going to have a sloppier fit.  I think now's the time to take care of this before I move on.

Todd

Offline sbwhart

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Re: Pottymill horizontal engine build
« Reply #33 on: January 05, 2015, 06:10:17 PM »
Hi Todd

It doesn't matter which way round you have the holes, leave things as they are.

You are making a really nice job.

Stew
A little bit of clearance never got in the way

Offline b.lindsey

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Re: Pottymill horizontal engine build
« Reply #34 on: January 05, 2015, 06:37:45 PM »
I think your solution is just fine Todd, and as Stew said, your are doing a great job with the build. Great pictures too BTW!!

Bill

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #35 on: January 08, 2015, 04:10:37 PM »
Not much progress with "real" work starting again, but I did spend some quality time cleaning up and tuning the cylinder assembly.   I'm going to leave it like this with air intake underneath.  Maybe I'll add some jazz to the exhaust, but not now.   Simple is good, too.



I polished out the roughness in the piston rod (not shown) and hope it didn't make too sloppy a fit.  If it did, I'll need to rework the rod.  The valve chest was indeed a bit over length and that is fixed now as well.  The whole thing is a little stiff, but I'm sure it will loosen up when I work it.

I already started working on bits for the cross head assembly.  Updates coming soon.

Todd

Offline b.lindsey

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Re: Pottymill horizontal engine build
« Reply #36 on: January 08, 2015, 04:29:35 PM »
That polished up nicely Todd. Looking forward to more as you have time. No fun having to go back to work after the holidays is it :)

Bill

Offline wagnmkr

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Re: Pottymill horizontal engine build
« Reply #37 on: January 08, 2015, 10:42:19 PM »
Yes indeed, that is looking good.

Cheers

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

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #38 on: January 12, 2015, 11:49:38 PM »
It's time to get back to documenting my work.  I accomplished a few things over the weekend.

The Cross Head

For the beginning of the cross head assembly, I made the cross head itself and a cross head pin that will mate with the connecting rod.  There are also slide bars and washers that will slide within slide bars and pillars that hold the slide bars.  I decided I should make those together so they fit well together.  So today it's the cross head and pin.  Here's the plan from Stew:



As usual I'll do the cross head and then turn the pin to match it.

I started with some 1/2" CRS bar stock which matches the 12.7mm dimension exactly.  I could have used 3/8"x1/2" as that matches the plan exactly, but this is what I had in my supply.  I faced it, turned the shoulder, and drilled and tapped for 8-32 which is how I threaded my piston rod.  I'm learning that when I make a choice like 8-32 as my substitute for M4 threads, I need to look forward in the print and write it down where it impacts other parts.  In this case I had written 8-32 for this part.





I chopped the part off the bar stock with my bandsaw and left a little extra.  Since the bar stock wasn't 3/8" thick, I had to mill off top and bottom as shown here.  I'm using my DI to measure the amount, which isn't a critical dimension.  Even if it was critical, I know I'm going to do some filing so I could simply use care to leave it oversize.


Next I rounded over the front edges with a file.  No filing buttons here.  I filed by eye and made a bevel first, which is easy to see if it is even width or not, and when I was satisfied, I did the final bit of rounding over.  This was quick work.


Next I located and drilled the hole for the crank pin.  I went with a D bit size, which is 0.246"


I rotated the part 90 degrees in the vise (you can barely see the D-size hole I previously drilled) and then I started drilling out waste between the arms of this little part.   This didn't go so well at first because I hit the previously drill passage.   So much for drills!  But at least I didn't ruin the part.


I switched to a 2-flute 1/4" end mill which worked much better.  Now I can hog out the inside of this thing.  I had centered the mill on the part so this was quick work moving in X.  Recall the part is over length so I could leave the bit on the right closed up.  I assume that's better for the vise.


Here it's almost done and looking better.  I wasn't too worried about the ends (certainly not the right end) and made light passes on the inside edges until they were at the proper thickness.


Next, I drilled for pins.  I had to study this a bit, but I realized this makes sense.  The cross head doesn't pivot, and the slide bars will thread onto the cross head pin.  These little pins will keep the cross head pin from rotating and unscrewing the slide bars.  I suppose loctite might do the job, too.  I pulled out some 3/4" brass brads from my wood shop supplies, measured them, and found they would need a #63 bit.  The smallest bit I have is #60, so I looked again for larger brads, which turned out to be 1" and needing a tiny little #57.  It drilled way faster than I would have guessed.  For sure I needed a starter drill (not shown) for these holes.


I centered these locking pins within the thickness of the material by eye.   As you can see, my eye isn't too accurate with the pin hole closest to me in this photo.  Oh well.


Next I machined off the excess length with an end mill on the edge of the vise.  I suppose I could have clamped it vertically in the middle of the vise and skimmed off the top in that position.  I took a few light passes so that nothing would snag and bend.



I found there was still some material remaining in the thickness of the arms of the part.  I clamped it in the middle of the vise, removed the parallels, and lightly took some passes.  I got a little too aggressive and popped it back like this.  Thankfully I didn't ruin the part (or me!).


I guess I was feeling lucky and went back at it despite my near miss.  I continued very light passes (< 5 thou) and it finished up fine.



The corners still need rounding over and I decided I'll make buttons to help guide that.  But it occurred to me that I could locate those buttons with the cross head pin, so I decided to make the crank pin next.  Rounding will happen later.

The Cross Head Pin

Recall I made the cross head hole with a D bit which is 0.246.  Here I have some 1/4" rod and I skimmed those few thousandths until I got a nice snug fit.  It presses in with heavy finger pressure.  No press needed of course.


I decided to thread the ends for 10-32 so I turned the 7mm length down to the necessary size (0.190") and threaded it.  I turned it around, parted it off, and did the same.  Not much to it.


You might notice I did better on the left than the right.  I did the right side threading first and found I couldn't get the thread all the way to the shoulder, so I used the parting tool clean it up.  On the left side I showed I learned something and used the parting tool up front to turn the minor diameter.  When I threaded it, the threads came out perfect right up to the shoulder.  Well, maybe the threads aren't exactly perfect, but I can run a nut right up to the shoulder.  I've never read how to do this before, but it sure turned out nice.  Or maybe I just got lucky.


Next I turned a 3/8" button and attached it with a nut on the 10-32 threads.  I could see this might work, but the nut is too big and would interfere with filing.  I didn't think to measure the nut.



So plan B was simple enough.  Make a couple filing buttons that are tapped for 10-32 instead.  Note that I needed to drill a recess to clear the wider part of the cross head pin.  The buttons fit nice.  It was looking like easy filing ahead.



And filing was fast and easy!  The nice thing was that this part was big enough to clamp.  Filing it down maybe took 2 minutes.  Maybe.



Spiffy.  And it looks right at home on the engine!



And that's it for today.   Next up, I will switch to the connecting rod assembly, and then later I'll get back to finishing the remaining parts for the cross head assembly.

Todd

Offline b.lindsey

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Re: Pottymill horizontal engine build
« Reply #39 on: January 13, 2015, 12:06:42 AM »
 Another nice update Todd. Still following along eagerly here.

Bill

Offline Don1966

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Re: Pottymill horizontal engine build
« Reply #40 on: January 13, 2015, 02:30:00 AM »
Nice bit of work there Todd she's shaping up. pulling up a chair.  :cheers:

 :popcornsmall:
Don

Offline Jo

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Re: Pottymill horizontal engine build
« Reply #41 on: January 13, 2015, 08:11:39 AM »
Hi Todd,

It is looking good  :ThumbsUp:

When you use the filing buttons if you file with the buttons , i.e. following the curve , rather than across you should find it easier to achieve the right curve. I also use a marker pen on my buttons/work so that I can see where the metal still has to come off the item ;)

Jo
Usus est optimum magister

Offline Jim Nic

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Re: Pottymill horizontal engine build
« Reply #42 on: January 13, 2015, 11:29:12 AM »
Looking good Todd.  I'm following with interest as I plan to build Stew's Cross Single shortly which uses the same cylinder arrangement.
A point regarding filing buttons is that as well as filing with the curve of the button rather than across it as Jo says, if you arrange the buttons so that they are free to rotate your file will shape your part down to the point where it rides over the turning buttons but will not remove any metal from them thus ensuring a truer radius on your part and saving the buttons for use another time.  ;)
Jim
The person who never made a mistake never made anything.

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #43 on: January 13, 2015, 05:19:45 PM »
Thanks for the comments!

I have filed with the filing buttons when I switch to a fine file and hold it by hand.  I should include a photo of that, but I keep running out of hands :).  I should come up with some way of allowing the buttons to rotate, though.  Maybe it's because they are so small, but I keep coming up with solutions that won't do that.  Maybe I need to think a little harder.  Some kind of bushing could go over the screw first, I suppose.

I like the idea of using a marker as an indicator that I'm cutting into the button.  Maybe I should paint it with layout dye.  I've done that a few times on the lathe when I want to know precisely when I make contact with the work, and it works pretty good.

I'm really liking using buttons for this kind of work.  Honestly, I can't say I've seen them in any books or magazines.  Are there other names for them?  Seems odd.  But maybe I haven't read enough.  I've only been at this for a bit less than a year.

Todd

Offline Steamer5

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Re: Pottymill horizontal engine build
« Reply #44 on: January 14, 2015, 06:50:40 AM »
Hi Todd,
 Looking good.

For filing buttons I use a rod of the right dia for the holes threaded at both end, make it long enuff for nylock nuts both end your buttons & part, & a spring that goes over the rod between the locknut & one of the buttons on one side, adjust the tension on the spring to hold all together, file away! As you hit the buttons roll, the nyloc nuts hold all together. With out them the gnome gets to play with your nuts, as they fired from the spring!
A trick that I don't remember seeing taught to me by an old friend when filing a round end, is to start to file down the far side of the part, as you push forward drop the handle down the front side & you produce a rounded surface.......hope that makes sense.

Cheers Kerrin
Get excited and make something!