Author Topic: Pottymill horizontal engine build  (Read 62990 times)

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #180 on: May 09, 2015, 02:51:09 AM »
Well done, I can't wait to see it all polished up and stood on its base.

Thanks a ton for the encouragement!   I spent quite a bit of time in the shop this evening polishing away.  I only hope to get 1/100th the shine that Don manages to produce (maybe he'll do a "polishing log" for us someday!), but even so the parts are looking pretty good.  It's completely disassembled right now so I hope I can get it all back together again.  I'll take a picture of the parts, too.  It's quite a "kit" right now.

Todd

Offline b.lindsey

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Re: Pottymill horizontal engine build
« Reply #181 on: May 09, 2015, 03:48:51 PM »
Todd, there was some discussion in Don's Eastern & Anderson thread as to finishing, wasn't sure if you had seen it or not. You can find it here and it continues off and on for a few pages.

http://www.modelenginemaker.com/index.php?topic=4629.msg90113#msg90113

Start with reply #104

Bill

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #182 on: May 10, 2015, 12:35:21 AM »
The Kit of Parts

I just finished polishing and making the base.  Here's what a kit form of the pottymill horizontal engine might look like.



Fortunately, a lot of those parts are fasteners.  Even so, there are quite a few parts and it was fun making every one of them.

I had generally sanded most of the parts through the grits to 320 and stopped.  I probably should have gone further, but I was mainly looking to remove the bigger scratches.  I'm not shooting for a mirror finish, but I'd like a shine on a few of the parts and especially the flywheel since it turned out so nice.   I polished with a hard(er) wheel and green stainless compound first, and then hit the parts with a soft wheel and blue all-purpose.  I probably should have started courser, but thought I'd see what this would do first.

Two things caught my attention.  First, the base was really getting a mirror finish and I decided I didn't want that because it was so large and flat and would distract from the rest of the engine.  So I brushed it with a fine wire wheel and smoothed it out with green pad.  Now it's just ordinary aluminum.   Second, the shaft supports had a rather nice looking finish direct from the bar stock that I thought was interesting, so I only polished the edges.

Now I need to put the thing back together and get it tuned back again.  That should happen over the next few days I hope.

Todd

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #183 on: May 10, 2015, 12:37:14 AM »
Todd, there was some discussion in Don's Eastern & Anderson thread as to finishing, wasn't sure if you had seen it or not. You can find it here and it continues off and on for a few pages.

Bill, yes I followed that with great interest.  It really reminded me how little I know about polishing.  There are new things to learn every day!

Todd

Offline b.lindsey

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Re: Pottymill horizontal engine build
« Reply #184 on: May 10, 2015, 12:53:25 AM »
That's a great "exploded" picture Todd. I really do like this engine!!

Bill

Offline zeeprogrammer

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Re: Pottymill horizontal engine build
« Reply #185 on: May 10, 2015, 01:16:07 AM »
Fantastic family shot. Very nice.
Just watched the video. That is one great sound.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Online steamer

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Re: Pottymill horizontal engine build
« Reply #186 on: May 10, 2015, 12:49:59 PM »
Sweet!!
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline rodw

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Re: Pottymill horizontal engine build
« Reply #187 on: May 12, 2015, 04:38:45 AM »
Awesome work. Been following this build religiously and I dont often do that.
RodW
Brisbane, Australia

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #188 on: May 13, 2015, 04:07:29 AM »
More Tuning

I've disassembled the entire engine (you saw that earlier), gave it a bit of polishing, and am in the process of reassembling and tuning as I go.  It's slow going.   I reassembled it completely and it was mighty stiff, so I backed off and am working on it component by component.  Here's what I've learned so far.  All of the problems so far are my own making.  Oh well, I'm learning as I go.

Here is one of the first things I noticed, and I noticed it earlier as I assembled the engine.  The valve chest is just a teeny bit oversized so it's pushing the cylinder head away from the cylinder.  That's causing a leak.   I had pulled the cylinder/valve mechanism (shown in the blurry photo -- sorry about that) off the engine, gave it compressed air, and was working the valve manually with my fingers.  The piston would snap out, but wouldn't snap back in.  The problem is this leak as far as I can tell.


I removed the valve chest and skimmed 3 thousandths off the end on the mill.  I did this by cranking the mill into the chest until it started cutting and went an extra 3 thousandth of an inch on the dial.  No fancy measuring.  That seemed to be enough.  I didn't take a picture of it.

The next thing that was really bugging me had nothing to do with tuning at all.  As I removed and tightened bolts, I kept scratching up the aluminum in a way that was really difficult to polish.  When I'd polish over the bolts it would create ugly "shadows" (not sure how to word this).  I needed a way to tighten/loosen these bolts without scratching up the works.  I came up with the technique shown in this photo.  I first tried to put electricians (plastic) tape on my wrench, but that didn't work well, so I punched the tape with a paper hole punch and applied it.  I reused this many times and it held up fine.  It gummed up the aluminum a little with stickiness, but that was easy to remove with a little oil.


Now I simply had a stiff engine, and it wasn't clear at all what was making it stiff.  So I started disconnecting stuff.  Step 1 was to disconnect from the crank and make sure the flywheel assembly turned smooth.  It did.


The crosshead guides were binding.  I could loosen them and it would work better.  I'd test this by sliding the cross head manually since it was no longer attached to the crank.  So it was time to skim the slide bars.  I took off 5 thousandths from both top and bottom.


This helped, but it was still binding.  I removed the guide on the valve side of the engine and it loosened up a lot.


It turned out the slide bars weren't at fault for the binding on the valve side.  It was the brass thrust washer.  I happened to have one that was a few thousandths thinner, replaced it, and now that was working well.  It goes to show you that you should save your "junk" parts until the build is finished.  I had made this thrust washer as a test part and thought it was too thin!

By the way, another useful thing was that it was very handy that I made the temporary pine base you see clamped in the vise.  It held the engine and it was ok for me to get oil and other gunk all over it.  Otherwise I'd be messing up the nice black walnut base you saw in an earlier post.

Now the engine was cranking fairly smooth by hand.  A little stiff, but not too bad.  When I applied air it took A LOT of pressure to make it run.  I was at over 50 psi.  The energy was going somewhere.   Now, this is fairly high pressure, but I discovered the cylinder was leaking when I dribbled a little oil on it.


In the plus column, the rear cover is solid.  No leaks I could find.  but both the valve chest and the front cover are leaking pretty bad.  I need to figure this out.

I'll probably re-do the piston rod packing, and maybe re-pack the piston as well.   The valve is a bit leaky too, but then again I'm applying a rather serious amount of air pressure at the moment.

Todd

Offline sbwhart

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Re: Pottymill horizontal engine build
« Reply #189 on: May 13, 2015, 07:26:58 AM »
Hi Todd

Good work with the fine tuning step by step is the way to do it.

As for the leaks arround the valve chest all you need is some silicon sealant Hylomar or some such product you'll get it from your car spare shop.

Hope this helps

Stew
A little bit of clearance never got in the way

Offline Jo

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Re: Pottymill horizontal engine build
« Reply #190 on: May 13, 2015, 11:14:39 AM »
Sealants: I was recommended to use Wellseal, rather than a silicon sealant which have a nasty habit of going hard in the tube  >:(.

Todd, I can't remember, :old: have you used gaskets to help the seal?

Jo
Usus est optimum magister

Offline Jasonb

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Re: Pottymill horizontal engine build
« Reply #191 on: May 13, 2015, 12:59:31 PM »
I use a blue instant gasket from Halfords (car accesory chain store) which is a silicon base, had the current at least six years and it was still working fine last week.

A washer under the nut will save your tools making themetal/paint.

J

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #192 on: May 14, 2015, 05:27:45 PM »
Thanks for all the advice!  For some reason a gasket feels like cheating.  I suppose I get this thought because the surface area of contact is rather large on these parts, and if the surfaces are good it seems that it should be enough.  But maybe I'm just being a bit naive :).

I'll double check the surfaces are reasonably tight first.  Maybe I have a burr on a screw hole or something like that.  I did change the fasteners on the valve chest from philips head screws to hex head "bolts."  It's possible I'm not getting them as tight.

Jason mentioned washers and it's interesting that I thought of that, but don't have any in these teeny sizes.   I see microfasteners has some, so I'll add that to my list.  Not sure why I didn't look for them when I got the bolts.  But a "real" engine wouldn't have washers in these places, would they?  I'm trying to think through in my head why they'd use them.  Maybe I need to look at some photos.

I'm off to run full size steam traction engines this weekend so my build will pause for a bit.  But I'll be having a different kind of fun, and I could look at how parts are bolted together.  Maybe I should be using studs in some places as well.

Todd

Offline NickG

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Re: Pottymill horizontal engine build
« Reply #193 on: May 14, 2015, 07:13:12 PM »
A real engine (I would have thought) would have gaskets and washers Todd. They help spread the load.

Offline rodw

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Re: Pottymill horizontal engine build
« Reply #194 on: May 14, 2015, 08:22:11 PM »
A real engine (I would have thought) would have gaskets and washers Todd. They help spread the load.

I'm sure gaskets would have been used too. As a kid in the bush where life depended on several stationery motors from the early post steam era, I can assure you that gaskets were everywhere. For some applications we even made them from leather. We used to use some gasket goo pre silicone era which you can still get from a bearing shop and it was kinda strange to go naked via a smear of silicone in later years. Just be careful that you don't use too much silicone so it builds up in the inside, vibrates off and blocks the valves. I had this happen when I had a Weber carby fitted to a car years ago and the excess silicone on the air inlet side blocked the carby after a few days. The boss was very cranky with his mechanic....

I might be proven wrong but from this experience, I'd be tempted to use goo and you'd be more authentic too!
RodW
Brisbane, Australia