Author Topic: Pottymill horizontal engine build  (Read 62991 times)

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #165 on: May 02, 2015, 10:21:14 PM »
Tuning the Engine

I'm taking a break to report tuning efforts so far this weekend.

I removed the valve guide as I thought it might be binding slightly and it could do without it for a while.  I had made a fourth spacer so I could simply replace the guide with the spacer for the cross slide guides.  Perhaps this helped, but not measurable.

I removed the valve assembly so I could more closely study the operation.  I could have figured this out from the plan, but it was easy enough to remove.  First, I found that the valve was made correctly.  The measurements were good.  Second, I found that the position the valve needed to be at the end of minimal travel to allow air to fully enter the cylinder.  Since my valve was mounted upside-down (remember that?) it was quite easy to adjust.

I re-installed the valve and looked straight down as shown in the photo.  Those are the exhaust ports and I'm looking at the one on the right which is near the cylinder head.  It may be hard to see...but that's the thick end of the valve that is obstructing the right exhaust port almost completely.  This is actually a leak.  Air is coming in to the middle of the valve and trying to get into the cylinder, but you can see a gap to the left in this port and much of the air is escaping!  That explains why this port is blasting more air that the other port.  At this point in the cycle, the port on the left is exhausting air.  So the valve is clearly pushed too far to the right.  Easy to fix.


From my experiments looking over the valve chest when it was removed, I learned that the valve should halfway obstruct the exhaust port when it is at the end of its range.  When it is at the end of the range the other port is exhausting and that port will be fully exposed.  Here I have the valve adjusted correctly for end of travel to the right port.


Here is a photo showing the left port when the valve is pulled to end of travel to the left.  I have it going a little too far.  It really shouldn't matter, but I balanced them out a bit better after taking this photo.  The important thing is that if the valve doesn't travel far enough to the end of the range, it won't fully open the internal port into the cylinder.  You can't see that in photos.  Experimenting with the valve chest removed was useful to learn this.


Now it was running ok, but still required a lot of air.  I re-packed the piston guide and the piston.  That helped quite a bit.  The engine actually feels rather silky going around, but I noticed a bit of tightness as the cross slide went to the right.  It occurred to me that the cross slide guides might be binding.  Sure enough!  I loosened the cross slide guides a bit while it was running and BAM!  It starting running on very low air pressure.  Here's a picture.  I kid you not -- it really took off!


But that doesn't say much, so here's a new video...

Rather than tweak the guides now, I think I'll start polishing it up a bit and will mount it to a base.  I'll take care of the guides as I reassemble as this is going to mess it up for a bit anyway.

Todd

Offline b.lindsey

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Re: Pottymill horizontal engine build
« Reply #166 on: May 03, 2015, 01:36:49 AM »
It sure is running smooth in that latest video. Very nice sound too!!

Bill

Offline Kim

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Re: Pottymill horizontal engine build
« Reply #167 on: May 03, 2015, 02:32:44 AM »
Nice... I love watching them run slow like that.  It sounds and looks great!
Kim

Offline mike mott

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Re: Pottymill horizontal engine build
« Reply #168 on: May 03, 2015, 04:57:17 AM »
Very nice, listening to that slow steady beat reminded me of my childhood watching trains on the GWR in Acton.

Mike
If you can imagine it you can build it

Offline Stilldrillin

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Re: Pottymill horizontal engine build
« Reply #169 on: May 03, 2015, 10:29:08 AM »
That's the way they should be run!

Well done, Todd!   

David D
David.
Still modifying bits of metal... Occasionally, making an improvement!
Still drilling holes... Sometimes, in the right place!

Online kev

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Re: Pottymill horizontal engine build
« Reply #170 on: May 03, 2015, 10:40:59 AM »
Nice one, been a real interesting thread this :)

Offline NickG

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Re: Pottymill horizontal engine build
« Reply #171 on: May 03, 2015, 07:23:58 PM »
Wow, runs so well, a testament to the workmanship. Are you planning on drilling an oil hole through into the main bearings ? Will be easier to lubricate that way.

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #172 on: May 04, 2015, 04:15:34 PM »
Are you planning on drilling an oil hole through into the main bearings ? Will be easier to lubricate that way.

I should consider this, but have no real experience doing it.  Would I just drill a small 1/16 inch (or so) hole straight down through the support and bearing?  The bearing is pressed and won't move around, so I think this will work.  How important is the diameter?  I've been using mobile-1 oil that I use on the ways of my machines and it seems to work well for this.

When experimenting with the engine I did find that oiling the main bearings was the toughest thing to do while it was running.  All the rest of the parts were pretty easy to oil provided a think just a little how the engine was going to knock around my little plastic oil "can."  But the crankshaft is pretty unforgiving :).

Todd

Offline Roger B

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Re: Pottymill horizontal engine build
« Reply #173 on: May 04, 2015, 06:24:38 PM »
A very smooth runner  :praise2:  :praise2:

A 1/16th hole should be fine for lubrication. If you are not intending to make an oil cup a reasonably large countersink will help to get the oil in.
Best regards

Roger

Offline NickG

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Re: Pottymill horizontal engine build
« Reply #174 on: May 05, 2015, 08:14:03 PM »
Yeah, that would do the job IMO - just an easy way of getting oil in there. As Roger says a countersink to hold a bit of oil. The 1/16" hole will probably deliver far more oil than needed and might appear to just run straight back out but at least it's an easy point to oil at the start of a run - guess that's why on large engines you would have drip feed lubricators but think a simple hole will suffice on an engine like this unless you intend leaving it ticking over all day unattended at a show.

Offline b.lindsey

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Re: Pottymill horizontal engine build
« Reply #175 on: May 05, 2015, 08:41:54 PM »
Todd, I use thinner oil (3 in 1 or Starrett Instrument oil) and for those even a hole as small as say a #60 works fine.

Bill

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #176 on: May 06, 2015, 09:58:59 PM »
Thanks all, I'll try this maybe tomorrow when I get some shop time.  I'll start with a #60, countersink it, and while it's still in the vise I'll try oil and see how it drips into the bearing.  It'll be a good learning experience.  If I need to drill bigger, it'll be right in place and I'll repeat until it drips nice.

I don't expect it'll really work as a drip oiler, but I do want to test it to make sure some oil actually flows through.  I'd feel a little silly discovering that it doesn't work two years down the road :).

Todd

Offline tinglett

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Re: Pottymill horizontal engine build
« Reply #177 on: May 06, 2015, 10:40:56 PM »
Making the Display Base

I started cleaning up and polishing parts, but decided to stop to make a proper base to re-assemble the engine.   I mulled this over quite a bit and decided to keep the base abstract and make it match my previous simple bases.  That is, nice beveled black walnut.  By "abstract" I mean I wasn't going to try to make model bricks and such.  The model doesn't have that level of detail so the nice wood plus well polished metal should have a nice look.   I need to try the full model approach -- bricks/tiles, lagging and paint -- on some future project.

But first things first.   I still need a way to mount the aluminum base to the wood base.   I decided to keep this attachment blind by drilling/tapping from the underside with 10-32 screws.  Since the plate is only 0.250 inches thick, I used a small 2-flute end mill to drill a flat-bottom hole 0.220 inches deep.  It worked well even though it was slightly undersized for the tap.


I used a bottoming tap to get as many threads as possible.  I didn't count them, but there are plenty.


Sorry for the simple tapping photos, but I thought this one was interesting.  It shows the metal curls were heavier than usual due to the undersize hole.  But it worked fine.


Next, time for the brown stuff.  In this case I used a black walnut block that matched the plate in size and used transfer punches to locate the holes.  This block raises the engine so the flywheel clears the main display base.


Hmm...I didn't take a photo of what I did with these hole locations I just punched.  I used a 5/16 inch forstner bit in the drill press to drill clearance holes in the walnut block so the screws that protrude from the aluminum plate will clear the wood.  Simple enough.  This could be messy as it is completely hidden, but I have quite a bit of woodworking gear and used it :).

Here I show a similar approach on the opposite side of the wood block using the same drill bit to countersink the bolts that hold the plate to the wood.


At the moment I am stalled hitting the wood base and block with danish oil.  A few more coats and I'll start assembling it this weekend.


Now I need to get back to polishing the bits and re-assembling the engine.

Todd

Offline b.lindsey

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Re: Pottymill horizontal engine build
« Reply #178 on: May 07, 2015, 12:22:48 AM »
A very fitting base for a lovely engine Todd. Well done!!

Bill

Offline Heffalump

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Re: Pottymill horizontal engine build
« Reply #179 on: May 08, 2015, 10:24:00 PM »
Wow, simply fantastic Todd. I've just read the entire thread as I've started to build this engine. I was really impressed with the first video, but when I saw the second... wowie! To get an engine that looks that good an runs as slowly as that is a dream, and the sound is fantastic! I hope you're very proud. Well done, I can't wait to see it all polished up and stood on its base.