Piston Rings

June 7, 2010 at 1:10 pm | Posted in Uncategorized | Leave a comment
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There’s a thing with piston rings. When you make them, they start out round. You cut a notch in them with a slitting saw, then put a piece of 1/4″ or so of steel and heat it red hot then let it cool. The idea being that the gap will be pressed closed when it’s in the cylinder. There’s a bit of a problem with this, however. When they go in the cylinder, they are oval. Philip Duclos discussed a way of dealing with this by holding the ring in a clamp with the gap closed and finish machining it. This is a nuisance. The other option is waiting for the rings to seat.

This can be sped up by using something like timesavers. Timesavers is an abrasive that breaks down with time and doesn’t embed. As it wears, it becomes a finer and finer grit. This way it can speed up ring seating without damaging the cylinder. I need to pick some up. I’ve been working the piston back and forth in the No. 1’s cylinder, and you can see how the rings are oval. They’ll seat in time, though. Just need to make sure all the grit(from honing the cylinder) is out of the steam passages.

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Projects in Progress

June 7, 2010 at 12:56 pm | Posted in Uncategorized | Leave a comment
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I’ve got a couple projects in the works at the moment. A list:

  • Kozo’s Pennsy A3 Switcher
  • Tiny Power Ajax
  • Stuart No.1
  • Stuart Sirius
  • GWR Collett(from Engineering in MIniature)

I’m thinking of adding the Darjeeling engine from Model Engineer that they just started. Very nice engine, and I’d like to follow along with the article as they print it. I need to cut some steel for the frames on that one.

There’s another project on my mind. A model of 6069, currently parked in Centennial Park. I’ve been volunteering with a group that is restoring it presently. It occurs to me that this is a perfect time for measuring to design and build a miniature. It’s a beautiful engine. I need to get the works drawings so I can figure out the frames, I’m thinking something in 5″ gauge.

Further progress in the shop.

June 7, 2010 at 12:26 pm | Posted in Uncategorized | 1 Comment
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The Stuart No. 1 is progressing nicely. I finished drilling the upper cylinder head yesterday. A photo:

Photo on 2010-06-07 at 12.04.jpg

The spigot in the center needs to be taken off. I loctited the head to the cylinder, and mounted the rig in the mill on a rotary table. I drilled both with the tap drill for 2BA. After drilling, I knocked them apart with a hammer and opened the holes in the head out to clearance size. I was then able to clamp them together(using a large kant-twist clamp) and use the head as a tapping guide. Got the studs in perfectly straight. It’s a touch snug, but goes on wonderfully.

With the head off the cylinder:

Photo on 2010-06-07 at 12.11.jpg

The head and top of the cylinder where lapped together using clover compound. I applied a few dabs between the two and used the mill to spin the head while I held the cylinder against it. The meeting face has a nice dull sheen.

In this picture you can see the port face:

Photo on 2010-06-07 at 12.11 #2.jpg

This engine employs a garden variety d-valve. The steam passages are cast in. I still need to lap the port face to flatten it. I think I will do this before drilling for the steamchest bolts. It’s a pain and a half to get the lapping compound out of the holes.

Photo on 2010-06-07 at 12.11 #3.jpg

This shows the lower end of the cylinder. Undrilled for the lower cylinder head. That has to be tackled next, and it’ll be difficult. I removed the chucking spigot prematurely. I’m going to machine out the gland and use it to mount the part to an arbour. Pictures will be forthcoming on that one too.

Stuart no 1

April 1, 2010 at 1:31 pm | Posted in Uncategorized | Leave a comment
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Considerable progress is being made on the engine. The connecting rod and has been rounded. Unfortunately, the radius is offset from the centerline. If I blend things well, I don’t believe it’ll be an issue. Next step is cuttig the slot in the middle.

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