machining a stuart7A

[brikk]

several months/years ago there was some discussion conerning a stuart 7A
I was wondering if anyone was still around and could give me some info about machining the cylinder for one
thank yoiu
K

[Mcgyver]

I made one but it was so long ago I'm not sure i can remember things that specific....what do you need to know? I might have the used the piston rod as a mandrel then held it in a collet...ie face drill and tap the piston then use the piston rod with the piston on it to turn the piston OD.

[JCHannum]

Welcome to the board.

Here's a link to a build of the Stuart No. 1 engine. While the engines differ, the methods for machining the cylinder and other bits are applicable. This gent appears to do all the work on the lathe, if a mill is available that ill simplify some of the procedures. Have fun and show us your progress

http://www.steves-workshop.co.uk/ste...uart1index.htm

[brikk]

Thank you very much for the link, a quick glance at it tells me it may have what I need.
Thanks again
K

[gizmo2]

I start with a file, and work the bore until a rod will just tap through. For instance, let's say your rough casting won't pass a 3/4" rod yet. File until the rod starts, then layout blue will show you the high spots that need worked down. Once the rod will go through, you can work between centers or use the rod to indicate with the cylinder chucked up in the four jaw. Single point the bore and do the mating surface at the same set up. That'll insure the cylinder casting aligns well with the frame. I looked at the link to Steve's workshop, and he says this is no good, as the rough bore is not guaranteed to be concentric. I'm currently only on my SECOND steam engine, a coke bottle like yours. However, this method gave me a good start on the second model, and I found the castings have enough extra meat in all directions for this to work (for me) Once you've established the bore line and that first face, you'll have a reference to work to. Good luck, and like Jim says, keep us posted!

[brikk]

Do you have a set of plans for building that cylinder?
not sure how ask about a hole that appears to be needed in each end of the cylinder into the openings for letting the steam into the outside ends of the cylinder.
if you have a set of plans I would be happy to pay you for you time and postage to send me a copy of just the cylinder machining detail
K

[Mcgyver]

I must have been half asleep...thought you said piston not cylinder. Glad you got it figured out

[gizmo2]

I'm building the PM Research model 5B, so I don't know how similiar they are. I'd be happy to send you the prints tho! And with a little head scratching you can probably figure it out. I bet somebody here can do you better with the real deal, tho'. Let me poke around and see if there's a way to contact you on the side here on this new web page format.

[brikk]

I have a set of PM coke bottle plans and a set of stuart mill engine plans they appear to be pretty close so maybe I will be able to muddle through this if I can't find a set of 7A plans
If nothing else and I drill them wrong I have gotten pretty good at patching holes LOL
K

[gizmo2]

Here's a way you might approach it... Machine the bore, ends, and features of the valve box to their final dimension. The center (exhaust) is generally a little deeper and twice as wide as the two end ports, just base them off the valve and scale them from the PM plans. That valve has to cover the exhaust and one port while the other takes the steam. Anyway, once those basic things are machined, draw up the cylinder as big as will fit on a piece of paper, let's say 5x, using all the dimensions you can measure. Then pencil in those angled holes so they look right. Then you can measure the angle and size of the holes. Any error will be 1/5th on the finished part, and should work just fine.