Stuart 10V Build Log

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raynerd:
Do you mean the ring of holes for the cylinder covers?

How about turning down another tight fitting bar to insert in the bore (once the cylinder has been bored and faced) and then holding the bar in the chuck on the rotab and drilling the holes. Because it will be turning based on the bore they will then be concentric right?

DMIOM:
Chris - if your mill's DRO has a PCD function then just use that - no need for the rotab; otherwise the rotab idea should be OK.

NickG:
The rotary table idea sounds fine to me. It's not critical that you get the bore in the centre of the casting, what is critical is that when you bolt it to the standard, the bore is concentric with the bore for the crosshead on the standard. Also, the distance from the centre of bore on the cylinder to centre of valve guide might be, depending on how much you can move the eccentric on the crankshaft. Looking at the picture on Stuart website you can move the eccentric sheave either way on the crankshaft so that's not critical either.

incidentally - £502 + VAT so £590 for the finished 10V from Stuart!!!!!

Nick

madjackghengis:
Hi Chris, you are getting good advise from all corners it seems, the issue with the bore, the ports, and the cover holes all center around the fact the outside of the casting will remain as cast, other than the machined faces. If you center the rough cylinder in a four jaw, and use an indicator to get the two sides which are the same, equal, and then get the third round side within a few thousandths of the two, you will have centered the main part of the cylinder, and it will be fine. The center line of the center port, must be at the center of the cylinder, and in my experience, you will probably clean it and the other two ports a little bit with a slot cutter, but it is important for valve timing, that you get that port pretty well centered, within a few thousandths is easily close enough. As Nick said, once the boring is done, and the facing off of the ends, if you have a DRO, and it has the bolt circle function, that is the easiest way to get the hole in proper position, just remember the radius you use in that function and you can use it for the holes in the standard, and for both heads as well, and get pretty much dead on. You certainly did a fine job getting all your mounting holes drilled in proper and it is starting to look like an engine. The reason for starting the boring from centering on the outside of the casting is to ensure you make up for any shifting of the bore core in the pouring of the casting. Thirty years ago, no one expected the cast bore to be centered, but casting techniques have improved a lot, and people expect bores as cast to be central, and such. Off subject a bit, I lost very little, just some of the collection of junk that could someday be something else, mostly. All the important things are fine.
I appreciate you posting of the drawings, they help with perspective a lot. I think you're going to get through this rather quickly at the pace you've set, and will be steaming an engine in a few weeks or less. Getting the ports central, end to end, is critical because it will provide equal lengths for timing the valve, and minimize compromise, which is always a factor in steam timing. The casting is quite long to ensure you have plenty to get it centered. You're making wish I could close up my shop doors and pull my kit out, and get back to work on it, rather than the next week cleaning out all the trash and setting up shop again. I'm really looking forward to the video you're going to post when this engine is steaming and the grin goes from ear to ear. By the way, can you tell me what "PCD" stands for? We call it hole circle function, here in the colonies, and I can't guess what the PCD stands for. :beer: :jaw: :nrocks: jack

Stilldrillin:
Jack,
Pitch Circle Diameter....... :thumbup:

David D

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