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| Stuart No 4 Build |
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| kwackers:
Not quite a build log - since I'm half way through and have taken no photos (until now), but I thought I show it anyway Base, sole plate, standard, cyclinder, crank, mains, bottom cylinder cover & gland, piston rod and con rod have all been machines (as per pic below). Also a pic of the jig I used to machine the crank main (crankshaft is a casting on this engine, ends are centred and main shaft machined to size both sides, then a pair of holders are made up and clamped to the shafts to allow the crank to be offset to machine the bottom end). Most of the rest of the machining is fairly standard, holes have all been drilled using a mill with DRO, cylinder holes drilled using PCD on DRO. The steam chest has been drilled to take the reversing gear. Next task is piston and top cylinder cover - then the core of the engine is done. I'll then start on the reversing gear. (Pics to follow). I'm quite pleased with progress so far, I'm slowly but surely finding my ability to machine parts accurately improves. In fact I've a set of castings for a Stuart Major beam and I'm feeling fairly confident about starting them (I'll definitely do a build log for that). Engine before this was a Stuart No8 - once I've nailed it to a piece of wood I'll post some pics. Parts machines so far. Crankshaft machining jig. |
| DavidA:
Kwackers, Looking at the bottom picture. I've not done this myself, but soon will need to. But I do recall reading somewhere that you should insert 'jacking screws' in the gaps in line with the centres, between the webs. The idea being that it prevents any distortion when you apply pressure to the tailstock centre. Have you considered this ? Not trying to tell you how to do it, how could I if I haven't done it myself ? but it looks like a potential problem area. Dave. |
| kwackers:
Hi Dave, The jacking screws sound like a good idea (I did worry about distortion). I checked to see what sort of movement I was getting and came to the conclusion that it was acceptable (bear in mind it mainly flexes the webs). I think (iirc) the bar I've made the holders out of is 3/4" so I don't think there'd be much 'racking' of the shafts. It's a fairly large crank and not held too tightly and the finished item seems spot on, my previous engine (No 8) had a much smaller crank that was made in the same way, I reckon that would probably have benefited from screws (again, I'm not aware of any issues with it). Thanks for your comments, something learned I hadn't considered. I've another No 4 to build so I'll seriously consider adding jacking screws to the jig, at the very least it'll take away any worry of something 'bad' happening! Steve. |
| NickG:
Steve nick work on those castings, the No 4 is quite big isn't it? |
| arnoldb:
Thats a nice job you're doing Steve :thumbup: I especially like the drain cocks on the cylinder! :beer:, Arnold |
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