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September 19, 2017

Vulcan Beam Engine 3 – The Flywheel

by martinbrewster2010

As much as I would love to describe the definitive way of setting up and machining the Flywheel, I can’t!  This is a case of luck rather than skill, but it worked for me.

I wasn’t sure whether I liked the flywheel or not, it looked more like a hand-wheel rather than a flywheel, but thats just my personal opinion.  It was one of those components you stare at for a while, scratch your head and then put straight back in the box. The casting does have a cast boss for holding, and the actual wheel boss itself, but what are the chances of them being concentric?  I tried gripping it in the lathe but it didn’t look right, and if there’s a quick way to spoil a model fit a flywheel that runs out of true.  I’d just about exhausted ideas and finally resigned myself I was going to have to use the Faceplate to machine this with any accuracy, (I once had a nasty experience with a faceplate) when I noticed the Flywheel was a bit warped.  As far as I was concerned it was a s**t or bust moment, so I remounted it back in the lathe, used a marker pen to find where it was running out and then hit it with a soft hammer.  I don’t know who the patron saint of engineers is, but he must have been smiling that day.  It was like a miracle, the whole thing was running dead true, seize the moment!!!  Make sure the chuck is tight, extra light cuts on the boss, gently face it, then drill the 11mm hole for the shaft.  Turn the wheel round in the chuck and grip on the machined boss, still running true, face the other boss machine the outside diameter, this is too good to be true.  Now it’s time to deal with the outer diameter.  There was quite a bit of material to machine away to get rid of imperfections but once again light cuts and a slow speed prevented too much chatter, and the bit that was there was soon dealt with using 240 grit wet and dry.  Gradually reducing the grit size down to 1200, it didn’t take too long to get a good finish, happy? You bet!!

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The shaft I turned to suit the bore so I could get a good fit, just a case of machining a couple of hundredths of a millimetre oversize and reducing to suit with wet and dry.  Decision time, do I machine a keyway or do I take the easy option of just using a grub-screw to secure the Flywheel to the shaft?  I think elation took the better of me, it had to be a keyway.  The shaft keyway was a simple milling job, no great worries there, but what about the flywheel?  Fortunately I had broached keyways before on the lathe and knew what to expect, it’s not a two minute job even on a fairly soft material such as Gunmetal. Firstly, grind some tool-steel with a top rake angle, set it dead centre height in the lathe and then push it through the workpiece with the saddle using very small increments of cut.  You will get deflection on the cutting tool so be prepared to finish off with needle files.  The key is just a cut and file job pretty simple.  Is it worth the effort?  Well, I like it, what do you think?

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