Building Up a Flywheel - One Way to Do It

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Senior Member
Jan 22, 2009
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This is in response to a couple of posters in Brian's ongoing Corliss build. This is a suggestion for one way to do it. My disclaimer is that although I've used all these techniques at one time or another, including pressing on an outer rim, I've never used them all on the same flywheel, preferring a casting.

The quick synopsis - the outside spoke ends will be covered by the main rim.

First, assume that what you are building is the "casting," to be finished all over by various means.

Turn the hub from the material you've chosen, and leave machining allowance in the bore. Finish turn the external surfaces. Index and drill the hub rather deeply for spoke spigots.

Make the spokes and turn a spigot at each end, long'ish spigot at the hub, short spigot at the rim.

Turn a ring (NOT the final outside rim) for a spine or sub-rim, finished on all but the outside (OD.) Index and drill this ring through for the spoke spigots. Split the ring (using a very fine saw) between one pair of spokes.

Assembled the spokes into the hub and expand the ring to allow it to snap over the spike outside ends. When completely assembled wire the split together and solder the whole. As this assembly won't be exposed to heat, and because it has sufficient strength to take whatever stresses, soft solder could certainly be used instead of silver solder. If you use silver solder, meticulously clean the parts of any oil or fingerprints and flux as you go.

Treat this assembly as the flywheel casting and clean it up (filing, dressing, etc) as you would a casting and prime paint.

Chuck the casting up and finished the OD and sides of the sub-rim.

Turn the ID of the (separate) main outside rim to a light press fit over the inner rim and press this home. Heat expanding the outside rim should allow a drop-on fit, but make sure to support it so as to align it squarely. A weensy step in the rim ID will also work.

Chuck the entire assembly and machine as necessary as if it were one casting.

Here's an example of what can be done in building up a wheel . . .
This is a flywheel for the Sanderson 1" Beam Engine, 9-5/8" diam, with 1-piece rim. The trick to this one was, first, to cobble up an attachment to counter-drill the spoke spigot holes in the rim, and as for the hub ends, the hub was split. This is not my work, it was built by a fellow in London UK.
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Thanks Harry,
A beautifully presented finished product. Love the detail e.g. red lining at the base of columns, fluted con-rod, column, etc. Proper modelling!
Well done.
And thanks for the tutorial in building a flywheel. (I have a brass ring that needs hub and spokes, so will put this on the list of projects now!).
K2 and others . . .
Oh my! I just realized I failed to mention this is NOT my work (now corrected.)
I posted this wheel as an example of what can be done by building up.
As I recall it is the work of a fellow in London whose name I didn't record.
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Here's another dodge I've used with some success . . . a way to widen the rim and include belt grooves in an otherwise narrow flywheel (Stuart #10H). The sketch, which is for example and isn't to scale or proportion, should be self-explanatory.

You first reduce the rim of the original casting by the amount you determine. Then split the new rim material and turn a step and shoulder as shown. This is pressed or Loctited over the reduced rim and turned and grooved for ropes. If you locate the parting line in the bottom of a rope groove the line will disappear and never be seen.

I first used this years ago for a Stuart Tandem D10H, based upon a series of articles in ME by Tubal Cain (IIRC) for improving the appearance of a the basic D10.


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Here is yet another alternative to a built up flywheel. (I hadn't added the barring holes/slots)
This type was mostly used on very large engines I believe.


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