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Building a flywheel

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PaulR:
I'd like to try fabricating a flywheel with (flat) spiral 'spokes'. These will be sawn and filed from a single piece of ~2mm thick steel sheet which will be soldered into the rim and a separate boss added. After a couple of hours of head scratching I figured out how to draw a suitable pattern, the steps are in the attached image if it's of use to anyone (the ID of the tube I have is ~68mm hence the odd size).

As I'm not sure I could mark out the metal directly with great accuracy (although I will give it a try first), I was planning on using a paper template. After wasting about half a tree worth of paper I finally figured out how to print the design to size. I don't think a paper template would last long if glued to the metal so I thought about gluing it to a piece of MDF, filing that to shape then fixing the steel disc to it (via a central hole) for filing. That might mean the wooden template could be used again and would stop some of the squealing while the metal is being filed!

If anyone else has done this or has a better method (using lathe and hand tools only) I'd appreciate any tips before putting file to metal  :D

Jasonb:
The traditional way to stop scribed marks getting lost was to go along the line with a series of dot punch marks. You could do the same glueing the template to the blank and then punching through that at say 3mm spacing then it would not matter if the paper wore off.

Drill six holes evenly spaced to start with in the "v" of each pair of spokes then saw to that before filing. A new sharp junior hacksaw blade that still has plenty of the wavey set to the edge can be made to cut to a curve if you lean it to one side once the cut is started which will reduce the amount of filing.

ShopShoe:
Just my brain cells ticking along in the background.....

Could you saw and file a stack of spokes together so they are all alike? You would need a way to hold them together, either a jig or maybe hot glue or double-sided tape would help. Or soft solder you later melt away?

You might need a filing jig ("filing rest") to hold the files perpendicular to the stack to ensure more consistency.

In my pre-machine maker days I often did things like that.

ShopShoe

crueby:
I remember  a thread from years ago where Chuck Fellows had a jig he made to do curved spokes. Would be worth searching his threads for it.

vtsteam:
Hi Paul, for lasting templates for model airplane construction, I always used aluminum flashing material cut out with tinsnips after first pasting paper patterns on via spray contact cement like Elmer's or other brand used for photographs and paper. Spray the paper and metal separately lightly and let flash dry briefly before pasting down.

For making and printing tiled paper patterns (which can can span multiple pieces of paper) I have always used the program PosteRazor (available online free). Maybe your flywheel is small and doesn't need it, but if you do any large projects, it's handy. I use a cheap plastic paper cutter to size those sheets to the registration marks when taping together to make a big pattern.

Scaling can be a problem with .pdf drawings. You want to be sure to turn off all auto-scaling and centering in Adobe Reader preferences, or you will get frustratingly unexpected results.

As far as actually making the flywheel -- well, shortly, I'll be in the same boat as you, except for the materials and shape.

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