Flywheel pattern making

[chucketn]

I am researching making patterns to cast al flywheels. I found a drawing from Elmer Verberg’s info at the Jon-Tom website. How do I machine the tapered spokes, shown in the drawing below, on a rotary table? I can understand the setup for drilling the corner holes for the cutouts, but how do I offset for the taper of the spokes?
Chuck

 

[Jasonb]

If you can draw it out in CAD just measure the angle of one of the sides of the spoke and set the rotary table to that angle, do each spoke then move the cutter to the other side of centre and set to that angle.

I did just that for someone last week who was having difficulty knowing how to do this 3" dia handwheel, think he made a good job of it

 

[chucketn]

Beautiful handwheel, Jason. I don't quite follow you on the rt. Can you dumb it down for me? I understand how to set up the RT centered on the table, and my dro will help drill the reference holes. Say I have the holes drilled as per the drawing I posted. Now I want to mill the first side of one spoke, the outer hole is under center. I offset the center of the RT to the angle required , left or right?
I don't have cad capability, though I started my working life as a detail draftsman, 45 years ago, I didn't stay with it.
Chuck

 

[Jasonb]

Right the angle of the side of your spoke can be measured as 2.93degrees as first picture.

If the rotary table is then rotated 2.93deg the centre line shown in green in the second picture will now be at an angle of 2.93 degrees but the tangental line that forms the edge of the spoke will now be along your Y-axis. Measuring from the Y-axis to the edge of the spoke gives 0.157" add half your cutter dia to this and that will give you how far to offset the table along the x-axis. Assume 1/8" cutter then move the table 0.219" to your left and make the cut.

Repeat for the rest of the spokes by turning the table to 62.93deg, 122.93deg, etc

When all six are done offset the table 0.219" to the opposite side of the spindle, set angle to 357.07 ( 360-2.93) cut then next at 297.07, etc

 

[Swifty]

Another way to do it would be to have your rotary table set at zero, loosen the clamps holding the table down, then place some drill shanks in one inner and one outer hole. Hold a parallel against the drills and using an indicator clock the parallel to zero and clamp the table. Now you can mill one side until the straight blends with holes, when the first one is done, in your case just rotate the table 60deg and mill the next one, repeat until one side on all spokes is finished. You will then have to repeat the same way for the other side, with this method you don't have to worry about rotating the table to odd degree markings, and on the first spoke, just zero the DRO reading to make it easier on the next one.

Paul.

 

[chucketn]

Thanks Paul and Jason. I will try this tomorrow...
Chuck

 

[SmithDoor]

Try looking at wheels
This what I had at till 2004 on Aircraft Hangar Doors

 

[mcostello]

Hey, That's cheating. I like it.

 

[cwelkie]

Another very helpful approach would be to use Marv Klotz's software ...http://www.myvirtualnetwork.com/mklotz/

I recently did one of Elmer's Grasshoppers with the tapered spoke flywheel using Marv's software and a rotary table. Turned out very nicely due to the software I'm sure.

One does need to be willing to sort running the software in a MS-DOS environment but the result is worth it.

... you probably just forgot about all the useful utilities Marv has shared with us!

 

[SmithDoor]

The top wheel is only 95 lb 17" dia the lower wheel is 1,000 lb 27 dia
I only kept the 2 smaller size 10 lb 9" dia and a 20 lb 12" dia for fly wheel
All are class 45 iron

Dave

Hey, That's cheating. I like it.

 

[kvom]

I drew the hole configuration in Draftsight and got a different angle than Jason. Here's my drawing.

If I rotate the holes 3.8 degrees the offset from the Y axis becomes .219".

 

[kvom]

The other thing to consider is that it is quite difficult to mill a perfect tangent path between the two holes. There are the issues of the holes being the exact size drawn and the angle being sufficiently precise. Best is to allow a few thou of clearance that can be evened out by filing.

For a casting pattern you need to have draft angles in the spokes and rim and account for shrinkage.

 

[Jasonb]

Your 1/8" hole is not 5/32" off from the centre so that probably explains the different angle.

 

[kvom]

I guess I fumble-fingered the hole placement.

Anyway, redrew and got 2.93 degrees to agree with you.