Mandrel for Flywheel Turning

Machine Shop
#1

  1. What is the diameter of the mandrel we have for the lathe?

  2. The flywheel I want to turn is 0.85" thick at the hub but only 0.4" at the edge. I have some brass plate that is 0.6" thick and some 1" brass rod. Can I press fit the 1" bar into the brass plate? That really the wrong question. If I press fit the 1" bar into the plate will it be strong enough for turning without slipping or do I need to add some Loctite or something? Also, how much smaller does the rod need to be to press fit?
    Flywheel Drawing v1.pdf (71.7 KB)

#2

I wouldn’t count on it not slipping if just press fit. Looking at drawing not sure where you’ll press fit a 1.000" bar. The through hole is .1875" and the shaft is .625, the recess 1.25" so I assume instead of .625" inside the 1.25" it would be a 1.000" shaft inside a 1.25" recess and would be there permanently.

What am I overlooking or missing

image
image.png624Ă—695 34.5 KB

1 Like
#3

I had planed to press the 1" bar into the plate before doing the turning so that I would be working with essentially a single piece. The dimension can be changed a bit. The diameter of the shaft will have to change to fit our mandrel. I could turn the 1" bar down to .625 and press that in. That might be easier although I would probable still need a bit of light turning after. I might also be able turn the main part of the flywheel, press fit in the rod, solder or braze the joint after pressing and clean it up. I’m trying to avoid buying more brass. It’s really expensive.
I could just use steel. I have a big piece of 1" steel but I’d have to cut it on the plasma cutter and I’ve forgotten a lot I learned in that class.

#4

For it to work right, the mandrel needs to be slightly tapered. I think we only have 1/2” mandrel. Also we only have the 1 live center. You don’t want to mar the mandrel. If you did a straight shaft, you could used green Loctite (bearing Loctite) then use heat to free it. Something like this http://www.loctite.com.au/3320_AUE_HTML.htm?nodeid=8802648195073

#5

What is the machining process from stock you have in mind?

#6

I’m making a flywheel for a small steam/air engine. If I had a solid piece of .75 inch brass 2.5 inches in diamerer., I would just turn it on the lathe or use the rotating table on the mill. I’ve only got .5 in plate I was going to try and use some round stock to make the hub bigger. I think I’ve figured out a different way to make it that won’t require extra thickness

#7

Modify the wheel dimensions so that the rotational mass is the same. The calculations are beyond me but they can be done.

1 Like
#8

I would make this in one setup if possible to ensure concentricity. I concur with David.

#9

The reason for the larger center hub was so that I could I could put in a set screw in to make disassembly easier. The flywheel will be between side plates. The rotation mass is not critical. I think I will make the sides removable and use loctite to attach the flywheel to the shaft eliminating the need for a set screw. There are no great forces on this while it’s running. What I’m building is loosely based on the double cylinder, double acting engine call Yellow Boy built by Tublican (mrpete).