Why did my Flywheel Wobble?

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Why did my Flywheel Wobble?

This topic has 15 replies, 12 voices, and was last updated 14 May 2014 at 14:59 by Nigel McBurney 1.

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18 May 2011 at 21:17 #68810
Steve Withnell
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@stevewithnell34426
I’ve resolved the wobble now, but still don’t understand what I did wrong in the initial machining.

The process I followed was this –

1. Set Flywheel casting (7 inch diameter) on the faceplate to run true (as possib le) against the flywheel areas that will remain unmachined.

2. Skimmed the front edges of the flywheel and the top surface, bored the hub as a series of ops without changing the setup.

3. Turned the flywheel over and set to truth using a DTI on the machined surfaces (1/10 clock).

4. Machined remaining front surface

5. Flywheel wobbles on the crankshaft.

I could understand if the final machined surface didn’t run true, but the whole flywheel had a clear wobble. This process should be fool proof (or Muddle Engineer proof!) shouldn’t it?

As above, I’ve sorted the thing, but don’t understand why the wheel wasn’t right first time.

Regards

Steve
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18 May 2011 at 21:17 #3089
Steve Withnell
Participant
@stevewithnell34426
18 May 2011 at 21:34 #68813
blowlamp
Participant
@blowlamp
Steve.

More than likely a problem with the boring tool, such as a lack of rigidity, wrong clearance angles (which cause the tool to rub), or off centre height, giving ‘bell-mouthing’, etc.

Could also be hard spots in the casting. Something like that anyway.

Martin.
18 May 2011 at 21:46 #68814
ady
Participant
@ady
Probbly a rubbing tool.
18 May 2011 at 22:58 #68819
Ramon Wilson
Participant
@ramonwilson3
Steve,

I would hazard a good guess that when you initially bolted this to the face plate it (the casting) was not quite flat and the bolting distorted it slightly. Your subsequent machining brought the rim true to the bore but once released any stress induced by bolting released – turning it over then may have compounded the problem. Turning a short stub mandrel and holding it on that may be sufficient to take very light cuts to be able to true it up. If it really wobbles theres only one way – Make sure one side is perfectly flat first then set it up again as true as possible and, clamping as lightly as the machining forces will allow, bore out the centre to take a pre turned sleeve (preferably cast iron) Loctite this in still on the face plate then bore and face this off to finished size – reverse as before.

Hope that’s not teaching granny to suck eggs but been there and know how you feel – nothing worse than a wobbling flywheel to maximise irritation as it’s plainly there for all to see

Regards – Ramon
19 May 2011 at 02:56 #68831
Ian S C
Participant
@iansc
I usually carve my flywheels out of hot rolled mild steel plate, but for a casting I would start as you didand face off one side, but then I would turn it over and face the other side, and bore the hub, and withthe jaws on the inside of the rim which makes it so that you can do the outside at the same setting.

At least if the flywheel wobbles you know that things are going round! Ian S C
19 May 2011 at 06:03 #68833
mgj
Participant
@mgj
i’d agree – it was most likely bent in the initial clamping.

One point that is important is only to use 3 clamps.Because then it will, like any 3 legged object, find its own “level” and it is very difficult to bend it. (Unless one overtightens on the spokes)

Edited By mgj on 19/05/2011 06:05:19
19 May 2011 at 09:22 #68842
Gordon W
Participant
@gordonw
Just to be on the safe side, rough machine all over, then leave for a day or two before machining to size. This lets any casting stress out ( or rolling).
19 May 2011 at 17:13 #68862
Steve Withnell
Participant
@stevewithnell34426
Loads of good insights – thanks guys

Steve
19 May 2011 at 17:17 #68866
Steve Withnell
Participant
@stevewithnell34426
As a PS: here is the finished thing, wobble removed!

http://www.youtube.com/watch?v=R6rgZ-7Y3t8

Thanks again

Steve
20 May 2011 at 11:27 #68895
Ian S C
Participant
@iansc
If you clamp the wheel by the spokesit must have adequate packing between the spokes and the faceplate, so that the spokes don’t get bent. Another way is to set up in the chuck nice and square, and bore the hub. Take out of the chuck and mount the wheel on a mandrel, and turn the rest of it between centers. Ian S C
14 May 2014 at 06:31 #152435
Brian John
Participant
@brianjohn93961
Yes, I would have thought that boring the hub would be the first step in machining a flywheel. Are there disadvantages in doing this first ?

NOTE : I did a search for '' maching a flywheel'' but turned up no results.
14 May 2014 at 08:32 #152440
Martin Kyte
Participant
@martinkyte99762
Is the Flywheel keyed to the crankshaft? This can often cant the thing over. I think I would bore the hub when machining the second face with the first now machined face against the faceplate as routine.

regards Martin
14 May 2014 at 09:14 #152441
Brian Wood
Participant
@brianwood45127
Hello Steve,

The one thing you haven't told us is how you corrected the situation having wetted all our appetites!

Please tell us, it might also help others.

Regards Brian
14 May 2014 at 11:17 #152450
Anonymous
This is how I machined my flywheels; the front face of the rim and boss, the outer diameter, and crowning, and the bore all machined at one setting:

Then turned over and the rim and boss faced to final thickness.

Andrew
14 May 2014 at 14:59 #152467
Nigel McBurney 1
Participant
@nigelmcburney1
I have often thought most flywheels have six spokes,and a awful lot of other castings/forgings were six sided yet most faceplates have two master slots set at 90 degrees making it easier for four spoke or square workpieces,though after a century or so Colchester did make six slot face plates by which time nobody was making flywheels. all the above are good comments though I will add some more, beware of workpieces that are stiffer than the faceplate overclamping will distort the faceplate. Holding work on stub mandrels can cause chatter problems as the bore on most flywheels is small relative to diameter. My method is mount three alloy blocks on the faceplate spaced two thirds up each spoke, then use three clamps on the spokes directly over the blocks,on heavier flywheels a further three blocks are mounted equispaced onto the face plate near the rim , three bolts screwed into the blocks are screwed outwards ,like chuck jaws , to just touch the inside of the rim.This helps to keep the flywheel in position and takes any radial strain off the spoke clamps . rough machine bore .o/dia and face ,sometime if the flywheel is spaced away from the faceplate the other face can also be machined .then relax the spoke clamps ,this allows any stress in the casting to be relieved but it remains in position ,held by the three bolts. Then leave as long as possible,tighten the clamps Finish by machining the rims and the bore last, on small wheels the hole should be bored a fewthou undersize and finish by reaming.

Use HSS tools for finish boring ,I have machined a quantity of flywheels from 6ins to 2 ft for steam and ic engines plus refaced rusty stationary engine f/wheels .
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