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Antique Engine Archives All archived posts from 1999 to 2004 when SmokStak was on EnginAds. This is a read-only board.

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Casting and machining a flywheel


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  #1  
Old 08-22-2004, 08:12:17 PM
Chris Kirk
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Default Casting and machining a flywheel

Thanks to everyone for their responses re: repairing the Bulldog flywheel. I'll be putting an ad for one in GEM, but also looking into getting one recast, and I have a few questions.

1) What is the best way/material to use to build up the face of the rim to account for shrinkage? According to Emmanuel King at Cattail, cast iron will shink 1/8" per foot from the original flywheel, so I will have to add on about 1/4" to the outside of the rim to make the flywheel the same diameter as the original. I've heard that you can use bondo, but there's the risk of not getting the thickness even all around the rim, and having a new flywheel that looks slightly out of round.

2) Does anyone know of a machine shop in or around the Northeast who can bore the hole for the crank (2"), cut a keyway, and machine the bolt hole for the governor weight...for a reasonable price? I want to find someplace that has experience with old engines and flywheels...the hole must be perfectly centered, or it will be out of round and the engine will vibrate badly.

3) Is there anything else I should be aware of or watch out for if I end up having this flywheel recast?

Thanks...

Chris
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  #2  
Old 08-22-2004, 09:16:55 PM
Bill Schaller
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Default Re: Casting and machining a flywheel

your statement "the hole must be perfectly centered, or it will be out of round and the engine will vibrate badly." is incorrect. you bore the hole, and then the outer surface of the flywheel is machined. and then you balance the flywheel.
  #3  
Old 08-22-2004, 09:49:24 PM
Mac Leod
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Default Re: Casting and machining a flywheel

I think it would be worth while to ask about the type of cast iron used and the annealing process.

Just a thought

Mac Leod
  #4  
Old 08-22-2004, 10:07:03 PM
Chris Kirk
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Default Re: Casting and machining a flywheel

Bill -

Thanks for the information. I only made that comment because the face of both flywheels has not been machined...they are totally unfinished rough castings. How could they have been balanced without machining the face?

Thanks...

Chris
  #5  
Old 08-22-2004, 10:36:22 PM
Bill Schaller
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Default Re: Casting and machining a flywheel

Chris, if the flywheel faces have not been machined, then I was wrong. anyhow, they usually drill some homes on the rim to get it all balanced.
  #6  
Old 08-22-2004, 10:52:41 PM
Chris Witt
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Default Re: Casting and machining a flywheel

A1) The best would be to have a complete pattern made. Most foundries don’t want to use a casting as a pattern. The foundry must have draft and smooth surface to get the pattern out of the sand. That aside you could add the difference by applying small strips of wood to the outside diameter. If I was to add material with bondo to the outside I would make a wood form to “squish” the proper size using shims. A squish is a technical term in patternmaking. Being that you asked about using the existing casting as a pattern I wouldn’t mess with adding the stock to the outside to make up the shrink factor. The rest of the flywheel isn’t being changed. A2) Anyone with a lathe large enough could bore the hole and it will be centered. Balancing the flywheel can be accomplished by drilling small holes on the rim of the flywheel to remove stock to balanced. I’m far from northeast so I am not familiar with north east foundries. I have heard about an Amish guy near Pittsburgh. A) Someone mentioned the type of cast iron. There are basically two “types” of cast iron. Gray iron and ductile iron. There are many different grades for each. I would suggest a grade 30 gray iron. That would be 30,000 tensile strength per inch. There shouldn’t be any annealing for class 30. If a foundry would tell you that, they don’t know what they are doing.
  #7  
Old 08-22-2004, 11:24:35 PM
Randy Hart
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Default Re: Casting and machining a flywheel

Chris, If you go the bondo build up road, go more than the 1/4" and let the shop turn it to size.. and for the thickness problem I would build it up and let it cure and remove the conn. rod and power the other flywheel with a SLOW running power source and belt, set up a rigid tool rest and turn the surface with a wood lathe tool.. If the foundry requires a taper then turn a taper for release.. I have used bondo several times for foundry build up and it is nice to work with and will stand the process.. Find your foundry and see what they want before you get busy.. Randy Hart Ohio
  #8  
Old 08-23-2004, 10:19:27 PM
Roland Finkenbinder
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Default Re: Casting and machining a flywheel

The bolt holes for a split hub or bolted hub may need to be cast in with a core. To drill them afterwards may not work if the spokes are in the way. I like to core the hub and use a boring bar to finish it. Depending on the size of the hub, you may or may not have problems with shrinkage without a core. The larger mass of metal cools slower than the thin spokes. The cooler areas pull metal from the molten areas as they solidify. The core helps to eliminate some of that mass. Stay at least 1/4"--3/8" or more smaller than your finished bore size with the core size, just make sure it is large enough to use a good size boring bar.I am definitly not an expert, these are just some things I have encountered when casting flywheels.
 

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