Author Topic: Modifying a Counterweighted Crankshaft  (Read 1003 times)

Offline oceanrhode

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Modifying a Counterweighted Crankshaft
« on: October 21, 2020, 07:49:48 AM »
I am in the research phase of my 1/2 engine build. I only have a case. But ordered some 1/2 engine plans and can't seem to find an answer on how to properly modify an existing shaft that is counterweighted. Plenty of information on welding counterweights on existing cranks but I plan on buying a new counterweighted crank from cbperformance. Do you leave the last crank throw on or do you cut it off completely? I have attached two photos that show the differences.

Offline Theodore

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Re: Modifying a Counterweighted Crankshaft
« Reply #1 on: October 24, 2020, 07:48:20 AM »
cut it off, then send it to Casler to weld on counterweights and balance.
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Offline oceanrhode

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Re: Modifying a Counterweighted Crankshaft
« Reply #2 on: October 24, 2020, 08:52:01 AM »
That's great and all but as soon as Casler stops doing this the question will remain. Do you leave the last counterweighted throw on or do you not. I've seen both being done. Better Half Plans and Great Plains plans shows welding counter weights on to a stock crank, and bolting on a plate on the back, respectively. Can't find plans showing the counterweight approach despite obviously seeing it done in other builds. Where are those plans?

Offline Dan_

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Re: Modifying a Counterweighted Crankshaft
« Reply #3 on: October 24, 2020, 03:04:40 PM »
You have 3 phone calls to make... Leonard Milholland, Scott Casler, and whoever took over at Great Plains from Steve Bennett.

Please let us know what you find out.


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Offline Kamcoman77

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Re: Modifying a Counterweighted Crankshaft
« Reply #4 on: October 24, 2020, 06:37:29 PM »
The rear counterweight is partially cut off when Scott Casler does the modifications to a SCAT stroker crank. My understanding is he cuts a pre-planned amount off and then cuts off a little more if his balancing machine indicates it's needed. Even so, there is removeable counterweight that bolts to the rear of the prop hub to complete the balancing. The weight and cut of the external counterweight varies with the stroke of the crankshaft.

Offline Suomelainen

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Re: Modifying a Counterweighted Crankshaft
« Reply #5 on: November 23, 2020, 06:05:03 AM »
Got any new info on this?

Offline oceanrhode

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Re: Modifying a Counterweighted Crankshaft
« Reply #6 on: November 23, 2020, 09:00:45 AM »
I spoke to Cassler on the phone and he kinda verified what was mentioned above. He leaves it on and then adds/subtracts depending on what is needed. He said leaving the extra throw on is not enough to correctly balance once cut in half. He adds material then, say you were using a magneto, he taps in some holes so you can mount that extra piece to engage with the magneto.

It seems some older plans just bolt on a balance because it may be easier to add the entire new counterweight than to work with a partial throw. Hopefully that makes sense.

 

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