The Ford Barn

Paul_nz · 01-21-2012, 03:55 PM

I have a counter-weighted crankshaft that I need to send off to the balancer, is it spun up at low revolutions or high revolutions and balanced at a given rpm. Is there an optimum rpm that I stipulate?

Kohnke Rebabbitting · 01-21-2012, 04:32 PM

Quote:

Originally Posted by Paul_nz

I have a counter-weighted crankshaft that I need to send off to the balancer, is it spun up at low revolutions or high revolutions and balanced at a given rpm. Is there an optimum rpm that I stipulate?

The weights we put on when I get time,we spin ours at 2100. Herm.

Pete · 01-21-2012, 04:37 PM

Anything spun up in a balancer will have a resonant frequency determined by the weight of the part and the balancer setup. The part is normally balanced at the primary resonant frequency. It is spun up slightly above this and let come down by itself. The unbalance is read as it goes down through the resonant point.
On most "A" crankshafts this point will be around 200 to 400 rpm.
The rest of the crank assembly (rods, pistons,flywheel clutch etc) needs to be balanced also.
When done, the assembly will be in as good balance over the whole rpm range
as the design of the engine will permit.

J and M Machine · 01-21-2012, 05:06 PM

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We balance the crankshafts at 500 RPM per the manufacturer of our machine. This rpm has worked for the model A/T engines as well as modern v8's and all other engines we have balanced.

We've updated to a new CWT machine but the RPM still is 500.

I would also recommend balancing the clutch and flywheel as a unit and then balance the rods end for end and also balance the pistons so you get the best result of the engine rather than just balancing the crank.
http://www.jandm-machine.com/balancing.html

01-21-2012, 03:55 PM	#1
Paul_nz Member Join Date: Jul 2010 Location: New Zealand Posts: 66	Balancing the Model A Crankshaft I have a counter-weighted crankshaft that I need to send off to the balancer, is it spun up at low revolutions or high revolutions and balanced at a given rpm. Is there an optimum rpm that I stipulate?

01-21-2012, 04:37 PM	#3
Pete Senior Member Join Date: May 2010 Location: Wa. Posts: 5,415	Re: Balancing the Model A Crankshaft Anything spun up in a balancer will have a resonant frequency determined by the weight of the part and the balancer setup. The part is normally balanced at the primary resonant frequency. It is spun up slightly above this and let come down by itself. The unbalance is read as it goes down through the resonant point. On most "A" crankshafts this point will be around 200 to 400 rpm. The rest of the crank assembly (rods, pistons,flywheel clutch etc) needs to be balanced also. When done, the assembly will be in as good balance over the whole rpm range as the design of the engine will permit.

01-21-2012, 05:06 PM	#4
J and M Machine Senior Member Join Date: Oct 2010 Location: 40 Mt.Vickery Rd. Southborough,MA 508-460-0733 Posts: 352	Re: Balancing the Model A Crankshaft Sponsored Links (Register now to hide all advertisements) We balance the crankshafts at 500 RPM per the manufacturer of our machine. This rpm has worked for the model A/T engines as well as modern v8's and all other engines we have balanced. We've updated to a new CWT machine but the RPM still is 500. I would also recommend balancing the clutch and flywheel as a unit and then balance the rods end for end and also balance the pistons so you get the best result of the engine rather than just balancing the crank. http://www.jandm-machine.com/balancing.html