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Old 11-18-2007, 06:14 PM
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I wanna try and knife edge my crank

I have been searching for info on the net and have come across alot of good stuff. I have a spare kawasaki crankshaft from a dirt bike that i want to experiment with.

I was wondering if there are any machinst out here that have done their own crank shaft work.

I would like to ask some specific questions in regards to the machining process and what was done to balance the crank afterwards. I am more concerned with balancing the crankshaft, how to properly straighten the crankshaft and if the crank needs to be heat treated after the machine work has been completed.

Are there any books on the knife edging process? any tutorials or something online that i could read?

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Old 11-18-2007, 07:32 PM
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I wanna try and knife edge my crank

well i've done several 2000 and 2300 pinto engines
it's not hard
you got some old bearings you can tape them in place to protect bearing surfaces .
grind slow and not to much heat will build up to hurt it .
i've cut most all the weights off and have them balanced at speed shop after doing the job.
polish the hole crank works well also .
you might as well polish the block to .
you got a good oil baffle screen plate ,deeper pan and run less oil .
polish your rods to ,just get all balanced ,run longer rods with shorter deck height pistons ,that changes the weight of the total throw .
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Old 11-19-2007, 09:38 AM
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Quote:
Originally Posted by burnt olds
well i've done several 2000 and 2300 pinto engines
it's not hard
you got some old bearings you can tape them in place to protect bearing surfaces .
grind slow and not to much heat will build up to hurt it .
i've cut most all the weights off and have them balanced at speed shop after doing the job.
polish the hole crank works well also .
you might as well polish the block to .
you got a good oil baffle screen plate ,deeper pan and run less oil .
polish your rods to ,just get all balanced ,run longer rods with shorter deck height pistons ,that changes the weight of the total throw .
Why were you unable to balance the crank yourself?
How did you grind off the material to do the knife edge work?
Why would i need to protect the bearing areas if i don't plan to machine them?
How do they balance the crankshaft?
How do they polish the entire crank?
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Old 11-19-2007, 11:32 AM
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I wanna try and knife edge my crank

used a big 1/2 inch grinder
the bearings protect the journals on cranks your going to use.
polished with sand paper wheels on hand held end buffer .
machine shop has a balancer ,you cant rent them you know .
it's a mess but get at it ,it's not hard .
i used a gas chop saw and cut the weights off some, use cutting coolant
to keep the heat down.
used 5.7 rods and short deck pistons and drill them down for less weight and balance them with scales yourself , have you a rod jig to balance them also .
i leave the expensive tools to the machine shops ,boring and crank grinding lathes past my budget.
the shop i use say that my grinding and polish work is a better than they do job ,they agree with it's time and messy type of job.

i ran dirt track and had the shift light set at 9 grand as a to keep up with to make consistent lap times.
broke one fan blade and cut the other side and the broke side even ,to balance out the fan.
3:73 welded rear with a 7-14 second gear transmission
586 roller cam in a 2000 pinto motor humming 9 grand for two years and never a bit of trouble.
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Old 11-19-2007, 07:00 PM
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Just an opinion here......... as usual.

I trust you are dealing with a four stroke engine? Knife edging a two stroke will reduce power.

In a dirt bike application, the oil is very much all over the place and not necessarily in the direct path of the crankshaft unless at moderately consistent positive G's at an "X" time factor.

If your talking one or two cylinders, the knife edging benefit is negligible in terms of performance unless you're expecting an advantage in the WR Square factor - the acceleration of a rotating mass, which will immediately be offset by an increase in imbalance and potential relational association of natural frequencies, though unlikely.

Unless the connecting rod (or rods) is a two piece design like the average Chevrolet, you won't be able to properly balance the reciprocating mass anyway..... so why bother?
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Old 11-19-2007, 07:21 PM
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Quote:
Originally Posted by Dugg
Just an opinion here......... as usual.

I trust you are dealing with a four stroke engine? Knife edging a two stroke will reduce power.

In a dirt bike application, the oil is very much all over the place and not necessarily in the direct path of the crankshaft unless at moderately consistent positive G's at an "X" time factor.

If your talking one or two cylinders, the knife edging benefit is negligible in terms of performance unless you're expecting an advantage in the WR Square factor - the acceleration of a rotating mass, which will immediately be offset by an increase in imbalance and potential relational association of natural frequencies, though unlikely.

Unless the connecting rod (or rods) is a two piece design like the average Chevrolet, you won't be able to properly balance the reciprocating mass anyway..... so why bother?
I was referring to practicing with a dirt bike crank because it was a spare item. i wasn't going to knife edge the crank and put it into my car. The dirt bike and motorcycle cranks i have are just spare parts that have been sitting, so i thought i could do my experimenting with these.

I want to try and mill the crank shaft instead of grinding it. I am concerned about the hardness of the material because it is heat treated. I am actually looking into what temperature would be needed to anneal the crank shaft hen i could heat reat it again for the added hardness. Im lucky because i have access to ovens that would reach heat treating temperatures.

I was trying to gather information on the machine work because i would personally like to AVOID annealing the crankshaft just so that i can machine it.
I know grinding is a nice process but I have to give machining the materal a try first. Ill update everyone once i see what happens
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Old 05-12-2008, 07:09 PM
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Trying To Revive

I would like to brig this discussion back to life.

I have some new questions in regards to balancing the crank in general and after the machine work has been done:

There are two counterweightss per connecting rod setup. Are the total masses of the counterweights equal to the weight of the connecting rod setup? (it doesn't seem like it)

How are crankshafts currently being blanaced. Even without knife edging the crank has to be balanced. I want to know I need to hold the crank to properly balance the counterweights.

I am only experimenting with the kinfe edging process. My crankshaft I am using is only a practice peice that is not usable. It is form a two cylinder motorcycle.
I want to be able to kinfe edge, or do a pedelum edge on the counter weights, then be able to rebalance the shaft. I am looking for experienced advice, from engineers, or machinist or some one who knows how the counterweights mass are chosen

Once, it is all said and done. I''m going to make a lamp from the crannk shaft.
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