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To balance or not?

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Morris

Morris

Yoda
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I am carting everything off to the machine shop tomorrow. So I am wondering, is balancing the crank/pistons a necessity or a luxury? The price makes me think it's a luxury!
 
What's the price? I've always seen it as good insurance, but I sort-of give the engine to the builder and say 'do it up' and cry later :p
 
I wouldn't buid an engine without balancing all the moving parts.
 
& I'm talking from harmonic balancer to flywheel
 
Actually, there isn't a harmonic balancer on 1500's ... It's shocking, I know!
 
Matt - I know, I was just amplifying that EVERY rotating part needs to be balanced!
 
Balance it, the cost is nominal compared to the benefit. It should be between $100-2$50 based on the amount of work that is being done, a small investment.

I know that you want to rev her....
 
I take everything that rotates to the machine shop...& I ask them to balance all the pistons one to another, all the rods one to another, end-to-end & then balance the reciprocating system...& go back & make any changes needed to the 'dry' balancing

but, if they're a good shop, they'll know what to do
 
Yep, excellent idea. In fact the little four cyl. engines need it to run well and smooth. Don't forget the flywheel.
 
I'd do it.

Any job worth doing is worth over-doing.... /ubbthreads/images/graemlins/crazy.gif
 
Soup to nuts. Balance it all from crank pulley to the entire clutch assembly.
 
Some things like pistons are weighed, like to 1/4 gram. other things are spun on a lathe like thing.
Parts are drilled or ground to take weight off.
 
Balance EVERYTHING wot spins. It's a really cheap way to insure a much longer engine life. Can't recall the numbers but half an ounce of unbalanced load increases exponentially with increased RPM. It gets into HUNDREDS of pounds up at the high end. I don't understand why they ALL don't just *explode* the first time they see redline! Magic, I guess... /ubbthreads/images/graemlins/wink.gif
 
They start by static balancing (matching the weight) of piston/con-rod assemblies. This is usually done by removing steel from the con-rods. The rotating components, starting with the crank, are rotated at high-speed in a cradle instrumented with accelerometers. The accelerometers measure the imbalance at a given RPM while encoders determine at what angle of rotation the imbalance occurred. The angular locations are noted and the counterweights of the crank are drilled to remove material until the imbalance is removed. Other components like flywheels and pulleys can be balanced by themselves using mounting mandrels or added to the crankshaft and balanced as an assembly. In general, the best results are obtained on rotating equipment balanced as an assembly rather than as individual components. I've never watched an automotive machinist balance an engine to see whether they balance assemblies or discrete components. I do know that with the Mini (which has a unique flywheel) the only way to balance the clutch assembly is mounted on the crank.
 
I just love all those big words, whoot.

Instrumented, accelerometers, encoders. imbalance and such. /ubbthreads/images/graemlins/smile.gif

Really though, very well put.

Note to self: Read again so I can use it on local folks that are easly impressed, Hehe.
 
Yeah, Jack... walk into the local Niceville machine shop and ask 'em to show ya how the accelerometer onna crank balancin' machine works... I'll jus' wait outside. With the engine runnin'. /ubbthreads/images/graemlins/hammer.gif

...now where's that durn'd beer cooler....
 
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