Topic: crankshaft balancing – Antique Outboard Motor Club,Inc

This topic has 12 replies, 7 voices, and was last updated 6 years, 11 months ago by retro-outboard-guy.

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July 10, 2018 at 3:20 pm #10511
retro-outboard-guy
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Has anyone had any luck balancing a crankshaft on a 60’s big twin? It seems that these engines weren’t built with a decently balanced rotating assembly. I’m curious to see if anyone has had any experience with this? I have several crankshafts and they all seem to settle differently while laying horizontally on a balancing rail.
July 10, 2018 at 5:07 pm #79331
frankr
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Yeah, I tried it. Removed shocking amount of metal. Motor vibrated as much or more than it did before. Conclusion: There is more to it than meets the eye.
July 10, 2018 at 5:11 pm #79332
retro-outboard-guy
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What amazes me is that the same crankshaft is used with the two ring 70’s 40hp engines and that piston and rod assembly is over two ounces heavier than the three ring assemblies of the earlier models. I guess they just weren’t worried about vibration.
July 10, 2018 at 6:05 pm #79336
Anonymous
Maybe the rotating assembly crank rods and pistons were balanced with the flywheel as one unit somehow.
July 10, 2018 at 7:13 pm #79339
frankr
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That’s what I figure. The flywheel is part of the equation.
July 10, 2018 at 7:38 pm #79343
RICHARD A. WHITE
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Lifetime Member
Or the flywheel was actually the part that was modified to balance the entire assembly????

http://www.richardsoutboardtools.com
classicomctools@gmail.com
July 10, 2018 at 8:13 pm #79346
Tubs
Participant
The pulse from ignition also needs to be considered.
It has a considerable effect on single horizontal firing
Motors. The more even the pulses around the rotation
of the crankshaft the less effect in has on vibration.
V-12’s & V-16 being the smoothest even in the 1920’s & 30’s

A "Boathouse Repair" is one that done without having tools or the skills to do it properly.
July 10, 2018 at 8:25 pm #79347
joecb
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A lot more complicated that meets the eye!! talking to an automotive engine designer ( we have several up here around Detroit) and you just begin to understand the complexity of engine "balance".

Joe
July 10, 2018 at 11:05 pm #79354
Tubs
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A "Boathouse Repair" is one that done without having tools or the skills to do it properly.
- This reply was modified 6 years, 7 months ago by Tubs.
- This reply was modified 4 years, 4 months ago by Tubs.
July 11, 2018 at 9:11 am #79372
Pete
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Well since you asked here are engine balance basics, never said it was simple:

https://motochassis.com/Articles/Engine … alance.pdf

How about this method, gotta watch the fingers?

https://www.bing.com/videos/search?q=ou … ORM=VRDGAR
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