Counterweight opinions

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Michael Paul
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Counterweight opinions

Post by Michael Paul » Sun Sep 22, 2019 10:54 am

Good morning!
I'm in the process of assembling my early engine with a 26/27 crankshaft. After reading all of the posts about broken crankshafts, I was interested in opinions about adding counter weights. Do you think it would help protect the crank, in other words less stress?

Have a great day!
Michael Paul

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Henry K. Lee
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Re: Counterweight opinions

Post by Henry K. Lee » Sun Sep 22, 2019 11:00 am

Balancing is always your friend, using Dunn weights or the likes of, we have been doing for many years with excellent results.

Just my $0.03 worth,

Hank


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Re: Counterweight opinions

Post by modernbeat » Sun Sep 22, 2019 11:15 am

This is one of the reasons the Scat cranks are so popular. New, full diameter journals, and counterbalanced cheeks.
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henryford2
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Re: Counterweight opinions

Post by henryford2 » Sun Sep 22, 2019 11:59 am

From past experience the 26/27 requires a little more work to correctly "fit" the counter weights to the crank so as to not "tweak" or bend the crank increasing the runout at the flange. Just my humble opinion.
Always looking for vintage Whizzer engines, bikes & parts. What do you have?

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Mark Gregush
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Re: Counterweight opinions

Post by Mark Gregush » Sun Sep 22, 2019 1:54 pm

If you have not done so, I suggest googling "mtfca; dunn counter weights" or try; "mtfca; counter weights". While using "counter weights" or "counterweights" gets about the same results, there has been a lot posted so lots of reading.
I know the voices aren't real but damn they have some good ideas! :shock:

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Re: Counterweight opinions

Post by Scott_Conger » Sun Sep 22, 2019 7:08 pm

I do not have a car fitted with such, but highly suspect that the 2 piece transmission shaft offered by one of our Forum participants will go as far or farther than almost any other thing you can do for your crankshaft with respect to keeping it in one piece.

It is a significant undertaking to get the 4th main in line with the block...a task which I believe is either misunderstood or ignored by many builders. This little device appears to be a remarkable improvement in design which allows the crank to run unfettered to a flailing transmission.

I am not in any way associated with this product, but feel that in a discussion regarding trying to eliminate breakage of a crank shaft, the stresses that can be imparted to a crankshaft by a transmission that is improperly aligned are significant and anyone doing this work should be aware of that. Anything that can relieve the crank of stress should be a valid option for discussion.

FWIW
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Re: Counterweight opinions

Post by Les Schubert » Sun Sep 22, 2019 7:23 pm

Scott
Thank you for the kind words regarding the “floating transmission shaft “(my invention)
I also believe in counterweights for the T crank. But I will qualify about this, for people like me with the patience and skills, bolt on Dunn weights are a great cheap solution. But I recognize that I am probably a exception. Like for me using a A crank is a good cheap solution.
For the others the Scat crank probably makes sense.
So I will respect whatever way you go (as long as you respect my methods too).
Either way the floating transmission shaft has proven beneficial!


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Michael Paul
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Re: Counterweight opinions

Post by Michael Paul » Sun Sep 22, 2019 7:32 pm

Thanks for the input. The 3 piece transmission shaft sounds like a great idea...

Erik Barrett did the Babbitt work, as part of the job he straightens the pan so the fourth main lines up perfectly. In fact he won't do your bearing unless he straightens your pan!
Great machinist, I highly recommend him!

I guess I'm being a little to cautious. I plan on driving the wheels off the car once it's back on the road. Open valve motors are hard to come by, and expensive to replace. I have a running 1916 engine, maybe I should use that for my driver, and save the early one for the dog and pony show weekends.

Thanks Mike


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Re: Counterweight opinions

Post by Les Schubert » Sun Sep 22, 2019 8:08 pm

Some years ago a guy did a great study on how much the back of the transmission moved around from the force applied to the transmission pedals. He measured significant deflection (irrespective of the pan being straightened (which I fully endorse))relative to the engine block.


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Re: Counterweight opinions

Post by Burger in Spokane » Sun Sep 22, 2019 8:31 pm

I ran a SCAT, not because I was worried about breaking a crank, but because I wanted
a well balanced, smooth running T engine. Henry designed and built these things for
bad roads, or no roads at all. The worst roads we drive on today are leaps and bounds
better than anything these things drove on when new. As such, the running of any steady,
high rpm driving just never happened. Today, we need to consider this change when running
and building a T engine, IF you plan to drive it much out side of parade speeds.
More people are doing it today than ever before !


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Re: Counterweight opinions

Post by Scott_Conger » Mon Sep 23, 2019 4:03 pm

I'd like to restate my comment above about the difficulty to align the 4th main (and am surprised no one corrected me). It isn't so much the 4th main alignment (with the straightened pan) as I MEANT to say "getting the transmission output shaft axis aligned with the crank axis, and ensuring all of the drums rotate concentrically about that axis". Lots more words, but is really what I meant. Les' 2 piece shaft goes a long way toward taking out the stress that mis-aligned parts can induce.

And Les, I am with you. My first experience with Dunn counterweights scared the daylights out of me just out of general principle, but they do work...I doubt that many folks using them actually follow up with balancing them, though they should be. The engine I saw with them was a very smooth performer.

Still with regards to broken crankshafts, anything that reduces stress, like Les' transmission shaft, or is designed to minimize the deleterious effects of stress like the SCAT crank, any of these options is a good choice. It's just about money $$.
Scott Conger

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Re: Counterweight opinions

Post by A Whiteman » Mon Sep 23, 2019 5:53 pm

IMHO, probably the major cause of broken cranks in a 'non-souped up' engine is a misaligned 4th main and then line boring of mains not properly done 'in line' (it is scary how many 'professionals' can't get that right!).
If all mains don't line up 'square' the crank flexes just a bit = stress fractures = broken crank. Balancing can help but won't overcome the alignment issues.

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