All -
Finally got some time to work on my own projects. Sized, cleaned, and weighed all the flywheel components to my WLA. Put a bobweight on the flywheels and matched them to to the lightest. Bobweight weighed in at 750.5 grams. I am using NOS 0.010" OS pistons. Did some reverse calculating and came up with a balance factor of 44% for these wheels. Just thought I'd post this info for anyone who's curious.
Jack
1942 WLA balance factor
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Jack_Hester
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Cotten
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Re: 1942 WLA balance factor
Geez that's low!
But that's in the ballpark of earlier vintage flatties (as per Slocombe: 43%).
But road conditions and riding habits have changed,...I think? (Noteing that 60% is the accepted figure for the last decade or two.)
Thank gawd a v-twin cannot ever really be out of balance!
PS: Maybe I do not understand exactly,...you assembled the wheels and rods, then added weight to the wristpin ends until they balanced, and then calculated...right?
But that's in the ballpark of earlier vintage flatties (as per Slocombe: 43%).
But road conditions and riding habits have changed,...I think? (Noteing that 60% is the accepted figure for the last decade or two.)
Thank gawd a v-twin cannot ever really be out of balance!
PS: Maybe I do not understand exactly,...you assembled the wheels and rods, then added weight to the wristpin ends until they balanced, and then calculated...right?
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Jack_Hester
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Re: 1942 WLA balance factor
Cotton -
First I put a bobweight on each flywheel, and added/subtracted weight, until they nulled. There was a slight mismatch from one wheel to the other. So, I balanced the heavy one to match the light one. Only 2 or 3 grams. Then, I went through the normal procedure of weighing all the components, as if doing a normal balance. Then, rather than calculating from a given balance factor (to find the bobweight), I used the weights to reverse calculate the actual factor, from a measured bobweight. This is only reversing the last few steps of the balance procedure for individual wheels. Maybe I haven't confused you too much on my method. I have a small computer program that I wrote to enter all the weights and calculate the bobweight value. I'm inspired to add a selection to it just for calculating the unknown balance factor of flywheels, like I did on this one. The math is simple. Just keeping up with all the data is the kicker.
Jack
First I put a bobweight on each flywheel, and added/subtracted weight, until they nulled. There was a slight mismatch from one wheel to the other. So, I balanced the heavy one to match the light one. Only 2 or 3 grams. Then, I went through the normal procedure of weighing all the components, as if doing a normal balance. Then, rather than calculating from a given balance factor (to find the bobweight), I used the weights to reverse calculate the actual factor, from a measured bobweight. This is only reversing the last few steps of the balance procedure for individual wheels. Maybe I haven't confused you too much on my method. I have a small computer program that I wrote to enter all the weights and calculate the bobweight value. I'm inspired to add a selection to it just for calculating the unknown balance factor of flywheels, like I did on this one. The math is simple. Just keeping up with all the data is the kicker.
Jack
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Cotten
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Re: 1942 WLA balance factor
Jack!
I took a peek at your program when you posted it to the WLA yahoo List.
Two or three grams of bobweight difference between wheels seems like a fart in a hailstorm, particularly since the bobweight 'contains' a lot of rotating mass as well.
I can see the benefit of bobbing individual wheels if one must start with some that are raw, or radically drilled previously, but when a re-built set only needs correcting (usually just for peace of mind), using bobs is a lot of extra hassle!
I have back-calculated big-twins and Chiefs, but never a HD45; Have you double-checked your factors after trueing up the crank assembly?
I took a peek at your program when you posted it to the WLA yahoo List.
Two or three grams of bobweight difference between wheels seems like a fart in a hailstorm, particularly since the bobweight 'contains' a lot of rotating mass as well.
I can see the benefit of bobbing individual wheels if one must start with some that are raw, or radically drilled previously, but when a re-built set only needs correcting (usually just for peace of mind), using bobs is a lot of extra hassle!
I have back-calculated big-twins and Chiefs, but never a HD45; Have you double-checked your factors after trueing up the crank assembly?
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Jack_Hester
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Re: 1942 WLA balance factor
Cotton -
You know, I almost left it as is, as that amount of difference really means nothing. But, yesterday (Memorial Day), I decided that that was my day to work on my projects. And, I was enjoying the moment. So, I just matched them up, as I had all the time for myself.
I've never attempted to do a combined-wheel balance. Individual wheels are all that I've ever done. The only reason I went to the trouble on mine, is that I wanted to know the balance factor on a 45. Now, I need to try another, just to compare. Otherwise, as these wheels are mates, I would have never gone to the trouble. I have several sets of wheels that I bought, that were not assembled. I will definitely check them against each corresponding mate.
My wheels are unassembled, as I jumped to another project, after getting all the weights written down. Now that I have some ballpark idea of the bobweight used, I will check a couple of other sets. Don't know when that will be, as I'm back on the priority stuff. I'll keep you informed as to my findings.
Cotton -
You have mail, in reference to Flywheel Balancing program update.
Just checked another set of flywheels this afternoon, and they came up with a 50% balance factor. Will check one more set tomorrow evening.
Jack
You know, I almost left it as is, as that amount of difference really means nothing. But, yesterday (Memorial Day), I decided that that was my day to work on my projects. And, I was enjoying the moment. So, I just matched them up, as I had all the time for myself.
I've never attempted to do a combined-wheel balance. Individual wheels are all that I've ever done. The only reason I went to the trouble on mine, is that I wanted to know the balance factor on a 45. Now, I need to try another, just to compare. Otherwise, as these wheels are mates, I would have never gone to the trouble. I have several sets of wheels that I bought, that were not assembled. I will definitely check them against each corresponding mate.
My wheels are unassembled, as I jumped to another project, after getting all the weights written down. Now that I have some ballpark idea of the bobweight used, I will check a couple of other sets. Don't know when that will be, as I'm back on the priority stuff. I'll keep you informed as to my findings.
Cotton -
You have mail, in reference to Flywheel Balancing program update.
Just checked another set of flywheels this afternoon, and they came up with a 50% balance factor. Will check one more set tomorrow evening.
Jack