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Axle strength - torque converter multiplication

 
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clay
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1972 Chevrolet Nova

PostPosted: Mon Jun 11, 2007 9:21 am    Post subject: Axle strength - torque converter multiplication Reply with quote

Since my buddies Monte Carlo isn't spinning like we though it would, now we are concerned with axle strength. He has Moser street axles right now. If you go to their site they have a calculator to figure torque at the axle. Very basic - crank torque x transmission ratio x rear end ratio x 0.9 (for drivetrain losses I assume) then divide by 2 for per axle torque. Then they claim he has a 200% safety factor. I call BS because from everything I read the torque converter mulitplies torque by 2.5 or so (this is a general figure) which would take care of the 200% safety factor. I mean the converter isn't there for nothing - right. I can't find anybody else that gives a torque rating on their axles to compare with. What does everybody think? Clay
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beersngars
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1948 Chevrolet Coupe

PostPosted: Mon Jun 11, 2007 10:05 am    Post subject: Reply with quote

I used Strange axles, case, ect and they asked me to spell out the specs on the car. I gave them the specs WITH expected upgrades to the engine and trans. The reccomendations were the same as the Moser site as to spline count. The only factor that would change their opinion is if I were to run a trans brake. In that case they would suggest the bigger axle. Strange, as Moser said to stay with the smaller axles if possible for street use.
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Knarley Darley
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PostPosted: Mon Jun 11, 2007 2:56 pm    Post subject: Reply with quote

What spline axles does he have and what is his quarter mile speed/ 60' times. After market axles will take alot even with stock spline counts. Does he have C clip eliminators?
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Big Dave
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PostPosted: Mon Jun 11, 2007 3:40 pm    Post subject: Reply with quote

Also torque converts only multiply engine torque when there is a differential in speed (slipping). The greater the differential the greater the torque multiplication. So at "speed" (above the point of "lock-up" or flash point) the converter slips only a little for a marginal torque enhancement. If you actually have a locking torque converter, like I do, then you get no torque multiplication or slippage once the clutch locks it up.


Big Dave
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af2
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1933 Willys Coupe

PostPosted: Mon Jun 11, 2007 7:25 pm    Post subject: Reply with quote

I may be off but doesn't the trans gear ratio play into the game?
Mine being 2.75 1'st gear it would seem you have to add that into the equation more so than the converter that can't add torque to a given engine.

Just a brain fart. Embarassed
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squeeezer
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1991 Chevrolet Camaro

PostPosted: Mon Jun 11, 2007 9:18 pm    Post subject: Reply with quote

ya
multiply gear (depending on which trans gear) and rear end gear
sometimes a transfer case


i wouldnt even begin to know how to add the multiplication of a torque converter?
how would you find out?

i would think ultimately it would be better to lock up the torque converter

which is better
1 the multiplication
or
2 the 1:1 ratio like a clutch
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af2
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1933 Willys Coupe

PostPosted: Mon Jun 11, 2007 9:51 pm    Post subject: Reply with quote

squeeezer wrote:


i wouldnt even begin to know how to add the multiplication of a torque converter?
how would you find out?

i would think ultimately it would be better to lock up the torque converter


The converter can't increase multiplication because it is part on the crank when bolted. I can only vision slip or stall at that point. Gear reduction is a different thing though. That's why I posted the ratio.
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clay
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1972 Chevrolet Nova

PostPosted: Mon Jun 11, 2007 11:52 pm    Post subject: Reply with quote

I think the converter does multiply torque - but does so on a continously changing basis due to the difference between input and output speed (exactly like Big Dave said). At the hit of the throttle, engine rpm will go to 3000 for example (converter input) but the input shaft of the transmission isn't moving (converter output). At this instant is where I believe maximum multiplication occurs and decreases as input and output rpm get closer to each other until it basically reaches a 1:1 ratio. Yes transmission ratio does play into it as well as rear end ratio which are fairly straightforward, just the converter thing is sort of interesting. He is using Moser street series axles which still use the "C" clips and are 30 spline. So far it has gone a 1.51 60' time at a weight of 4200 lbs. It has gone a 11.42 in the 1/4, but given the latest 1/8 mile pass, it could easily be a tenth or two faster. Clay
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af2
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1933 Willys Coupe

PostPosted: Tue Jun 12, 2007 12:25 am    Post subject: Reply with quote

clay wrote:
I think the converter does multiply torque - but does so on a continously changing basis due to the difference between input and output speed (exactly like Big Dave said). At the hit of the throttle, engine rpm will go to 3000 for example (converter input) but the input shaft of the transmission isn't moving (converter output). At this instant is where I believe maximum multiplication occurs and decreases as input and output rpm get closer to each other until it basically reaches a 1:1 ratio. Yes transmission ratio does play into it as well as rear end ratio which are fairly straightforward, just the converter thing is sort of interesting. He is using Moser street series axles which still use the "C" clips and are 30 spline. So far it has gone a 1.51 60' time at a weight of 4200 lbs. It has gone a 11.42 in the 1/4, but given the latest 1/8 mile pass, it could easily be a tenth or two faster. Clay


You answered you're own question!
The transmission and drive line are not going to see the converter till it is locked or so so. Therefore the amount of torque to the rear end is the same as the engine nothing more or less!!!
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clay
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1972 Chevrolet Nova

PostPosted: Tue Jun 12, 2007 8:44 am    Post subject: Reply with quote

I'm just mainly talking about the first few feet of the run where the torque converter is really doing it's thing since input shaft speed is pretty slow and the engine is theorectically at it's peak torque rpm. After that, it's decreasing multiplication and there wouldn't be a problem. Clay
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wagon train
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1983 Mercury Capri

PostPosted: Wed Jun 13, 2007 12:13 am    Post subject: Reply with quote

I ran Moser 31 spline 9" axles for about a year till I could afford Mark Williams 40's. 2985lbs. 1.25 60ft.
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clay
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1972 Chevrolet Nova

PostPosted: Wed Jun 13, 2007 12:23 pm    Post subject: Reply with quote

I really think they are stronger than I think they are - just that it is their street series is really what has me even questioning - and I just want to know about the torque conveter too. I'm just trying to get all the information I can since he spent sooo much time on body panel fitment, all body gaps, paint, etc. and I would hate to see a quarter get torn off and have to fix that. Clay
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af2
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1933 Willys Coupe

PostPosted: Wed Jun 13, 2007 1:07 pm    Post subject: Reply with quote

Clay, I would eliminate the C-clips for sure. In fact I believe any thing Quicker than 12.99 must have eliminators.
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