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Old 28 Apr 2006, 05:56 (Ref:1596696)   #1
johnny yuma
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Power Loss At Universal Joint

Due to firewall,transmission tunnel etc. constraints [laziness?] I have about a 5 degrees angle [off a straight line]at the front uni in a rwd live rear axle sedan with engine swap. Am I losing much power--is it worth chasing ??
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Old 28 Apr 2006, 06:57 (Ref:1596712)   #2
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graham bahr should be qualifying in the top 10 on the gridgraham bahr should be qualifying in the top 10 on the grid
no you will hardly loose anything, infact u/j s should not run perfectly in line or they wear permaturely
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Old 28 Apr 2006, 12:19 (Ref:1596884)   #3
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Originally Posted by graham bahr
no you will hardly loose anything, infact u/j s should not run perfectly in line or they wear permaturely
thanks graham one less niggle.
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Old 28 Apr 2006, 13:31 (Ref:1596950)   #4
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On the subject of losses is there any equation to calculate the losses of power when angling driveshafts which use tripod joints?

Is it to much of a worry compared to CofG reduction. This is in the case of a single seater
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Old 30 Apr 2006, 01:44 (Ref:1597873)   #5
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Power losses due to taking a round about way to the road will surprise you. the most efficient is is the common chain driven motorcycle because the engine rotating in tandem with driven wheel, same for the Morris 750 with transverse engine. An average car ft engine rear wheel drive will suffer about a 40% loss. The same set up on a buss with an extra long drive shaft will be closer to 60%. DON'T BELIEVE IT? prove it to yourself: take an impact wrench or a torque wrench set at say a 40 ft pound setting and tighten a lug nut, then with a torque wrench, see haw much is required to remove it. then do the same with longer extension, the add a U-joint, then another extension and hold it at an angle. You will be amazed at the difference.
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Old 30 Apr 2006, 08:20 (Ref:1597990)   #6
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yes norman i see what your saying but the question was about a slight 5degree angle (which is how they are designed to run), your compairing a short direct straight drive without a U/J to one with a much longer drive with a u/j, not to mention the u/j s in a socket set arn't designed to be free running not being on needle rollers
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Old 30 Apr 2006, 14:38 (Ref:1598160)   #7
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Originally Posted by graham bahr
yes norman i see what your saying but the question was about a slight 5degree angle (which is how they are designed to run), your compairing a short direct straight drive without a U/J to one with a much longer drive with a u/j, not to mention the u/j s in a socket set arn't designed to be free running not being on needle rollers

True, even so it's a item that is often missed. BTW are they using any aluminum or carbon fiber drive shafts over there?
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Old 30 Apr 2006, 15:54 (Ref:1598195)   #8
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steel mainly!
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Old 1 May 2006, 04:38 (Ref:1598492)   #9
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Oh! thats terrible! I feel so sorry for you. My Aunt has one on her car and she doesn't drive any more. Would you accept a gift?
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Old 1 May 2006, 05:56 (Ref:1598512)   #10
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Oh! thats terrible! I feel so sorry for you. My Aunt has one on her car and she doesn't drive any more. Would you accept a gift?
Is she The Little Old Lady from Pasadena ?
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Old 1 May 2006, 13:07 (Ref:1598747)   #11
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Quote:
Originally Posted by norman-normal
An average car ft engine rear wheel drive will suffer about a 40% loss.
Absolutely no way near this much. From here:

Quote:
Originally Posted by http://www.pumaracing.co.uk/power3.htm
Average real transmission losses are about 10% of the flywheel power plus 10bhp for FWD cars and 12% plus 10bhp for RWD cars. This equates to about 15% to 17% for cars of "average" power output.

VW technical also quote their cars as losing, on average, about 15% of the flywheel power in the transmission and tyres.

The chassis dyno division of Bosch UK also suggest 15% as being a realistic estimate of transmission losses.
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Old 1 May 2006, 14:48 (Ref:1598789)   #12
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I drew my own conclusions using one of the first dynos in So Cal (no scientific method), autos used were American w/auto trans judged against "factory HP claims" at the time. (mid to late 50s) The factory HP claims in those days were a bit fancifull.... Please forgive me.
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Old 1 May 2006, 14:54 (Ref:1598793)   #13
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Is she The Little Old Lady from Pasadena ?

Yes Johnny, shes riding a Harley now, dressed in black from helmet to boots
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Old 1 May 2006, 20:17 (Ref:1598967)   #14
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Originally Posted by Rubinho
Absolutely no way near this much. From here:
Yeh, got to agree there. I just got off the rolling road with my car and it posted 184kw at the engine and 150kw at the wheels. That makes a 34kw transmission loss, or just over 18% of the engine power. I also know that Jaguars tend to be at the high end of these type of losses (for whatever reason). What always amazes me is that it's the equivalent of the mechanical drive train acting like ten three-bar electric fires... no wonder it gets hot
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Old 1 May 2006, 21:46 (Ref:1599008)   #15
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graham bahr should be qualifying in the top 10 on the gridgraham bahr should be qualifying in the top 10 on the grid
my car looses about 18% through the transmission despite the engine shoving 460bhp through it, the direct top gear probably saves some looses but then again 235 sticky slicks will increase the losses again

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Old 2 May 2006, 01:33 (Ref:1599080)   #16
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Originally Posted by graham bahr
my car looses about 18% through the transmission despite the engine shoving 460bhp through it, the direct top gear probably saves some looses but then again 235 sticky slicks will increase the losses again
interesting-you would think the transmission loss would be tending more to constant, not rising at the same percentage as the increase in power [at a given RPM of course]. Perhaps it has more to do with the maths where torque is converted to power to express the readout form that the punter wants-the extra KW OR BHP will turn up in the answers at higher RPM,where over a given period of time more spark plug firings are delivering more loads to the gears and generating heat,but at a moment of torque the transmission itself requires would not change.
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Old 2 May 2006, 02:54 (Ref:1599104)   #17
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I think the truth is somewhere in between Johnny, more power does create more heat and therefore more loss, but it is not a direct relationship.
In Grahams case the car is not going to simply double or halve its power, so working with a constant is accurate enough. I am sure some smart people would be able to work it out properly. After all you can't create or destroy energy, so if you know the imputs you could work out all the outputs.
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autos used were American w/auto trans judged against "factory HP claims" at the time. (mid to late 50s) The factory HP claims in those days were a bit fancifull....
Autos are hard work on the dyno as well, as (especially old tech) they slip almost constantly. So you are talking about total trans losses then? As I have said somewhere else the US use a different standard of measurement which involves no ancilleries.
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Old 2 May 2006, 18:52 (Ref:1599555)   #18
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I ran tripode inner and outer joints on my black-bird powered 750-F4 single seater, one of the shafts was at 12 degrees.......it made 145bhp at the wheels (as expected) and went like a missile down the straights......it aint worth worrying about......you do actually need a few degrees to promote internal lubrication and even wear, as being perfactly straight can actually weld themselves together, and hammer away at only one area.......5 degrees is no prob......its a 2 tenths of not a lot syndrome

Last edited by dtype38; 3 May 2006 at 15:12. Reason: Autocensor evasion
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