## Drive shaft angle

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
PaulB
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Joined: Sun Oct 17, 2010 8:52 am
Location: Graz/Austria

### Drive shaft angle

Hey folks!

Sorry, that's not Formula 1 (but F1 area is more visited than "other racing series", so I hope for a helpfull answer). As maybe a few of you are knowing, I'm working on an Audi R18TDI currently. Now I've found something strange.
At the gearbox calculations, I recognised something, what I cant really believe. Is it possible, that (the R18s) drive shafts are tilted forwards? (differential behind rear wheel centre line) That sounds to me not really logical - especially at racing cars.
The R18 ones are defenitively tilted about 10 degrees upwards. But that's nothing strange - the RB7 ones are also tilted upwards.

Thank's for helping.

Cheers, Paul
"Being second is to be the first of the ones who lose!" - Ayrton Senna

Paul Bischof
Milton Keynes, UK
MK2 2HL
http://paulsf1.wordpress.com/

222
Joined: Sat Jan 02, 2010 12:57 am

### Re: Drive shaft angle

The half shafts do indeed tilt upward and forward on both cars..
Last edited by strad on Wed Jul 18, 2012 7:52 am, edited 1 time in total.
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Jersey Tom
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Joined: Mon May 29, 2006 7:49 pm
Location: Huntersville, NC

### Re: Drive shaft angle

...I fail to see how X degrees upwards is normal but X degrees forward is strange. What difference does it make as far as the diff is concerned? Both seem perfectly normal to me.
Grip is a four letter word. All opinions are my own and not those of current or previous employers.

PaulB
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Joined: Sun Oct 17, 2010 8:52 am
Location: Graz/Austria

### Re: Drive shaft angle

Jersey Tom wrote:...I fail to see how X degrees upwards is normal but X degrees forward is strange. [...]
That's the reason why I asked.
I thought you also try to keep the half shafts as straight as possible (horizontal and vertical). For a lower COG it's usefull to keep the diff as low as possible and put up with the upward tilted shafts. But I still see no logical reason, to tilt the shafts forward... (appart from a (very) little more weight on the rear, but that can hardly be the reason) Maybe to build the car a little shorter.

Thanks to both of you.

Cheers,
Paul
"Being second is to be the first of the ones who lose!" - Ayrton Senna

Paul Bischof
Milton Keynes, UK
MK2 2HL
http://paulsf1.wordpress.com/

Jersey Tom
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Joined: Mon May 29, 2006 7:49 pm
Location: Huntersville, NC

### Re: Drive shaft angle

PaulB wrote:But I still see no logical reason, to tilt the shafts forward
When you design a car (or anything) you can't get everything 100% the way you want it. There are compromises to be made for packing, component layout, whatever.

Whatever they came up with is what they felt was the best total package - even if it means some individual components aren't "ideal."
Grip is a four letter word. All opinions are my own and not those of current or previous employers.

DaveKillens
54
Joined: Thu Jan 20, 2005 3:02 am

### Re: Drive shaft angle

I agree with most said here, but I pulled out my trusty pen and paper and attempted to see where torque would be applied relative to the center-line of where the drive-shaft exits the transmission. Correct me if I'm wrong, but if the wheels are ahead of the transmission, torque is vectored downwards, giving an anti-squat under acceleration. As far as the wheels being below the transmission, I believe it's all because of the need to get all that heavy mass of the transmission as low as possible.
Racing should be decided on the track, not the court room.

Jersey Tom
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Joined: Mon May 29, 2006 7:49 pm
Location: Huntersville, NC

### Re: Drive shaft angle

DaveKillens wrote:Correct me if I'm wrong, but if the wheels are ahead of the transmission, torque is vectored downwards, giving an anti-squat under acceleration.
Hmm. Not sure if that is the case. For a typical open wheel car with the gearbox / differential rigidly fixed to the body I think those forces are all resolved internally to the structure. The anti's would come into play through control arm geometry, or in the case of a stock car where the axle housing is separate from the body.
Grip is a four letter word. All opinions are my own and not those of current or previous employers.

rjsa
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Joined: Fri Mar 02, 2007 2:01 am

### Re: Drive shaft angle

Torque knows only direction, not point of application.

xpensive
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Joined: Sat Nov 22, 2008 5:06 pm
Location: Somewhere in Scandinavia

### Re: Drive shaft angle

Jersey Tom wrote:
DaveKillens wrote:Correct me if I'm wrong, but if the wheels are ahead of the transmission, torque is vectored downwards, giving an anti-squat under acceleration.
Hmm. Not sure if that is the case.
...
I agree, believe it or not, the conveyed torque itself is never attached to neither suspension nor structure outside of the diff, why the chassis will never see any of it?

However, does anyone know something about powerloss from out-of-angle drive-joints?
"I spent most of my money on wine and women...I wasted the rest"

Lycoming
134
Joined: Thu Aug 25, 2011 9:58 pm

### Re: Drive shaft angle

I've heard one manufacturer quote 4% at 12 degrees, the maximum they specify for that particular type of CV joint.

PaulB
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Joined: Sun Oct 17, 2010 8:52 am
Location: Graz/Austria

### Re: Drive shaft angle

Lycoming wrote:[...] 4% at 12 degrees, the maximum they specify for that particular type of CV joint.
Yep, that's a usefull information. Thanks!
"Being second is to be the first of the ones who lose!" - Ayrton Senna

Paul Bischof
Milton Keynes, UK
MK2 2HL
http://paulsf1.wordpress.com/

Jersey Tom
246
Joined: Mon May 29, 2006 7:49 pm
Location: Huntersville, NC

### Re: Drive shaft angle

rjsa wrote:Torque knows only direction, not point of application.
True but kind of deceiving. There are suspension topologies where the torque from the engine is resolved internally and/or there are no anti's and it's all nice and easy.

There are others where you can have significant longitudinal anti's, body roll with drive torque, etc... all which has to be accounted for. The torque ultimately has to become a force at the ground after all.
Grip is a four letter word. All opinions are my own and not those of current or previous employers.

tommylommykins
2
Joined: Tue May 12, 2009 9:14 pm

### Re: Drive shaft angle

do you also get slightly sinusoidal rotation speed from the geometry of CV joints?

...In answer to my own question, no, CV joint == constant velocity

xpensive
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Joined: Sat Nov 22, 2008 5:06 pm
Location: Somewhere in Scandinavia

### Re: Drive shaft angle

tommylommykins wrote:do you also get slightly sinusoidal rotation speed from the geometry of CV joints?
You do indeed with a conventional joint, but that is directly neutralized with two joints on the same shaft interacting.
"I spent most of my money on wine and women...I wasted the rest"

marcush.
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Joined: Tue Mar 09, 2004 3:55 pm

### Re: Drive shaft angle

this for Saab fans: