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Trailbraker · 10-09-2006

Originally Posted by Peter K

Ok....now I am confused..

AFAIK any type of 1 way Limited slip Diff will not work if one wheel does not have any traction? Otherwise we are talking locking diff (as in off road vehicles) or very very agressive diffs not suited for Road use. (2 way diff)

Clutch type LSDs lock - Thats how they work!

They progressively limit the difference in the rotational velocity between the two wheels.
e.g. mine is set at 30% locking factor.
So the unloaded wheel in a corner can spin up to 30% faster than the outside wheel.
The locking of the faster spinning wheel to a fixed proportion of the other wheels rotation forces torque to be transferred to the outside wheel under cornering, even if the inside wheel is airborne...
i.e. the rotation velocity of the two wheels is locked together up to a fixed proportion.

This is NOT the same as a welded diff which would just cause huge understeer everywhere in an FWD, and huge oversteer everywhere in a RWD

When you say off road vehicles you are probably thinking of locking diffs that cause understeer when the two wheels rotational velocity is locked together completely..
These aren't really comparable to progressively locking performance oriented diffs. Their main job is usually to just avoid wheelspin to allow some behemoth to get out of a pile of mud.

I believe "1 way", "2 way" and "2 and a half way" diffs just refer to the level of differentiation under braking as well as under acceleration.
1 way diffs only function under acceleration as opposed to braking.

I think the AD LSD would also stop working of one wheel looses all traction?

No, the two wheels rotational velocity are coupled within a certain proportion.
This is hugely different to a torque sense diff such as Quaiffe that limits the proportion of torque transfer to a certain proportion.
e.g. For an ATB torque bias ratio of 8:1 the torque can only be transmitted in a max split of 8:1 between the two wheels.

In summary one limits the rotational wheelspeed difference,
the other limits the torque split proportion.

Maybe the Clutch type is only activated via Torque from engine? In this case I wold say this type seems significantly more dangerous in the event of one wheel completely loosing traction, not mentioning the risk of damaging drive shafts and other components when the wheel regains traction while full power is still transfered to it.

On the contrary - I believe you have just described the main disadvantage of torque sensing diffs such as Quaiffe

Since they are technically incapable of limiting the proportional difference of rotational velocity between the two wheels (like a locking clutch type LSD can), an airborne wheel will spin up to high speeds and theoretically cause huge stress when it lands.
Some googling will probably find lots of statements of this characteristic, with another example being when you have one wheel on grass on one on tarmac.. and then rejoin the track, again a sudden transfer.

That said Quaiffe specifically offer a lifetime guarantee even for track use so their parts must be pretty well made.
(although I presume the guarantee just covers replacement rather than other damage).

Cheers,
TB

10-09-2006	#103 (Post Link)
Trailbraker AO Silver Member Join Date: Mar 2005 Location: Ireland Posts: 4,825 Member car: 156 GTA	Re: LSD Group order ? Originally Posted by Peter K Ok....now I am confused.. AFAIK any type of 1 way Limited slip Diff will not work if one wheel does not have any traction? Otherwise we are talking locking diff (as in off road vehicles) or very very agressive diffs not suited for Road use. (2 way diff) Clutch type LSDs lock - Thats how they work! They progressively limit the difference in the rotational velocity between the two wheels. e.g. mine is set at 30% locking factor. So the unloaded wheel in a corner can spin up to 30% faster than the outside wheel. The locking of the faster spinning wheel to a fixed proportion of the other wheels rotation forces torque to be transferred to the outside wheel under cornering, even if the inside wheel is airborne... i.e. the rotation velocity of the two wheels is locked together up to a fixed proportion. This is NOT the same as a welded diff which would just cause huge understeer everywhere in an FWD, and huge oversteer everywhere in a RWD When you say off road vehicles you are probably thinking of locking diffs that cause understeer when the two wheels rotational velocity is locked together completely.. These aren't really comparable to progressively locking performance oriented diffs. Their main job is usually to just avoid wheelspin to allow some behemoth to get out of a pile of mud. I believe "1 way", "2 way" and "2 and a half way" diffs just refer to the level of differentiation under braking as well as under acceleration. 1 way diffs only function under acceleration as opposed to braking. I think the AD LSD would also stop working of one wheel looses all traction? No, the two wheels rotational velocity are coupled within a certain proportion. This is hugely different to a torque sense diff such as Quaiffe that limits the proportion of torque transfer to a certain proportion. e.g. For an ATB torque bias ratio of 8:1 the torque can only be transmitted in a max split of 8:1 between the two wheels. In summary one limits the rotational wheelspeed difference, the other limits the torque split proportion. Maybe the Clutch type is only activated via Torque from engine? In this case I wold say this type seems significantly more dangerous in the event of one wheel completely loosing traction, not mentioning the risk of damaging drive shafts and other components when the wheel regains traction while full power is still transfered to it. On the contrary - I believe you have just described the main disadvantage of torque sensing diffs such as Quaiffe Since they are technically incapable of limiting the proportional difference of rotational velocity between the two wheels (like a locking clutch type LSD can), an airborne wheel will spin up to high speeds and theoretically cause huge stress when it lands. Some googling will probably find lots of statements of this characteristic, with another example being when you have one wheel on grass on one on tarmac.. and then rejoin the track, again a sudden transfer. That said Quaiffe specifically offer a lifetime guarantee even for track use so their parts must be pretty well made. (although I presume the guarantee just covers replacement rather than other damage). Cheers, TB I'm not a doctor - but I really do recommend braking later Last edited by Trailbraker : 10-09-2006 at 22:44.