What's a 'spool'?
Discussion
Tony
drag racers use spools, it is a locked diff to maximize traction and to stop torque steering the car to one side and also even out power delivery to both wheels, naughty folks used to make their own by welding the sun gears together, a practice which is now banned, I am interested how a spool would assist a circuit racer unless they are able to dial in "slippage" in some way
Steve
drag racers use spools, it is a locked diff to maximize traction and to stop torque steering the car to one side and also even out power delivery to both wheels, naughty folks used to make their own by welding the sun gears together, a practice which is now banned, I am interested how a spool would assist a circuit racer unless they are able to dial in "slippage" in some way
Steve
Correct. A spool is a solid axle (no differential). The Sierra RS500s used to run them.
IIRC, the trade off is traction and no torque steer vs. understeer and scrub. In the case of the Sierra, it made them far more predictable and driveable on boost, allowing the power to be applied earlier in the corners. It turned the cars into point and squirt machines where the best technique was to square off the corners as much as possible. This advantage was deemed greater than the tyre preservation and lesser turn-in understeer of an LSD.
IIRC, the trade off is traction and no torque steer vs. understeer and scrub. In the case of the Sierra, it made them far more predictable and driveable on boost, allowing the power to be applied earlier in the corners. It turned the cars into point and squirt machines where the best technique was to square off the corners as much as possible. This advantage was deemed greater than the tyre preservation and lesser turn-in understeer of an LSD.
most of the porsche 935's had them and a load of other mega powered cars. you have to drive them in a different way to normal diff'd cars, you really need to steer from the rear so to speak, otherwise they just understeer.
from the Ozzy v8 side of things, they keep the spool in the rules because they don't like to much change and it keep the racing exciting, watching the cars slide around.
from the Ozzy v8 side of things, they keep the spool in the rules because they don't like to much change and it keep the racing exciting, watching the cars slide around.
Edited by wildman0609 on Tuesday 28th August 18:57
So wouldn''t a locking diff or spool that's fixed cause some really big stresses when turning? if the car is turning then the inside wheel physically can't turn at the same speed as trhe outside wheel? Does the inside wheel (or the outside, I'm assuming the wheel that's loaded the most would be the outside one) then lose traction and scrub the tyre to remain turning at the same speed as the outside tyre? Wouldn't that cause some horrendous tyre wear?
I remember the case of the Volvo 4WD system that used to lunch itself if you ran tyres with different tread depths and Volvo didn;t realise this. Wouldn't the same or a similar thing happen on this? back when indycar and Champcars were sepaerate Indycars couldn't run on road courses and used to race on Ovals only because they didn't have an open Differential, only a locked one so they said until they developed one the cars transmission woudl almost eat itself if you tried turning the car.
now I'm confused!
I remember the case of the Volvo 4WD system that used to lunch itself if you ran tyres with different tread depths and Volvo didn;t realise this. Wouldn't the same or a similar thing happen on this? back when indycar and Champcars were sepaerate Indycars couldn't run on road courses and used to race on Ovals only because they didn't have an open Differential, only a locked one so they said until they developed one the cars transmission woudl almost eat itself if you tried turning the car.
now I'm confused!
I think indy cars only run the "spool" diff on the shorter ovals, places like Indy they have an open diff to free up the car.
The reason they work is they run stagger on the rear tyres, so the outside is bigger than the inside, therefore the car is always trying to turn left. They actually have to turn right down the straights to keep in a straight line.
The reason they work is they run stagger on the rear tyres, so the outside is bigger than the inside, therefore the car is always trying to turn left. They actually have to turn right down the straights to keep in a straight line.
[quote=MissChief]So wouldn''t a locking diff or spool that's fixed cause some really big stresses when turning? if the car is turning then the inside wheel physically can't turn at the same speed as trhe outside wheel? Does the inside wheel (or the outside, I'm assuming the wheel that's loaded the most would be the outside one) then lose traction and scrub the tyre to remain turning at the same speed as the outside tyre? Wouldn't that cause some horrendous tyre wear?
quote]
Yes lots of stress on the drivetrain. For eg the principle is the same though when i raced RC cars (4wd) we used to use a spool on the front axle. The car handles loads better however driveshafts used to bend all the time because one wheel is wanting to turn faster than the other while going round a corner.
I belive peoplle used to also weld up diffs in 2wd rally cars like the Chevette's tbh i dont know if its still like that.
quote]
Yes lots of stress on the drivetrain. For eg the principle is the same though when i raced RC cars (4wd) we used to use a spool on the front axle. The car handles loads better however driveshafts used to bend all the time because one wheel is wanting to turn faster than the other while going round a corner.
I belive peoplle used to also weld up diffs in 2wd rally cars like the Chevette's tbh i dont know if its still like that.
Scuffers said:
spool diffs are not locked all the time...
they are effectively an LSD that's either on or off..
they used to be used because at the time, there were not the LSD'd that could cope with the torque, (no longer the case).
Spools are perminatly locked, there is no slip posible.they are effectively an LSD that's either on or off..
they used to be used because at the time, there were not the LSD'd that could cope with the torque, (no longer the case).
A full spool is basically just a piece of metal the ring gear is bolted to that the output shafts slide into.
A mini spool is a set of parts that replace the sun gears in the diff unit, to again give a solid driven assembly.
What you are describing may be a detroit locker, which is an LSD unit that has dog faces that provide drive, once you overcome the spring preload against the dog faces it jumps to the next dog, inducing some slip. Detroit lockers are quite brutal, they drive almost like a spool, so you have to be agresive with them and drive the car sideways on the power, but they do offer a modicum of slip for low speed tight corners.
johnfelstead said:
Scuffers said:
spool diffs are not locked all the time...
they are effectively an LSD that's either on or off..
they used to be used because at the time, there were not the LSD'd that could cope with the torque, (no longer the case).
Spools are perminatly locked, there is no slip posible.they are effectively an LSD that's either on or off..
they used to be used because at the time, there were not the LSD'd that could cope with the torque, (no longer the case).
A full spool is basically just a piece of metal the ring gear is bolted to that the output shafts slide into.
A mini spool is a set of parts that replace the sun gears in the diff unit, to again give a solid driven assembly.
What you are describing may be a detroit locker, which is an LSD unit that has dog faces that provide drive, once you overcome the spring preload against the dog faces it jumps to the next dog, inducing some slip. Detroit lockers are quite brutal, they drive almost like a spool, so you have to be agresive with them and drive the car sideways on the power, but they do offer a modicum of slip for low speed tight corners.
They are not 'locked' all the time, however, slip not the way to describe them.
Sorry Scuffers. I'll side with John here.
A spool is a locked diff. It looks like this:
A Detroit Locker - what we had in the ASCAR/SCSA/Days of Thunder/V8 Trophy cars is like this (cutaway pic):
I have a number of different springs for the "locker" in my Winters axle - the different pre-load settings make the car behave differently. You certainly know when it locks as you apply power! Great fun around Cadwell though! The car is very drifty, and you have to "drive" it to go quickly.
The Aussie V8 Supercars use Ford 9" Axles with spools in them. They run a crazy amount of camber to help the cars turn in better. Makes them an arse to get off the line without bags of spin.
A spool is a locked diff. It looks like this:
A Detroit Locker - what we had in the ASCAR/SCSA/Days of Thunder/V8 Trophy cars is like this (cutaway pic):
I have a number of different springs for the "locker" in my Winters axle - the different pre-load settings make the car behave differently. You certainly know when it locks as you apply power! Great fun around Cadwell though! The car is very drifty, and you have to "drive" it to go quickly.
The Aussie V8 Supercars use Ford 9" Axles with spools in them. They run a crazy amount of camber to help the cars turn in better. Makes them an arse to get off the line without bags of spin.
Edited by thunderbelmont on Sunday 2nd September 22:17
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