Differentials...
Discussion
Assume you mean 1000 lbs-ft, but measured where? I know you're aiming for a monster engine, but the loads on the diff are limited by what you can put down through the tyres. Just that in your case, it'll be going a lot lot faster at the time. What do you have planned in the way of transmission coolers?
GreenV8S said:
Assume you mean 1000 lbs-ft, but measured where? I know you're aiming for a monster engine, but the loads on the diff are limited by what you can put down through the tyres. Just that in your case, it'll be going a lot lot faster at the time. What do you have planned in the way of transmission coolers?
Something very special!
But any pointers in the direction of reputable diff manufacturers will be very helpful... although a Jaguar unit has already been selected - havent put the money down on it just yet - in case I can get something better for the job.... been looking at the detroit locker combo - but its a heavy mutha!
Been looking at getting one built to custom spec, not cheap, but might be something I'll consider in the future - but for now just need something that can cope reliably...
A Viper rear end can handle that kind of power, possibly with uprated driveshafts, and its only an 8" AFAIK, and a much heavier car.
No doubt there are plenty of US cars with rear axles strong enough to cope, but it depends what you intend to do with it, and how much of the car you want to modify to fit it.
The typical 9" Ford live axle setup will probably handle as much power as you will ever need it to, but you will compromise the cars handling going live, rather than IRS.
There are mustangs out there, that use the 8.8" axle I have in solid confiuration, and its reputed to be virtually unbreakable with 31 spline shafts. It is also available in IRS form, where again, driveshafts would then be a potential weak spot, but no doubt the aftermarket will cater for it.
Using such a diff setup will make CWP, and diffs cheap, and offer you a good range of CWP..
But most will say you need a spool for that sort of power. Regardless of what any of the US guys say about then, I'd never consider using a spool on the road.
spool = locked diff.
No doubt there are plenty of US cars with rear axles strong enough to cope, but it depends what you intend to do with it, and how much of the car you want to modify to fit it.
The typical 9" Ford live axle setup will probably handle as much power as you will ever need it to, but you will compromise the cars handling going live, rather than IRS.
There are mustangs out there, that use the 8.8" axle I have in solid confiuration, and its reputed to be virtually unbreakable with 31 spline shafts. It is also available in IRS form, where again, driveshafts would then be a potential weak spot, but no doubt the aftermarket will cater for it.
Using such a diff setup will make CWP, and diffs cheap, and offer you a good range of CWP..
But most will say you need a spool for that sort of power. Regardless of what any of the US guys say about then, I'd never consider using a spool on the road.
spool = locked diff.
What do you think are the limiting factors for the diff though, are you sure you need such an exotic diff? Diffs are rated in terms of torque not power. The torque taken by the diff is limited by the tyres, if you fit a 1,000,000 bhp engine the diff will still only take enough torque to spin the wheels. If you run sticky tyres this will increase the torque accordingly but still you are not looking at massive torque increases. Cooling is another matter altogether, but you already said you are addressing that.
The engineers have run the calculations - and with a specific 6 speedbox and the SI diff with certain size tyres with a specific psi and rear end weight and torque with the added vertical force - we're talking some crazy numbers for traction, but that will only come into play in the strip... on the road - we're talking a different ball game altogether - feck - I wish I had a plug'n'play system and could just change the drivetrain for road and drag by the flick of a switch - I dont want to compromise my strip times and I dont want to screw up the road enjoyment.... what a wonderful world this is, its one or the other or only half good for both.... that sucks....
Assuming you have enough power (I think that is a safe assumption here!
) the loads on the diff are determined by the traction and not the other way round. Don't know quite how your engineer chums are working this out, I'm just trying to point out that just because your engine puts out 4x more power than standard doesn't mean your diff has to be 4x stronger. It is already strong enough to spin the wheels. Sticky tyres will increase the loads (ballpark +50%), running more power will mean you reach the peak loads more often so you might eat into your fatigue life, but as far as I can see you don't need the sort of massively strong diff that you would see in a heavy muscle car or dragster. Anyway, no doubt your engineers are on the case.
) the loads on the diff are determined by the traction and not the other way round. Don't know quite how your engineer chums are working this out, I'm just trying to point out that just because your engine puts out 4x more power than standard doesn't mean your diff has to be 4x stronger. It is already strong enough to spin the wheels. Sticky tyres will increase the loads (ballpark +50%), running more power will mean you reach the peak loads more often so you might eat into your fatigue life, but as far as I can see you don't need the sort of massively strong diff that you would see in a heavy muscle car or dragster. Anyway, no doubt your engineers are on the case.GreenV8S said:
Assuming you have enough power (I think that is a safe assumption here!
Apparently if we pushed through 900lbs of torque at 7000RPM through the engine with the ratio step etc from the box to the rear end - engineers words "you will rip your box and diff apart and your driveshafts will snap, and if you're very unlucky propshaft will splinter off and flip you over or tear your chassis in half" - so the custom diff and box and propshaft and driveshafts will be able to handle just over 1500lbs of torque - I went out in a hot rod auto 3 speed conversion just yesterday - and - it was freakin horrible to even sit in whenever the drag auto box clunked in - and its constant whining - so I think I'll stick with a 6 speed smooth one with an electronic 3 plate clutch I believe.... those 3 speed autos might be the way for the strip - but on the road - damn you're better off sitting in a diesel isuzu jugger...
Correct me if I'm wrong, but the Borg Warner T5 is only capable of around 400lbs max in its standard form, before reliability becomes a serious issue?
And the Tremec T56 is around 450lbs in standard?
Engineer wants me to go for a german custom jobbie, he says it might cost more - but its an exotic piece of kit and very low maintenance - even has a specific internal cooling design... and will handle anything I throw at it - although would have to keep a spare clutch or two when dragging....
>> Edited by SXS on Saturday 30th October 16:18
And the Tremec T56 is around 450lbs in standard?
Engineer wants me to go for a german custom jobbie, he says it might cost more - but its an exotic piece of kit and very low maintenance - even has a specific internal cooling design... and will handle anything I throw at it - although would have to keep a spare clutch or two when dragging....
>> Edited by SXS on Saturday 30th October 16:18
Obvously your guy knows what he's talking about but I still don't understand his logic. I mean, if you put your car up on axle stands will your 900 lb-ft tear the back axle apart? I don't see how. It doesn't matter what you do at the front of the car, your back axle will only see the loads transmitted to the road.
I'm deliberately ignoring transient effects from the inertia of the wheels and from transient weight variations because these apply regardless of the engine power, I'm just looking at it from the steady state pont of view.
I'm deliberately ignoring transient effects from the inertia of the wheels and from transient weight variations because these apply regardless of the engine power, I'm just looking at it from the steady state pont of view.
T5's can be made to handle in excess of 600lbft, Ive already posted those links before.
T56's can be made to handle in excess of 800lbft.
The factory rating varies from around 450-550lbft
These are the ratings given, but in many cases, they will handle much greater than this, and it will vary on application. It depends on usage, the driver etc. A road car with 800bhp, with skinny road tyres may never break the standard transission when used on the road.
A similar weight car, with only 500bhp, launching on the strip with slick may break the trans on its first run.
The trans will be put under much greater loads on say a 4000lb drag car running on full slicks, than it ever will on a lightweight Cerbera, with any amount of power.
Traction and weight are the biggest factors.
ANY Ford 9" diff would IMO be strong enough. I dont have any calculations to back this up, but with so many people using them the world over, I think it has been proven.
As I also said, the Ford 8.8" would also do.
With regards to diffs, the biggest limiting factor will be driveshafts, and any internal workings within the diff, not the actual CWP itself.
T56's can be made to handle in excess of 800lbft.
The factory rating varies from around 450-550lbft
These are the ratings given, but in many cases, they will handle much greater than this, and it will vary on application. It depends on usage, the driver etc. A road car with 800bhp, with skinny road tyres may never break the standard transission when used on the road.
A similar weight car, with only 500bhp, launching on the strip with slick may break the trans on its first run.
The trans will be put under much greater loads on say a 4000lb drag car running on full slicks, than it ever will on a lightweight Cerbera, with any amount of power.
Traction and weight are the biggest factors.
ANY Ford 9" diff would IMO be strong enough. I dont have any calculations to back this up, but with so many people using them the world over, I think it has been proven.
As I also said, the Ford 8.8" would also do.
With regards to diffs, the biggest limiting factor will be driveshafts, and any internal workings within the diff, not the actual CWP itself.
I think there was something mentioned about reverse rotational feedback and inertia slap - which can cause something which is running close to its t-limit to just bend/stretch causing cracking etc... the new 6 speed box is a ZF custom build one about 35% lighter than the existing T5 and the new diff is about 10% heavier - the driveshafts are also about 15% heavier than standard - I dont know if you chaps have seen the cerb's driveshafts - but they're tiny little tubes! these new driveshafts are about 2-3 times the diameter...
Stevie, totally understand and accept the tyre/wheel size effect on driveshafts/diffs/gearbox - this is my greatest worry - I will have two sets, 16's with raw fat slicks on low psi, and then 20's with low profile road tyres - so have to get this bit right... this will be the difference between enjoying her reliably and not having to rebuild diffs/boxes....
Stevie, totally understand and accept the tyre/wheel size effect on driveshafts/diffs/gearbox - this is my greatest worry - I will have two sets, 16's with raw fat slicks on low psi, and then 20's with low profile road tyres - so have to get this bit right... this will be the difference between enjoying her reliably and not having to rebuild diffs/boxes....
[quote=SXS ]
...if you're very unlucky propshaft will splinter off and flip you over or tear your chassis in half"[/quote]
That's what a propshaft loop is for - stops the propshaft battering it's way into the car if it snaps at the diff end - you'd be nuts to fit slicks and not have one (I'm also pretty sure it's an NHRA and IHRA reg that cars as fst as yours have to have one, so you won't get through scrutineering if you don't)
...if you're very unlucky propshaft will splinter off and flip you over or tear your chassis in half"[/quote]
That's what a propshaft loop is for - stops the propshaft battering it's way into the car if it snaps at the diff end - you'd be nuts to fit slicks and not have one (I'm also pretty sure it's an NHRA and IHRA reg that cars as fst as yours have to have one, so you won't get through scrutineering if you don't)
not really sure what way the NHRA or IHRA work, but do they operate within the UK ??
I know of a few 9sec cars that can be used on the road here, and Id say none of them have roll cages, or other safety equipment that the US drag regs would have as mandatory for cars so fast.
And something else to consider. At that level of tuning and power, no matter what you build and consider to be unbreakable, something will always give. Otherwise, every car in motorsport would have 100% reliability.
I would build reliability in as much as is reasonable given cost considerations, and ease of replacement.
At least that way when something does fail, its easy and cheap to replace.
Fitting a mega expensive diff and shafts is certainly good, but no doubt still not 100% gauranteed unbreakable. But if or when it does break, it will cost another fortune to replace.
Id go to tried and tested American parts as used in some of their high powered road cars that the guys regularly race, as many have 800bhp+ in much heavier cars than you, and often use slicks at the track. They consist of various large diffs, some 8-9" in size, some live some IRS.
Most parts will be off the shelf, and fairly cheap.
The propshaft safety loop is a very wise idea, unless you are going for a carbon shaft, in which case it becomes less important, as if it breaks under drive, it should shatter if it hits the ground, rather than catapulting the car into the air.
I know of a few 9sec cars that can be used on the road here, and Id say none of them have roll cages, or other safety equipment that the US drag regs would have as mandatory for cars so fast.
And something else to consider. At that level of tuning and power, no matter what you build and consider to be unbreakable, something will always give. Otherwise, every car in motorsport would have 100% reliability.
I would build reliability in as much as is reasonable given cost considerations, and ease of replacement.
At least that way when something does fail, its easy and cheap to replace.
Fitting a mega expensive diff and shafts is certainly good, but no doubt still not 100% gauranteed unbreakable. But if or when it does break, it will cost another fortune to replace.
Id go to tried and tested American parts as used in some of their high powered road cars that the guys regularly race, as many have 800bhp+ in much heavier cars than you, and often use slicks at the track. They consist of various large diffs, some 8-9" in size, some live some IRS.
Most parts will be off the shelf, and fairly cheap.
The propshaft safety loop is a very wise idea, unless you are going for a carbon shaft, in which case it becomes less important, as if it breaks under drive, it should shatter if it hits the ground, rather than catapulting the car into the air.
stevieturbo said:
not really sure what way the NHRA or IHRA work, but do they operate within the UK ??
I know of a few 9sec cars that can be used on the road here, and Id say none of them have roll cages, or other safety equipment that the US drag regs would have as mandatory for cars so fast.
And something else to consider. At that level of tuning and power, no matter what you build and consider to be unbreakable, something will always give. Otherwise, every car in motorsport would have 100% reliability.
I would build reliability in as much as is reasonable given cost considerations, and ease of replacement.
At least that way when something does fail, its easy and cheap to replace.
The propshaft safety loop is a very wise idea, unless you are going for a carbon shaft, in which case it becomes less important, as if it breaks under drive, it should shatter if it hits the ground, rather than catapulting the car into the air.
NHRA and IHRA both operate in the UK - IIRC Santa Pod is NHRA sanctioned? and Shakey is IHRA, but It could be the other way round...
Just checking my IHRA rulebook (local track is IHRA sanctioned, so I don't have an NHRA rulebook to hand) - a propshaft safety loop is mandatory on any car running slicks, no matter how slow, and anything faster than 11.50s 1/4 mile must have a loop no matter what it's running (slicks/treaded/road tyres/bycicle wheels
). And even the carbon shaft can do some nasty damage if they break - as it's usually the U-joint at the diff end that breaks, not the shaft itself (seen at least half a dozen do this this year) and even a carbon shaft (which usually has a steel or aluminium cap on the end for the U-joint) can batter it's way into the passenger compartment before it shatters... Everyone I've spoken to says the propshaft risk is more of it beating it's way into the car rather than flipping it that is the real danger.
I certainly agree that something will always fail eventually, and you can't prepare for everything, but for such an easy and cheap to fit (peanuts compared to a 700 bhp+ engine
)safety feature as a propshaft loop, you'd be nuts not to fit one IMHOAha, sorry fellas, forgot to mention it - yes they will be fitting 'Muscle Power' clamps around the propshaft and also plating under the whole drivetrain - the cerbera is a tubular chassis with glassfibre everything so will need the reinforcement - the technical director at the company said that he wont be happy to let me take the car onto the strip without reinforcing a number of areas... he said its a good thing the car has an integral rollcage, but he says he will look into making a removable crossbar for the cage... theres also ideas flying around on replacing the side windows with acrylic versions... there has been talk in regards to removing the back seats - but they're tiny and flimsy anyway - so I doubt I'd save much more than a around 10kg tops... the cars already too light - any lighter and the power coming out of the engine will launch me into orbit.... Been looking into a whole carbon fibre front end.... but the bodywork (stage 3) will have to wait a little bit longer till the finances hole fills up again... by the way stevie have you seen Aeromotives suggestion on the fueling system on the project website's forum yet? www.projectphoenix.xt7.net
[quote=SXS ]I'm trying to choose a rear-end differential to handle in the region of 1000lbs of torque, the one thats been recommended by the Pyle Bros over in Texas, is the Detroit Locker with a 35 spline setup.
Any views or info on alternative lockable differentals?[/quote]
Probably the best diff out there is a Gripper differential. Made in sunny Coventry.
Bear in mind that for a ZF with say 3:1 first gear and 3.3:1 rear axle ratio you get 10 times multiplication in first gear. To get 1000 ftlbs of torque on the rar end only requires 100ftlbs at the engine.
I would suggest that you want 40% locking in first gear, so for a 500 lb ft engine with 10x multiplication in first you are generating 5000 ftlbs at the rear axle. So the plates need 2000 ftlbs minimum capacity.
Any views or info on alternative lockable differentals?[/quote]
Probably the best diff out there is a Gripper differential. Made in sunny Coventry.
Bear in mind that for a ZF with say 3:1 first gear and 3.3:1 rear axle ratio you get 10 times multiplication in first gear. To get 1000 ftlbs of torque on the rar end only requires 100ftlbs at the engine.
I would suggest that you want 40% locking in first gear, so for a 500 lb ft engine with 10x multiplication in first you are generating 5000 ftlbs at the rear axle. So the plates need 2000 ftlbs minimum capacity.
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff