The Cal-look Lounge

Wondering if there was any benifit in raising the gearbox in my oval ???
It`ll be running a T2 `box so its obviously IRS, is it a mod that has more benifit in a swing axle car?
Obviously it gives a bit more ground clearance for the sump, but will it benifit handling / stability much?
Opinions gratefully recived! ;D

You won't get any more clearance for the sump unless you change to bigger wheels or change the angle of the axles.
It is called raised transmission, but more or less you have the trans and wheels in the same height and lower the body over it.

Hi Roman,

When the gearbox is raised so is the engine therefore increasing sump - ground clearance, I thought this came about to improve axle angle when launching.I know raising the complete torsion tube / frame forks on a s/a car lowers it without the dreaded camber changes that happen when adjusting spring plates, I`m just not clear if its an advantage on an irs car which won`t be particularly low.
Smaller wheels (diameter) will lower the rear end and give less sump clearance though.
Cheers,
Kev

No... Remember, the engine bolts to the gearbox.

Raised gearbox = raised engine = raised rear wheels
 :)

No... Remember, the engine bolts to the gearbox.
[/quote]

I know but I was asking about raising the gearbox / engine alone.


That car has the entire rear torsion tube / rear forks raised hasn`t it? that would obviously lower the car, my question is whether there was any advantage in raising the gearbox / engine for drag racing or is it simply when a car is commonly refered to as having a `raised gearbox` the complete torsion tube & rear forks have actually been moved?
Cheers,
Kev

if you do it correctly
and raise the entire rear suspension
not just the gearbox
you will not gain ground clearance
it will raise all that in relation to the body not to the ground
it will therefore lower the body on the ground and those iteams

if however you raise only the gearbox
you will get a slight ground clearance advantage
however
your suspension geometry just went to hell also

Kev when you raised the gearbox you also have to re do the suspension geometry.

Kev, raising the gearbox (1" taller mounts for example) raises the engine and gearbox relative to the frame horns and pan. As Austin said though, your suspension geometry will be out too, so you'll need to lower the car by the same amount on the springplates. This isn't ideal because you've then got less suspension movement before you hit the bumpstops. It's most often done to lower the back of a swingaxle car and then restore the camber of the rear wheels.
Cutting off the whole back of the chassis with torsion bars and frame horns and raising everything up together is the better solution - this keeps the rear suspension working fully and gets the back of the car down as shown on the yellow oval in Stephans post above.

So guys do you think doing a raise is a good or bad thing.

As Heil has said
This isn't ideal because you've then got less suspension movement before you hit the bumpstops.

the idea behind raising the box, is nothing to do with clearance at all, it only really works for swing axle cars, its like this.

the spring plate (this transmits the torque throug the chassis) is like a mini ladder bar, and if the pivot point of the (ladder bar) spring plate is higher than axle center the car will try to wheelie as its transfering the the power through the car on a rough line throught the spring plate, this is bad once you get into the high HP levels, as going up isnt going forward.
So you lower you lower the rear of the car to enable the power to be directed to a lower point (follow the line of the spring plate, roughly) now this is great! but the only problem is that your camber is all wrong now, so your only using the inside of the tire, and giving the axles a load of pain!. so you raise the trany to level out the axels and hey presto, your camber is correct the springplates (lader bars) are point at an angle to allow you to put more power throght the chassis.

as a rule of thub, the center line of the axle should be about 1 1/2 higher than the fulcrum of the spring plate.

So running a lader bar car like my 52 and lil woper, i can tune how the car runs, if i want big wheelies and impress the crowed, i raise the lader bars (axle stays in the same palce), but if i want to go fast then the lader bars are running low, if you go too low it will light the tires up, but thats a whole nother lesson.


If your running IRS then it dont matter where the gearbox is. it matters how your suspention arms work.





Martin.

Thanks for the input guys, this is exactly what I wanted to know ;D
As I said, this is a subject I`ve heard referred to a lot but never had an explanation of why it works or when it becomes a good thing to do.
I`m building my first race car & starting with a clean slate so want to do it properly, theres no point of making something that won`t work when theres so much information available from experienced builders / racers.

Although I can see my bar bill from EBI3 being scary by the time I`ve repaid all the good advice with beer.. :D

Kev, on another note... Any update on the ex-Colin Burnham project?

did somone say beer?

I`ve got to be honest - it`s not progressed at all ::)
This oval`s side tracked me a bit (a lot..) though, and KS`s old fastback will be done next as its only 3-4 weeks away from paint.
I actually considered selling it as there was a guy in Ireland who wanted it but nothing happened.
Because I`m only home 3 - 14 days at a time with a total of about 4 1/2 months a year, along with a major house rebuild (which is now 98% done ;D) cars take me ages to do!
I`ve collected most of the bits it needs though & its in a nice dry garage.

Once I get to it I`ll keep you posted ;D
Cheers,
Kev

Thanks for the update!
I loved that car when it came out back in the '80s.

That is good information right there, never crossed my mind!! Thanks!

No problem, its nice to have a place to share information.


eveyday is a school day.

It is for me! ;) :D

I`m still in nursery school.. ;)

arnt there rules about that ;) lol

Draggin g up an old thread, but a valid one! :D
So what we're saying is that the axle centre line should be about 1 1/2" above the line of the torsion bar, and the gearbox mounts then need raising to keep the axles level or even slight positive camber. Does anyone know how much raise exactly is this? 1", 2"? Or somewhere in between? It's kind of important for setting ride height I'd imagine! I really don't want to do the torsion raise and narrow, but the new car will need to come down some at the back I think, and it's best to build it to go forwards as quickly as possible!

the amount of raise depends on the amount of rake the cars going to have...... more rake, the less the amount of raise.  and you want to keep your wheels with 0 camber and the axles strait .


Martin

Good point, I hadn't thought of that! I'll have to build the front end up too! :D Cheers Martin!

The original post was asking about a car with an IRS in it.

Raising the trans will not affect suspension geometry, it will only affect the angles of the axle shafts/cv joints (and ground clearance under the engine).

Raising the torsion tube would be what alters the suspension geometry.

I have an IRS car that is lowered more than is the preference on this board (it also has the trailing arms flipped for the zero camber look)...and it would benefit from a tranny raise.  The angle on the CVs is awful.  ...but I do like the stance.

(http://i110.photobucket.com/albums/n90/Flipper_1938/HPIM0242.jpg)

Would a raise in gearbox & engine height improve the centre of gravity of the car at all (make it any more stable at the top end of the strip)? Or is the 1-2" we're discussing here not enough to make a noticable difference?

I thought lower center of gravity was supposed to be better.

But it allows the car itself to be lower... ;)

I think it¨s easy to make a mental bobo when we are referring to the procedure as a gearbox raise. What we are doing is lowering everything except the gearbox (keeping the wheels straight), and that's the gain in centre of gravity.
On a IRS car you don't have to change a thing, but you still get a "better" result...  just lower the car and the gearbox and engine also goes down... and the wheels stay straight... (might need some clearance around the spring plate to allow enough arcing) (and that engine might be hitting the ground)  ;) 

When you are lowering a IRS you get a benefit that dont excist in a swingaxle car.