Chassis rub blocks

[Roy Ranquist]

  Rooman I have to fabricate rub blocks for my chassis before I race again.In your opinion what should they look like under the chassis?

[rooman]

Roy,
       when I was involved in that arena the big show guys used a block with a big radius on the leading edge and most mounted them in double shear but I have some left over stuff from when Snake shut his operation down that mount to a flat tab that is parallel to the ground plane and tangential to the bottom of the frame rail. The block is tapped from its top surface. I have them in aluminum and also in UHMW. I also have some of the big radius ones in Ti that have a single lateral tab on the top surface but I guess that you would need plenty of ground clearance to run them unless you like bright sparks 

Roo

[janjon]

Anyone care to explain the purpose, placement, etc of rub blocks? I guess I could guess... but I've never seen or heard tell of such.
Thanks.

[rooman]

Anyone care to explain the purpose, placement, etc of rub blocks? I guess I could guess... but I've never seen or heard tell of such.
Thanks.

On big show cars they come in handy if one (or both) of the rear tires make an exit during a run--it can reduce the need to replace the lower frame rail/s. On anything else they can also be a benefit if there is a shortage of ground clearance and the car is flexible enough  to put the lower rail on the ground on a rough track/shut down area (or in the pits at some places I have been to).
 Usually placed at the mid plate on a big show T/F, at approximately the front seat upright area on a funny car and just ahead of the motor on a front motor car.

Roo   

[dreracecar]

The down side to them is (If the engine is out too far) is they tend to pound and beat up the lower rail because they take up space and reduce the ground clearence that would normaly be present

[Greg H]

What would be a good number on ride height? Front to rear... Some rake in the chassis.


 

[rooman]

Apart from needing whatever ground clearance is necessary to be able to navigate the pits and return road at the tracks that you race at "ride height/chassis rake" is not relevant. What is important is the overall package--how far out the engine is and how high it is mounted usually being the primary factor.
 Just about any combination can be made to work if the tires, clutch/converter, horsepower and torque are all in sync. Some people swear by slip joint cars (usually the ones with the engine behind the driver    ) and some of those same guys like suspension as well but (within reason) you should be able to get just about anything to go down the track by finessing the combination.
  My cars are normally have about 3.5" clearance at the front axle and I like 4" plus at the mid plate although in a lot of cases the oil pan is lower than that and the limiting factor.

Roo

[Greg H]

Good input......Thanks!