427 Cobra rear suspension and Spicer half shafts

[Dominik]

Maybe this helps:

1): closer to 10", as you know all sits at an angle. UCA 3.5 deg. From CR drawings.
2): 12.38" CSX 4000
3): right
4): I would say, no. Depends on your wheel diameter and ground clearance.

The spindle in the upright is at 6.75" above the LCA mount. This brings your outer lower LCA point to: 27.5" wheel / 2, minus 6.75" = 7" above ground. This is dictated by the wheel diameter.

Your ground clearance (to chassis) works out to be 5" (perhaps 4").
The rear inner LCA mount sits sort of 1.5" higher = 6.5" above ground.

Assuming 5" ground clearance, then your differential/axle shaft outlet is 5" + 2" + 5.25" above ground = 12.25"
The center of your 27.5" wheel is 13.75" above ground, which results in 1.5" higher than the axle shaft.


I am curious myself about 9) But this can be calculated using a triangle function.
We need the length of the axle shaft. It's more like 1 mm only.

[my427cobra]

Thanks Dominik. Great info.

But I'm not sure what you did here:

"Assuming 5" ground clearance, then your differential/axle shaft outlet is 5" + 2" + 5.25" above ground = 12.25""

I understand hat 5" is the ground clearance.

What is the 2" and 5.25"?

You're probably wondering what the heck I'm up to.

I'm going down the path that Tom started in a previous posting to use a Corvette C3 differential in a 427 Cobra chassis.

My car is a replica and I am scratch building an IRS for it (just because I like doing that stuff) and wanted help confirming the dimensions.

Another question though.

The Cobra uprights appear to have some castor built in to the UCA mount, but a heim (spherical) joint up there would probably wipe out any castor.

What castor does the 427 Cobra rear upright run at?

I'm about 3/4s done the mock up of the IRS and should have it done in a couple of weeks.

Thanks again for all your help.

Cheers
Greg

[my427cobra]

oh yeah. I forgot to ask about the Spicer half sahfts.

Am I right that on the Cobra the slip yoke (internal splined) goes inboard on the diff side and the yoke shaft (external splined) goes outboard to the upright?

Even though Spicer typically identifies the slip yoke (internal splined) as the outboard component.

Just wondering?

Cheers
Greg

[Dominik]

Originally Posted by my427cobra

Thanks Dominik. Great info.

But I'm not sure what you did here:

"Assuming 5" ground clearance, then your differential/axle shaft outlet is 5" + 2" + 5.25" above ground = 12.25""

I understand hat 5" is the ground clearance.

What is the 2" and 5.25"?

You're probably wondering what the heck I'm up to.

I'm going down the path that Tom started in a previous posting to use a Corvette C3 differential in a 427 Cobra chassis.

My car is a replica and I am scratch building an IRS for it (just because I like doing that stuff) and wanted help confirming the dimensions.

Another question though.

The Cobra uprights appear to have some castor built in to the UCA mount, but a heim (spherical) joint up there would probably wipe out any castor.

What castor does the 427 Cobra rear upright run at?

I'm about 3/4s done the mock up of the IRS and should have it done in a couple of weeks.

Thanks again for all your help.

Cheers
Greg

The addition of: 5" (ground clearance) + 2" (from center of chassis) + 5.25" (to diff / axle shaft center) above ground = 12.25"" is the position from ground of the center of your axle shaft as they are coming out of the differential.

Makes sense? This is from the Cobra Restorers drawings.

Kirkham once posted their ground clearance, which you may want to find and use. Else the 5" shouldn't be far off.

I am still struggling to log in, but I am sure you won't be stranded without my input :-)

On a side note:
Looking from above your rear upright will turn/twist during suspension movement. This is to help corner entry and exit.

Racing Cobras have this eliminated. Their suspension movement is limited and this "bump steer(!)" has no noticeable effect.

It is mandatory to keep it at bay for a street car. Not so much the bump steer itself, which you can't really change, but the static toe setting at ride height. And for this your ride height must be correct...

Did I hear Tom's Motorsport in Vegas who set up Cobras since ever? Look them up?
Or find "Morris" here. He has two brains when it comes to Cobras!

[my427cobra]

Thanks Dominik. You've been a great help.

I plan to set the static toe-in by shimming the LCA at the inner mount.

And to set the static camber, by adjusting the heim (spherical) joint at the UCA at the top of the upright.

I might even figure a way to adjust the anti squat by some adjustment at the UCA inner mount.

Cheers
Greg