44-Year-old Cobra Wins Street Car Challenge

[ERA Chas]

Bruce,
Your info sharing is most appreciated by me. Believe me, I did not imply a pi$$ing contest with Morris. Both are superb examples of what could be done in two different technical areas.
Continue to press the envelope but please share all the progress (except the deep dark secrets), with those of us who really are students of the technical side.
Thanks,

[twobjshelbys]

Originally Posted by Jamo

If you ever get a chance...

Bruce's Cobra is beyond belief. I got a chance to chat with him about the suspension changes during the Belmont Concours, and it is nothing less significant than when shelby messed with the front of the early Mustangs.

Great to see a true living Cobra, evolving through its life as it should. Even more so when the owner is a true gentleman.

You're right. Anyone who takes an original Cobra out for a beating like this deserves our respect. I think the same thing of the cars at the Shelby American Collection. On any given weekend, one or more of them may be out for vintage racing. Not as much now as a few years ago, but still happens.

The Murray brothers think like this: We put it back together once, we can do it again. [Remember, race cars get no penalty for repairs. I expect one that hasn't been wrecked doesn't know the limits.]

[D-CEL]

Thank you so much for responding.

When I saw the drive pulley, integral with the crank spacer I assumed it was from Aviaid, sorry LOL.

Yea those old “open bridge” Superlites are… in a word… Crappy! While I was the Quality manager at Wilwood (several years ago) we received a lot of complaints, we built a test rig that measured pedal travel and input force, clamping force and caliper flex in several different axis. Eng attempted to fix it, but in the end, the whole caliper was redesigned into the current SL series that is very stiff. I run the SL-6R on the front of my SPF with a 12.75x1.25 rotor.

I’m certainly sorry to see you switching to Baer…

I would never be so presumptuous as to ask your wheel rates in open forum LOL.

From all the video I’ve watched, the car looks stiffer than the lunch room at Pfizer! And it steers like lightning. The turn in is amazing, almost too quick. I’m guessing it takes mighty powerful arms to turn a cobra like that

[Cobra #3170]

The car has a modified Appleton power steering gear with GM pump, ratio is 12-1 about .95 lock to lock. It is like a formula car for turn in but I run enough toe in that it is quite stable at high speeds. It actually feels like a modern car with a little quicker than normal steering. I have enough Ackerman % that I don't need any static toe out, thus it is stable in a straight line. We played around with boost so that there is still a good deal of "feel" but it is fairly easy to steer. I was well into 4th gear on the straight out of the Carousel at infineon (about 160 mph according to the PI system) and it was very stable even under some really heavy braking. My Wilwoods are about 10 years old now, I am sure their new stuff is much better. I just changed to a more aggressive pad last year which made the Wilwoods a ton better than they were originally. I did notice a lack of initial bite at Infineon which was spooky at high speed (probably a compound issue). I actually overshot the 180 because of that a couple of times, once with a passenger.
The passenger was Dave Wagner, I am sure some of you know him through his Cobra building business. He was a good sport about it, but I would not have liked being in that passenger seat not knowing if we would make the corner or not. I have to admit your 6 piston Wilwoods with slotted rotors look terrific and I am sure perform well too.

Originally Posted by D-CEL

Thank you so much for responding.

When I saw the drive pulley, integral with the crank spacer I assumed it was from Aviaid, sorry LOL.

Yea those old “open bridge” Superlites are… in a word… Crappy! While I was the Quality manager at Wilwood (several years ago) we received a lot of complaints, we built a test rig that measured pedal travel and input force, clamping force and caliper flex in several different axis. Eng attempted to fix it, but in the end, the whole caliper was redesigned into the current SL series that is very stiff. I run the SL-6R on the front of my SPF with a 12.75x1.25 rotor.

I’m certainly sorry to see you switching to Baer…

I would never be so presumptuous as to ask your wheel rates in open forum LOL.

From all the video I’ve watched, the car looks stiffer than the lunch room at Pfizer! And it steers like lightning. The turn in is amazing, almost too quick. I’m guessing it takes mighty powerful arms to turn a cobra like that

[cdnus]

D-CEL

Are the safety wired bolts in your photo left hand threads?

Craig

[D-CEL]

3170,

I thought I saw PS rack hiding in there.. I think about a power rack every time I come home with my arms aching lol.
With that kind of turn in I would have thought it would be a little twitchy , must be amazing to drive, It’s hard (for me) to imagine a Cobra you don’t have to wrestle with.
Wow 10 years! I think new package would yield some big improvements.
That steering arm looks…problematic for a big rotor swap. Is it just an optical illusion or is it really in the way?
Thank you, I’m happy with them. I’m still messing with the M/C’s, F/R bias and pedal ratio. I think they require a little more effort than they should.


Craig,

Yea well NO... LOL
When I was putting it together it up, a friend stopped by to hang out "I’m a pro at lock wire! I can do that"
So I said "Great!!" and moved on..
I was also building my master cylinder/balance bar assembly at the same time and it was giving me fits (not knowing the factory had the pedal ratio at 3.5-1!!)
So a couple of days later, in the midst of staring blankly at the car up on jack stands with the wheels off, I said "DOOOUUUUGHH!!!" lol


Jason

[Cobra #3170]

You are very observant D-CEL, the rotor is so close to the steering arm that I had to radius the inboard face of the rotor along the outer circumference.
I had to repackage the whole deal with the 13" rotors to make it work. I have a reverse hat that moves the rotor as far out as I can and still have adequate clearance from caliper to the wheel inner face. I cheated by reducing rotor thickness .125 to 1 1/8 and moving the wheel outboard .125. I still have my Ackerman with the new set up and don't have the outer tie rod on top of the rotor. I have 1" bore F and 7/8" bore R AP masters with a mechanical bias adjuster that works well with the current calipers, I'll have to see how it is with the new design, efforts have not been bad with the old set up.

I could not drive this car without Power steering now. You should really give it some thought, sometimes the car can do things that you would not believe, if only you could move the wheel fast enough. I also installed a smaller Momo wheel for hand clearance at the door, this really requires PS because of the reduced leverage.

My amateur racing experience is in Formula Atlantic cars so I am really spoiled in terms of steering and brake response this has driven me to try and improve those two areas over the years .

Originally Posted by D-CEL

3170,

I thought I saw PS rack hiding in there.. I think about a power rack every time I come home with my arms aching lol.
With that kind of turn in I would have thought it would be a little twitchy , must be amazing to drive, It’s hard (for me) to imagine a Cobra you don’t have to wrestle with.
Wow 10 years! I think new package would yield some big improvements.
That steering arm looks…problematic for a big rotor swap. Is it just an optical illusion or is it really in the way?
Thank you, I’m happy with them. I’m still messing with the M/C’s, F/R bias and pedal ratio. I think they require a little more effort than they should.


Craig,

Yea well NO... LOL
When I was putting it together it up, a friend stopped by to hang out "I’m a pro at lock wire! I can do that"
So I said "Great!!" and moved on..
I was also building my master cylinder/balance bar assembly at the same time and it was giving me fits (not knowing the factory had the pedal ratio at 3.5-1!!)
So a couple of days later, in the midst of staring blankly at the car up on jack stands with the wheels off, I said "DOOOUUUUGHH!!!" lol


Jason

[D-CEL]

3170,

If i may ask, what spindle are you using? Is there a different steering arm option? Gotta luv Hoerr

Jason

[Cobra #3170]

I made my own because of the critical ratio of upper and lower joints and wheel axis with relation to the chassis. The only thing I regret is not using a cartridge bearing. I started out that way but converting it to a pin drive set up would have taken a lot more time than I had that season. The set up that Kirkham has on their new design is very nice for the bearing and hub. If I were doing it again I would use a lot of their design and just modify upper and lower joint accommodations. I use a 1/2 Stainless NMB Rod end for the upper and a 3/4 spherical NMB for the lower joint. Mounted at just the right angles it gives me 5.5" of total travel with out binding at all possible steering angles, I did limit rack travel to avoid potential clearance issues. One critical design issue is getting the steering arm outer pivot far enough outboard to get the needed Ackerman, that in conjunction with relocating the rack rearward in car gave me what I needed. You can actually push this car at full lock with out a lot of resistance (other than the rear end clutch plates). Try that on a stock Cobra with big tires, you might as well put the hand brake on.

[D-CEL]

I figured the A arms and geometry were yours.
Are the “upright” forgings and steering arm factory Cobra pieces?
Do you use a suspension design program?

Jason

[Cobra #3170]

In the 1970's I bought a spare set of spindles, steering arms, and uprights from Shelby American. I used those as my starting point and modified the uprights and steering arms to get the right package. I actually used a mechanical drawing program to articulate the suspension for roll center location and movement, tie rod end points and length to achieve minimal bump steer. I have used a Ford Motor program in the past that was on the main frame called "Hfronts" that showed me all the weak points of the original design in the early 1980's. I knew pretty much what I wanted in terms of camber gain, toe change, Ackerman, caster, roll center height, antidive, etc. and also how much freedom I had in terms of inboard points so a lot of the input was a given because I couldn't cut or weld on the chassis. I just used the lower inboard pick ups and the tire patch location with respect to the frame and optimized everything else from there. If I were starting with a clean sheet of paper and did not have to preserve the original parts and just bolt stuff on it would have been a lot different. I have a poor motion ratio and that makes it tough to get proper shock control (like the originals). My Ford GT is close to .9 front and 1 in the rear which really helps the shocks do their job vs motion ratios around .6 or .7 especially when you square them.

Originally Posted by D-CEL

I figured the A arms and geometry were yours.
Are the “upright” forgings and steering arm factory Cobra pieces?
Do you use a suspension design program?

Jason

[twobjshelbys]

Just spotted on the Ford GT forum that Optima has invited Bruce back to the Optima Invitational. He doesn't get to drive the Cobra though. 2005 FGT. I wonder what specials we'll see


GOOD LUCK BRUCE!

[twobjshelbys]

Bruce posted his results here:


2010 Optima Challenge Results