289 rear spring

[Rick 427 Cobra]

Any body know of a 289 rear spring for sale or a source?
Cal Metal ,Nedsel , Jim Maxwell? anybody?

[Dan Case]

I needed new front main leaves for CSX2551 to replace ones that were damaged. I made a drawing of what I wanted and Alcan Spring in Colorado made them. (Charles at charles@alcanspring.com) I have not installed them yet but he made them just as drawn so I am confident I won't have any problems. Charles was very easy to work with.

Dan

PS Charles is the only person I could find that would make parts to a print. A very well known in the old car hobby shop said they could not, they had to have an exact sample, and.....they did not warrant that what they might make would fit!!!!!!!!!

[Rick 427 Cobra]

I may have found a used set, F & R. I only want the rear. Any interest?
Re Alcan, how much? I do not have a drawing that I have faith in currently. The drawings that are floating around all seem to vary slightly. Slightly doesn't cut it with nonadjustable suspension. I would like to have a new spring in hand before I tear the car totally apart.
I am anxious to see how your spring works out.
Thanks for the contact

[Dan Case]

I did my own reverse engineering from precise measurements of parts from several cars, information from the original chassis manual, the current owners of AC Cars library, and published old interviews with SAI fabricators. I did completely detailed drawings on AutoCAD® software for the two leaves I needed created. While I was at it I got shorter leaves to change front wheel camber. The two leaves delivered were just under $250 custom made.

I got quotes from a couple of places in this country that have done a version of leaf spring chassis or sell parts for same and AC Cars. None of them would put in writing their part would fit an original chassis. AC Cars was the only one that claimed the eye to eye dimensions (measured in flat state) was the same as original. I don't have the old messages anymore but the difference in eye to eye among these places was almost two inches. If you do the math something like 0.03" difference in length might affect camber half a degree per side so two inches in variation is a lot.

The car seems to have a Dragon Snake front spring in it as it was longer eye to eye and shallower in free camber. It was also bent and the caster was no doubt off too. The front wheel camber was severe and the handling in anything but a straight line off compared to what I am use to.

[mloy]

Originally posted by Rick 427 Cobra


I may have found a used set, F & R. I only want the rear. Any interest?
Re Alcan, how much? I do not have a drawing that I have faith in currently. The drawings that are floating around all seem to vary slightly. Slightly doesn't cut it with nonadjustable suspension. I would like to have a new spring in hand before I tear the car totally apart.
I am anxious to see how your spring works out.
Thanks for the contact

Rick, I would be interested in the front spring. How much are we talking in price? My email is markloy at verizon dot net

Thanks,

--Mark

[mloy]

Kirkham sells both springs, FIA specs @ $300 per spring including the bronze bushings. That was what Tom quoted me a month or so ago.

Motorsports International has them listed for $269.95, FIA specs.

Rick, I would be interested in both springs if the price was right and you did not want the rear.

--Mark

[mloy]

Originally posted by Dan Case


I needed new front main leaves for CSX2551 to replace ones that were damaged. I made a drawing of what I wanted and Alcan Spring in Colorado made them. (Charles at charles@alcanspring.com) I have not installed them yet but he made them just as drawn so I am confident I won't have any problems. Charles was very easy to work with.

Dan

PS Charles is the only person I could find that would make parts to a print. A very well known in the old car hobby shop said they could not, they had to have an exact sample, and.....they did not warrant that what they might make would fit!!!!!!!!!

Dan, funny how small this world is. I was talking to Charles about getting a set made for my project at the same time you were working with him on the leaf.

--Mark

[Rick 427 Cobra]

The K bros spring is VERY stiff, not what I want. MSI may list them, but they do not have them. I haven't got a price yet on the springs. I'll let you know.

[mloy]

Originally posted by Rick 427 Cobra


The K bros spring is VERY stiff, not what I want. MSI may list them, but they do not have them. I haven't got a price yet on the springs. I'll let you know.

Rick,

Thank-you. I appreciate it.

--Mark

[Dan Case]

Mark / Rick,
One of the reasons the replacement leaves from Alcan were expensive was material thickness. The original steel gage AC Cars used is virtually obsolete now. I did www check outs of companies all over the world that advertise making automobile suspension springs (most seem to be in India????). I forgot to mention that Charles was the only person I found in my many contacts that would even discuss obtaining raw material in the original gage. He was familar with that gage as some other antique vehicles also require it. The "big boys" in springs (the high volume folks) would not talk about using a gage they could not buy in bulk cheap. I tried.

I was really surprised at the lack interest that Eaton displayed. They are highly praised in the old car and custom car world. I was told via e-mail point blank they considered it an unreasonable demand to make springs to a drawing with dimensions and tolerances to be held. Go figure.

[Rick 427 Cobra]

Proper gauge material! Now you really have my attention. This is one of the things that McCluskey mentioned when I called him. He was talking about going to England for springs. That's key to spring rate. Properly tapered and end treatment?
Do you have any drawings for a rear? My drawing calls out 41.5" c/c, spring " flat". 40" c/c with 4.75" c/l to bottom spring relaxed.
All leaves .219 with a taper to .156 at the ends. 7 springs total.
Alcan's price sounds good for the correct spring.

[mloy]

Originally posted by Rick 427 Cobra


Proper gauge material! Now you really have my attention. This is one of the things that McCluskey mentioned when I called him. He was talking about going to England for springs. That's key to spring rate. Properly tapered and end treatment?
Do you have any drawings for a rear? My drawing calls out 41.5" c/c, spring " flat". 40" c/c with 4.75" c/l to bottom spring relaxed.
All leaves .219 with a taper to .156 at the ends. 7 springs total.
Alcan's price sounds good for the correct spring.

Interesting, very interesting.

While the AC Cobra Chassis manual states the 41.5" eye-to-eye dimension on the rear spring, it does not clarify whether or not it is along the spring itself or eye-to-eye across when “relaxed.” The plans I have show the 41.5” dimension eye-to-eye when relaxed and not the distance along the spring. The dimensions were supposedly taken off an original Cobra back in the seventies. I have twice thought that the dimensions shown on other items on these plans were incorrect only to be proven wrong both times. That is not to say that these dimensions shown cannot be wrong, however. The plans I have also show 7/32” spring material for the rear leafs, which is .219” in thickness. The issue comes with the front spring which has (by my plans) the main leaf at 7/32” in thickness and the rest 3/16” which is supposedly not available anymore. This stands to reason why pictures of SAI and Kirkham cars have fewer leafs shown on their front springs.

Since I have an original style front upright, I can plot the camber curve for different front spring dimensions and see what is what for that spring. I, at this time, cannot do it for the rear as I do not own the rear uprights.

I am inclined to believe that the 41.5” dimension is eye-to-eye when measured with no load on the spring (relaxed) for an original car. If someone can provide good solid tech why this is not the case, I am all ears.

Now with all this being said, a shorter spring would seem to benefit the car as I understand that negative camber was hard to come by on the original cars. How much shorter, I do not know at this time.

[Rick 427 Cobra]

No go on the used spring set. back to square one. I talked to MSI and had them check their drawings and once again we have a difference in specs, particularly in amount of arch.

Dan
Do you still have the spec that you sent to Alcan? What kind of spring rate? I would love a copy for comparision sake.

[mloy]

Originally posted by Rick 427 Cobra


No go on the used spring set. back to square one. I talked to MSI and had them check their drawings and once again we have a difference in specs, particularly in amount of arch.

Dan
Do you still have the spec that you sent to Alcan? What kind of spring rate? I would love a copy for comparision sake.

Bummer on the used set.

Who is MSI?

Thanks,

--Mark

[mloy]

Nevermind, MSI = Motorsports International.

[Dan Case]

Eye Center Free Chamber
To Eye Center Camber
(inches) (inches)
Front
AC COBRA CHASSIS INSTRUCTION BOOK 39.250 3.250
Shelby Automobiles, Inc. January 2005 37.000 Not Available

Rear
AC COBRA CHASSIS INSTRUCTION BOOK 41.000 5.313
Shelby Automobiles, Inc. January 2005 39.500 Not Available

Notice: How much different eye to eye the two sources are. This was the case with all sources of replacement parts too. I do not have their messages anymore but I believe the current owners of AC Cars offered these same eye to eye dimensions as the original chassis manual but the gage was thicker (and very expensive!!!!).

The average leaf thickness front (several cars measured) is 3/16” (0.188 - 0.190 actual). This gage is for practical purposes obsolete. There is no gage taper, the leaves are constant, as constant as the hot roll process can make, gage end to end.

The average leaf thickness rear (several cars measured) is 7/32” (0.218 – 0.221 actual) There is no gage taper, the leaves are constant, as constant as the hot roll process can make, gage end to end.

I did a lot or research, hours a day for weeks, on original leaf springs. I had help from several other owners in various parts of the country that have cars in some stage of restoration. I had multiple contacts with AC Cars, Shelby Automotive, Motorsports International, and my fellow owners.

I am grateful several owners took time from the activities to remove their springs and make measurements. One pair of people even made a fixture to hold the whole spring assemblies out horizontal for measurement with large calipers. I dismantled my springs and used a 4X4 section and clamps to flatten the springs against my steel work bench. All my measurements were multiple readings made starting completely over at least twice (multiple days, multiple set ups, five readings each minimum, all measurements averaged).

Some things became clear.

1) The eye to eye dimensions in the AC COBRA CHASSIS INSTRUCTION BOOK (AC) are for the two main leaves while they are still straight prior to heat treating into an arc or finished leaves held out flat along their top surface tangent to the rolled ends afterwards.

2) All the front springs (or rear springs) measured were very consistent in eye to eye centers except CSX2551 (which I am working on). CSX2551 had a longer set of front main leaves, perhaps Dragon Snake length as they are reported to have special longer front springs. The front camber on CSX2551 made it look like an old tractor.

3) It was very common for the center clamp bolt (runs through the middle to hold leaves together) to be considerably off center. This surprised us. We had assumed you could center the bolt in the clearance hole in the spring tower and you would have even side to side control arm (the springs being the upper control arms) length. Not true. One spring was found to be 0.120” off center, not good for an alignment gage. Range found was exactly in center to 0.120 off center. This confounded me enough to gather tools to measure the location of the clearance holes in CSX2551’s spring towers. After much work I got five sets of measurements and averaged them. The average offset for each was 0.000”, at least they were in the center. They must have been jigged for drilling as getting that accuracy on a fabricated weldment otherwise would be tough.

4) No two front (or rear springs), comparing one car to another, still had the exact same free camber or exactly matched AC. This is probably due to each individual chassis’ use history. The variance was not large.

Specific dimensions of leave width and width at ends were they fit into their uprights depends on what the dimensions are of the mating parts. Wear also is important. About 1991 I had exact copies of the Vandervill brand thrust washers made in 660 bronze bearing material except for thickness, I had parts made nominal, in +0.005, and in +0.010 so I could fit to eliminate slop due to wear or process variation.

[mloy]

Dan,

Got it.


--Mark

[Dan Case]

Oh yeah. The original spring eye bushings are standard plain bearings shortened by 0.01".

Wheeler WC 913-16 Bronze
9/16 X 13/16 X 2.00 cut down to 1.990 length and installed with a
0.5675 diameter polished pilot tool

[mloy]

For my memory when I draw this up...

Simple circular curve geometry on rear spring:

LC = (Long Chord) eye to eye when spring is curved = 38.0545"
R = (Radius) = 36.7302"
L = (Length of Curve) actual leaf length = 41"
M = (Middle Ordinate) free camber = 5.3125"



--Mark

[tnewland]

Hello Rick, just got back from vacation so I'm late to this thread. Sorry, but maybe I can still help. We talked at the last COCOA event at Willow Springs; I've got the BRG FIA CSX 7030. And thanks for the help with the T-5 tailshaft issue and muffler clearance situation.
Anyway, as you may know from our talk. I've also got spring issues. I'm currently on my second front spring (modified). So far so good. I have no plans to change it.
Just before Willow I installed a replacement rear spring from Shelby because the original just wasn't supporting the car through anything other than the flattest intersections. All too often the spring was slapping the gas tank hold-downs and bending them over. So far I haven't noticed any damage to the square tube above the spring.
Because I question the steel quality of the Shelby spring, I decided to beef it up to the extent that I could by adding the longest leaf from the original spring to the replacement spring. To keep the stack height the same, I removed the uppermost short leaf. On my car, there's only room for eight leaves. So far it's holding up.
Now for your situation: you might want to talk to (Shelby Dealer) Lee Benson at All Pro Motorsports in Pennsylvania @ 570-546-4800. He's tracking some cars and is going to a NASCAR spring supplier for replacements. I hope this helps. Tom