Failed Shock Mount

[Seymour Snerd]

I'm sure that a U shaped brace would great, but bending a somewhat thick piece of steel is beyond my skill set. By the way how thick a piece of steel should I use?

I'm not all that sharp when it comes to steel. How does brazing differ from "welding". Also, is the GT40 tub brazed, welded or maybe both?

No worries, either method will work. If I were just making the triangular plates I'd probably use 1/8", probably overkill, but you want to do this only once. This means you might have to lengthen your bolts by as much as 1/4".

Oh, wait: the width at the crossmember and the width at the shock are different on the front side; hence the gentle fold in the original. So now you are eighter bending your plates or your are spacing them away from the shock mount. OK I guess. Use a stack of washers?

I'd really like to hear what "the factory" has to say about this. But a fix like the above will certainly get you on the road again.

Sidebar: The technical definition of brazing is joining two pieces of metal, not necessarily the same material, by melting a dissimilar metal (eg steel to brass with silver). In the case of the GT40 that would be joining steel to steel with bronze. Welding, OTOH, is joining two similar pieces of metal by melting them together, with or without the addition of melted metal of the same kind. Typically steel is joined to steel with the addition of steel "filler", but you can join steel to steel just by melting them both together. So spot welding is an example of the latter.


How you decide whether to braze or weld in any particular situation, and what you use as a filler metal, is somewhere bertween a long magazine article and a batchelor's degree subject

I don't know the total answer for the SPF tub, but I know that there is a mixture of spot-welding and brazing. If you take a file or some sand paper to any of the "welds" you see and it looks bronze colored, it's brazed.

 

[Jim Craik]

Alan,

Thanks for the info.

Yes, I'll wait until we hear back from SPF.

In the mean time, thanks for the info on plate thickness, I'm thinking of bending them to match the shape, instead of spacers.

 

[Jac Mac]

Looks more like its been spot welded & mig welded, hope it has not been brazed, that limits you to also doing the same in the repair without an extensive 'brazing material' removal exercise. I cant help feeling there is a 'missing element' in the manner that bracket has been made, either in material or the welding itself which BTW has considerable room for improvement!

 

[Pat]

Jim, first I'm glad you're safe. Had this occurred in any sort of g-loaded corner, it could have been a mess.
Have you done any crack testing on the other mount? The issue may be systemic. It also looks a little like a fatigue crack so perhaps the harmonics of the swaybar contribute to the problem. So it may be a thought to put some polyurethane bushings in the swaybar mount.

 

[Jim Craik]

Veek,

Yes, I think Steve called the problem, with the sway bar mount adding just a little twist to a fairly lightly constructed area, add to that the higher than typical mileage and I got a fatigue crack!

We were very lucky, if the whole mount had failed on the way home, Skyline is a fast mountain Highway with fast sweepers.....................Frances was with me

I'm considering moving the sway bar mount away from this area like Steve did, but either way I will reinforce both sides.

 

[Pat]

Veek,

We were very lucky, if the whole mount had failed on the way home, Skyline is a fast Highway with fast sweepers.....................Frances was with me

I'm considering moving the sway bar mount away from this area like Steve did, but either way I will reinforce both sides.

Steve's work looks great and looks like a super solution. One other thought, while you have things apart, you may want have your shocks put on a shock dyno to make sure they are operating properly. You should be able to find a high-end race shop with a setup to do that. It will insure that it's not contributing vibrations to the problem.
I hope Frances didn't lose any enthusiasm for '40 rides! Debby and I try to go out most weekends but we have over 10K to catch up to you.

 

[Seymour Snerd]

Jim,

Take a look in the SPF Forum Page 1 under "Upgrades & Mods to P2125

Look at pics in posts 51 and 52 for how my sway bar is connected and the strengthening plate that helps support the shock mount ect.

Helpful?

Steve P2125

PS: Just looked at Dimi's post above....His suggestion is similar to what we did at time of P2125's original build;added the pate as shown

Steve --

Isn't there a little more going on with yours than just strengthening the original design? It looks to me like your mounting scheme was intended to fix an intereference problem by shifting the anti-roll bar to the rear in order to clear the transaxle mounting ears on your custom transaxle top-plate, and your exhaust system, and that it needed to be strengthened in order to deal with the increased twisting moment produced from moving the anti-roll bar; IOW your initial requirement, moving the anti-roll bar, made the twisting worse. I just ask because I vaguely remember either Paul or Dennis O mentioning having to do this.


IAE the "right" solution is to move the bar up on top so there is no twisting, like the actual GT-40s did (Mk I and Mk II). All these plates and things are bandaids.

And, by the way, this goes on the SPF deviations list in a rather prominent place as a definite downgrade unless someone can produce a picture of an original GT40 that has an anti-roll bar mounted to the end of its shock bolt.

 

[Seymour Snerd]

Looks more like its been spot welded & mig welded...
....there is a 'missing element' in the manner that bracket has been made, either in material or the welding itself which BTW has considerable room for improvement!

Mine is spot welded and brazed.

I think the missing element was in the brain of the person who decided to perch the anti-roll bar pivot out on the end of the top shock mounting bolt, thus requiring a nice light double-shear structure entended to take only vertical loads to now take twisting loads for which it was not designed. IOW somebody tried to do a "Colin Chapman" but without the genius.

 

[Jim Craik]

Alan

I'm not sure about the mods you mentioned, is far as I can tell, the sway bar mounts are as built. Additionally, although I did not do the instal, I am not familiar with a custom transaxle top plate.

As far as deviations, what it is is what it is. It's a GT40, built under licence from Safir.

Acording to what I have read, only the cars up to P1049 were built under licence for Ford. After that Ford sold the rights, assets and remaining parts to JW Aotomotive and they then sold them to Safir.

So with some exceptions, all cars built from P1050 on were built not by Ford, but by the owners of the rights.

The Safir Mk5 tubs were much simplified by Len Baily (the South Africa tubs are much closer to the Abbey Panels tubs) and the Holman cars were built by John Holmans son, long after his death and also have "deviations".

So as far as I can tell, all cars after P1049 are cars built by folks who bought the rights from Ford and they are all slightly different.

What I have is a Gt40 built just as the Wyer/Safir/Holman cars were, under licence from the rights owner, and they are all slightly different.

 

[Pat]

For what it's worth, here are the treaments of the Alan Mann car AM GT40/2 and the Gulf Mirage.

 

[Jim Craik]

Mine is spot welded and brazed.

I think the missing element was in the brain of the person who decided to perch the anti-roll bar pivot out on the end of the top shock mounting bolt, thus requiring a nice light double-shear structure entended to take only vertical loads to now take twisting loads for which it was not designed. IOW somebody tried to do a "Colin Chapman" but without the genius.

Alan,

I totally agree, the design is simple, light and elegant, very Lotus like. Additionally Mr Chapman was a genius, but I seem to remember many of his light and elegant designs did also fail, with considerably less than 28,000 miles

 

[Seymour Snerd]

I'm not sure about the mods you mentioned, is far as I can tell, the sway bar mounts are as built. Additionally, although I did not do the instal, I am not familiar with a custom transaxle top plate.

That's all about P2125, Steve's car. Hence the post starting with "Steve:..."

As far as deviations, what it is is what it is. It's a GT40, built under licence from Safir.

Acording to what I have read, only the cars up to P1049 were built under licence for Ford. After that Ford sold the rights, assets and remaining parts to JW Aotomotive and they then sold them to Safir.

So with some exceptions, all cars built from P1050 on were built not by Ford, but by the owners of the rights.

The Safir Mk5 tubs were much simplified by Len Baily (the South Africa tubs are much closer to the Abbey Panels tubs) and the Holman cars were built by John Holmans son, long after his death and also have "deviations".

So as far as I can tell, all cars after P1049 are cars built by folks who bought the rights from Ford and they are all slightly different.

What I have is a Gt40 built just as the Wyer/Safir/Holman cars were, under licence from the rights owner, and they are all slightly different.

I know all that, I have one too. I'm confused, why do you bring that up here?

 

[Seymour Snerd]

For what it's worth, here are the treaments of the Alan Mann car AM GT40/2 and the Gulf Mirage.

Yes, both showing the implementation described in the parts book.

 

[Seymour Snerd]

Alan,

I totally agree, the design is simple, light and elegant, very Lotus like.

Uhhh... I didn't say that... and I don't agree at all. IMO the GT40 design is complex, heavy and elegant, and not at all Lotus like. Chapman's proposal was along the lines of the Europa.

But we're way off topic.

 

[Jim Craik]

Alan when I first looked at your post, I'm pritty sure the "Steve" was not there, hence my thinking you were speaking to me.

I see that you edited your post 22 minutes after you first posted, Alan is it possible that you might have added the Steve after the first post? I know I'm always changing my posts.

 

[Jim Craik]

That's all about P2125, Steve's car. Hence the post starting with "Steve:..."



I know all that, I have one too. I'm confused, why do you bring that up here?

Alan, you said

And, by the way, this goes on the SPF deviations list in a rather prominent place as a definite downgrade unless someone can produce a picture of an original GT40 that has an anti-roll bar mounted to the end of its shock bolt. Posted by Alan

I brought it up because of your list of variations, a big "downgrade", the thing about looking at old photos and how the sway bars are mounted on the "actual cars".

The cars are all different, even all the "actual" cars are different from each other.

You will never find the "correct" GT40, because it does not exist! If it did, all the cars would look like that.

Like i said, what it is is what it is. Our cars have a provenance of their own and nuances in their design.

I guarantee that 30 years from now, the Jackson/Barret guys will be talking about whether or not P2264 has the "correct" SPF rear sway bar mount. Just like all cars, years from now the most "original" cars will have the most value.

 

[Jim Craik]

Alan,

As far as the Lotus comment, perhaps I did not say it as I meant to. You mentioned the Chapman genius.

I think that the SPF rear sway bar is light and elegant, Lotus like. Why limit a bolt to one job when it can do two saves the weight of one bolt and one mount. Very elegant and I think very Lotus like.

And like Lotus sometimes the light, elegant designs were too light.

 

[Jim Craik]

And, by the way, this goes on the SPF deviations list in a rather prominent place as a definite downgrade unless someone can produce a picture of an original GT40 that has an anti-roll bar mounted to the end of its shock bolt.

posted by Alan

I took a quick look through the book "The Ford That Beat Ferrari".

There is a photo of P/1031 on page 142, a MKII at Le Mans In 1967, light blue #57. It shows the sway bar mount off the rear of the shock mount.

Additionally on page 169, a MKIV, J-8, i know it's not the same, but it just shows what Holman & Moody were doing back then.

 

[Seymour Snerd]

I we're going to discuss the validity of my deviations list let's do it here: http://www.gt40s.com/forum/superformance-gt40s/34278-spf-gt40-genesis.html. I'm sorry I brought it up in this thread.

 

[Seymour Snerd]

There is a photo of P/1031 on page 142, a MKII at Le Mans In 1967, light blue #57. It shows the sway bar mount off the rear of the shock mount.

Additionally on page 169, a MKIV, J-8, i know it's not the same, but it just shows what Holman & Moody were doing back then.

Good, then it's not a deviation in the gross sense.

Here's a closer picture of what is probably that design.



I suspect if Hi tech had implemented that precisely, your car would not have failed as it did. But since they didn't, we'll never know.