Mike
Lifetime Supporter
spf gt40?
Failed Shock Mount
- Thread starter Jim Craik
- Start date
Seymour Snerd
Lifetime Supporter
Seymour Snerd
Lifetime Supporter
And if so, what did it say? :lipsrsealed:
Alan (and all other SPF GT40 owners with interest in this) Please contact me OFF LINE via email or phone. Please do NOT PM me via GT40s.com.
rick(at)timemachinesauto.com or 716.407.0975 for details.
There are upgrades in the works.
Mike
Lifetime Supporter
I know who Jim is and about his cars. What I'm trying to figure out is how that is relevant to a discussion about SPF specific design concerns other than to hear about the massive down force his cars creates?
Just that hard use can crack shock mounts or sway bar mounts and I'm not surprised that they might have to be re-enforced.
Also you guys are probably running wider and stickier tires that the original chassis were so even more force is being transmitted than on original cars.
I not surprised by stress cracking and think any car you drive at speed might need beefing up and careful inspection. The chassis we cracked on P 4/5 C was Ferrari 430 GT 2 spec and at The Ring the Ferrari 458 GTC also suffered a cracked wishbone. (Factory Part)
Shit happens and chassis crack.
Michael,
Jim was probably responding to a comment Alan said here:
"An hour on typical California broken pavement at street speeds is probably worse than an hour on a track.
Kevin
NYC roads are even worse. They cracked the chassis in my Ferrari TR twice.
Most race tracks are much smoother than the average public road. While the input forces may be higher on the track, the vibration/cycling on the road is much harder on the chassis than track use.
And keep in mind these cars were designed as "expendable" and to "save weight". That they became a road car was incidental to the original design intent. While rules stated that they be "Grand Touring" cars the reality was they are race cars with enough equipment to be road legal-just barely!
Seymour Snerd
Lifetime Supporter
And I was responding to Jim Craik, and I was talking about fatigue where force magnitude isn't necesarilly the most interesting issue, and reinforcement isn't necessarily the correcct solution, and pot-hole depth isn't necessarily relevant.
So just to re-establish the context: this is a thread about a single particular Superformance GT40 replica with 28,000 street miles in Northern California.
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Seymour Snerd
Lifetime Supporter
Rick was addressing that to Jim Craik, the OP and the person with the fatigue, by now probably of both kinds....
Jim Craik
Lifetime Supporter
Rick was addressing that to Jim Craik, the OP and the person with the fatigue, by now probably of both kinds....
Yes, I am very tired
Very scary. Now I know why they call you lucky Jim! I would not be too chuffed to have that happen to me.
Interesting now it's become a "British Design" :laugh:
If I was lucky enough to own one, I would now perform a thorough eyes-on, hands-on, "nut and bolt check" of the entire vehicle. If there's one problem, there may be others. I think you are a test mule mate!
Is yours still in warranty Jim?
Interesting now it's become a "British Design" :laugh:
If I was lucky enough to own one, I would now perform a thorough eyes-on, hands-on, "nut and bolt check" of the entire vehicle. If there's one problem, there may be others. I think you are a test mule mate!
Is yours still in warranty Jim?
Pathfinder Motorsports
Sponsoring Vendor
Pathfinder Motorsports has discussed this issue with our partner Holman Moody and their response was interesting.
The chassis built by Tennant Panels for the GT40 Mk II had several structural enhancements over the Mk I, including the area for the shock mount. Given that our goal is to build true race-ready GT40s, we have specified that future GT40Rs assembled for us by Holman Moody (including the two currently being assembled at Holman Moody) will have fitted a Mk II-style shock mount reinforcement plate.
If any of you would like one or our Holman Moody-built Shock Mount Reinforcement Kits, including a MK II-style plate, mounting hardware, and instructions for installation, we can provide it for approximately $180, excluding shipping. No welding is necessary. This kit is not available from Holman Moody and only from Pathfinder Motorsports LLC.
If you are interested, please contact me at: [email protected].
The chassis built by Tennant Panels for the GT40 Mk II had several structural enhancements over the Mk I, including the area for the shock mount. Given that our goal is to build true race-ready GT40s, we have specified that future GT40Rs assembled for us by Holman Moody (including the two currently being assembled at Holman Moody) will have fitted a Mk II-style shock mount reinforcement plate.
If any of you would like one or our Holman Moody-built Shock Mount Reinforcement Kits, including a MK II-style plate, mounting hardware, and instructions for installation, we can provide it for approximately $180, excluding shipping. No welding is necessary. This kit is not available from Holman Moody and only from Pathfinder Motorsports LLC.
If you are interested, please contact me at: [email protected].
That's great, Alan! Do you have photos? I'm curious as to the 'path' that you guys have chosen! :laugh:
Pathfinder Motorsports
Sponsoring Vendor
Mike:
None of the kits have been fabricated yet as we have no idea what the demand will be, if any.
At present there are two GT40Rs being assembled by Holman Moody for our racing customers, and neither has had the shock mount reinforcement installed. When these parts are fabricated and ready - probably in a couple of weeks - we'll post some photos.
Otherwise, if someone orders a set now, we can photograph and post them sooner.
Alan
Seymour Snerd
Lifetime Supporter
Howard Jones
Supporter
Jim, I read this thread through a couple of times and what I think is this.
1. The material seams to be much thinner than I would have made it if I was using my battleship method. I.E. Make it much much stronger that necessary. If I remade this part It would be 1/8 inch 4130 Chrome molly.
2. I would make it in four pieces welded together inside and out, instead of bending one piece in two places.
3. I would add a second strap across the bottom of the opening of the revised mount that the shock slides into. As wide as shock movement will allow. This will box in the entire assembly. Huge difference.
4. Relocate the roll-bar mount so that it is in double sheer like the pictures above. #68 with a lot more beef. Even if you need to have it trailing the shock location so that you have header clearance carry over the mount to the other side of the bolt with a bridge element.
5. Make the roll bar mount a separate piece so that twisting stress is not transmitted through the whole assembly.
6. One of the side panels of the new mount could be made so that it extends all the way down to the transverse link inboard pickup point, if all three planes are in line. See #34.
7. Lastly, grade 8 bolts please.
They might add a 1/2 pound to the weight of the car...........so what. Wear lighter shoes.
1. The material seams to be much thinner than I would have made it if I was using my battleship method. I.E. Make it much much stronger that necessary. If I remade this part It would be 1/8 inch 4130 Chrome molly.
2. I would make it in four pieces welded together inside and out, instead of bending one piece in two places.
3. I would add a second strap across the bottom of the opening of the revised mount that the shock slides into. As wide as shock movement will allow. This will box in the entire assembly. Huge difference.
4. Relocate the roll-bar mount so that it is in double sheer like the pictures above. #68 with a lot more beef. Even if you need to have it trailing the shock location so that you have header clearance carry over the mount to the other side of the bolt with a bridge element.
5. Make the roll bar mount a separate piece so that twisting stress is not transmitted through the whole assembly.
6. One of the side panels of the new mount could be made so that it extends all the way down to the transverse link inboard pickup point, if all three planes are in line. See #34.
7. Lastly, grade 8 bolts please.
They might add a 1/2 pound to the weight of the car...........so what. Wear lighter shoes.
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The funny thing about stress cracks from cycling is that it can be a (seemingly) completely insignificant thing that starts it. A small ding in the surface from a dropped tool, even just a scratch can start a stress crack....then cycle it across a few 1,000 cycles and boom - failure. Best example is the old Boeing alloy wings - these things could go 1,000s of cycles and not suffer any failures at all. Why? Because the stress loads were very carefully designed to avoid any point loading or small weird little forces. In other words, it doesn't take a big bump or major shock of some kind to start a crack, just a small force or ding....but cycled over a few thousand cycles.....
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