Fixing bent door strut brackets

[flux3d]

Sorry, last question I promise......both of the fixing points for the struts on the frame are bent slightly and have been like it since I got the car. I know this is a sign that at some point either the torsion bars were torqued too much, or more likely in this case a bad batch of struts were used and have pushed the fixing brackets outwards. This seems to be likely as both sides show pretty much exactly the same amount of movement outwards.

What's the best way of fixing this? I was planning to make a new L shaped bracket that would be fitted to the roof section for added support, but this seems a bit more involved than I thought it would be. Has anyone tackled this and have any wisdom?

[SteveyP]

Yes, I had the door mounting bracket pull away from the fiberglass surround on my drivers door (see attached pics)

Chris Nicholson at PJ Grady had to repair the fiberglass, and then manufacture a nice support bracket to make sure it would never happen again.

Steve.

[flux3d]

Hi Steve,

I think Chris pointed out your car when I was last down and how I needed to do something before mine needed the same treatment. I'm thinking of using a similar type of bracket.

[SteveyP]

Yes, Chris did say it was fairly common problem. He did a great job anyway. Thankfully she's nearly finished now, should be picking her up in the next week or so.

Steve

[Darren C]

Déjà vu….

Common Fault, I’ve made several of these brackets in Stainless Steel. The one in your picture Steve, looks far too thin to not deform under the doors weight. I'm sure it will easily bend again in time

Here’s a solid Brushed Stainless one I made for Andy D.

[flux3d]

lol, I was just posting on the other forum about needing one of your creations Darren after Andy D posted about his experiences and success with the one you made for him.

Small world!

[stunned_monkey]

If you need any monobolts, I had to buy a bag of 100 in order to fix the brackets on one car. Also useful for fixing the roof back down when it comes unstuck and starts bowing upwards. They're what Rob Grady has been using for years.

[Darren C]

Hi Mark,

PM me if you still need a bracket

Martin,

The key to a successful repair is using a "strongback" (backing plate) when fixing to fibreglass. Bolts, Rivet-nuts, Screws, Pop rivets or just a nut and washer behind will eventually tear out of the tub under stress.
Consider the original oval backing plate, even though its 2" long and an inch wide with two bolts they eventually tear through the tub to give you the problems we're experiencing. I have very little faith in a glass patch up job, the tub is too thin and the pressure and stress too localised at the strut point to make a good, long lasting repair this way. Glass fibre repairs are never as good as the original where the resin set as a complete item, repairs always have shear points where old meets new.

Pressure= Force over Area

Increase the area (using a larger or second backing plate) and the pressure is reduced. Combine this with placing the strongback over a good undamaged part of the tub, rather than just a local glass repair around the original damage and you should have a long lasting solution.
Relying on a bolt or rivet-nut is going the other way as you are still focusing point loads. Granted 100 rivets would be fine, but not practical.
The angle bracket repair some use is a similar example of the physics but NOT good since it holds up the cover trims around the aperture, promotes water leakage (around the bolts/screws put in vertically) where water naturally sits or looks an eyesore if placed over the trim.

[stunned_monkey]

Darren C Wrote:The key to a successful repair is using a "strongback" (backing plate) when fixing to fibreglass. Bolts, Rivet-nuts, Screws, Pop rivets or just a nut and washer behind will eventually tear out of the tub under stress.

I wasn't suggesting that the monobolts could be used in lieu of anything else on the strut mount, but like all rivets (monobolts are basically giant pop-rivets), they're very strong in shear but pretty rubbish under tension and especially cyclic tension loading. P=F/A is only part of the story, what needs to be done is to massively increase the area over which the moment applied by the strut mount acts on the underbody, and we've both done it the same way; by putting a large boomerang-shaped steel bracket across where the original mount was. The fibreglass doesn't even need repairing as such as long as it's sealed. I use bond & seal (aka Sikaflex) which over a large area is evil-y strong in addtion to four monobolts to hold the new bracket in place.

The roof can be fixed down along the rear edge simply by using monobolts.

As for the "not if but when" scenario on original strut mounts, i disagree. Most failures are caused either by the mount being placed too near the hinge when originally fixed at the factory, or the use of struts which were too long. DMCH many years ago made this mistake and prompted this review which showed how the "closed" length was too long. Note: this report is now over 10 years old.

http://lukesandel.com/auto/delorean/inf ... arison.pdf