Grounded-Broken wing

[athens7]

I killed a cone at 6X MPH this weekend, and pulled the rivnuts out of the aluminum body on the right rear wing. The holes are cratered out, and I'm looking for solutions that don't involve new sheetmetal. Any best practices out there, both for the repair and perhaps for strengthening the body (this is my 2nd right rear wing in 2 seasons-I need a car that is 2" narrower, but only on the right side!)?

[soareyes]

Some of the Stalker guys use these during AutoX's, removable cone deflectors:





Stan

[slomove]

Suppose you have seen that?
These Well Nuts look quite promising.

[Doug Liedblad]

Some have used nylon screws, maybe with a notch to make them break easily. Better than fixing the aluminum.

I pulled several rivnuts out of one side of my car when it was first on the road. I was able to fix them OK but have bought some rubber well nuts for the next time. You can get them from McMaster Carr.

Doug

[magnusfeuer]

I use nylon bolts (bought at Home Depot). I did not take up a notch in them, but that would probably not hurt either.

Would it be possible to use oversized washers to cover the holes and use nylon bolts through the washers?

/Magnus F.

[athens7]

The consensus seems to be well nuts and nylon/polycarbonate bolts-ordered from McMaster-Carr today. Hopefully, I'll be back NOT smashing cones within the week.

[GWise]

Polycarbonate bolts?

I've never heard of those. You'll probably want nylon...

This may be a little more subtle solution. The exhaust tends to block the cones on the drivers side of the car.

[athens7]

Polycarbonate bolts are clear plastic. The guy at McMaster-Carr preferred them to nylon for my application because they were weather-proof and slightly stronger than nylon. The wing is back on, mounted with neoprene rivit nuts. This weekend will afford a shakedown cruise before the next autocross on the 23rd.

I do like the idea of a nerf bar; another item on the projects list.

[Boxologist]

i would go with the nylon or LDPE material. u want the bolt to be the weak link. maybe Tom G has a link to his bolts that he ordered. I have teh mcMaster-carr pages open on my browser at home.

[athens7]

here is the link to the bolts I used:

http://www.mcmaster.com/#93140a184/=365blb

This is their comparison chart for plastic types:

http://www.mcmaster.com/param/html//AboutMachineScrewsPlasticMaterialTypes/default.htm

Clearly, the carbonate is stronger. It is hard to believe, though, that the polycarbonate bolts are anywhere near as strong as the metal ones, and, in humid Georgia, the impervious-to-water benefit is appealing. If I'm wrong, the rubber well nuts should do much less damage to the body than the original rivnuts when they come out.

[GWise]

i would go with the nylon or LDPE material. u want the bolt to be the weak link. maybe Tom G has a link to his bolts that he ordered. I have teh mcMaster-carr pages open on my browser at home.

Let me just preface this by saying you will PROBABLY be ok with your polycarbonate bolts.

You're right, the strength of polycarbonate is considerably (as a rough guess, I'd say 5 times) less than a typical grade 5 bolt. The problem is polycarbonate (and it even says it on that mcmaster table) has good impact strength and is likely 2-3 (again a rough guess) times stronger than nylon. This MAY be enough to keep the polycarbonate bolt from breaking upon impact with a cone whereas a nylon one would break. One thing you can do is notch the bolt/screw so it has a reduced cross sectional thickness to shear through. (Nylon absorbs water, but otherwise they would be fine to use)

Also...be very careful not to spray brake cleaner around these parts. Solvents are great for joining certain plastics parts but they're also good for ruining them as well.

[slomove]

And tighten only VERY lightly. All plastics (and Polycarb especially) are prone to Stress Cracking, that means an otherwise acceptable load may lead to cracks over time, even faster when hot/wet or something is attacking the surface. You don't want that happen on the freeway.

[athens7]

As my car is driven to all events, it spends most of its life on public roads. I worry about the strength of all of these non-metal fasteners over time. I suppose my routine maintenance should now include inspecting/replacing the bolts. I have left the metal bolts in the rear half of the wing, so that the wing will not separate from the body if hit. In both cases when I hit the wing hard enough to tear it away from the body, only the front half came loose and there was no damage to the rear sheet metal, either puckering or panel bending. Accordingly, I am trying this hybrid set up in the hope that it will provide both streetable durability and sheet metal protection when cone slaughtering.

[Elv15]

I've had plastic bolts (actually I think they are nylon) on my car for it's whole life. almost 20K miles now. No problems. You HAVE to be sure that you don't over tighten them, as they are easy to strip.

Also, years ago I saw a very simple but effective cone catcher. Simply a length of square aluminum tubing slightly wider than the width of the fenders bolted under the car by the seat bolts. It was easy to remove for non-autocross driving, but easy to attach when needed. Simple and light - the Lotus way.

[athens7]

You told me so...

Killed 2 cones in a 3 cone wall last Sunday. The Bottom 2 polycarbonate bolts snapped, the next 3 pulled the rubber rivnuts through the aluminum. Nylon bolts, here I come!