Help With Base Plates For Roll Cage

[jamesjedi]

Hoping that I can get help with my Safety Devices Roll Cage. As always, I appreciate any help given.

It is a bolt in style.

I have fabbed up some base plates. My concern is; are they going to be big/strong enough? The front part of the cage base plate is realatively small. The base plate for the main hoop in larger, but it is at a curved part of the chasis. They are 3/16 mild steel. I am hoping that the picture shows the curvature of the chassis steel. The base plates are not curved.

Any help would be super.

[aftermath]

The rules for your race class should dictate the size and thickness of base plate material. No harm in going bigger. I would for the front ones for sure as they look pretty small.

[jamesjedi]

Thanks for the reply.

Can I put a gusset plate underneath the brackets I made?

I think the nut plates from Safety Devices are very small.

[armandodiaz]

Just curious, what are you using to bend the plates?

[jamesjedi]

I had a shop bend the steel. To say that I "fabbed" them is a bit of an exaggeration. I have been shaping them in an attempt to get them to fit. I may have to trim part of the feet for the cage and weld it in. It may be the only way to get it to fit properly. It has been frustrating.

[Pete R]

As mentioned, your cage requirement will vary with vehicle weight and organization in which you are running. I would review the rules of all the series that you may want to run with and build them to the most strict requirements. You will not ever be penalized for overkill on safety equipment. Welding and bolting will have different requirements too. No one here will be able too tell you what's required with out knowing what you are doing with the vehicle.
If you are just asking in general (since most full racing organizations don't seem to allow bolt in cages anyhow) the last thing I read on bolt ins was not thinner that 3/16 and at least 3 bolts per pad. You need to have an equivalent backing plate on the other side of the body as well.

[Walt Fricke]

Bolt-in seems always to require a thicker top plate, plus an equivalent backer plate. 3/16" seems the norm there. That is (or was) the SCCA spec, and just about every amateur organization at least starts with some of the SCCA's work and long experience.

If the cage is welded to the plates, they can be considerably thinner. SCCA, as I recall (you should check) is 0.080" minimum. And they have a maximum for some reason. So 1/8" plate would do fine. And no backing needed.

You may be overanalyzing here - if the plate is welded in, and is 3/16", it will take a pretty hard hit directly down (as in flying into the air, turning upside down, and coming down with a large vector normal to the ground) to push that plate down from where it is welded. And then it will, before it moves enough to cause your head and neck to be squashed, come into contact, so it will be as strong as if it were contoured to within a thousandth of an inch.

So if you have 1/8" of void space, is the roll hoop being 1/8" shorter going to have an effect on your protection?

Though perhaps I am overlooking some kind of dynamic effect or something?

If these plates aren't to be welded in, then you won't gain approval from anyone who requires a roll bar or roll cage, because you can't get backing plates into place. At least not without cutting sheet metal, inserting plate, somehow bolting together, and then welding up the hole you made. All of which is silly.

But maybe I don't understand. To me a bolt-in cage usually has the hoops bolted to the floor, so to speak, and the rear braces to a wheel arch - both of which locations can easily be accessed from below.

In your case, are you going to weld nuts under these plates (below the holes), and then bolt the stock base plates of the cage assembly to them? I don't know if any rules directly address this, but you can argue that you are basically a weld-in cage, as the base - that which takes all the various forces - is welded in. And your bolts are strong enough for the bolted specs. So why isn't this going to be strong enough.

Me, I'd do two things first: I'd call Safety Devices to check to see what they think, and what they think about this passing Venue X's rules. And I'd contact the appropriate person in Venue X to see what they have to say.

I also think that the idea that a track prepared car with modifications as serious as a cage is ever going to be returned to cageless street configuration (and stiff springs, bushings, etc removed) is wishful thinking. Doesn't seem to happen.

[jamesjedi]

All good points. Thanks for the help.

The Safety Devices cage has to use nuts welded to the back side of the base plates, due to their placement on a boxed section of the car (the main hoop). Unless it is welded in. They would have to be long bolts to go all the way through the car. Autopower cages bolt to the floor.

I will talk to Stable Energies today.

[armandodiaz]

Have you seen the "Wheeler Dealer" episode of building a 951 track car?

They installed a bolt on rollcage to the frame rails. What they did was fab backing plates, weld on nuts to the backside. Then drill over-sized holes on the frame rails, where the nuts would recess into. Once the rollcage is loosely installed they welded the brackets to the frame. Finally tighten everything.

Seemed like a pretty good idea.

[andrew15]

Originally Posted by armandodiaz

Have you seen the "Wheeler Dealer" episode of building a 951 track car?

They installed a bolt on rollcage to the frame rails. What they did was fab backing plates, weld on nuts to the backside. Then drill over-sized holes on the frame rails, where the nuts would recess into. Once the rollcage is loosely installed they welded the brackets to the frame. Finally tighten everything.

Seemed like a pretty good idea.

This is exactly what I did when we installed a safety devices cage in my 911.
I wasn't happy with the smaller mount plates sent, so a friend and I made up a set that fit the metal around the mount points well, and drilled oversized holes to clear the welded on nuts. Once everything was in place we tacked it and removed the cage to weld up everything.

AM