Piecing together a custom roll bar

[Dubstep Shep]

Though most of what I'll be doing will probably be open track days.

 

[neema]

Though most of what I'll be doing will probably be open track days.

NASA runs open track days (HPDEs) with their race events, and there are still a set of rules that apply when you want to install a roll bar or cage. Notably, sections 11, 15.5, and 15.6.

Have a look: http://www.nasaproracing.com/rules/ccr.pdf

 

[Sky Render]

Regardless, you don't "piece together a custom roll bar." This isn't a turbo kit; you can't buy some used parts here and there and just throw them all together.

You either buy a roll bar/cage you bolt/weld in (like the Maximum Motorsports one), or you take your car to a qualified shop and have them build one into your car, to your specifications.

What, exactly, is wrong with the Maximum Motorsports unit, anyway, especially since most of what you'll be doing is open track days?

 

[Dubstep Shep]

Regardless, you don't "piece together a custom roll bar." This isn't a turbo kit; you can't buy some used parts here and there and just throw them all together.

You either buy a roll bar/cage you bolt/weld in (like the Maximum Motorsports one), or you take your car to a qualified shop and have them build one into your car, to your specifications.

What, exactly, is wrong with the Maximum Motorsports unit, anyway, especially since most of what you'll be doing is open track days?

By no means do I plan on buying "some used parts here and there" and just throwing it all together.

My intent was to combine the good design features from multiple designs into my own applications.

This is a custom bar, no doubt about it. But some of the components will be bought pre made. That is where the "piecing together" comes in.

Chief reason I didn't go with MM is that it doesn't tie into the shock towers.

 

[NoTicket]

From what I understand, CM is more rigid than DOM, just like you said, to achieve a similar level of rigidity, you need less material.

However, DOM will bend when pushed past that limit, and CM will just fracture.

Maybe I'm mistaken. But I believe any flaws in a DOM cage will be less catastrophic than a CM cage because of the ways in which both fail in extreme conditions.

 

[Dubstep Shep]

From what I understand, CM is more rigid than DOM, just like you said, to achieve a similar level of rigidity, you need less material.

However, DOM will bend when pushed past that limit, and CM will just fracture.

Maybe I'm mistaken. But I believe any flaws in a DOM cage will be less catastrophic than a CM cage because of the ways in which both fail in extreme conditions.

I would have to do more research into the material properties to knows, but I'm not sure that's right.


Basically any material has two types of deformation; plastic and elastic.

Elastic deformation is when the object returns to it's original shape when the load is removed.

Plastic deformation is when the object is permanently deformed after the load is removed.

The thing that's great about all metals is that they go through elastic deformation, then plastic deformation, then fracture or breakage.

The extent to which the elastic and plastic areas extend depend on the material. For something like cast iron, which is very brittle, the elastic area is small. For something like steel, it's much larger.

I would have to look up the material properties of CM and DOM to know for sure, but I seriously doubt that the elastic deformation range will be smaller for CM.

So I talked to Patrick at Watson Racing and he was extremely helpful.


Basically they offer a couple of options.

Their road race cage for of the Boss 302 S/R isn't compatible with the OEM interior, so it's a no go.

They do, however, make the Cobra Jet cages that fit inside the OEM interior and are CM. They're drag cages though, and mount to the spring towers and third link rather than the shock towers.

The other think he mentioned was a shock tower brace that's essentially the same design as their road race cage from the Boss. He said it would be the perfect point to build a bar from or to just brace the coilovers.


I'm gonna dig a little deeper, but what I'm thinking at this point is buying the Watson shock tower brace and using it with a x-brace design. I may see if I can get a main hoop, diagonal brace, and harness bar from them as well, then have the x-brace done at a shop.


As for the CM vs DOM, after a good amount of research, it seems like DOM will be the way to go simply because it's more accepted. Kudos to those that said that earlier.

I haven't decided on bolt in vs. weld in yet. I may weld the gussets in near the B pillars and the shock tower brace in the rear, then make the rest of the cage detachable. Much like the MM design. It would make installation MUCH easier as well.

 

[SoundGuyDave]

Just keep an eye on your load-paths! If you're going to try to land the back-stays on the rear shock mounts (good but not essential), you'll need to build up a plinth box around the mounts, then weld your back-stay to that, along with any lateral bracing you may want. If you're starting from scratch, the MM bar would make a pretty good "donor base" to begin with, and if you have the fab skills to do plinth boxes, grinding off the backstay stubs from the MM bar and relocating them would be a piece of cake...

 

[Dubstep Shep]

Just keep an eye on your load-paths! If you're going to try to land the back-stays on the rear shock mounts (good but not essential), you'll need to build up a plinth box around the mounts, then weld your back-stay to that, along with any lateral bracing you may want. If you're starting from scratch, the MM bar would make a pretty good "donor base" to begin with, and if you have the fab skills to do plinth boxes, grinding off the backstay stubs from the MM bar and relocating them would be a piece of cake...

Good idea.

I think the Watson shock tower brace has a pretty good setup as far as mounting around the shock tower. I'll have to post up the picture they sent me later.

 

[modernbeat]

So, you say you want the roll bar to tie into the rear shock mounts because you are going to a coilover suspension in the rear. That's a good idea. But you didn't say why you are going to a coilover. In my experience there are very few benefits and lots of drawbacks. And once you get away from using a coilover, the Maximum rollbar becomes a good off-the-shelf unit. Add a couple extra bars if you want (we sometimes do) and you have the rollbar that will work well.

 

[Dubstep Shep]

So, you say you want the roll bar to tie into the rear shock mounts because you are going to a coilover suspension in the rear. That's a good idea. But you didn't say why you are going to a coilover. In my experience there are very few benefits and lots of drawbacks. And once you get away from using a coilover, the Maximum rollbar becomes a good off-the-shelf unit. Add a couple extra bars if you want (we sometimes do) and you have the rollbar that will work well.

Simply put because it's a better system than a shock and spring for road racing.

The why is a little more complex than that, and there are plenty of people that are more knowledgeable than me on the subject, but results speak for themselves. I'm running Griggs racing suspension for a reason, and that reason is it gets results.

Here are the pics of the shock tower brace btw:

 

[csamsh]

Simply put because it's a better system than a shock and spring for road racing.

The why is a little more complex than that, and there are plenty of people that are more knowledgeable than me on the subject, but results speak for themselves. I'm running Griggs racing suspension for a reason, and that reason is it gets results.

Aw come on...humor us with some tech

 

[csamsh]

Also, hello there! I'm in Edmond.

 

[Dubstep Shep]

Aw come on...humor us with some tech

Hahaha I'll resist sticking my foot in my mouth right now.

I didn't see the article on Griggs website, so it must of been one that he emailed me. I'll have to go digging to see if I can find it.

 

[csamsh]

Just throwing this out there...there's a pretty successful Mustang shop about 2.5 hours south of you...

 

[Dubstep Shep]

Just throwing this out there...there's a pretty successful Mustang shop about 2.5 hours south of you...

In Dallas? What's their name?

 

[Sky Render]

In Dallas? What's their name?

Vorshlag...

www.vorshlag.com/contactus.php

Sent from my toilet using Tapatalk

 

[Dubstep Shep]

Oh snap. Didn't know they were that close.

I'm going to try and find something a little closer before I go that far, but if not I'll hit them up.

 

[csamsh]

Oh snap. Didn't know they were that close.

I'm going to try and find something a little closer before I go that far, but if not I'll hit them up.

You won't find anything. Be careful though...Vorshlag can be bad for your bank account.

 

[Dubstep Shep]

You won't find anything. Be careful though...Vorshlag can be bad for your bank account.

My engine builder recommended several builders here in OKC. One of them did his car. It runs a sub seven second quarter mile.

 

[Dubstep Shep]

I didn't know Vorshlag did custom cage work though?