Roll Cage Specs

[ADAM]

hi guys, i am going to put in a roll cage this winter...does anyone have a link of book that shows what a race approved cage should look like, and the materials and such?

[RedRabbit Racer]

Adam - assuming you want something suitable for CASC-OR racing you should check appendix 'O' of the 2002 Race Regulations. posted on the CASC website.

[Dave]

Adam, CSC Racing in Newmarket (905) 954-0520 builds cages and they're familiar with the Solo 1 and regional road race rulebooks. If you go with DOM mild steel (which is the least expensive and most common material used for cages), according to section 2.3.10 of the Solo 1 Rulebook you'll need to use 1.750'' (diameter) tubing with a .120'' wall thickness. I don't think CSC works with Chromoly (alloy), but if you want to go with Chromoly cage, which is more expensive than DOM but also substantially stronger and you can therefore use smaller diameter and wall thickness, resulting in a lighter cage, you'll want to give Ronnie at O'Brien Motorsports in Brampton a call at (416) 604-0477. For your car, you'd need to use 1.625'' diameter tubing and .095 wall thickness in chromoly to be Solo 1 legal. Ronnie built my cage in chromoly a few years ago and he also did all the Sentra series cages. He can also build you a cage in DOM if you prefer it from a cost perspective.

Either of these shops know how to build you a strong and CASC legal rollcage. You can specify how you want the cage laid out to a certain extent, but obviously things like the main hoop can only go in one location. I think your best bet is to go to one of these shops and tell them what you're looking for (DOM vs Chromoly; super-strong vs weight saving; nascar door bars vs simple x door bars; etc.) and they'll deliver what you want within the rules you plan to compete under.

[ADAM]

hi dave,
can i ask what he charged for the cage?

so far i have my roll bar in .125 thou steel, for the main hoop..so i would build off that..

[Dave]

so what's the diameter of your roll bar? I'm sure it's probably at least 1.75''.

Ronnie at O'Brien Motorsport is more expensive than CSC Racing, but his welds are cleaner and he fits the cage tighter to pillars and roof than CSC does. You'll definitely lose more interior space with a CSC cage than an O'Brien cage, but that may not matter much to you. A CSC cage will be about $1500 and an O'Brien cage will be about $2200 or so. Prices do vary depending on the car (ie. if they've done a S13 240sx before it means they've got a blueprint and it's easier/cheaper for them to build another).

[Bubblecar]

Quick point about Chromoly.

When I put a cage into my Talon, two years ago - CASC advised me that you still had to make it the same diameter as mild steel and since it is actually heavier (weight saving comes from smaller diameter) you end up paying more and not gaining an advantage.
As well, appearantly it is more difficult to properly tech a chromoly cage.

Rules might have changed since then, but I think even in the SCCA, few are using chromoly.

Nick

[GR8 Ride]

Nick,

The Chromoly cages actually have a thinner wall, hence the reduction in weight over the mild steel cages.

Ronnie does build an excellent cage, and his price differential from mild steel to Chromoly is about $500 total.

There are two schools of thought on the cages, both in SCCA and Club Racing perspectives. Some guys swear by the lighter weight, other guys prefer the thicker walls of the mild steel cage, swearing it's stronger.

Personally I'd say go with whatever version fits your budget. If you can swing the Chromoly, then do it. Resale value as a potential race car will increase somewhat with Chromoly compared to mild steel.

If you'd rather spend the $500 on something else, you won't lose much going with mild steel.


Pat

[Bubblecar]

Yes Pat,

but the point is that both CASC and SCCA require that the thickness of the tubing be the SAME - whether made of mild steel or chromoly.

Therefore the advantage of chromoly that you can structurally have a thinner wall is not allowed.

If you make a chromoly cage with thinner walls - the value of your racecar would not increase - but could well go to zero - if it doesn't meet specs for either SCCA or CASC.

Nick

[Dave]

Nick, the CASC Race Regulations clearly state the following (which I have cut & pasted from the online rulebook found at www.casc.on.ca):

Race Regulations 2002 - Appendix O

3.1 The roll cage shall be of seamless or ERW or DOM mild steel tubing (SAE 1010, 1020, 1025) or equivalent, or alloy steel tubing (SAE 4125, 4130). It is recommended that mild steel tubing be used as alloys present difficulties in welding and must be normalized to relieve stress. Proof of the use of alloy steel is the responsibility of the Entrant.

3.2 Unless otherwise specified herein, the minimum size of tubing to be used shall be as follows: (all dimensions are in inches).
Car Weight Mild Steel Alloy Steel
Up to 1500 lbs. 1.375x.095 1.375x.080
1500-2500 lbs. 1.500x.095 1.375x.095
Over 2500 lbs. 1.500x.120 1.500x.095
Or 1.750x.095

ERW tubing may be used in the following sizes only:
Car Weight ERW tubing
Up to 2500 lbs. 1.500x.120
over 2500lbs. 1.750x.120

3.3 For purposes of determining tubing size, the Car weight is as raced, without fuel and Driver.

3.4 The minus tolerance for wall thickness shall not be more than .010 below the nominal thickness.

3.5 An inspection hole of at least 3/16in diameter shall be drilled in a non-critical area of all tubing with a specified dimension, to
facilitate verification of wall thickness.

So as you can see, in the case of my 2,000 lbs Civic I am in fact within the rules having used a 1.375'' diameter and 0.95'' wall thickness alloy (chromoly) tubing, where had I used mild steel I would have been required by the rules to use 1.500 x 0.95 tubing. So you can in fact use smaller diameter (and in some cases thinner walled) tubing should you opt to use chromoly instead of mild steel should you be racing under the CASC rulebook. However, the SCCA has banned chromoly cages though they do allow cars that have chromoly cages that predate this rule change to compete.

In the case of Nick's Talon, he did indeed have to use the same diameter tubing but he could have opted to use chromoly and saved weight via the thinner wall thickness required for cars over 2,500 lbs. How would this have saved weight? Read on.

FYI, ERW stands for Electric Resistance Welded and this is a mild steel that is made from a flat sheet, rolled up into a tube and welded. DOM stands for Drawn Over Mandrel. This tubing is actually ERW tubing that has gone through an extra step to even out the imperfections and make it stronger. Chromoly is an alloy of steel which incorporates both Chromium and Molybdenum in the process and is stronger still. The benefits of ERW tubing is simply that it is less expensive. The liabilities is that it is not as strong and therefore you need to use a larger size tubing than either mild steel or chromoly.

Finally, and most importantly, size for size ALL steel weighs roughly the same. In other words, chromoly is not heavier than mild steel. What is true is that chromoly is stronger than DOM and DOM is stronger than ERW. Therefore, some sanctioning bodies allow you to reduce the size of the tubing as you go up in strength, as is the case with the CASC as clearly seen in Appendix O of the Race Regulations.

[Dave]

In terms of weight savings, here's a chart from Unorthodox Racing's website:

Chromoly Vs. Mild Steel - Weight Difference:
Cage Type------------Weight Savings
4 point cage---------->15.5 lbs. lighter
6 point cage----------> 31 lbs. lighter
8 point cage----------> 62 lbs. lighter
10 point cage--------> 77.5 lbs. lighter
12 point cage--------> 81.37 lbs. lighter

FYI, chromoly (depending on the type) has roughly four times the tensile strength of mild steel, as indicated by the numbering system used. Mild steel is usually 1018 but can range from 1010-1020. Chromoly is 4130 or 4140 and is just that much stronger. The higher the number the higher it is in tensile strength and the stiffer the material is.

4130 still remains flexible but not so rigid that it snaps. It has "memory" which mild steel does not. Mild steel tubing bends very easily and it will stay bent, whereas 4130 has quite a bit of memory and it will flex, bend and come back to where it is supposed to be.

On the other side of the issue, chromoly welds are much more susceptible to cracking, particularly if the grain structure has not been re-aligned thru a stress relieving process known as 'normalization'. The reason chromoly has been banned by the SCCA is that too many yahoos have tried to build their own chromoly cage without understanding the normalization process and how to achieve this. However, with modern welding techniques such as cold welding and TIG welding, properly performed by a professional like Ronnie, normalization of welds is easily achieved.

[B18C5]

Nice slew of info d00d! The weight savings may or may not be somewhat misleading though. For my car I found that to meet CASC requirements I needed a cage with either 2.00x.095 chromoly or 1.75x.120 DOM tubing. I found a website here:

http://www.auto-ware.com/techref/tubeweight.htm

...which gives the weights of different sizes of tubing. It turns out that the tubing for chromoly weighs 1.933 pounds per foot and the tubing for DOM weighs 2.089! Definitely not worth the extra trouble and expense in my case.

OTOH, if I was building a cage to meet SCCA or NASA rules only, then I could get away with different weights and sizes. I think weight savings would be a little more in that case.

[Dave]

For my car I found that to meet CASC requirements I needed a cage with either 2.00x.095 chromoly or 1.75x.120 DOM tubing

Huh? Geo, do you mean SCCA? I posted the CASC regs above and your numbers don't jive with them. I know from the NASA regs (checked them before we went to the OTC) the specs are as follows for cars over 2500 lbs: 2.25 x .120 in mild steel or 2.00 x .095 in alloy (chromoly). For my car (1500-2500 lbs) the NASA alloy specs are 1.625 x .095.

SCCA GCR Section 18 has the following specs for rollcages:
1501-2500 lbs. 1.75 X .120 in mild steel or 1.625 X .095 in alloy
Over 2500 lbs. 2.25 X .120 in mild steel or 2.00 X .095 in alloy

Where are you getting your numbers, Geo? They don't seem to coincide with CASC, NASA, or SCCA.

Anyway, off the top of my head I seem to recall 60-100 feet being needed to build a full roll cage, so lets say you need 80 feet for a really nice cage in your ITR. Using the CASC minimum specs, a mild steel (1.5 x .120) cage would weigh 141.52 lbs and a chromoly (1.5 x .095) cage would weigh 114.08 lbs. That's a savings of 27. 44 lbs. To some that may seem like small potatoes, to others looking for that last tiny edge over their competitor it may seem like a lot. It's all a matter of priorities I guess :)

[B18C5]

WTF? Something is either weird or I'm wired. The specs I posted were right off the Solo 1 rulebook. I guess it's different than CASC's specs. I just assumed that Solo 1 cage specs would be the same as race specs, since cages aren't required for Solo 1. Weird. I wonder where those specs came from...

The NASA ones are me being wired because I remembered the Solo 1 regs being stiffer (no pun intended). Hrmph. I guess I'm either going to have to get my car down to 2500 pounds or use bigger tubing to be able to run in ECHC. DAMN THE WORLD!!!

[Dave]

HAHA! Geo, you've identified an error in the Solo 1 rulebook I've never noticed before! You did quote the Solo 1 specs, but we got the weight ranges for chromoly wrong. I'll bring this to the attention of Christian and Perry and we'll work it out. I think it's safe to assume that a cage that meet CASC Race Regs as outlined in Appendix O of the GCRs should be good enough for Solo 1. But of course in your case, with OTC and ECHC to consider, building a cage that meets CASC, SCCA, and NASA spec is a bit more of a challenge. Looks to me like NASA and SCCA actually have the same specs and CASC allows smaller diameter tubing for the same weight ranges. Interesting...

BTW, Appendix O of the Race Regulations is actually a very interesting read. Have a looksee at http://www.casc.on.ca/files/2002RaceRegulations.pdf and go to page 55 of the document

[B18C5]

Damn. Are you referring to section 4.1 which states: all cars shall be neat and clean. Cars which are dirty... will not be approved for competition.

DAMN THE WORLD!

Well, I guess I gotsta put in a beef-fest of a hardcore booyaka heavyweight cage. I guess kinda like Alec's thickness (of his cage I mean). Well, better tank than sorry I guess.

NASA has a similar document. I think it's just in the GCRs or something. It may even be more specific than the CASC GCRs about cage type and method of building and all that shizznit. It's pretty nutzo. I think it's here:
http://www.nasaproracing.com/rules.html
...under the Club Codes and Regs (CCR) section. I think. It's somewhere in there. Very interesting shizznit...

[Bubblecar]

Dave, Pat, etc.

I stand corrected! (Damn - that's the fifth mistake I've made in my life!) :D

When I caged my Talon, I wanted to work with SCCA specs, and when speaking with CASC Chief Tech, I was very much dissuaded from using chromoly.

Nick

[Dave]

Geo, I've just realized our mistake with regards to the Solo 1 rulebook. Section 2.3.10, which you used as your source for rollcage tubing diatmeter and wall thickness, is actually for ROLL BARS, not full rollcages. If you go on to Section 2.3.21 of the Solo 1 rulebook, you'll see that in the case of full rollcages you are told to refer to the CASC GCR's Appendix O. So we've come full circle my friend :)

However, I have been told that there's a very good chance CASC will revamp their rollcage specs this winter (perhaps to align with what we see in SCCA and NASA), so if I was you I'd wait to see the CASC 2003 specs before making any decisions on cage size.

Dave

[Dave]

Nick, is one of those 5 mistakes driving a Nissan instead of a Honda???? :eek: Hehehe....

Seriously though, it looks like you made the right choice to use SCCA specs since CASC seems to moving in that direction anyway. Hope they don't expect me to cut my chromoly cage out of my car!!!

[GR8 Ride]

Well, at least ONE of those mistakes was buying a Nissan 350Z instead of a new BMW as a track toy.... ;)


Pat

[GR8 Ride]

Well, at least ONE of those mistakes was buying a Nissan 350Z instead of a new BMW as a track toy.... ;)


Pat

[GR8 Ride]

Originally posted by Dave
Geo, I've just realized our mistake with regards to the Solo 1 rulebook. Section 2.3.10, which you used as your source for rollcage tubing diatmeter and wall thickness, is actually for ROLL BARS, not full rollcages. If you go on to Section 2.3.21 of the Solo 1 rulebook, you'll see that in the case of full rollcages you are told to refer to the CASC GCR's Appendix O. So we've come full circle my friend :)

However, I have been told that there's a very good chance CASC will revamp their rollcage specs this winter (perhaps to align with what we see in SCCA and NASA), so if I was you I'd wait to see the CASC 2003 specs before making any decisions on cage size.

Dave

Dave,

I've been searching both the SCCA rulebook and the NASA rulebook, and I find no mention of the banning of chromoly / alloy steel cages for 2003.

Can you provide any links on this? I'm having this debate with several people in both Canada and the US, and nobody seems to know much about the SCCA banning chromoly cages?


Pat

[Dave]

Pat, I've just spoken to a contact I have at NASA head office (National Auto Sport Association) and he tells me that the SCCA has not banned chromoly and there are no plans to do so. In fact, chromoly is widely used by racers who run with the SCCA and NASA. However, as of January 2003 the only materials allowed will be DOM and Chromoly tubing. ERW will no longer be permitted. For a description of what ERW is, read this entire thread :) I posted a good rant about somewhere in here.

I actually contributed to the rumor that chromoly was going to be banned because I was confused what ERW meant (thought it meant chromoly, which is doesn't). My bad!

Dave

[turboawd]

Anyone use Autopower rollcages. They seem to have a good reputation and prices seem reasonable but after shipping and US exchange... ?