sachilles
sachilles HalfDork
2/5/10 2:56 p.m.

Just wondering if there were any articles on cage design. Specifically oriented toward the rally side of things. Getting ready to have my cage done, but would like a better understanding of why some things are done a certain way. Rally america rules, reference FIA rules and site the "web link" below, and there is no web link. They also have a diagram of an example cage. http://www.rally-america.com/info/2008_Rollcage.pdf Yet I haven't seen a cage in a rally car quite like there example. Typically they have an x bar in the door area, where the diagram does not.

Anyways. I'd love to see an article on cage design, and considerations based upon the type of racing you do. Perhaps covering common mistakes and misconceptions.

dyintorace
dyintorace Dork
2/5/10 3:01 p.m.

I'd love to see this article too. It would be helpful if it covered common compromises too (street and track use). By that, I mean a full cage vs. a half/back cage. Weld in vs bolt in would be helpful too.

Adrian_Thompson
Adrian_Thompson HalfDork
2/5/10 3:12 p.m.

Head over to the construction forum on Specialstage. http://specialstage.com/forums/ Once you get past 20 people telling you to buy not build your first rally car there are lot's of cage threads to read and digest, plus lot's of pics to see what people do/have done.

Carson
Carson Dork
2/5/10 3:15 p.m.

There is a TON of cage discussion in the "Car Construction and Equipment" sub-forum on Special Stage for rally cages.

http://www.specialstage.com/forums/forumdisplay.php?f=13

You might find some answers there. The search is good on that site and you don't have to be a member to search.

Carson
Carson Dork
2/5/10 3:16 p.m.

What Adrian said.

sachilles
sachilles HalfDork
2/5/10 4:19 p.m.

Lot's of good info on special stage. Thanks.

HappyAndy
HappyAndy HalfDork
2/5/10 10:30 p.m.

I think a series of articles on cage construction would be great. I say a series because you couldn't possibly properly cover all the different applications that GRM'ers would be interested in in just one or two articles. For example the first article could cover the simple stuff like roll bars for drag cars that are just a bit to fast to run with out them or HPDE cars and hill climbers/AX'ers that still see mostly civilian use. The next eddition could cover propper installation of bolt in cages, stuff that would be helpfull to lemons racers and more serious track toys. The following article(s) could cover cage fabrication for rally and serious w2w use.

Please. I would really love some articles with this type of info, and I think a lot of other readers would too.

vwcorvette
vwcorvette New Reader
2/6/10 7:50 a.m.

TImes eleventy billion

Streetwiseguy
Streetwiseguy New Reader
2/6/10 10:25 a.m.

Other than making sure the tube spec is correct for the sanctioning body, the only real difference I have seen is door bar design. Rally wants to retain easy entry/exit from the car, and the side windows have to remain, and function. That usually means an X with no intrusion into the door ala SCCA/NASA.

My take is that as you move from stock car to road race to rally, you bias the cage less towards collision/intrusion protection and more towards rollover protection.

JoeyM
JoeyM Reader
2/6/10 10:57 a.m.
HappyAndy wrote: For example the first article could cover the simple stuff like roll bars for drag cars that are just a bit to fast to run with out them or HPDE cars and hill climbers/AX'ers that still see mostly civilian use.

+1

I'd love to see an article on how to build a roll bar that would satisfy HPDE requirements on a car that will mostly be street use. It would be especially useful if the article discussed seats, too. For example, is it legal in HPDE (or safe) to retain the stock seat if you want to add a roll bar? What are the differences in roll bar requirements for the different HPDE organizations and clubs? (SCCA, NASA, Chin, etc.) I watched/read this thread from September 2009 on the issue, and it left me with more questions than answers.....

Karl La Follette
Karl La Follette HalfDork
2/6/10 5:08 p.m.

Also include hoops for vert classic cars , various mgb/spitfire /midget setups

JoeyM
JoeyM Reader
2/6/10 5:15 p.m.
Karl La Follette wrote: Also include hoops for vert classic cars , various mgb/spitfire /midget setups

Yes, definitely!

I really hope they do an article....

dj06482
dj06482 Reader
2/6/10 9:01 p.m.

Corner-carvers also has some good cage discussions...

sachilles
sachilles HalfDork
2/8/10 9:05 a.m.

sample question for the article:

This isn't my car, but the cage will be similar. My question relates to the door bars. The door bars form an x. One solid bar, and two smaller bars welded at the intersection. I've also seen the x done as two separate bars bent as V's, welded at the middle, so ultimately it looks like an x as well. Below is a image with the two "V"s.

Just wondering if there is a strength advantage to two bent door bars as opposed to an x that is welded together with straight tubes. Which is better suited should I smack a tree going sideways?

dyintorace
dyintorace Dork
2/8/10 9:23 a.m.

Another good resource is this website: http://www.izzyscustomcages.com/. I've traded emails with the owner on a few occasions and he is both super nice and super helpful.

pmchase
pmchase New Reader
2/8/10 10:19 a.m.

In reply to sachilles:

I'm not a cage designer or structural engineer but I'd bet the gussets on the blue car are way way stronger. They form a box like structure with far more surface area for the welds as opposed to the red car's X.

modernbeat
modernbeat HalfDork
2/8/10 12:27 p.m.
sachilles wrote: My question relates to the door bars. The door bars form an x. One solid bar, and two smaller bars welded at the intersection. I've also seen the x done as two separate bars bent as V's, welded at the middle, so ultimately it looks like an x as well. Just wondering if there is a strength advantage to two bent door bars as opposed to an x that is welded together with straight tubes. Which is better suited should I smack a tree going sideways?

The latter version, with two bent bars, is stronger. It's been endorsed by Mike Hurst, the Rally America technical director. The other version has a weak point where the two short bars are welded to the single bar. At that point the "X" is only as strong as a single bar, and possibly even weaker. The short bars when put into compression may collapse the long bar.

There are other items that could make both of those cages stronger and help egress like moving the front downtubes further forward.

Izzy's Cages
Izzy's Cages New Reader
2/8/10 7:13 p.m.
dyintorace wrote: Another good resource is this website: http://www.izzyscustomcages.com/. I've traded emails with the owner on a few occasions and he is both super nice and super helpful.

Thanks man! I don't get back here very often due to login issues... The biggest thing to keep in mind when looking at cage designs (especially on the web) is that you don't necessarily know what the builder had to take into consideration for the final design.You never know what the customer ultimately wanted done. I've had some requests that many would consider very odd for a racecar.

Read the cage rules and know them well. Talk with your builder and be sure you both are on the same page. A lot of drag builders don't know a thing about NASA/SCCA specs and Rally America has WAY more specific rules. I've seen plenty of people waste money on cages that wouldn't pass tech where they ultimately wanted to run. It's pretty obvious when the builder just builds it the way they always have and never actually look at the rulebook. For the buy vs. build debate, I'm cutting out a cage in about 2 months because of missing welds and poor design in a pre built/logbooked car. Just because the car has competed doesn't mean you don't go over it with a fine tooth comb.

For dropoff, have the seats in position so the builder can place the harness bar at the proper height as well as see where your elbows, lap belts/sub strap mounts etc will be located.

Go with the double bend X over the traditional 3 bar X. Also, add a sill bar. Bars should be backed by other bars at nodes whenever possible. Sometimes, it's not feasable, but it should be the norm rather than the exception.

JoeyM
JoeyM Reader
4/6/10 5:13 a.m.

bump.

this is just a) a reminder that we want this article, and b) a way to get canoes off of the front page

914Driver
914Driver SuperDork
4/6/10 5:58 a.m.

Take a look at the GRM SAAB 99 build. I think they covered the cage retty well, not every available option or "what if" but it's a start.

Dan

kevinSC1
kevinSC1 New Reader
4/6/10 8:52 p.m.
dyintorace wrote: Another good resource is this website: http://www.izzyscustomcages.com/. I've traded emails with the owner on a few occasions and he is both super nice and super helpful.

+1.

Scott is putting a 4-point in my new (to me) Miata.

JoeyM
JoeyM Reader
4/7/10 5:01 a.m.
914Driver wrote: Take a look at the GRM SAAB 99 build. I think they covered the cage retty well, not every available option or "what if" but it's a start.

I'll dig it out and re-read it. I remember something about tieing the cage to the chassis in 30 or so places. I know I mentioned it to Per when he was at the FL State Championships, and I seem to recall that they had the cage made, but cut and welded their own gusset plates to do all the extra attach-to-the-body stuff.

What I'm trying to do is figure out how to prep the datsun replica so that I can use it for autox (and maybe even an HPDE or two) when it is finished. I think the 2.4 liter engine means that I'll be in A-mod.[1] I'll never have the times of a go-kart with a snowmobile engine and a tennis court sized wing, but I will probably be required to have all their safety equipment.


1 - I wish there was a "wimpy streetrod" class. The datsun will have an anemic little L24e engine, in bone stock condition, which means that on a good day it might be capable of 120 hp

modernbeat
modernbeat HalfDork
4/7/10 10:55 a.m.

Back the topic of what Rally America allows as a cage: They allow four different avenues of cage design.

  1. Is the spec Rally America cage. This is the cage illustrated in their rule book.
  2. Is the FIA cookbook cage.
  3. Is the FIA homologated cage.
  4. Is a "free design" cage built to withstand the FIA tests and signed off on by an engineer.

FWIW, building an FIA cookbook cage gives you the most flexibility. A homologated cage will usually be the lightest, but you aren't allowed to modify it or repair it yourself (unless you were the welder/installer or manufacturer).

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