Roll bar thru the cab questions

[Chassisman]

Pretty much geometry.. How angles and curves react with force upon a spot..
To play and test your theory, gas weld coat hangers in your roll cage configuration, then mimic the roll or crash forces..
It will bend easy.. If it doesn't.. Then you have a strong cage.. But the point is it bends easy enough to observe what happens thus you can figure if your set-up will work..

I have a 1/24 scale 14 point chassis built out of 11/32 rod....you can stand on it.....actually put 500lbs on it .....no bend...no collapse....use it to show clients how I built stuff....

[Deaf Bob]

^^ that is the way to do it! But how do you see " give". ??
Bet that conviences guys pretty darn quick!

[ChampTrucking]

THANK YOU CHASSIS MAN. I knew the collective intelligence on this forum could help! Thanks to all of you.

[Chassisman]

^^ that is the way to do it! But how do you see " give". ??
Bet that conviences guys pretty darn quick!

...years of building cars has given me an eye for where weak spots are in chassis design....I've fixed a lot of ill handling cars over the years. Chris Alstons Chassisworks used to send me the worst of the worst....I cut one tube on a 63 Nova 3x2 chassis car...the car twisted far that a 2" gap opened up with a pow as the portaband cut through it......

[Chassisman]

THANK YOU CHASSIS MAN. I knew the collective intelligence on this forum could help! Thanks to all of you.

Glad to help.....glad years of trial and effort keep other people from struggles from weighing them down on projects.

[milner351]

I'd love to see that model chassisman - that sounds very cool.

In your opinion - is there a "kit" cage that is worth buying?

[Chassisman]

I'd love to see that model chassisman - that sounds very cool.

In your opinion - is there a "kit" cage that is worth buying?

No "kit" is perfect.....but....any kit that uses one piece sides (not a halo with A pillar bars) is a good kit. Ive built ever manufacturers kit out there over the years.....thats why in 1994 I became a dealer for Chris Alstons Chassisworks.....no one else in the industry uses automotive industry modeling software.....Chassisworks does.....Chris is also responsible for a lot of safety innovations that are SFI approved. He's been on the board of directors for years. His swing outs are the NHRA standard ....they wrote the rule based on his testing of the swing out. I know this sounds like a commercial for Chassisworks. ...but I've seen them all.....and they are the best for the do-it-yourself kit guys.

[milner351]

What's your opinion on removable (pinned like swing outs, or bolted) horizontal bars between the two down legs of the main hoop?

For my falcon - I only want that bar in there when I'm racing - not when my 3 year old is getting in and out of his car seat in the back.

[Chassisman]

What's your opinion on removable (pinned like swing outs, or bolted) horizontal bars between the two down legs of the main hoop?

For my falcon - I only want that bar in there when I'm racing - not when my 3 year old is getting in and out of his car seat in the back.

Removable seat bars on the main hoop are not legal for the NHRA. ...if your running quicker than 11.50 you'll need a legal bar or cage(on a side note...I do not install rol bars....only 8 point cages and up.....a roll bar doesnt keep a roof out of your lap if you roll down the top of a rail).I've built some pro street cars with removable seat bars.....made the customer sign a statement acknowledging it will not pass tech. Chassisworks sells the kit to do that.....its your call.....good luck.

[milner351]

I totally see your point and respect your expert opinion - I want the safety at the track - and was thinking 8 point if I do it at all.

This car will never see the low side of 11.50 in it's current configuration - I'd be happy as heck to get into the 11's at all.

I'd rather be kicked off a track with a removable bar if I do go faster than 11.50, than not be able to use the car on the street.

[Ron Ward]

I totally see your point and respect your expert opinion - I want the safety at the track - and was thinking 8 point if I do it at all.

This car will never see the low side of 11.50 in it's current configuration - I'd be happy as heck to get into the 11's at all.

I'd rather be kicked off a track with a removable bar if I do go faster than 11.50, than not be able to use the car on the street.

I see a couple flaws in your logic. I'm not trying to be a jerk, but rather, I'd like to point out a couple things that just don't jibe with each other.

First, if you plan on using a 5-point harness, you'll need to have the crossbar behind the seats installed to mount them correctly or they could cause severe injury.

Second, you stated you want "safety at the track." Getting kicked off because you are violating a safety issue is rather contradictory, no?

I'm in no way telling you how to build your car, but I think with some thought and input from folks like Chassisman, you can come up with a safe installation that will pass tech AND be compatible with young rear seat passengers.


Ron

[milner351]

Thanks Ron - and sorry to hijack the thread! I truly appreciate all the input - I've never had a car with a cage - I'm sure that's obvious!

It's a confusing subject to me, I'm a mechanical engineer and tend to over build things and be overly conservative on most set ups.

I would like to have 8,10,12 point from the chassis stiffness and safety standpoint, however - the last thing I want to do to this car is make it a pain to operate on the street... I want it to be a street car first, and everything else second.
That's why I'm going with Mark 8 seats and console, air conditioning, tilt column, modern stereo, and an over drive auto.

I have to keep an eye on the budget - dropping the shell off at a chassis shop for a full on .083" 4130 DOM custom bent cage is most likely way way out of my budget. I have an HF tubing bender - but have not had the best luck with it. I have a tig welder - but tigging a cage in all sorts of contorted positions is going to really stretch my skills and more than likely I'd end up Mig welding in the interest of time and my sanity.

A single hoop with rear bars, swing out / removable door bars, and a removable cross bar would be easier from an ingress/egress standpoint - if James can fold himself in and out of a fox body with that sort of set up - I can do the same with the falcon.

However - as Chassisman pointed out - if I do turtle this thing - the factory A pillars aren't going to do much for me.

I'm fine with a 3 point seat belt until the NHRA tells me I have to buy 5 point.
This car didn't come with any belts... so a 3 point is an improvement - the top anchor would be on the cage I'm assuming?

signed,
confused in motown.... LOL

[DanStokes]

I don't know Chassisman's take on this but Bob Self's Ford GT has a beautiful cage from S&W and the whole deal bolts together. It uses machined plugs that slide into the tubing and are then TIG'd into the tube, sort of glad hand style. Each joint has 2 Allen head screws (I'd guess maybe 7/16") in a counterbore. I'm thinking that if you Google the car you might find a pic. That car has been thru ECTA and, I think, SCTA tech many times and I can tell you Joe Timney is STRICT - as he should be. No clue if NHRA would like it or not but that might be a good solution.

If you find a pic please post..........

Dan

[milner351]

can't find any still shots but here's a video

http://www.youtube.com/watch?v=SxXUy68GANY

[Chassisman]

I don't know Chassisman's take on this but Bob Self's Ford GT has a beautiful cage from S&W and the whole deal bolts together. It uses machined plugs that slide into the tubing and are then TIG'd into the tube, sort of glad hand style. Each joint has 2 Allen head screws (I'd guess maybe 7/16") in a counterbore. I'm thinking that if you Google the car you might find a pic. That car has been thru ECTA and, I think, SCTA tech many times and I can tell you Joe Timney is STRICT - as he should be. No clue if NHRA would like it or not but that might be a good solution.

If you find a pic please post..........

Dan

....NHRA accepts no bolt together cages/bars period. All insecting joints must be mig or tig welded.