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Cert upgrade to 7.50? Best chassis parts supplier? #3096370
11/22/22 04:35 PM
11/22/22 04:35 PM
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Frostbitefalls MN (Rocky&Bullw...
gregsdart Offline OP
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I plan to upgrade to 7.50 cert. Currently 8.50 cert, with most of the tubes already in place. I need the drivers cage itself, plus tubing for cage gussets, lower between frame rails X brace, and the brace under the bellhousing area . Who has a good web site and INTELIGENT tech guy to work with? I will be fitting the tubing myself , then hire a welder to finish the welding.

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Last edited by gregsdart; 11/22/22 04:37 PM.

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Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: gregsdart] #3096371
11/22/22 04:38 PM
11/22/22 04:38 PM
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Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: gregsdart] #3096392
11/22/22 06:40 PM
11/22/22 06:40 PM
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Do you have a copy of the proper SFI specs and diagram? If not I'm sure that will help you a lot scope up
The funny car cage is needed for sure, is the existing cage mild steel or chromemoly?
I think the main cage has to be chrome moly to be able to certify too SFI 7:50 specs confused scope up


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Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: Cab_Burge] #3096413
11/22/22 08:27 PM
11/22/22 08:27 PM
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Cab, MS is fine for 7.50, and i have the SFI spec book for 25.5D, which is mild steel or CM on rectangular frame rails. My chassis is 1 3/4 ms now. My div 5 tech guy has been real helpful, and rold me five years ago i had everything but rhe FC cage, gussets at the top of the cage, and tube under the bellhousing area. So it is a matter of either finding someone to weld CM at a reasonable cost after i fit it up, or finding a good chassis shop that will supply 1 5/8 x .134 wall tube for the cage.

Last edited by gregsdart; 11/22/22 08:30 PM.

8.77 153 mph best, 3055 lbs 528 indy 440-1 alky
Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: gregsdart] #3096425
11/22/22 09:24 PM
11/22/22 09:24 PM
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Greg your car would fall under SFI 25.4 not 25.5. 25.5 is for stock firewalls and steel floors, both are good to 3600lbs. You need the entire F/C cage how its configured will depend on where your helmet sits in relation to the main hoop. You will need x bars in the floor and a kidney bar and 6C ba(Bell housing area, it can be one piece or three just depends)which can be removable as well. I would suggest ordering a 25.4 SFI spec book and follow it. As for where to buy the tubing, do you have the capability to bend the tube? If so most any big chassis shop can help you. I buy a lot of my stuff from RJ Racecars, but also use MCcamis, Bickle, Rhoades racecars and Tin Soldier. Just depends on what I need.


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Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: Al_Alguire] #3096440
11/22/22 10:23 PM
11/22/22 10:23 PM
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gregsdart Offline OP
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Originally Posted by Al_Alguire
Greg your car would fall under SFI 25.4 not 25.5. 25.5 is for stock firewalls and steel floors, both are good to 3600lbs. You need the entire F/C cage how its configured will depend on where your helmet sits in relation to the main hoop. You will need x bars in the floor and a kidney bar and 6C ba(Bell housing area, it can be one piece or three just depends)which can be removable as well. I would suggest ordering a 25.4 SFI spec book and follow it. As for where to buy the tubing, do you have the capability to bend the tube? If so most any big chassis shop can help you. I buy a lot of my stuff from RJ Racecars, but also use MCcamis, Bickle, Rhoades racecars and Tin Soldier. Just depends on what I need.

My memory is slipping, my SFI book is 25.4d . My goal is to use diagram figure B, Page 16. That allows me to move my seat back a little bit, and i need that as leg room is cramped, too short. It also allows me to not use a bar going forward by my right hip. Which would be in the way of my seat.
Al, thanks for listing those shops. I talked to RJ today. They only have CM kits on the shelf. So maybe i need to find a welder willing to do moly.

Last edited by gregsdart; 11/22/22 10:27 PM.

8.77 153 mph best, 3055 lbs 528 indy 440-1 alky
Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: gregsdart] #3096527
11/23/22 10:56 AM
11/23/22 10:56 AM
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I missed the MS part. Yeah thats a bit tougher to find from most any big chassis shop. We order a lot of tubing from Summit, or here locally from a local steel supplier. Plenty of places have the stuff in stock but not many chassis shops will.


"I am not ashamed to confess I am ignorant of what I do not know."

"It's never wrong to do the right thing"
Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: Al_Alguire] #3096587
11/23/22 02:17 PM
11/23/22 02:17 PM
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On the parachute mount
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WAY better off with CM. i know its hard to get welded at home, BUT a local welder told me to fit it all up, even tack it with my mig. Then i brought the car over to his shop and he tig'ed it for me.
And you can mix CM and MS in the 25.5/25/4 cert


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Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: n20mstr] #3096921
11/24/22 08:30 PM
11/24/22 08:30 PM
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Mine is all c.m. 25.5/7.50 cert. The Tech officials compliment my car every time they recert it. Get a NHRA tech book. Some of the current changes NHRA has made is the funny car cage bars has to be parallel on both sides of driver. Many like to move the outer bar back some to ease getting in and out, no longer legal. Also, the diagonal roof bars have to land 6" from the corner.

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Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: 6PKRTSE] #3097260
11/26/22 12:20 PM
11/26/22 12:20 PM
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Get the SFI book read it and follow it. There are a LOT of ways it can be configured depending on drivers position in relation to the main hoop. Its pretty easy to follow. IMO nothing wrong with mild steel but choose your own material. My Cuda was a 25.4 car all mild steel and worked well. Although it was 100% tig welded, why MS, it was originally a street car.


"I am not ashamed to confess I am ignorant of what I do not know."

"It's never wrong to do the right thing"
Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: gregsdart] #3097329
11/26/22 04:17 PM
11/26/22 04:17 PM
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I stopped looking for sound mechanical/structural engineering proofs behind these rules. Compare crash results (which tubes failed)? Destructive testing of joints in hydraulic press? SAE papers consulted and referenced? GoPro Hero video from inside the car in slo-mo (which failed first)?
Answer came there none,

Just a thought: the relative bending (collapsing) resistance of a tube's unsupported span length is ignored.
A 12" span has almost twice (+96%) the bending resistance of a similar span 15" (+25%) long.
To equal the 12" tube @ 1.75" OD with .120" wall, the 15" diameter must be increased to 2.16", or its wall thickness to .350".
???
Bending resistance varies inversely as the cube (1 รท L^3) of the span length.


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Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: polyspheric] #3097338
11/26/22 05:09 PM
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Poly, those are not reassuring facts, ๐Ÿ˜ณ
Al, i am going with figure B in the proper book, so i can have my helmet position partially under the main hoop. I am going to get the cage kit from RJ racecars, the rest of the tubing locally. Then find a good tig welder to help me finish.


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Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: gregsdart] #3097346
11/26/22 05:51 PM
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Scary, but not especially relevant to door slammer drag cars.
LSR is a different story. The tube restrictions are huge overkill for a 90" wheelbase car, but will detect spans that need to be made into triangles on streamliners, etc.
Anything at all that shortens the unsupported span length, including gussets, fillets, and inserted support stubs, has a positive effect*.
Adding a short tube to anywhere along the length of a big tube divides it into 2 shorter lengths (duh). It need not be mid-way, even a 25-75 split is a big deal: a 75% length is 237% as stiff as the original.

* This includes pushrods, a longer tappet shortens the pushrod, many times the extra weight is a small penalty for greater valve train compliance.


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Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: gregsdart] #3097363
11/26/22 07:21 PM
11/26/22 07:21 PM
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Originally Posted by gregsdart
Poly, those are not reassuring facts, ๐Ÿ˜ณ
Al, i am going with figure B in the proper book, so i can have my helmet position partially under the main hoop. I am going to get the cage kit from RJ racecars, the rest of the tubing locally. Then find a good tig welder to help me finish.


So you are cutting it all out and starting over?


"I am not ashamed to confess I am ignorant of what I do not know."

"It's never wrong to do the right thing"
Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: Al_Alguire] #3097434
11/27/22 12:24 AM
11/27/22 12:24 AM
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Originally Posted by Al_Alguire
Originally Posted by gregsdart
Poly, those are not reassuring facts, ๐Ÿ˜ณ
Al, i am going with figure B in the proper book, so i can have my helmet position partially under the main hoop. I am going to get the cage kit from RJ racecars, the rest of the tubing locally. Then find a good tig welder to help me finish.


So you are cutting it all out and starting over?

Nope. I just need to drop the crossbar behind the driver, add the cage and other tubes not currently in the car that 7.50 requires. Roof gussets, bars under the driver (under floor), a bar under the bellhousing area.
When i built rhe chassis in 1997 i didn't realize how close i was to 7.50 specs. Only missing a few tubes and the cage.


8.77 153 mph best, 3055 lbs 528 indy 440-1 alky
Re: Cert upgrade to 7.50? Best chassis parts supplier? [Re: gregsdart] #3098072
11/29/22 11:59 AM
11/29/22 11:59 AM
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Update:
S&W has the mild steel 1 5/8 funnycar cage kit, and i found the balance of tubing i need locally. The kit allows the helmet to be partially under the main hoop by maybe 3 or so inchs, more than i need. I want to gain 2 inch leg room, plus that allows a little more room for entry/exit. Parts are on the way!


8.77 153 mph best, 3055 lbs 528 indy 440-1 alky






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