Rear Frame Rail Notching How To!

There are a lot better shocks out there for drag racing than the qa1. I am changing to a new shock in the rear and wish i would of done it right the first time.
 
Very nicely done article. It seems to be an overview of the typical way it's done. From what I understand from past postings, you will get the body panel wrinkles with the notching done this way, am I correct?
 
Chassis Jig

I've been studying up a bit and I am to a point where I'm looking to build a chassis jig. It will be a type that can be broke down and stored in a corner of the shop when it's not needed. I've seen some interesting designs on the internet and wonder if anyone out there has a favorite design they would like to share.

The plan at this point is to build a new rear frame section that will retain the OEM four link design. It will feature adjustable forward mounting points for the UCAs. The shocks will be mounted very close to how the stock shocks are mounted. The springs will use the same mounting location as OEM and will be the smaller coil over style springs for frame rail clearance purposes. The frame rails will be 2x3" channel tubing, at least 1/8" thick. I haven't decided whether to have the channel wrinkle free mandrel bent, or just angle cut and piece it together. The fender wells will get a work over too. The idea is to get all the clearance I can with the LCAs and springs being the limiters. Not the stock fender well. The floor pan behind the support structure after the passenger foot tubs will be removed. I already have sheet metal covering that area. How far back I will be removing the floor pan is still to be determined.
 
Donnie,

This sounds very interesting, would love to see updates with pictures! (as I assume you will do as always :) )

You might check out a company called Autoweld Chassis (autoweldchassis.com/index2.ivnu). They will bend up any 2x3 to your specs (not generic frame rails like most offer).

Keep us updated!

Thx
 
WHITE T said:
Donnie,

This sounds very interesting, would love to see updates with pictures! (as I assume you will do as always :) )

You might check out a company called Autoweld Chassis (autoweldchassis.com/index2.ivnu). They will bend up any 2x3 to your specs (not generic frame rails like most offer).

Keep us updated!

Thx
Click to expand...
I do plan to document and share the modification in great detail.
I came across that site in my studies. I'll most likely use them, if I go the mandrel bending route.
 
I picked up 8 pieces of 3"x3"x3/16"x30" rectangular tubing to build into stands. Each will have a base footing plate of 12"x12"x3/16" and a 6"x7"x3/16" pad at the top. Provisions for leveling will be built into the stands. I think 30" will be enough to get around the car for fitting and welding.
Material cost: $187.00.

I'm going to try to keep track of the cost of this part of the project.
 
Just a note about the QA1 shocks. The double adjustable is an OK shock for drag racing. Its taken a few years for them to come around. The valving is still somewhat odd but Todd @ TRZ thinks they are good shocks.

The Stange shock is prefered due to the quailty and performance. They can also be had cheaper if you shop around.
 
The job although completed very nicely is not deep enough for the trouble.The above magazine article clearly depicts what I mentioned in my earlier post.

The rear portion of that magazine notch will cause issues with tires in the 29in. tall range.The rear of the notch had so be done deeper than the front due to the way the frame spreads outwards towards the tire. I have found that you should notch to about 3/4 in from the rear frame bushing or closer..

I like the fact they used nice heavy material to re box the area. I have always frowned on reusing the stock piece back in the notch. I also angle the front most and rear most sections of my notches instead on just doung a 90 deg. notch. The angle box is much stronger and if done correctly saves you two extra welds.
 
Quoted from Louie L.
The job although completed very nicely is not deep enough for the trouble.The above magazine article clearly depicts what I mentioned in my earlier post.

The rear portion of that magazine notch will cause issues with tires in the 29in. tall range.The rear of the notch had so be done deeper than the front due to the way the frame spreads outwards towards the tire. I have found that you should notch to about 3/4 in from the rear frame bushing or closer..

I like the fact they used nice heavy material to re box the area. I have always frowned on reusing the stock piece back in the notch. I also angle the front most and rear most sections of my notches instead on just doung a 90 deg. notch. The angle box is much stronger and if done correctly saves you two extra welds.

Very good points.
 
Louie L. said:
Just a note about the QA1 shocks. The double adjustable is an OK shock for drag racing. Its taken a few years for them to come around. The valving is still somewhat odd but Todd @ TRZ thinks they are good shocks.

The Stange shock is prefered due to the quailty and performance. They can also be had cheaper if you shop around.
Click to expand...
What do you think of the Afco shocks. I've talked with some local racers that really don't have anything bad to say about them. On the contrary.
 
$82.00 for setup tooling.
Square
Plumb bob and string
Digital level and batteries
Contour gauge.

Didn't really need the contour gauge. I just thought it would be a neat tool to have. Don't take me shopping.:biggrin:
 
DonWG said:
What do you think of the Afco shocks. I've talked with some local racers that really don't have anything bad to say about them. On the contrary.
Click to expand...

Love my Afco's. Compression is adjusted by turns on a knob and the extension by sweeps on the top of the shock. I found the rear shocks were more important than the front since I run so little travel. I have the dbl adjustable QA1's from TRZ for the front and like them......but they're no Afco.

On the notching. I'm a firm believer the bracing/roll cage tie in points are much more important than the frame itself. The last car I looked over had nothing but the rear part of the frame left....basically 1/8" thick or the factory thickness. This is to fit a 12 inch wheel and a 315/60 radial at a very low ride height. The roll cage was tied into the frame where the upper and lower arms attach to the frame as well as the where the spring pocket is. Special attention was paid to the section between the rails where the upper arms attach to the frame. There were several bars tying the main hoop to these mount points. From that point back, the frame only holds up the bumper. Rather than relying on the frame to support the bumper and parachute mounts. A "backbone" if you want to call it that, was ran from the main hoop, back to the bumper area to support the parachute mount.
 
Dusty Bradford said:
Love my Afco's. Compression is adjusted by turns on a knob and the extension by sweeps on the top of the shock. I found the rear shocks were more important than the front since I run so little travel. I have the dbl adjustable QA1's from TRZ for the front and like them......but they're no Afco.

On the notching. I'm a firm believer the bracing/roll cage tie in points are much more important than the frame itself. The last car I looked over had nothing but the rear part of the frame left....basically 1/8" thick or the factory thickness. This is to fit a 12 inch wheel and a 315/60 radial at a very low ride height. The roll cage was tied into the frame where the upper and lower arms attach to the frame as well as the where the spring pocket is. Special attention was paid to the section between the rails where the upper arms attach to the frame. There were several bars tying the main hoop to these mount points. From that point back, the frame only holds up the bumper. Rather than relying on the frame to support the bumper and parachute mounts. A "backbone" if you want to call it that, was ran from the main hoop, back to the bumper area to support the parachute mount.
Click to expand...


Dusty you didnt happen to take any pictures of the car did you?
 
ttypewe4jim said:
Dusty you didnt happen to take any pictures of the car did you?
Click to expand...
Dusty. That setup sounds very interesting. I agree with you about the bracing/connecting to the roll cage. I've been studying the RaceTech Race Chassis School modules. Almost through the 4th of 5 modules. Even though the study course is geared for a full blown tube chassis, it gives great insight into how the different chassis loads are distributed through the whole cage. I'm trying to envision a cross between a simple roll cage and a well tied in rear section. It sounds like the car you're describing has some good ideas. I'm not trying to do a full blown funny car cage, just something very effective up to the 8.50 et limit, but I do whole heartedly agree that the rear cross member(s) should be tied into the main hoop.
 
Although this is way more than necessary for a stock suspension car this pic shows what people are now doing to strengthen the rear of the car. You can accomplish the same thing with a few bars placed in the correct position tieing into the suspension mount points. This "backbone" structure can reinforce the frame rails so you don't need big beefy rails. This allows max tire clearance and a low ride height.
 

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  • rollcagebbone.jpg
    rollcagebbone.jpg
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That's the type of cage structure I'm studying up on now. I... I'm really trying to resist going the whole nine yards.
 
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