Thread: I need help building a frame to go with my Jaguar front suspension

Tweet

I have the front & rear independent suspension out of a '75 XJ6. I'm building a hot rod from the ground up, and I can't find much info about building the front of the frame to work with the IFS.

Any ideas?
Thanks!
Chris

you could do a search on here concerning frames a lot of the guys on here build there own. hang in there some one will be along.. OH and Welcome to CHR

What kind of frame? Rectangular or round tube? What kind of car?

Generally speaking, you'll have to put the front and rear suspension in place on some sort of fixture at ride height, paying particular attention to having all the geometry correct. Is the suspension still all together or apart? Do you have a chassis table or some other type of fixture to build the frame on????

The frame rails will be 2 x 4 rectangle tubing. I don't know what kind of car it is... I'm building it all... haha. It'll be similar to a T-bucket only longer. I don't have a frame jig, but I have a 4' x 16' table I can lay it out on. I have a cnc router that I can use to route wooden jigs to get stuff in the right position. I guess I could go to a jag junk yard and take some measurements.

Maybe I should mock up the whole frame in wood first.

Welcome to CHR, Chris. I think you first need to sit down and decide exactly what you want to build. For me, that means drawing it out to scale (computer drafted, drawn out on paper, however you can), including wheel & tire size, wheel base, ride height, stance, and body position. Once you have the car drawn the way you want it you can draw out the chassis to fit, and figure out the details of necessary "Z" sections to get the height right, etc. For others it's mocking up everything with jackstands, blocks, etc, to "eyeball" the right look. Whichever works for you the key is to plan the work, then work the plan to build it. Just my $0.02.

Hi Chris-we have a user who's name is Astroracer that I think he said he has the programs for CAD design frames.Based on what he has done on his ground up build of his frame,I suggest you PM Mark and see if he couldn't help you out.

Chris,

I'd have a real good idea of body size before I'd tackle the frame. Like the fellas said, have an idea overall drawn out of what you want. Once you get far enough to start the frame, I'd get on a forum designated to Jags and ask them if they have specs on the model you have for reference. When I installed the Corvette IRS I hit the Corvette forums and found a couple fellas that sent me the specs in PDF format. Like Dave said, figure your ride height and match the factory specs, to a point, for caster and camber. Just as important for the rear. I had to narrow mine and it was pretty difficult for me to maintain those settings. I'm still going to lose a bit under full suspension travel but at ride height it's perfect.

What helped me the most on the IRS, I had the factory bracket that the front of the dog bones (links) mount to. I found a 85 Corvette and asked him politely if I could take some angle readings of the bracket with the bracket mounted to the car. For me that angle was what I set the whole rearend up around. I used a digital inclometer. It can be zero'd off the bottom of the hub.

David

Trade you places. You can come here and work and I'll go hit the slopes?

Welcome to the site!

David

You could get the Circle Track Analyzer to check the geometry of the front.
I used it to set up my upper and lower control arm lengths and pivot points.

A CAD program will do nothing that a sketch pad, scale, and a straight edge will do.... Like others said, the first thing you have to do is some planning, what engine and trans will you run, what are there dimensions? Need to determine a wheelbase so that you can design in an instant center that is acceptable.

I would say start with the drawing and parts planning first. There are so many variables that go into chassis design you are going to have to have a lot of your major components picked out and their dimensions before you can start on the frame rails....as well as a sturdy, flat, level, and squared surface to do the actual building on.....

Originally Posted by 123pugsy

You could get the Circle Track Analyzer to check the geometry of the front.
I used it to set up my upper and lower control arm lengths and pivot points.

Nice Pugsy.

For some reason I think Mark(Astroracer) is a designer/engineer.That is what
he does and that is why he has the programs he has.Agreed pen and paper will get you their too.Sure don't hurt to have a guy like Mark(if he has the time)helping out.

If you have the suspension componants from a jag then get the frame plans for that car. From those plans you will be able to get the proper suspension mounting locations in three dimensional space. When you know where the bolts holes should be then you can design a frame that can accomodate where the suspension bolts to. What you will find in working with dedicated componants is that they won't be very forgiving nor adjustable - they are designed to work proper in just one particular relationship to each other and if you - for instance - want to change the ride height it won't be a simple matter of raising a bolt hole or two.
Chassis design is a simple or complicated as you want to make it. I do them from chalk on the floor to AutoCad Inventor 3D plans and the absolute best is get a roll of butcher's paper and draw everything at 1:1. Figuring out where everything goes is easier than you think, just apply common sense. What size rear tire, draw it on the paper and the middle is the center of the rear end, about an inch below that will be the pinion (figure which rear you want to use and get the right pinion offset); what size front tire? draw that and the middle is your front spindle height; How big clutchcan/torque converter and add some clearance - say 12" + 6 or 1/2 of 12+6= 12" to the crank - so that is your driveline height from the harmonic balancer to the tranny tailshaft and now you know where the engine and tranny is all you need to add is the length. This will set the driveline level and the driveshaft will run uphill into the pinion which should also be level and that will automatically give you a good pinion angle. Just keep going, plug in the knowns and the unknowns will solve themselves. Drawing at 1:1 you can lay the part on the paper and trace it or cut the frame member and lay it right where it belongs.

Thanks for the info. Turns out the doner car is still in one piece and I can go measure where everything went. That should make it much easier for me.

Thanks!
Chris

get the car and build a jig to the attach points or cut out the frame front section and use it as part of a jig

But at least get the car for referance--a used car is cheap--when I built my fire bird prostocker, I leased a IROC Camaro to take measurements from. and rented a firebird formula from avis to pull molds for front end fiberglass