How to build an early hotrod frame

Hi Brian:

Well, about two hours ago I googled for help on building a frame and suspension...and look where I ended up! FANTASTIC!!

Yes, I read every word, and I'm going to have to do it again no doubt.

It's been 25 years since I built my last rod, and hopefully next year I'll be able to start on the next one.

I know you have been thanked many times before, but a thousand thankyou's from me.

 

Merry Christmas 2010 to all you rod builders. I am still driving the 31 Model a roadster pickup that I built when I started this thread, (although its gone to bed for the winter right now). It always gives me a moment of cheer when this thread shows up in my email, and I know I have helped another aspiring hot rodder.----Brian

 

Just want to say thanks for your time in putting this together for all of us. I have read it all and I have saved it for future reference. Can’t wait to get started on my first build thanks again

 

Great thread!

 

you wanna know how to build an early style frame. just dont over engineer shit....

 

The best HAMB thread ever Brian. Thank you !

Just one tip about bending frame rails.
A tight string right down the middle of the chassis makes a great center line to work from, and it won't shift while you work.

 

Its been a while since I posted anything in this thread, but tonight when I was answering someones question elsewhere, my answer seemed worthy enough to post. Its about what to use for isolation bushings when building engine mounts.
I buy mine from Horton in Milton, and I think he gets then from Pete and Jakes. They are urethane 4 link bushings. They work really well for motor mounts and 4 links, but I will give you a word of warning. You absolutely can not "dummy up" mounts to tack them together with those bushings in place, then remove the engine and bushings to finish up welding. Those damn urethane bushings melt if you even breathe on them. They stand up fine to general engine heat, but they sure don't like heat from even short tack welds. After ruining enough of them and then having to re-order and wait, I finally turned up a bunch of them on the lathe from cold rolled steel. Now if I am positioning a suspension or a set of motor mounts, I use the steel units I made, tack everything in place, then disassemble and do the finish welding. The urethane bushings seem to last forever then.

 

Not a bad idea, but did you ever try to hook a tape measure on a string and measure from it?--String moves all over the place when you pull sideways on it. I build my frames on the garage floor, and to establish the centerline I drill two small holes into the cement about 10 foot apart and tap in a small lead or plastic anchor that will accept a #8 screwnail. Loop one end of a chalkline over one screw, pull it tight and give it a wrap around the second screw, and give it a snap. Then roll up the chalkline and remove the screws. The chalk outline will remain on the floor long enough to run a peice of masking tape along it. That won't move when you measure from it (Try and remember which side of the tape you are working from). If the tape gets messed up (it always does) you still have the anchors in place if you have to redo the chalk line.

 

Wrong technique.
You sit the end of a three foot steel ruler up against the frame, and read off the string.

 

Great thread!
Very informative

Spike

 

Hi Brian... I am also from Canada ...we wont tell anyone though...

I was looking on this site and some others... for dimensions for my 4 link brackets... as far as metal thickness goes. I have seen them from 1/8" which seems a little light to me... right up to 3/8" which seems a little overkill ... for my rod anyway..

I am running a ford 8.8 rear... t5 trans .. and a turbo charged 2.3 ford engine....stop laughing already...lol.... anyway you seem like one of the most knowledgeable people on this site... any info would be appreciated..

thanx Roy

 

Hi Roy---I'm from Canada, and damned proud of it!!! If your brackets are fairly short, with the actual pivot point close to the frame, you can get away with 3/16" plate. I generally always use 1/4" plate---The extra 1/16" of thickness won't cause any serious weight problems, and it takes away the pucker factor when you really get on it .----Brian

 

Thanx Brian.... I am proud of being Canadian too..... seems there are quite a few Canadians on this site.. I will take your advice and go with the 1/4 inch plate... awesome thread you have here,... and great work on your truck... thanx again for your help...


Roy (from Canada ..lol...)

 

I was looking to build some ladder bar brackets just like these. I have heard that about seven inches is a good distance to set the clevises apart. Do you have a picture of these brackets that includes the dimensions? Thanks again for the help that you have provided with this thread as I am in the middle of building my first hot rod frame and it has been an immense help.

 

I don't have drawings that I keep around of these things. They are not like panty hose---One size does not fit all!!! As a general rule of thumb, when viewed from the side, a vertical line drawn thru the upper and lower pivot holes should set about 1" forward of the outside of the rear axle tube. The big hole, of course, matches the outer diameter of the axle tube. The outer diameter of the small removeable back portion should be about 3/4" to 1" greater than the diameter of the axle tube---That will give you 3/8" to 1/2" of meat on the radius. The top hole should always be at least 2" higher than the center of the axle tube. The bottom hole should be 5 1/2" to 7" below the top hole. The plates should be a minimum of 3/16" thick if you are using 2 with the radius rod bushing trapped between them, or 3/8" thick if you are using a single plate with a clevis mount on the end of your radius rod or 4 bar link. Generally, if the top hole is more than 2" above the center of the axle tube, then you will have clearance issues with the floor of the car.---Brian.

 

Brian, I am in the early stages of building a 30 Chevy coupe and have the original parallel leaf spring setup with the original steering box. You recommend a conversion to a model A crossmember in order to expand my choices of suspension/brake parts. In my hunt for a model A crossmember, should I be looking for a particular year? Are the 28 - 31 units pretty much the same? It seems as if I will need to rethink about how to mount my radiator surround. cheers

 

To the best of my knowledge, all years of model A crossmember were the same. You can buy aftermarket ones where the geometry has been changed slightly, so that the top of the spring sets closer to the top of your frame rails, thus lowering the front of your car an inch, but I don't recommend them. You can get the front end low enough, sometimes too low even, by using a reversed eye spring and a 4" dropped axle. Try to find an aftermarket crossmember that has the 6 degrees of negative caster built into the area where the spring rests. If you put in a crossmember which does not have this angle formed into it, then be sure and weld it in at that angle, with the top rear side of the crossmember tipped down 6 degrees towards the rear of the car. The angle your crossmember sets at is what basically determines what angle the spring and axle sets at, and 6 degrees is just about perfect for these old beam axle cars.----Brian

 

while the Ford front end looks right at home in a Ford
something about a Ford front end in a non Ford never quite looks right to me

I'd keep the parralel spring style suspension in a Chevy
but that's just me

 

Paul---I agree with you, but---I have found it extremely difficult over the years to find replacement or aftermarket parts for early Chev beam axles. They work well, but its the lack of parts to upgrade them that has always steered me towards using Ford front suspensions.---Brian

 

Brian,
Thank you for the info on the ladder bar brackets. I have one more question for you. this is my first build and I am trying to figure out the order in which to do things. I read earlier in this post where you were talking about pinion angle and from what I understand you want to get the front end assembled and put the rear end under the car with the spring that you are using and compress the spring by getting some fat chicks to sit on it then you can figure out what angle to put your ladder bar brackets on the axle so that they will line up with whatever front mounts you are using. If that is correct, then the question I have is how exactly to mount the spring hangars in order to get to this stage. I am using a posies model a style spring and their spring behind hangars that place the spring seven inches center to center from the rear axle. I am also using their rear shocks that will mount between the axle and the spring. Can I just put the rear into a fixture at 3 degrees up and weld the spring hangars in so they are level with the world. Also I have an 8" kick in the rear and 4" in the front would that have any effect on the pinion angle? Thanks again for any help. and here is a picture of my frame as it sits.

 

Again, you are dealing with the uncertainty of just how much your spring is going to compress between "free" state and after the full weight of the car is setting on it.-Simple answer is to find a friend with a similar size car and the same spring and measure the difference between his spring and yours.---Or you can build some kind of jig to hold the spring securely and preload it to what you THINK the car is going to weigh and see how much it compresses.---Or you just put the rear into a fixture at 3 degrees up and weld the spring hangars in so they are level with the world (Which is what I always do) The ladder bars should have at least one adjustable end on them, so you can tweak the pinion angle after the fact if you need to.. Choices are somewhat infinite here, although its a bit more difficult with a leaf spring than with coil overs. The fact that your frame is kicked up front and rear really has no effect on things.-----Brian

 

Thanks man I think they have a similar set up over here at full tilt street rods so I'll see if I can get some measurements from them.

 

No, 28 29 radiator mounting pad height is different (higher, I think) than 30 31 radiator mounting pad height.

 

Sorry have not read all 14 pages but unless I misunderstand what you are saying, I believe rubber rake must be accounted for since 2* of rubber rake would deduct 2* from frame/spring caster.
"relative to the top surface of the framerail." ... I believe caster should be measured relative to level ground.

 

hey brian, thanks for all the awesome info! Got a question though, started on my frame the other night, doing a suicide front suspension set up and I wanted to go to a 3in crossmember instead of 4. 4 just looks too bulky for me. Yay or nay? if you think its safe, any chance I could get some measurements for the spring perches with a 3in crossmember?

 

Yes, 3" diameter will work fine. I wouldn't go any less than a 3/16" wall. as far as a drawing, there are too many variables for a generic drawing. One variable is how much drop you want to engineer into it, the second being how far away do you want the spring to be from the center of the tube horizontally.---Brian

 

thanks brian, I'll sit down and geek out on a template for this.

 

Wow, Brian. Wow. I'm probably only the 4,000th person to say this, but this is a great thread. Post #189 which explained a strategy for setting up the chassis and engine stance was a great summary for a newbie who's trying to get his arms around all of the moving parts. The thread's age speaks to its utility. I think my brain got a little bigger reading it. Thanks, Cory.

 

Brian, just found this thread, its late, its been a loong day, read 4 pages, all I can say is THANKS for all the info and I cant wait to read the next 10 pages tommorow!!!

 

More chassis building poop---This came to me as an email from someone asking about death wobble and how to establish the centerline of their chassis. I have copied and pasted my answer to him----perhaps it can help somebody out.----Brian

Brian---I was hoping I could pick your brain a little.

My car: 1931 Tudor Sedan on a 32 duece frame.
Model A crossmember
SBC 350, turbo 400
Superbell dropped chrome spring over
front mounted by hairpins
Ford 9" with tri-angular 4-link/coil-overs
4-wheel power disk brakes
Fenderless car, open hood

Over the weekend I was on a 120 mile trip and had a scary experience. While traveling at highway speed (70 mph) a expansion joint at a bridge sent my car into a horrible shake. My brother was following in his sedan and said he could see 6" of air under the driver's side tire and then the passenger side repeatedly until a got slowed down to 30 MPH. I pulled over and checked everything out but could n't find the problem. We hit the road again at a slower pace and it still happened numerous more times. I babied it home and tore into the frontend. Here is what I found so far;
1. No play in the front wheel bearings but I did see some pitting and the outer bearing didn't feel perfect so I will replace.
2. All front suspension seems good (car only has a few thousand miles on all new parts)
3. Front shocks seem lousy. (Pete and Jakes) they seem to have a dead spot right about where normal suspension travel would be. I will be ordering new So-cals or Bilstien gas units.
4. The front hairpins are mounted to the side of the frame (like Pete and Jakew suggest on their 32' frame kits) drivers side in great shape. Passenger side - WOW. The bolt wore thru the sleve going thru the frame and started wearring into the inside of the passenger frame rail. The outside of the passenger frame rail sleve (where the hairpin mounts) was worn very thin towards the back of the car, the inside frame rail sleve was worn all the way thru and into the frame boxing plates about 1/2". I fixed the damaged area and welded in a new sleve.
I think I found the "death hop" problem but I am not sure if the damage caused the problem or if the problem caused the damage. The car has been on the road for a while and I never had this issue before.
We did re-adjust the rear 4-links recently because I started feeling a little wobble at 55mph and found the rear-end was not set properly. (Wheel base was off by 3/4", longer on passenger side).

Anything you might suggest I try will be great appreciated. I think I will re-set everything in the front just like it was a fresh build to make sure I have my bases covered. I just cannot figure out why I never had this issue before or what could be causing so much force on the passenger side hairpin to wear out the sleve. I am hoping the mounting bolt had loosened up and allowed the bolt to rock which led to the sleve wearing thru.[/QUOTE]

Wow!!! Glad you didn't get hurt!!! Best suggestion I can give is --check and see that your front and rear axle are setting at an exact 90 degrees to the chassis centerline---If you don't have one already, add a front Panhard rod. Reweld and re-align everything, Make sure you have1/8" front tire toe in, make sure top of front kingpins are leaned towards rear of car approximately 6 degrees +/-. Good Luck---Brian[/QUOTE]

Thanks for the speedy reply. I will re-establish everything before the car hits the road again. What is the best procedure you recommend for setting the rear and front axles at exactly 90* to the centerline of the chassis on a assembled car?[/QUOTE]

That, my man, is a miserable bit of work. I do it on a concrete garage floor, with car setting fully on suspension (no jacks) using tape measure, plumb bobs, and a chalk line. --Measure to find center of front crossmember, hang plumb bob, transfer mark to floor . Find center of rear crossmember, hang plumb bob, transfer mark to floor. Connect the front and rear marks on the floor using a chalk line to get the centerline of the chassis established. If your car is too low to get under, then you must support each tire with the same height of stand to get the car high enough to work under (Make sure it is blocked----It can kill you!!!) Measure out an equal distance from each side of the newly established centerline, and hang plumb bob off rear side of rear axle, transfer marks to floor. Connect the two new marks with a chalk line or a long straight-edge. The lines on the floor should cross at exactly 90 degrees. Repeat same-o on front axle, add third line to garage floor. It too should be at 90 degrees to center of chassis line. Measure between front and rear "points" on floor----Measurements should be within 1/4" of one and other, or it means your car is going down the road diagonally.---Brian