How to build an early hotrod frame

Gary--You are overthinking this. In a lightweight street rod, as in coupe or roadster with a small block in it, You are not going to see a big enough difference to worry about it. True, if you are a big company, GM or Ford, you have a fleet of engineers to work out all of the theoretically "perfect" suspension angles, tire offset, Ackerman angles, etcetera, and the tires won't show any strange wear patterns after 50,000 miles.--However, you are building a street rod. You want it to be safe, you don't want it to shimmy, or wheel tramp, or fight to go in a straight line. Lean the top of your axle back towards the rear of the car about 6 degrees when full weight of the car is on the suspension---that's plus or minus a degree and a half when you set up your front crossmember---that sets your caster angle. The camber angle will be "built in" to whatever axle you use, and the axle aftermarket guys generally always get that right. set your toe in for about 1/8". That's all you really need to be concerned about. Forget multiple mounting points, contact point, etcetera, unless you are going to Bonneville.

 

Brian, perhaps I do overthink things, but just to be sure I asked my question properly I found this drawing on the net. From what I've heard, the ideal king pin angle is one where the line drawn downward thru the king pin intersects the tire patch in the center of the tire's tread. In the case of this image, it doesn't hit center, but falls to the inside. So... I've been thinking that when you change tire diameters / offsets, you can't help but move that point left / right or perhaps even above below ground. That's my worry, that when this idea relationship is changed, you may drastically (again overacting) change the handling from over to under steer, for example. Gary

 

Best advice I can give is "try it and see"!!! In 1978 I built a 56 Ford pickup with a 390 Thunderbird engine in it. I wanted the "Hotwheels" look so I put 13" Micky Thompsons on it all the way round.--It looked AWESOME!! And it steered fine, going down the road. It had a stock beam axle with stock spring, and those tires were twice as wide as the original tires for that truck.--The only issue I had was that there was no power steering on it, and that T-bird engine and C6 tranny weighed almost twice as much as the old stock Y-block.--At low speed in traffic, or trying to park, it was a pure Son of a Bitch to turn the steering wheel. By the end of the summer, I had arms like Hulk Hogan---My wife wouldn't even drive it.---But---It steered and went down the road like a brand new truck. I even drove it down to the east coast on vacation with a camper on it. You can totally mess up your head worrying about all the different things that MIGHT happen, but the essence of hotrodding is "Try it and see".

 

Ok then. Now I've got to start calculating all some tire / rim sizes and offset combos. Thanx, Gary

 

I just found this tech and over the last few houres of reading and studing it all, you have helped me figure out all of my suspention concerns. Thanks for sharing your knowledge.

 

im just using this post so i can find this thread again, cheers.

 

Brian, I've read several threads on setting up a transverse rear spring and saw several versions that all make sense...but can you walk me through setting up posies '40 front spring to a '55 rear in a 1931 Model A (vaphead frame bought several years ago.) By the way, I've read this thread countless times and it's one of my favorites.
Ben

 

Sorry Ben--I can't do that, because I haven't done it myself, and I will only give advice on stuff I have personal experience with.--Brian

 

Man I'm glad I found this. Brian Thanks

 

Brian,
First let me say thank you for this thread and all of your help through the years. Secondly when you mention 6 degrees of neg. caster built into the front crossmember. Is that already there on an original 30 model A crossmember?
-Pat

 

Gary,
What you're describing is scrub radius. That's the distance between the king pin (steering) axis and the center of the tire contact patch.

In case you're still pondering this, a simple rule of thumb is to simply keep that theoretical point inside the tire contact patch and the car should be drivable with no major issues. While zero scrub (contact patch centered on pivot) seems like the ideal, it often isn't.

For example, you may want to minimize the difference that tire pressure or braking will cause the car to pull in one direction or the other. Or maybe you want loaded suspension bushings to give predictable handling results like stiffer bushings while still being compliant. Moving them apart allows the tire to load the suspension leading to more predictable handling events on soft bushings. A positive scrub with the tire outboard as in your picture will steer easier because the tire will roll around the king pin axis as the wheel is turned (if the brakes aren't applied).

There are lots of reasons (compromises) that a suspension engineer will select a tire/wheel combo that is offset from that point. But in general, just keep it inside the contact patch and you should be ok.

 

Yes, I'm still pondering and thanx very much for the info. Gary

 

Brian, I’ve read most of this thread from start to finish and THANKS for taking the time to start & maintain it. The information here is very helpful.

I have a couple of questions that I’d appreciate your input on if you’re still inclined to devote time to this.

I’m just starting to think about a Deuce roadster that would outwardly look somewhat traditional but that would have the soul and spirit of a track car. Power will be from a 289 Ford, that I’ve already started on; ‘block went to the machine shop today. When done it will be a moderate street engine, cam, headers, 4 barrel, balanced; stock heads cleaned up with new valves, hardened seats and light polishing internally. Nothing radical but enough pep to be fun in a light roadster. This engine will be in front of a 5 speed, probably Tremec. It will, I hope, be a Hot Rod that handles…really handles.

This is where the chassis questions come in and I’d like some advice. I’m planning a fairly traditional set up with a dropped axle up front, beyond that the page is clean. I’m thinking sway bars front & rear, ladder bars and coil overs. Is this the ticket for best handling, or would something else work better? I know from experience with my current car (Deuce 5 window with triangulated four bar & coil overs) that space for a sway bar is a challenge with that configuration.

I want the rear somewhat lower than the traditional hot rod rake. Given the shock travel issues these cars have, even with a C notch, what’s the best way to get the rear down? I thought about raising the shock crossmember or a small Z in the rear of the frame. The Z will cost trunk space and necessitate re doing the flooring and the raised shock crossmember will need a bigger C notch to get the clearance I’m looking for. I’d like to have an honest 4” of clearance for shock travel. Am I missing anything and do you have any thoughts as to how to best achieve the outcome I'm after?

Finally, am I being realistic here? I’d like to do a car that can be driven about anywhere with the ride & handling capabilities being a cut above the average hot rod roadster. Thanks for your thoughts.

 

Seadog, the one question you've asked that I'm able to answer is regarding the dropped axle. Have it bent (in a capable press) to give you a few degrees of negative camber. That'll help you tons with handling.

Look back three or four years through R&C. There was an article on a '32 roadster built to run road courses and it detailed the suspension setup. Almost all traditional or acceptable parts, nothing exotic. Wheels and tires were big n' fat and not my style, but the car performed real well.

 

Great reading tonight...

 

I want to thank you brianangus for all the efforts you put into this thread. Here is one I am working on now that uses the spring in front on a model A in the rear. It has an 8" Ford rear out of a Mustang with a stock A rear cross member moved ahead 8" and a T rear spring. I used a set of 37 front bones with a 1/4" flat bar welded in the middle of the tubes vertically. To attach it to the axle I made a set up like a 35-36 rear axle has. To attach the rear spring to the axle I used a kit for mounting the spring behind but swapped it to the front of the axle.

The shocks have a double sheer bracket welded to the bones on the bottom and some mounts bolted to the top of the cross member. The shocks were a tight fit and the flange of the A cross member had to be heated and bent down for clearance. I used a model A front bone capture mounted to a small cross member directly below the front u-joint to hold the 37 ball socket. This gave the suspension the design that alleviated any binding that splitting the bones does. Here are some pictures of the set up. The frame is from Dagel's and has their x-member in it.

 

Just read this post "AWSOME" job Brian thanks for posting

 

I am glad this is still here ten years later...

 

10 years?????.... Im looking at 11 years lol... THANK YOU BRIAN, I am starting the planning of a new project, a '28 Chevy, your thread will be my goto for a long time.

Sent from my cell phone when I shoulda been working, using the H.A.M.B. mobile app

 

Luckily Photobandit didn't screw up this oldie but goodie.

 

Yeah I was thinking the same thing

Sent from my cell phone when I shoulda been working, using the H.A.M.B. mobile app

 

Nice work 55Willys, this design has inspired some thoughts for my next project, helps keep it low and no bottoming out of rear suspension.

 

Seadog, I am no expert, but I always give the highest priority to keeping my center of gravity as low as possible, I see this as key to providing good handling in our style of vehicles. Besides acceleration which is the easiest to achieve, performance also means steering and stopping besides suspension considerations which always seem some what limited with our old style suspension, but then again there are sway bars, top quality shocks and decent drivers seating that all help claw back some of the losses.
What ever changes you make to improve it, there is always the possibility that it will affect other areas of your build as you mentioned with the rear floor, no big loss in my book...
Good luck and keep us posted.

 

Subscribed

 

brianangus rules .......... ruled.

Car 54, you out there ???

 

According to his profile page "brianangus was last seen: May 2, 2014".

I sure hope he's ok and would like to see more of his posts. They were always worth reading.

 

Hi guys..
There is a thread with an answer just for this question
https://www.jalopyjournal.com/forum/threads/anyone-know-where-brian-angus-is-these-days.1050531/
Hopefully I pasted that properly. Otherwise just for a search for:
"ANYONE KNOW WHERE BRIAN ANGUS IS THESE DAYS?"
So much of this "old" fantastic knowledge that was shared needs to be protected somehow....

 

bumping a classic thread created by brianangus created a long time ago. Thank God for the old timers who share the gospel of building hot rods.

 

He's still doing bad ass sh*t.

https://www.homemodelenginemachinist.com/threads/a-blast-from-the-past.31354/

 

Hi Guys.--I'm still alive and well. I'm getting a bit too old at 73 for a lot of involvement with hotrods,but it was a hobby that I loved and lived for over half a century. I always grin when a message shows up on my computer from the HAMB. I'm glad that I was able to contribute some knowledge of hot rodding to all of you. My arthritis got so bad that I couldn't get down on the garage floor to work on hot-rods any more, so I sold the Wild Canary (my yellow Ford roadster pickup) about three years ago. I stay busy in my machine-shop, designing and building miniature engines. It's nice to hear from you.---Brian Rupnow