How to build an early hotrod frame

SmokeyStover---Damn---I just typed a 10 minute answer and the internet Gods ate it---I’ll try again. That same old “equal and opposite reaction” will try and spin the rear axle assembly in the opposite direction of the tires, under acceleration. If you are running a separate “torque bar” then you will be okay. On a classic 4 bar set-up, with the top link above the axle centerline, and the bottom tube below the axle centerline, the bottom link will be in compression, and the top one will be in tension. Those old ford rear radius rods were pretty thin walled, and were intended to take tension forces only. If you “hook-up” good during a “boulevard blast” and don’t have a separate torque limiting mechanism on the rearend, your bottom links might fold up on you.---Brian

 

Damn, I hate it when that happens.
If I know I'm going to get long winded I will usually compose it in Wordpad or Notepad (or what ever ASCII editor you like) and then cut and paste it.
I may have miscommunicated. I'm using a set of old front 'bones for the bottom links on the triangulated 4-bar. I didn't want to cut a nice long rear rod so I used what I had lying around. I think the ones I'm using are off a '35 and are pretty thick walled stuff.
I just checked and they are about 3/16 wall with an oval vertical cross section. I would think that the fronts would take quite a lot of compression loading as that would be the type of shock they would experience with a wheel hitting a pothole etc. I know it's not as strong as DOM but I don't have enough tire and weight to really hook up. The upper links are 5/8 ID DOM so I'm not worried about them.

 

Might? They do Brian, they do.

 

Brian,

First let me thank you for the wealth of information I have gotten from your thread!!!!!! THANK YOU

Secondly, let me apologize if you answered this question somewhere in here and I overlooked the answer.

My question is:

On the suicide front axle set up with the axle out in front of frame...you mention radiator mounting being "tucked in" behind the front bar. Is there a method of mounting that you know of....or have you seen a radiator mounted up in the center of the axle/wheelbase where it normally is positioned with the suicide set up?

I have a 30 coupe and it currently sits on a suicide front set up (assuming someone set the body on a Total Performance t-bucket frame just to sell it)....and yes... I was the one who bought it!...LOL
Anyways....I'm not liking the set back radiator look......is my only option to cut and extend the frame and weld in a stock style crossmember?

Thanks in advance for any help with this.....

 

When it comes to engineering, Brian kicks ass like some kind of Canadian cybernetic ass-kicking machine. He can probably even explain why, what we call "ham", they call "bacon". Plus, he probably knew John Candy.

 

You can hang a radiator any place you want to. It simply means building a flat plate for the bottom of the radiator to set on, and tying that flat plate back into the frame to make it strong enough to support the weight of the rad. A 3/16" plate would be strong enough. Look at the original Ford crossmember---it had only 2 holes in it to support the bottom of the rad. The rad is "steadied" at the top by the two round rods that run back to the cowl. The point that I was trying to make earlier, was that if you set the rad directly over top of the crossmember, with a channeled car, the top of the rad will set up too high. I am enclosing a picture of a 1/8" steel "radiator enclosure" that I fabricated and used on the roadster pickup. It (the enclosure) sat on top of my crossmember (my rpu is not channeled). The radiator bolted to the enclosure, also the "steady rods" that ran back to the cowl, also the 32 grillshell fit over top of it and bolted in place. two bolts went thru the bottom of the enclosure, and also thru the crossmember to hold everything in place. That same enclosure would fit down behind the crossmember or out in front of the crossmember equally well, and the bottom of the enclosure would fit at whatever height you were comfortable with. Although it doesn't show up very well in the picture, there are a pair of 3/8" diameter studs welded to the underside of the bottom plate--they pass down thru the Ford crossmember and have nuts on them.---I didn't use bolts because then the heads would have stuck up above the top of the bottom plate and hit the bottom of my radiator. (my radiator has a peice of 16 ga. plate welded on both edges between the upper and lower tanks, and its that plate that bolts thru the sides of my "enclosure" to hold the rad in place.)---Brian

 

if you are using old FRONT bones as your bottom link, you will be fine---they are much heavier than rear bones, because as you pointed out, they were originally intended to tun in 'compression".

 

I just ran across this picture on the HAMB and "borrowed" it, because it is such a perfect example of a radiator and grillshell tucked in behind the front crossmember on a car with a suicide style front crossmember. This style demands that you either stretch your frame about 8", or else live with a humungous firewall recess, to fit your engine in between the firewall and the radiator.

 

I found this thread just in time! I have read this all the way thru and enjoyed every page. I realized that in all of my CAD modeling I haven't paid enough attention to how much the suspension will deflect when loaded. I liked that guys fabricated jig used to measure spring rate. I may try to contact my spring mfgr. for some specs. I wonder how hard that will be?

Either way I'm heading back to the drawing board! Thanks for the thread.

 

Any competent spring manufacturer will be able to tell you how much their spring will deflect for every 10 pounds of weight applied to it. The trick really, is knowing what that weight will be. ---Not really an easy figure to come up with.---Brian

 

Great info Brian.I just came across this post looking for ideas for the Hambandy build.Alot of good info to be learn here.Just wanted to say thanks for sharing.I`m like a sponge for this type of info.

fitzee

 

FITZEE---Always glad to help a Newf.---One of my favourite places in Canada---Brian

 

Brian,
I've had many questions for you in the past and after two years I'm finally putting my 26 T coupe together. It's got a Buick V6 (just setting in the frame for weight), 373 geared S-10 rearend with drum brakes, modified prostreet frame, Super Bell 4" I beam Dropped axle with a four Bar and GM Metric front disk brakes.
I found an artical from you about Vega steering that stated that the steering box is to be mounted so that the input shaft is tipped UP at an angle of 10 degrees from the frame at the rear side of the steering box.
Questions: The frame sets at an downward angle, so do I add the angle of the frame to the 10 degrees?
How far forward should the box be located?
How far down in the frame should it be located?
Along with that question should the Drag Link be parallel with the Tie Rod?
What about steering stop nuts are they still used?
If there are any pointers you can give me I'll take them. Thanks for all your help!!!

<O></O>
Tom---Nice to hear from you.<O></O>
The ten degrees ‘tipped up” angle is from the frame itself---don’t worry about what “rake” the finished car will set on.<O></O>
<O></O>
A Vega box in a model A frame is located so that the 2 bottom bolts which will come thru the mounting plate just clear the underside of the frame rail by enough to get the nuts on them. The top bolt doesn’t get a nut---it will be almost in line with the top of the frame, so you will have to drill and tap the spacer which fits on the engine side of the nounting plate, between the mounting plate and the steering box---there is no room for a nut on the top.<O></O>
<O></O>
The “fore and aft” positioning of the steering box is detemined by the length of Pitman arm that you are using.---I always use an aftermarket Pitman arm which has the taper reversed at the outer end so that the drag link assembles to the underside of the Pitman arm to give me adequate clearance between the drag link and the underside of the pan).----When viewed from above, with both front wheels facing straight ahead, the drag link should be parallel to the tie rod---this will determine how far back your steering box is mounted in the frame from the front crossmember.<O></O>
<O></O>
I don’t use stop nuts on the cars I build---generally the Vega box will run out of movement before the wheels turn far enough to hit anything anyways.<O></O>
<O></O>
Good luck---Brian

 

Brian
lots of great info on frames/suspension
I'll be using this stuff as I get ready to start boxing my A-frame.
Thanks Ken

 

this thread was awesome! Brian you share with us so much!

 

Dude if you got elliptical springs keep it that way!! Or sell em to me...I hate the fact i couldn't use em since they are hard to find!

 

Brian, I found this after reading another thread that said search brainangus..I was amazed at your dedication to answering everyones question to the best of your ability. You are crazy genious. Anyquestion I had or planned on asking, and I only joined this forum a few days ago, you've answered all. Many thanks, and I am going to pass this thread onto my car club, saskatoon shifters, cause this is info that everyone needs to have. Cheers from a fellow Canadain. Thanks again.

 

Great Thread!! Full of useful information.

 

How long should my radius rods be??? My knowledge of radius rods is that yes, longer is better. Main reason for that is that the longer a radius arm is, the less movement back and forth on the axle being guided as it swings up and down thru the arc of travel. I find that the ideal point of attachment for rear radius rods is to the crossmember that supports your transmission tailstock, or up to about 10" behind it---and the closer together you can keep the ends attached to that crossmember, then the better your suspension will work. On the front, there is one caveat to remember---If you are using a cross steer (Vega) style steering set-up, then yes, longer is better. If, on the other hand you are using a steering drag link that runs from the steering arm up to the drivers side spindle, it is wise to keep the rear attachment point of the front wishbone in line with the point where the Pitman arm attaches to the drag link, when wheels are pointing straight ahead, when viewed from the side. That way, as the front axle moves up and down thru its suspension travel, the arc described by the influence of the wishbones will be equal to the arc described by the drag link as it pivots on the end of the Pitman arm, thus minimizing bump steer.---Brian

 

What material should I use to build my frame from?? Should I try and use an original frame or make a new frame?
I have done it both ways, and there is really no benefit of one over the other, except this. Firstly, if you already have an original model a frame, and it is in reasonably good condition. then there is no guesswork involved in where the front crossmember goes.--you end up burning out all the other crossmembers anyways as you change it over for modern engine and rearend--but , you are working with 70 year old steel which may be cracked and tweaked, so it must be closely inspected. If its okay, then add 1/8" boxing plates full length from the rear side of the front crossmember all the way back, and away you go.
If you are a reasonably good welder and know the dimensions you want to build to, then one weekend will build a beautifull frame out of nice new 4" x 2" x 1/8" wall box tubing. You will have to do a little creative metalwork to shape the front of the tubing into appropriate frame horns, and either buy or build a front crossmember, but its no big deal. However, if you are going for that ultra low look which is so popular here on the HAMB, with a big Z in each end, then I strongly recomend that you build the frame totally from new rectangular tubing and forget the original frame. Just remember there is a big penalty to pay when you Z your frame like that. It looks cooler than Hell, but now you will have to share an already narrow cockpit area with a driveshaft tunnel, because now the driveshaft will be above the floorboards.----Big assed hotrodders BEWARE!!---Brian

 

Hi Brian,
I am wondering if you would be able to answer this question. I noticed in the Speedway catalog that you can get a 2" lower front crossmember and a reverse eye front spring that is 2" lower. Wouldn't that bring the spring to close to the frame allowing it to smack the frame? I have seen people cut the frame above the spring to allow room for the spring to move , anyopinion on all this?
Sure did enjoy reading your frame building thread!
Back up to the top again it goes.

 

Hmmmmm!!! I'm not sure about this. I know that an old hotrodders trick was to put a model A crossmember into a 32 frame, and that would lower the 32 suspension about 1". I also know that from the top of a model A frame down to the center of the crossmember is about 3 or 4", so yes, they conceivably could make a 2" lowered crossmember, to drop the front of the car about 2". I also know that I built a perfectly flat crossmember from a peice of square tube with one side cut out one time, and yes, it did lower the front of the car 3 or 4", but as you supected, the spring did hit the frame, and then I had to put a 1" spacer in between the spring and crossmember to get the clearance I needed. Soooo---yes, you could probably run a 2" dropped crossmember and not have spring clearance issues where the spring passes under the frame.----The fact that a spring has reversed eyes wouldn't really come into play at the point where the spring passed under the frame---it would simply mean that the axle sets closer to the frame. Any adds I ever seen for reversed eye springs only claimed to drop the front end by 1", but I haven't seen Speedways add---probably one of the Durant monoleaf springs would get it down even farther, but I have never used one. Thats the most honest answer I can give you.---Brian

 

Best thread i've read on the Hamb

Thank You Sir!

 

Here's a new one on me---I haven't seen that done before, and I've seen a lot!!! This is the trap that a lot of people fall into when they add a dropped axle into a stock front end set up. The damn tie rod wants to run right thru the side of the wishbone. That is why so many people go to a set of batwings and a set of hairpin radius rods, to give tie rod clearance between the upper and lower hairpin. Or else they bend the steering arms to drop the tie rod below the stock wishbones. I have never seen it done this way before, but as long as there is clearance when tuned lock to lock, and the window in the radius rod is sleeved as shown, it should work okay.---Brian

 

Test post---Just bought a new computer.---Brian

 

Today I recieved an email from a fellow in Costa Mesa, Cali, asking about rear transverse spring hangers. Seemed that they had put a "new" rearend under their model A they are building, and when they got the body and engine mounted, the spring shackle was hitting on the rear axle as it tried to swing thru its arc of movement. They wanted my advise on what to do, so I sent them the following email---
Don't ya just hate it when something like that shows up at the end of the game!!! Without a picture of the offending area, its hard to give an exact diagnosis, but if I understand you correctly, when the spring flattens under load, the shackle is swinging beyond the 45 degree mark, and hitting the tube axle. this would mean that there is something wrong with the hanger welded to the rear axle. When the full weight of the body and engine are on the rear spring, the shackles should be at about 45 degrees---but tilted in towards the center at the bottom---not the top. That way, when the car hits a bump and the spring flattens out even more, the shackle will swing towards the outside of the chassis at the bottom, swinging thru an arc ---pivotting about the center of the eye in the shackle support bracket.The rear shackle bracket which is welded to the axle should be designed so that the shackle can actually swing about 15 degrees beyond true vertical before its swing is limited by the body of the shackle support bracket.---check whether you have the correct bracket welded to your rear axle.-----
Then, after reading it, I wasn't too sure that it would be clear, so I done up a couple of 3D solid models to illustrate the point I was trying to make. In both of the models, the spring and the shackle are setting the way that they should, when under full load. The transparent shackle shows the position that the shackle will move into when the car hits a bump and the spring flattens out momentarily, thus getting longer. This condition will last for only a second, then the spring will return to its normal shape and length. If the shackle is restrained by hitting the axle housing, or the shackle hanger, then you are going to either have a jarring thump, or you are going to break parts---or both. Interestingly enough, where I grew up, it was common practice to cut a bracket similar to the red coloured one from 1/2" plate and weld it to the top of an Econoline van I-beam axle to make a hotrod front axle. I was always to chicken to try that myself, but the president of my car club, Carm Nobes made a lot of hotrod front ends using that method, and I never heard of one failing.---Brian

 

My take on this is that if you build the shackle hanger to be Parallel to the axle when you install the spring you won`t have this problem?? Sound right?? This is how I did it on my 31 project. In the pic The Shackle on the right has sence been fixed to match the left.

http://img.photobucket.com/albums/v144/fitzee/rat rod/000_0808.jpg

 

I think what you are saying is parallel but also OFFSET.---Yes, this gets around the issue of having the shackle hit the axle tube, however it throws eccentric loading onto the axle that is not there with the spring directly above the axle. Now, with the setup you have, the axle housing will try to rotate whenever you hit a bump. On the early fords that had the axle behind or in front of the spring, this eccentric loading was taken up by the radius rod, because the spring shackle mount was actually a part of the radius rod. With what you have, that eccentric loading force will pass thru the axle tube itself and then have to travel down the plate brackets which you have hanging off the bottom of your axle tubes, then thru the radius rods. I think that the mounts you have cantilevered off the side of your axle tubes to mount the spring on will either break the welds or tear a peice out of the axle tube before it sees many miles of usage.

 

Very interesting.makes alot of sence. I seen it done like this before tho.There is a after market kit that is much along the same idea as I have. It is much beafer then the ones I`m using. I was planning on beafing up the bracket anyway. Thanks for the info.

 

Brian, thanks for sharing your methods and experience. Very generous of you. I did a fairly quick read through, of the thread, but I was curious if you had input on setting up width or distance between frame rails.