How to build an early hotrod frame

Yes, I know exactly what you are asking about. You will have to provide me with a bit more detail, but on an early rod frame, the frame inside width directly above the center of the front axle should be 1 1/2" wider than whatever grill shell you are using. At the firewall, it should be about 1 1/2" narower at the outside of the frame rails than the outside measurement of the front of the cowl, and out at the rear, it should be 1 1/2" narrower at the extreme back end, over the outside of the frame than the measurement inside the body at the corresponding point. The frame rails, when viewed from directly overhead have only one bend in them,and that is about 25" behind the firewall where they begin to flare out towards the rear of the car.

 

I went back and checked some numbers, and edited the previous post and drawing a bit. I have added the dimension from the centerline of the front axle back to the firewall and then changed the dimension from the firewall back to bend in the frame to reflect what I did on the roadster I built. Don't be alarmed when you see the drawing with the body on the frame, and it looks like the cowl at the firewall is much wider than what my frame building numbers would imply.---Remember that the cowl is wider up at the top than it is down at the level of the frame.---Brian

 

Good info.

subscribed to thread.

 

Brian, this tread has me thinking again about drive train issues...

The whole pinion angle thing and all. I have to ask this:
When using a t350 tranny and a maverick (offset 8" rear end) how does one accomodate for the offset?

Maybe I haven'te been looking at the car for a while and I'm freaking myself out for no good reason...

 

The secret with pinion angles, are that they should be parallel with the gearbox.
And as long as the engine is mounted along the frame centerline, and the rear axle is mounted 90 degrees in relation to the frame centerline. The offset does not matter.

Parallel is the name of the game.

 

Yes, Mr42 is correct. the offset when viewed from above doesn't really mean anything. It can be ignored, except you must remember that the driveshaft will not run parallel to the centerline of the car. This only takes on any importance when you are running a channeled body with a driveshaft tunnel.--You will have to either build the driveshaft tunnel so that it follows the angle of the driveshaft, or (which is more commonly done) make the tunnel straight but a bit wider to allow for the angle of the driveshaft from front to rear when viewed from above.

 

whew... I thought that's what I read but had one of those puzzling thoughts enter my head in the middle of the night.. thanks

 

great info in this little book, let keep this building with info guys

 

THE FOLLOWING RESPONSE WAS TO A GENTLEMAN FROM IRELAND, WHO WANTED TO KNOW THE PROCEDURE FOR "PINCHING" A MODEL A FRAME AT THE COWL: Hello James---Welcome to Canada---Your not intruding. I am going to assume that you still want the stock width front and rear crossmember, and that you plan on some custom body mounts.---The body mounts are an angle that set on the outside edge of the frame, so if you suck the frame in 1" per side, the outstanding leg of the angle, along with the holes in it will have to be extended by 1" to maintain the same position relative to the body. Since all of the other crossmembers will be removed except the rear crossmember and the front crossmember, you could conceivably use a boat builders clamp at the point where you want the narrowing to occur, and start tightening.---A boat clamp is a pair of castings fitted to a peice of 1" pipe. one casting is the moveable jaw, and can be slid to whatever length you need,then locked there, the other casting is attached to one end of the pipe and has a moveable jaw which is moved along parallel to the pipe with a crank mechanism and an acme thread. (I have a pair and can send you a picture if you want.) You do not say if the frame is boxed or not, (I hope not) and will structure my answer based on the assumption that it is not boxed. The big trick is to be sure that you bend each frame rail by exactly the same amount. I would set the frame up on 4 boxes about 16" high at each of the 4 corners and level it and check for squareness before I started bending anything. Use a plumb bob and a chalk line to establish a centerline on the garage floor that clearly marks the centerline of the frame on the floor. Use an oxy acetylene torch with a big cutting tip or a rosebud tip, and heat one frame rail at a time to a cherry red in a band about 2" wide exactly where you want the bend to be, before using the boat clamp. ---Be especially sure to get a lot of heat into the top and bottom flanges, as this is where the most resistance to bending will be. As soon as one frame rail is cherry red, put the boat clamp on, and start tightening untill the heated framerail moves in the required amount---It will bend very easy when heated to cherry red, and the unheated framerail will not bend. Be very carefull during this operation that you do not move the frame around on the boxes relative to the centerline, as this is your "witness mark". You will need a 24" level, and probably a carpenters square, to measure exactly how much bend is enough. Leave the boat builders clamp in place, and walk away---let everything cool for an hour. go have a beer. Then come back and remove the boat builders clamp. and repeat the heating and bending operation on the other frame rail. Measure, measure, measure, and then measure one more time to be absolutely certain that you have bent both frame rails the same amount, relative to the centerline. Walk away---leave it for an hour. Do NOT quench the heated rails with water, oil, or blasts of air. that should get it done---It wouldn't hurt, if after everything is levelled, but before you start the heating and bending, to place a 100 pound bag of sand on top of the frame rail at each corner where it is supported on the box. This will lessen the chance of inadvertantly bumping the frame with your knee and moving it away from that very important centerline, and will also ensure that the frame stays flat and level during the heating process. I would also put in a temporary support under the frame rail about 12" on either side of the zone where you are doing the heating on each frame rail, so that they don't "sag" under their own weight when heated to cherry red.---Brian__________________

 

i'm thinking of building a new frame using 1/8" 2x4 tubing. two questions: 1, how do you pinch the frame and how far back from the frt. axle c/l is the pinch. 2. what is the best way to do the frame horns?

thanks
rer_239

 

Er---didn't you read the previous post???????

 

i did read that post, but i thought you were talking about an original unboxed frame. can i use that method on a 2x4 tube frame?
thanks
rer_239

 

there have been several threads showing building Model A frames from 2x4 tubing..

here's a link to one I did
http://www.jalopyjournal.com/forum/showthread.php?t=87556

 

Great Info Fello Canadien Terry From The Great White North

 

Thank you for all the information. I'll be rereading this a lot before I gather up the stuff to build my frame. Cheers Josh.

PS Now I know where to go if I get stuck.

 

I think that if you are going to pinch a frame made from rectangular tubing. you will have to take a cut thru the inside vertical leg,and maybe half way thru the top and bottom flange from that same inside cut, pinch the frame using the method I described previously, then weld up the cut. I doubt that you will get enough heat into a boxed section to get a smooth, distortion free bend without a relief cut first.

 

Rer-239, If you are copying the dimensions of a stock Model A frame, there is a bend on each rail, that resembles the pinch Brian speaks of, but it is located further back on the rails. You can, if building an "A" frame, (as opposed to pinching a Deuce frame) take about (3) Vertical sawcuts w/a hacksaw, (it amounts to one narrow pie-cut) starting on the outside face, let the three intersect at the inner INSIDE wall face of the tube. Then bend the tube rails toward each other. There is no need to cut the inside wall, simply use it as a hinge. This is similar to the pie-cuts that folks use to "Z" the rear frame region, only turned 90* upon application. For the front frame horn profiles, I used a cardboard template hammered against the stock A horn area, and traced the cutout upon the front tube ends. Then get a sawzall and cut the side wall "pie wedges" out, and bend the top face down along the dressed curve, making sure to allow for the 1/8th thickness so that the finished horn will copy an original frame.

 

I like the look of a suicide front-end, but I don't like the look of the round tube cross member. Is there any particular reason to use round tube instead of square?

 

Size for size, and assuming the same wall thickness, round tube is stronger than square tube. You can use a square tube, but don't go less than 1/4" wall thickness.

 

Brian,

This has been an awesome thread to read. I have a 31 Five window project and your info has helped to give me some direction.

I also believe you should publish a guide to fabbing up Model A frames... I would definetly buy one.

Again Thanks.

 

WOW i just saw this thread and i wish i would have about 4 months ago great info and brian thanks for the great great easy explanations.

 

Thanks Brian for all of that swell info. One point, I can't tell from the pics etc. just what the detail is of the coil spring mounts where they attach to the rear axle. How do you make these and how do they attach? Perley

 

Here ya go Perley. the plates are cut from 3/16" or 1/4" mild steel plate. The round part that the spring sets in is a peice of steel pipe about 3/16" to 1/4" larger in inside diameter than the outside diameter of the spring. There is a round plate in the bottom of it that sets on top of the two axle plates to make a flat surface for the spring to set on. there is a 5/16" or 3/8" diameter hole in the center of that plate for the end of a bayonet style shock to fit thru. This not only gives a place to attach the shock, but the shock also keeps the spring from jumping out of the pocket when you hit that 'Oh My God" bump. The side of the spring pocket pipe is welded to the axle on the side that is closest to the axle---this takes some of the torsional loading off of the welds on the spring plates.---Brian

 

Thank you very much Brian. I had to print it out and study it for a minute to see what I was looking at. The drawing is excellent and I see clearly now what I need to do. Best Regards. Perley

 

Brian, did you ever give your opinion on using 1/4 elliptical for the rear? Speedway does this on some of their frames.

 

I have never used quarter eliptic springs. I believe that there may be some space savings with them, and some fellows use the actual spring itself as the top link in a 4 bar set-up. If I offered up an opinion, it would be based more on guess work than anything, so I will bow out on this one.

 

Thank you for taking the time to post all this great tech and pics. It will come very handy and has already answered some questions and concerns I had about my model a project.

 

What a great post. Good stuff.

 

Brian,

I've been following this thread and I applaud your answer to the quarter eliptic spring question .

Too often, some guys here throw out information that's technically incorrect. There's nothing wrong with saying I don't know because of no experience in that area.

By the way, take a look at the chassis we built. Do an advanced search using my HAMB name and you'll find it. Please critique + or -.

Holy crap, I just noticed, this is my 2,001 post here!!!!!!

 

Brian,

This is simply the best post I have ever seen anywhere, on any subject, at anytime!

Than You for all the time you have devoted!!