[Rufus_2]

Greetings All,

I ve got a question about frame boxing. I have attached pictures of the middle and rear of my 37 Pontiac frame. I am planning to box the rear from the end of the X member to the crossmember just behind the rear axle. My original reason for this was because I planed putting a Triangulated 4 bar and needed the plate to mount the hardware. I also figured any strengthening would be good. This is where my question lies. Should I box the section between the first rear crossmember and the end of the frame. Also, Should I box the center of the frame between the front and back of the X-Member?

Thanks,
Rob

[327NUT]

A fully boxed frame is obviously stronger but it all depends on what kind of power you're going to run and what you're going to do with the car. If you have the welder, the time and the talent to use it then why not.

[adtkart]

On an older frame like that, I would box in all that you could reasonably. Just keep in mind how things will be mounted.

Aaron

[boatbob2]

Hi,when i boxed the entire frame of my 1934 ford pickup,i noticed the bottom,inside of the frame at the kick up,was very thin. i took a piece of cold rolled steel bar,3/16 thick by 2 in wide and welded both sides to the frame. then i ground off the outside edge,so it was the same size as the frame.it made the frame noticably stronger,then i boxed the chassis. im boatbob2

[MARTINSR]

I would seriously think about WHY the need to box it? Unless you plan on a LOT, I mean a LOT of horsepower AND sticky tires, fully boxing a thirties frame is overkill. ESPECIALY a thirties frame that has an X member.


Boxing CAN warp a frame. Caution needs to be taken when welding it. Skip around and don't weld much in one area at a time.

Look at all the forties and fifties pickups without any X member and simple ladder frames and no boxing that are on the street with blown big blocks and the like. A Model "A", that is a whole different story, but a late thirties frame, they are much taller and have much more support with wider mounting of the crossmembers. I would think about it long and hard before I got into it.

The X member is where the rigidity comes from, even MORE so than boxing. Do you see bridges with "boxed" beams? No, they rely on structual design, that is what the X member is.

The biggest reason for boxing on something like that is a warm gooey feeling and aesthetics.

Brian

[Rufus_2]

I agree Brian. That was my initial thought but I had the creeping feelings of doubt that made me want to check with folks more experienced. Speaking of the X member, I will have to make some modifications to the center to accommodate my transmission. The X is built with I-Beams instead of C channel and my plan was to take 4" front and 4" back of the center out to accommodate the tail shaft. I was going to leave the top and bottom of the I and take out the center. Once everything is removed I plan to add a box made of steel tubing to replace any strength I lost. Will this considerably weaken the X-Member. I will be using an Olds 455 and Turbo 400. I am looking to build in the upper 300 lower 400 range for horsepower.

Thanks for all the advice,

Rob

[powerrodsmike]

Sorry Brian, I got to dissagree with you on this one.

Anything you do to increase the rigidity of the frame is a benefit. If you can box the whole frame without warping it it will be a much nicer car to drive. those frames built in the 30'-40's were stronger than their predessors , but are not up to the task of todays higher horsepower, stronger brakes, stickier tires, faster freeway speeds...etc

I won't start to compare the tires,brakes, etc of yesterday with what you will inevitably put on that car and use today. Even mediocre tires and a stock 350 is worlds ahead of yesterdays stuff.

Every time you put more power from the car to the ground, being engine, steering or brakes, it demands more from the frame

Box it as much as you can stand.

At the very least, box it from 6" in front of the 4 bar mounts and run that all the way back to 6" behind the crossmember. Are you replacing the rear crossmember? I would think that you won't be using it with the new suspension.

When you cut out the center of the "X" member, put a peice of 1"x2" rectangular tubing all the way across, connecting the frame rails, and the new wider, box section that you will put in The closer you get to the outside of the frame with yourr replacement box section, the more rigidity you will lose, unless you make the box out of a rigid , unflexable material itself, such as rectangular tubing. One length of rectangular tubing on the bottom with a drop out trans mount will really help things.

I'd box the front also.

This should have been in the suspension forum, as we have no real "frame" forum.


Later, mikey

[Rufus_2]

Thanks for the advice Mike. The front is getting replaced with a Fatman Sub frame that is already made of square tubing. It will mate just in front of the X. I planned on trying to keep the crossmember in the rear because that is where the gas tank mounts and I planned on using an repro tank. That may change when I start mocking up the rear. I think I'm going to make 2 plates to cover the area between the back of the X to the end of the frame. My plan is to let the Rod shop that is replacing the front clip go ahead and weld the plates as well. I didn't want to risk the warpage doing it my self.

Thanks again to everyone.

Rob

[adtkart]

Mikey.... You forgot to mention that the frame he is working on is only 70 years old. There is no way it is as strong now, as it was when it was designed and built.

Aaron

[powerrodsmike]

Originally Posted by adtkart

Mikey.... You forgot to mention that the frame he is working on is only 70 years old. There is no way it is as strong now, as it was when it was designed and built.

Aaron

It's my way of being considerate.
I like to leave something for the other guys to say

I'm just kidding.

mikey

[MARTINSR]

Thats all good Mikey, it sure can't hurt to box it. But there are a LOT of late thirties cars with a full X member like that and work just fine.

Brian

[Henry Highrise]

Some folks used to think that a certain amount of flex gave a better ride. This is wrong...the stiffer the frame the better the ride as it lets the suspension work better. I would box the whole frame if it were me and I was not concerned about a little extra weight.

[powerrodsmike]

Originally Posted by MARTINSR

Thats all good Mikey, it sure can't hurt to box it. But there are a LOT of late thirties cars with a full X member like that and work just fine.

Brian

I think it was more the "warm gooey feeling and aesthetics" statement that I disagreed with.

I know there are a bunch of those cars out there that were built through out the years that are currently in service, but the more steering box and motor mount repairs that I do on those cars, the more I am convinced that if a guy has the chance, he should box his frame.

Especially if he has to cut a significant amount out of the center out of the X member. This takes alot of rigidity out of the frame.

Motor mounts get moved back away from the front crossmember, steering boxes pushing wider tires make the frame flex at that point. I have fixed the frames of several late 30's cars at the steering box mount.

Also, as adtkart pointed out, all of those frames have been through alot. Metal fatigue from thousands of cycles of flexing have weakened the steel.

I won't say that a guy needs to take his car apart and box the frame, but if someone has the car all apart, and as in the case of the op, is adding a fatman stub, then IMO, not boxing the frame would make his car less of a joy to drive.


Later, mikey

[MARTINSR]

Mike, as usual you make very good points. The forces just the wider tires with offset rims can make is pretty substantial. Especially with a cross link setup, the frame where the steering box mounts gets twisted.

And the X member does get cut up pretty bad on a lot of these cars for late automatics.

OK, OK, I give up!!!! Just kidding, I see your points and they are well taken.


Brian

[Sixguns]

I would like to see some more pics of your frame, to see if its built the same as my 36 LaSalle. I had Fatman build a custom Stub and also have Triangulated 4bar. It sounds like our builds may be close to the same idea. I boxed only the rear and Added welds to all the points where the frame sections are rivited together. Im very pleased with this frame, here is a pic of my mock up. There are a few more in my photo album.