I have posted this on a Flatheaf formum at Yahoo! groups, but I have disappointed by the quality of the replies.
I am helping a friend restore a '38 Ford pick up. The original front crossmember was broken, and since it had been previously patched, it seemed prudent to replace it. He has located a NOS crossmember. The question I have is, "How should it be attached?
The oem method was rivets. Some peole weld them in, and others prefer bolts with some sort of locking nuts. What I am seeking is some discussion of the relative merits of these various methods. Opinions are OK,( "weld it", or "grade 8 bolts") but the discussion is required to understand the "why" of each method.

Michael
Bel Air, MD

In my opinion Ford used rivets so the frame had a certain amount of flex, much like a ship's riveted hull. If it is welded (I have seen welded ones that broke) it won't flex at those points over uneven terrain and will likely break. On semi trucks there is usually a tag on the frame that says No Welding. They use bolts and or rivets.

__________________
1983 300-D turbo
1985 300-D turbo
1959 Harley Panhead chopper
1929 Ford coupe restored
I hang out with Boneheaddoctor at Schuman Automotive OBK#5
All liberals are mattoids but not all mattoids are liberal.

Thanks for starting off the discussion. I think many late model frames are made of heat-treated steel, and the heat of welding would compromise the strength. I am not sure if early V8s had any heat reatment of their frames, so that caution may not apply.
AFAIK, rivets are very strong when properly installed--If the rivet is at a red heat, then it has stretched a bit--just due to its temperature. If it is installed and peened while still stretched, it will shrink as it cools and become VERY tight. I am not convinced that you can tighten even a grade 8 bolt to provide that same clamping force. But thats what this thread is for. I am looking for comments on the relative merits.

Should be able to get at the HAMB - it's a hot rod forum, but they should know what's up.

http://www.jalopyjournal.com/forum/

Click on 'Hokey Ass Message Board'. Let us know how it works out.

PaulC
Part of the problem is that my friend, still can't make up his mind. One day he's talking about an authentic restoration, the next, he's thinking about boxing the frame and installing a SBF with Air and power steering. Then, he has mentioned just putting the '39 body on a late model frame. I don't know what he really wants; he doesn't know what he really wants, but when I discovered that the original crossmember was beyond repair, he didn't hesitate to buy a new cross member. I think if we get the frame done as per original, and it is stable, he might stay with the restore idea. I believe part of his reservation is due to how much the frame rolled. Stepping on the running board would cause the body to roll a lot. That was due ( I think) to the broken crossmember. So if we get that fixed, it should be OK.

I agree with the comments regarding grade 8 bolts.

I have over the years restored and otherwise maintained countless early vehicles,chiefly pre-29, and chassis rivetting was done of a purpose.

My Vauxhall is a prime example,in all essentials it is an Edwardian design,deriving from the Prince Henry 3 litre,with a correspondingly flexible chassis.

While the Vauxhalls could not be beat in straight sprints and hill climbing their somewhat flexible chassis robbed them of any easy handling above 75-80 MPH.

many have tried welded members but the penalty was cracked joints as if in rebellion to the welding.

I have found that grade 8 bolts,welded at the nut-bolt joint are more than sufficient for durability and flexibility,my InterState being a prime example.

__________________