The Stovebolt Site Forums The Shop Area Paint and Body Shop Frame rivet replacement

Hi fellows!!! A while ago I asked for replacement for frame rivets. In that opportunity several guys adviced me to try and not remove any rivets. Well, the frame was worst than I expected and had to remove the engine cross member and the next one. I'm wondering which would be the best replacement: Hex flanged bolts (grade 8)unfortunately I have just found coarse thread or ferry cap screws (12 point head with flange) this is usually ISO 12.9 class (higher than grade 8). This I found in fine thread. The flange in the hex head is bigger (13/16") than the ferry (9/16"). Which variable is more critical, the area of the flange (to distribute the force), the grade or the thread (so it won't slip). Thanks for any ideas.

Chinito

I'd say either would work fine, more than likely even Gr8 would be an improvement over original in strength. I'd go with fine thread and permanent LocTite. Whether bolt or rivet, most joints on a frame are primarily designed to work in shear, not tension, so the head size is not likely to be critical.

Good point, but aren't the rivets on the engine cross members subject to a bending moment? Also the supports for the cab are in cantilever making it also subject to a bending moment and thus to tension stresses. If so, would it be wise to use the ferry bolts or flanged hex on those particular spots?

You got me. Your pencil and mind are sharper than mine. Good analysis grasshopper. I would agree, however the magnitude of tensile loads is (go ahead, whip out your FEA iPad app and prove me wrong) probably insignificant compared to the shear loads.

Certainly the Ferry bolts would look high tech and aircrafty, but the hex with a good hardened washer would do the trick and look more original.

Remember though, any fool can over design something - it takes a good engineer to put it right on the edge of falling apart.

(and I did CMA with the phrase "MOST joints")

In one of my old Chevy manuals, it gives instructions on replacing a frame rail and using bolts instead of rivets to put it together. The instructions call for drilling out the holes to a new size which fits the shank of the bolt. I assume they are special bolts that have an smooth area on the shank for this purpose.

Farmer: Is there a FEA app on Ipad? I should get it. My concerns were merely to replicate the area of the rivet head with the area of the head of the bolt. That´s why I looked for either the Ferry bolts (you may be right, overkill) for the flange and for flanged hex bolts. I think it will look cleaner than a regular hex head and a washer. The other issue is the torque applied to the bolt, not for preload but chiefly for avoiding it to loosen up. If preload is no concern and I will be fine with loctite and a good lock nut, I'll go with a coarse thread grade 8. Thanks

Here's some information on using FRAME BOLTS in place of rivets. I think it's information that you already know, but it is shown with pictures and torque specs. It's a pdf format and will take a moment to load.

I thought I was kidding about the FEA app, . . .but

http://www.intesym.com/mobile.php


You've got the issue well in hand but I'd probably still err on the side of fine thread. I noticed the bumper bracket bolts were fine threads, and a little LocTite never hurts.

Holy crap, and I just spent 1000 bucks renewing our structural software at my office. GMONIZ document was extemely useful. I'll go with the grade 8 with hardened washers. Thanks ya'll for the help.

I picked up an old frame repair book by Bear Equipment, a while ago. In describing the installation of rivets, it said to put the rivet in place, heat the shank and then form it. I always thought that they were dropped in already glowing.

If you had asked me, I would have said the same thing. But thinking about it, you can get a tighter fit that way. A half inch bolt might expand .003-005" going from cold to glowing, if it was almost a press fit cold, this would help lock it in I suppose.

If you remember the Three Stooges films when they cooked their hotdogs where the rivets were heated. I also thought the rivet was heated prior to be formed, so when it got cooler and contract, it gave the preload needed on the joining pieces.

If they are about 3/8 Diameter, a SAE no. 5 would be way over kill let alone an 8. Even 5/16, a 5 is way strong. An 8 is a waste of money. The 5 will have a huge safety factor already. I am sure you are using more than one bolt on each frame rail. Just use an oversized washer on both sides and a lock washer against the nut and torque to specs and it will never break or come loose. Locktite is for high vibration. No. 8 hardware (or stainless) and lockite is for aircraft and rockets. We are all hyped by TV shows and their sponsors. You sometimes use locktite on a truck if you can't use a lock washer.

www.bigflatsrivet.com/catalog.html

Of course I remember the Three Stooges. Still watch 'em occasionally.

I was referring to radial expansion which would make for a tight fit in the hole. You're referring to axial contraction which may be more important in terms of tightness, and I think would not be impacted by installing hot or cold, as long as it was formed hot. Guessing at a yield of 50ksi the shrinkage from 1300F assuming two 1/8" pieces of steel is nearly 4000lbs.

Torquing a bolt to proper specs would likely yield a similar clamping force. Only problem then is how to heat your weiner.

yeah, you were thinking axial contraction, don't do that again!