Just wondering what some opinions are on whether or not crush sleeves are necessary in my application. I have made some subrails for my roadster body out of 1"x 2"x .120" steel tube, and I will be using the original mounting holes in my '32 frame. I don't really see any deflection of the top wall of the tubing when bolted up for test fitting, and the bolts are cranked down pretty tight (3/8-16 bolts zipped down with impact). Getting spacers in there without drilling an oversize hole in the top wall is not possible, so I'm not sure if I'd really be gaining anything or not.
Don't know if they are still available but I purchased two body mounting bolts from Speedway motors that use an expandable rubber bushing that gets captured into a hole in the top of the frame. I remember using similar mounts for luggage racks on station wagons.
I don't like the idea of it myself, especially in a wreck situation. Not only that but as the body and frame flex thru everyday driving, especially where I live, I can see the tubing slowly give way and crush loosening the bolts as they go. My first thought/ solution would be to take a holesaw and cut the top of the tube big enough to drop a shorter bolt thru it and be able to get a socket thru it. This would put the head of the bolt against the bottom wall of the tube and directly against either the rubber bushing or the frame rail... that's how I would try to handle it. If that wasn't possible the tube would definitely have a steel feral welded into it... ...
I agree with lostone. If you pass through the tubing without at least a solid spacer, the tubing will crush over time. Every automotive body mount to frame that I have seen has always had a hole in the non-mount surface large enough for a bolt head and socket to pass through. I have not personally seen where a factory has used a spacer through a tube for a body mount (light & shock brackets, yes, but not body mounts), but that doesn't mean they don't exist. I spent 28 years replacing bad body mounts in all kinds of cars and trucks, but I have not seen them all.
I have to agree that making sleeves and inserting them to keep the tubing from collapsing when you tighten the bolts or collapsing due to the crushing over time as Gene-Koning said. You don't have to take the subframe back off the body just find tubing/pipe that will just fit over your bolts, take a hole saw or step drill and enlarge the hole on the bottom to the OD of the tube, figure out what length you need to come out flush and cut to length and insert and tack in place.
The wrong way to do it (no sleeve) will work fine, just don't tell anyone that's how you did it. Put lock nuts on the bolts. Tighten them every year.
here in New Zealand, with the extensive regulations that we have, crush tubes are mandatory or you can do what @lostone proposes in post 3, (also below), providing the minimum dimensions are met for size and thickness of steel. Personally, I believe that by cutting what is essentially an access hole and only bolting through the bottom of the tube, will weaken the box tubing. And if the forces in an accident are capable of causing the box tubing to crush, (before ripping the bolt threads out of the nuts), I would think that you have bigger problems to worry about, but I may be wrong. Two thicknesses, even without crush tubes, make more sense to me, rather than just the bottom 3mm. to answer your question : (as others have said) Simplest and “SAFEST” solution would be to put crush tubes in !
Once I have everything bolted down conventionally I systematically drill out each mount to install a say 1" diameter metal slug. The slug is bored out beforehand, stepped at the bottom and countersunk at the top. Fully welded ( bottom done when body taken off). Strong as anything, consistent body alignment on reassembly and countersunk bolts mean no raised bolt heads making for easier upholstery. I find the advantages make it worth the effort. Chris
the funny thing about all of this is that a bolt going through two pieces of 1/8" steel is still way stronger than any body mount made on any OEM car, even without the spacer between the two pieces of 1/8" steel. I love how we have to overthink everything.
My first pair of 32 homemade rectangle sub rails were anchored using Allen head cap screws by drilling through the tubing 3/8" or 7/16" depending on your choice of fasteners, then redrilling the top side only to permit the head to pass through & simply accessed & secured using an Allen wrench as intended, no collapsed tubing or spacers required. I used 16 ga. rectangle tubing the same as the 32's, were I to make another pair it would be done likewise.
@ShortyLaVen per @squirrel, are your bolts going completely thru the frame? A little lost since you mention the top of the frame twice but not the bottom. Then there’s not wanting to drill the top bigger for a sleeve which would mean there is a bottom hole???
“Hold the Press’s” your title say’s through. If you really want a sleeve. Wouldn’t making the hole at the bottom make more sense? But like @squirrel said, your body is going no where.
Most frames were "C" beam< EZ to just drill n bolt though,but after boxing=same as tube ; So I always welded tabs n bolted through those{ Often used a cut belt for under rad. ,an rubber pad for body cut from side wall of tire.***=about 1/4inch thick/be sure all are same thick. { coming out of same place of side wall]. Never really had $ for store got,factory type,and being no one can see,that OK.
@squirrel Here's a couple pictures of what I'm working with. The frame has nuts welded inside the rails in the factory '32 locations, which is what I'm bolting the subrails to. Basically I made the subrails from 1"x2"x.120" tube the same shape as the frame, then cutaway what was left of the factory Model A subrails until the body sits where I want it. The bolts are going through the top and bottom holes of the 1x2, into the weld nuts in the frame rail. My original line of thinking was that passing through both layers of the tube means more meat the bolt is passing through, as someone else mentioned here. But of course, talking to different friends about hot rods, everyone has their own idea of whats right/wrong, so that's why I made the post here.
That won't ever move if you don't install sleeves. But with the workmanship involved in making those subrails, it seems that putting sleeves in is just a natural thing to do, to fit in with the rest of how the car is built. Even though it's totally unnecessary.
I'm for using inserts like @anthony myrick posted ..........OR a somewhat similar method I like is to insert some bar stock inside the rail thats maybe 3" long and nearly as wide as the inside of the rail. If its box tubing, its a little harder to do, but not that much. Simply insert the bar stock where you expect the body hole to be needed. Then when you place the body on the frame, mark the exact location of the body holes and drill and tap to fit. The actual process I would use if its box tubing is to drill 2 holes in the box tube and get the burr off the inside surface so the steel will lay flat. A good way to do that is drill undersize and then finish with a small reamer(in a drill) ....usually leaves no burr. Turn the box tube upside down and drill a small hole so someone can push down on the steel plate. Weld each of the two holes with a rosette weld and the steel plate is secure. Then weld up the small hole you used to push thru. This is a little more work, but it allows you the ability to then drill holes that exactly match the body and frame and the extra thickness of the plate gives plenty of strength to hold threads. I'd use 3/8" plate. There are lots of ways mentioned above that will work, this is just how I prefer doing it as it gives me the ability to adjust locations of holes if needed rather than where a drawing says the factory put the hole. We often assemble things that did not originally come from the same source, so it may be necessary to make allowances for mismatches.
That's quite a compliment, thank you! We're just doing the best we can with the tools we have. I hate to use the phrase "cutting corners" as such, but I am on quite a bit of a time crunch to get the car done by the end of the year with the small amount of time that I have to actually work on it. I'm just trying to budget that time as efficiently as possible. A day spent welding in unnecessary sleeves could be a day spent fitting up doors, or building the transmission crossmember, etc. The sub rails did come out looking pretty fancy, but in reality its just a bunch of pie cuts and welding. Here's a pic before we ground them down. And I know what your thinking, that's a tedious way to do it, but I started them quite a while ago before I had the deadline to finish the car. Maybe that makes zero sense, but that's the way it goes.
at least you got in a lot of welding practice! I wouldn't bother with sleeves, hearing the situation you're in.
What I did was to get a flange head nut, drill a hole in the rail with a stepped bit just far enough so the nut will drop in but not through and will end up flush. Weld the nut in the hole. To see how strong this was I did the same in a cutoff piece of tubing. Then tried to get it to fail. The tubing finally tore, but it took a lot of force.
the most simple thing to do is just drill a big hole in the top of the tube, so the bolt only holds the bottom layer of tube, and you can get it fully tight. But still, 1/8 wall tube even with a little crush is still way overkill for the job it has to do.
You obviously know how to weld, so what is the big deal with installing crush sleeves? They may or may not be needed, but is the right way to do it. Do it right the first time. Not everything is worth doing twice...
That's exactly what my advice was above, simple to do, easy to do at this point and I like the idea that the bolt is clamping metal to metal surfaces. It's simple and effective, takes 10 minutes and costs nothing... I over engineer, too many years fixing wrecked cars and seeing how things move and crush when getting hit. I've seen things that I thought couldn't or wouldn't happen, happen. ..
Yes. Me too. 1" x 2" tubing crushes a lot easier then you think it can. If it looses 1/8" of its original thickness where the bolt passes through, the bolt will be loose and allow movement between the two pieces of metal that are suppose to be tight. That can be the source of a future failure. If you can tighten a bolt a year later that passes through a tube that is not reinforced with at least a sleeve, you know the tube is already crushing. Your build is compromised. It may live all of its life without issues, or it may fail when it needs to be at its strongest point. I'm not going to take that chance with something I build for me or someone else.
Definitely worth the effort to weld in some tube sleeves…the body getting loose isn’t anything you want in the future.
Steel 3/8" Rivnuts will do just great. They are rated at 610 pounds pullout capacity. This X the number of fasteners (8?) Will give you almost 5000 pounds of pullout capacity. You're going to have bigger problems if you reach that limit.
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