I am planning the installation of bucket seats in my '39 Ford. The seats I found (out of a '96 Mercury Villager) are 1 1/2 inches lower than the stock '39 Ford bench seat and the bolt holes are 12 inches apart for the '39 and 14 inches apart for the bucket seats. I plan on using 2 inch square tubing to raise the seats up and will have to compensate for the bolt hole difference between the old and the new. Can I use a Rivnut or Helicoil to make a blind threaded connection? Will the Rivnut or Helicoil hold the bucket seats in place with no further problems? Safety is a real issue with me. Is there a better way to do this? I would weld in a nut but I want a flush fit and I don't think I would be able to weld inside the 2 inch tubing.
I don't think I would trust either one, the seat could come loose in an accident. Can you through bolt the whole thing with long bolts down through everything and put a large fender washer on the underside ? It is hard to offer an opinion without actually seeing what you are working with. Don
How thick of wall tubing are you working with? I would go with a rivnut anyday, I dont see how you're going to have enough wall thickness to work with for a helicoil. We use rivnuts to hold F-16 panels down, so they work pretty well
This could work as well, how are you attaching the tubing to the floor? But yeah a photo would probably make it easier to help you, not sure I understand completely.
like Don said. When I put in seat risers, I put matching 1.5x angle iron under the floor. You can feel the difference. That floor pan metal is probably old, a little rusty and has been flexed many times.
Don't use any hardware smaller than the stuff that comes with new cars / belt kits. While it's best to bolt your seats to the frame some way, there are special, custom-shaped oval plates that are made for use on the bottom of sheet metal floors as bolt anchors. These plates are far better than just big flat washers. But I'd only use them as a last resort, and only on the front pair of mounting bolts - remember that you could be in a crash from the sides or rear, too. Gary
Picture a 2" square tubing, 1/8" wall (or so, let me know). On the top are two holes with Rivnuts in them to hold the seat down, spaced 14" on center. On the bottom of the square tubing are two more Rivnuts, spaced 12" on center. Bolts come up from the bottom (w/ red lock***e) to hold the tubing to the floor. The seat is placed on the top and then bolted down (grade 8 bolts) 14" apart on the square tubing. This is basically what I'm thinking. I had thought of drilling though the 2" square tubing to be able to directly bolt down the seat to the tubing and then through the tubing (top to bottom) to secure the tubing to the floor. My hesitation is that the holes drilled will be less than 1" from each other and raised a red flag in my mind.
Can't you just put new holes in the floor, 14 inches apart, and bolt all the way through the seat, tube, and floor, using the 2" tube strictly as a spacer?
I agree with the 1/4 inch wall suggestion. The insert would still only be holding by 1/8 even if it were 1/2 long.
As far as the holes in the floor go, how about a 100mm (4") square plate 3mm (1/8") thick underneath and also one inside for each hole, like a sandwich, to spread the load since the other hole is so close.
With through bolts use a crush sleeve in the tubing to prevent the tube from collapsing. Helicoils will not work period,and I'm not a big fan of Riv-nuts in a application like that. I would make up and weld in some sleeve nuts into the tubing myself.
I would cut the tube to 2 " and run the bolt through the tube with a washer on top and bottom of the tube. then run a plate across the underside across from one end to the other.
Okay, a few thoughts: What diameter bolts are you using? 1/8in wall steel is reasonably hefty for that application, and the big issue with a rivnut is the stability of the hole it's in (because it doesn't have a lot of bearing surface on the back side of the material) so the more rigid the material the stronger the joint. You're probably in good shape with 1/8in wall tube, but I'm not a certificated engineer so take that for what it's worth. I find tons of uses for rivnuts but the big problem I, personally, have with them > 1/4in is that it really takes a big ****in' tool to set them properly, preferably air/hydraulic, and I haven't convinced myself to spend the money on one yet. If you're looking for something with more clamping surface and your square tube rails are open on the ends, weld a sheetmetal tail onto a hex nut, then insert the nut by its tail into the end of the tube while you thread the bolt. You could even drill a hole in the tube and plug-weld the tail in place once the nut's properly aligned with the hole. You can get weld-in nut plates of similar concept (if you can reach the inside of the hole to locate them) from McMaster-Carr. Thread a hole in the end of a piece of flat stock, screw a short stud thru the nut plate and into the tapped hole in the flat stock, drill a couple 1/4in holes next to your bolt hole in the square-tube rail, stick the whole thing down the end of the rail and pop the stud thru the bolt hole. Put a nut on it to snug the nut plate in place, tack the plate thru the 1/4in holes, unscrew the nut and stud, complete the plugwelds, then repeat for the rest of your holes...
Crush sleeve in the tubing and a plate on the bottom seems to be the way to go for me. Thanks to all for the advice, I learned a lot about something I've never done before.
I don't think a panel on an F-16 will have any where near the same kind of Stress Impact Load as a seat, especially in an accident. Or am I missing something in what you are doing with the F-16?
Consider the Rivnut , but forget the helicoil for this application. Sounds like the long bolt through everything may be best.
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