Side pipe mounting with rivnuts

[Cutter 54]

I am finally ready to bolt in the under chassis support brackets and hangers for my Gas N side pipes on my Mark 4. Since I already have the cockpit carpet glued in I really prefer NOT to drill through the transverse "outrigger" square tube beneath the seats to mount the side pipe support bracket. Since the 2" square frame is 1/8" steel I thought that steel rivnuts inserted into the rear wall of that tube would be strong enough for support the 2 brackets on each side. Standard mounting calls for drilling through both walls of the tube from the cockpit side aft. Anybody try this?

I might even be tempted to rivet a piece of 1/8" steel plate to the rear wall of the outrigger for reinforcement and then tap the double thick wall to mount the hanger hardware. I mean, how much stress is there on the side pipe hanger bracket? Static weight is 10 lbs at most (I recently weighed both side pipes at 37 lbs. total), so with up and down movement at speed there might be ? 50 lbs, 100 lbs. on each pipe. I can probably hang my body weight of 185 lbs. on a bolt tapped into one side of one of those 2" square tubes without anything bending or breaking.

Share your thoughts. The question kind of reminds me of the issue of cutting out the diagonal 3/4" tube in the trunk area to install the drop trunk modification. Good idea? Risky? Stupid? No consequence? Multiple choice post.

Maybe I'll just do the experiment and see what happens.

Happy St. Pat's.

[JohnK]

Yes, I used 5/16" nutserts for the hanger bolts. Can't take credit for the idea - I stole it (along with a million other ideas) from Edwardb's excellent roadster build thread. You can see his post on it here.

[Cutter 54]

Thanks for responding John. I thought Paul was responsible for the idea, from a post I had read in the past, but I wanted to canvas others on the Forum. If it worked for him, I'm in.

Let's see if anyone else has comments. I'm curious.