Mounting Plate - Radius Arm Cup installation

vrracing · Post by **vrracing** » Tue Feb 04, 2014 10:52 pm

I am replacing the mounting plate radius arm cup and thought it would be pretty straightforward as I'd read all the discussions about fancy no-longer-available fasteners, screws, warnings about not welding the plate to the floor, etc. Cut the rivet things and it should slide out...

My floors seem to be original as they blend smoothly into the inner sills and have the hex pattern under the sound deadening, etc.

The back part of the mounting plate seems to be welded to the vertical sheet metal that forms the front of the IRS tunnel. Does that seem right? There is an indentation in that vertical panel for the mounting plate to inset in so the floor remains flat.

I've almost finished grinding out the last remnants of the back end of the mounting plate. When I put the new one in should I drill plug weld holes and weld it back in along the back edge? I thought they weren't supposed to be welded in.

If there are any writeups on this I'd appreciate any pointers.

Thanks,

Jim

christopher storey · Post by **christopher storey** » Fri Feb 07, 2014 12:53 pm

When new, they were fastened by deformable /shearable aviation type fasteners so as to limit the damage to the floor in case of accident . The nearest thing we have to them are Huck Bolts but the difficulty can be that a very special tool can be needed to get the bolts to tension and the rearmost pair are concealed on their interior ( upper ) end by the dished wells behind the seats , thus requiring a hole to be cut in the dished panels to get at them . Some of the restorers do in fact weld the rear edge and with some hesitation I have done this on my 1969 car

vrracing · Post by **vrracing** » Fri Feb 07, 2014 3:31 pm

Thanks, Chris.

I already have the dished panels removed.

I ground off the rivet things but the driver side radius arm mounting plate (RAMP) seems to have been welded or otherwise fused at the back edge to the vertical sheet that forms the front side of the IRS compartment. It looks like it is supposed to be in a recess in that vertical sheet and sandwiched between the flange on that sheet and the floor.

I expected them to slide out with the rivets removed. I'm wondering if that's normal because I am replacing the rear floor on the driver's side but I don't need to on the passenger side. But if the RAMP doesnt just slide out after the rivets are removed, then I'll have to do a lot more panel separation on the passenger side than I was planning.

Thanks!

jim

christopher storey · Post by **christopher storey** » Fri Feb 07, 2014 7:05 pm

Jim : my guess is that the cups have been replaced on a previous occasion -- they don't last forever, my last failure of one being wherea replacement which was welded had completely rotted away from the inside where the eggcup joins the heavy flat plate . Thus, like you, I had to get the angle grinder out to cut/grind the weld of the plate away from the floor/flange. It was a very unpleasant job but in fact didn't take more than perhaps 1 hour and did no damage to the floor/flange. I then fastened it with small metric nuts and bolts ( about M3 - or 5/32 inch or so ) and then seam rather than plug welded along the flange you have spoken about . Incidentally, when you say "slide out" this implies to me some horizontal movement . They should in fact just fall off vertically once all fastening is eliminated

vrracing · Post by **vrracing** » Fri Feb 07, 2014 9:05 pm

Actually, it's the "heavy flat plate" that I'm referring to as the RAMP or Radius Arm Mounting Plate. The cup just dropped off once I cut the rivets. I expected the RAMP to just slide forward.

Here's a picture of one of the new, uninstalled RAMPs.

The driver side cup just had a little surface rust inside. The RAMP was all pitted. I decided to replace the RAMPs with the thought that capillary action would draw water out of the sound deadening felt and between the RAMP and the floor sheet metal. Surprisingly enough, the floor sheetmetal was fine.

paulsco · Post by **paulsco** » Sat Feb 08, 2014 10:47 am

Hi Jim,

The plate you are referring to is spot welded to the floor panel and seam welded at the rear and to a box section at the front where the curved panel joins the floor. To replace this without cutting the floor will be a major task.
Hopefully my photos will be of some help

This is the plate from the inside; it is spot welded to the floor.

This is the box section area; the plate is seam welded to the tab on the small box section and the floor and the plate is seam welded at the back at the front of the chassis leg.

I have bolted and plug welded the cup on.

This is an original cup prior to plug welding; you can see that it was originally spot welded and riveted to the floor.
I have used high tensile bolts with lock nuts and plug welded it.

I hope this helps.

Paul

christopher storey · Post by **christopher storey** » Sat Feb 08, 2014 6:18 pm

Paul : it's perhaps a little academic now since most of the restorers do weld the radius arm cup plate to the floor ( which is what I thought Jim was talking about ) but the factory originals were not welded at all - they were designed to shear the fasteners without transmitting a linear load to the floor in an accident .

paulsco · Post by **paulsco** » Sat Feb 08, 2014 7:04 pm

Christopher,

I know; we have had a discussion on this on JagLovers before, but it is clear to see that on this cup which I am certain has not been tampered with, clearly has spot weld indentations??

Paul

vrracing · Post by **vrracing** » Sat Feb 08, 2014 8:40 pm

Thanks, Paul.

It's interesting that my driver side RAMP and cup were definitely not spot welded to the floor.

Mine did have the weld connecting the stiffener tab to the top of the RAMP identified with the shorter yellow line.

For the back edge of the RAMP weld, there are three layers of metal between the floor, the RAMP and the vertical piece. So is that welded from below and outside of the car along the butts of the three pieces of metal?

Thanks,

Jim

vrracing · Post by **vrracing** » Sat Feb 08, 2014 8:46 pm

Thanks, Christopher. Yes, my RAMP and cup were not welded to the floor except at the back of the RAMP which surprised me because of all the discussions I read on the plates.

Thanks, all.

paulsco · Post by **paulsco** » Sun Feb 09, 2014 12:22 am

in a word; yes.

Paul

vrracing · Post by **vrracing** » Sun Feb 09, 2014 1:43 am

Cool, thx.

Since I'm waiting for the new rear drivers side floor to arrive from SNG, I decided to pull out the odd looking driver's side footwell. I have replacements but have been focused on the back of the floor. It turns out the original had rusted so they built a replacement and welded it under the original one, globbed tons of weld under the car to seal it and then lathered it it with seamsealer. The welds were 12-14mm thick all around the outside edge of the footwell. After 3 hours of grinding I think I still have another hour to go.

If everyone thought to themselves "Will this make me the DPO?" classic cars would be more enjoyable!

vrracing · Post by **vrracing** » Fri Feb 21, 2014 1:50 am

thought yall would find it interesting that the SNG rear floors come with seat rails, seatbelt mount and the RAMP pre-installed. They spot weld the RAMP to the floor.

The seat rails have fore and aft bolt holes which is different than my stock ones. I thought that was interesting.

And the black primer is just for shipping. Got a little stripper on it and it ran off like mud! The beige primer they put on the footwells was really tough stuff. My 19 year is still cursing it.

Jim

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