A slightly different approach to lowering seats

[Chuchuf]

For years I have had the seats lowered by bolting them directly to the floor. I have never liked this approach for obvious mechanical reasons but also because it makes taing the seats out and reinstalling a PITA!!
Not having the tools to weld nor wanting to learn and do a sloppy job, I decided to take a different approach after I read about using rivnuts on the tunnel to avoid heating up the fuel lines. Thought I would share it with the community.
I am very familiar with composites and have built many many things out of Carbon Fiber (CF) for both extremely light and strong applications as well as structural members for experimental 200 mph aircraft, so I thought I'd try this approach.
The goal was to lower the seat rails about 1.5" and have them adjustable up to 2" further to the rear with 3 sets of mounting holes and floating captive nuts. I also wanted brackets that race seats brackets could be bolted to if someone wanted to.
To do the CF I made a mold by gluing two pieces of scrap Corian together that were about 4" wide and 24" long to make a 90 like an L bracket. The corian was then cleaned and waxed with Partal wax and then some release was put on.
I used some CF I had on hand and decided that I wanted a layup that was about 0.17" this (probably overkill, but the additional weight wouldn't be noticed), with some of the carbon on a 0/90 deg layup and some +/-45 deg. That way I would have good strength in all directions.
With the carbon I had this would take ~17 pieces stacked on each other. I started by wetting out the corian mold with West 205 and Slow hardener and then proceeded to put each layer in the mold being careful to throughly wet them and make sure the corner was pushed down (sorry no pics as my gloves have resin on them).
Once all the layers were applied, a layer of perf release film is applied and then some heavy breather cloth to soak up the excess resin. This assembly is put in a vacuum bag and a vacuum applied. The resin was allowed to cure for 24 hrs and then put in a home made "hot box" to allow it to post cure at about 160 deg F for another 8 hrs.
The result is a very stiff strong pat that I then trimmed from templates I made from poster board. Hard point were made by oversizing the mounting holes and filled with a splooge of resin, cabosil and flox, then the holes were re-drilled.
In the pictures the mount are temporarily held in place with sheet metal screws while I wait for the M8 rivnuts to get here. Along with the bolts, the rails will also be glued to the chassis which should make a joint stat is stronger than the CF.
For the seat mount nuts I will be using floating M6 nuts that I believe will be riveted in place (haven't found the nuts just yet, need to look at Aircraft Spruce catalog)
Terry

[Elombard]

At first I thought - this will be brittle and could fail in a wreck.....then I remembered the seats are made out of CF or FG. Only as strong as the weakest point.

If you glue the mounts to the tunnel they wont be moveable? I thought you wanted to be able to move them 2" back if needed?

Can you remove them if they are glued - with out getting too crazy? I like this way better than welding against that tunnel with out adressing fuel lines (like id did - roll eyes).

Another thought we cut off the stock mounts like you did and made a frame with 1" square tube and some flat.

I wonder if you could use the square CF tube that is available to cross brace for added strength or maybe even instead of the custom brackets you made. I have never looked I suppose the CF tube is $$$

I love this and I am going to go this route if I ever do it again.

[Chuchuf]

Originally Posted by Elombard

At first I thought - this will be brittle and could fail in a wreck.....then I remembered the seats are made out of CF or FG. Only as strong as the weakest point.

If you glue the mounts to the tunnel they wont be moveable? I thought you wanted to be able to move them 2" back if needed?

Can you remove them if they are glued - with out getting too crazy? I like this way better than welding against that tunnel with out adressing fuel lines (like id did - roll eyes).

Another thought we cut off the stock mounts like you did and made a frame with 1" square tube and some flat.

I wonder if you could use the square CF tube that is available to cross brace for added strength or maybe even instead of the custom brackets you made. I have never looked I suppose the CF tube is $$$

I love this and I am going to go this route if I ever do it again.

Erik,

No I don't think that the CF will be to brittle and the failure modes looks like and they flex quite a lot before breaking. Mine are stronger that steel of Al of the same size so they should be plenty strong enough. Planes, cars, spars, racing sailboats and many other things are being built from this stuff.
Yes the intent is to permanently glue and bolt (M8's) the rails to the tunnels. My feeling is that I wanted lots of surface area to apply the stress to. So taking them out won't be an easy option. They will be part of the car just like the original seat mounts but ~1.5" lower. The glue I'll use will either be Hysol or a 3M made for composite to steel.
The way I'll be able to mount the seat up to 2" further back is I'll have 3 sets of mounting holes with nuts on the top. The front ones in the standard position and then two more 1 and 2" back. So if you need more leg room no problem. I made the mounts almost 18" long for that reason which is a bit longer than the stock mounts.
I choose this method because I am familiar with working with CF, molds, etc. I wanted the seats to be easily mounted just like the stock ones, be adjustable back, and provide a surface that you can mount any other type of mounts to.
Sure I could have purchased CF L channel but in my case I could easily make my own.

Terry

[porsche930dude]

you can use old hockey sticks for cf tube I would think.