Seat back brace

[HoustonNW]

At the dyno day tech Al noticed that my bling carbon fiber seat had expired and I needed a seat back brace. The roll cage cross bar is too high to mount the IO Port brace normally. This might work however:

From the side:



From the back:



The centerline of the brace is about even with the bottom of the harness holes. Al said that the seat back brace is not just for rear impacts, but side impacts also. For that reason, I think that any strength lost from having one of the mounting bolts between the harness holes is gained by having the brace bar so short.

My questions, not necessarily in order of importance:

1. Will this pass tech?

2. Is this a good idea?

I'm not sure if I can get an extra cross bar welded to the cage on this short notice, so if this doesn't pass tech (or is a really bad idea) I'll have the miss the weekend.

[marshall_mosty]

Wayne,
I think that will be fine. The CCR really only addresses rearward movement from a rear-end crash. All your upper torso loading will be trasnmitted primarily through your shoulder blades, which should lie approx at or slightly below the harness holes in the seat. The mount being situated directly below that point would allow a load path which should not put the seat in any wierd bending that would be detrimental to the function of the seat. Just use some big washers on the forward side of the seat and obviously pan head bolts, as to not create anything that would hurt you if driven into your back at 100G.

From the CCR

15.6.22 Seat Back Support
A seatback support must be made to hold the seat from going back in the event of a
crash. A plate should be used to distribute the load. No bolts, corners, or sharp objects
should be placed in such a manner that could lead to a possible puncture of the driver in
a high impact crash.

[Mrs. Crumpacker]

Just use some big washers on the forward side of the seat and obviously pan head bolts, as to not create anything that would hurt you if driven into your back at 100G.

I was thinking the same thing...but I don't know how the "normal" seat braces work...I was imagining the bar possibly impaling the driver (just from a look at the pictures posted). However, I am just a track wife. I don't really know a lot about the physics of some of this stuff

[marshall_mosty]

Darcie,
The bar breaking through the composite seat is something that many of us have wondered. Carbon fiber is very strong, but the strength depends on lots of factors (fiber type, layup angle, composite thickness, resin used, etc). I would build as large of a backing plate to distribute as much of the load as possible into the seat and not localize any of the loads just at the small IO Port plate.

[Al Fernandez]

Wayne, that will work fine.