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Mounting seat to sheet metal


trigun7469
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3.3.3. All seats or seat-sliders must be securely mounted to the floor or roll cage to avoid separation during a crash. All mounting hardware must be SAE Grade 8/Metric Class 10.9 or better and a minimum 2-inch diameter or larger steel plate or load washers are required when mounting to sheet metal.

 

Trying to get the seat to the lowest point has anybody mounted the slider to floor using a larger steel plate (champcar legal)? If so can you please post pictures.

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I don't have pictures,  but you just bolt through the sliders with big washers (or steel plate above and below the floor sheet metal.  No sharp edges (try not to use any metal with sharp corners, cause they can poke through the thin sheet metal of the floor).

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I am 6'4" and have a first gen rx7.  We actually cut out the floor and welded in a 1" pan and then mounted the seat directly to the floor.  We used big fender washers.

 

If your team is relatively similar sized you can just mount the seat directly to the floor to get clearance and then use foam cushions for your shorter drivers.

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3 hours ago, wvumtnbkr said:

I don't have pictures,  but you just bolt through the sliders with big washers (or steel plate above and below the floor sheet metal.  No sharp edges (try not to use any metal with sharp corners, cause they can poke through the thin sheet metal of the floor).

 

That's how the seat was mounted in our old car.  The seat back was leaned slightly.  After the crash the floor was completely deformed from the pressure of my butt pushing the seat pan down/foreword.

 

Factory floor material really isn't strong enough to properly support the seat.  I hate to imagine what would have happened if I'd had a reverse impact where the floor had to carry the majority of the stress instead of the belts doing the work.

 

The new car uses square tube welded to plates welded to the vertical parts of the tunnel and door sill.

 

If I had to do a floor mount seat again, I'd cut out the whole floor section and do a pan out of heavier gauge steel.

 

Remember the seat mount is the only thing restraining you in a side or rear impact.

 

How much force do belts have to absorb?  This much VV...

IMG_20190612_185124255.jpg

Edited by SonsOfIrony
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True dat!

 

If you can, use some square tubing on the floor welded to the sills and trans tunnel for the front at least.  It will give you angle AND help shorter drivers get higher when they move forward, AND help carry the load in side or rear hits.

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I saw a kit the rally guys use with tabs welded to round tubing to mount the seat brackets and large square plates with a large hole in the center.  Cut the tubes to length to fit between tunnel and rockers, then plate is centered by the tube, weld plate to rocker and tube to plate.  Allows you to add recline and move the seat closer to the tunnel if needed.  I'll search for pic and edit post.

weld_in_seat_rail_kit.jpg

Edited by TimS
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We used a square piece of 3/16" sheet metal large enough to catch all 4 factory seat bolts, then bolted the seat to that. Lower than any bent sheet metal seat mounts, uses the strengthened areas for the stock seat, and it's low enough to make hooking the anti-submarine to the eyelet nearly impossible without removing everything. A hole is cut a in the sheet to allow the belt to go down to a factory cross brace where the eyelet is welded to the floor. 

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On 2/7/2020 at 4:39 PM, Alex3000 said:

I am 6'4" and have a first gen rx7.  We actually cut out the floor and welded in a 1" pan and then mounted the seat directly to the floor.  We used big fender washers.

 

If your team is relatively similar sized you can just mount the seat directly to the floor to get clearance and then use foam cushions for your shorter drivers.

Another 1st gen RX-7 here.  When we put my seat in we cut the tunnel and squared off the floorpan on the driver side.  This effectively lowered the rear of the seat over an inch and added a piece of angle that runs from the factory front seat mount to the rear bulkhead on the floor.  The right rear bolts through that angle, and the left rear bolts through a plate big enough to be a roll cage foot.  The fronts just bolt through the factory seat mount and floor with large fender washers.  

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On 2/7/2020 at 3:07 PM, trigun7469 said:

 

Trying to get the seat to the lowest point has anybody mounted the slider to floor using a larger steel plate (champcar legal)? If so can you please post pictures.

We welded plates under the floorboards to mount ours.  Keep in mind you have to be able to see over the hood. We got ours all the way down only to raise it because of the view. But then again we run a Gen III firebird with a loooong hood.  before you do a lot of work make sure you want it that low. 

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On 2/10/2020 at 10:26 AM, TiredBirds said:

We welded plates under the floorboards to mount ours.  Keep in mind you have to be able to see over the hood. We got ours all the way down only to raise it because of the view. But then again we run a Gen III firebird with a loooong hood.  before you do a lot of work make sure you want it that low. 

Haha yeah, our sight line is basically just above level with the bottom of the windshield.  It's actually good because it doesn't allow the bad driving habit of looking down in front of the car. Not an option! 

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