Seat Positioning

[tony barnhill]

Back to the thread where I was discussing my roll cage...After the comments there, I realize I need to raise the rear of my seat about 2-1/2" to make the opening for my harness at the correct place on the main hoop cross member where the harness will be located.

I've got plenty of vertical room to do that:

I also like how Nial raised his seat & plan on copying his idea:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]The "riser-bases" started out looking like the drawing below. Made from 1/8" aluminum. The red areas are folded back 90°....The upper red area bolts to the bottom of the seat. The lower red area bolts to the floor. No real adjustment.[/QUOTE]

Now the 1st dumb question (& its purely a mathematical calculation or personal preference question, I'm sure). Oh, my seat is the 10° layback model.

<span style='font-size: 12pt'>Do I also raise the front 2-1/2"? Or, should I add a little more tilt over the 10° built into the seat?</span>

& the 2nd dumb question. I'm thinking about cutting the left 'wing' of the seat )the rib protector I guess its called) back by almost half to make it easier to get in and out of the car?

<span style='font-size: 12pt'>Does anybody see a problem with doing that?</span>

 

[Bugeye58]

Tony the rake angle of the seat should be wherever it's most comfortable for you.
Jeff

 

[blkcorvair]

I got a 20 deg. layback which is still pretty upright. So if you got a 10 deg layback Id say kack it back a bit. You really need to play with that and your steering to find your comfort angle. Remember its not too adjustable after it's installed. Also be aware that most sanctions like 2" clearance to the top of the cage from the top of your helmet, so see where that lines up.

 

[tony barnhill]

John Prather was over today going over my car with a fine toothcomb using the various historic racing rules - he actually didn't find alot I need to change! But he had some good ideas.

We spent a long time on the seat - me sitting in it with my helmet on; him measuring the angle of my shoulder belts & the room I have above my helmet (right now a little over 4"); clearance from my helmet to the cage top side bar, etc....I've either got to raise it and/or enlarge the belt openings in the seat.

I really like where it is right now & am thinking about just enlarging the openings & living with the angle of the harness shoulder belts.

 

[Greg_Blake]

Or you could keep your seat where it is and add a short bar under your existing horizontal at the right height.

 

[JerryB]

Tony:

You do not want your shoulder belts at an "UP angle" coming off your shoulders. Reason...your body can move upwards and there will be some spine compaction in a very hard hit.

You want, in best case., about a 15-20* down angle of the belts off your shoulder to the attaching bar.

Dosnt matter where the seat slots are....its where your shoulders are that counts......and it will be coincidental if the slots in the seat are in the right position.

"""""""""" I need to raise the rear of my seat about 2-1/2" to make the opening for my harness at the correct place on the main hoop cross member where the harness will be located"""""""""""""""

I would not raise the seat. You want the driver as low as possible. You want that aluminum seat resting on the floor of the car. After you establish the rake of the seat back with you siting in the car and hands on the wheel and the fore and aft postion of the seat(for pedal reach),then you fab the side brackets from the seat to the floor.

And lastly you fab the back bar so its postioned 2 to 4 inches from the back of the seat where the shoulder belts come thru the seat and at that 15-20* angle of the belts. now then I would suggest that the bar be redone.

"""" also raise the front 2-1/2"? Or, should I add a little more tilt over the 10° built into the seat?""""""""

With the seat on the floor of the car and you in the seat you set the angle of the seat fore and aft. Tilting the back will raise the front of the seat. The front of the seat WITH the seat pading should support your legs with your left foot on the footrest that you will fab, and your right leg supported by the seat and able to use the brale an gas pedals easily. Now if, when you cant the seat back to the angle you need and the kickup is too much for your legs, then you need to use a 20* seat. With me so far??? Driver comfort is PRIMARY here.


""""" 2nd dumb question. I'm thinking about cutting the left 'wing' of the seat )the rib protector I guess its called) back by almost half to make it easier to get in and out of the car?""""""""""

That seat is a circle track seat.....I would have suggested a road race seat that has shoulder wings for more side support. Rib support seats should have driver containment on the right with a driver net and on the left with one of the left side bars..this is best case. you cn trim back the wings. Completely removing you will compromise the seat integrity of back collapse. Depending where your right armpit falls, you might have to trim the top of the right wing so you can shift the trans easily. In any case you want to use a right side net.

When you do your seat mounts you might consider and look at the Kirkey seat brackets. This gives you an idea of a side bracket. The bracket should go the length of the seat on both sides and pick up as much seat area and use 4 to 5 1/4" bolts and large area washers inside the seat on each side. In the front you want to use some more .060" half hard alum and pick up the front seat cross rib to the floor with a 90* flange to the floor. Put your sub belt thru the seat bottom 4" back from your crotch. I'd use at least a 6 point or a 7 point harness which means more trimming of the sides of the seat.

And lastly your seat back should have support below the shoulder belt hole to the rear bar and I would suggest another support form the back of the seat to the ledge on the package shelf in back of your beltline.

 

[Bugeye58]

Excellent points, Jerry. Coincidentally, they describe my installation perfectly! /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
Jeff

 

[tony barnhill]

Thanks, Jerry - I do not want to raise my seat..right now, my belt is at a 15-degree upward slope from my shoulder to the mount point. The instructions that came with my harness said up to 30degrees above my shoulder is okay. Are they wrong?

I took about half that left 'wing' off my seat & can get in & out much easier.

 

[JerryB]

Tony.....

Quite a bit of the safety equipment sold doesn't come with instructions at all. It's almost like it's a secret. The theory is (and the rumors that I have heard ) is that if instructions are too specific that might open the mfgr up to additional liability.

Simpson does have in their racewear catalog "information for restraint systems"....
"Anchor shoulder straps at a point four inches below top of shoulder" and shows a profile drawing at about 20* down.

Another good example of this that I find remiss, is that the seat belts should go from the buckle to the floor anchor in a STRAIGHT LINE in profile view. Many folks have the wrong angle of attack on the seat belts and also some wrong hardware. Simpson does talk about that a bit tho in the same page as the shoulder belts.

Deist Safety also uses a similar profile drawing with similar notes/dimensions. This drawing is possibly from the NHRA rulebook and in fact Simpson says so as a disclaimer.

Also as a reference you can look at the SCCA GCR as there is a profile drawing there with some specs. The call out 90* with the spine which equates to 3-4 " down.

Also I think the HANS website might have some detailed information.

So to answer your ? "they" might be wrong or possibly not accurate?