Topic: Seat back brace question

So, there's a spare seat like this for sale locally that I'm thinking of getting: http://www.momousa.com/racing/seats/sta … w=featured

Problem is, the drivers on my team range from sorta tall to...me. We're probably going to either mount it to the stock 944 sliders or something very similar, so

I think we're stuck using a seat back brace because of the sliders, ugh--unless the stock sliders are magically less than 6" of travel. (I should probably measure that sometime.)

Anyway, is there a seat back brace that works with this seat? Does it matter? I'm guessing we'd have to drill holes in the composite to make a back brace work? Suggestions, plz.

Re: Seat back brace question

Your seat back brace does not have to bold/connect to the seat.  It just needs to act as a positive stop w/in 6'' of the seat back.

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Re: Seat back brace question

We just modified our Sparco Evo Plus to use a seat back brace. We made the whole thing our selves. Yes composite seat - a Sparco Evo Plus (roughly the Evo 2USA or 3)
http://www.sparcousa.com/product/evo-iii

As DC Doug points out, the seat back just has to be 6" from solid (roll bar or roll bar like) part of the roll cage. So you could make some sort of adjustable roll bar piece that is in the area of the seat back. But this is probably more complicated than just adding a seat back brace.

There has been some discussion on seat back braces and the small foot print of the brace on the seat back. Some fear of having the brace foot shear through the composite in an accident and break the spine. So the solution is to use a bigger plate on the seat back, spreading the load and reducing the risk of shearing through. (which by the way, is nearly the same risk as fracturing over the roll bar which is <6" away - Think about that).

What we did.
Got a piece of .120" steel, about 10"x6".  Took the seat and the plate outside to a dirt area with a sledge hammer and John S. pounded on the plate in the dirt. The dirt acted like a shot bag, allowing the blows to bend the plate, but not very much allowing for better control of shape. John got to within about 1/8" overall shape to the back of the seat, shoulder area, just below the seat belt cutouts.
We had some 1" square, 0.125" thick wall Aluminum tubing which we drilled a hole in one end, and then rounded the end to allow for pivoting. Then we made 4-  1" steel angle pieces 2 as pivots, and 2 as the roll bar pin pieces (pre-drilled for cross pin/bolt). We welded the pivot pieces to the plate. Lined up the plate and AL tubing in the car, and marked the seat. We undid the seat cover and then match drilled plate/seat with 8 small pilot holes. We were using some 8-32 Stainless Steel CSK head screws I had around for another project.  The countersunk screw heads would be nearly flush with the inside seat surface and so not pose any risk to the drivers back.
We tapped the plate for the 8-32 screws, drilled and countersunk the seat for the screws and installed the back plate. We added nylock nuts for extra locking on the 8 screws. Put the seat in the car, lined up the Aluminum tube with the roll bar and clamped on the two 1" angle pieces. Those got welded in on the underside of the harness bar, and then we marked and drilled a couple locations of the seat to fit our various drivers.

A note on screw size and composite seats. Composites (fiberglass and carbon fiber) are strong and tough in continuous form, but when you start putting in screws, the local stress/strain can easily exceed the strength of the material. More smaller fasteners are better, the load on each fastener is small so its less likely to rip through. More of a small loaded fastener equals the same strength as one or two bigger fasteners. We used a 3/8 bolt for the cross pins of the brace. So that is 0.375" DIA, or 0.11044 sq inches of steel. A #8 screw is 0.164" DIA, or 0.0211 sq inches. So dividing 0.11044/0.0211 = 5.2 . Meaning 5.2 of the #8 fasteners is equivalent to 1-3/8" bolt for strength. Now I did a real rough job of estimating, and Stainless Steel is not as strong as regular steel, or high strength bolts (grade 8), so put in a couple more for safety and you should be OK.

The other thing to remember is the seat back brace really only takes a backward load. Meaning the driver gets slammed back into the seat, if the car is hit from behind. If the car impacts a wall, and the driver is thrown forward, the seat belts take the load. So the seat back brace just needs to support the nearly direct load from the seat to the roll bar, and the shearing forces of any angled bracing that are going to try and peal the brace off the seat back (because the brace will not be perpendicular to the reclined seat back). And the wide plate and brace tube are really doing most of that work.

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?Everyone who has ever built anywhere a 'new heaven' first found the power thereto in his own hell- Frederick Nietzsche

Re: Seat back brace question

mackwagon's solution sounds a bit complicated, with all that hand-forming and such.

We just took some angle iron, welded it into a square, welded on a couple muffler clamps so it'd attach to our cage, and we were off to the races.  When our short driver sat in the seat, we'd swivel the bracket into place and tighten the clamps.  When our tall driver sat in the seat, we'd swivel the bracket out of the way.

Re: Seat back brace question

papal_smear wrote:

We just took some angle iron, welded it into a square, welded on a couple muffler clamps so it'd attach to our cage, and we were off to the races.  When our short driver sat in the seat, we'd swivel the bracket into place and tighten the clamps.  When our tall driver sat in the seat, we'd swivel the bracket out of the way.

Muffler clamps are not Grade 8 hardware. Grade 8 hardware on Seat belt and seat attachments. So your seat back brace isn't really a seat back brace, its a hack job that doesn't meet the rules.
Lemony fixes are awesome, just read the rules and understand where you need to really have a good design and use the right hardware

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?Everyone who has ever built anywhere a 'new heaven' first found the power thereto in his own hell- Frederick Nietzsche

Re: Seat back brace question

Is there a LeMons-legal way to have a brace that doesn't bolt into the seat, then? Are there already made versions that operate like that?

After our last seat got twisted up from a side impact (whole cage got pushed over and took the seat back with it), I'm a little meh about bolting into the back of it again. I'm not sure if it's better to have it unbolted or not, though.

Re: Seat back brace question

ninjacoco wrote:

Is there a LeMons-legal way to have a brace that doesn't bolt into the seat, then?

Rule 3.2.2: Seats without Seatback Braces. If a seatback brace is not used, a strong, seat-width element such as a shoulder-harness bar must be located within six inches of the seatback to prevent the seat from failing rearward.

We use a seat-width section of rollbar tubing that is welded at the end of a projection from our shoulder-harness bar.  It isn't adjustable but we can adjust the seat itself far enough to accommodate all of our drivers while still remaining within six inches of it.

http://farm8.staticflickr.com/7131/7132588725_bc74b4be53.jpg

1982 MG Metro 1300: IOE 2015 Pacific Northworst GP, Longest Distance 2010 Cd'L Box Wine Country Classic
1980 KV Mini 1: Worst of Show and Fright Pig Supremo 2009 Concours d'Lemons
1978 H Special: Second-Round Elimination 2010 Lemons Pinewood Derby at Sears Pointless
1967 SAAB 96: IOE 2012 Pacific Northworst GP

8 (edited by Brett85p 2013-07-16 06:08 PM)

Re: Seat back brace question

http://i48.tinypic.com/2w20s9j.jpg

This is legal, pipe inside pipe with holes drilled in the inner at 1 inch intervals and a bin to hold in place. We move it back/forward depending on the seat position. I know the rule is 6 inches but that's more than I want my neck stretching!
Picture shows it a lot further back than we would race with.

Apocalyptic Racing - Occupy Pit Lane racing
Racing the "Toylet" Toyota Celica powered by Chevrolet Ecotec.
16x Loser with the Celica. 5 times loser in other fine machines

Re: Seat back brace question

NICE. We'll have to look up how to make something like that, then. I have a feeling we'd need to have it adjustable, so I like that bottom suggestion.

Re: Seat back brace question

Better picture
http://i39.tinypic.com/140c16o.jpg
before additional bracing.

Apocalyptic Racing - Occupy Pit Lane racing
Racing the "Toylet" Toyota Celica powered by Chevrolet Ecotec.
16x Loser with the Celica. 5 times loser in other fine machines

Re: Seat back brace question

http://i944.photobucket.com/albums/ad286/trekkor/car%20photo%20dump/P1060478.jpg

http://i944.photobucket.com/albums/ad286/trekkor/car%20photo%20dump/P1060479.jpg

Tallest driver is tight against the brace, shorter drivers are a few inches forward.


KT

TH 2009- 40th ~ SP 2010- 13th Class Bad win!! TH 2010- 17th ~TH 2010- 16th  SP 2011- 20th ~ RF 2011- 13th Least Horrible Yank Tank ~ TH 2011- 79th
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Re: Seat back brace question

mharrell wrote:
ninjacoco wrote:

Is there a LeMons-legal way to have a brace that doesn't bolt into the seat, then?

Rule 3.2.2: Seats without Seatback Braces. If a seatback brace is not used, a strong, seat-width element such as a shoulder-harness bar must be located within six inches of the seatback to prevent the seat from failing rearward.

We use a seat-width section of rollbar tubing that is welded at the end of a projection from our shoulder-harness bar.  It isn't adjustable but we can adjust the seat itself far enough to accommodate all of our drivers while still remaining within six inches of it.

http://farm8.staticflickr.com/7131/7132588725_bc74b4be53.jpg


Are you happy with this solution? I'm going to need to do something similar and this came to mind.. Are the judges happy with this when you go through tech?  I am thinking to put to supports off the cage evenly spaced instead of a single piece.. This will balance the load, I think and also act as stoppers to keep the belts within the "even or angled in" requirements.

BlackMaven Motorsports - a tiny, less creative, division of Three Pedal Mafia   Supporting the United Leukodystrophy Foundation - www.ulf.org
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Re: Seat back brace question

WarpdSpazm wrote:

Are you happy with this solution? I'm going to need to do something similar and this came to mind..

I'm happy with it.  Our other drivers are happy with it.  Then again, one of our other drivers is Pete Peterson and I believe he spends most of his time in the car giddy and giggling anyway, so I don't know how high a bar (so to speak) that sets.

WarpdSpazm wrote:

Are the judges happy with this when you go through tech?  I am thinking to put to supports off the cage evenly spaced instead of a single piece.. This will balance the load, I think and also act as stoppers to keep the belts within the "even or angled in" requirements.

Nobody at tech, including TEO, has ever said anything bad about it.  TEO and others have mentioned that the cage is by far the nicest part of our car.  I agree.

I like the idea of two supports, now that you mention it.  We're using some roll cage padding (not shown in this photo) to hold our belts properly inward.

1982 MG Metro 1300: IOE 2015 Pacific Northworst GP, Longest Distance 2010 Cd'L Box Wine Country Classic
1980 KV Mini 1: Worst of Show and Fright Pig Supremo 2009 Concours d'Lemons
1978 H Special: Second-Round Elimination 2010 Lemons Pinewood Derby at Sears Pointless
1967 SAAB 96: IOE 2012 Pacific Northworst GP

Re: Seat back brace question

We have only about 4" to close for our smallest driver. I'm considering a similar solution, but instead of mharrel's "T" design pictured simply having another crossmember, installed below the one the belts are attached to, curving out to meet the width of the seat back. Thoughts?

Re: Seat back brace question

Went and had the bar installed by a local weld shop that spent the last 25 years building and racing modifieds.

https://scontent-b-iad.xx.fbcdn.net/hphotos-frc3/t1.0-9/1981867_512747008830383_37477501416511768_n.jpg

https://scontent-b-iad.xx.fbcdn.net/hphotos-frc3/t1.0-9/10168174_512747035497047_4174967232474895046_n.jpg

Our tallest driver is touching the bar and our shortest is about 4.75" away.

BlackMaven Motorsports - a tiny, less creative, division of Three Pedal Mafia   Supporting the United Leukodystrophy Foundation - www.ulf.org
'68 Ford Cortina - 2 Races: 1 Motor dead, 1 wheel driven clean off the car (axle included)
'86 Toyota Cressida - B Class win at Thompson
BlackmavenMotorsports on Facebook

Re: Seat back brace question

Jim Whitley at Rollcagecomponents.com designed this adjustable seat back brace setup for us. It clamps to the support bar behind the seat, and then has two sizes of tubing that slides between each other, and uses clamps to hold everything in place. So you just loosen the clamp bolts when you slide the seat, then tighten them back up. Worked great for us.

Here it is installed in our car:
https://www.facebook.com/pages/Roll-Cag … mp;theater

Here it is on his website for about $60:
http://www.rollcagecomponents.com/adjus … mount-kit/

Collateral Damage Racing
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