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Author Topic: Seat brace with composite seat?
Sean Allen Verified Driver Made Donation to Website
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Anyone tried this before? I have a Sparco Evo seat in my car, and it moves and flexes quite a bit. This may be how the seat is designed, but I'm not sure. Any ideas?

Kim Ouye Verified Driver Made Donation to Website
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Well...I asked a Recaro engineer this question and his answer was the seat was certified w/o a brace. Read into that what you will, but I took it that it would go against the seat design if you add a brace.

I'd imagine that the Sparco seat is FIA certified that way.

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Jim Boemler Verified Driver
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Your helmet is certified without a HANS device, too -- what does that mean really?

jim

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A HANS doesn't affect how a helmet works, the seat brace affects how a seat works.

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Kim

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JB - I usually agree with your posts, but I think you're off on this one. [Frown] A helmet's certification means it has a damn good chance of protecting the contents from impacts to the helmet. Adding a HANS minimizes other risks without compromising the helmet's ability to withstand an impact.

The composite seats that are certified without a brace MAY be compromised by installation of a brace since they are ostensibly designed to protect/restrain the driver as a stand-alone system.

If you replaced all that foam inside the helmet with hard plastic, your head would move around a whole lot less. Let's do that too!
[Razz]

Steve D.

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The point is merely that certification under certain circumstances doesn't mean you can't get even better performance under different circumstances. Whether it's an improvement or not for this seat and this brace, I couldn't say; but I think it's a mistake to say that because it passed a test once, it can never be improved.

jim

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Sean Allen Verified Driver Made Donation to Website
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Yeah, the Sparco evo is FIA rated as is, I guess I will just leave it. I was at the track a few days ago, and on hard switch backs, there was a clunking-ish noise and some flex. I have a custom seat mount that adds to the flex, but it turns out the bolts were a little loose so that may be contributing to the problem. I guess we will see how the next event goes.

Kim Ouye Verified Driver Made Donation to Website
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Jim - What I got from the Recaro engineer was basically that it would not improve the seat performance. He would not specifically answer my question thouhg, probably for liability quesion, but he did imply that the seat is supposed to give for shock absorption. Making it not flex seems like it goes against the design and possibly cause more problems than it solves.

Sean - My Recaro seat flexes quite a bit also, but I assume it is meant to do that to absorb some of the energy. I too have a custom seat mount and probably need to look at it to see if it contributes to the flex.

--------------------
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My Sparco Rev would come loose and "clunk". I took out the bolts and put loctite on. Then tightened them up real good and havn't had a problem since. It is part of the design to get a little flex in these seats.

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Sean Allen Verified Driver Made Donation to Website
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Alright, so thats what it was then. The bolts were somewhat loose through the floor and maybe the clunk was them moving against the floor pan. Ill try lock washers and loctite and hope they stay tight.

jwarren Verified Driver
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there is actually a reason why these seats flex and it is a very BAD idea to brace them.

so here is how it works. imagin you hit someone from behind... your seatbelts stop you from going anywhere and the seat essentially does nothing.
now lets imagine that someone hits YOU from behind. the back of the composite seat will flex backwards. As this happens, the sides will actually "squeeze" you in your seat. They'll pinch inward and basically hug you in place. This is what these seats are made to do.

If a seat brace is installed, the seat won't flex, and the sides won't hold you in. this comprimises the design of the seat and its function. This is also why aluminum seats have big wings.

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What the heck are you talking about, JW?

What about guys that use HANS? Let's say in the situation of a rear impact, your seat flexes to the rear. Now your shoulder belts are LOOSE compared to static position. Should we worry about the belts becoming slack in a rear impact even without a HANS?

SCCA Pro mandated seat back braces on all seats at the start of the 2006 season, I'm guessing for this very reason.

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maybe my side of the argument was wrong but i guess what i was trying to get at was this - i don't really think composite seats were made for seat back braces and by installing one it could be equally if not more dangerous than having your belts come loose.

i guess what it comes down to is this - are you willing to have your belts become loose or are you willing to comprimise the strength of your composite seat by installing a seat back brace.

maybe aluminum is the way to go?

interesting read:

http://www.ioportracing.com/faq/seatbackbraces.htm

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I totally agree that composite seats are designed to flex. I just think that it is an interesting argument about the belts slacking, especially when it comes to HANS usage.

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Carlo Sparacio
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trust me i wouldn't get in a car without my hans, and i agree that there needs to be a solution for this problem, but i don't think that seat back braces are necessarily the solution.

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Jim Boemler Verified Driver
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What "problem" are you trying to solve, Andrew?

jim

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I seem to recall around 1998 a driver in PCA Club Racing spun on a wet track and backed his car into concrete wall at high speed. COD was a broken neck caused by the seat mounts shearing and allowing his neck to be broken by the harness bar on his roll cage.

I have no idea if he was in an FIA certified seat or not. The point being that in a rear collision a bunch of relatively flimsy stuff is all that keeps you away from the rear windshield.

A properly installed side net that wraps around the back of the seat probably serves as somewhat of a back brace for the seat.

The fact that for most people the installed seat is only a few inches from the rear bulkhead means that in a Miata we may be relatively well restrained in the rearward direction if the seat mounts depart.

Jim Boemler Verified Driver
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Seems like a good argument for an aluminum seat (and brace) to me.

jim

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Dusty Bottoms Verified Driver Made Donation to Website
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Multiple braces...there's a picture somewhere from some manufacturer where they show braces to the cage at 3 points: head, center (where most people have one), and lower section toward the edges.

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quote:
Originally posted by Jim Boemler:
Seems like a good argument for an aluminum seat (and brace) to me.

jim

Please explain.

Ed

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Rigidly attaching the seat to the cage intuitively seems like a good idea. How can more support direct to the rollcage be a bad thing? The above discussed rear impact scenarios assume the seat flexes and the belts go slack. Wouldn't the inverse be true with a brace, assuming the seat doesn't flex, the belts don't go slack and they continue to hold you safely in position. I'm just asking, the seat (fiberglass MOMO FIA certified)is about to come out of may car anyway for some interior paint touch up, so now is the time to decide this issue.

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My personal feeling is that in our cars with the tight cockpit any flex is bad. Maybe in a bigger car the composite seats are great. For my car, if I had a composite seat, any flex would result in impacting the harness bar and/or the rear firewall.

As far as belts going slack...who cares in a rear impact? Belts hold you in a forward impact, the seat in a rear-end collision.

I wish I could find that picture of the recommended bracing.

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Playing devils advocate for a moment....

Would a rigid seat be similar to a car without a crush zone, transferring the entire energy of impact to the driver?

--------------------
Kim

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Ah, I love the internet! Be careful, guys, when getting safety advice from forums and merchants. Opinions and conjecture often resemble "science" when stated with enough confidence and conviction.

I recommend doing what Kim did - ask the manufacturer of YOUR seat what the proper and acceptable mounting methods are. Testing is the only way to ascertain what works and what doesn't.

My perception, having done a little research on seat and harness safety and then looking at club race cars, is that the mounting of the seat, harness, interior net and seat brace is woefully inadequate on many amateur cars. Whatever combination you choose, please make sure that you very closely follow the manufaturer's installation instructions!

For what it is worth, when I bought my car, the seat brace wasn't working (collar was impossible to tighten enough - crappy design), the sub strap was mounted incorrectly and the seat interfered with the shoulder straps. All very dangerous, yet all passed NASA and SCCA tech.

This is just my OPINION, as I'm not a safety expert...

Dean

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I agree with your statement Kim. The idea behind the Fiberglass or Carbon/Kevlar seat is for it to flex in an impact and absorb energy. If you were supposed to put bracing on these seats, the instructions would tell you so.

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quote:
Originally posted by Kim Ouye:
Playing devils advocate for a moment....

Would a rigid seat be similar to a car without a crush zone, transferring the entire energy of impact to the driver?

Check out an AL seat after an impact, it will be obvious that they flex/bend quite a bit.

They just dont throw you back like a composite seat does.

An AL seat is a one shot deal. You crash - it bends - you toss it.

-Kyle

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quote:
Originally posted by Antonio Garza:

As far as belts going slack...who cares in a rear impact? Belts hold you in a forward impact, the seat in a rear-end collision.

Well, a rear impact could be followed by a frontal impact. And with a HANS, could the HANS slip out from under the belts in the rear/quarter (slack) impact and then be useless in subsequent impacts whether side or frontal?

I am only throwing this out as a "what if." I have no science behind it or am I trying to state anything as a fact. Just thinking out loud. I don't engineer safety systems and I don't have a test sled.

What brought my line of thinking on is when SCCA Pro mandated all seats, including composite FIA seats, to have a seat back brace. All SCCA Pro drivers must also use a HANS, so I wonder if the two are connected.

--------------------
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Hey Carlo,

Just want to be clear that my rant wasn't directed at you, but rather at the link in the post further up that advocated back braces for any and every seat without offering any sort testing or specific installation instructions...

Cheers,

Dean

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Kyle - Good point. But then again, does it make sense to make an aluminum seat more rigid with a seat back brace???

--------------------
Kim

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Dean,

No sweat, I did not take it as that. Just being clear from my point of view.

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Carlo Sparacio
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Kim, I want the crush zone in the car not in the seat....as Kyle posted, I'd rather have a seat deform than flex back.

I am not an expert on the human body in impacts but I am familiar with electronic product shock/vibration testing. The difference between survival or no in a component (60-200G) is not the total amount of energy but how fast it's imparted. So a sharp spike kills a component but the same energy stretched out a tiny bit would make a big difference in survival. I'm guessing it's the same with our cars and bodies. What are average speed crashes in real life and in racing and how do people walk away from a 35mph frontal crash in a car with a 3 point belt? Before anyone starts telling me how fast we are racing, how fast was Dale Earnhardt's crash speed (subtract the tangential component) and do you think he would have survived that impact in a street car instead of a tube frame car?

For you guys with the composite seats, do the instructions tell you how much minimum clear space you need between the seat and rigid surfaces? Just curious.

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Here's the diagram for how seats are tested for FIA certification. You can see that there has to be 150mm minimum between the back of the seat's headrest and the cage, and 200mm min from the point where the belts go through the seat.

 -

After preaching to everyone to follow manufacturer's recommendations, I couldn't find a single installation guide from a competition seat manufacturer... oy!

Dean

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Well since 150mm of clearance for a 6ft 220# driver would mean not being able to turn the steering wheel, the full "flex" space tested by FIA isn't really an option in a miata.

Dean, dfastbear, where did you find that diagram, does FIA have a website in english?

I'd like to review some of the information if it is readily available.

I'm still leaning toward leaving the brace installed by the previous owner of the car. I think I agree with Antonio "wheel" Garza, the place for crush zones is much further away from the driver than the seat.

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Ignore the previous question about FIA, I found it once I beat google into submission

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It would be interesting to see rear impact crash sled videos to see how much an FIA approved composite seat flexes. Does it go back 149mm or some amount much less than that?

This seems like such a basic decision to make when mounting a seat that seat manufacturers would some how address it with guidelines.

I wish there was a definitive seat mounting document similar to the one Schroth put out on harness mounting.

Cheers,

Dean

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I've seen one before...but I can't find it! They recommended the seat attached to the cage with rails, etc. It was pretty fancy. Basically attaching to the floorboard was not good according to what I remember seeing.

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This is a very interesting discussion and I must admit I now realise I have a bit more research to do with my manufacturer's products in regards to whether there is a specified distance required between the shell and rigid areas. Miatas are a tight fit as we experienced on Andrew's car.

I can say, and definatly agree, that it is imperitive to double check on bracing with the manufacturer. My seats do have some that come ready for such mounting at the shoulder area. I also have a retro fit detailed for some specific older models. This came up because of the MX5 cup and also at Carlo's request when we were looking at this last year.

While most seats are FIA certified, w/o the back brace, you need to look at your class rules and it seems the brace is a direction we're going, probably for good reason. Carlo's speculation may be one possibility.

Realise in Rally cars that there is in car film showing the seats giving up some side flex in monster g load crashes. This is in a tumble. In an aluminum seat a driver's helmet bounced and smacked the Halo wing to the side. Great, it gave on the first bounce... where's it gonna be for the possible 2-4 more rolls and impact as the car finishes tumbling? I am not sure I'd want a "Mechanical fuse" one shot safety device. I'd prefer something to stay intact until I am done and get out of the car and empty my shorts! [Eek!]

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Antonio,

The seats used in NASCAR (which are aluminum) are attached to the cage, via a tubular frame and it not attached to the floor of the car (of course, the cars are tube frame already...but).

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Racetech is one seat manufacturer that produces a composite seat that requires a back brace. I don't know if there are others. Unlike most composite seats the RT is very stiff with almost no flex. It is unbelievable how secure you feel in a RT when compared to another composite seat. I can't comment on the aluminum seats having never driven with one. If you saw the video of JD's crash at Mid Ohio you'd understand what I mean. Horrific crash with several big impacts and his head and upper body are almost stationary in the seat capsule. Barely any body or seat movement at all. On the other hand I watched a video of a Porsche GT3 with a composite seat of some type and I couldn't believe how much the seat flexed back and forth under normal racing conditions, never mind how much it would flex in a crash.

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Originally I was avoiding mention of which brand of seat I sell, in deferance to Saferacer.com, as I appreciate their sponsoship of this forum. I was definatly interested in this discussion, for obvious reasons. Then I finally went to their website, (I'm old and slow), [blush] and I see they are wisely offering Racetech as one of their brands so there was no conflict, or advertising issues. Wanted to try and follow Mike's posting instructions and yet be a part of this worthwhile discussion. ok now that's of my chest... I am awaiting some more feedback from Brian at Racetech and will include it when it comes through and if it is relevant. [Cool]

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Ok folks here ya go... I learned alot.....

Neil, Here’s a response back from David about the specmiata.com forum
--------------------------------------------------------------------------------

From: David Black
Sent: Friday, November 17, 2006 3:00 PM
To: 'brian'
Subject: Back Braces etc



Well I guess I will need to write a book at some stage.

I believe there are some misconceptions here.


There are 4 main parts of a human to protect and keep these parts in the same relationship with each other. Head - Shoulder - Pelvis - Thigh - It is believed that if this is achieved then the Human body can survive impacts beyond 100G without serious injury

The foremost safety people in USA say that in a wreck you should stop the human body as close to the Chassis Deceleration as possible.

Flex in a seat or stretch in a belt is not absorbing energy - it is storing it for later dissipation. The energy absorption should be done with specially designed energy foam as used in the head , shoulder and back areas of Racetech serious race seats utilising the square shoulder and back mounting.

One issue with back bracing a seat which is not specifically designed for that is - the lateral shoulder support of the seat is not adequate to support the shoulder of the occupant. hence the seat stays rigid and the driver slides out sideways.

The positive of a back brace on any seat in a rear impact is that it takes most of the load - without a back brace the loads on the side mounting bolts, brackets and bolts to the floor are enormous and could fail in a major impact if not well designed. It also should be noted that rear impacts generally cause less injury because of crush zones in the car etc.

Many models of Racetech seats are designed and tested with back braces attached. Racetech is still the only FIA seat maker who homologates seats with back mounting. Because Racetech seats have good square shoulder supports they therefore take more load in a lateral impact than a traditional open shouldered seat.

We have measured lateral impacts of 81G where the driver has walked away unhurt sitting in a Racetech RT4009HRV (Viper Seat).

I trust this answers some of the questions.

Regards
David Black

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"I am master of my unspoken words and slave to those that should have remained unsaid." Abe Lincoln

Sean Allen Verified Driver Made Donation to Website
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Thanks for all the responses, I;m not going to worry much about it right now with my Sparco seat, I think I will just start saving for a Racetech with HR.

Dusty Bottoms Verified Driver Made Donation to Website
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I still haven't seen anything about minimum clearances for a composite seat...the prices on some of these are coming down but I'd like to see info on what kind of clearance is needed. My seat has the shoulder wing essentially touching the main hoop, and it's very close to the cross bar.

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"Your victory is tainted! Asterisk! Asterisk!!!"--Lisa Simpson

mx5er
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Has anyone used a set of OEM sliders? I have an extra set.

SAE113 Verified Driver
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holy three year old thread batman

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Steven Elicati
'92 Protege ITA#01
'94 Miata ITA#99

tony senese Verified Driver
Phew, that was close!

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quote:
Originally posted by SAE113:
holy three year old thread batman

lol!!!

--------------------
Tony Senese
SM#99
2008 NASA-NE SM Champion
NASA-NE SM Director
2008 PRO-IT SM 3rd place
http://www.nosenseyet.com/coppermine

seege Verified Driver Made Donation to Website
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This resurrection is timely. I have a Racetech HR 4009 that's 5 years old and NASA is now requiring a brace be installed. Anyone else done this? Tips?

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-CJ Johnson

Keith in WA Verified Driver Made Donation to Website
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The Ractech is fiberglass so it's a bit easier to work with. Use sharp tools. Protect yourself from the fiberglass dust. Reinforce the holes. Try to get the contact patch to the seat as flush to the surface as possible to best distribute the load. Also hope you never get into a bad crash where the seat should really flex as designed. They're not meant to have a back brace.

If it was carbon fiber I'd say don't drill through it if you don't already have significant enough experience working with carbon fiber to understand why I say don't drill.

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Keith Novak
(Will work for tires)

SAE113 Verified Driver
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do the rules state that the seat has to be attached to the seat brace or just that you have to "use" a seat brace. because if it doesn't state attached I wouldn't. Like keith stated those seats are not designed to be attached in the back. stupid rule anyway,why would the seat be any different 5 years old or new.

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Steven Elicati
'92 Protege ITA#01
'94 Miata ITA#99

seege Verified Driver Made Donation to Website
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Yes it needs to be attached to the seat. I would rather buy a pre-fabbed weld-in brace if there is one out there. Also, I don't want the brace to have rods pointed at the driver for obvious reasons. Sorry I haven't had time to do any homework on this yet...just hoping someone else has done this as these seats have been popular a few years now.

-CJ

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-CJ Johnson

 
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