racing geek

iTrader: (5)

Yes you read the title correctly, I'm going to build a harness bar. I don't want to install an actual roll bar or roll cage because it will ruin my interior which is in really nice condition (ask anyone at TGF this year). The other thing is no one makes a harness bar for third gen F-bodies.

I'm tired dealing with the stock seat belt, and I'm tired of bracing myself against my center cousel and floor while I autocross. I upgraded to the Corbeau Forza seats and I no longer have to use the center counsel for support (to prevent lateral movement in the seat), but I always have to use my left foot to try and hold my torso back in the seat when I slam on the brakes instead of using it to brake. I have a set of 5-pt harnesses, but the shoulder straps are to short to go all the way back to the rear seat belt mounts.

My plan was to use a piece of pipe I have at home (1.5"odx3/16") and have two bends put in it to make it resemble the top portion of the main hoop of a roll bar/cage. I would then have this angled back to where the back of the rear seat pivots at. The pipe would be welded to a bracket (3/16") that would bolt to the stock bracket. I would also have extra braces going from the main pipe to where the seat belt mounts below the center counsel. I did some basic modeling in Inventor and it doesn't look like there will be much flex (less then 1/4") even with 35,000 pounds of force acting on the main bar. According to a website I found, a 200lb person exerts 15,000 pounds of force during a 70G crash. This is why I doubled the number to 30,000 and added another 5,000 pounds as a safety factor.

If I can use a harness, I wouldn't be surprised if I could take at least a second off my times. Next time I autocross (June 21), I'll make a video of me trying to brace myself so you can all see how bad it is. If I wasn't so tall, and my head wouldn't have been pushing against the A-pillar plastic, my whole head probably would have been out of the car during the long sweeping turn at the last event (Sunday). I'm getting tired of my racing being a full body workout!

Any ideas for mounting locations, material thickness, or other stuff is greatly appreciated.
Mike

PS - How much do shops typically charge per bend, or would it be cheaper for me to just find someone that cut out a roll cage and take their main hoop?

Stephen

iTrader: (12)

I've seen what your basically talking about making, commercially made for 4th gens, that mount to the rear seat shoulder strap mounts (of the late 3rd gens), reaches forward & provides a bar to mount the front seat 5-pt shoulder straps too.

racing geek

iTrader: (5)

Yeah, that's all I can find as far as harness bars for F-bodies goes. I would mount mine up there but my car is an 87, meaning it is too old to have the rear shoulder straps, and therefor, that mount doesn't exist in my car.

FueledSoul

iTrader: (18)

I'v been thinking about this for a long time. i dont want to put a roll cage in eiether. i have a 8 point laying around in my garage even thoght 4 point with the main hoop and the back peaces. but what a waste just to have a harness. . .

racing geek

iTrader: (5)

I did some math based on the numbers in my first post, and apparently those forces are experienced during a 168 mph crash. This is well over three times the speed I would get to while autocrossing. Even if I take my car on a road course, this harness bar would still be more then strong enough.

This is where I found the numbers that are in my first post and what I used to get the numbers in this post. (middle of the second paragraph)
http://www.circletrack.com/safety/ct...unt/index.html

Please correct me if any of this math seems questionable. I am confident in the math I have done but it is always good to have others double check everything.

I was looking closer at the bar I have and there are a few 1/4" holes drilled in it. Do you think this would compromise the strength any? I'm not worried about passing tech at the drag strip because my little 305 is barely enough to get me below 15 seconds. I couldn't find any rules or requirements for harness bars in the SCCA Solo rule book so it seems as though I just have to build it up to my standards.

Mike

punkdude908

sounds cool...can't wait to see how it turns out.

1Aauto

X2. Like to see custom work.

omnipotentgoku

iTrader: (1)

Have you considered making this a part of the infamous "rear strut tower brace" (knowing that it doesn't exist, its just what i've seen it called before). If you could add to the rigidity of the rear while having a seatbelt harness... well lets just say its good times for all!

Stephen

iTrader: (12)

Year One used to sell one for 4th gens....Part # LG92B, but it isn't shown in their current online catalog.

Dunno if it is discontinued, or I just didn't find it, despite a seach of their catalog.

racing geek

iTrader: (5)

I was looking into this for a while too. I think it was discussed about this time last year, and the conclusion was that there isn't much need for a rear shock tower brace. The way the metal is shaped back there (all the angles/curves strengthen it), it was deemed strong enough for pretty much any thing the cars would be used for. However, if you wanted to turn a rear shock tower brace into a harness bar, it would be recommended that you make plates similar to what is used for welding in a roll bar/cage in order to strengthen the mounting mounts. All the time it would take to make the reinforcing plates match all those bends/curves would probably be better spent trying to mount it in a different location. Yes that metal is strong... but it probably is not strong enough for the forces I stated above. Also, the shoulder straps on my 5-pt harnesses aren't long enough to reach all the way back to the rear shock towers so I would still end up having to get a tube bent.

See, still 4th gens... Either all the aftermarket companies hate our cars, or they realize that most owners of 3rd gen F-bodies are too cheap to cough up the money and buy their products. Sigh... Though the current economy doesn't really help matters. Heck, I'm still in high school and even I'm feeling the effects of this economic downfall. My hours at one of my jobs went from 22-25 hours a week down to 10-12 hours a week. The only reason I probably still have that job is because all the managers like me.

Thanks for looking Stephen.

-----------------------------------

I haven't had much time to do any work on this lately because of a big Psychology project. I'm hoping to start doing some more modeling and testing on the computer later this week, and I probably won't be able to get to actually building it for about a month. I have other more urgent issues with my car, such as getting rid of the oversteer (already dropped from a 24 to a 22) and getting new tires since mine are almost bald.

Sorry for the slow progress and lack of updates.
Mike

GMan 3MT

iTrader: (4)

Not to dissuade you from your project, but have you tried this in the meantime?

The other thing I have heard of is the cg-lock that somehow locks the lap portion of your stock seatbelt. Seems like a popular choice.

I don't have any experience with either. I did, however, drive a friends F-stock third gen who had just a lap belt portion of a harness installed along with the factory 3 point. Even with stock seats, it wasn't too bad.

[sarcasm on]
And if you still complain that's not good enough, consider how lucky you are... try autocross with someone who has a bench vinyl seat!
My experience was riding shotgun in a 60's GTO IIRC
[sarcasm off]

racing geek

iTrader: (5)

The CG-lock would be something to consider, however, I don't think it would work for our cars unless you do the 4th gen front seat belt conversion. This is because the lower retractor for the waist portion of the seat belt is still going to allow the slack.

The seat reclining would also be a great idea, but it isn't possible for me. I can't recline my seat because it is a fixed back racing bucket seat (Corbeau Forza). You can see a pic in my VBgarage. So, instead of tilting the seat, I could slide it back a little, lock the belt, then slide it forward. However, that still wont work because my seat is already slid back as far as it will go. I can't really have the seat any closer or my knees will get in the way of the steering wheel. Then I have to leave the steering wheel up which feels odd, and looks funny seeing it so much higher then the dash pad. Being 6'3" sucks. When I installed my Corbeau seats, I already mounted the seats as low as they could possible go without actually bolting them directly to the floor. I posted how my seats mount in a thread in the interior board. I'll make a link later.

With the Corbeau seats, my butt doesn't really go anywhere due to the high sides of the seats. My problem is when I slam on the brakes and my torso goes flying forward, or when I'm in a turn and my torso slides into the door or my head is above the passenger seat. Ok, its not that bad but still...

My worst experience was in a new Dodge Challenger with the leather seats. It wasn't terrible considering the car can't really turn too well, but when the tires did dig in, I basically body slammed the door. I told the owner he should go back to autocrossing his Miata. He agreed, but said he wanted to see how it would do.

Mike

racing geek

iTrader: (5)

I made some videos of me inside the car during some runs on Sunday. However, I had surgery on Monday and finally got around to putting the videos on my computer this morning. I'm hoping to get them edited and on uTube by Monday. I think I found someone with a mandrel tube bender that would be willing to bend me a tube for cheap. Apparently the guy used to do the chasis work for one of my dads friends late model dirt oval race car things. Who knows though, maybe it will be better if I just weld 3 bars together instead of getting one tube bent. It sure would be cheaper that way.

Another thing... I don't have access to that stress analysis program anymore because school ended. Now I can only do the math and hope it turns out as planned.

Mike

bluethunder28

iTrader: (1)

I had a friend who put in eye bolts right behind the rear seats so all he had to do was clip them in when they ran.

I have the Schroth belts in mine.

Stephen

iTrader: (12)

I hope he either A-Never NEEDS the seatbelts (like in a crash or B=Has some good structural reinforcement back there, or the eye bolts are gonna rip right through when he needs them most.

bluethunder28

iTrader: (1)

You buy the eye bolt kit when you buy your belts. It's the same kit they use in race cars.

Stephen

iTrader: (12)

You missed my point.....

IF the eye bolts through sheet metal only, they can rip through. You need a thick steel plate to mount them through, not just the thin sheet metal.

sam24th

iTrader: (1)

You would have to weld in a thicker sheet of metal to the sheetmetal to disperse the energy. Also mounting seatbelts like this can cause injury to your shoulders in a crash. Aftermarket seatbelts are ideally mounted at almost shoulder height to prevent your shoulders from being injured. Thats also a reason 5pt harnesses are illegal for street use.

Stephen

iTrader: (12)

The main reason is because the manufacturers haven't paid the $$$$ to have them pass crash test standards. I guess the $$$$$$ cars that come from the factory that way (european supercars) were built that way, so they are OK.

The other reason, is because the way a 3-pt is designed, it allows the body some angular deflection, down & away from the roof in the case of a rollover. A 5-pt keeps you straight up in your seat & your head is crushed in a rollover.

I say.....If your car rolls, your pretty much screwed anyways, so let's just get a painful recovery over & done with! (not politically correct to say i know, but i'm speaking from personal experience on this one).

Pretty sure I see Cobra kit cars with them though, so I'm not too sure how they pass legally/If they are OK for those cars/or the inspectors look the other way.

bluethunder28

iTrader: (1)

My point is for a quick and easy way to mount the harness for an autox, behind the back seat (upper trunk) is an easy fix without messing up the interior.

//<86TA>\\

iTrader: (14)

that may be true, but i will have to agree with Stephen. If your friend did actually cash the car the bolt would most likely fail and he could be killed. Is that worth the convenience of a quick mounting location?

However you could use that area as a mount, but you should still reinforce the mounting area so that it is as strong as it should be. You probably would be able to install the plate without dropping the fuel tank, not a big deal for a little added saftey.

leonpiper69

a couple points on harness mounting. one NEVER drill holes in a bar... ever. to mount the rear parts of the harness you can either weld tabs (one on each side of the harness tab to sandwich it) or wrap it around the bar. second, pepople that talk about mouting point waaaaaaaayyyy in the back.....NO. there is a reason this is not allowed (there are nhra rules specifically about this. the reason is the harness material will stretch. not a lot, just enough to be a problem in a crash. third it is correct whoever said you have to mount them hear your shoulder (i think its like at or at most 4 inches below the shoulder). mouting them on the floor is big no no. i know people do it but its not allowed. it has to do with spine compression and makeing you live the rest of your life in a wheelchair. doesnt matter if its a three point or five point, it still needs to be mounted in the same place, there is no "angular deflection". if that were tha case the harness would not be installed correctly. it is suppossed to be installed so that it keeps you in the seat SAFELY. 3 or 5 point installe dcorrectly and PULLED TIGHT (i dont know how many guys leave um loose and say it more comfortable) will not allow you to move at all and thats what they are designed for.


as far as being street legal. i run a five point in my mustang, on the street. not only have i never been pulled over for wearing them, i took the time to talk to local cops in my area. at least 3 towns around me. when i would bump into a local cop, i asked them straight up if i would get in trouble (was polite and explained i didnt want any trouble). every cop i talked to said they would nevr pull someone over for wearing a harness because in their mind even though the hanress is not dot certfied it is still safer. matter of fact most of the cops wanted to check out the car (i guess there arent that many ls1 mustangs running around, and they liked the car) they were always cool about it.

from my experiance most cops dont want to be dicks unless you give them a reason.

racing geek

iTrader: (5)

Leon,

I was wondering the same about the holes in the bar. Since I'm planning on building a motorcycle this Fall/Winter, I'm trying to save as much money as I can. For this reason, I'll probably not pay the guy for a new pipe and just use the one I have but cut it to do my 3 bars welded together idea. By doing this I'm hoping I can avoid the holes.

Stephen was referring to the stock seatbelts when he mentioned the angular deflection, not the 5-pt harness. And yes there is angular deflection in stock 3-pt seatbelts. I believe it is Schroth that even has some DOT approved harnesses for Mini Coopers. They say in the description that they are designed to retain the deflection that the stock belt would have.

I also agree with you about mounting the shoulder belts way back in the trunk area being a nono. I can't remember what the numbers are, but yeah they do strech. For some reason 1" of stretch per 1' of harness material comes to mind. Based on that, mounting the shoulder straps way back there would probably get you atleast 4" of stretch. That brings the driver a lot closer to the nice sharp edges of a third gen dash.

It just occurrd to me that my neighbor is a cop... brain fart! I'll ask him what he thinks about harnesses.

------------------------------

What stock mounting bolts behind the seat could be used for mounting a harness bar? I would think the rear seatbelt bolts would be good enough to use, but are there any others?

Sorry about not having videos posted yet. I'll do a quick edit and post them in a couple hours after I get some sleep. If you havent already noticed, progress will be slow because I've got several projects going at the moment for my car and other vehicles.

Mike

leonpiper69

i found this???? http://worcester.craigslist.org/pts/1198658044.html

doesnt say who its made buy but maybe you could try to copy this design.

racing geek

iTrader: (5)

That looks like the harness bar that is made for 4th gens that Stephen was talking about in post #2. It is made to bolt to the upper mount of the rear seat belts. I've never seen one made for a third gen (1992), but I suppose someone could have made custom made it based off the other design. I can't do that because like I said in post #3, my car is an 87 so it doesn't have the mounts that a harness bar like that would bolt to. All I have there is flat sheet metal covered by the stock interior plastic. I don't even have a hole in that area that I could have it come through.

I tried posting the video on youtube, but for someone reason it wont load in my browser. I also tried posting a video on photobucket but it would never load past 50%. Anyone have any other ideas? I know my computer isn't that great, but I never thought it was this bad.

bluethunder28

iTrader: (1)

How fast are you going that you are worried about the belt stretching that far? Most autoxs are mid 60's and harness bars aren't allowed in time trials without a roll bar. If you hit something that'll stretch the belts far enough to hit the dash pad, you have more to worry than just belts.

I based everything off you autoxing and wanting to keep in the seat. The people that did the harness in the back were Safety Stewards and they past tech with no problem for years. After the event they would unclick them and put them away.

Now if you are planning on using the harness on the street, I wouldn't worry about the police, it's the insurance company that'll be the problem.

racing geek

iTrader: (5)

I usually only get to the mid 50's and sometimes I'll break into the 60's. I understand that I shouldn't have to worry about stretching the belt while autocrossing. There are a couple "pros" with 4th gen camaros that just replaced the bolt for their T-top strap with an eye bolt and clip their harness into that. I'm just saying that in a crash, they can stretch to the point where it isn't even like your wearing a seatbelt. I don't plan on using it on the street. Just for autocross and maybe the drag strip.

I would do the simple click in setup that goes way back, but then I would have to buy new harnesses. The pair I have won't reach back that far, and the new harnesses aren't exactly cheap at around $200 each. Yeah the price may amaze some, but that seems to be the average price for a harness with long shoulder straps. Even buying the shoulder straps seperate will still run me $70 for each harness.

On a side note... Anyone know if there are any rules on how you mount a nitrous bottle? I've got a bottle that I was thinking about hooking up. My plane was to bolt it to the trans tunnel behind the center counsel with a slight angle up so the end of it is above the center counsel lid.

racing geek

iTrader: (5)

Just an update about the legality of a 5pt harness on a street vehicle...

I asked my neighbor yesterday and he said that as long as the person is strapped in he wouldn't care. He also commented about injuries during a roll over and mentioned that a roll bar/cage is also a good addition if a harness is used. He said that some cops may want to see the DOT certification if they are having a bad day but that it shouldn't happen often.

And... I asked another cop about 30 minutes ago. He pulled me over because of "unreasonable impudent speed/display of power." When he walked up to my car he seemed super upset and asked if I was speeding because I was "a kid with a fast car" and he also mentioned that I almost lost control of the car twice (squealing tires). I gave him my license and then he went on about how I should know better since this was just down the road from my house (you could literally see my house from where I got pulled over). What I found interesting though, was that during his rant, he mentioned that I shouldn't be speeding on a neighborhood road and that I should save it for the larger 2/3 lane roads. He ended up only giving me a written warning (the ticket would have been $260 and 6 points) and then asked if I had any questions. I was unsure if I should ask about a harness since I just got pulled over for reckless driving, but I did anyway. He said the same thing my neighbor did. He wouldn't really care as long as the person was strapped in. When I mentioned that most 5pt harnesses aren't DOT approved, he said that he still wouldn't mind but I should check with the DOT in case another cop had an issue with it. I also mentioned that I autocross and the seats I have do a good job of holding me in but a harness would be a lot better which is why I was wondering about the harness. He must have relaxed a little after I said that because then he started asking me about my car and talking about his Corvette. I guess I should be happy he was a car buff.

Edit:
Anyone know how many written warnings you can get before something else happens, or are written warnings never actually saved to your name/license? I'm thinking I might be pushing it now... 3 warnings (one was only about a burnt out taillight).

FueledSoul

iTrader: (18)

i dont know but i always keep a nice ice cold beer next to me in a cooler in the car just in case i have a run in with one. they seem to like thos on hot days

customblackbird

iTrader: (15)

i thought the 5 point harnesses where legal for street use... if anything they are safer than 3 points. ive smacked my face on 2 steering wheels with the stupid stock 3points lol.

im a cop magnet as well, my car at 2500 sounds like im goin 95mph so i get pulled over just bc... and then they find something to give me a ticket for. watch out for written warnings... they stay on file in there system and they use them to see if youve commited the same offense twice. if uve received a warning and get pulled over for the same offense... most likely u will be recieving a ticket.

the most i ever racked up at one stop was 14pts and 1000$ in fines lol. i was racing my bros vette on a hwy. doubled speed limit 120mph, wreckless driving, yadda yadda ;P

if i were you dont mess around, instead of a harness bar, install a 4pt bar. solid foundation for 5pt harness, legal, and will save your A$$ if you roll over. you could even weld in the door bars for a 6pt but use a swing out kit and just remove the actual bars. u cant even notice the door bars mounting points with the actual bars removed.

my brothers 68 vette has had 5 pt harnesses in it for over a yr now on the road and never has had issues with the cops

Spifz

I know you don't want to buy new harnesses, but just for anyone who wants ones long enough to attach to the deck lid/rear seat belt mounting, the Corbeau 5-pt ones are long enough. You can even double up the strap almost the whole way between the seat and the back deck lid.
Definately reinforce if you are hooking on there. I used a piece of 1.00x.750x5.00 steel so I could drill/tap it for the 7/16 bolts that Corbeau ships with the belts. The blocks are tied into the shock mount and the plates for the rear cage bars, so I'd trust it to the breaking strength of both rear straps. My shoulder belt angle comes out around 10 or less degrees below horizontal, which is within what Corbeau (and FIA > nhra) recommends. I took the padding off the carpet in the area of the reinforcing blocks; without the belts bolted in, you can't even tell they are there. (See vid near the end of this thread: https://www.thirdgen.org/forums/fabr...n-model-3.html

(3" Nylon strap is rated at 10,000 lbs breaking strength, 3" kevlar is about 11,000. Maybe 'seat belt strap' is tougher though, so the numbers are just for info.)

bvahnee

iTrader: (2)

Here is a picture of the harness bar I had made :

http://img190.imageshack.us/i/img4160z.jpg/

Grade 8 bolts into the stock belt location with two half inch CNC milled plates welded to heavy duty piping. I did this along with a few other things as a high school project.

jjlabinski

FYI

I designed and built something similar to what you are looking for. I posted it on here a few years ago and got some smart &^* comments about the structual integrity. I too did FEA on the design, proved its reliability and have it installed in my ride.

Do a query on my name here on TGO and you are bound to find some pics.


Jeff

racing geek

iTrader: (5)

Yeah that looks simply and effective, but isn't that a little high? Maybe it's just the angle of the picture. Problem though is I don't want to drill any holes anywhere or in anything. My interior is mint so I don't want to ruin anything by drilling holes in the floor or cutting the headliner and/or plastics. I want this to be in a sense just like the fourth gen bar that Stephen posted a link to above. I want it to go in and out without disturbing anything.

I did the search and all I could find was this... https://www.thirdgen.org/forums/inte...t-harness.html
Apparently you deleted the photo from your post. Would you mind taking another picture or posting that same picture again?

----------------------------------------------------------------
I came up with a few different ways of mounting this. Unfortunatly I still can't do any stress testing because I still don't have access to the the program. I'll be getting my laptop from MSOE soon (I think it's a week or two) so I'll start playing with the programs on there. Hopefully I wont have to teach myself a new program and I'll be able to start were I left off. I've pulled the back seats out so I can get a better idea of what stock mounting points I can/can't use. The car looks a lot lighter and roomier with them out, but I probably didn't save much weight. I probably took off just as much weight as the AC did.

I didn't abandon this idea/project. I will for sure have it done for Third Gen Fest 2010.

Mike

customblackbird

iTrader: (15)

bvahnee... those straps are too high... they are suppose to be within 4" of the shoulder height while sitting but below the shoulder or shoulder height. also how are the secured? look like they arent looped around the harness bar correctly.

bvahnee

iTrader: (2)

I know they are too high, Im designing a new bar that will hopefully fit better. I wasnt trying to sell them off as the safest thing ever, sorry if that was the impression. I didnt know anything about harness bars when I had it made, but thanks for the info.

camaro_doc

Racing Geek

Keep up the work i am very interested to see how you wrap up this project!

racing geek

iTrader: (5)

I'll have access to the programs I need starting tomorrow afternoon. I've changed the design again so I'll remodel everything, do some more computer testing, and if everything seems ok I can get trigger happy with the welder and grinders and all those other fun tools.

HCR13

iTrader: (5)

Have you considered maybe using the bolts that hold the hatch support struts? Maybe making a straight bar and having the ends flat and at 90* and bolt it between the hatch strut and the body bracket?... Thats probably what I would do... As far as integrity, those body brackets support the EXTREMELY heavy glass hatch, so they should be plenty strong to keep you in your seat. Thats probably what I would end up doing soon when I get some harnesses...

racing geek

iTrader: (5)

I have considered it... then a week later one of the bolts shot out of its threads and the hatch almost dropped on my head. Now I try and open the hatch as little as possible. I have to get a heli-coil kit or something to repair the threads.

The current design I have planned will only use stock seat belt bolts and bolt locations. The only problem I see is figuring out which material will be strong enough that the bar wont flex but yet still be light enough to make this worth while. If it gets too heavy I might as well just weld in a 6/8 point roll bar.

Problem.....
The program I got on my school laptop isn't the same one I was using a couple months ago in High School. Instead of using Inventor, now I have to use Solidworks. I haven't looked at the program much, but I would think it would be very similar to what I'm used to. If not, progress will just get slower.

Thanks for not letting the interest die.
Mike

bvahnee

iTrader: (2)

Heres a revised edition of the harness bar I made. The tubing is 3/16 mild steel, preformed 90 degree's and cut to size straights. The plates that hold it in the stock location are 3/4 inch CNC milled mild steel, everything is mig welded. I listened to a couple suggestions and added a 4 inch extention to the first design and now it sits a lot more comfortable. The bolts used to hold the bar in place are grade 8, and the ones for the harness are grade 5 7/16. I havent used any program to see the stress tests but for a daily driver it seems plenty safe for me. Oh, and now I can see out the rear view mirror, thats a plus.

http://img2.imageshack.us/i/090809124302.jpg/

Edit: I forgot to mention it weighs nearly 20 pounds, maybe more. Weight isnt an issue with me, Im not running a/c or smog or a stock engine, so ya.

racing geek

iTrader: (5)

You should have mounted the harnesses to tabs that would be welded on. When you welded the pipes together, did you use plugs? Like slip a slightly smaller tube inside then weld it in then slip the curved portion on and weld that on? I'm pretty sure that's what you're supposed to do in that situation...

-----------------------------

The program on my new laptop is not what I'm used to. I was used to using Inventor 7 and this is Solidworks 9. It's good that I have the newest version of the software, but it isn't too good that I don't know how to use it. Hopefully I'll be able to find some spare time in the coming weeks to figure this out.

Mike

bvahnee

iTrader: (2)

So your saying the stock location, 2 threaded holes each side, isnt strong enough? I guess that would make sense to some extent, the threads probably cant hold the 150k psi the bolts can. Again, its a street car, goes 65mph tops on a regular basis. As such, if I were racing the car Id just opt for the 8/10 point cage instead, which actually uses thinner tubing than I did, but obviously designed differently. If you truely think this bar wont hold up in a crash, give me a way to test it (safely), otherwise I think it is miles ahead of the OEM seat belt it replaces.

Edit: After looking at actual harness bars (the kind you buy online, sparco, etc), which all "bolt" into stock location, are you saying those too are not safe? Or do the turn buckles attached to the floor actually make that huge leap from my bolt in style to "safe"? Just asking, I realize your knowledgeable in this area so Im trying to suck as much information as possible.

Edit Edit: I just had an idea, similar to what aftermarket harness bars have, turn buckles, how about if I added a vertical bar (each side) that was bolted to the lower seat belt location and then welded to the bar? Or should I really stay away from bolting stuff in?

I dont mean to thread hijack, I think the info to these questions can be used by everyone on the boards, especially the original poster, with ideas and such. Thanks.

racing geek

iTrader: (5)

Correct, the stock bolt locations may not be as strong as you think... at least in your situation. Think of how leverage is acting on the bolt... with the stock seat belts the forces are only like 1" away from the bolt, and with your harness bar coming down for the harness to attach too, the forces are now like 1' away. This is why your design still may not be as strong as you think it is. Since you had to take the fun out of testing recommendations by saying "safe", all I can think of are crude ways of testing it or methods that require a lot more time and access to high dollar programs. Anyway... to illustrate the leverage point I was trying to make above, sit in your backseat and yank on the bar hard as you possibly can. If it flexes even a little, then imagine what a crash at 65mph will do.

The difference between your bar and a harness bar from Sparco is that their bars use a wrap around harness (no holes in the structure to create high stress points that would lead to part failure). Yes, you are right... they do use stock mounting locations. However, this comes back to my leverage point. Your bar uses a hoop with two mounting points on the ends... theirs use a hoop with two mounting points on the ends, but they also have extra support bars. These extra bars help absorb some of the forces exhibited during a crash which all the stock mounting points to be used "safely". Also, because of where the extra braces mount to the actual harness bar, their bar is essential just that... a straight bar.... not a hoop like yours.

One example I can think of uses a hula-hoop. Holding it horizontal, grab onto it at what could be 1:30 and 10:30. Now have another person push on it either up or down. Notice how it is still pretty easy for the person to rotate it even if you try and squeeze tighter and lock your wrists to try and prevent movement? Now get a third person... Continue holding the hula-hoop horizontally and have one person hold the bar at 1:30 and 3:00, and the other person hold it at 9:00 and 10:30. Once your holding it tightly, have the third person try and rotate the hula-hoop again. Notice it still moves (due to the thin plastic) but nowhere near as much as the first time. This is essential the difference between your harness bar and the one offered by Sparco. The extra bracing adds a significant amount of rigidity to the bar. Did that make sense?

Oh, one last thing... you never go above 65mph in your car??!!??!?

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Just to give a sneak peak at what my current design currently consists of... it will be using 6 stock mounting points, and 5 bars. One will be a heavy duty main bar... the hoop, and the other 4 will be smaller/lighter support bars that will help prevent any lateral and fore/aft movement. I'm guessing the entire weight of my bar will be low 30's, but I'm just hoping to keep it below 35 pounds. Keep in mind that I'm designing the bar to be capable of higher speeds then most will see or probably want to see on the street. I do plan on taking my car on a road course where triple digit speeds will be common and I plan on using this harness bar at that time. (I don't plan on making frequent trips to the road courses, but maybe once a year... autocross will still be my primary use)

My homework for one of my classes is to go through the tutorials for Solidworks so I don't have to worry about time as much. The only problem is that what I want to do is one of more the advanced applications of the program so that may take some time build up my skill to that level.

Mike

Twin_Turbo

iTrader: (25)

That last pic is scary, the whole bar puts a tremendous leverage on the attachment points on the roof, the belts are bolted on in shear, not even double shear..that is one scary setup. if you crash @ 10 mph you will be killed by that bar smacking you in the back of the head.

bvahnee

iTrader: (2)

I get the most of your explanation, so I think what Ill do it add some support bars, similar to the sparco but way more permanent, I have no use for the back seats as is. I guess what I will do is have the hoop, plus two bars angled back towards the rear of the car, and then mounted to the frame just under the seats. Oh, and what I did to test the car first was put a come-along on the bar and then mounted the other end to my brothers truck, put the two cars end on end, and began pulling. There wasnt any flex in the bar at all, but I didnt crank the crap out of it, I was scared lol. Im not sure if this makes any difference at all, but the 3/16 tubing goes past the mounting points. What basically happens is the tubing gets maybe 1/16" from the roof before bolts go in, then once its bolted in the tubing is making contact with the roof, so imagine putting making an L shape only with the plate backed off a little, then bolt it to something. To put it simply the mounting point is not flat, its basically a 3/4" piece of steel with a piece of tubing sticking through, so that once bolted its touching the roof, kind of like in the "pit" where the old seat belts went.

Oh and what I meant by not going over 65, the only time I went well over that was at the track, which I only hit 96. Highway driving sucks now because I got 3.42's in the back so I keep it around 60-65 to keep the noise down.

In any case Im going to add some support from the bar to the floor this weekend. Thanks for the help

Edit: I found a picture of what I mean so you can see what it looks like not bolted in, http://img406.imageshack.us/i/dscf1748c.jpg/

On the right hand side you can see the bar sticking through, its like that on both sides. When I made the bar I bolted the plates in first then held the bar up against the roof and then marked it to be welded.