Sgtblue

iTrader: (16)

Not necessary.
Build it....please. I really don't want to install a rollbar which IMHO would be overkill for AX. But I need something solid for a harness that's still compatible with divider and cargo cover when reinstalled after an event. Given that the M2 version is no longer available (AFAIK), I think you might be surprised by the interest if you can keep it at or below $300.

rockshox

iTrader: (3)

If its anywhere near as cheap as youre predicting then Im in. Would be nice to have a matching front piece as well. Ive always wanted a way to mount a harness without having a full roll cage but I completely agree with your analysis of the existing products so I was never willing to trust them.

saxyman990

Well, to be honest, I think the cost is the most challenging aspect at this point. My goal is to keep it around $300. But given the increasing cost of raw materials, labor, and machining, I really think that goal might be too aggressive. A price point closer to $400 is probably more likely. Although, you can take my word that I would do everything in my power to keep end-user cost to a minimum. I've already changed a few details that will reduce machining cost, yet not compromise the design. I still may do some more design iterations...

-Rob

XxMerlinxX

iTrader: (2)

Saxyman, shoot me a PM when you have everything ironed out with the design. Labor down here is a lot lower and I have a few friends in the business that might be able to help, I'm fairly positive we could get it down into the $200-$250 range.

saxyman990

As I mentioned, that price-point is not exactly a prediction, it's more of a goal, and a quite aggressive one, at that. In all honesty, I don't know if I'll be able to hit it.

Also glad to know people would be interested in a matching front bar.

Thanks for the support!
-Rob

saxyman990

Merlin: thanks for the info! Be warned, I just may take you up on that.

-Rob

RotaryWhat?

iTrader: (1)

First---just wanted to say nice work. It's always great to see people actually applying engineering knowledge to their passion (limiting design by trial & error). This is exactly what I'm looking for since I don't want a full roll cage on my street car, but it would be nice to have something for HPDE's and AutoX (like you, everything else I've come across looks poorly designed). I had a few questions though:
1) Does the slot in the cross bar (at each end) go all the way through?
2) What type of aluminum are you considering & what material properties did you assume for your FE analysis?
3) Would you mind sharing your boundary conditions, the Von Mises stress plots on the eye bolts/bar assembly under load, and also the first Eigenmode/freq. of the assembly?

-Ken

saxyman990

Ken, thanks for the kudos

1) Yep, slots go through the bar
2) Prototype will be constructed from 6061 in a T6 temper (all components). Most analysis was performed with this aluminum in mind, and stresses stay below the yield strength by an acceptable amount. I might use 7075-T6 for the central bar (if cost doesn't skyrocket out of control) simply to increase the SF. Mounting brackets will remain 6061-T6. Assumptions made in most FEA analyses were with a modulus of 1e7, and poisson's of 0.33.
3) I don't mind posting some of that information to give you an idea. The fringe plots in the initial post are actually Mises stress plots. However, I've probably done close to 100 different analyses, all with slightly varying assumptions and BCs. Also, please understand that I am extremely hesitant to post detailed information and specs simply for proprietary reasons. When I get a chance, I'll re-run some of the analyses and post some pictures/information.

-Rob

turBRO240

iTrader: (1)

I hope you know that if you have a 55mph+ collision, your shoulders are going to break and be forced into your chest collapsing your lungs and punchuring your heart.. and possible paralyzation of the stress and breaking of your spine if your not already dead from the shoulder situation i described in my previous sentence.

Get a real harnessbar and attach it to that. Dont be stupid.

RotaryWhat?

iTrader: (1)

No problem Rob---I understand your concern with sharing the info. As far as the stress plots---there was no scale on them, and I was also curious how the eye bolts affected the analysis. The eigenmode/freq. question was related to me wanting to put a camera mount on there....didn't want the first mode of the bar assembly right on top of a chassis mode....

-Ken

dclin

iTrader: (4)

Totally IMHO, but nothing goes with CNC parts like a brushed finish. Just something very functional about it. Less expensive to produce than polishing I'd imagine, in any case. I remember seeing a pic of a race car or hi perf version of a street car (an Aston, IIRC) that had front CNC tower bars; very sexy.

If you do decide to provide a multi-point option, it could be just that, an option. I'd guess it wouldn't be too hard to engineer some extra mounting points to a 'regular' two point bar, at not too much additional cost. Cusco offers a triangulation option for it's rear bars (last pic):

http://cusco.co.jp/english/e_strut.html

Speaking of which, could a similar option be available for the rear (assuming it really does offer a benefit)?

As far as cost, the $300 range is reasonable given the engineering you've evidently put into, not to mention the pure sexiness of CNC parts. I've been inquiring about ordering the Autoexe set (front and rear), which looks like is going to be about $700 to my door.

Hurry up and build it.

XxMerlinxX

iTrader: (2)

How would that situation happen? His mounting points are above and behind him, therefore there's no compression of the spinal column. It's only when the mounting points are lower than your shoulders, and the more so the worse, that you get the compression that's so dangerous.

saxyman990

Ken,

hmmm... you're right, there was no scale on the fringe plots. I think those pictures were taken at an earlier stage when I was toying with different mesh configurations. I didn't usually have the scale visible.

Also, there are no eye-bolts in my design. I use a drop-through quick release pin. The load is centrally mounted, and the analysis is virtually unaffected by them.

Excellent thought about the eigenmode analysis with regards to a camera mount!! I'm sure that the bar doubling as a camera mount would be fairly common for track go'ers. I'll do a little more analysis in this area to see where I'm at (and possibly adapt the design accordingly). Stay tuned....

-Rob

saxyman990

definitely a possibility. Wouldn't be too incredibly difficult once I design the basic structure. The question would be if it has any benefits to make it worth-while. I'll have to do a little more research in this area...

Yep, a similar system could be made. However, it would probably cost more money than most people are willing to pay, would require interior alterations, and would probably provide minimal (if any) benefits. But I will definitely look into it, and give it some thought.

I'm trying

-Rob

M104-AMG

iTrader: (8)

As always, a wonderfully thought out product.

I do have the full "Race Shop" roll-bar with diagonals on the main hoop and rear support diagonal. The roll bar also has an additional horizontal harness hoop, and seat back-brace.

I personally have my harness looped around the Race Shop horizontal bar between the rear-strut towers bypassing the use of eye-bolts.

Too bad this can't be made to replace my Race-shop horizontal rear-strut bar.

:-) neil

Basically the same config (mine has the seat brace, harness bar, and a different (not M2) strut-brace), unfortunately, not the same car!

RotaryWhat?

iTrader: (1)

Good god I'm retarded---I see what you did. Never mind my question. The assembly should be stiff enough to put the frequency well above 100 Hz, but I've seen results in the past where a long bar like that can be down around 20-30 Hz if not stiff enough....

Keep up the good work, and let me know when I can buy one!

turBRO240

iTrader: (1)

The optimum situation is having the harness bolted at a 45 degree angle from the shoulders. The description the other poster described were for (and im assuming) mounting it in the mouting points of the REAR lapbelts?

Am i missing somthing?

XxMerlinxX

iTrader: (2)

I was thinking he has the harnesses up and at an angle to where the belts come out of the b-pillar in the back (if that's where they go, can't say I've really ever looked for where they come from). If he does have them go down the back of the seat and then bolt into the bottom, then you're definitely right, he'll get his spine crushed.

turBRO240

iTrader: (1)

Unless he has JDM backseats (which supply the mounting points) i dont see how its possible to mount it the way he described. You wont be able to mount the harness of OEM seatbelt mounting point on the b-pillar because that will only supply one mounting point... so wheres he going to mount the other harness strap?

But yea.. i was just trying to make a point.... ive personally seen alot of injuries and fatalies because of incorrectly installed saftey system (whether it be seats, seatbelts, harnesses, airbags, etc.)... so, just lookin out.

Even though theres countless hours and effort going into the engineering and contruction of the saftey equipment, it all still depends on the user...... unfortunatly saftey systems are desgined to work in ideal situations but also acomdate as much as possible to a situation other than the ideal (incorrect mounting and such of the equipment or position of the person/object and such) in an impact.

aoc007

iTrader: (5)

So theres no way to make it work with the cargo divider? My amp is mounted to mine and taking it out is a real pain. I just started looking into a harness but it looks like this may be the one I want.

dclin

iTrader: (4)

Mounted to it directly?! You might want to reconsider this if so; doesn't take any one of these engineering types to figure out what 15lb+ projectile would do, bouncing around inside the cockpit in the event of an accident.

saxyman990

Not with my design, no. Take a look at the picture that Neil (M104-AMG) posted above. Notice how the harness bar is below the top level of the divider? This kind of limits our options. You could do what most harness bar manufacturers do, and simply use eye-bolts. This will extend the mounting location to a point above the divider. Unfortunately, as I already mentioned, this can put some extreme twisting forces on the bar, and is NOT the ideal situation.

The better option is to go directly through the centerline of the bar. Unfortunately, this requires that the divider be removed. I suppose as an alternative, you could cut some slots through the plastic divider, so that the shoulder harnesses go through it...

Also, I'm in agreement with dclin. I wouldn't personally mount anything of substance directly to that plastic divider...

-Rob

BobfisH

I do have JDM back seats.

I was told as long as the belts are at least 45 degrees from vertical under tension id be fine. (apparently this is a regulation in some US race series?) Currently the two shoulder straps mount onto the lower seat belt mounting points for the rear seats in a JDM car - which is about kidney height at 2 feet behind me.

Ill get some pictures and see what you think, i want to be safe. From what i was told this would be ok, but we will see. I do see how some spinal compression would certainly occur in this configuration, but i wouldnt imagine itd be a lot. But as i say, proof in the pictures. Ill start a new thread as to not hijack this one.

And saxyman, i'd definately be interested in this product $300.

aoc007

iTrader: (5)

It's bolted to the side paneling and is pretty secure, but I've only done one trackday with it on. When I was installing it there wasn't a better place to install it really.

slow7NC

Nice work Good luck with prototyping and production