im almost ready to buy but i have a couple more questions you can hopefully answer. exactly how much force was it able to handle in simulation? what are the dot/fia/etc specs regarding harness attachment strength. what is its strength resisting side and twisting loads presented by the shock towers under cornering. was any simulation done on offset impacts? those bolts and especially those tiny pins can handle the shear stress? sorry for all the questions but my life may depend on a harness some day.

Well, hopefully I can shed some light on those questions. I'll address them each individually:

I'll start with this one. Each of those governing agencies actually have fairly similar requirements when it comes to loads/forces. In a nut shell, each mounting point needs to be able to withstand 3000 lbf without yielding.

Design and analysis was performed so that the bar can maintain 4 points of simultaneous loading at 3000 lbf. This is with a safety factor of well over 2 (meaning the bar can actually withstand more than 6000 lbf on each of the 4 harness mounting points simultaneously).

Actually, the strength under side loading and twisting is considerably larger than for the harness loading-direction discussed above (many, many times larger). The bar system is extremely strong in both tension, and compression. The weakest form of loading is the bending incurred by the shoulder harness loads.

Yes. I took an extremely large variety of different loading conditions into account during analysis. Keep in mind that even large auto manufacturers cannot accurately predict results from EVERY possible impact scenario. So there's no way you can place any kind of guarantee when it comes to this.

Yep. Those “tiny pins” are Grade-8, which can handle more than 130,000psi of stress. Even with their diminutive size, they can still handle well over twice the necessary forces without any issues. As a side note, most racing sanctioning bodies (including FIA, SCCA, NASA, etc) only require 3/8” Grade-5 mounting fasteners.

I know, me too :) . This is exactly why I refuse to use any other harness bar that is on the market, and decided to design one that was up to the task.

Great questions, by the way!
-Rob

Unfortunately, an extra $30. :( Sorry fellas. I'm still looking for a better method of shipping there, and if I find one, I'll let you know.

-Rob

Yep, I'll be sending a full set of standard pins with every bar, even if you purchase the push-button quick-release ones.

-Rob

Now :)

-Rob

By now, I should have personally contacted everyone who has expressed an interest in this new harness bar. If I have not contacted you, or you're late to the game, then please LET ME KNOW!

-Rob

Can you still put the black cover back on for when the bar is not in use?

Also, this is made of aluminum. What is the fatigue resistance factor compared to steel? I know aluminum wont last as long when stressed regularly. It just makes me wonder since this is mounted between the strut towers, and will put under load at every corner.

My primary points of interest are the eyelets where the crossmember bolts to the brackets. that is where the aluminum is the thinnest and also where any fatigue-causing bending will occur (however minimal) during cornering.

Just looking to clarify. I have built a few experimental aircraft, 2 out of all aluminum, and fatigue is a large factor in material choice. Any area that could be subject to flexing was reinforced significantly by using some sort of channel stock or backed up with steel.

The plastic vertical divider in between the cockpit and the truck needs to be removed when the harness is in use. It can be put back in when the harness is not in place. The horizontal package tray (or hatch cover) can remain in place at all times if desired (of course, you also need to order the optional "hatch cover mounting brackets").

Well, as you pointed out, aluminum is not nearly as fatigue resistant as steel. It does not have an actual fatigue endurance limit like steel. Therefore, we have to define a lifespan based on loading cycles, and design around that. In this case, I defined loading cycles based on maximum/average tension and compression loads seen in high-g turns. The bar has been designed to handle more than 6-million cycles.

To help put that in perspective, let's look at it like this: Let's say you run your car mainly at Mid-Ohio (my personal favorite:)), which is a relatively high-speed 15 turn course. Let's also say your normally run 50 laps in a day, and you're extremely wealthy with nothing better to do, so you also run 365 days a year. It would still take you more than 10 years to notice any type of fatigue crack.

Also consider that all of your main suspension components are made from cast aluminum, and generally see much greater alternating loads than the shock tower bar would.

So basically, fatigue shouldn't be a problem :)

-Rob

I think he was referring to the black cover that goes over the stock strut tower bar?

Oh! Good catch, I must have misunderstood

Yep, the plastic shock tower covers can remain on at all times.

-Rob

But not the one that goes over the actual stock bar, right?

If you get the hatch cover mounts when you order the bar you can put everything back on just like the stock unit. The divider, the covers over the strut tower, and the hatch cover that hangs from the hatch and pivots off the bar.. When racing just pull the hatch cover and divider out and hook your harness up.. Good to rock... Sweet bar and setup, I'm going to have to order one.. Rob I'll shoot you a email later tonight, want to ask you about some stuff...

A bit OT, but any thoughts on where to mount the lower belt connections?

I am purchasing one - black with hatch cover mounts, even if it doesn't have a cool RX-7 logo. Rob, do you see a theme here? <grin>

The lower two lap belts can be connected in the same location as the stock lap belts. Eye-bolts are available from places like Jegs or PegasusRacing that directly replace the bolts that secure the stock lap belts. This allows you to keep your stock lap belts for street driving, and gives you a place to snap-in your racing harness.

These mounting locations are reinforced from the factory, and are more than strong enough. Also, in this configuration the eye-bolts are loaded in the proper configuration and direction, so their use is perfectly acceptable.

If you use a 6pt harness (something I HIGHLY recommend, especially while using the stock seats), then the two anti-sub straps can be mounted in the same spot.

-Rob

Per Schroth Race Harness "A seat that was not originally desiged for use with a racing restraint should never be modified to accept an sub strap."

http://www.schrothracing.com/products/competition/1598

Also they are the only company I can find that is DOT legal on the road??

are there really no others that have a orange center push-button release? (i believe thats the DOT requirement)

insnt there only a single attachment point (inboard) for the belt attachment on either side? where would the reinforced point be outboard?

I would like to use a pair of Sabelt 6-Point harnesses with this, but they have a million different kinds on their site. Does anyone know which one would work well in an FD? Thanks

-Andy

The lap belts and anti-sub belts can be mounted to the same eye-bolt. The sub belt should be snapped inboard of the lap belt.

-Rob

Reminder
 

Just a reminder, if you are interested in this harness bar, you need to contact me IMMEDIATELY. A small production run is in the works, and there will be only a handful of bars available.

-Rob

Anychance youll have this in the near future? Or other time?



Also: Is there anyway to use the Scroth Autocontrol III with this harness bar?

I'm not intimately familiar with their device as I've never seen one in person. However, as I understand it, they have a "mounting adapter" available that would probably work. It would provide an extension to enable the inertia reel to bolt to the harness bar.

-Rob

For those of you that have already placed an order, thank you. The parts are scheduled to be completed in about 4-5 weeks. They should be shipped to you prior to the end of September.


For those of you that still may be interested in the harness bar, I am able to continue accepting orders up until the 27th of August(Monday). This slight extension is a result of some scheduling changes made with my machinist (please note, this extension to the order placement date should have no effect on the original estimated ship date).

So once again, get your order to me prior to the August 27th in order to be assured you will get one.

PM me, or visit my website for details.

-Rob

Rob, looks nice....I think I may have totally forgotten how to do all of this stuff now....ha

what the heck is all this about "Axiom Autosports Engineering"?? are you still in or did you get shaped?

i don't ever come on here anymore - no time to mess with a car in Japan really, but I might be interested in one of these if you're only going to end up making a few and not do another run of them.

Holy crap! It's Nic! I haven't talked to you in ages man. You still over there in Nippon? I figured they would have sent you back state-side by now. How you doing?

Axiom is just a small part-time business that I have on the side. I primarily do for-contract design and CAD/modeling work. The AF still has their claws in me. They're actually sending me back to CO pretty soon....

I'm honestly not sure if I'll ever do another production run of these. If I do another one, it probably won't be for another year or so. Just depends on if there's enough demand I suppose

-Rob