Removable side bar ideas for 818R used on street

[ZincBoy]

I recently picked up my 818R kit and am looking at modifying the chassis to allow the upper side bars to be removed.

The general consensus seems to be that these bars would be a head crusher if used without a helmet and I agree. I would like to make them removable so I can drive the car on the street on occasion without a helmet.

The other concern is to keeping the chassis able to pass race scrutineering.

FIA: rules seem to allow for removable elements of the roll cage if using the correct joint type (FIA Appendix J, Art.253, 8.3.2.4)
NASA: Rally would seem to not allow this mod, but I am not sure as they do reference the FIA Appendix J document. Time Trial and HDPE seem to be fine
SCCA: Seems to be fine but the rules are not clear about exact joint requirements. The FIA joints might be acceptable, but I am not sure.

Using the FIA Appendix J as a reference, I came up with the following:

There are three cuts to make. One close to the main hoop that leaves a ~3" stub needed for the joint. One close to the dash leaving about 2" sticking out to allow the removable member to be bolted in. And finally, the vertical support member cut about 3" above the small forward brace.
Removable_door_bar_cuts.jpg

A quick mockup in CAD to show the joints. All joints are made with 1.75", 0.12"wall DOM tube. SCCA rules may require use of a double bolt per joint so the FIA 253-41 style joint would need to be used instead. The overall length of the coupling sections remains the same at 5.75"
Removable_bar_joint_detail.jpg

An overview of the parts of the connection system. The vertical tube connector must be welded to the removable section as there is not enough space for a fully bolted joint.
Removable_bar_exploded_view.jpg

Some areas of concern:
1. The stub on the main hoop sticks out about 3" into the driver/passenger area. I think that this is out of the way and highly unlikely to intersect with a head in an accident. This may also depend on the seating system used.
2. The forward section of tube under the dash may need some bracing to keep it from moving when the bar is not in place.


This seems to meet the needs of a removable side bar system for the 818R but I am not an expert and thought I should get some feedback before cutting my frame

[TahoeTim]

just pad them

are you adding the windshield and wipers too?

[longislandwrx]

Even with a bunch of padding your head could hit and give you a pretty serious concussion if not worse.

I like you idea, I considered doing something similar, but I'll probably just go with a full containment seat @ +$200 each per side. It's easy to slap on a helmet.

looked at these:

http://www.appliedracing.com/roll-ba...vis-mount.html

I had a link so some really nice interlocking ones but I cant find it at the moment.

just pad them

[apexanimal]

these are very nice... although i don't know if they meet the requirements necessary...

http://www.ballisticfabrication.com/...mp_p_1467.html

[FFRSpec72]

This would really be questionable in NASA and would not fly in our international conference (as folks have tried this with spec Miata that they wanted to drive on street). This also does not allow you to have any intrusion protection like 1/8 steel to cover the side of the cage. My challenge car was spun (taped in the rear) and i was hit at 60 mph in the drivers door as I was in the middle of track, and w/o the intrusion protection on the cage I would have really been in serious condition, but the intrusion protection does 2 things, it spreads the impact across the bars and also keeps sharp object out of me. I personally would never do this modification, I occasionally drive my challenge car on the street and it has the same setup as the 818 with the cage and I would rather take a chance of hitting my head on the side bar than remove it and take the chance of getting hit and have a weak cage collapse because of altering the strength. I personally feel this is a really really bad idea to consider.

[JeromeS13]

Just wear your helmet on the street. Done.

[Santiago]

If I am not mistaken, the Challenge cars front down struts have a bend in them that offers a stand off to move the bar away from the driver's head. So what might make for a tolerable risk in that car may not translate to the 818.

I dunno. For any wheel to wheel racing I agree with Tony, it is not likely to pass NASA tech. For HPDE you are probably fine. The OP didn't say if w2w was a definite use.

Engineering treatments seem to frown on any bolt-in solution, so it's an uphill battle any way you look at it. I like the idea of removable bars, I just tend to have severe reservations about most specific designs. For this one, my concern is the one already mentioned, the little 3" spuds by the driver's head.

Best,
-j

[FFRSpec72]

If I am not mistaken, the Challenge cars front down struts have a bend in them that offers a stand off to move the bar away from the driver's head.

Yes the bars are bent out but you still have same issue (as you can hit your head), these have to be padded per rules. I see folks riding dirty in their street cars with their heads right next to the B pillar so I imagine they have the same issue

Once you cut the bars you can never go back (as welding would not be acceptable to try to restore the cage), that would be a real concern.

[Pearldrummer7]

Just wear your helmet on the street. Done.

I plan to street my R and treat it just like I'd treat a motorcycle. Helmets are badass, anyway

Then you don't risk the integrity of the roll bars from a safety or handling perspective.

[RM1SepEx]

Removable_door_bar_cuts.jpg

can you do me a favor and measure where the lower seat belt tabs are welded on your frame? dimension from the back of the tab to the rear firewall tube would be excellent. It looks like about 11-12 inches in your photo above. We don't have them on the S frame and I'm about to weld some in for my stock belts. Attaching the belts to the seat brackets isn't strong enough IMO

[FFRSpec72]

can you do me a favor and measure where the lower seat belt tabs are welded on your frame? dimension from the back of the tab to the rear firewall tube would be excellent. It looks like about 11-12 inches in your photo above. We don't have them on the S frame and I'm about to weld some in for my stock belts. Attaching the belts to the seat brackets isn't strong enough IMO

There are lap belt mounts and crotch belt mount and then the shoulder belt mount on the roll cage. Are you only talking about the lap belt mounts?

[RM1SepEx]

yes, the S frames have mounts for the inertia reels, (sedan and wagon) as well as the upper belt pivot point but no lower attachment points

[ZincBoy]

This would really be questionable in NASA and would not fly in our international conference (as folks have tried this with spec Miata that they wanted to drive on street). This also does not allow you to have any intrusion protection like 1/8 steel to cover the side of the cage. My challenge car was spun (taped in the rear) and i was hit at 60 mph in the drivers door as I was in the middle of track, and w/o the intrusion protection on the cage I would have really been in serious condition, but the intrusion protection does 2 things, it spreads the impact across the bars and also keeps sharp object out of me. I personally would never do this modification, I occasionally drive my challenge car on the street and it has the same setup as the 818 with the cage and I would rather take a chance of hitting my head on the side bar than remove it and take the chance of getting hit and have a weak cage collapse because of altering the strength. I personally feel this is a really really bad idea to consider.

I appreciate the feedback!

For the 818, I would think that putting a plate over the upper triangle formed by the support bar would impede visibility to the side? For the lower door bars, it is a really good idea and I plan to add something like that to mine. Especially since the doors are open shells on the R. Did you weld or bolt the panels in?

The challenge car also seems to have a bar that slopes more sharply down and away from the drivers head. I would be much less concerned driving on the street with that setup.

Strength wise, a properly designed joint would be stronger than the rest of the bar. This bar is only really strong in tension and I can't see the joints as shown weakening it significantly. That being said, I have not run the calculations yet and would do so prior to making any changes.

Thanks!

[ZincBoy]

these are very nice... although i don't know if they meet the requirements necessary...

http://www.ballisticfabrication.com/...mp_p_1467.html

those are the ones I was talking about. double bolt, should pass inspection, with or without padding hiding them.

I did see these joints and I like the look of them. Unfortunately, they do not appear in the rules books in the approved drawings. I also couldn't find anyone selling them as FIA/NASA/SCCA approved connectors.

[FFRSpec72]

can you do me a favor and measure where the lower seat belt tabs are welded on your frame? dimension from the back of the tab to the rear firewall tube would be excellent. It looks like about 11-12 inches in your photo above. We don't have them on the S frame and I'm about to weld some in for my stock belts. Attaching the belts to the seat brackets isn't strong enough IMO

I replied over in another thread on seat belt mounts the position of the R tabs

[FFRSpec72]

For the 818, I would think that putting a plate over the upper triangle formed by the support bar would impede visibility to the side? For the lower door bars, it is a really good idea and I plan to add something like that to mine. Especially since the doors are open shells on the R. Did you weld or bolt the panels in?

The challenge car also seems to have a bar that slopes more sharply down and away from the drivers head. I would be much less concerned driving on the street with that setup.

So I'm only duplicating the existing aluminum side panel and making this out of 1/8 steel and then will weld it in, I did this exact same thing for my challenge car.

Here is the position of the challenge bar in relationship to the head

HelmutPicture.jpg

[ZincBoy]

So I'm only duplicating the existing aluminum side panel and making this out of 1/8 steel and then will weld it in, I did this exact same thing for my challenge car.

Here is the position of the challenge bar in relationship to the head

HelmutPicture.jpg

Sounds good. Thanks for the tip. At this point I plan to wait until I get seats in and look at how things sit before taking any more steps down this path.

I don't really want to wear a helmet on the street, but this is a car meant for the track and I can't have everything

To Santiago's point about wheel to wheel racing, that is not in the cards right now but I want to keep the options open. That is why I will not make any irreversible changes until I am further along.