The 24 Hours of Lemons Forums → Lemons Tech → Cage question
Ok my question is can you attach the top halo to the vertical halo with plates like this one is done? i will be running down bars from the back side of the plates to the rear of the car so it will be properly triangulated. Just want to make sure im not going to have a problem with this in tech.
I wouldn't. The main hoop is the primary structural member for the whole cage. You want all the forces transferred directly into it, not around it.
I would say "no" but I'm no expert either....typically most race rules state that the main hoop (behind driver) must be one continuous piece with bends not more that a stated angle etc.....
Heres da rules
# 3.1: Rollbar and Structure: Professionally made full roll cage required. A poorly built, improperly mounted, or badly engineered rollcage can keep you from racing: Don't show up with crap! At minimum, cage must include: Full front and rear hoop, appropriately braced to each other along the roofline; two drivers-side door bars (X-design is acceptable); appropriate main-hoop backstays with no bends, located as close to 45 degrees from horizontal as practical; one main-hoop diagonal; appropriate spreader plates and gussets; complete 360-degree welds at all joints. Each major load-bearing member must be formed from its own single, continuous tube. Shoulder-harness bars strongly encouraged, and virtually necessary for proper shoulder-harness mounting in some applications (the attachment point of all shoulder harnesses must be between zero and 15 degrees lower than the seat-entry point); dash bars very strongly encouraged.
o 3.1.1: Rollbar Tubing and Padding: Minimum tubing size for cars weighing under 3000 pounds as raced is 1.50" x .120" or 1.75" x .095". Cars weighing over 3000 pounds as raced must use a minimum tubing size of 1.75" x .120". Properly-bent, racecar-grade and -quality tubing is mandatory: no stretched or crushed bends allowed. DOM mild steel is very strongly recommended over ERW (seamed) tubing.
o 3.1.2: Don't understand any of the above? See where it states "professionally made." You shouldn't be doing this yourself.
o 3.1.3: All roll cage tubing must be padded with high density roll bar padding wherever a driver may contact the tube.
o 3.1.4: All attachment points on the vehicle must be selected and reinforced as necessary so that, in an accident, the cage will not punch through, tear, or grossly distort the attachment point. Spreader plates, backing panels, gussets, and/or other reinforcing elements are generally required to meet this goal. Cages mounted to rusty, thin, under-supported, or otherwise stupid attachment points will flunk tech immediately.
o 3.1.5: Waivers: Previously entered Lemons cars that don't meet the above specs must upgrade their equipment or apply for an individual grandfather waiver before showing up for the race. Be warned: Waivers aren't automatically granted.
the way I see your design is the roof piece is one continuous tubing, except for the rear....where the rules state the front and rear main hoops must be one piece except for where they attach to the floor...make those changes and it looks okay assuming the tubing is correct size-material for the weight of your vehicle
Ok well i did it similar to the pic here. I will post pics later in the week. It is a nascar legal design so it should work for Lemons.
This is LeMon's, not NASCAR. I would say if you did it with plates like shown above, they will fail you at tech. Besides, it looks pretty stupid from an engineering standpoint.
unless it was ubsurdly reinforced, NO. besides its a stupid desin that lowers the main hoop's overall height, do it the conventional way
I dont get how it is a stupid design or how it would be any weaker. It is actually stronger than running it straight to the halo. You are gusseting the only bend in the vertical halo this way which is making it stronger. You also have more surface area welding it to the cage. And you are not losing any head room, you are actually gaining some head room on the left side of your head.
Surface area welded to the cage is a two edged sword...
With tubes that are butted up against each other, the weld is basically there to keep the tubes in place while the tubes press against each other. The weld itself carries very little weight until the tubes have bent enough that the direction of force is no longer along into the adjoining tube. With the set-up you have there - The welds would have to carry a lot of the force of the impact. Welds, generally, are weaker than the material they are connecting - especially butt-welds like the ones from the tubing to the plate.
The use of a Halo Hoop is just fine in the design shown above. I do agree that notching the halo hoop and tying it directly into the main hoop will make for a better load design. You will be welding two tubes of similar strength and thickness and if your weld is properly done it should be stronger. A notched weld has more welding surface than a butt weld. Of course as always IMO. 
*I* wouldn't do it like that, but I've certainly seen MUCH worse. There was a team at the first CMP event that had the A-pillar to main hoop tubes OVERLAPPING each other like a "T". They welded in the tiny corners where the tubes touched. Of course that didn't pass tech and they had to use a sawzall and come-a-long to fix it. The funny was the entire rest of the cage looked like it was built at a NASCAR shop!
I'm not passing judgment on your cage, the quality of your welds, or even its design. That's not my line of work.
I will warn you that this would appear to be an unconventional design when it comes to road racing cages. None of the AutoPower cages seem to be designed like this, none of the SpecMiata cages are designed like this, and I've not seen a SpecE30 cage designed like this either. It may be that your design is perfectly fine, maybe even better than all the other designs out there.
But be prepared that you may get an argument about this when you go through tech, and tech may decide that this design isn't safe because it doesn't look like all the other cages out there. Again, I'm not passing judgment. But I've seen how things go when somebody tries something different and then has to submit it through safety tech, and it's often not pretty.
(FWIW, Page 19 of the Lefthander Chassis catalog shows a cage done in a similar way, at least for the halo bar)
Personally, I'd design it to look and function like all the other safety cages out there and avoid the hassle and the chance that I get to rebuild my cage on the spot to meet whatever the tech inspectors want, especially since the standard cages seem to do a pretty good job in a rollover. You might want to think about getting John at Evil Genius Racing in West Sacramento to take a look at your cage and bless it, he's a NASA Safety Inspector and his blessing might help you down the road if things get ugly at tech.
But this is your ride, and I wish you luck. Just be prepared to make your argument. And don't forget your main hoop diagonal. 
The 24 Hours of Lemons Forums → Lemons Tech → Cage question