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Hey, guys...sorry I haven't been posting much...life is very, very busy right now.

Yes, you've all pinned my motivations and plans pretty well. It's just that they keep changing! I was planning on just a roll bar for minimalism with autox-legal and reasonable safety. The cage for racing/time trials is really a very minor part of it all...I might do it, I might not.

Yes, my plan was roll bar for now, maybe a cage later. But then I've been thinking more about safety, particularly on the street. I'd hate to be killed for hitting a dear, hence the front hoop. I'd also hate to be killed by someone t-boning me. Hence the door bars...though I'm dubious that would save me from anything but a TaTa Nano or one of the hundreds of other Locosts cruising Lexington's streets.

So at the moment, I'm pretty comfy with the rig pictured above, pending door bars. I look to the racing req's not so much to race, but as conservative engineering guidance. For example, I'm not too concerned about the lack of top side bars in my design above. Yes, I'm very aware of the tremendous strength and rigidity they would add to the cage, but with what I've got: a) it's still 100x more protection from "likely impacts" than what Colin built, b) it doesn't look so much like a frickin dune buggy, c) I really don't anticipate actually getting my car upside down, and d) I'm not sure that any impact the top side bars would protect me from would actually be all that survivable anyway. Oh yeah...I have a bad back and a bum leg, and on my worst days I wouldn't be able to get in the car!

The curvy bits in the roof seem like a good compromise, with safety weighing in heavily, and a tip of the hat to aesthetics and ease of use. And I can add the top side bars at any time later...given I have more than a few nanoseconds lead time!

I've thought about your comments about the hazard of a cage to an unhelmeted head, Moti. Assuming seat belt usage (a *constant* for me and my passengers), I couldn't get my head close to any of the bars, except maybe the roll hoop vertical. I'm not too worried about the bars getting close to my head...by the time they move that much, all bets are pretty well off anyway.

I like Driven's idea of building the roll bar to bar specs, and the rest to cage specs. It looks like the rules recommend, but not require, consistent tubing throughout. I suspect what they mean is that the bracing tubing should not be *less* than the roll hoop tubing. They all spec only minimum tubing...no max. I'd sure take to task any scrutineer than complained that parts of my tubing were too heavy or that my roll bar had too much bracing!

I have been thinking along the lines of using roll bar-rated tubing (1.5" x 0.120") for the whole cage, which would run about 85 pounds, I think. I'm going to recipher with the lighter, cage-spec tubing, but I suspect it won't change the weight (or cost) notably, and is probably not applicable since I'm not completing the whole cage.

We'll see...Thanks, everyone, for all the discussion...VERY HELPFUL!

-dave

_________________
...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
Visit my [Locost 7 build log]

I'd suggest adding the door bars to the rollbar for street use. Im sure they wont help MUCH in an accident but they actually make getting in and out of the seat easier. Something a little larger and farther away is nice to help hoist yourself up. I do not think it impacts getting in that much and will help prevent you from maybe touching/stepping on the exhaust. Plus I think the car looks better with em.

Okay, I just took the plunge. Three weeks of indecision and playing endlessly with PVC is really stressing me out.

I just ordered 10' of 1.5" x 0.125" DOM for a roll hoop, and 60' of 1.5" x 0.095" for the rest of the cage. I'll be almost $500 poorer when it arrives.

This will yield me a legal roll bar, and a future-potential legal roll cage. For now, I'll put in the funky curve roof pieces, but no door-top bars. I'll probably add one or two door bars now, but frankly not committed yet.

I could have used 1.375" x 0.095" throughout if I was sure the empty weight would be under 1500, but that's crystal-ball stuff for me right now, and I don't mind the extra safety margin. Weight would drop maybe 20 pounds, and probably save $100...both are notable, but not compelling for a non-race car. Plus, depending on how things end up, this may allow extra bends (which would be useful) if that puts me the "next size up" on the weight charts. I probably should have figured this out before ordering, but there comes a time when you have to stop analyzing and start shooting sparks.

Watch for pix in a few days. There's a test-n-tune in Cincy this weekend I'll go to if things go far better than expected. There's another here in Lexington the next weekend that I'm hell-bent on terrorizing.

-dave

_________________
...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
Visit my [Locost 7 build log]

Here's where I'm at now:




More photos and details in my build log:
viewtopic.php?f=35&t=2741&p=62716#p62716

I still plan on adding the curvy roof tubes, but I'm going to run topless for a little while to see how I like it.

-dave

_________________
...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
Visit my [Locost 7 build log]