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Learning how to build Lotus Seven replicas...together!
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PostPosted: June 11, 2007, 2:23 am 
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Looks nice.....I think that if you can get close to these pictures with a laid back window and smoother lines you should be doing well.

I really like the pods it is the first practical attempt I have seen in real world application to address side impact of a lotus....better aerodynamics is another benefit. The nose cone could be angled (similar to the radiator and a sloped wind screen).


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File comment: Basic view simple lines
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File comment: With a wing for added down draft
con3.jpg.jpeg
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PostPosted: June 11, 2007, 10:19 am 
mr.peabody.d wrote:
I really like the pods it is the first practical attempt I have seen in real world application to address side impact of a lotus


I like the side pods, but they would add almost nothing to side impact safety. They would literally crumpled like soda cans on a side impact and absorb very little energy doing it. If you wanted to add any significant side impact energy absorption you would have to add a piece of channel inside the skin of the pods and beef up the bulkheads.


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PostPosted: June 11, 2007, 1:29 pm 
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Maybe fill them with structural foam to absorb some of the impact energy. Of course add the side impact beam too. Then it becomes too heavy to be practical.

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PostPosted: June 11, 2007, 1:52 pm 
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Said Mr. P:
>I think that if you can get close to these pictures with a laid back window and smoother lines you should be doing well.

Man, if I could get close to those pictures I'd be doing <great>, but even my modest targets (cheap, duplicable at home, etc) call for considerable effort. So I won't be changing horses any time soon. If there was a body available like the one in those drawings, though, I'd buy one...if I could afford it.

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> ...they would add almost nothing to side impact safety....

The main benefits of the side pods are torsional rigidity and aerodynamic drag reduction, but the side impact safety is not to be sneezed at. As some of you know, Kinetic intends to enter a 2k7-based car in the AXP alternative class, and (unless the Alternative Class requirements get relaxed so much it drops from the innovaters-and-eccentrics class to the fruitcakes-and-mystics class) crash protection is part of the package. But yeah, channel in the pods, more bulkheads...we can dial in whatever level of side impact protection we like, without any significant changes to the structure. I haven't done any impact tests yet, but I'm working with hat sections as stiffeners (held in place with a 3M automotive structural tape) because they seem to do the job better than channel per pound (and per dollar as well) and 'waffled' bulkheads and it appears we can meet federal standards for cockpit intrusion for less than half the weight of a Miata door.

But as it sits now, "literally crumple like a soda can" is surely a step in the right direction, impact-wise. Per pound of soda can, many foot pounds of work are absorbed during crumpling. Compared to, say, a rib cage, this pontoon is already pretty sturdy.

Anyway, back to work on the fenders.


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File comment: I painted the pattern blue last night; when the glossy spot on top dries, it'll get a light wet sanding with 400 grit.
41BluePaint.jpg
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PostPosted: June 11, 2007, 2:10 pm 
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Hi all, the sides that mr.peabody.d put in his drawing- very nice by the way. are almost exactly what I am trying to do. Structural foam would help but is not going to last as the exhaust is going to be to close. Honeycone or hat sections as Jack suggested probably would. Better yet is that a side inpact bar incorporated into the roll bar could be run down the side in the pod and not even show.
Dale


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PostPosted: June 11, 2007, 8:08 pm 
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I don't want to hijack my own thread, if this discussion carries on maybe we should start an <Impact protection> thread--I must admit it's an interesting subject.
dale wrote:
Better yet is that a side inpact bar incorporated into the roll bar could be run down the side in the pod and not even show.
Dale

Show us a sketch, Dale, I'm not getting it.

I agree with you re structural foam and the temp changes it would experience in the exhaust-side pod.

jamnz6, there's a diminishing returns thing goin' on there for sure, but trading off <some> weight for <some> side protection may be worth doing. Nothing we can do will protect the driver from a Hummer hitting the left side of the car at 30mph, unless we're willing to change the personality of the car significantly. That's not a dealbreaker to me; the same is true of every bike on the road. But a standard Locost is probably not survivable if the Hummer t-bones it at 15mph either--I think a Hummer is high enough and heavy enough it'll get in the cockpit with you at 15. But at 5mph, there's a good chance a side impact from a Hummer (or Suburban or the neighbor kid's Toyota Tundra with the lift kit) would merely push you into the passenger and terrify you.

Point is, someplace between 5 and 15mph, it would be good to have pontoons. "Almost nothing" is, after all, something.

BTW, the pontoons in steel weigh a smidgen less than 15 pounds per as is.

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PostPosted: June 12, 2007, 12:46 am 
I was a professional Collision Analyst & Reconstructionist for the past few <decades>, and I totally agree with you, Jack, about the "soda cans" analogy. There is a large amount of kinetic energy in any collision, and it has to go somewhere. If you could get the vehicle's body structure to deform, and thereby absorb all of that energy, there would be none left transmitted to the occupants, and therefor no injuries would occur. Of course, that will never happen - in the real world, vehicles change direction as a result of collisions, and the sudden changes in vectors can transmit hundreds of G's to occupants, over very short times (i.e., milliseconds!). But it is possible to mitigate this to a large extent using sections designed to crumple in a collision, and use up substantial amounts of the kinetic energy.

I'm thinking that the side pods in your design could work extremely well - if I were to recommend a side-impact intrusion beam, it would be nearest the occupants (NOT on the outermost portions of the structure), and inside of the energy-absorbing material. In other words...absorb as much as you can with the outer structure, then protect the occupants with what the last-ditch protection (the side beams). It's too bad that carbon-fiber is so expensive...imagine the technology in those Indy car (and Formula 1) nose cones, incorporated into your side pods. Bring on the Hummers then! (well, not by choice of course ) :roll:


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PostPosted: June 15, 2007, 10:29 pm 
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Well, not to be a downer, but wouldnt a hummer just go over the pod?


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PostPosted: June 16, 2007, 12:57 am 
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Mandurath wrote:
Well, not to be a downer, but wouldnt a hummer just go over the pod?
Depends on the speed. A book frame is 13" high, add 5" for typical street ground clearance...Hummers have a fair bit of hardware under the nose; they don't have 18" of ground clearance...and with the pontoons, that stuff will make contact with the car 10" sooner than it would without the pontoons. If one can reduce the intrusion by 10 inches, well, my rib cage is roughly 14" wide, and if I get squished to 4" wide I'll be dead.

If you do get centerpunched by a car/truck/SUV it'll probably have the brakes locked up and the driver will be at least <trying> not to hit you. When you hear traffic accidents, it's normally screechCRASH, not CRASH. Impact speeds cover a wide range, and somewhere in that wide range, there are situations where pontoons will keep you alive if you are hit in the side. I'm still not going to figure-8 race it unless all the other vehicles are Locosts too.

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PostPosted: June 16, 2007, 1:44 am 
If you get T boned in a A LISS you will probably be having a bad day


Last edited by locostv8 on June 16, 2007, 2:36 pm, edited 2 times in total.

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PostPosted: June 16, 2007, 9:12 am 
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I am guessing that depeding on speed, if you get tboned in a locost type car, you are probably screwed depending on the speed.


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PostPosted: June 16, 2007, 1:18 pm 
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An insurance agent told me the vast majority of car accidents happen at low speed, and due to the nature of our cars, even low speed side impact accidents are a significant risk to us if we're the impactee. So maybe a bit of side structure will come in handy some day.

Still, it's a fringe benefit, I wouldn't be doing this if I didn't think it was worth the trouble from the standpoints of aerodynamics and chassis torsional rigidity. As a biker, I've been saved some injury because I had a fairing, but I put the fairing on to make it go faster, not to protect my leg. The secret to locost safety (as it is with bike safety) is pay close attention to what you're doing, and don't trust your life to the skill or altruism of other drivers.

PS--locostv8, what's an ASIS?

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PostPosted: June 16, 2007, 2:23 pm 
My attitude when I rode a bike as only transportation. ride as though everyone on the road is purpously trying to run over you and you will ba atleast half right. My plan is to treat the LC the same. Noisy visible and duck.


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PostPosted: June 16, 2007, 2:49 pm 
JackMcCornack wrote:
An insurance agent told me the vast majority of car accidents happen at low speed, and due to the nature of our cars, even low speed side impact accidents are a significant risk to us if we're the impactee. So maybe a bit of side structure will come in handy some day....


part of the reason for the big x huge tyres& wheels, something to hit first before impacting the side of the car/me. A cage with side bars certianly wouldn't hurt.


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PostPosted: June 17, 2007, 5:33 pm 
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In response to the side impact bar incorporated into the roll bar here is a couple of pics I took from the locostbuilders.co.uk site. I hope the builder does not mind.
Its neatly done and does not show to bad. I think the side bar could be incorportated into the side pod to some degree. I like the idea of a petty bar but would want it removable.
Dale


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