andyps
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| posted on 1/12/04 at 12:33 AM |
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Side impact
One day soon I hope to be ordering steel to make a chassis - got to make a start at sometime!!
I was wondering about adding a bit of extra strength to the tube which forms an elbow rest on the car with a view to it providing a small amount of
extra side impact protection (I know this is something the seven is never going to be good at, but anything which helps has to be worth having),
My thoughts are either thicker 25mm tube (maybe 3mm wall) or moving to 50 x 25mm tube of the standard thickness. Anyone got any thoughts on these
alternatives, and how much extra strength might it add? In other words, is it worth worrying about?
Andy
An expert is someone who knows more and more about less and less
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scoobyis2cool
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| posted on 1/12/04 at 12:52 AM |
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I think the 50x25 would give a bigger increase in strength (assuming you are mounting it 50mm horizontal and 25mm vertical). However, this will
obviously encroach on the cockpit, which is already a bit on the small side! You may also have problems with body panels over the top rail, depending
on how you are planning on fixing it.
Pete
It's not that I'm lazy, it's that I just don't care...
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Dale
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| posted on 1/12/04 at 01:02 AM |
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I would think that the safest route to go is using one of the roll bars that includes a side protector.
Dale
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erwe
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| posted on 1/12/04 at 05:50 AM |
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As you see on my car (left) I have an extra support from the roll bar to the side of the chassis. I must weld an support from the elbow position to
the underside of the chassis to create a triangle. For a side impact protection the most important thing is that there is extra space to absorb the
crash. Because a seven is a light car it will also slide on an impact. So I think this solutuin is better then bigger tubes for the chassis.
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pgpsmith
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 posted on 1/12/04 at 06:15 AM |
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According to my male sibling, who is a crashworthiness engineer, you want to make certain that you have your arms at your sides during a side impact;
the extra layer of bone and tissue apparently providing a noticeable improvement to your torso's impact resistance(!)
I thought he was kidding when he first mentioned this. I doubt that I would have both the presence of mind and the reactions to snap to attention
just before impact. I agree with Dale that a side impact rollcage seems the way to go. Team Birkinsport do a nice one. The front-ends of most vehicles
(particularly here in SUVland) are above the 7's sill height.
Regards,
Mr. Pete
Live and don't learn, that's us. - Calvin and Hobbes
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David Jenkins
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| posted on 1/12/04 at 08:20 AM |
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This picture shows the sort of thing that would give you some protection on the side - the side bar and the front upright would certainly help.
(I know it's a Westie, but it's a good picture!)
David
 
Rescued attachment car1.jpg
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MikeRJ
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| posted on 1/12/04 at 09:22 AM |
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I'm not normaly one to worry too much over aesthetics, especialy where safety is involved, but I really think the full roll cage ruins the looks
of a seven. It looks like what it is, an afterthought. Has anyone considered building a roll cage into the chassis design?
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Dale
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| posted on 1/12/04 at 12:25 PM |
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I agree and dont like the look of the full cage like that is on the westie and was actually thinking about the car in "ERWE"'s
avatar. If you are building a full racer then the full cage is proably best but I suspect that there is a compromise someware inbetween. I am
trying to build my car as a 30's to late 40's style so bar inplemataion is tricky to not make obvious.
Dale
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Mark Allanson
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| posted on 1/12/04 at 06:33 PM |
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All this side impact resistance is a load of tripe.
If you are hit side on (VERY rare), you biggest worry will be the inertia. if hit from the right hand side, your head will be thrown towards the
outside of the car and into the bonnet of the striking car.
The chances of being hit from the side at 90° is very slim, and the chances of the car being hit between the wheels even less likely.
A bit like wanting a reinforced concrete hood incase of meteor attack
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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JoelP
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| posted on 1/12/04 at 06:44 PM |
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i agree with mark TBH, if the car moves that much faster due to less deformation, your head (neck) is gonna feel even more of a jolt. if you have side
impact bars, you mayaswell have someting to stop your head falling off (much like how a headrest prevents whiplash).
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scoobyis2cool
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| posted on 1/12/04 at 07:58 PM |
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I see your point, but at least side impact protection would help prevent the side of the car caving in and crushing your whole body.
Pete
It's not that I'm lazy, it's that I just don't care...
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andyps
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| posted on 1/12/04 at 08:09 PM |
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I know about the roll cages with the side impact bars and I would certainly consider one if I was getting serious on a track, but for the moment I am
just wondering if there is any benefit of doing something slightly stronger than the standard tube.
I guess my thought for 50x25 tube was to have the 50 vertical to keep the basic dimensions within the original spec.
I do realise changing one chassis tube will not be a complete solution by any means
Andy
An expert is someone who knows more and more about less and less
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Mark Allanson
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| posted on 1/12/04 at 08:12 PM |
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quote:
Originally posted by scoobyis2cool
I see your point, but at least side impact protection would help prevent the side of the car caving in and crushing your whole body.
Pete
If it got to the side of the car caving in stage, your brain would be exiting your skull via your right ear hole. Then you would have no worries!
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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scoobyis2cool
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| posted on 1/12/04 at 09:14 PM |
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quote:
Originally posted by andyps
I guess my thought for 50x25 tube was to have the 50 vertical to keep the basic dimensions within the original spec.
Having the tubing that way round won't make much of a difference to the strength I'm afraid. It will however make a big difference if you
have it the other way round, but that would mean changing the cockpit dimensions
Pete
It's not that I'm lazy, it's that I just don't care...
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David Jenkins
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| posted on 1/12/04 at 09:39 PM |
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My main concern is not side impact so much... it's the risk of being "run over" by 4x4s, trucks, etc. At least a full cage would
(hopefully) result in you being pushed aside rather than flattened.
David
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Rorty
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| posted on 2/12/04 at 01:13 AM |
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quote:
Originally posted by David Jenkins
My main concern is not side impact so much... it's the risk of being "run over" by 4x4s, trucks, etc. At least a full cage would
(hopefully) result in you being pushed aside rather than flattened.
David
You should really consider driving one of the 4x4s or a truck then. 
Adding impact resistance is akin to adding strength to a wishbone (or whatever). All you're doing is shifting the unavoidable inerta and stress
to another area. In this case, probably your head, as has been mentioned.
If you choose to drive a motorised skateboard, then you'll have to assess and accept the risks. Bikers do it all the time.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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Dale
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| posted on 2/12/04 at 01:44 AM |
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I normally are not over easily swayed from an opion- as per in the side impact but i really thought about the comment of the head being crushed by the
time the side would come in and must admit i beleave its pretty much correct. So with a look at my chassis it becomes fairly obvious that a dirct
hit at the drivers mid section has to go through the wheel to get to me and should spin the car to take some of the impact. I used a 4 inch 12 awg
plate all the way across the shock mounts from one side the other mounted on a 1x1 on each side underneith it ( just to give me the option of cobra
style hoops), I think that brace across thetop should give alot of strength to cause the whole car to move---all beit with a very solid hit I
probably dont have to worry too much about it. I dont see a whole lot of viable help from a side impact bar- except in racing where I assume its
main use it to keep open front wheels or rear from haning up on the rear wheels or our cars.
Dale
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David Jenkins
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| posted on 2/12/04 at 07:35 AM |
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quote:
Originally posted by Rorty
If you choose to drive a motorised skateboard, then you'll have to assess and accept the risks. Bikers do it all the time.
I used to be a serious biker - 400 miles a week, usually - but eventually decided that staying intact and alive was more fun.
In spite of what I've said previously, you'll see on my website that I don't have a full cage - I don't even have a
windscreen! However, I do have a sturdy roll bar in case I turn the car over. As you suggest, I assessed the risks and made my choices.
My Locost is an excellent motorbike alternative and a lot safer - but I still use my motorbike techniques for keeping out of the way of the plonkers
in their great big penis substitutes...
cheers,
David
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scoobyis2cool
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| posted on 2/12/04 at 10:17 AM |
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How about strengthening the chassis to protect your body and wearing a helmet to protect your head? That way you can look after your whole body, with
the added advantage of keeping the wind/bugs out of your face!
Pete
It's not that I'm lazy, it's that I just don't care...
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David Jenkins
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| posted on 2/12/04 at 10:59 AM |
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I do wear a helmet! I find that it enhances the "pretend motorbike experience"... oh, and it means that I can actually see where I'm
going, hear myself think, allows me to breathe, and so on...
David
[Edited on 2/12/04 by David Jenkins]
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silex
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| posted on 2/12/04 at 12:44 PM |
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If you look at your seating position in locost, side impact bars aint gonna help that much. You back is practically on the rear bulkhead of the
chassis which will take more impact than side bars. Also to your side is the rear wheel, connected to an axle - pretty strong in a side impact no
matter what the design, not to mention the air bag (tyre).
If some thing did come through the gap between front and rear wheels, they will be aiming more at your legs than torso. I don't think side
impact bars are going to make alot of difference between life and death in a locost for normal road use.
Murphy's 2 laws
1. If it can go wrong it will
2. In case of emergency - refer to rule 1.
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krlthms
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| posted on 2/12/04 at 05:24 PM |
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I, unfortunately, have never driven a seven or a locost. But I have driven and did a bit if hill climbing in a TR3A about 25 years ago, which appears
to have the same saftey issues, in that you sit ON the car rather than IN it, and you adopt the "elbow out" sitting/driveing position.
I am intending to build a locost, which will be a lot faster and flimisier than the TR and, being a middle aged parent, I am supposed to think more
about saftey. So here is what I think:
1. A locost is (should be) safer than a bike, but adopting defensive bike style driving technique would help more. So, I would drive with the lights
on and try to make sure I am not driving in anyone's blind spot. Also, I would not allow anyone to "tailgate".
2. I am not sure that having the front suspension as intentially weak is a good idea because once you lose it you lose your ability to steer or brake
which would increase vulnaribility. Also, IIRC Aryton Senna (the Jim Morrison/Hendrix of car racing) was actullay killed by a wheel detaching and
hitting him on the head, so there is also this possibility to consider.
3. I like this sevenesque design
http://www.rcb7.de/galerie-2/index.php
I don't know if it is an optical illusion, a lower seating position (?), side door, or higher chassis side members, but it appears the driver is
enclosed by the car to neck level. I think something like this design with some built in strength (e.g., side door made of composite sandwich and
overlapping the chassis members), should provide some extra saftey. IIRC aftery Aryton's death F1 cars were modified by raising the sides of
the cockpit to protect the driver's head.
4. I agree that the roll cage detracts from beauty and sense of lightness of a locost. I assume that for racing the design is fixed by regulations
and you have to live with it. For road use, could a strengthened windscreen frame be used as a front hoop (I think it is so in certain TVRs). Also,
would it be possible to use tubing of a different profile (oval?) in making the roll cage? This may improve the looks, as would painting/plating it a
light color.
5. Side whiplash or inertia would likely cause severe spine/head injuries in a Locost because these cars are capable of generating large lateral Gs.
I have come across the HANS (Head and Neck Saftey) device, which supposedly works well, but is priceyand looks uncool:
http://www.guyons.com/hans.html
Maybe someone in this forum could design a low-cost version?
Cheers
krlthms
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Volvorsport
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| posted on 2/12/04 at 05:44 PM |
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well , having studied side impact and looked over a 1000 volvos , both chassis rails are too high /low to offer any penetration resistance , if you
compare the height of a side impact door bar , and the locost youll see there would have to be some large alterations to the design . You could add
some 50mm tube so that the depth of the tube has more bending resistance , all around the cockpit , through the dash and back round the the back of
the seats .
I intend on mine to have a foam filled sides that wil offer some extra security in absorbing energy , as for being runover by an SUV , if it hits you
in the right place , youll be eating 16 inch rubber for a while , for which case a full roll cage will be the nearest /best answer you could provide
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Mark Allanson
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| posted on 2/12/04 at 06:00 PM |
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look in my photo archive under safety modifications
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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Volvorsport
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| posted on 2/12/04 at 06:16 PM |
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you are a one mark!!!
agreed tho that safety in a locost cannot be taken as a priority due to the nature of the cars .
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