Jumpy Guy
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| posted on 27/7/04 at 09:03 AM |
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removable side panels?
How much do the side panels contribute to the structural rigidity of the car?
im thinking of making my front side panels fixed by rivnut, rather than rivets
mainly because I want to take the car apart during the winter to re-paint and powder coat, and dont want to have to drill out too many rivets!
but, it should give me slightly better engine access.
so, do-able, or not?
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zilspeed
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| posted on 27/7/04 at 09:47 AM |
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I like to think of the central tub of the car as having a stressed skins. This is entirely empirical thinking, so please feel free to ignore me.
The sides of the tub have nowhere near enough members in them for my liking and I think this is why many builders bond the panel on as well. This
causes the panel to be a stressed skin.
I imagine that rivnuts would always have the capacity to work ever so slightly loose, thus allowing elongation and ovalling of the holes in the panel.
At that point, the panel is contributing precisely zero to the structural qualities of the the car.
Hopefully, a boffin will be along in a moment to provide scientific data of the difference in torsional rigidity between an unpanelled chassis and a
bonded panelled chassis.
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mangogrooveworkshop
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| posted on 27/7/04 at 10:06 AM |
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Zil
Chapmans original design had tube that was wafer thin. He didnt have the power we have availible today so his way of thinking was one part two uses.
The modern road cars such as indy and westie have fibre glass panel that are more a function than structure. The ali does stiffen up the chassis if
bonded and rivited correctly. How ever the chassis is strong enough to do the job its built for with out these panels. Remember the originals had no
center tunnel tubes! These were added later. The seat belt mounts were bolted through the ali on the inboard sides as well as the gear box mount.
So the jurys out. As you say some ss engineer will tell us the maths.
Ive got a report on all the chassis somewhere and the DSK was the heavy one with 180 brake (turbo) Catervan have had several changes as well down at
the rear suspention trailing arms as well as the top of the front suspention bay.
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stephen_gusterson
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| posted on 27/7/04 at 10:06 AM |
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why not do what I did?
instead of using 19mm tubing as diagonals at the sides, use inch tube, and make it X shaped. I did this for the engine bay sides too.....
atb
steve
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stephen_gusterson
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| posted on 27/7/04 at 10:09 AM |
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quote:
Originally posted by mangogrooveworkshop
Zil
Chapmans original design had tube that was wafer thin.
chapmans cars were never that strong - many accidents were caused to his cars in F1 by things breaking.
I read a book on the original seven - the rear axles used to break as there were just two swing arms, which allowed the axle to pivot under torque.
what might have been ok in early sevens may not have been that great in retrospect, and as you say, not for cars with engines this side of the
60's
just my opinion....
atb
steve
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Bob C
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| posted on 27/7/04 at 11:23 AM |
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I have a distant memory of an original seven using the oil drain hole of the diff to mount a lower A frame for axle lateral location...
I think his theory was if the customer died he couldn't sue.....
cheers
Bob
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stephen_gusterson
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| posted on 27/7/04 at 11:51 AM |
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the mod I saw wasnt to use two extra arms (4 in total) like the locost does.
It kept the one each side approach, and welded a vertical strip of steel along the top of the axle.
The axle was twisting and cracking, so this 'mod' was to prevent the twist - rather than adding 10lbs of better suspension to the car.
I once read that chapmans race car suspension was a masterpiece, as one bolt held three parts in place. Of course, if one bolt failed,,,,,,, 3 bits
fell apart.
how much does a bolt weigh in the scheme of things - esp as F1 cars hold parts on with m6 m8 bolts....
atb
steve
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zilspeed
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| posted on 27/7/04 at 04:25 PM |
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quote:
Originally posted by stephen_gusterson
the mod I saw wasnt to use two extra arms (4 in total) like the locost does.
It kept the one each side approach, and welded a vertical strip of steel along the top of the axle.
The axle was twisting and cracking, so this 'mod' was to prevent the twist - rather than adding 10lbs of better suspension to the car.
I once read that chapmans race car suspension was a masterpiece, as one bolt held three parts in place. Of course, if one bolt failed,,,,,,, 3 bits
fell apart.
how much does a bolt weigh in the scheme of things - esp as F1 cars hold parts on with m6 m8 bolts....
atb
steve
Exactly
In a live axled caterham, the trailing arms mount to the bottom of the axle and the A frame mounts on the top of the diff housing. Great for
cheapness, but unfortunately causes a disastrous load path along the axle tubes. Hence the welded on brace.
This is mentioned in Legend of the Lotus Seven by Dennis Ortenburger.
Chapman's philsophy was that if the car fell apart on the slowing down lap, then every part had been just strong enough.
I have a wife, a mortgage and a child. I want a bit more structural integrity than that.
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zetec
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| posted on 27/7/04 at 04:30 PM |
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I have fitted my offside panel with sikoflex as I don't think it will have to come off unless damaged then I'll hack it off and bin it. My
nearside panel is removable as it's the only way to get the exhaust manifold of the car without moving the engine. The rear wings hold the rear
of the side panel in 3 places with bolts, the scuttle add another 3 fixings and the nose cone 2 more. The underside uses those hex head self tapers
which if fitted correct give a very secure fixing.
So far the panel has stayed on just fine, the chassis has not twisted and all four wheels seem to be touching the tarmac most of the time.
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stressy
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| posted on 27/7/04 at 09:18 PM |
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w.r.t caterham live axles i think youll find the a arm is mounted to the bottom corners of the chassis and the bottom centreline of the diff. the
trailing arms were curved over the top of the axle. ??
On the side panels topic everybody has a different view. My thoughts are as follows:
in order to stress the panels you require them to have sufficent comparative stiffness to pick up load. a triangulated box section construction in
steel or a plane sheet of 1.2mm soft alloy. no prizes for guessing which is gonna be stiffer by a margin....
the panel will be loaded in shear, introduced by the deflection of their outer boundaries, i.e. the chassis. therefore ignoring the stiffness of the
panel itself you must have the edges sufficiently fixed to aid loading transfer. this means as best as possible a continuos joint . ideal of this is a
weld which is clearly not an option.
In orderto gain substaial advantage from the side panels you would eeally need to do the following:
1) use a good grade of heat treated al.al, 7000series maybe
2)use a bonding medium not just any old epoxy
3) chemical clean prior to bonding
4)use solid rivits not pos at a tight pitch
I weighed up the effect of the extra stiffness / strength at the fornt versus the practicality of front removable panels for engine access and went
for bolted panels.
as i sat these are just my thoughts on the topic but i hope they be helpful.
Cheers
Chris
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jcduroc
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| posted on 19/8/04 at 10:25 AM |
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quote:
Originally posted by mangogrooveworkshop
Can anyone spy on my ISP and runnig software?
JCM
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phelpsa
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| posted on 19/8/04 at 10:45 AM |
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We can only see our own. If someone else has the right software it is easy to find out, thats what hackers do.
Adam
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blueshift
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| posted on 19/8/04 at 12:40 PM |
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rather a vague and handwaving answer.
the banner is a lot more alarming than it seems. all it is doing is working on two bits of information it has, your IP address and your reported
browser version and platform.
the image has been included by someone's signature, so your web browser connects to the web server the image is on and requests it (this is how
you get all images loading in your web browser). When you connect to anything over the internet you reveal your IP address: you have to, or the other
end doesn't know where to send things back to. Perfectly normal. Then the webserver does a reverse DNS lookup on the address, again perfectly
normal.. DNS stands for Domain Name System, it's the mechanism that turns names like www.locostbuilders.co.uk into an IP address (217.204.9.252)
so your computer can connect to it. using the same system you can turn an address back into a name, that's all this "clever banner
program" is doing, chopping off the beginning of it, and hoping that the end part is the name of your ISP. for most people that works, for me it
comes up saying "your ISP is chebs.net" because I have fiddled my DNS to be quite silly.
As for the browser version and platform, nothing magical about that. your browser always sends those to a webserver with every request, it lets
webservers serve you the right content for your browser and platform.
In conclusion: don't be afraid, it's not doing anything sinister, it's just handwaving to scare people who don't understand
what it's doing.
On a related note, you can now laugh whenever you see a popup that says "warning! your computer is currently broadcasting your IP
address!" - if it didn't, you wouldn't be able to use the Internet at all.
Hope this helps.
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jcduroc
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| posted on 21/8/04 at 09:02 PM |
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Thanks for the info anyway(?!)
JCM
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