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Author: Subject: Chassis tubing wall thickness?
alistairolsen

posted on 16/7/09 at 09:46 AM Reply With Quote
Chassis tubing wall thickness?

I was looking at some petric tube which is 25x25x1.5 but thought this might be a touch thin as the book used inch by inch by 16swg which is 1.6mm.

What tube thicknesses did everyone use?

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handyandy

posted on 16/7/09 at 09:56 AM Reply With Quote
i,m building a Haynes Roadster & the chassis is constructed from the 25x25x1.5, its fine, it really does become a strong frame once welded together.

andy

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speedyxjs

posted on 16/7/09 at 10:55 AM Reply With Quote
I used 2mm 25 x 25 but i need a stiffer chassis to handle the power





How long can i resist the temptation to drop a V8 in?

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clbarclay

posted on 16/7/09 at 11:11 AM Reply With Quote
changing the wall thickness by 0.1mm shouldn't weaken the chassis to much. IIRC there were some people on here building chassis with 18swg or 1.2mm wall thickness steel.

If you want to make the chassis stronger, a few people analysed the chassis and concluded where adding more steel of changing the design would be beneficial and posted it on here before.

I've just found that searching through all the posts made by the memeber "cymtriks" brings up a lot of technical posts on chassis design, including his own FEA based recomendations from 2002.

[Edited on 16/7/09 by clbarclay]






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alistairolsen

posted on 16/7/09 at 11:14 AM Reply With Quote
Ill be doing everything that cymtriks recommended, including deepening the lower chassis rails.

What I want to know is whether suspension mounts welded to 1.5mm wall are strong enough, or whether to accept the weight penalty and go for 2mm or something.

My gut instinct is that thin is fine, and if necessary put spreader plates behind the mounting points.

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JoelP

posted on 16/7/09 at 12:10 PM Reply With Quote
if you are paranoid about the suspension mounts, add gussets or braces in those areas. 1.5mm is fine for most engines and uses.





Beware! Bourettes is binfectious.

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deezee

posted on 16/7/09 at 01:50 PM Reply With Quote
quote:
Originally posted by alistairolsen
.......accept the weight penalty and go for 2mm.....


The additional weight, per metre of 2mm over 1.6mm is 260 grams. So if you use 50 metres in your chassis, it will only weigh 13kgs more. Not a great deal and easily recoverable else where on the car.

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alistairolsen

posted on 16/7/09 at 01:58 PM Reply With Quote
on the basis of half that, tell me where I can save 6kg later in the build for no money whatsoever?
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Staple balls

posted on 16/7/09 at 01:59 PM Reply With Quote
quote:
Originally posted by alistairolsen
on the basis of half that, tell me where I can save 6kg later in the build for no money whatsoever?


Eat a dodgy kebab, that should do it.






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alistairolsen

posted on 16/7/09 at 02:05 PM Reply With Quote
at 64kg dripping wet I cant see me getting myself much lighter.

cencessions to weight saving:

no internal panelling
triton seats
wilwood calipers
lightweight wheels
alloy blocked engine
alloy panelling


Anywhere I try and save weight is going to cost, so I dont want to add 6-13kg for no reason. If I go 2mm or 2.5mm it will be because I have to, not because I CBA to find the proper steel.

So, once again.... will 1.5mm be ok, or will I end up building a crap floppy chassis that ends up cracking and tearing out the suspension points?

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ironside

posted on 16/7/09 at 05:03 PM Reply With Quote
Have you decided what you're going to put in it yet?
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Mark Allanson

posted on 16/7/09 at 06:21 PM Reply With Quote
Many stockholders if asked for 25x25x1.5 will say certainly sir and give you 1"x1"x16g as there is no discernible difference. Manufacturers never did retool to produce metric in this size.

Be aware when making you car very light that it is the ratio between sprung and unsprung weight that makes a hell of a difference. Too light makes a very crashy bangy car only suitable for red eyed youngsters, and a real pain is the @rse for anyone the wrong side of 40!





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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alistairolsen

posted on 16/7/09 at 09:06 PM Reply With Quote
its getting a volvo t5 engine and the nice side of 300bhp.

Im aware of that, hence trying to save weight in the unsprung with nice uprights and brakes etc.

interesting that they didnt retool, probably wont make any difference then

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procomp

posted on 17/7/09 at 06:52 AM Reply With Quote
Hi

The other thing with tubing these days is that they are now so clever whith the tolerances that they supply the majority of tubing at minimum tolerance regardless. This means that if you order 16G you will get 17.5G So order 14G if you want 15.5G. Although if your stockholder can supply certified tubing with certification you should be able to get genuine sizes. It's why there have been so many failures of chassis and components over the last 5 years or so.

Cheers Matt






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cymtriks

posted on 22/8/09 at 09:40 PM Reply With Quote
quote:
Originally posted by procomp
...It's why there have been so many failures of chassis and components over the last 5 years or so.


A search for "chassis failure" and "tube failure" comes up with nothing.

Are there any reports on here? Is a certain tube prone to failure?

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