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  #1  
Old 01-08-16, 16:22
sprite sprite is offline
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What size ERW square tube for BEC car?

Will be building BEC car using square ERW as much easier than round tube. Can i ask what size tube most cars are made of or what you would use to be strong enough but not over doing it.
Car will be 300-330kg, ZX12R mid-engined, 60's style cigar shaped with no real aero. I would like to use mainly one size , except for roll over bar. What OD and wall thickness is recommended?
Thanks!!!!
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  #2  
Old 01-08-16, 16:55
Lolat492 Lolat492 is offline
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Can I suggest you buy the fantastic book, How to Build Motorcycle Engined Racing Cars by Tony Pashley
The best £20 or so you will ever spend on your project.
Page 36 to 40 details everything you need.

The text says for such a car that you could use 1 inch square, 18 swg or 22 mm square, 1.2 mm thick.
He does use some larger sizes and MOST importantly gives you advice on the roll cage material and thickness.

Remember making suspension arms etc from ersteel is not a good practice.

Demon Tweeks sell the book, bet Amazon do too.

Hope this helps.
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  #3  
Old 02-08-16, 16:12
sprite sprite is offline
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Thanks Lolat492, have that book. Quite good on overall stuff but a bit vague in detail for a non engineer like myself.
I'd read the 1.2mm wall thickness but then also read Allan Staniforths' Terrapin plans calling for 16swg (1.6mm). Wanting to keep as light as possible without compromising safety. But it would seem 1.2mm is acceptable. Thanks.
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Old 02-08-16, 17:49
Lolat492 Lolat492 is offline
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ok, and all books will be slightly 'grey' about these things as so much depends on the design of all the components.

Best perhaps to use the thicker material where the obvious stress points are, suspension, engine, ROPS and seat belt anchors etc and pedal box too!

You might consider starting a build thread on Uphill as there are some really useful people on here with real experience.
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  #5  
Old 02-08-16, 18:05
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tr7v8 tr7v8 is offline
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Another book I could recommend is 750 Racer & another is High Speed Low Cost by Staniforth.
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Old 03-08-16, 13:55
sprite sprite is offline
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Thanks Lola, will start a build thread but just a few questions i need to answer before getting design underway. Have most components and plenty of ideas.
Tr7v8, i also Have Staniforths book and Terrapin plans, though i do remember hearing some Terrapin builders and maybe even Staniforth himself using different (thinner) will thickness than design calls for.
My last question before build thread will be about half shaft shortening. Pashley suggests a method with tube welded over shaft but on may other internet searches people worn of its dangers.
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Old 03-08-16, 17:10
Lolat492 Lolat492 is offline
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I have seen the technique used many times.
All down to the quality of the weld prep and weld penetration for the shaft and then the tube.

Drive shaft steel is not common mild steel.
Would suggest a pro welder does it.

Custom drive shafts are expensive but peace of mind too!

Ask Ian Dayson at Force Racing cars.
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  #8  
Old 06-08-16, 12:45
GR-124 GR-124 is offline
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Hi Sprite,
I'm currently building a chassis. It's a locost, clubman, or call it a Lotus 7 replica race car (it has many names).
I'm using ERW SHS 25x25x1.6mm 350 grade. common here in Australia.
I suggest you get on the ozclubbies forum site. Theres a few builds there and some good help.
Good luck with it
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  #9  
Old 08-08-16, 16:42
sprite sprite is offline
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Thanks GR-124, been trying to get onto oz clubbies for quite some time but may have been closed down a while ago. I remember reading something about in fighting on the site.
Thanks for the other info. What is the cost of the metal you are getting if you don't mind me asking?
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  #10  
Old 10-08-16, 15:59
gixxerthou gixxerthou is offline
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I would simply use 16g 1" box (ERW), as I have used on just about everything BEC and '7' related, no worries.
It can be MIG welded with ease, presents little in the way of HAZ distortion issues. Weight penalty over 18g just never seems worth it to me, especially when you're being pulled out of the wall. Just stay off the burgers to compensate.
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