Chassis Material

[oj]

I'm going to build a tank and am used to working in chromemoly, I get the feeling mild steel is better?  That lightweight isn't as much a factor as in drag racing.  I'm of the opinion to build light and add weight where I need it to get down the track. 
I'd like opinions.  What would be a good target weight, P-38 tank stretched to 170ish inches, shorter if possible.
Thanks, Oj

[wobblywalrus]

It seems these vehicles are never finished.  A non-tempermental metal that tolerates alterations seems to work best in the long run.   

[Peter Jack]

I'd be using ERW mild steel for any square or rectangular steel members and DOM for any round tubing members. The chassis rules preclude you from building in much lightness. Landspeed racing is different from any other form of racing you may have been involved with. I think there might be an advantage to building somewhat light for the mile and mile and a half racing but for racing on the salt weight seems to be your friend. Some cars are unbelievably heavy. Weight distribution definitely has an effect.

Pete

[rgdavid]

What specifications de ERW and DOM tubes do you use?.

I would like to try and find the equivelent french and europeen specs,

Thanks, david

[SPARKY]

I use ERW tube and go up to 1.75" & 2.0 which is considerably cheaper than 1 5/8 DOM and is just as strong or stronger s

[Sumner]

An interesting article.....

http://www.pirate4x4.com/tech/billavista/Links/

.... I'm not smart enough to know if the facts/conclusions are all accurate but I felt it was worth the read and bookmarked it,

Sumner

[Stainless1]

Sumner, your article was a no show for me.... can you just post the link please 

[Peter Jack]

I get the same non result Sum and I tried it on three different browsers.

Pete

[Peter Jack]

While the grade never shows on the invoices I receive from the suppliers, Metal Supermarket offers some pretty good articles on materials.

https://www.metalsupermarkets.com/difference-between-erw-dom-and-seamless-tube/

Hope this helps.

Pete

[Glen]

The SCTA gives all the data on tube sizes etc.

[wobblywalrus]

Look at "The Racing Motorcycle:  a Technical Guide for Constructors" by John Bradley, Volumes 1 and 2, for all sorts of advice on the subject.  More of the fabrication part is in Volume 2.  John is from the UK so there is good info about European metals. 

[rgdavid]

Mr.walrus, those are good books and would love to get hold of them but have you seen the prices they go for...mad prices.

Its difficult to buy good spec tubing in france ,  even as  a metalworker i have been refused to be sold quality tube because if your not a reconized chassis or rollcage or airframe maker suppliers you are not aloud to buy. (one large spplier actually closed my acount when i told them what its for ! ) , bloody french liability laws!,
Ill find a way, just need to find material specs.
25cds4 here seems to be an almost equivelent for chrome moly, (4130 ?) and is used here for motercycle frames,
Thanks.david.

[Peter Jack]

DOM and ERW would both be considered mild steels with the ERW approximating SAE 1010/1015 and DOM generally approximating SAE 1020. There is little advantage to using 4130 or chromoly as the rules don't allow thinner wall tubing for that alloy so there is no weight advantage. The disadvantage to using 4130 is that the heavier wall thicknesses should be normalized after welding. Furthermore if a person is going to employ 4130 for race car use it should be 4130N for normalized. Tubing that doesn't come in the normalized condition is unsuitable and probably unsafe for rollcage use.

There is a new material on the market that's just become available in the last few years called Docol R. It seems to have all the advantages and non of the disadvantages of the other materials. It's apparently been approved by most of the major sanctioning bodies for oval track racing and drag racing right up to and including sprint cars and top fuel.

Pete

[tauruck]

Great advice Pete.


Lots of guys are now wondering about their 4130 welding projects not being normalized!!!!.
The guy that the Ferrari F1 team used here in SA for repairs back in the old days told me to stay away from the 4130
unless I could get it stress relieved after welding.

[oj]

Interesting.  I've started reading the rule book and just glanced at the 'cage' section, I thought anything over a certain speed (say 200mph) would have an SFI spec and not shown in the general rules.  You'd have to contact SFI to get a copy of the specifications, it would be in those specs where you would choose either DOM or ChromeMoly.
If there isn't any allowances for stronger tubing then DOM is the way to go, very high quality metal to work with.