Chassis tube sizes, kinda stuck >< -Australia-

[Juggz]

How is everyone going this year, guess its getting close to crunch time for alot of teams.

I hae a question about the rules and how people solve these problems.

The chassis rules stats the minimum size of wall thickness and OD for all the members of a tube chassis.

The problem arises when it says the bulkhead and front roll hoop/ bulkhead supports/ side impact structure, need to be 25x1.6mm, this is a stock size in australia and is manufactured by onesteel. The problem is that the tolerances of this ERW tube are 1.4mm-1.8mm wall thickness.

Now after ordering a length i can certainly vouch for this.

I have emailed the rules questioning email address but i dont expect an email back for another month or so most likely.

We were warned last year with this same situation, that our walls were quite thin in some places (eg 1.5mm instead of the require 1.6) and i dont want this to happen again this year.

The next size up is a 2mm wall thickness and this will add up to 5kg to the frame alone just by using this.

What do other teams do that use a steel tube chassis? How to get around this.

Ive called the engineers at one steel and they said they dont make a product that guarentees the wall thicknesses to match this criteria.

Thankyou for your help

[Juggz]

How is everyone going this year, guess its getting close to crunch time for alot of teams.

I hae a question about the rules and how people solve these problems.

The chassis rules stats the minimum size of wall thickness and OD for all the members of a tube chassis.

The problem arises when it says the bulkhead and front roll hoop/ bulkhead supports/ side impact structure, need to be 25x1.6mm, this is a stock size in australia and is manufactured by onesteel. The problem is that the tolerances of this ERW tube are 1.4mm-1.8mm wall thickness.

Now after ordering a length i can certainly vouch for this.

I have emailed the rules questioning email address but i dont expect an email back for another month or so most likely.

We were warned last year with this same situation, that our walls were quite thin in some places (eg 1.5mm instead of the require 1.6) and i dont want this to happen again this year.

The next size up is a 2mm wall thickness and this will add up to 5kg to the frame alone just by using this.

What do other teams do that use a steel tube chassis? How to get around this.

Ive called the engineers at one steel and they said they dont make a product that guarentees the wall thicknesses to match this criteria.

Thankyou for your help

[oz_olly]

Hey Mitch,

Which uni are you from, UNSW, UTS, Sydney?

I would try performance metals in Sydney. They stock 350 MPa steel tube, I think it is 1020 steel resistance welded then cold drawn to size. Going by the quality of product we have received in the past I would guess the tolerances are quite good.

http://www.performancemetalsau...au/product/mildsteel (http://www.performancemetalsaustralia.com.au/product/mildsteel)

Maybe that will solve your problem. I have used One Steel in the past and would never use it for something like a FSAE car again. I consider it to be for sheds and furniture.

Cheers

Olly

ACME Racing
UNSW@ADFA

[Juggz]

Hey mate thanks for the reply, i was going to try that company tomorrow, the 1.6 they have then is hopefully ok for the car and i hope they have fast delivery because we need it kinda soon http://fsae.com/groupee_common/emoticons/icon_smile.gif

I thought there might be some other teams that had a similar problem, just that steel from one steel is rubbish, 1.4-1.8 is a ridiculous tolerance, i guess thats cause their machines are 15-20 years old.

Also wish the judges or whoever replied quicker to the rules emails http://fsae.com/groupee_common/emoticons/icon_smile.gif

Im from USYD to answer your question

[fixitmattman]

The minimum tube sizes are based around industry standards. You should have no problem running with that catalogue size. You're not going to get much better than that as that's about the best the mill can produce. Unless you call around and find another mill with better machines, but I doubt it as those are pretty standard mill tolerances. Normal variation on the wall sizes produces by the mills here are published at +/-10%, which sounds right up the alley you're getting. I've never had any issue during tech with wall thickness using off the shelf ERW or DOM to those production tolerances. They're mainly concerned that you using at least that minimum size tube to guarantee the integrity of the safety cell.

[Tom W]

We have used Performance Metals for our steel the last few years and haven't had any dramas. If they are struggling for stock you can also try Andrews Race Cars, he generally has everything in stock so that you can go and pick it up, quite often cheaper than Performance Metals.

[shivam wankhede]

Hi, my name is Shivam and I am a 2nd year student at IIT Delhi.

We are currently testing and tuning our car and plan to participate in FSG'14.

We were verifying the thickness of Roll Hoops (ASME 179 and Outer Diameter- 1 inch) for Cost Report (using Ultrasonic thickness gauge). It must be greater than 2.4 mm according to rules.

We observed that their thickness varies from 2.1 mm to 2.4 mm.

During the manufacturing phase, we ordered 2.4 mm tubes and checked their thickness at end cross-section with vernier caliper and it varied from 2.3 mm to 2.4 mm which is within the tolerance of +-10%. But with the Ultrasonic gauge, we noticed that it is as low as 2.1 mm at some locations in the of Roll Hoops. It is due to manufacturing defects on the side of supplier.

Now, should we replace the roll hoop or such a manufacturing error is acceptable?

Do you guys have any other suggestions such that replacing the Roll Hoops can be avoided?

[Pat Clarke]

Shivam,

you should refer this to the FSG tech people as soon as possible. Posting here will not get you an official answer, only opinions.

Tube wall thickness thins around the outside of a bend, but whether this is an acceptable reduction can only be answered by the FSG people.

Go to the FSG website and post your request there in the forum and also email your request to the address you will find on their website.

You need to get moving on this because you cannot just cut the top off the roll hoop and weld a new one on. The rules say the entire hoop must be made from a single length of tube.

If you cannot cut the chassis up to replace the entire roll hoop, then ask for some guidance to an acceptable solution.

Cheers

Pat