[alfa] Re: roll barred

[SHartDP@xxxxxxx]

Being in the off road racing scene I see plenty of people who are bashing standard mild.  It does have it's place though.  I do know that DOM is about 20% stronger then regular mild for a same size comparason - eg..120 wall 1.5" and chromoly is significantly stronger than DOM.  DOM is similar to regualr mild but has a higher carbon content (1018 and 1020).  It is also stronger due to the lack of seam.  Chromoly is also seamless and VERY strong making it the choice of many racers.  The main people run it though is becasue you get the same strength out of a .095 wall 1.5" chromo tube as you do from a .120 1.5" DOM tube.  This means you can have the same strenght with less weight.  BUT chromoly becomes more brittle if it is not normalized or heat treaded after being welded. This will lead to stress cracks over the life of the car.  (I swear I am getting to the alfa content)  I chose to run .120 wall 1.75" DOM in my truck because I want to have the truck for a long time, and do not want to be stuck "chasing cracks" in the cage all the time.  In the Alfa however (told you it was in here somewhere) I am kind of stuck on what to run.  I am building a 6 point cage for what will be my semi daily driver and play toy.  I'm not sure I will do any sanctioned racing other then a club fun day so I don't think I have any set rules to abide by (not that my design would fail any tech inspection).  Anyways - do most people run mild or DOM cages at .095 wall or are they thicker?  .095 wall is allowed for main cage in chromoly only in SCORE rules so most guys run .120.  Is .120 overkill or too heavy for the poor little alfa?

Steve Hartman
Balboa Island, CA
72 GTV - project street car
71 GTV Euro - needs to go
89 Ford Ranger - tought me too much about metal
89 Honda Civic SI - Ricey daily driver - eeewww  
In a message dated 10/3/2003 7:50:18 PM Eastern Daylight Time, owner-alfa-digest@domain.elided writes:

> > One question I have though is why is ERW banned in SCCA now?  Has there
> > been a history of people using hot rolled instead of cold rolled steel,
> > or possibly bending the tube with the seam on the outside of the bend
> > (making the seam prone to tearing)? 
> 
> mostly the latter, i think. Kurt Weiss (an engineer and cage builder who is
> now chairman of the SCCA Competition Board) also feels that there are
> significant strength advantages to DOM in general. i've not talked to him
> about the exact reason for bagging ERW, but i'm sure that the case was
> there for the ban (incidentally, Kurt built the cage in my currently stored
> SCCA ITB Alfetta Sedan, to put some Alfa content back into this thread.
> it's made from 1.75" 0.095 wall DOM, not suprisingly given 
> that Kurt built
> it.)
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