[DeTomaso] Wheel Weight

[Tomas Gunnarsson]

Aluminum forming on a lathe:
http://www.youtube.com/watch?v=qO06tQ9ETEY

It's pretty amazing to me how the metal stretches cold like that.

Tomas

----- Original Message ----- 
From: "Thomas Borcich" <tborcich at msn.com>
To: "Pantera REALBIG forum" <detomaso at realbig.com>
Sent: Saturday, November 07, 2009 7:39 PM
Subject: [DeTomaso] Wheel Weight


>I use to watch the three piece wheels being made back in the 80's by a very well known racing wheel manufacturer who 
> I think is still in business today (I won't mention the name). These wheels were the number one wheel used in the 
> Formula Atlantic Series at the time. I saw quite a few of those wheels used on street cars, Porshes, Ferrari's, etc. 
> I think many forget that there is a huge difference in weight of a Formula Atlantic car (1,000-1,500 lbs+/-)  or similar race car 
> vs. a street Porsche, Ferrari, or Pantera (2800-3500 lbs) and the related stress due to that weight. Also, throw in pot holes, 
> curbs, and other assorted road hazards which aren't present on most race tracks, or bolt that wheel on and add a four to 
> eight inch wider gumball tire to pretty much the same wheel manufacturing process and materials bolted to a Pantera and 
> you have may have quadrupled the stresses on that wheel? Sorry I'm not an engineer so I haven't done any 
> stress calculations, I'll leave that to someone on the forum. 
> 
> 
> The centers were a cast piece that was later machined down into a finished piece by an outside vendor. Those centers may have
> 
> been forged, don't recall. I was quite surprised to see how crudely the wheel halve/hoop that bolts to the centers were made. 
> The actual rim halve that is bolted to the centers was made out of flat sheets of aluminum about an eighth inch thick, bolted to a 
> form/buck on a lathe shaped like an inverted bowl. The tool to form that flat piece of aluminum over the buck, was a five to six foot 
> long bar with a forming wheel pressing against the flat piece of aluminum and moved along the base of the lathe. 
> The guy doing the forming and manipulating of that bar was 6'6" tall and over 250 pounds, pulling on that lever with all he had,
> forcing the metal to bend and form to that inverted bowl shape on the lathe!!! I tried to do it and barely moved the metal. Multiple 
> passes had to be made over and over to get the right shape against the buck. That's not very scientific in my book and susceptible to 
> human error. Given the amount of forming done to make the hoop the metal has to be pretty soft to not crack or break during the process.
> I don't recall if the wheel hoops were later sent out for heat treating?
> 
> After seeing how they were made it doesn't surprise me that there were
> lots of failures. I don't think there were ever any back of envelope 
> 
> stress calcs done considering the manufacturing process. Worse, the lathe operator could have put a little too much pressure in one spot 
> 
> when forming a bend in the hoop which made that cross section of the
> wheel thinner and more suseptible to cracking......I saw wheels come 
> 
> back for repair for various reasons, cracks, crashes and leaks...a new
> wheel halve was supplied and bolted to that center and off they went.
> 
> 
> I just went out to my garage and looked at the wheel hoops on my Codington
> clones waiting to go on the Pantera...they have similar rotational 
> forming marks on the pressurized/tire side of the wheel as the racing wheels I mentioned above...so maybe the
> process hasn't changed significantly, although
> I would think that the process is far more mechanized and there is more quality control on a DOT approved wheel.  When I was at Codington's
> warehouse picking up my wheels, there were wheels stacked 15-20 feet high, covering a football field so either they are very well insured or 
> the process is much better, I hope it's the latter.
> 
>  
> Tom
> 
>       
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