• Registered: 2010-10-02
  • Posts: 4

Topic: Roll Cage...Help!

I am in need of a scrutinizing eye, especially since I don't have a cage in yet and we will be racing at PBIR!

I am using a crush bender on 1.50" x .120" ERW tubing (using the fill with sand technique) and I think our bends are coming out well, but there is a very slight dimple on the inner apex of the bend.

See the photo here:  http://llracing.weebly.com/cage-photos.html

Will this pass tech assuming everything else is done right?

Also the crush bender is putting small dimples in the tubing, where the tubing contacts the rollers is this ok?  The dimples are on a straight portion of tubing, I feel that this will not compromise the cage's structural integrity...but I am not exactly a structural engineer.

Any help is greatly appreciated!

  • trekkor
  • trekkor
  • Lemons Staff Stalker
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  • From: Napa, Ca
  • Registered: 2009-08-26
  • Posts: 2,124

Re: Roll Cage...Help!

I think it looks pretty good and is likely very safe.

That said, I suspect you will fail tech.
They are looking for pro-built cages that are bent on tube benders for cages.


KT

TH 2009- 40th ~ SP 2010- 13th Class Bad win!! TH 2010- 17th ~TH 2010- 16th  SP 2011- 20th ~ RF 2011- 13th Least Horrible Yank Tank ~ TH 2011- 79th
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  • Mulry
  • Mulry
  • Ayatollah of Rock-n-Rollah
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  • From: Dallas, TX
  • Registered: 2009-05-01
  • Posts: 4,607

Re: Roll Cage...Help!

You should really think about borrowing or buying a good bender (check JD Squared or pro-tools.com), or get a shop that does this work to do it. Nothing -- nothing -- sucks worse than sticking all that time and effort and wasted $$$ into a cage that fails tech and then having to re-do it at the last minute (with the extra expense and hustle involved) just in order to race. And with the PBIR race being a true 24, you're going to want to have some rest going into it. Or put it out there on this board where you're at, you might have a friendly and helpful Lemons neighbor with the tools you need and you don't even know it. Good luck!

Pat Mulry, TARP Racing #67

Mandatory disclaimer: all opinions expressed are mine alone & not those of 24HOL, its mgmt, sponsors, etc.
  • Serj
  • Serj
  • Lemons Staff Stalker
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  • From: Cincinnati, OH
  • Registered: 2009-05-02
  • Posts: 1,601

Re: Roll Cage...Help!

crush-bending tubes is a no-no. do what Mulry sez, invest in a better bender. you don't necessarily have to cough up $800 for one of those Pro-Tools jobs but look for ones that do radius type bending. Crush-bending compromises the integrity of the pipe, even if it's practically imperceptible to the naked eye.

  • From: Davis, Ca
  • Registered: 2009-04-30
  • Posts: 1,843

Re: Roll Cage...Help!

Fail, use a real bender... I will be inspecting at PBIR, and just ask the guys, I'm tough on poorly made cages.   Your cage WILL fail if it is filled and sanded.   


  -John

Gosh, my business card says 'Tech Tyrant'
  • From: Sacramento
  • Registered: 2010-08-09
  • Posts: 1,665

Re: Roll Cage...Help!

John, he's filling the tube with sand before bending - an old trick used to make headers and the like before "mandrel" benders were common... this usually leaves the cross-sectional area very close to the original.

If done right the tube is packed with sand and tamped down - the result can be a bend that is very smooth and often nicer looking than a mandrel bend from a cheap bender.

~also said, the result of filled-bend is that ALL of the tube metal is stretched - the outer radius exceptionally so.
Note that even crush benders stretch the outside radius, but that a std Mandrel bend leaves the inner-most radius mostly unstretched
the reason a crush bender wrinkles the inner radius is that it doesn't stretch at all - it folds in upon itself...

For the problem at hand - I would bend a section of tube and send it to John for inspection. That or fly him out to look in person.

  • Registered: 2010-10-02
  • Posts: 4

Re: Roll Cage...Help!

Thanks to all the speedy replies guys, I managed to track down a friend of a friend of a friend who has a mandrel bender and is willing to help us out, If I can remember to bring the bend to the track I'll have the evil genius take a look at it.

Thanks again!