Topic: question on 3.1.1

sent my rollcage guy a copy of the rules to make sure our cage was up to spec. he said he was worried about a line in 3.1.1 "no stretched or crushed bends allowed". so i went over there and took a picture of what his equipment does. this look kosher?

http://i440.photobucket.com/albums/qq127/Mechafishy/Other/IMGP0097-1.jpg

Holton St Eurotrash
84ish porsche 924s
- ct 10 ate bolt, heroic fix.
- nh 11 1st to cover track in oil.

2 (edited by TeamDFL 2009-06-24 05:40 PM)

Re: question on 3.1.1

I'm not a tech guy so my opinion counts for jack.  No warranty expressed or implied.   I did not stay at a Holiday Inn last night.  Blah, blah...

It sort of looks like you used a rotary draw bender from the marks on the outside of the bend but there seems to be a lot more crush on the inside than I would expect.  If it were my car, I would run that at a Lemons event but I would also do some testing with my die set to figure out what is going on.

What are the tubing, bender, and die specs?  What did you use for lube?  Did you mark the tube to line it up with the die?  Did the tube slip during the bend?  It sort of looks like the wall thickness was a bit thin for the center line radius of the die.

Here is a pic of the inside of one of the bends in the main hoop in our car.

http://teamdfl.com/Lemons/diagonal3.jpg


EDIT:  Are you going to bring the Bobcat to the event to have your own little Mechafishy's curse crush-o-rama?

http://www.ducttapemotorsports.com/
http://www.teamdfl.com
"I can see it now, a pile of nickels and all the glory of being a real race car driver."
Prepping the Red wReck for the 24 Hours of Lemons

Re: question on 3.1.1

I would agree that is right on the edge of acceptable, and that a rotary draw bender should do better than that.  Check his dies for out of round and/or wrong size and/or cheap as hell. 

Best bet is to take a bunch of photos and send it to Jay and/or Nick.  We had the same questions about our bends and  they told us what's what.

Re: question on 3.1.1

That does look like a more-than-ideal amount of crush. Our metal-fab neighbor tells us that that much crush at a bend typically means one of two things:

1. The buckles/cradles on the inside of the bender are placed too close together (assuming they are adjustable). Try spacing them out and running another piece of test pipe and see if it makes a difference.

2. The pipe itself is too thin. If you used muffler pipe or other thinwall tubing to run this test, you might get different results with cage-spec tubing.

Finally, your test piece was bent at a slightly acute angle (which you ideally shouldn't have in your hoop design). That might also create extra crush.

Jay has an Alfa with an Autopower bar parked here in his living room, and we use that as the benchmark for the ideal amount of crush. It's barely visible, especially in this crappy-ass picture:

http://farm4.static.flickr.com/3279/3659952061_2cd613d943_b.jpg

5 (edited by Mechafishy 2009-06-29 06:18 AM)

Re: question on 3.1.1

so... would an auto power bolt-in be cool if we weld the joints together?

EDIT: nevermind. shouldda done the search before i asked the question. my bad.

Holton St Eurotrash
84ish porsche 924s
- ct 10 ate bolt, heroic fix.
- nh 11 1st to cover track in oil.

6 (edited by Junkyard Dog 2009-06-29 07:29 PM)

Re: question on 3.1.1

I'd say that first pic wasn't a bend from a rotary draw bender. That looks more like the kind of bend that would be made by a pipe bender. Like this one:

http://www.global-b2b-network.com/direct/dbimage/50114317/Hydraulic_Pipe_Bender.jpg

The Team DFL bend pic looks like a rotary draw or mandrel bend.

Also, most race series spec that all the bends in the main hoop add up to 180 degrees,  for instance 2 5 degree bends and then 2 85 degree bends. Lemons doesn't specifically mention this, but I have a feeling a main hoop with more than 180 degrees of bend might not pass tech.

Philosophy of life: old age and treachery will ALWAYS overcome youth, enthusiasm and cash. General smartass know it all beer swilling ne'er do well. Avoid eye contact with this person, best avoided completely. 2008 Animal House Racing CMP 'Most Likely To Leave In An Ambulance' 2009 Blind Rodent Racing CMP 2010 Team Galileo CMP 2011 Roundhouse Kick Racing CMP 2012 Road Kill Grill Racing CMP (x2)

Re: question on 3.1.1

Mecha:  I'd really like to know what happened.. report back when you hear from your builder

8 (edited by RobL 2009-06-30 06:44 AM)

Re: question on 3.1.1

The tubing bender that crushes the bend like that is called a ram bender.  A local shop has one and I had exactly one bar bent from them before I decided to do all the bending myself.  It's the way that the dies interact with each other and on smaller bends it's not as noticeable. 

BTW - the $80 pipe bender makes $80 bends.
http://schumachertaxiservice.com/corwebpics/images/p20080202%20(9).jpg

--Rob Leone Schumacher Taxi Service
We won the IOE at Southern Discomfort.
We got screwed at The Real Hoopties of New Jersey  and we took cars down with us.
We got the curse at Capitol Offense but they wouldn't let us destroy the car.

Re: question on 3.1.1

I have been wondering about the total degrees for the main hoop. NASA cmc series allows 190 degrees. I have not read through SCCA recently though.

Re: question on 3.1.1

IMO that is a crush bend and therefore unacceptable...

  All benders stretch the tubing to some extent, or it would not be bent, the physics are incontrovertible, mandrel benders manage that stretch to maintain a much strength in the tubing as possible.   That bend looks like its done on a exhaust bender.  If I were inspecting(and I do inspect for Lemons)  a car with that bend in it, I'd fail it.... 

On the 180 degrees for the main hoop: usually the rules read something like: 180 degrees +-20 degrees.  Many cars need some tumblehome main hoop so it can be pushed out to the maximum and still be attached safely to to floor.

  -John

Gosh, my business card says 'Tech Tyrant'