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Bent Tube Thickness measurement

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shrivara View Drop Down
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    Posted: Apr/24/2015 at 12:08pm
Guys! I saw a photo of a car undergoing technical inspection where one of the judges was inspecting the tube thickness especially at the bends using some kind of instrument...

All I wanted to know is
1. Did u guys undergo through such process in any of the events so far??
2. If at all I wanted to know what is the thickness at the bent portions of my rollcage, what can be done?
3. Is it really necessary to check thickness of tubes at bends??
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Post Options Post Options   Thanks (1) Thanks(1)   Quote rasmuet Quote  Post ReplyReply Direct Link To This Post Posted: Apr/24/2015 at 2:05pm
That is part of technical inspection checking for the minimum thickness of primary material in your roll cage and throughout the vehicle.  It is necessary to check the thicknesses of the tubes at the bends because if you had primary material at (.062" thickness) and you had a significant bend you may no longer meet that rule.
 
It is essentially an ultrasound for metal tubes.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ruturaj Quote  Post ReplyReply Direct Link To This Post Posted: Apr/24/2015 at 4:29pm
Which event are you talking about BSI Jamshedpur or Baja Sae India 2015? We were at Indore and i was at Tech inspection with our car ,none of the inspectors checked our rollcage thickness by any instrument. They just asked dimensions that's all!! I don't remember such in other bays too
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Post Options Post Options   Thanks (0) Thanks(0)   Quote vin2000 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/24/2015 at 5:24pm
He is talking regarding US events where frame check is carried out in every detail. Both the events in India don't do that as far as I know.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Richie_Dagger Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2015 at 12:25am
Never seen 'em check our bends. They always picked straight members. Checking bends is lame, unless you just want everyone to run 1x0.120 frames or square roll hoops...
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Post Options Post Options   Thanks (1) Thanks(1)   Quote RLM Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2015 at 4:25pm
They have checked our thickness in bends almost every year. We just upsize to the next thickest material above the rule to account for thinning in the bends. this is a good idea regardless of whether they check or not as by bending the tubes you are stressing the material and causing it to be more succeptable to failure. last thing I want to see is someone get seriously injured from a frame failure just so a team could save a pound of weight. if your that desperate for weight savings to compromise safety, just lay off the cheeseburgers and pizza in the weeks leading up to comp and take a monster dump before you go out on the track. 

Safety first. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elpwnage20 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2015 at 7:10pm
How are you supposed to respond to that though? There isn't anything in the rules about this and there is no way that a team would know that they require this unless looking at the forum. Would you basically be disqualified and not allowed to race cause of this?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shrivara Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2015 at 11:43pm
Yeah.. I completely agree with RLM that it is the " Safety First"...
But if you are going to use the next thicker material above the rule how can you be sure that because of thinning the thickness wouldnt come below the rule( for different bend radii)?? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elpwnage20 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2015 at 1:36am
Also, how are they supposed to check the thickness of a bent tube?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zglazer Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2015 at 8:04am
The little ultrasound machine Erik described is used to check tube thicknesses of both straight and bent sections. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sweeneyp Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2015 at 11:20am
interesting, they've never once checked a bend on ours. 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Aztec Warrior Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2015 at 11:56am
I've been thru tech 5 times. I have never seen a thickness checked at a bend. All they are trying to do is make sure you are useing the tube dimensions you are claiming on your roll cage spec sheet. Everyone uses 1.25 x.065tubing. If they checked at bends, they wouldn't have enough cars to run the race. Believe it or not tech officials are not out to get you.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shrivara Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2015 at 12:48pm
Well, its interesting to see diversified opinions on this topic...
@Aztec as u said most teams use 1.25x0.065 tubing what bothers me is due to thinning is there any chance of thickness getting reduced less than 1.57mm as mentioned in the rules??
 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Aztec Warrior Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2015 at 1:52pm
There is a chance. I am sure you could estimate the thinning with a simple equation (conservation of volume). But personally I have never worried about it, and have not had problems with it. I actually talked to the guy checking in auburn, and he said that he normally sees thickness vary down to 0.063 (in straight sections), and he passes those cars as there is a tolerance in thickness of tubes. He also mentioned that thick paint can add a couple thousandths. So if you are worried about it, put a couple extra coats of paint on the bends. I really don't think it is a safety thing. That is plenty strong tubing for the speeds we are going (as long as it is notched and welded properly.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2015 at 3:06pm
If they check the thicknes sideways will be the same as original.
Unless the car has a very small bend radius, with severe profile lost, i really don't see any safety issues
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Post Options Post Options   Thanks (0) Thanks(0)   Quote i6overboard Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2015 at 3:24pm
Originally posted by Aztec Warrior Aztec Warrior wrote:

as long as it is notched and welded properly.

This is more of problem than any thinning of the bend area.. Techs are for the most part nice guys, if I was doing tech I give more people crap about the welds they are putting out, but i guess what should they expect when most of welders only have a year or so of experience max.

Like a few others have said, they just make sure you used the tubing that you say you've used and you'll be in the clear...


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