Help a retard bend tube

[XJ_ranger]

ok guys...

Im working on the Mini Baja for University of Nebraska, Lincoln, and here is the problem:

1 - no one on the team has ever touched a bender in their life...
2 - i pretended to have knowledge on the subject well enough that they put me in charge of the team supposed to bend the tube...
3 - we cant get the bender to do anything other than kink the inside and flatten the outside of ANY bend.

here are pictures and a more detailed explanation:

lets start here:
JD Tools, Model 3 Bender - ok, seems straight forward enough -

here is an over-all shot of the bender and how it is currently set up -

In chatting with Lincoln, he mentioned that it might be caused by the "trailing die" or something like that. I assume that means the part of the die that doesnt move and is this piece. This is how it is put in. The side facing "up" clearly says "top"

I am a little worried that the "trailing die" doesnt sit level with the "big die" for lack of a better term. In our bends, we obivously lifted the "trailing die" to the same level as we inserted the tube

Someone else suggusted that i was using a pipe die or the wrong size die and tube -

both pieces of the die are marked 1-1/4" 4" radius

the tube is marked
PLY/TUBE MIL-T 6736B 4130 COND N 1.250x.058 HT#518893

I assume 4130 to mean that it is 4130 ChroMo and the 1.250x.058 to mean that it is 1-1/4" OD with a .058 wall...

Lincoln also asked for a shot of the two die pieces around the tube - so i took the bender apart -

Here are a few shots of the bender together with the tube in it -

and here are a few shots of the crappy bends that we are getting note the obivous kink on the inside and the "flattening" on the outside

My thoughts -
It seems like there is too much friction on the tube in the "following die" and the tube cant slide past it as the bender forces it to. We tried using some gear oil as a lubricant (all that was laying around) to no avail.

The only time we did get a sucessful bend (55* with no kink) we used a MAPP gas torch to heat the area that was being bent as it was being bent, but you can see where the metal was heated, and I worry that changing the properties of the High Carbon steel through localised heating is not the right way to do this...
here is a pic of the one bend that we got (with heat)

looking at a full size shot of this picture above shows that even that had considerable "necking" during the streaching.

to look at a bigger shot of any of these pics - click here - (also some pics of last year's car there and the new engine)

http://www.opiebennett.com/MiniBaja/2-14-06/index.htm


Anyone have any thoughts?
Would a 6" radius die work better?
Would a "trailing die" with rollers on it instead of the fixed setuo work better? why doesnt it have 2 rolling contact points?
Is part of the bender put together wrong?

 

[Captain Ron]

4130 Condition N, .058 wall. Does .058 wall HREW do the same thing?

--ron

PS: MIL-T-6736B... didya get certs with that?

 

[XJ_ranger]

4130 Condition N, .058 wall. Does .058 wall HREW do the same thing?

--ron

PS: MIL-T-6736B... didya get certs with that?

dont have any of that to chuck in....

as for the MIL-T 6736B:
http://www.opiebennett.com/MiniBaja/2-14-06/images/IMG_4478.jpg

 

[RockControlXJ]

Your radius is too small. Your dies fit properly but your wall thickness is too thin for that tight of a die.

http://vansantent.com/model_3_bender_dies.htm

you should step up to a 4.5" or 5.5" radius.

I just finished bending the chassis for Chico State and i used a bender identical to yours with a 5.5" die with .065 wall mild steel with no kinking problems. Hope this helps

 

[Lincoln]

That is a pretty tight radius for tubing in that bender. I thought you said you were trying to bend .120" wall?

Not sure how the JD dies work and I'm having a hard time seeing what that bolt is for on the trailing die. Mine has a tab welded to it and a bolt that runs to another pin directly behind the trailing die. Start the bend then snug the bolt up to the 2nd pin, then continue bending. It's suppose to help with the issue your dealing with on the thin wall tubing.

JD2 says .083" wall on the 3.5" radius die and .058" on the 4.5". If yours is a 4" I would guess it's somewhere in between. What are you using for lube?

Someone smarter than me can confirm, but I think your going to have a problem bending that thin of tubing without some distortion no matter which die you have. Plug then ends and fill it with sand (Ron would that be conisdered a redneck mandrel bender). Report any findings.

 

[XJ_ranger]

That is a pretty tight radius for tubing in that bender. I thought you said you were trying to bend .120" wall?

I thought so too, then looked at it...

our 1-1/8" tube is .120 wall (used for A arms)

Not sure how the JD dies work and I'm having a hard time seeing what that bolt is for on the trailing die. Mine has a tab welded to it and a bolt that runs to another pin directly behind the trailing die.

The bolt on the trailing arm is just to hold the guide on there - aparently these guides are swapable for delrin and aluminum guides for bending stainless and aluminum... near as i can tell that is its whole purpose...

Start the bend then snug the bolt up to the 2nd pin, then continue bending. It's suppose to help with the issue your dealing with on the thin wall tubing.

I have no idea what you are trying to get me to do here...

JD2 says .083" wall on the 3.5" radius die and .058" on the 4.5". If yours is a 4" I would guess it's somewhere in between. What are you using for lube?

I tried some gear oil on the trailing die because that is all we had laying around...

Someone smarter than me can confirm, but I think your going to have a problem bending that thin of tubing without some distortion no matter which die you have. Plug then ends and fill it with sand (Ron would that be conisdered a redneck mandrel bender). Report any findings.

hmmm... Ive PM'd a few pirate vendors asking if they want to donate a 5.5" CLR die to help us...

If i get a chance tomorrow, ill try filling with sand...

though capping the ends of the tube will be a lot of work for every bend...

not to mention make the tube fricken heavy...

 

[Captain Ron]

...
Plug then ends and fill it with sand (Ron would that be conisdered a redneck mandrel bender). Report any findings.

It would.

It also shows that boatyard awning / dodger builders and rednecks are the same creatures.

The following die should be adjustable in the amount of "pivot", and how tightly it "clamps" the tube to the radius die. Clamp down hard, and limit the pivot to as little as possible.

If the following die contacts the radius die, you probably need a new following die. It might be possible to remove material on the following die to increase the clearance to the radius die, but contact generally means replacement time.

Get the longest arm you can... it's alot of friction to overcome, and it has to be bent slowly and evenly.

Thin wall 4130 is going to be tough.

--ron

 

[Lincoln]

The bolt on the trailing arm is just to hold the guide on there - aparently these guides are swapable for delrin and aluminum guides for bending stainless and aluminum... near as i can tell that is its whole purpose...

Ahhh, I read some discussions on that. Making sense now.

I have no idea what you are trying to get me to do here...

Take a look at this pic:

The bolt on the right side of the pic tightens to a secondary pin put in behind the trailing die (has a flat milled in it). It keeps the die pressure on the front(?) edge to help resist kinking and distortion. Might try adding it to your die and see if it helps.

I tried some gear oil on the trailing die because that is all we had laying around...

Get some white lithium or even regular grease in a tub. Not sure how much it will help but you should be able to feel the point it wants to start kinking better.

If i get a chance tomorrow, ill try filling with sand...

though capping the ends of the tube will be a lot of work for every bend...

not to mention make the tube fricken heavy...

I used these a couple of times when I was bending in my poop pipe bender.
http://www.pipeplug.com/LPmechanical_alum.htm
Don't make me call you a p***y.

I haven't messed around much with tubing that think so I might just be feeding you a line of BS.

 

[Lincoln]

It would.

It also shows that boatyard awning / dodger builders and rednecks are the same creatures.

What's bad is I can't even remember where I learned that. Electrical conduit maybe?

 

[XJ_ranger]

Take a look at this pic:

The bolt on the right side of the pic tightens to a secondary pin put in behind the trailing die (has a flat milled in it). It keeps the die pressure on the front(?) edge to help resist kinking and distortion. Might try adding it to your die and see if it helps.



Get some white lithium or even regular grease in a tub. Not sure how much it will help but you should be able to feel the point it wants to start kinking better.



I used these a couple of times when I was bending in my poop pipe bender.
http://www.pipeplug.com/LPmechanical_alum.htm
Don't make me call you a p***y.

I haven't messed around much with tubing that think so I might just be feeding you a line of BS.

hmm, ill try adding a tab with that bolt and another bolt to keep the trailing die from pulling over and making the friction more than it needs to be... that picture makes more sense now...

it is annoying enough to expense parts that we actually use - explaining a 60lb sand bag on an expense report "on a hunch" might be a little iffy - though if nothing esle works, ill give it a shot...

Thanks for the help...

 

[Lincoln]

Just find some sand somewhere and do a test bend on a single short piece.

I would not add the second bolt you were talking about, just the one on the leading edge to keep the triailing die from rotating.

 

[XJ_ranger]

Sucess!!!!!!!!!!!!!!!!!!!

we packed with sand and it still kinked (and shot the end off one of the tubes)

then we tried heating and lubing the shit outta the trailing die - this caused flaming bearing grease and more kinks

then we tried (as a last resort on a piece of scrap) flipping the trailing die so the side clearly marked "Top" was now on the bottom.

Sucess!!!!!!!!!!!!!!!!!!!!!!!!

no lube, no heat, just pure bending tube!

No kinks, very little outer edge flattening, and very little splay.

Very happy.

pics later

 

[Captain Ron]

So the pivot point on the trailing die changed? Further away from the bending CL?

--ron

 

[XJ_ranger]

So the pivot point on the trailing die changed? Further away from the bending CL?

--ron

no - th contact points on the trailing die changed. there are 2 contact points on the trailing die -

one is "flat" and the other has an angle.

So the friction on the tube as it was pulled through changed...

See the contact patch on the left edge has a slant, and the contact patch on the right has no such slant - and is "flat"

The "top" of the die is facing us, and as the tube gets pulled through the bender, with the side labeled "top" up, only the front edge of the left contact patch actualy touches the tube BUT the whole entire contact of the rear contact was touching the tube. This was evident by the wear patterns in the grease that we were using.

When flipped, the tube seems to touch the entirety of both contact patches - and no longer puts that "point load" from the one edge on the tube.

even though there is more tube in contact with the "contacts" the friction realised friction (at the end of the lever near as i could tell) was less...

we bent about 30' of tube tonight after fliping that stupid trailing die with out a single kink.

and here is a photo of the guys holding the piece of scrap that we bent without kinking:

links to more photos...
http://www.opiebennett.com/MiniBaja/2-17-06/index.htm

 

[Lincoln]

So it sounds like my original thought we were talking about was it. Die was in backwards.

Is it possible that since they are replaceable that the trailing die pads (I can think of the correct terms) were reversed when someone had it appart?

Congrats, now you can tell everyone your a tube bending maniac and better than the Captain.

 

[Lincoln]

BTW, I'm pretty slow. It can clearly be seen that the die isn't right in your third pic from the top.

 

[XJ_ranger]

So it sounds like my original thought we were talking about was it. Die was in backwards.

Is it possible that since they are replaceable that the trailing die pads (I can think of the correct terms) were reversed when someone had it appart?

Congrats, now you can tell everyone your a tube bending maniac and better than the Captain.

yes.......


Lincoln was right.......




I think that the pads got fliped at some point for some reason, but then not put back - i really dont know, all i can do is speculate right now...

I'm just glad to have a working tube bender than bends the tube that I am trying to bend...

And im glad that i dont have to worry about seams like i would with HREW... - its hard enough to keep the bends in the same plane with a bender that isnt level - i wouldnt want to think about keeping a seam in a plane with 3 or 4 more bends...

 

[Lincoln]

Clamping something to the tube as a base for your level helps. Something like this:

Also I use those roller stands to balance the tube and to get it level.

Then I think some of the smart people should give us some schooling. I'm still trying to figure out how to get the degrees you need to twist the tube on a multi plane bend.

I've gotten away with working off the side I want verticle and getting using an angle finder to get the lean I want on the second side. Problem is I've been looking at something and it's going to have three planes. It gives me a headache thinking about it.

 

[XJ_ranger]

I've gotten away with working off the side I want verticle and getting using an angle finder to get the lean I want on the second side. Problem is I've been looking at something and it's going to have three planes. It gives me a headache thinking about it.

dot product my friend

dot product....

if you want to go 3" in one direction, say X and 6" in another direction, say "Y" then 1" in another direction "Z"

then you pick the direction of the tube - just make that 1 and make it "x"

then you have 2 vectors -

1 vector that describes the direction of the tube to start with, and another that describes the new direction of the tube...

so for our two vectors -
<3,6,1> = vector A
<1,0,0> = Vecotr B

the dot product would be -
3*1+6*0+1*0=3

using the other property of the dot product -
||A||*||B|| cos @

where @ is the angle in between the two vectors -
and ||A|| is the magnitude of A and ||B|| is the magnitude of B

so we have:
||A|| = (X^2+Y^2+Z^2)^(1/2) = (9+36+1)^(1/2) = 46^(1/2) or about 6.78

||B|| = (1^2+0^2+0^2)^(1/2) = 1

so we have:
3 = 6.78*1*cos @
Cos^-1(3/6.78) = @ where Cos^-1 is inverse cos or ArcCos...

@ ~ 63.73 degree or 1.11 radians...

I hope that makes sense...

 

[Lincoln]

dot product my friend

dot product....

if you want to go 3" in one direction, say X and 6" in another direction, say "Y" then 1" in another direction "Z"

then you pick the direction of the tube - just make that 1 and make it "x"

then you have 2 vectors -

1 vector that describes the direction of the tube to start with, and another that describes the new direction of the tube...

so for our two vectors -
<3,6,1> = vector A
<1,0,0> = Vecotr B

the dot product would be -
3*1+6*0+1*0=3

using the other property of the dot product -
||A||*||B|| cos @

where @ is the angle in between the two vectors -
and ||A|| is the magnitude of A and ||B|| is the magnitude of B

so we have:
||A|| = (X^2+Y^2+Z^2)^(1/2) = (9+36+1)^(1/2) = 46^(1/2) or about 6.78

||B|| = (1^2+0^2+0^2)^(1/2) = 1

so we have:
3 = 6.78*1*cos @
Cos^-1(3/6.78) = @ where Cos^-1 is inverse cos or ArcCos...

@ ~ 63.73 degree or 1.11 radians...

I hope that makes sense...

Printed.