Tube Bending Question for GAB or RPM?

[RexRod]

When bending a 2" diameter by 1/4" wall piece of DOM for a front axle, how tight can you safely bend it? Can the center line radius (CLR) be as tight as 2.5 times the tubing diameter? (2.5D) Or do you need to increase the CLR to something like 3D, or 3.5D?

I ask because I notice some companies make two bends on each end of the axle, and I'm trying to figure out how in the heck do they do it with so little room.

I'm just thinking out loud again and wondering about stuff.

David

 

[Brucer]

Rex,

Of course I'm not george or ron

My pro-tools bender has a 6inch radius die for 1 5/8 tubing...
You might go to pro-tools website and look at their selection of dies, I know they do offer tight radius dies not sure of the sizes though.. Jd2 and also vansant or maybe vanzant makes popular benders also..

 

[RPM]

We just bought a new JD2 model 32 bender. It will bend the 2" DOM with 1/4" wall. All the axles we make are now made from that. The die we got with it is a 6.5" CLR and it will bend it 180 degrees. How do they do that double bend on the end of the axle? I am not sure but working on it with some short pcs. That 2" DOM is kinda pricey.

 

[Brucer]

My old axle is made of the thick walled pipe, schedule 80 I guess..

I Used 2 90 degree elbows, and a solid piece of bar stock insert between the 2 elbows then plug welded then fully welded the inserts and elbows, then welded up all the outer joints.. Most axles I've seen have been made like this, or they were forged.
Except for the axles that have the long bend/angle farther in towards the inside of the axle
I think rpm's axles are currently like this.

 

[oldtman]

I worked for a place that bent a lot of tubing for harley parts and they had dies and a big press and a special slipery lube. The tubing would slide in the die to make the shape conform to the curve like on a dropped axle.

 

[RexRod]

Rex,

Of course I'm not george or ron

My pro-tools bender has a 6inch radius die for 1 5/8 tubing...
You might go to pro-tools website and look at their selection of dies, I know they do offer tight radius dies not sure of the sizes though.. Jd2 and also vansant or maybe vanzant makes popular benders also..

Sorry Brucer, no offense, I was asking GAB and RPM because I know these two guys have tons of experience with bending tubing. Your idea is good to just see what size dies that normally sell.

We just bought a new JD2 model 32 bender. It will bend the 2" DOM with 1/4" wall. All the axles we make are now made from that. The die we got with it is a 6.5" CLR and it will bend it 180 degrees. How do they do that double bend on the end of the axle? I am not sure but working on it with some short pcs. That 2" DOM is kinda pricey.

Thanks Ron. So a 6.5" CLR on 2" works out to be 3.25D. So between 3D and 3.5D is totally doable. Interesting.

I know with these types of benders, the wall thickness of the outer side of the bend gets thinner, and the cross section of the tube starts to take the shape of a distorted letter "D" from bending. I also know that some sanctioned rule books limit the CLR for a roll bar to nothing less than 3D for strength. That thinner outer wall of the bend I guess becomes a weak place.

I still think it's amazing that some axle makers get that second bend in there.

David

 

[Brucer]

Sorry Brucer, no offense, I was asking GAB and RPM because I know these two guys have tons of experience with bending tubing. Your idea is good to just see what size dies that normally sell.



Thanks Ron. So a 6.5" CLR on 2" works out to be 3.25D. So between 3D and 3.5D is totally doable. Interesting.

I know with these types of benders, the wall thickness of the outer side of the bend gets thinner, and the cross section of the tube starts to take the shape of a distorted letter "D" from bending. I also know that some sanctioned rule books limit the CLR for a roll bar to nothing less than 3D for strength. That thinner outer wall of the bend I guess becomes a weak place.

I still think it's amazing that some axle makers get that second bend in there.

David

sorry rex,
i've owned my bender for a while now, cant exactly remember when i bought it, probably about 5 or 6 years ago. but i never bent up an axle. i knew there was a minimum radius you could bend with the dies these companies supply, thats why i replied..

 

[Chris@whiterhino]

Sorry Brucer, no offense, I was asking GAB and RPM because I know these two guys have tons of experience with bending tubing. Your idea is good to just see what size dies that normally sell.



Thanks Ron. So a 6.5" CLR on 2" works out to be 3.25D. So between 3D and 3.5D is totally doable. Interesting.

I know with these types of benders, the wall thickness of the outer side of the bend gets thinner, and the cross section of the tube starts to take the shape of a distorted letter "D" from bending. I also know that some sanctioned rule books limit the CLR for a roll bar to nothing less than 3D for strength. That thinner outer wall of the bend I guess becomes a weak place.

I still think it's amazing that some axle makers get that second bend in there.

David

David I don't understand what you mean by 3D or 3.5D because if it is a 6.5 CLR it will take 13" of tube to make a 90* bend and 26" of tube to make a 180* bend. I also have the JD2 Model 32 bender and they don't make a die with a bend radius that tight for large tube. Tubing bent like that is done on a CNC bender

 

[RexRod]

David I don't understand what you mean by 3D or 3.5D because if it is a 6.5 CLR it will take 13" of tube to make a 90* bend and 26" of tube to make a 180* bend. I also have the JD2 Model 32 bender and they don't make a die with a bend radius that tight for large tube. Tubing bent like that is done on a CNC bender

I could be wrong, but from what I understand, the "D" in 3D stands for the diameter of the tubing. "CLR" is the center-line-radius of the bend. This radius is measured from the center of the bending die, to the center of the tube being bent. So a 6.5" CLR die would be 13" in diameter. For a 2" diameter tube with a center-line-radius die of 6.5", it works out to be 3.25 times the diameter of the tube, or 3.25D. I thought I used the term first, then the abbreviation in my first post. Sorry if it was not very clear.

I read somewhere that with the style of forming bender like Ron uses, the general rule of thumb was that the center-line-radius (CLR) has to be equal to, or greater than 2.5 times the diameter of the tubing (2.5D). Of course, the wall thickness can't be too thin as well, otherwise it collapses.

I was just trying to figure out how the heck they get the two bends on the end of the axle, so close and tight to each other.

David

 

[jeffery]

sorry rex,
i've owned my bender for a while now, cant exactly remember when i bought it, probably about 5 or 6 years ago. but i never bent up an axle. i knew there was a minimum radius you could bend with the dies these companies supply, thats why i replied..

We used to bend our exhaust out of thin wall stainless 2" tubeing by first packing it with sand and just putting plugs in at both ends and it never did get any kinks in it.i think the wall thickness was around 1/16".Just something to think about.
Vince

 

[Bill Pedersen]

Hi David,
Without a mandrel bender, a CLR 3x the OD of the tube is usually about all you can go. If you use a 3-ball mandrel and a wiper die you can get to a 1-2xD bend. Also you typically need to allow approximately 3x the OD of the tubing for the straight area between the bends.
I have a JD2 Model 4 hydraulic bender. The only 2 die available for it is a 6.5 CLR. This is very common size for a non-mandrel die.
I think a lot of the axles with the 2 close bends use a casting that is welded to the 2 inch tube. Pete and Jakes catalog states that the Super Bell axles use a tube end that is cast from 65-45-12 ductile iron.
The All Rod Performance Axle that Total Performance listed in their catalog also used ductile iron ends.
Bill