My dad o is a pipe fitter on the nuclear submarines and he bends a lot of pipe, All they use are the big mandrel bending machines, and a real "mandrel bender" has the two wheel that pull the pipe around and then they have the internal mandrel is inserted and then the pipe is bent and then the mandrel is extracted. this way there is always support on the inside and there is absolutly no deformaion. This doenst mean that the outer wall thickness doesnt decreese, the the shape and therefor the flow dynamics remane the same. Basically you could roll a golve ball through when its done.

CJG

 

The bender is getting a huge make-over. One die will take the position of the pipe rest. A piece similar to the pipe rest will press the pipe the the bending die and pull the pipe around it.
I will be busy getting that together and I will takes pics of everything at once. I cut off the piece of messed up pipe and will get some pics of that too Hopefully I won't be bending any more pieces like that

 

so are you going to use a stationary round bending(forming) die with a counterbending(pressure) die

like thise

 

The mechanics would be very similar. I am making a inside mandrel like the one suggested to me in an earlier post.
I am still hoping to avoid scuffing the pipe. The biggest difference I see is that where I placed the red arrow is where the die not being used for the radius will be used for that.
The slots that the ram pushes against illustrates what I had unsuccesfully tried to explain of why the ram cannot make much of a bend in one position.
Unfortunately that is about the only thing I have got right so far

 

thought of using your normal rotary draw(like in picture) bender, but use longer pipe than needed. fill pipe with water after welding on caps. after bend cut off caps. the water shouldnt let the pipe crush(along with proper wallthickness(which Id assume is the #1 reason for crushing, #2 is CLR being too tight))some people use sand, but the sand will let some compression take place.

just a low-rent idea.


EDIT: the above mentioned idea will most likely be too much work for any preacticality.

making a true mandrel bender is the key, but AFAIK unless your going with some crazy small CLR(like 7-8") or are using some tue/pipe with tiny wallthickness, a rotary draw is perferable. the madrel will think the outside wall of a madrel bent piece, and depending on application that CAN be a problem, although i wouldnt guess it would be in a hobbiest, auto fabrication use. unless your talking about a cage, but you have to use a set wallthickness so theres no problem there.

 

dont know if you have seen some of these but might help

their benders look pretty good http://www.pro-tools.com/

heres a site on segment bends, helped me out with my bender work
http://www.porcupinepress.com/_bending/segmentbends.htm

 

Here is a video of one that I am not sure if they have anything inside it but it does not appear to try to collapse. http://www.pro-tools.com/video/erc.mpg
Since this is a non-crucial(doing it for the fugg of it) project, I want to tweak it to where I can get the best bend with the least amount of headache in the long run.
Capping and pressurizing is more work than I want to have to do to each pipe/tube when it is finished. That may mean a lot more headaches and changes and money on the front side but in the end I know I will be happier. Hopefully the "*****" mandrel on the inside at the apex of the bend will help.
After seeing what happened to the last bend I learned a lot about the dynamics of the forces but it left me with more questions than answers
This is really trial and error from here on out.

 

Damn Hans thanks for that link to the segment bends calculator! That is going to be incredibly handy.
I just had my "Mechanical Drawing" book to fall back on for trying to figure that out. I haven't even looked at it yet for that. I tried to find a pic of that book on Ebay and found a first print from 1920! This is like a shop bible. I think mine is a twenty-something edition and it's at least 20 years old.
I know it is off the subject but it's an FYI in case you never heard of it or run across one you can pick it up http://cgi.ebay.com/ws/eBayISAPI.dll...category=12570

Before the "computer age" I got I was constantly going to that book. Tons of info. Now a whole lot can be found on a word search on Google. Sometimes though I still ave to dig it out.
I am going to save that page you gave me offline in case they ever shut it down. I just got an extra wireless NIC for the PC I am putting in my garage. Now I have to get one of those keyboards like they use in a fast food place so I can pull up **** out there including that link
Thanks again Hans!

 

thanks that will make a great addition to my collection of 'useful' books as my fiance puts it

wanna see if you can make a cheap english wheel for me...
havent foound great plans yet, and dont want to buy a lathe to make some wheels for one atleast not yet...

 

Damn an english wheel! Haha!!! I had not even seen one in forever until I saw Jesse James using one on "Monster Garage" He was making fenders.
Getting one is not the bigger of the challenges. Those take a while to get the feel. But you can sure do some serious work once you get the hang of it

 

Hey, here's ya a budget engwheel!

 

My dad did up some really nice drawings for a english wheel, it looks nothing like that budget one their. It looks much like the type they use over in UK.

Would post photos, but dont know were the drawings are on here. heh

My father is in to that type of body work. He likes to never use bondo. It's always nice having someone in the house like that and also knows what he is doing when it comes to body work.

Nice setup so far Scalliwag.

 

how about a chassis jig for my first gen... so far the best idea is to go get some scrap I-beams from a construction site. I have seen some cool designs using this method.

after i get it mounted i need to make a 6' brake(figure why not) bend at least 16ga...using thick *** plate and lots of counterweights

and if i get that far it would be nice to have a hydrolic shear that can cut 1/8" plate...have some ideas in head but is mostly worthless

if you only saw some of the stuff online that is low-rent but functions so sweetly like this
they turn this:


into this:


works nicely:

 

I-beams are a must in my opinion for any frame/chassis jig. I am building a T-bucket roadster after I finish my repu project which I still have to get to the house. I have to make a frame jig for the T and possibly for the repu depending on how far I decide to take that.
As far as a brake and a shear good luck getting those built. They would kick my ***

 

Speaking of getting my *** kicked this has been a long day. Redesigning the bender was a workout because of all the pulling things apart and putting them back over and over and over for measuring, drilling, cutting, etc.
The depth of the "*****" is crucial. When it is too deep the tube breaks and when it is not deep enough the tube crunches.
What I am finding is that there is a fine line between the two. Less than 3/4" makes all the difference.
I went through 6' of aluminum so far. I have one more 6' stick but the stuff is a little $ to keep fugging it up while I tweak this.
I am going to get a stick of steel tube and work with it until I get some success and then switch back.
Here are the pics of the changes and what happens when the tube splits. Of course I forgot to get a pic of the really jacked tube and I am not going back in the garage tonight I will let you guys see that though.

 

have you thought about heating the external apex of the bar?

It would soften the bar, and allow easier bending with less chance of cracking, but it would need to be held in the bender whilst it would be allowed to cool naturally (if you don't want it hardened anyway)

 

Hopefully I will be able to just bend the pipe once this is finished without filling it or heat etc. At least all the benders I have seen don't appear to require any special procedure.

Here are the pics of the first bend that would be better described as a crunch

 

that's just plain nasty!!!

But you could heat it with an oxy-acetelene torch during "testing", so you can find a better setup with more flexibility - if only to get the bend started easier


And now i think about it - if you heat it, it would relieve the stresses built up in it by the cold-working. Which would mean a stonger bit of pipe!!!

 

this might sound stupid but what are you using for lube on the pipe. its looks like it the bending die(one pushed by ram) is too tight and catching on the pipe, might shim it out, or lube with wd40 or similar

 

are you using a solid madrel insert(***** style)

i have seen some that use multiple pucks packed together attached with cable or maybe strong spring

like so(dunno about spacing, just guessed)
MSPaint rules for drafting!!!

 

double post

 

That picture was from last week when the dies spread out on me during the bend. The next bend was not much better. Between that and some of the helpful posts I decided to redesign the way the dies worked.
Now I have one busted bend and a partly crushed bend from the "*****" being out of position.
It will have to be at just the right place not to get a broke or crush in the pipe.
But I am tired of fuggin up aluminum since I only have a 6' stick left. Steel will be a lot cheaper to play with. I actually have a job to use the aluminum on so if I jack much more up I will have to get another batch
But don't let the pics confuse you. I have made a little progress in that it appears much more like a good bend is within reach.... maybe

 

Scalli.. I was talking with someone a while back about bending me a section of 4"aluminum for an intake. We got to talking about the process and he told me that (A) aluminum was the most difficult to bend (tedious PITA with a mind of its own), and (B) that you need to start with aluminum tubing with a particular anneal to it, so that it will bend properly.

I don't know how accurate his claim was but it might be worth asking a few questions before you mangle up more of what may not be easily bendable aluminum.

Good luck on the project.

 

I am using 6061 in case you ever talk to him again. I will try to find out about that. Thanks for the info.
It seems as though a lot of the IC pipe I have seen claimed to be 6061.
The material I am using is Alcoa so it is very good quality with very good consistancy as far as size and wall thickness. So at least those are not factors in the failure.

 

I just did a quick search on Ebay and found this cold air kit that is supposedly 6061. The bends look great... damn bastards!!!
http://cgi.ebay.com/ebaymotors/ws/eB...tem=2444537590