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JFW
10-11-2012, 02:58 AM
Hi guys,

I just recently bought a Kennedy #12 tube bender. This is a lever operated machine designed for thin walled tubing (max. diameter: 1 1/4"). I know from a very good source that this is a proper good bender, but it would be interesting to hear if there are other ones out there using such a machine. The bender I've bought is missing the follower-blocks, so that will be the first things to make when I get it (somehow) from Manchester to Norway. So, any information and/or experiences with using such a bender, would be highly appreciated.

http://www.lathes.co.uk/taylor/img72.gif

More about Kennedy bending machines here: http://www.lathes.co.uk/taylor/page13.html

Thanks,

Truls
Hølen, Norway
www.johnsenframeworks.com
www.facebook.com/johnsen.frameworks

Mcgyver
10-11-2012, 08:26 AM
That is a nice looking rig.

Years ago I wanted to make some small radius bends and came up with a design that is very similar; I didn't know there was a commercial equivalent....some pics like that would have saved some head scratching! The key which i came up with (and subsequently learned is nothing new) is the "shoe", the half round segment on the outside of the pipe. This is what distributes the force so you don't get the material ploughed up on the outer edge. clamping force on mine is achieved by the outside roller being on a cam
.
http://bbs.homeshopmachinist.net/threads/24051-A-tube-bender-saga?

justanengineer
10-11-2012, 09:24 AM
In the military we called our hand operated single sided draw bender the "muffler shop special" bc simply put, we hated it. Because you have to bolt them down solidly to manually use them, you have to either put them in the middle of the floor, have a heavy enough bench (REALLY HEAVY) to bench mount them, or theyre in the way. Personally, I would either modify it to accept a hydrauic cylinder so you dont have to mount it solid, or else bin it and build a double draw bender. If you ever have to do a lot of bending or where you need accuracy (like building a cage for a race car), this is NOT the bender you want.

BigJohnT
10-11-2012, 09:43 AM
What is a "double draw bender"? I googled and came up with no hits...

John

JFW
10-11-2012, 02:14 PM
Thanks for the replies, guys. The bender have the same basic design as the Di-Acro tube benders, and utilize what is commonly referred to as rotary compression bending. This is a proven design that is used for thin walled tubing with great success. It will require a sturdy base, so that will take some thinking to fit into an allready crammed 40 sqm workshop. Hopefully it will cover my bending needs when I get it set up. I will also make some modifications to it when I find the time. Finding information about these are hard (nothing apart from the lathes.co.uk page).

Truls

dave5605
10-11-2012, 02:33 PM
Here in the states a lot of offroad guys that bend their own tubing bury the female part of a trailer hitch flush in their concrete floor (hole facing up obviously). Then you mount the bender on a piece of 1/4" wall, 2x2 tubing. When you want to use the bender just slip it in the trailer hitch sleeve that is in the floor and bend away. When not in use the bender can sit over in the corner.

Another way is to use the trailer hitch that is on the back of a pickup truck (common over here) and build a 90 degree adapter that essentially does the same thing as the hitch in the concrete.

toyjeep73
10-11-2012, 02:58 PM
What are you actually bending, copper tube? I see "thin wall" mentioned a couple times. Seems to me that a plate on the bottom and a good vise to hold it is all you need. All you do is spin the handle right?

The kind of bender that I think has been referenced above requiring a serious mount is for bending roll cage style tube such as 1-3/4" x 1/8" wall DOM. I did one cage by hand with one of those (2" DOM) and we fitted it up with an air cylinder for power after that. All I had was 4 drop in anchors in the floor of my garage to hold it when were yanking on it with a 6' long lever arm though.

justanengineer
10-11-2012, 03:26 PM
What is a "double draw bender"? I googled and came up with no hits...


http://www.asedeals.com/tubing_benders.html

A single draw bender like the OPs has one die and one "shoe" that draws the tubing around from one end of the radius, meaning you have to know where the start of your bend is or do a bit of math if youre doing some complex curves.

A double draw bender like the Bendpak shown in the link has two "shoes" with a ram powered die placed in between. You only need to know where you want the center of the bend to be, simplifying things quite a bit. Despite the cost, there really isnt any more to them than building a wood splitter. Ive been collecting parts for quite awhile to build yet another as I have this bad habit of building one, needing money, selling it (bc I can always build another), then taking forever to build another or worse yet, scavenging parts from one partial project to build another.

JFW
10-11-2012, 03:45 PM
What are you actually bending, copper tube? I see "thin wall" mentioned a couple times. Seems to me that a plate on the bottom and a good vise to hold it is all you need. All you do is spin the handle right?

In my case, thin walled (around 1mm) steel tubing (4130 or similar) up to 1 1/4" OD. I think it might need a bit more than mounting in a vise (it weights about 80 pounds), but it won't need the same kind of anchoring as a heavy duty unit.

Truls

BigJohnT
10-11-2012, 03:57 PM
http://www.asedeals.com/tubing_benders.html

A single draw bender like the OPs has one die and one "shoe" that draws the tubing around from one end of the radius, meaning you have to know where the start of your bend is or do a bit of math if youre doing some complex curves.

A double draw bender like the Bendpak shown in the link has two "shoes" with a ram powered die placed in between. You only need to know where you want the center of the bend to be, simplifying things quite a bit. Despite the cost, there really isnt any more to them than building a wood splitter. Ive been collecting parts for quite awhile to build yet another as I have this bad habit of building one, needing money, selling it (bc I can always build another), then taking forever to build another or worse yet, scavenging parts from one partial project to build another.

The only thing that doesn't make sense yet is how the shoes work. The tiny fuzzy video doesn't help much... but I understand the principal of operation and yes just knowing the center of the bend is nice. Do you have any details about how the shoes work?

Thanks
John

JFW
10-12-2012, 06:18 AM
The only thing that doesn't make sense yet is how the shoes work. The tiny fuzzy video doesn't help much... but I understand the principal of operation and yes just knowing the center of the bend is nice. Do you have any details about how the shoes work?


If you refer to the Di-Acro bending prinsiple, then this one should give you a better indication:

http://www.youtube.com/watch?v=Z1oA-VdgL6w

Truls

BigJohnT
10-12-2012, 07:04 AM
If you refer to the Di-Acro bending principle, then this one should give you a better indication:Truls

I was asking about the double draw bender.

http://www.asedeals.com/tubing_benders.html

John

justanengineer
10-12-2012, 12:42 PM
The only thing that doesn't make sense yet is how the shoes work. The tiny fuzzy video doesn't help much... but I understand the principal of operation and yes just knowing the center of the bend is nice. Do you have any details about how the shoes work?


The first link below is the same video but a bit better quality. If you look right at the 22 minute mark, you can see a closeup of a bend in action. The second link is to Bendpak's site. I have no affiliation with them, just have experience with one of their machines and highly recommend them. Thanks to a former employer that had one, I was able to build two of my own that were similar.

Basically, the shoes are on two arms which are simply pinned to the main body of the machine to allow them to rotate as the die is pushed between them. The trick is to ensure that the shoes and dies are both in contact with the pipe at the bending/forming point throughout the bend. On my second one, I used a common pin location in an attempt to simplify changing shoes and dies for different sizes and bend radiuses, but it actually made changing a PITA. I also didnt use shoes, but rather two round "pulley-esque" dies that were lathe turned, but after the fact I realized standard shoes are more forgiving if there is any slop, misalignment, or positioning errors when built, and dont require changing the mounting arms as well for every diff size. Unfortunately, I almost never take pics of my own work, else Id post some to simplify my explanation of what I did wrong. The second one worked, but not great. When I get my toolbox from the storage shed on my brother's place, if I can locate it, I have a hand powered brake line bender that I built a few years ago that operates very similarly that I can post pics of.

http://www.youtube.com/watch?v=MKJia05KzmQ

http://www.bendpak.com/benders/pipe-benders/1302BAS-302.aspx