Author Topic: Bendy pipes (Read 13608 times)

John-Som · « **on:** May 24, 2011, 12:46:35 PM »

I would welcome the views and experience of members on the use of Cerrobond (USA) or Bendalloy (UK) for the forming of curved exhaust (muffler) systems. According to Strictly IC this alloy which melts below the boiling point of water supports thin wall tubing whilst been bent into curves. I was stopped in my tracks however when I discovered that the minimum order is for 500 gms at £40 plus £8 shipping costs. I do have a pipe bending tool which works fine on the copper tubing that we use on our steam engines but I am looking to shape 1/4" thin wall steel tubing which I feel will need internal support. Suggestions anyone ?

John-Som

Jasonb · « **Reply #1 on:** May 24, 2011, 01:00:42 PM »

Fill it with molten soft solder and melt it out afterwards, this is not ideal if you want to silver solder any of teh pipework after as the remaining traces of lead affect the joint.

Jason

Bluechip · « **Reply #2 on:** May 24, 2011, 02:04:32 PM »

John

http://www.bendalloy.co.uk/page9.html

Curiously enough that subject came up with some mates a few weeks ago.

There is, apparently, some other stuff, resin based .. link above. Other than the link, I have no other info.

No idea whatsoever what it's price/performance is.

I have used odd sizes of Bowden cable, but it's hit and miss if it fits the bore of the tube.
Used to have access to a m/cycle service dept. Often scrounged odd bits of speedometer/ brake etc. cable.
Inners & outers.
Sometimes lucky. Mostly not ..

Dave BC

andyf · « **Reply #3 on:** May 24, 2011, 05:30:23 PM »

I've heard all sorts of tales about bending piping like packing it with sand or even a finer powder like dry cement, or filling it with water and then freezing it. Dunno if any of them work.

But are the bends of such a radius that one of these might help? http://www.holden.co.uk/displayProduct.asp?pcode=095.164

Andy

John-Som · « **Reply #4 on:** May 25, 2011, 01:52:14 AM »

Jason

The molten soft solder idea strikes me as a definite possibility well worth a try. I can imagine that it would be malleable in a similar way to the commercial, and very expensive, 'Bendalloy' option.

Dave

I like the notion of using speedo or bowden cable but I don't think they would allow the sort of tightish radii that this project calls for.

Andy

That pipe bender looks very promising in that there may be some freedom in varying the radius of curves. Perhaps combined with Jason's soft solder suggestion this could provide the answer I've been seeking.

Thanks for all your help.

John

John Hill · « **Reply #5 on:** May 25, 2011, 02:18:22 AM »

Heres a thought, wind a soft wire helix (i.e. spring) that can be slid into the pipe. Bend the pipe then pull on the end of the helix which will collapse and enable it to be pulled free of the tightest bends.

Bogstandard · « **Reply #6 on:** May 25, 2011, 05:38:53 AM »

John H,

You can buy sets of small bending springs, unfortunately, if you do too sharp a radius (and not all that small either), you have to destroy them to get them out.

After buying two sets, I came to the conclusion that they really are a waste of time and money, I could bend tubes better just by using my fingers.

My way John (S), would be to bend a solid bar first to whatever radius you require, then bend a twist drill in it's middle to the same radius. Using the bent drill, drill down thru the bent bar to make the bent tube.

It's easy when you know how

John

John Hill · « **Reply #7 on:** May 25, 2011, 06:07:11 AM »

Quote from: Bogstandard on May 25, 2011, 05:38:53 AM

John H,

You can buy sets of small bending springs, unfortunately, if you do too sharp a radius (and not all that small either), you have to destroy them to get them out.

John, thats why I suggested making the one's own bendy spring out of soft wire as it is easy to just pull it out unravelling it as you go. We can still get curtain spring which I have used with thin wall aluminium tubing.

I wish I could get something for the 36mm thin wall steel tubing I used on my bike project, but I had a kludge that was better than expected, I hacksawed partial crosswise cuts until the tubing would easily bend into the required curve then brushed flux into the cuts and brazed them. I guess that wont be 100% strength but it certainly feels quite sturdy.

slowcoach · « **Reply #8 on:** May 25, 2011, 06:27:09 AM »

This stuff might do the job John-Som. Its called Polymorph a themal plastic.

&feature=related Pollymorph.

Its can be found here. http://www.gyroscopes.co.uk/d.asp?product=POLYMORPH

Cheers
Rob

AdeV · « **Reply #9 on:** May 25, 2011, 07:22:08 AM »

Be careful when ordering Polymorph, you don't want to end up with the wrong stuff....:

spuddevans · « **Reply #10 on:** May 25, 2011, 08:14:11 AM »

Quote from: slowcoach on May 25, 2011, 06:27:09 AM

Its can be found here. http://www.gyroscopes.co.uk/d.asp?product=POLYMORPH

Just came across another supplier that is cheaper.

http://www.mindsetsonline.co.uk/product_info.php?cPath=18_177_533&products_id=550

They have a load of other great stuff too.

Tim

Bernd · « **Reply #11 on:** May 25, 2011, 08:22:22 AM »

John,

See if you can find somebody in the UK that get's Model Engine Builder. In issue #24 there is a nice article on building a simple tubing bender for 1/4" dia. tubing.

Bernd

John-Som · « **Reply #12 on:** May 25, 2011, 09:14:06 AM »

Thanks guys for the flow of helpful ideas and links. But to be honest Bogs has once again proven his superior engineering skills with his brilliant and innovative solution.

(Bogs, it worked very well, the only problem I have now is straightening the drill bit)

John-Som

dsquire · « **Reply #13 on:** May 25, 2011, 09:57:31 AM »

Quote from: John-Som on May 25, 2011, 09:14:06 AM

Thanks guys for the flow of helpful ideas and links. But to be honest Bogs has once again proven his superior engineering skills with his brilliant and innovative solution.

(Bogs, it worked very well, the only problem I have now is straightening the drill bit)

John-Som

John-Som

That should not be too hard to straighten. Fasten the shank end of the bent drill bit securely to a light chain. Now get out your heating equipment and heat the bent drill bit up to the point just before it is molten. At this point swing chain with bent drill bit in a circular motion at a high rate of speed. Now centrifugal force is your friend and when you reach the correct speed the drill bit will straighten. Be careful not to swing it too hard or you may cause the drill to straighten too much and you will loose the spiral. Come to think of it, if you do loose the spiral maybe it would work OK as a reamer. In any case pay careful attention to the temperature after it has straightened and you can plunge it into a can of oil to temper it again without having to reheat it.

Cheers

Don

Jasonb · « **Reply #14 on:** May 25, 2011, 11:44:58 AM »

There is another very nice tube bender in the latest issue of Model Engine Builder that dropped on the doorstep today.

I have a set of external springs that avoid the problems of getting stuck in the tube but they are still quite hard to remove from the outside. You can also get the small record bender that does 1/8,3/16 & 1/4 but I did not find it that good on copper.

J

PS when melting out the solder make sure you start heating from one end of teh tube, I still have solder stuck to the workshop ceiling where I heated the middle first

John-Som · « **Reply #15 on:** May 25, 2011, 12:10:34 PM »

Nice one Jason ! Wifey would not be a happy camper with splats of solder over the lounge ceiling.

John

Bogstandard · « **Reply #16 on:** May 25, 2011, 12:44:45 PM »

John,

Sorry about the bit of ribbing, but unless you can laugh about it, sometimes you could cry.

But joking aside, what is the tubing for? Could the item be made from something a little easier to bend?

I do have some easy to make bender plans that can take up to 1/4", in fact up to say 3/8", it just depends if you have a milling cutter of exactly the right size of the material you want to bend, to cut the half round formers on the mill using a spindexer or RT.

You are quite welcome to have a copy.

John

John-Som · « **Reply #17 on:** May 25, 2011, 12:55:14 PM »

John

I'm after making a swept exhaust for my Upshur vertical 4 stroke instead of the sticky out one show on the plan. Rather than use copper brake line I was pondering on the idea of using thin wall 1/4" steel tubing but you know me John I do get these silly ideas sometimes. I was even thinking of having it chrome plated.

John

Bogstandard · « **Reply #18 on:** May 25, 2011, 01:03:54 PM »

John,

Use copper instead, easier to bend, and have that chrome plated, or even electroless bright nickel (only a fraction of the cost), it will look almost exactly the same.

1/4" copper would be able to be bent between your fingers, after annealing it whenever it starts to harden up.

John

75Plus · « **Reply #19 on:** May 25, 2011, 03:50:06 PM »

What about this one John? It is 1/4" OD X 3/16" ID and is stainless steel. Bent with a spring bender and ran past the buffer.

If you think you can use it PM me an addy to mail it to.

Joe

John-Som · « **Reply #20 on:** May 25, 2011, 05:21:19 PM »

Joe

That's a very kind offer but the shape is not really what I'm after. Sorry to look the gift horse in the mouth !

John

I am beginning to wonder if I was anticipating a problem that didn't exist. I will give it a go as you suggest and report back with the result.

John

DMIOM · « **Reply #21 on:** May 25, 2011, 05:28:42 PM »

Quote from: John-Som on May 24, 2011, 12:46:35 PM

.......I do have a pipe bending tool which works fine on the copper tubing that we use on our steam engines but I am looking to shape 1/4" thin wall steel tubing which I feel will need internal support. Suggestions anyone ?

John-Som

John,

Have a look at this bender thread by George Britnell, which, in to making the tool, also has some info on bending possibly similar material.

Dave

75Plus · « **Reply #22 on:** May 25, 2011, 05:48:44 PM »

Quote from: John-Som on May 25, 2011, 05:21:19 PM

Joe

That's a very kind offer but the shape is not really what I'm after. Sorry to look the gift horse in the mouth !

John

Would you care to share the shape you have in mind? Someone here is sure to have the solution.

Joe

Jasonb · « **Reply #23 on:** May 26, 2011, 02:39:14 AM »

I think this is the type of drill bit Bogs was suggesting

Pity they don't go small enough

DMIOM · « **Reply #24 on:** May 26, 2011, 03:05:44 AM »

John-Som - you could also cap one end, fill the tube with fine sand and then seal the top end before bending (either threaded or a plug of solder)

Alternatively (OT)

Quote from: Jasonb on May 26, 2011, 02:39:14 AM

I think this is the type of drill bit Bogs was suggesting

Pity they don't go small enough

nahhhhh - too simple and not enough

the answer is, in true MM style, a fusion of the earlier answers. What you want to do is, as per Bogs, bend the solid rod stock into shape, using stainless for your material. Dave Bluechip mentioned Bowden cables, but rather than using it as a bending spring, afix the requisite short stub drill bit to the end of the core of the Bowden cable, ensuring the lay (twist) of the cable is the same handed lay as direction of rotation of the bit. Then (and I'm sure Kenneth could help here) get something like the scan coils from the neck of an old cathode ray tube (TV tube) and drive them from a CNC rig, and because the stainless is relatively transparent to magnetism, if you apply enough power to the coils you should be able to steer the steel drill bit through the workpiece (NB don't try this at home if you've got a pacemaker!)

Dave

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Author Topic: Bendy pipes (Read 13608 times)