where can I get steel tubes tapered?

[hotponyshoes]

Oh you'd open it up to the larger diameter? Can't see that working easily for a home workshop on a long enough tube. I guess you would heat the tube in stages but wonder how such a long former would hold up remembering the expanded part is going to cool and shrink. I'm sure there's a trick to making that work but sounds difficult.

The op is only looking for 6" though..

 

[nickk]

Pat,your welcome to use my power hammer and forge,sounds interesting would be very rewarding too.

 

[Screwdriver]

The op is only looking for 6" though..

I thought that was 6 inches of taper on a two foot tube though.

 

[hotponyshoes]

I thought that was 6 inches of taper on a two foot tube though.

That would be about the perfect size, heat 6" on the end up, drop it through the hardy hole so it's sat on a plate on the floor,
Drive your punch on in.
Reheat to dull red, hold upside down, dunk the punch in water and it will drop right out.

 

[Screwdriver]

That would be about the perfect size, heat 6" on the end up, drop it through the hardy hole so it's sat on a plate on the floor,
Drive your punch on in.
Reheat to dull red, hold upside down, dunk the punch in water and it will drop right out.

Hmm. I remain skeptical. In my "forge" you'd be five foot up a ladder to reach the top of the 60 inches of taper+pipe+30 inch long punch with your head two feet through the roof!

 

[hotponyshoes]

Hmm. I remain skeptical. In my "forge" you'd be five foot up a ladder to reach the top of the 60 inches of taper+pipe+30 inch long punch with your head two feet through the roof!

Just dig a hole in the floor to drop the tube in

Maybe I'm not reading the op right but the tube is 30" long (that's less than 1m?)
I read it as 6" of taper within that 30"
Ie. 12" of taper leaving 18" of straight tube?

The punch could be a short as 7-8" as you could just weld a fuller style bar handle onto it

 

[hotponyshoes]

Actually, ignore all of my posts.
I read the 1st post again and looking at the photo the op wants them tapering in at the ends, not out!

You could still do it with heat and a punch but you would then have to do them as bits and weld them on afterwards..
Which might not be so bad if you cut in a leg joint..

 

[Matchless]

I will post the correct dimensions when I get a chance in the hope someone can do me a quick drawing so I can ask around the firms that offer tube manipulation services, I did ring a few but I think a quick email with a drawing will be a lot easier, my guess of sizes was quite accurate though, tomorrow is another day,

Thanks for the offer @nickk, we shall see, I saw something similar in Brads workshop the other day and he is 300 miles closer, first let me see if a company can help me for a decent price, if not we, the forum, will find a way!

 

[Agroshield]

It's not something I have tried on anything of any size but could you not get a bit of solid bar, grind/turn it down to the taper that you want for the ID of the tube to use as a former.

As I read his first post and his subsequent clarification of dimensions, the tube is 1/2" (12.7mm) OD at the small end and 2mm wall. That means the ID is 8.7mm (a little over 5/16"). That is a very skinny, delicate mandrel for the inside of the tube. Its thermal mass is very low so I wonder if heat transfer to the mandrel from the red hot tube would be an issue.

 

[hotponyshoes]

As I read his first post and his subsequent clarification of dimensions, the tube is 1/2" (12.7mm) OD at the small end and 2mm wall. That means the ID is 8.7mm (a little over 5/16"). That is a very skinny, delicate mandrel for the inside of the tube. Its thermal mass is very low so I wonder if heat transfer to the mandrel from the red hot tube would be an issue.

The narrow end of this is just under 8mm

I use that to punch holes in 1/2" thick hot steel all day with no problems.
I have a longer version somewhere that would be used to punch the first hole in a hammer head for the shank, again, no problems.

Heat transfer might be an issue but if anything, the issue will be the tube cooling too quickly rather than the punch/mandrel overheating.
Working at a decent pace would solve that, I would expect to be able to punch out a 6" length of 3-4mm wall tube in a single heat.

In fact, I would probably make the punch over length and taper it down more than required (7mm or so) then wack it into a bit of 8"+ tube.

That would allow you to quench the bottom end of the tube to stop it belling out and let you cut out the section you wanted to the perfect size afterwards.

 

[Screwdriver]

Welding a six inch section of taper onto the 24" straight is verboten from my understanding. In any case. if you were going to weld it, you'd cut a relief lengthways to form a conical section , cut and shut the taper lengthways.

These girder forks are a type of flexure. While they have some strength in their lattice like design and are an extension of a suspension mounting, they still have to be able to flex. I'm not a welder or a mechanical design engineer of any sort but the last thing you want to do is introduce a weld that cuts across a suspension strut that will flex. Amiwrong?

 

[Matchless]

If someone with cad skills could draw these up for me I would be very happy,
19.05mm od, 2.03mm wall, 550mm overall length, tapered each end for 150mm tapering down to 13mm od, and for the rear stand 25.40mm od 2.03mm wall, 320mm long tapering over the whole length down to 16mm od, ideally then staying at 16mm parallel for another 180mm making 500mm overall,

 

[tom2207]

I saw this and thought of you .

 

[Edward Teach]

You Tube - Tapered Tube Forming

This seems interesting - Tapered Tube Services

 

[8ob]

A lot of this oddball tube shaping is now done with hydroforming. I suppose in this case the smaller diameter tube would be pumped out to the larger diameter.

Bob

 

[RussH]

Hi Matchless, I know this is an older post but did you ever find a solution for the girder forks ?
I have the same dilemma for an old Triumph, if I could find / make the tubes I would rebuild.

 

[Seadog]

Renolds used to do them. A good friend had Manx swinging arms made by them around 15 years ago. Having said that, there's probably no-one left at Renolds who has a clue, now.

 

[tom2207]

I know Paul Brodie buys in tubes for pedal bikes all ready done , so they must be available some where ,, granted hes in the US

 

[Matchless]

The easy answer is no, I got some tapered tubes from a friend but they were not quite small enough at the bottom to go into the castings so I cut a slit out, squished them together down the slit, and fired up the mig welder, I am still alive so must be OK,

 

[RussH]

The easy answer is no, I got some tapered tubes from a friend but they were not quite small enough at the bottom to go into the castings so I cut a slit out, squished them together down the slit, and fired up the mig welder, I am still alive so must be OK,

Thanks, good to know, gives me another option. I've found a supplier of tube at 19mm od with 3mm wall, so should be able to machine a taper down to 16mm and maintain an acceptable tube thickness. I'm not worried about the extra wall thickness / weight - I don't plan to do much racing lol.
How did you manage to make the bend and keep alignment ? I'm thinking a simple jig is needed ?