View Full Version : Sleeve insert question.

12-09-2014, 01:34 PM
Hi folks,

If one wanted to create a disassembling joint between two bits of tube of the same size by use of a "sleeve insert", how far up each tube does the sleeve insert need to go in order for the strength not to be compromised?

Assume one end of the sleeve insert is rose-welded into one of the outer or main tubes and the other end is a snug "push-fit" into the other tube with internal crush-tube(s) and bolt(s) or a pinch-collar.

Is there a formula e.g.inserts must be embedded "X" times the diameter of the tube to be joined?

At the moment it is just an idea for a trike that can be broken into 2 pieces. The alternative is a folder of course.

All answers treated in the strictest confidence. ;-)

12-09-2014, 02:37 PM
Dan, standard repairs to airframe:


should be good enough for your bicycle as well?

This is for permanent repair. If you wanted to slide things in and out on one side than I would go at least x3 tube dia (preferably more) on both sides.

12-09-2014, 04:30 PM
Hi Danny

what you haven't said is where the joint will be. I found out with the transportable the force on the front boom on a downward push can exceed 200 lbs. and the joint could twist eventually I used 2 clamp nuts on the outer pipe and a second tube inside the inner tube to ensure it does not crush , It has about 5 inches inside the tube which is the equivalent to double a seat pin in a DF frame .

regards emma

12-09-2014, 06:15 PM
Thanks Chris & Emma,

IF I do this instead of a "fold" then the joint would be just aft of the Cross-boom where the tube returns to horizontal.
So, if 3 x diameter were engaged on either side then the sleeve would be inserted 5" either end? Wow! That's a long sleeve.

Looking at the split-frame option of the "Thunderbolt" from Rick Horowitz (I bought these plans) I see he inserts the rear-end section of 1 3/4" tubing (when doing replaceable 20" or 26" wheel options) about 5 and a half inches into the forward section of 2"tubing of his main beam assemblies and fastens with pinch collets on the main tube; so this bears out the 3 x Dia measurement.

The sleeve I made (as a test to see if I could make one at all) was only 6" long, but extending the process by another 4" should be no trouble.
I wonder if the rearward insert were to be rose-welded in 8 points around the circumference of the host tube (2 rings of 4 welds offset by 45-degrees) if this could be shortened a bit?
This is the fun stuff, trying out ideas and experimenting.

Thanks again.

12-10-2014, 02:14 PM
Still playing with this as a concept/method and I thought I would try to weld the inside of the sleeve along the seam.
Wow! what a difference, not at all successful in fact it was awful. it just did not want to weld properly.
Same settings and switched back to the outside of the sleeve and ...perfect welds.
I wonder why? Welds don't like performing in the dark? I thought most ERW tube was welded from the inside anyway.
Very strange.

12-10-2014, 03:04 PM
Just curious: HOW are you welding the inside of a 6" long tube?? did I read that wrong? What diameter is the tube? MIG/TIG/STICK or something else? I can't even imagine a way to get my welding gun nozzle 3" into round tube unless it was tube larger that I would ever want on a bike frame.


12-10-2014, 04:20 PM
Just curious: HOW are you welding the inside of a 6" long tube?? did I read that wrong? What diameter is the tube? MIG/TIG/STICK or something else? I can't even imagine a way to get my welding gun nozzle 3" into round tube unless it was tube larger that I would ever want on a bike frame.


You don't really weld inside the tube. You drill holes on the outer tube, then fill in the holes when the inner tube is inserted. You can also weld the ends and grind smooth. It's called rossetta welding. The filling of the holes causes the outer and inner tube to become attached.

Hope that helps clarify.

12-10-2014, 06:16 PM
Ahhhh got your interest :-)

The tube/sleeve I was playing with is 1 &9/16" Diameter and therefore my mig torch can reach in from either end about 2 - 3 inches, so that's "how".

The sleeve had already been welded from the outside in a continuous seam along the cuts I had made to remove 10mm of material from the 1 & 3/4" tube I had started with.
This had then been ground down with a flap disc to show a smooth round tube that would slide (with difficulty) into a section of 1 & 3/4" tube.
The attempt at welding on the inside was to add material/strength to the seam thus created.

Does this make any sort of sense now guys?

12-10-2014, 07:33 PM
No, it doesn't
There should be no need to do any welding inside, assuming your welder settings are correct and you have proper penetration.
How can you reach inside more than about 1/2" is beyond my powers of imagination - you are supposed to maintain certain angle between the nozzle and your weld, otherwise the results will be mess.

12-11-2014, 03:35 AM
That explains the "mess" then. :-)

The outside is welded ok. The very ends of the seam to the point of melt-back of the base-metal.
I guess I was trying to gild the lilly a little (in error).


12-11-2014, 06:06 PM
You have enriched my life beyond bounds Mr B,
A rosette weld indeed,and ignorant me calls it a puddle weld !!!!
Or rose weld as Dan calls it
So now I will do my puddle welds and think" Shall I compare thee to a summers rose"
Hmmm, possibly not

12-11-2014, 07:30 PM
:) puddle, plug, rosette weld
any other names?

12-11-2014, 07:44 PM
I am sure that there are purists and pedants that would argue the toss on the precise nature of each as well as the names and the spellings, we all know what we mean in general terms.

On another note...
Who is "General Failure" and why is he reading my hard drive? ;-)

12-12-2014, 03:23 AM
You did ask!
Just to prove I do read sometimes.
Steve G

But I think plug-weld is the more common name

12-12-2014, 03:32 AM
General Failure is closely related to Sargent Major Sargent, whose son is a police officer , Constable Sargent, and a distant relative of Major Disaster.
As to why he's reading your hard drive---I didn't know he could read anything!
Steve G

12-12-2014, 10:53 AM
Plug welding is quite easy to make look good but can give a poor result from the point of actually welding the two bits together. It's very easy to get a weld pool beautifully filling the hole but with very little penetration to the inner piece. It's a technique used a lot in home automotive panel repairs. Don't use holes in the outer that are too small and ensure you spark up on the inner piece not the outer.