Repair a 1 inch wide by 1/4 inch thick by 14 inch diameter round cast aluminum clamp

[dansawyer]

The clamp is 1 inch wide by 1/4 in thick by 14 inches in diameter. It is in two halves hinged together. The closing mechanism is tangs or fingers with a 1/4 x 20 thread closing mechanism. The break is half between the hinge and the closing mechansim where the telescope is intended to be mounted. (my suspicion is it broke under the stress of holding the instrument. )
I have read about aluminum welding and that seems not the best solution in this case.
The clamp is primarily under tension when in use. My thought is to get some 1 inch by 1/8 inch steel strap and line the inner side of the clamp for 8 inches or so each side of the break. I would then screw flat head #6 or #8 machine screws every 2 inches along the strap.
Can anyone provide improvements to this idea or a better solution?
Thank you, Dan

 

[Weldingrod1]

Photo?
Ally has weak welds in general. You need to arrange more weld area than base metal area. Some alloys don't play well at all with welding.
Mechanical joining sounds promising...

Sent from my SM-G892A using Tapatalk

 

[Ulma Doctor]

a steel strap would be an improvement.
it is most likely more ductile than the aluminum and would definitely be more ductile than a weld

 

[Ulma Doctor]

polished 304 stainless steel would be an excellent material for a replacement, should you feel the need

 

[MrWhoopee]

What, no pictures? If you want specific help, we need pictures.

 

[brino]

If the picture in my head is correct, then this is a large band clamp that goes around the main tube of the telescope.
If so, I'd put the steel repair strap on the outside of the broken aluminum clamp.
Perhaps drill and tap the steel "scab" piece and countersink the heads into the aluminum on the inside.
It would be more visible, but would present a smooth inside diameter for the telescope tube.....with no "step".

-brino

 

[Mitch Alsup]

This sounds like one of a pair of clamshell clamps around the tube of a 12" telescope.
These are generally cast (pot metal) aluminum and welding is contraindicated.

What you might consider is:: drill and tap two holes on opposite sides of the break.
Make a steel strap with holes drilled to match.
Place several layers of typing/news paper on the telescope tube with scotch tape.
Epoxy the crack and the seam between clamshell and the steel strap.
Lightly clamp the telescope in the clamshell clamp while the epoxy sets.
When epoxy is hard, remove clamshell clamp and sand the stuck paper+epoxy off the inside of the clamshell.

The easy alternative is to rebuild the clamshell clamp out of baltic-birch plywood 3/4×3/4 should be strong enough.

 

[rwm]

If you add 1/8" to the inside of the clamp will it still function? A pic would be useful. Can you make an entirely new clamp half?
Robert

 

[dansawyer]

Below is a picture. The tube is 13 inches in daimeter. For size reference the vertical aluminum bar is 1/2 inch thick and 4 inches wide. Unfortunately the break is in a spot that would not easily allow straping on top..

 

[Alcap]

Are there screws from the inside of the broken band to the aluminum part ? Could the crack be moved to the middle of the aluminum and new holes drilled .