where to find an unusual channel or rectangular tube in aluminum

bryan_machine · Aug 26, 2015

I'm making a new cradle for a small boat lift. The brackets for the old cradle are either a channel, or a rectangular tube with one side cut off.

All of the material is aluminum.

What's unusual is that the old parts are 2.5" wide by 6" tall by 1/4" thick giving a sliding fit to standard 2" wide rectangular tube.

None of my local suppliers has any 2.5" wide by 1/4" thick material, either channel or rect tube, listed.

I am gearing up to cut 3" x 6" x 1/4" tube and weld it back together, but wondered if anybody here knows where to get 2.5" x ... tube or channel.

(I couldn't think a maker of boat lifts would have a custom extrusion made, but ....)

Milland · Aug 27, 2015

Are you concerned about loss of strength at the weld joint? And isn't there an increased risk of corrosion in the welded zone? Perhaps looking further afield for the right sized material is worthwhile, even with shipping costs. And there are custom small lot extruders, perhaps it's worth checking them out?

Fabworks · Aug 27, 2015

This is the closest that I could find.

Coast Aluminum
7066 S 188th Street - Kent, WA 98032
Phone 503.224.6061 - Toll Free 877.398.6061

or

Coast Aluminum
4740 NE 166th Avenue - Portland, OR 97230
Phone 503.224.6061 - Toll Free 877.398.6061

bryan_machine · Aug 27, 2015

Thank you Fabworks - I have been looking at Coast's catalog but somehow just didn't see that. Thank you again.

bryan_machine · Aug 27, 2015

Oops - actually, that won't work.

What Fabworks pointed out is 6" wide and 2.5" deep. I need 2.5" wide and 6" deep. Sigh.

re: Milland - yes I'm a little concerned - BUT - the boat going on will be quite light (only about 150#) and I can overbuild the bracket. And in any case the cradle above it has to be a weldment anyway.

By the way - all of the custom small extruders I've found (poor search???) don't extrude things that large.

Sigh.

Thanks anyway.

Fabworks · Aug 27, 2015

bryan_machine said:
Oops - actually, that won't work.

What Fabworks pointed out is 6" wide and 2.5" deep. I need 2.5" wide and 6" deep. Sigh.

That's funny.... After I posted, I thought: Did I get that backwards ??? I guess so.

Good luck anyway

thermite · Aug 27, 2015

bryan_machine said:
- the boat going on will be quite light (only about 150#) and I can overbuild the bracket.

Never mind aluminium.. for all the labour involved, even at twice that weight, that dasn't sound as if it even has to be METAL.

Fabworks · Aug 27, 2015

Coast does have a 2.5 1/4" square tube (sharp corners) that you could stuff inside your 3" x 6" rectangle.

JP Machining · Aug 27, 2015

The first question is are you making 1 or 1,000 of these. Can always get a custom extrusion made and for that size of an solid shape I would guess die cost around 1500-1800 and then the actual extrusion is probably like 2.25 or so a lb in 1k lb lots higher for smaller.

If just making 1 then keep searching or fab something to work and be within spec.

Scottl · Aug 27, 2015

Is there a chance that the original parts were bent from sheet on a press brake?

bryan_machine · Aug 27, 2015

making 2 of them - so yes tooling for extrusion is impractical

we are talking a bracket that sits on a tube and holds another member coss ways - the second member may well be wood, and in any case, has free dimensions

it is getting clamping over the outside of the existing 2x5 tube that is part of the base of the lift that needs close dimensions

I have notes confirming it is 6061 and the edges are quite sharp - seems unlikely to be made on a brake

I guess will go ahead and fab it

thermite · Aug 27, 2015

bryan_machine said:
making 2 of them - so yes tooling for extrusion is impractical

we are talking a bracket that sits on a tube and holds another member coss ways - the second member may well be wood, and in any case, has free dimensions

it is getting clamping over the outside of the existing 2x5 tube that is part of the base of the lift that needs close dimensions

Hmmm.. I have a third-party add-on for one of my aluminium ladders. Outrigger cross-bar to stop twisting. Its clamps are extrusions - not the same size you seek, 2" x 2" or so.

But you might find that what you need is also used on longer ladders. Or as a component of some other boatish, ATV'ish, 2-wheel-ish or RV trailerish or scaffolding clamping doo-dad.

Bill

Milland · Aug 27, 2015

With a lift that light, perhaps you could use regular 2.5 x 1/4 wall square tubing, and make a couple side plates or bent strap "loops" to engage the existing 2" wide material? Is there a requirement that the 6" extend the full length of these parts?

bryan_machine · Aug 27, 2015

There's no written requirement, I am just copying what was done before (and worked for 20 years) I want to avoid cannabalizing the existing clamps for several reasons.

The existing design has the clamp legs long enough to reach past the bottom of the support beam, and then have a binder bolt run through them. This allows for a lot of adjustability of spacing, which is a big win.

The 2.5" square approach means 2 welds to add "flaps", the cut down 3-by tubing means one weld in the middle.

I've also though about taking some 3by tubing, and cutting filler plates which I would weld to the inside (bringing the inside gap down to the needed 2") - now the weld is only holding a spacer pad in place - that might be the most sensible thing.

(All of this is in the air over a fresh water lake, so at least the most serious issues of salt water corrosion, etc. aren't relevent.)

Chip Chester · Aug 27, 2015

Sounds like the kind of thing that would be found in a trailer parts catalog. Not the extruded stock, but clamp-on parts that will fit those dimensions. Galvanized steel up north, but aluminum at the seashores.
Maybe Google up "aluminum boat trailer parts".

Chip

thermite · Aug 27, 2015

bryan_machine said:
I've also though about taking some 3by tubing, and cutting filler plates which I would weld to the inside (bringing the inside gap down to the needed 2") - now the weld is only holding a spacer pad in place - that might be the most sensible thing.

Suspect I'd have used linen-bakelite (ratholed) or cut up polypropylene or linear-polyethylene kitchen cutting boards.

Then counterbored rivets with washers.

But nah... that's far, far too sensible.

Cheating, even!!!

If yah got a pair, you'll mill the buggers from solid 'bill-it'..

Bill

Chip Chester · Aug 28, 2015

+1 on a visit to the kitchenware aisle for cutting boards, but I'd skip the hardware altogether. Buy thicker-than-needed material, cut oversize by 2", and route a recess in the middle so that the clamp holds the plastic captive with 1" "borders" on each side. No hardware to fuss with, and when whatever clamp is bolted on, it will be completely constrained with no dissimilar metal problems.

By the way, cheapie cutting boards made great "skates" for pushing around a 7000lb CNC mill over good-quality concrete floors.

Chip

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