want to make rock drill mast from aluminum

[burntside]

Looking for information on what type of aluminum to use to build a rock drill mast. I want too weld to pieces 0f 5" aluminum association C channel together with two pieces of extruded aluminum bars to form a box. A square tube will not work becaue I need the extensions of the C channel to slide the drill up and down the drill mast. The C channel will be welded together with the channels or extendion angles away from each other to form a square box with extensions on it.
What type of aluminum do you recommend I use 2024 or 6061 or other type of aluminum?
The aluminum mast will be 13 feet long. The drill and mounting bracket will weigh 420 pounds and travel via steel roller chain up and down the mast.
I plan on using aluminum association channel alloy 6061-T6:
5 inches wide with angles of 2.75 inches long, width of web 0.19 and width of angles 0.320.
Two of these would be welded together with extruded aluminum flat bar 4 inches wide and 3/8 inch thick.
Two of these flat bars, one welded flush with the out side of the two channel pieces and the other flat bar welded between the two channels about 1.5 inches in from the edge, for the steel roller chain to travel in.
I am wondering if the mast can be welded together without heat treating the aluminum after its welded together?
What do you think - would the mast be strong enough to hold together and not bend even if the mast is tiped to one side at a slight angle, say on a clock dial angles at a number 2 or 10, think it would hold together?
The mast would be mounted to a mini excavator stick where the bucket would mount, take the bucket off put mast on, two machines in one.
The drill is one of those hand held rock drills only weighs 66 pounds by itself but with the steel roller chain feed, hydraulic drive motor for the chain feed, mounting bracket of drill to mast and drill rod steel, it totals under 420 pounds with a safety factor included.
What ever input you can give me it will be greatly appreciated.
Mom & Pop businesses have to be creative to make a living, thats just the way it is.
I have a small dirt contracting business, right now really dead in the business field, have time to make this drill mast what I wanted to do for some time now.
So help me do it. Help me get-herrr-done.

[greywynd]

I see some 'challenges' with this idea.

Just so you have an idea of my background, I've owned a mini ex for almost 10 years, and ran them off and on for 10 before that. I'm also familiar with rock drills and drilling, there's a Pionjar in my shop that I've now owned going on 15 years.

I also do a lot (likely 75%) of my welding in aluminum.

The basic idea of your concept is sound I think, as I understand it you are wanting to use the mini to move and position the drill for drilling, then use the weight of the drill with a chain/crank(whatever) to regulate it's feed rate for drilling.

Aluminum has two major downfalls. First, when it's welded it tempers it, making it soft around the welds. In the case of 6061 T6 (common structural aluminum) it reduces the weld area down close to a T0. There really is no easy 'home shop' method of fixing this, other than some believe that time allows it to age and harden on it's own.

Second, when it's built and you're using it, the vibration from the drill will cause another issue, it will then harden from vibration, and eventually cracks will form. I suspect that you are going to have to bolt or pin this to steel at some point (never seen an aluminum excavator yet!) and that area, amongst others could be problematic.

I would suggest that you rethink it a little, and look at using steel instead. Size wise you can go to smaller shapes of materials, and likely retain the same strength for not a lot of difference in weight.

I'd be interested in seeing what you come up with, I hadn't thought of that option, but it's a great idea, might need to consider something like that myself.

[vicegrip]

I'm the opposite

No, experiance with rock-drills, but lots O' custom machinery.
There are more downs than ups, using aluminum.

Done lots of robots, fixtures, measuring devices.
Was sposed to be light, and easy to build.

Steel, my friend is your friend, clever use of appropriate
cross-section, reductions and ballances, of rigidity.

Post some schetches......interested, !!
VG

[Nac]

What size mini do you plan on mounting it on? I have this same set up but mine is all steel . I to would not recommend aluminum eved tough some manufactors build it that way. I tell you the vibration from a rock drill vabrates all kind of stuff loes locktire fasterns have failed hd rooler chain has failed. My feed beem is steel that is bolted to gether not weled.

[Spike]

Bolt it together

There is one brand of tractor trailer flatbeds that uses an aluminium frame and it is bolted together to get away from the downside of welding.