Building a Robot with Aluminum

We are in the fortunate situation to have been given access to a shop with MANY aluminum dropoffs for a period of time. During this time, we
can have any of the 6061 dropoffs that range from circular pieces to pieces of plate to square/rectangular pieces.
So with the bonanza standing before us, the question is what should we take before it disappears?
Considering that storage is always a concern, what are the "useful" pieces that one should salvage for later robotics construction?
What shapes, sizes and thicknesses do you find useful in your robotic construction?
Thanks for any insight.
TMT
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Too_Many_Tools wrote:

You don't say what size robots you are building.
For small machines say under 18" in length: 1/2" square bar stock is nice for making bearing mount blocks. 2" square bar stock is nice for mounting gear motors (bore, slit an edge and tap to make a heat sinking mount clamp). 1" - 3" round bar stock is good for wheel hubs.
If you have access to sheet metal forming tools 0.050" sheet formed into a shallow pan will make a pretty decent chasis for this size range. With no sheet metal tools, 0.090" - 0.120" sheet can be sawn directly into a base plate and hardware screwed to the top.
I built a machine in this size range for doing software development for a motor controller system I am working on. As I am finding that I enjoy the mechanical construction more than the software development, it was fun.
Good Luck,
Bob
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I deliberately did not say what size of robots will be built...since this source of aluminum has appeared and is available for a short time I feel that focusing on a certain size would restrict further projects.
I am looking for ideas as to sizes and shapes that are useful.
Thanks for your suggestions...anyone else build with aluminum?
TMT
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What's the real state in your garage? Why "any" and not a greedy "all"? :-)
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Because we are going to store this aluminum in a school storage area for use later by students....so we are trying to go about this in a logical and not greedy manner.
Nobody else?
TMT
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Too_Many_Tools wrote:

What kind of machine tools do you have to work with it? Personally I'd take anything that could be worked with the tools that I had.

--
--John
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Good question....we have access to several machine shops with the usual mills, lathes, drills, saws, etc.....so tools and tooling is not a concern.
We can't "take it all" because "all" represents many pounds and cubic feet of space used for storage.
What structural shapes are useful in the robots that have been built by amateurs?
TMT
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Too_Many_Tools wrote:

No it doesn't. Take whatever they'll give you, sift through it, then eventually sell the rest as scrap. You can make some additional money you can use for something else.
If you really have all those tools available, then there isn't a piece or size you can't use. 1/4" sheet could be used with a metal lathe or mill to turn down into any shape you want. But in any case, I'm with Padu in thinking if you don't have a particular class of robot in mind, answers to your question will be nearly meaningless.
-- Gordon
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Thanks for responding...
Yes...we really do have all those tools available.
Reality is that we can't take it all...not enough space for storage.
Politically is that we wish to have a continuing relationship with this source for the future...taking it all would not be seen to be wise.
Back to my original question...what shapes in aluminum are most likely to be used in building robots?
TMT
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Rectangular and square tubes can be used to build frameworks and also cut apart to use as right angle brackets or flat stock. So I would suggest these as your first choice.
A small amount of rods of various diameters are also often useful. But, for things like axles, it is cheap enough to buy small diameter rods.
If you look at the price of this stuff at MSC or Enco, you'll see that it is probably not worth that much agonizing. If you find you need some aluminum that you didn't select, it doesn't really cost very much. You'll also notice that the price is proportional to the weight so you might want to skew your selection towards heavier pieces.
Mitch
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Thanks for the response Mitch.
Rectangular/square pieces were my inclination also.
In robotics, I would expect the rectangular/spuare pieces to be of more use than something round.
For axles, I would expect one to use steel.
I am also guessing that plate and sheet goods would also be a good material to scourge.
One use for aluminum would be for motor mounts...any suggestions what the typical sizes of motors are used in amateur robotics?
Am I correct to assume that many amateur robots use an exoskelton approach towards construction....an aluminum skelton with an aluminum skin?
TMT
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L shaped pieces have been very useful for me. Great for connecting two pieces at 90 degrees, mounting motors, etc. Plates that are 1/8" to 1/4" thick are handy, too.
Maybe Google some robots that are made of aluminum and catalog those shapes ? Hope that helps a little more ... JCD
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Thanks for responding....yes, it does help.
I am surprised that there has not been more input on this subject.
Many times one finds surplus material at an attractive price and knowing what general geometric shapes, sizes and material type are useful can mean the difference between filling one's storage area with useless trash or useful construction material. Also considering that many robotic builders have limited shop resources means that the closer a piece of metal, plastic or composite is to the actual finished shape means less waste or effort processing of the part.
TMT
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Too_Many_Tools wrote:

I go back to my original comment that I think you're bound to get insufficient answers because you haven't provided enough detail of what you want to build. I'd never build a large robot out of channel stock because it wouldn't be structurally strong enough -- at least not without a lot of cross members that would add unnecessary weight -- but it's my first choice for a smaller chassis. In fact, when I wrote the first edition of Robot Builder's Bonanza no one I knew (and no book I had read) made extensive use of extruded aluminum, but it worked for those designs because of their size.
For a larger robot, say one for combat, I'd use plate aluminum and weldments, or go to steel. For a very small robot (under say 10 inches), I wouldn't use aluminum at all. In any case, the choice of material is application specific. Otherwise you can create engineering problems that are more costly to fix or work-around than if you simply purchased the right materials to begin with.
-- Gordon
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Thanks for commenting Gordon.
I do agree with your excellent discussion but reality is that many of us work with what we have available.
If a hobbyist comes across some surplus material (plastic, aluminum, steel), it suddenly becomes crunch time where one needs to decide what to take/buy/drag to the cave. Many times in surplus offerings you will have one chance to sample the plenty since others will soon partake of the offerings too. In my experience if one finds a surplus of material, you likely have only one chance to select what items you want. More than once I have stood designing a project that I had not planned on doing for years because the Surplus Gods have chosen to make that "ONE" critical component available to me at that moment. I am sure you are not a stranger to ham fests where one will find anything and usually not when you expect to....happens to me all the time. Walk away from that one special item for a moment and it will likely grow legs.
One last thought....I have always enjoyed your books and especially the sections that discuss the different materials that can be used in robotics.....excellent work.
TMT
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too_many snipped-for-privacy@yahoo.com (Too_Many_Tools) wrote in <1142041379.198382.84170 @j52g2000cwj.googlegroups.com>:

Here is an example of why it's hard to answer your question.
I say I want to build a robot .. no idea what size. and I come across a room full of motors of every possible size. I can only take a few.
how can anybody possibly advise which motors to take without knowing the size of your intended robot.
the guy that suggested taking the most expensive stuff had the right idea ... grin
mike
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Hi,

Here's the stuff that I've found that I use:
Most of the round stock I use is 3/4" and smaller. I occaisonally use larger pieces, but much less frequently.
For the non-round stuff in alumimum, I occiasonally use stuff bigger than 3/4" in the smallest dimension but not often. Angle & plates/sheets seem to be much more useful than large blocks.
Same goes for plastic. I like Delrin and HDPE (high density polyethelene). Sometime HDPE comes under other names like StarBoard.
I dislike UHMW. This stuff is very stringy and doesn't cut particularly well.
PVC is not too bad to machine either.
I find myself using a fair amount of sheet material that's 1/8" & 1/4" thick for plastics. I also pick up thin stuff (0.050 or thereabouts).
As others have said, alot of this really depends on what you're planning on using it for.
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"the guy that suggested taking the most expensive stuff had the right idea ... grin"
LOL...Yeah...I have used that stragedy before...the problem is many times ALL the stuff is expensive.
In the surplus world, many times you get just one chance at many specialized mechanisms that would cost thousands of dollars and hundreds of hours to make. Raw stock is a simpler problem but still the logistics of discovery, assessment, transportation and storage of materials still represents an investment in time and money.
My interests in robotics ranges from those of a few ounces to hundreds of pounds. This means materials and components of interest can range the spectrum of surplus.
While we are on the subject of materials, how do you store your inventory of metals, plastics, etc.?
TMT
Mike_in_SD wrote:

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Mike_in_SD wrote:

When in the situation of having to choose among freebies, run do not walk to Home Depot and grab their $18/hr immediately available truck (or if leaving for an hour will lose the deal, take your cell phone and dispatch a minion to perform this task), load it up until it groans, and then visit everybody you know dropping off however much stuff they will store for you, and leave what's left on the truck for whatever SOB rents it next <grin>.
--
--John
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gee, I just grab whatever I can fit, and when I cant fit anymore its time for a build session :)
there is a certian amount of experiance in knowing what kind of things will work for projects you are working on. One method it to create 'bins' if you will for your projects, if you find something that should work good for it, put it in the bin, when the bin has everything you need, simply assemble it.
I have a 400 square foot 'back burner' whats wrong with that?
http://eds.dyndns.org:81/~ircjunk/robots/robots.html
dan
J. Clarke wrote:

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