1/2" diameter aluminum rod for short axles ?

    1/2" aluminum rod isn't a good axle material for a 35 pound
load.  Mild steel should work fine, and you can work it with hacksaw,
file, and drill.  Just oil your cutting tools, use drill bits rated
for mild steel if you need a hole, and don't let drills get hot.

    Avoid tool steel or hardened steel rod; you'll struggle
forever to cut the stuff.

    Paint mild steel; it rusts easily.

                John Nagle
                Animats

Thanks for the info !
JCD

What is animats ? I went to the web site of that name (.com). Is that you ?
Always curious to see what peoples' *real* jobs are !
JCD

   Yes.

   I was also the team leader of Team Overbot in the DARPA Grand Challenge.
We lost.

                John Nagle

you ?

COOL!

What do you think of 1/4" mild steel axles for 35lb bot ? Too little ?
Barely acceptable ? ( Last question on this topic - I promise! )
Thanks!

     Now you're getting close enough to marginal that the
alloy and bearings matter.  3/4" is certain to work.
1/4", you need to build up a test rig and load it up.

     Sawing through 3/4" mild steel rod isn't that
hard.  You need a vise, a hacksaw, and a pump can
of cutting oil.

                John Nagle

Why do you want to use the smaller
diameter?  If weight is the issue,
then consider using a hollow tube
rather than a solid rod.  A tube
resists bending better than a solid
rod for the same weight/length.

I use a 3/8" stainless steel tube
with 1/16" walls for the axle of
a 20 lb robot, and it works fine.
Stainless steel is harder to work
with than mild steel, but it is
stronger and it doesn't rust, so
you don't have to paint it.


You can cut stainless steel with a
hacksaw but it is hard work.  Much
better to use a lathe with a cutoff
bar.

When building a robot, I use four
materials for 99.9% of it:

1.  Stainless steel for axles, joints,
    pivots, etc.  Also for nuts, bolts,
    and screws.  I have learned never
    to use cheap zinc coated screws,
    they don't stand up to the constant
    assembly and disassembly of a
    prototype robot.

2.  Aluminum for the main structure.

3.  Acetal (Delrin(tm)) plastic for
    precision parts that don't have
    to withstand too much load.  Very
    easy to machine.  Comes in white
    or black.  I only use the black
    because it looks cool.

4.  Acrylic for panels.  Easy to cut
    and drill.  The edges can be
    polished with a propane torch.
    I use only clear acrylic, because
    I like to be able to see inside
    for loose wires or whatever, and
    I like the way it looks.

*Partly* just trying to reduce the complexity of having different size
pulleys, wheels, etc. for this and that.

*Mostly* just getting a feel for what works and what doesn't --- from the
pros on here !


I hadn't thought of that - good point!


All VERY good tips! They're going in my notebook!
Thanks !

Good info as always - thanks !