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Hey all, I get messages all the time from people asking for help, tricks and
tips on building Robot Arms and Gearing Schemes.
I put this together for a fellow builder and I thought it may be useful to
others.
Enjoy, and please let me know if any of the below stated is in need of
clarification.
I tried to use common terms - explaining what I do by intuition is never easy.
====================
Basics:
On Joints and gearing-
Axle won't hold the weight or bearing point @ axle bow-
Well the trick lays with a few different schemes. When using axles and worm
gears, typically the lift arms channels the stress load through to the
axles. Causing them to bend of bow under the weight.
So when you encounter this, you need to decided how big the device will be.
At certain sizes, (small) the issue is not that bad. But start adding more
and more weight and the problem becomes significant.
Next step is to move to the gearing and the type of bearing used at the
articulation point.
Try using a z8 to drive a z40. The small size of the z8 resists the z40
backlash and is the best combo when looking for the drive end to bow as
little as possible.
Then there is another trick. Bind the Technic Beams you are using as the arm
structure straight to the z40 using pins. You know the extra holes on the
z40. Well pin a beam to those holes so you maintain the most contact
possible to help reinforce the structure you are moving.
Then once you pin the beam to the z40, now instead of the weight being only
channeled to the lift arm at the center of the gear. The weight is also held
by the z40 itself. Then with the aid of the z8 driving the z40, you'll
achive minimum backlash which also contributes to the axle bow.
Another, trick is to use Technic Turntables as the main bearing. All of the
joints on Jama and the Super Mech-Bot use Technic Turn tables as the main
bearing. Driven with a worm gear the Technic turntable is the way to go.
So all in all try to use a z40 as the lifting geat at the joint point. Then
drive it with a z8 connected to a worm set up.
Pin the Technic beams directly to the z40.
Try this. Grab a lift arm and a pin. Get a beam and a z40. pass the axle
thru the z40 and lock the beam together to the lift arm. with no additional
pins connecting the z40 and the beam, the axle will twist. with the z40
pinned to the tecnic beam the weight is shared between the lift arm and the
z40 itself.
You might see the set up at the top of the mantis' knee.
http://www.brickshelf.com/cgi-bin/gallery.cgi?i=40517
On the flip side (bottom pivot base) - a pic of a worm table set up.
http://www.brickshelf.com/cgi-bin/gallery.cgi?i=267225
Also at the elbow of Jama is the set up I am talking about. Actually the
elbow is the only place where a Technic Turntable is not used.
http://www.brickshelf.com/cgi-bin/gallery.cgi?i=218101
See the Clear Worm box in the ceter of the midarm just above the elbow...
See how it drives the z8 and z40? Then there is a z24 at the back end behind
the z8 to help re-inforce the z8 drive gear and keeps it sandwiched against
the z40.
About the gearing down. Get a High RPM 9v Motor. The put a z8 on it. Mate it
to a z24 and repeat the process a couple of times. The end output with at
least 2 or 3 stages of z8 to z24 gives you high RPM with good torque but
slow output. This can be modifyied depending on what stage you end off on.
That is to say 2 stages of z8 and z24s has less torque and more speed then a
3 stage. Try out the stages to see what output is best for your end output.
This is tough to explain, but just try a z8 to z24 then repeat the set up a
couple of times and see what the speed and torque ends up like.
There are other ways using z8 to z24 then to a z40. Lots of torque!
Keep in mind that the z16 is best when used to transfer power rather than to
be used in a gearing setup. Since the z16 doesn't mate well with other gears
except using two z16s together. Jump gaps, send power from one brick level
to another using two z16s. Try not to use them in a gear set up, only when
you need to transfer power.
Hope this all helps. I have learned many aspects of Technic folmulas during
my building days.
Good luck, please let me know if you need clairification or additional help.
e
http://members.aol.com/mylegomaster/
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Message has 1 Reply:
 | | Re: Robot Arm Help - Gearing Techniques - FAQ
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| Hey Eric, good stuff! I've XFUT lugnet.faq so Cary is aware of it and can consider it for inclusion in the overall FAQ... (he doesn't always see every potential FAQ if you don't crosspost there, IIRC) Thanks for sharing. Because the quoteminder is (...) (22 years ago, 31-Jan-03, to lugnet.technic, lugnet.faq)
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