Hello J. Very nice mechanical work on that. Looks like you're
controlling it from a PC via a slave servo controller. What are you
using for a power source, for those of us who don't speak much
italian? What is the total weight so far?
- dan michaels
I have been working on my "Robo-One" style bot on and off for about a year.
Here is a link to a page with some pics of some of my stuff. It's not
pretty, but I'd rather spend the little time I have on the bot rather than
the web page. I'm on my third generation design, and I'm starting work on
the fourth generation. It might actually make it past the leg stage!
I agree about the new Robot Servo. It's really nice, but the price tag is
just too high especially if you need a bunch of them. My legs alone take
Did you see that sozbots is selling one (the "KHR-1") for about $1700? Still
a little steep, but it's right in the ballpark of what I'm spending to build
I'm planning to check out that servo the KHR-1 uses. I'm wondering how they
get by with the little 6V 600mah NiCd battery. I'm using a JR Extra 5-Cell
6V 1800mah NiCd pack. It does well if the bot just stands there, but when
it starts moving, the battery is drained in just a few minutes. In any
case, my final design will have a way to physically change to a fresh
battery. I'll bet that more robo-one contests are won/lost by
efficient/inefficient battery use. Easy to be the last man standing when
all the others batteries just gave out!
Hi Steve, someone on yahoo robotics club said he has a KHR-1, and the
batteries give him about 20 minutes of service, but 600 mAh is just so
small for 17 servos, so ????? I've been working on an 16-servo
octopod, and using 2300 mAh NiMH's, and it doesn't get much more time
Looking at your biped, it has some really nice mechanical work, like
Jodinsky's biped also has. I imagine all that metal rolls up the
weight quite a bit. My octopod weighs about 70 oz [2000 gm], mostly
for the servos, batteries, and legs, which have a very minimal amount
of metal on them. The aluminum deck is 14 oz, which seems like
something I can address regards weight reduction.
So, I'm thinking that so much metal on the bipeds must really run the
weight tab up very fast. We pretty much have the same power vs weight
vs battery problem here that the electric motor RC planes have.
- dan michaels
Dan, I'm planning to move to NiMH batteries soon for better power per
weight. I can't figure how they get 20 min out of 600mAh either.
Especially for 17 servos...
I don't have a scale, so I'm not sure how heavy mine is. I have 12 servos
on the legs and I'll have another 10-12 for the upper body. Weight and a
few other considerations is why I am working on a new servo bracket. I went
over to the CNC shop today and they had made a mistake so they are going to
re-do them. I hope to see them next week. The thing I like best about
Jodinsky's biped is that it is complete. If I keep improving things at this
rate, I'll never have a complete bot! I wanted lots of degrees of freedom
to work with, but in the long run it may be that removing a few servos will
make a big enough weight difference (and $ difference) to justify the loss
of a few DOF.
I used to have a scale, but it broke, of course. Now I take my parts
down to the post office and surreptitiously weigh them on the postal
scales when no one is looking ;-). Accurate to under 1 oz.
What I found was that you can easily overpower your servos as the
weight goes up, just by including the "minimal" amount of structure,
and all the bipeds seem to have a lot of metal on the legs/etc. Once
you get those legs together, with 3 or so servos linked in series, you
suddenly have a very long torque arm to deal with. Std servos working
against a 6" torque arm gives you only 44/6 = 7 oz to work with. And
one leg has to hold up the entire machine. Nice thing about multi-peds
is several legs can share the load.
- dan michaels
I'm using Hitec HS645MG servos with 133 oz/in torque at 6V. That's around
22 oz per leg to work with. The MG is for Metal Gear. They also have a
nice bearing in them. Absolutely necessary for the conditions a biped
subjects them to. Also the "Servo Saver" is a great gizmo, but gives up too
easily under my biped load.
Those little 44oz things barely even work for a good pan and tilt.
Lynxmotion is selling them but currently out of stock. I saw another site
selling them but the price was through the roof. I suspect that the price
will come down a bit when more distributors get in on the act. Guess it's
too new to be widely available.
Here's another supplier for the HiTech and other Servos. Looks like they
give a discount for purchases of 4 or more servos. Prices look pretty good
but they don't have a price listed yet for the HS-5995TG.
No servo included. Maybe we need to get all the Robo-One people to go in on
an order to E-MachineShop and have a bunch of brackets made up. I don't
think it would cost much to blast those out on a water-jet cutter.
I paid about $125 for 20 of the "servo shells" that I had made for my bot as
I just got the call that the CNC shop has my new design parts ready. They
only did a sample run of 4 or 5 and have not given me a price yet. If they
work and the CNC price is reasonable, I'll have them make up a bunch and
offer them for sale at a reasonable price.
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.