small hub motors

Bob:

You might try to find a motor and hub at:

   <http://banebots.com/>

If you do not like the motor selection,
you might try:

   <http://www.anaheimautomation.com/>

I've never bought anything from them, but they seem to
have a fairly broad selection of motors.

-Wayne


Bob Smith wrote:

Wayne C. Gramlich wrote:

Thanks, Wayne.  I'm looking specifically for "hub motor"
not a motor and hub.  Hub motors are pretty popular for
bicycles and are reasonably prices but are too big for
this project.  Maybe there is just not enough of a market
for what I'm hoping to find.


thanks
Bob Smith

Bob Smith wrote:

Sorry 'bout that.  I never heard that distinction before.
When I Googled "hub motor" I got a whole bunch of hits,
so now I understand the difference.

-Wayne

Bob Smith wrote:

The best I've found so far is at http://www.goldenmotor.com/
Click on "Hub Motor".   More power and weight than I'd like
but the size and price are right.  I wonder if I can modify
these so the wheel is cantilevered and not on a fork.

Bob

Bob Smith wrote:

Their wheel chairs did not use a fork.  So I suspect that
there is some way to do it.  I'm not sure if it will work
with specific one you are looking at tho'.

-Wayne

A while back I was also looking for a low-wattage hub motor.  I also
came across goldenmotor.com who seemed to have the lowest wattage
ones. But, their lowest wattage is still 75 watts. As for ones not
needing a fork, the Model: HUB24S -- 8" Mono Shaft wheelchair motor is
the lowest power one, but, it is 180 watts.

Why do you want a hub motor? For me, I thought it gave the easiest way
to mount, and the best ground clearance for an outdoor application I
had.  But, in the end, there just weren't any low power ones that I
could find.  However, for your indoor application, other choices are
available.

Joe Dunfee

l o wrote:

  Yeah, this was my pick as well.  The problem is that two of
these and a battery would be 25 or 30 pounds.  I was hoping
for something a little lighter.



My former boss has MS.  He walks with case and even then has a
very uneven gait.  By "walks with a cane" I mean _everywhere_,
including from room to room.  The problem is that he would like
to brew a cup of coffee in the kitchen and take it to his desk
to drink.  One good hand and one good leg and carrying a cane
means he can not carry a cup of coffee (or much else) from place
to place.

He is a pretty good guy with a good sense of humor, so when he
asked if I could build a robot to help I immediately said yes.
He and I are both hard-core Linux guys which is a big help.  He
can do the high level coding, leaving me to the mechanical stuff.

The idea is to have the robot respond to voice command and to go
from station to station in his house.  We will use his desktop
computer for the CPU intensive stuff and use a Chumby for the on
board computer.  A Chumby is a well documented, low power Linux
computer.  We will use dead reckoning for navigation and will
use bar codes printed on 8.5-by-11 sheets for landmarks.  A web
cam can scan the area for bar codes and, using triangulation,
figure out fairly accurately where it is.  The nice part of bar
codes, web cams, and voice recognition is that almost everything
we need is off-the-shelf Linux software.

Our plan is to build a prototype first and then discard it.  I
will use some motors from a kiddie car that I salvaged awhile ago.
Wheels will be plywood with some 12 inch bicycle tires (but no
inner tube for now).   Ultrasonics for collision avoidance but
I'd like to get to stereo vision at some point.  Tail dragger to
begin but I'd like to get a balancing robot at some point.  We
will have fairly big wheels so a balancing robot should be easy
since we can keep most of the heavy items below the axle.

We'll use the Demand Peripherals BaseBoard4 for all the Linux to
hardware interfaces so this should be almost trivial.


This is probably more detail than you wanted.
I would appreciate any advice you can offer.

thanks
Bob Smith

Bob, why do you specifically want the motor to be a hub motor?

As for advice, i don't have any from real experience, but some
thoughts did come to mind that may ring true to you.  Keep in mind
that my comments are more in the category of brainstorming.

Weight; I would think that the goal would be to make a robot that your
friend can move around if necessary. Robots are known for getting
stuck, loosing power, and just plain breaking down. A good robot won't
do this a lot, but eventually it will.

Size;  You friend needs to be able to get around the robot if it is
stuck in the hallway. But, it also must be tall enough to be able to
set a full cup of coffee on it, while he is standing. And of course,
your friend isn't as agile as some, so these criteria are going to be
more restrictive than it might if you were making it for yourself.

Perhaps if the wheels will just easily free-wheel if it is powered
down. That way he can just push it out of the way if necessary. This
might solve some of the weight/size issues.

There certainly are a bunch of criteria that all are in a fight
against each other.  It would be very wise to make an easy mock-up of
possible dimensions, and weights.

As for a balancing, that tends to make me nervous.  Your friend is
going to have a harder time cleaning up after a mess than your would.
Sure, we have all seen projects showing off a 2-wheeled robot
balancing a tray with a beverage.  But, you are not a research
institute.  I think you might be better off sticking with something
very reliable.

A differential drive with a round base, and the wheels centered , and
then a 3-rd caster, has its advantages with turning around in tight
spaces. But I would also wonder about stability. If the house does not
have carpet where the robot will go, then you are probably OK.. But,
if not, then that 3rd wheel caster tends to cause the top of a server-
bot to move a lot during transitions.  Perhaps the robot should just
be made smart enough to know that it must go extremely slow when
transitioning to a carpet.  Many round differential steering robots
tend to tip back and forth , especially when they are made taller than
the base diameter. I suspect it is best to minimize this. I wonder if
it is better to not be a symmetrical round robot, but rather have the
drive wheels more forward, so that you have a more stable base.  The
task of turning around gets more complex to program, but people do it
for some robots.

Here is a link to one "Butler Bot", but I really suspect that it is
only practical without carpets. It is based on a IRobot Create. Note
that you can hack most Roombas, since they have serial connectors.
But, the all suffer from issues going over carpet.
http://blog.makezine.com/archive/2010/06/belvedere_the_butlerbot.html

This Toshiba prototype looks wonderful, but note that they are NOT
demonstrating with a cut of liquid!
http://www.switched.com/2010/03/12/wheelie-butler-bot-serves-dinner-lacks-witty-banter/

This one is interesting, but certainly limited to cans of beverages.
http://www.norrislabs.com/

I imagine one good form to consider is that of a serving cart. I came
across some round ones in a quick internet search;
http://www.accent-furniture-direct.com/Alfresco-Home-21-0850-AFH1234.html
http://www.accent-furniture-direct.com/Emu-ER6407-82-41-QS-EMU1172.html


Hope I gave you some ideas and stuff to consider.

Joe Dunfee

Joe Dunfee wrote:

   No really good reason.  The prototype will use motors taken from a
kiddie electric car.  These motors have a ring gear around an axle
that passes through the motor.  I need to find a wheel and hub that
will fit.  This is kind of a pain.  Bicycle wheels are made for a
fork mount and I'd like a cantilevered wheel.  A hub motor would
make this a lot easier, especially one made to be mounted on just
one side.



   Frederic does not have much upper body strength so a stuck robot
is a real problem, especially if it is also a heavy robot.  The kiddie
car motors have a very long gear train and will be difficult to move.
For the finished robot I was thinking of hub motors (which are easier
to move) and, don't laugh, a socket for a broom handle.  The idea is
that attaching a broom handle gives him some leverage to turn or pull
the robot.  The wheels are about 12 inches in diameter to get over a
floor/carpet transition.



  Right!  You know those 5 gallon buckets?  The prototype has the motors,
batteries, electronics, and batteries in the bottom of two of those.
The top bucket is removable.  He can put stuff on the top lid, in the
top bucket, and/or remove the top bucket.



   Yep,  12 inch wheels and small hub motors would work



   There are a lot of unanswered questions.  Will a two-wheel, tail
dragger work?  Is voice control (which Frederic got working last
night) really be the right way to control it?  Will big bar codes
and web cams be enough for localization?  Will the ride be smooth
and fast enough to be useful?



   Agreed.  Two wheels does solve the problem of getting pneumatic
tires on all wheels.  Also, if he really hopes to carry an open cup
of coffee then the top platform will have to be balanced or gimbaled
anyway.  If the weight is below the axle it will tend to be self
balancing.  But agreed, this is not a priority.



   Yes, it does need to go from floor to carpet.  We can put in a ramp
if required but I was going to use ultrasonics on the prototype  to
detect bumps.  I would like to play with stereoscope vision as a way
to detect open paths, bumps and for obstacle avoidance.  All of this
is still an open problem.


 > Many round differential steering robots

   The 5-gal detergent buckets for the prototype are not really round
but are kind of rectangular.  (I'll post a photo when the prototype is
done.)  Big drive wheels near the front and a caster on the back.  As
you suggest, stability may be a problem.



http://www.switched.com/2010/03/12/wheelie-butler-bot-serves-dinner-lacks-witty-banter/

   Yep, you have the right idea for what we're trying to do.  The Toshiba
one seems closest.



   You did, thanks!

says...

Don't make him hobble around the house to get a broom. Make the socket
fit the cane that he already has in his hand...

In article <67317809-1fb7-4734-94c0-9608d8b97922
@y11g2000yqm.googlegroups.com>, cadcoke5@gmail.com says...
 

How about a short/wide robot with a low center of gravity during travel
that can then lift a tray to service height? Think of something like a
jumbo roomba with a scissor lift. In the kitchen a voice command will
have it extend a tray up to perhaps 4 feet for the coffee mug. (Extra
points if the tray has a "cup holder" like in a car.) The 'bot then
lowers the tray for transport, drives to the desk, then on command
raises the tray/coffee.

A tall 'bot would shake coffee out of the mug moving over carpet and
abruptly starting/stopping. This bot would lower the tray/coffee closer
to a center of gravity. Plus the lift height could be commanded for a
person standing (lift to counter-top height) or sitting in a chair
(perhaps to TV-tray height) for convenience.

Uniden wrote:

This is a good idea but I don't know how to build something like
this.   Or where to buy it.


On a separate note, the idea of using the cane instead of a broom
handle is also really good.  I'll see if I do this.


thanks
Bob

McMaster.com has this;

 Item #2846T11 Compact Electric Lift Table 500# Capacity,
Adjusts 5" to 30" at 1 7/8" per second.
25" X 12" Table Size , $2,826.36

I imagine too expensive. Your experiments on the prototype will show
if it is necessary.  Human serving cars are 3" high, but I am sure
people go very slow if they are going over bumps. Perhaps there can be
a compromise in the height. Maybe if the height were 25", it would
still be acceptable height to put stuff on while standing, and stable
enough to do transition to carpet.

[note that I also started a new thread "Server Robot" since we have
strayed away from just the wheels so please direct future replies to
that thread]

Joe Dunfee