JR servos
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Does any one have experience with these? I am thinking of purchasing some
JR517s (ball bearing) to make a 12 servo hexapod. Are these suitable? I
can get a good deal on them, they cost $45 new, and I can get them for $30
new. These are Canadian prices. The typical american price is $27. I
believe that they are high quality, but am not quite sure. I'm not looking
for comparison on specs. I have found those already. As with any other
products, some manufactures will over rate their stuff and other will under
rate it, but I won't get into that now. I want to know if they are
reliable, durable, smooth (being ball bearing I assume they are), and long
lasting. CAn anyone offer some advice?
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JR517s (ball bearing) to make a 12 servo hexapod. Are these suitable? I
can get a good deal on them, they cost $45 new, and I can get them for $30
new. These are Canadian prices. The typical american price is $27. I
believe that they are high quality, but am not quite sure. I'm not looking
for comparison on specs. I have found those already. As with any other
products, some manufactures will over rate their stuff and other will under
rate it, but I won't get into that now. I want to know if they are
reliable, durable, smooth (being ball bearing I assume they are), and long
lasting. CAn anyone offer some advice?
________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
Comments
> Does any one have experience with these? I am thinking of
purchasing some
> JR517s (ball bearing) to make a 12 servo hexapod. Are these
suitable? I
> can get a good deal on them, they cost $45 new, and I can get them
for $30
> new. These are Canadian prices. The typical american price is
$27. I
> believe that they are high quality, but am not quite sure. I'm not
looking
> for comparison on specs. I have found those already. As with any
other
> products, some manufactures will over rate their stuff and other
will under
> rate it, but I won't get into that now. I want to know if they are
> reliable, durable, smooth (being ball bearing I assume they are),
and long
> lasting. CAn anyone offer some advice?
>
I've used JR ball-bearing servos (517 and others) for their intended
application (flying airplanes), along with other JR products, for
quite some time. I've always found them to be well-made, smooth, and
reliable. I've never used them in a robotics app, however.
Chuck Davis
I've used tons of RC servos over the years (for everything you can imagine
- including your application). A few points to consider:
1. No (major manufacturer) servo will last more than ~100 hours of
continuous running. Even with good mechanical design, this is an
unfortunate rule of thumb.
2. Servos will always fail. This can be assured by over loading them. In
your application this means weight is the enemy.
3. I've had good luck with JR servos. They seem to be more on par with
Futaba stuff and superior to Hitec and clones. Last year I did a project
that required several of their new high torque NES4721 digital servos, and
these worked well. We still had to replace them now and then, even at 130
oz/in! I think what you're considering is a good choice...
4. In an application that requires many servos (yours) I always obey a
basic rule. If I'm paying for them, I get a good quality basic model (ie.
Fut 148, 3003, etc.) and replace as required. If someone else is paying, I
buy the absolute very best (read: most expensive) and save myself *some* of
the maintenance headaches.
5. The hexapod I'm referring to had 12 standard futaba servos and they
failed with a certain regularity in fairly heavy use (TV series). These
things were, however being strained to their absolute limits - they could
only *just* lift it for walking. Again, if you can make your 'bot lighter
they will last longer. Maybe build the chassis out of plastic instead of
aluminum?
Hope this helps, Duncan
worst case, and IMHO one of the best choices out there (HiTec/RCD's FET
servos are up there too).
-dave
Dave Paton Motorola Advanced Technology Center
voice 847.538.7575 pager 888.773.6802
A13593@e...
>
Original Message
> From: ED Ward [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=H77MI4XiTKVONKynqV1fxmn8oCF73XT0MvFNrUzRAeV-8AYD911i8HR30qqef6C7gp3tVXy7rp9_J9hjZOQj8AcBhA]punk__rocker@h...[/url
> Sent: Sunday, July 16, 2000 11:41 PM
> To: basicstamps@egroups.com
> Subject: [noparse][[/noparse]basicstamps] JR servos
>
>
> Does any one have experience with these? I am thinking of
> purchasing some
> JR517s (ball bearing) to make a 12 servo hexapod. Are these
> suitable? I
> can get a good deal on them, they cost $45 new, and I can
> get them for $30
> new. These are Canadian prices. The typical american price
> is $27. I
> believe that they are high quality, but am not quite sure.
> I'm not looking
> for comparison on specs. I have found those already. As
> with any other
> products, some manufactures will over rate their stuff and
> other will under
> rate it, but I won't get into that now. I want to know if they are
> reliable, durable, smooth (being ball bearing I assume they
> are), and long
> lasting. CAn anyone offer some advice?
> ______________________________________________________________
> __________
> Get Your Private, Free E-mail from MSN Hotmail at
http://www.hotmail.com
way I figure, a little aluminum is lighter than a lot of plastic. I plan to
have the whole body based around on 1-1/4 inch piece of aluminum (so I can
fit some sub-Cs inside). On some of the flat pieces I might drill a bunch
of whole to further reduce the weight. Also I plan to use some springs or
elastics to offset the force the servo's need to exert to lift the bot.
Might it be a good idea if I "rotate" the servos? Obviously, the "lift"
servos will be the first to go, so swapping them with the "swing" servos
every 20 hours or so, could help equalize the wear.
>From: orthner@s...
>Reply-To: basicstamps@egroups.com
>To: basicstamps@egroups.com
>Subject: Re: [noparse][[/noparse]basicstamps] JR servos
>Date: Mon, 17 Jul 2000 08:47:55 -0400
>
>
>Hello Ed,
>
> I've used tons of RC servos over the years (for everything you can
>imagine
>- including your application). A few points to consider:
>
>1. No (major manufacturer) servo will last more than ~100 hours of
>continuous running. Even with good mechanical design, this is an
>unfortunate rule of thumb.
>
>2. Servos will always fail. This can be assured by over loading them. In
>your application this means weight is the enemy.
>
>3. I've had good luck with JR servos. They seem to be more on par with
>Futaba stuff and superior to Hitec and clones. Last year I did a project
>that required several of their new high torque NES4721 digital servos, and
>these worked well. We still had to replace them now and then, even at 130
>oz/in! I think what you're considering is a good choice...
>
>4. In an application that requires many servos (yours) I always obey a
>basic rule. If I'm paying for them, I get a good quality basic model (ie.
>Fut 148, 3003, etc.) and replace as required. If someone else is paying, I
>buy the absolute very best (read: most expensive) and save myself *some* of
>the maintenance headaches.
>
>5. The hexapod I'm referring to had 12 standard futaba servos and they
>failed with a certain regularity in fairly heavy use (TV series). These
>things were, however being strained to their absolute limits - they could
>only *just* lift it for walking. Again, if you can make your 'bot lighter
>they will last longer. Maybe build the chassis out of plastic instead of
>aluminum?
>
>Hope this helps, Duncan
>
>
>
>
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At 03:42 PM 7/17/00 -0700, you wrote:
>Thanks for the input. I am thinking of building my bot out of alumunum, the
>way I figure, a little aluminum is lighter than a lot of plastic.
This is true, but you do have a minimum structure that's required - the
thing has to have six legs...and most of the weight is in the 12 servos, no
matter how light you make the chassis.
>I plan to
>have the whole body based around on 1-1/4 inch piece of aluminum (so I can
>fit some sub-Cs inside). On some of the flat pieces I might drill a bunch
>of whole to further reduce the weight.
Yes, relieve it as much as you can, and start with as thin a piece as you
dare...
>Also I plan to use some springs or
>elastics to offset the force the servo's need to exert to lift the bot.
Be careful. If the servos are at or near their torque limit (40 oz/in) when
lifting, any assist will have to be overcome during 'steps' - further
torqueing the servo. A good design is to position the servos *on* the leg,
outboard of your hinge mechanism. This way, during the lift part of the
gait (I'm assuming a tripod gait) at least the weight of six servos doesn't
have to be lifted - they're on the 'planted' legs. With this scheme, during
each step you're only lifting *half* the servos.
>Might it be a good idea if I "rotate" the servos? Obviously, the "lift"
>servos will be the first to go, so swapping them with the "swing" servos
>every 20 hours or so, could help equalize the wear.
This is a good plan. I also thought of buying higher torque servos for the
'lift' position and using standard ones for the 'swing'...
Good Luck, Duncan