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View Full Version : Hexapod using 60mm (1/5 scale) Servos



mdenton
03-25-2008, 01:58 PM
Hi,

I have recently been designing a larger hexapod platform based on Multiplex Rhino 60mm size servos or 1/5 scale as they are sometimes known. This is very different from my usual style of hexapod, and has been designed with practical applications in mind, hence much of the aesthetic styling has been removed.

http://www.hexapodrobot.com/images/HexMUX60Cad02.jpg
http://www.hexapodrobot.com/images/HexMUX60Cad01.jpg


If built I estimate the body to be around 420mm long. In the picture of one of the legs you will see a standard size 40mm servo for scale reference. The tibia is 3/4" diameter tube and has a simple rubber foot contacts sensor attached, which would be replaced with something similar to my B.F.Hexapod foot.

Has anyone built, or is anyone building a hexapod with these size servos? if so I would be interested to know details of pay load and power consumption etc.


cheers,

Matt.

tom_chang79
04-21-2008, 09:47 AM
I've never built or played with the quarter-scale or 1/5-scale servos. I was considering to build one just for the sheer size of it when Lynxmotion comes out with the 1/4-scale brackets. But I was under the assumption that the 1/4-scale and 1/5-scale servos have a poor torque-to-weight ratio. I always thought that the standard servos, due to their popularity, had the best torque-to-weight ratio.

How are you doing with this project? Have you gone forward with it and built something up?

mdenton
04-21-2008, 11:49 AM
Well it is true that there are some 1/4 scale servos which specs are not much better than standard 40mm servos, however, what you need to remember is that the 1/4 scale servos have much bigger gearbox's and motors, and dissipate heat better. Therefore they are much better when it comes to continuous torque ratings and shock loads on the gear box.

The MUX servos I was thinking of using have a really beefy gearbox, along with 8mm output spline. Quite often the 1/4 servos achieve the same torque as the standard servos with less current consumption.

Matt.

JonHylands
04-21-2008, 12:32 PM
You should look into the RX-28 servo - its a little more expensive than the 1/4 scale servos, but handles more torque, and weighs a lot less...

- Jon

mdenton
04-21-2008, 12:49 PM
You should look into the RX-28 servo - its a little more expensive than the 1/4 scale servos, but handles more torque, and weighs a lot less...

- Jon

Those servos do look pretty good, I can't remember the size of them now, but I guess the point I was making is that if two servos are more or less rated at the smae torque, but one is smaller than the other, the larger servo will usually out last the smaller :).. At least thats been my experiance with 14 years of animatronic application, which is pretty demanding.

JonHylands
04-21-2008, 12:57 PM
If you really want to get into the overkill side of things, look at the RX-64. Even more expensive, but oodles of available torque, and still less weight than the 1/4 scale...

- Jon

Matt
05-05-2008, 01:04 PM
Okay, I finally found the servos I was thinking about. A REAL robot is made with some of these :D
http://www.vantec.com/ssps105.htm

I dare you! I double dare you! (Just because I'd love to see this bot!)

tom_chang79
05-06-2008, 01:51 AM
Matt Denton, I think I get what you are saying about the large scale servos... It's not just "torque" but "endurance?"

If you are interested in making a hexy out of the large scale but with the classic servo look, wait for Hitec to release their latest monster servo, the HSI-100.

For those that have the Spring issue of the Robot Magazine, this servo was mentioned in a little section towards the end of the mag. Check out the topic that I started on Lynxmotion's forum on this:

http://www.lynxmotion.net/phpbb/viewtopic.php?t=3864

The only draw-back is the +/- 40 degree travel. Not sure why it was speced like this, but the Robot Magazine claimes a 180-degree of travel. Conflicting information...

But I do agree with JonHyland about the RX-28. Gobs of power. But an RX-64 would be the king of hobby-size servos right now, and it's fully featured like all Dynamixels...

I would personally love to see a hexy with RX-64s. It would probably be able to carry your other hexys on its back and walk around... It's such a brute of a servo... :p