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Mechanics and Construction => Mechanics and Construction => Topic started by: noahc on June 14, 2009, 08:02:20 AM

Title: Am I doing my Servo Math Correctly?
Post by: noahc on June 14, 2009, 08:02:20 AM

Using this servo just as an example http://www.rcplanet.com/ProductDetails.asp?ProductCode=FUTS3104&Show=TechSpecs (http://www.rcplanet.com/ProductDetails.asp?ProductCode=FUTS3104&Show=TechSpecs)

Speed: 0.21 sec/60° @ 4.8V
Torque: 128 oz-in @ 4.8V (9.2 kg-cm @ 4.8V)

So lets say we have 5" wheels on these and we take 128/2.5  which equals 51.2 oz of torque per wheel.  If you had two of these they'd be at say 100 oz of torque so you could haul roughly 6lbs.

How do I calculate speed from there?  With this: Speed: 0.21 sec/60° @ 4.8V ?

Title: Re: Am I doing my Servo Math Correctly?
Post by: Razor Concepts on June 14, 2009, 09:18:40 AM

Unfortunately those values are the maximum values, so the servo can just barely move 128oz-in. With the speed, it is .21 seconds for 60 degrees when there is no load on it. If you put the maximum load on the servo, it will barely move.

Title: Re: Am I doing my Servo Math Correctly?
Post by: noahc on June 15, 2009, 10:25:58 AM

What is the best way to move 7-10lbs?  Large servos?

Title: Re: Am I doing my Servo Math Correctly?
Post by: sonictj on June 15, 2009, 12:41:08 PM

Quote

What is the best way to move 7-10lbs?  Large servos?

dc gear motors

Title: Re: Am I doing my Servo Math Correctly?
Post by: noahc on June 15, 2009, 12:58:05 PM

What is the most weight I can do realistically with servos? 3lbs or so?

Title: Re: Am I doing my Servo Math Correctly?
Post by: SmAsH on June 15, 2009, 03:58:01 PM

wells, it depends on the servo now doesn't it?
but with hobby servos it would be around that mark.
but a servo is just a dc motor with gears and a driver circuit...
sonictj is right, dc motors geared down will give heavens of power. ;D

Title: Re: Am I doing my Servo Math Correctly?
Post by: Metal Slug 2 on June 15, 2009, 03:59:17 PM

thats completely dependant on which servo you buy.  For example, the HS-311 servo can only support up to 49 oz/in (4.5 kg/cm) operating at 6v.  And then there are other servo's like this one: http://www.tonegawaseiko.co.jp/pro/e_pro02.html (http://www.tonegawaseiko.co.jp/pro/e_pro02.html)   which can supports up to 380kg/cm!!