$50 Robot Question-HS-311 servos strong enough to pull sega saturn

[WolfFire]

I was just wondering if the servos from the $50 dollar robot tutorial (Hitec HS-311) would be strong enough to pull an empty Sega Saturn cover. I removed all of the electronics (don't worry, I got it from goodwill) and I'm not sure if it will be too heavy for the HS-311 or not. It is under 2 lbs because my scale wouldn't turn on. How much can the HS-311 pull? I'll try to post a picture soon. (By the way, I don't have my servos yet, I ordered them yesterday.)

[pomprocker]

Check the HS-311 datasheet for torque, find out how much the sega chassis weighs, and then do the math 


And by when you say pull, what exactly do you mean? whats your setup?

[WolfFire]

I have 5 inch diameter wheels, which are going to be mounted on the front of each side. The rest of the sega is going to be dragging behind for the castor. I might put cd's (or a castor wheel) on the end to reduce friction.

[WolfFire]

Check the HS-311 datasheet for torque, find out how much the sega chassis weighs, and then do the math

Ok, I know this is a really stupid question, but how do you do that?
I get the weighing, and I know how to find the torque. But what math do you do.

[pomprocker]

Here is some specs for the HS-311

          Speed: 0.19 sec/60° at 4.8V
          Speed: 0.15 sec/60° at 6.0V
          Torque: 42.00 oz-in at 4.8V
          Torque: 51.00 oz-in at 6.0V

[ArcMan]

Here is some specs for the HS-311

          Speed: 0.19 sec/60° at 4.8V
          Speed: 0.15 sec/60° at 6.0V
          Torque: 42.00 oz-in at 4.8V
          Torque: 51.00 oz-in at 6.0V

So, (51 oz-in / 2.5" (the radius of your wheels)) X 2 wheels = 40.8 oz. of pulling force.

Whether that will be enough to move the load on a flat surface or not depends on the coefficient of friction between your load and the surface on which it is pulled.  Attaching wheels to your load will minimize its resistance to being pulled (the whole reason for their invention).  Note that wheels have bearing friction and rolling friction, so the resistance is not zero.

[WolfFire]

OK, thanks for explaining that to me. I am going to add castor wheels to the back corners so according to your calculations, I think it should work just fine. Also, thanks to Pomprocker for the specs

[Admin]

Use this to calculate robot wheel torque:
http://www.societyofrobots.com/RMF_calculator.shtml