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Need help with servo motors

nboy22

nboy22

Diamond Member
I'm doing some research on building my own motorized pan/tilt head with 2 servos. I would ideally like have the servos able to hold up a load of 30lbs (larger production cameras). What are my options? It seems there are lots of RC servos out there, but I am unable to find any real clear information about servos that can hold up 30 lbs.
 
Leros said:
A servo won't be strong enough. I would look at some strong stepper motors.
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Ok cool I'll check into that. Thanks everyone for the info so far. I think I may have found some that are able to hold about 29.9 lbs axial.
 
why would you hold 30 pounds anyway? Balance the load properly on a good set of bearings and the forces will be in the inch-ounce range.
 
This is a major component of my Senior design project. We are using stepper motors, even though they are a pain in the ass.
 
skyking said:
why would you hold 30 pounds anyway? Balance the load properly on a good set of bearings and the forces will be in the inch-ounce range.
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I figured I would build it to withstand almost any type of camera. It's not so much the pan I'm worried about, but the tilting. Some of the cameras we use at my work are around 20-30 lbs with a battery attached to them
 
arkcom said:
Check out servo city. They have some designs that hold up to 50lbs. You could probably make something similar.

http://servocity.com/html/pt-2100_pan__tilt_system.html
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Yeah I saw that rig. It is a bit too expensive, but I really like the design. I think I read somewhere at some point they were selling it for $1000. I would like to know what kind of servos and what kind of axles (?) they are using. Not really sure if it is the servo holding it up, or some sort of smooth bearing helping out so that the servo doesn't have to do all the work when it is stopped.
 
nboy22 said:
I figured I would build it to withstand almost any type of camera. It's not so much the pan I'm worried about, but the tilting. Some of the cameras we use at my work are around 20-30 lbs with a battery attached to them
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But if it's balanced correctly, the servo is not moving 30lbs of dead weight. There are some large high torque hobby servos which will probably work fine for you, however, I am guessing that you can buy what you're trying to make for less cash.
 
SphinxnihpS said:
But if it's balanced correctly, the servo is not moving 30lbs of dead weight. There are some large high torque hobby servos which will probably work fine for you, however, I am guessing that you can buy what you're trying to make for less cash.
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panning isn't carrying the weight, but tilting sure is. even with panning the drive has to accelerate and decelerate 30 pounds. it goes without saying anything with plastic gears is going to break instantly.
 
The Boston Dangler said:
panning isn't carrying the weight, but tilting sure is. even with panning the drive has to accelerate and decelerate 30 pounds. it goes without saying anything with plastic gears is going to break instantly.
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Well, you're sure not an engineer of any sort.

If he balances the weight - that is, he puts the pivot points at the vertical and lateral center of gravity, the servos will take no force at all to turn except the rotational inertia, which is very very small.

All he needs is some smart engineering, and a couple continous rotation servos. Gear it down a bit and he's good to go.
 
Pulsar said:
Well, you're sure not an engineer of any sort.

If he balances the weight - that is, he puts the pivot points at the vertical and lateral center of gravity, the servos will take no force at all to turn except the rotational inertia, which is very very small.

All he needs is some smart engineering, and a couple continous rotation servos. Gear it down a bit and he's good to go.
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i'm not an engineer but i can read and spell. the rig you describe was already deemed too expensive.
 
FWIW we spent less than $300 on our mount that is also designed for a 30lb camera (though control circuitry and software is more). Our design centers the cameras mass on an axle on some pillowblocks/bearings requiring 70 newton centimeters. Like I mentioned before we are using stepper motors. It's nearly functional...
 
ussfletcher said:
FWIW we spent less than $300 on our mount that is also designed for a 30lb camera (though control circuitry and software is more). Our design centers the cameras mass on an axle on some pillowblocks/bearings requiring 70 newton centimeters. Like I mentioned before we are using stepper motors. It's nearly functional...
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what is driving it? an arduino?
 
The Boston Dangler said:
panning isn't carrying the weight, but tilting sure is. even with panning the drive has to accelerate and decelerate 30 pounds. it goes without saying anything with plastic gears is going to break instantly.
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I can hinge a 500lb door on a 1/4" wood peg. They make servos with metal (titanium even) gears, and larger than I suspect you suspect; like the size of your fist. But like I said, it would be cheaper to just buy a mount made for this purpose.
 
Whenever I see weights over 10lbs being moved it is usually being done with hydraulic controls not stepper motors. Steppers are not really designed to move large loads because of the way they are designed the motor winding tend to burn out quickly when you demand a lot of torque. Be careful on the design of the drivers for the motors, they can easily overload if your stepper stalls from the load.
 
Modelworks said:
Whenever I see weights over 10lbs being moved it is usually being done with hydraulic controls not stepper motors. Steppers are not really designed to move large loads because of the way they are designed the motor winding tend to burn out quickly when you demand a lot of torque. Be careful on the design of the drivers for the motors, they can easily overload if your stepper stalls from the load.
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It would have been nice to talk to you before we burned through a couple drivers. They were cheap though, so lesson learned.
 
Second the hydraulic recommendation. EHA (Electro-Hydraulic-Actuators) can scale large, have essentially unlimited overload capacity (can remain in stall position indefinitely) and are fairly quiet. Not sure if the application is noise sensitive since you're moving imaging equipment. If a mic is nearby it can be.
 
Rubycon said:
Second the hydraulic recommendation. EHA (Electro-Hydraulic-Actuators) can scale large, have essentially unlimited overload capacity (can remain in stall position indefinitely) and are fairly quiet. Not sure if the application is noise sensitive since you're moving imaging equipment. If a mic is nearby it can be.
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Cool, I'll check those out too. It is better for it to be quiet for sure. I could probably deal with some noise but I would prefer almost complete silence. What do you guys think about this? http://www.youtube.com/watch?v=9e4wnJrnuqU

What kind of motors are used to drive that motion control rig? I'm thinking I would need some motors like that, but on a smaller scale.
 
nboy22 said:
Cool, I'll check those out too. It is better for it to be quiet for sure. I could probably deal with some noise but I would prefer almost complete silence. What do you guys think about this? http://www.youtube.com/watch?v=9e4wnJrnuqU

What kind of motors are used to drive that motion control rig? I'm thinking I would need some motors like that, but on a smaller scale.
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You don't have to use steppers to get fine detail movement. You can use a regular motor with an encoder wheel of some sort to determine revolutions. If you use a fast motor and have it turn a tiny gear and connect that to a large gear then you can move some pretty impressive loads, you are converting the speed of the motor into torque. I see a lot of scanners and printers using this method to move the print heads or the scanning assembly.

encoder usage
http://www.hessmer.org/blog/2010/04...ncing-robot-–-motor-driver-and-wheel-encoder/

Encoder design program
http://www.societyofrobots.com/downloads/Encoder_Design12.exe

schematic_ServoMotor_Encoder.gif




The rigs in the video are a combination of electrical and hydraulic systems depending on the size needed.
 
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