First Project

[krockhouse]

I am going to begin working on an autonomous turret, yes this will be my first robot build, and I have a few questions.

1. The goal is to have the turret be autonomous and will hold an airsoft gun, possibly two to shoot with.  We decided that stepper motors would be the way to go but we were wondering what size we should get.  I guess they are rated by torque so the question should be, what torque rating should we buy?  These stepper motors will control the pan/tilt.  Also where could we buy stepper motors, we would rather buy them at a store but we could buy online if we need to.

2. Are some stepper motors faster than others? We want the motor to be fast enough to shoot moving people.

3. Does the weight rest on the motor itself or is there another way to set it up so the weight does not rest on the motors? I have never stepper motors and so would appreciate any information you could provide for how to mount them to optimize the power.

[SmAsH]

what torque rating should we buy?

Well, this depends on the weight of the assembly itself, once you figure out an approximate weight then we can talk...

Also where could we buy stepper motors, we would rather buy them at a store but we could buy online if we need to.

Although im sure some stores have steppers, i would highly suggest buying them online.
For one, you can get a much larger variety than from a store. Also, the prices tend to be much cheaper.

Does the weight rest on the motor itself or is there another way to set it up so the weight does not rest on the motors?

The weight will be on the motors shaft. There are probably designs to help reduce the amount of weight on the shaft but in most cases it will be able to take it.

[Soeren]

Hi,

Does the weight rest on the motor itself or is there another way to set it up so the weight does not rest on the motors?

The weight will be on the motors shaft. There are probably designs to help reduce the amount of weight on the shaft but in most cases it will be able to take it.

The weight should _never_ rest on the motor shaft, as this will tear down the bearings. Axles mounted in bearings at each end (or close to) should carry the weight and the axles should then be driven from the motor.

[krockhouse]

The airsoft gun weighs 2.5 pounds with the ammo in it and we are using light scrap metal for the arms, so I would guess it would be around 4 or 5 pounds probably.  We are going to trim down the gun so it is just the basic components so it will weight slightly less.  Does that help at all? Do you have a specific range, I would like to  buy these motors quickly so I can start working with them.


 Also any hints on how to control them, any good tutorials?

[RoboGeek]

...
The weight should _never_ rest on the motor shaft, as this will tear down the bearings. Axles mounted in bearings at each end (or close to) should carry the weight and the axles should then be driven from the motor.

Actually the medium to large stepper motors (size NEMA 23 with 6mm shaft) have quite high ratings for axial and radial loads. About 6kg load rating if I remember right. So it would be perfectly happy with a load of a few pounds (2 kg) on it.

However I think it will need to be geared for good turrne performance, like 4:1 or 5:1 gearing, which means the load mass would be mounted on the gear shaft not the stepper motor shaft anyway.

[krockhouse]

I started searching for these motors and I found one site that sells them for around $40-50.  Does anyone know of a good site/store that they know gets good deals on stepper motors?