Motor sizing

[asid61]

Originally Posted by mreda

So this instead?
http://www.andymark.com/Motor-p/am-0255.htm

That's the one.

[EricH]

Originally Posted by asid61

Good to know you have somebody to work with, that makes me feel a bit better.
775pros could work, but because of their smaller mass you may face heating issues if you run this thing for a long time. CIMs are much safer and only cost slightly more (and have more reliable stock).

VEX did some tests on the 775s and published the results. Short version, under some of the test conditions they only got about 9 minutes of continuous operation (I want to say that was the max power test), after which they needed a new motor. EDIT: http://motors.vex.com/775pro--compare to http://motors.vex.com/cim-motor

Fan-cooled motors don't take stalling very well, which is where you run into a lot of the heating issues (drivetrains tend to stall a bit). CIMs... Can't say I've ever seen one of those smoke when used in an FRC-size robot's drivetrain.

[roboruler]

I’m going to be honest here. You are asking a lot of questions and it really seems like your knowledge in robotics is lacking. I am somewhat surprised that you received a grant from your college for a robotics research project without knowing that you need to use gearbox on a motor to increase the torque and reduce the speed and you don’t even know what a motor controller is.

Before you make any more design decisions, you really need to take a step back and decide your design requirements.

For example you mentioned tracks, do you need really need tracks or will wheels suffice.

How fast does this robot need to travel, what terrain does it need to cross, what range( battery capacity) does it need to have etc.

Another thing to consider is will the grant be large enough to be able to afford the necessary components, wheels represent a huge weight, complexity and cost saving over tracks

[Knufire]

Originally Posted by mreda

My best reference is someone who is young and doesnt really look at the dollar signs, this is just me getting another guide as well as to help me understand what I am doing rather than just taking advise and nodding blindly.

In terms of being able to handle the load though, would 775 pros motor and gearbox and SPARK motor controller theoretically work?

http://www.vexrobotics.com/217-4347.html
http://www.vexrobotics.com/vexpro/mo...reduction.html
http://www.revrobotics.com/product/spark/

thanks again guys

Strictly speaking, any motor can move any load. It's just a quesiton of how fast.

In terms of "handling the load", these are the factors you'll need to identify:

• How fast does the robot need to move?
• How much weight is it carrying (you already answered this)?
• A bit more about the geometry of the drivetrain (to estimate how much it's going to scrub/fight itself when it tries to turn)
• The material of the tread surface
• The surface it's driving on

The first question will identify the speed of your drivetrain, and the others help answer the question of how much torque you'll need the drivetrain to output. Multiply these together, and you get how much power you'll need in your drive; that'll allow you to pick an appropriate motor and gearbox for the drive.

[Lireal]

Originally Posted by mreda

just a question what is the purpose of a motor controller? and the gearbox will allow the independent movement of the two motors or would I need two of them?

To provide varying amounts of electricity to the motors, and to make them turn on, you will need a motor controller for each motor you use. A gearbox is just a set of gears packaged together that will reduce the speed of the motors' output while increasing the torque. If you use the gearbox I linked, you will need one gearbox, 2 motors, and 2 motor controllers for each tread.

[Knufire]

Originally Posted by mreda

just a question what is the purpose of a motor controller? and the gearbox will allow the independent movement of the two motors or would I need two of them?

I'd definitely recommend that you call up Andymark. They have a phone number listed on this page here: http://www.andymark.com/Contact-Us-s/177.htm You should be able to speak to one of their engineers and they'll help you spec-out everything you need from their inventory for a one-stop shopping experience to finish up this project.

[Ether]

Originally Posted by mreda

It doesnt have to go fast but when maxed out it will need to lift 100-150 lbs.

Lift? So you're not asking about drivetrain motors, you're asking for motors to power a lifting mechanism?

To select a motor (or motors), the first thing you need to do is determine the power required.

So... how high do you need to lift the 150 lbs and how fast? That's the info you need to estimate the power required.

[mreda]

Originally Posted by Ether

Lift? So you're not asking about drivetrain motors, you're asking for motors to power a lifting mechanism?

To select a motor (or motors), the first thing you need to do is determine the power required.

So... how high do you need to lift the 150 lbs and how fast? That's the info you need to estimate the power required.

lift was the wrong word. It just needs to be able to hold and move 150lbs