1. 2 months ago

    7517H

    Aug 9 Malvern,PA 7517H

    Having not been able to use the V5 motors yet, I wanted to find out how much weight a motor can carry. We have thought out the design and we will probably be using a 2 V5 motor drive. I'm aware that V5 motors are stronger, but they also have different internal gear ratios(rpm) as the V4 motors. In order to decide whether we will use 2 100 rpm motors or 2 200 rpm motors we want to how much weight each motor can lift. Thanks in advance!

    @7517H a single 200 RPM V5 motor has a stall torque of 2.1 Nm (or 18.59 in-lb). Assuming you use wheels with a diameter of 4", a 2 motor V5 drive at 200 RPM should be able to carry 18.59 lbs.

  2. lacsap

    Aug 9 Event Partner, V5 Beta Tester Massachusetts 9791[a-z]

    You can find the details about the motors on the VEX product page
    V5 Motors

    At the bottom of the page is a tab with the product specs and comparison with 393 motors.

    I hope this helps with figuring out your application.

  3. What would be most helpful is a torque-speed curve for the V5 motors. I seem to recall seeing one somewhere showing how the software limits the motor's action (instead of the old PTC method used by 393 motors), but I can't find the graph for it.

  4. rbenasutti

    Aug 9 Worcester, MA WPI

    @FullMetalMentor What would be most helpful is a torque-speed curve for the V5 motors. I seem to recall seeing one somewhere showing how the software limits the motor's action (instead of the old PTC method used by 393 motors), but I can't find the graph for it.

    You are probably thinking of this -image- from this page .

  5. @rbenasutti You are probably thinking of this ....

    Yes, that looks like it. Thanks!

  6. Joshua_L

    Aug 12 Answer Virginia

    @7517H a single 200 RPM V5 motor has a stall torque of 2.1 Nm (or 18.59 in-lb). Assuming you use wheels with a diameter of 4", a 2 motor V5 drive at 200 RPM should be able to carry 18.59 lbs.

  7. Joshua_L

    Aug 12 Virginia

    Also, friction will also negatively affect how much weight the motors can carry so make sure your drive has good build quality.

  8. @Joshua_L ... I like your thinking ... but a 2 inch wheel radius means the carry capacity needs to be divided by 2 ... also that is peak torque and that only occurs at and below 50% motor speed, so based on the peak torque clearly being flat below 50% run speed implying a built in clutch to limit peak torque. And not the scaling .... 100 rpm ... not 200... it seems odd cause the motors seem like they should run fine 2 motor drive at those speeds but who knows ... sorry man i wish i knew all the needed math but its been too long.
    I do know at NBN worlds our bot was 23-24 lbs on 6 motor 393 drive running turbo (240 rpm) on 3.25 wheels too my knowledge... but i have no idea what else to do other than run someone with v5 run some tests with minimal friction and please post the results here ... but my intuition says 2 motor 200 rpm on a 4 inch wheel should be possible around 10-11 lbs

  9. callen

    Aug 12 Braintree, MA, USA

    @theone1728 @Joshua_L ... I like your thinking ... but a 2 inch wheel radius means the carry capacity needs to be divided by 2 ...

    He did that, and then multiplied by 2 for 2 motors.

    @theone1728 also that is peak torque and that only occurs at and below 50% motor speed, so based on the peak torque clearly being flat below 50% run speed implying a built in clutch to limit peak torque.

    Yes, you don't want to actually handle this load.

    @theone1728 And not the scaling .... 100 rpm ... not 200... it seems odd cause the motors seem like they should run fine 2 motor drive at those speeds but who knows ... sorry man i wish i knew all the needed math but its been too long.
    I do know at NBN worlds our bot was 23-24 lbs on 6 motor 393 drive running turbo (240 rpm) on 3.25 wheels too my knowledge... but i have no idea what else to do other than run someone with v5 run some tests with minimal friction and please post the results here ... but my intuition says 2 motor 200 rpm on a 4 inch wheel should be possible around 10-11 lbs

    You're not driving the robot up a vertical wall. A generally robot won't require its weight's worth of force to move it about.

  10. Joshua_L

    Aug 12 Virginia

    @theone1728 but my intuition says 2 motor 200 rpm on a 4 inch wheel should be possible around 10-11 lbs

    Based on my math, 2 V5 motors at 200 RPM has a little more torque than 4 393 HS motors, which is roughly equivalent to 6 turbo 393 motors. My worlds ITZ robot was ~20 lbs (not counting the additional 3-4 lb mobile goal it had to carry most of the time) and was carried by 4 HS 393 motors and none of the motors ever stalled out, so I think it's safe to say that 2 200 RPM V5 motors can safely handle any robot around ~20 lbs in weight, assuming their drive has minimal friction.

  11. My only concern is the stall torque in proportion to the power out put of the new motors, in proportion to that of the 393s ... but yeah I'm saying the new motors definitely have the power but it might not have the torque without being clever.

  12. callen

    Aug 13 Braintree, MA, USA

    @theone1728 My only concern is the stall torque in proportion to the power out put of the new motors, in proportion to that of the 393s ... but yeah I'm saying the new motors definitely have the power but it might not have the torque without being clever.

    Just remember stall torque isn't torque in general. It's important but not all-governing. As long as you're not stalling the motors (or trying to start them under high stress), pay some attention to the output power, too. So long as it doesn't mess up what you need to do or there is just no need, adjust your gears so you're operating in the middle zone, where you get the best efficiency. Do as much of the gear adjustment as possible internally.

 

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