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Motor Mount and Wheel Kit with Position Controller on my new bot — Parallax Forums

Motor Mount and Wheel Kit with Position Controller on my new bot

Rural GeekRural Geek Posts: 17
edited 2013-02-12 08:43 in Robotics
I am just getting started in building a new bot its going to be stingray style. its going to be bigger and heavier. I am looking at around as a high guess around 50lbs or so. What I was wondering is would the Motor Mount and Wheel Kit with Position Controller part number 27971 be big enough to drive this bot with no problem? The bot will be driving on carpet and tile flooring.

Thank you for any help everyone.
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Comments

  • NWCCTVNWCCTV Posts: 3,629
    edited 2012-11-20 16:55
    For that price I would hope so!! If I could afford those I would have gone that route instead of the way I went but oh well, whatever works. Unfortunately they are out of stock right now. If you need HB-25's for them I have a few brand new ones for sale.
  • Tom CTom C Posts: 461
    edited 2012-11-21 05:41
    @Rural Geek,
    I believe that Ken once stated that the motor mount wheels could handle up to 50 lbs. I have a pair and they are very sturdy and are presently supporting around 35 lbs with no trouble. You might be able to find cheaper motor drives on eBay or Craig's list though.
    Regards,
    TCIII
  • W9GFOW9GFO Posts: 4,010
    edited 2012-11-21 09:26
    I am using the same motors on a robot that weighs about 80 lbs. The motors have no problem moving it around.

    I am currently awaiting a response from tech support regarding the motors running hot after being run for more than ten minutes while not under load. I think it is normal but I want verification that my use is "approved", especially since I plan to make other similar robots.
  • Matt GillilandMatt Gilliland Posts: 1,406
    edited 2012-11-21 10:33
    Welcome to the Forums Rural Geek :thumb:

    50# no problem.

    We did some internal tests about a year ago, and we were able to drive our machinist around with no problem. He weighed about 190#.

    That's NOT to say that the MMWK is rated to run at that load, but it did, although we don't guarantee it.

    The weak link (if you want to call it) that is our caster wheel kit. It failed during the test because of the machinist losing his balance and putting all of his weight on the front end of a Madeusa platform.

    We're currently out of stock because we're changing over the kits to include our new high resolution quadrature encoder (#29321).

    Should be in stock soon!
    The bot will be driving on carpet and tile flooring.
    Easy Cheesy... I drive mine in an open field in the dirt, grass, and mud. No problem-o

    -MattG
    PS: (you'll have to get in line, i get one of the new ones first ;-)
  • Matt GillilandMatt Gilliland Posts: 1,406
    edited 2012-11-21 10:39
    currently awaiting a response from tech support regarding the motors running hot after being run for more than ten minutes while not under load
    Yep W9, you're right, it's normal. (consider this your reply from tech support ;-)
    -MattG
  • W9GFOW9GFO Posts: 4,010
    edited 2012-11-21 12:30
    Matt Gilliland wrote: »
    Yep W9, you're right, it's normal. (consider this your reply from tech support ;-)
    -MattG

    Thanks Matt, my question to tech support also asks if my application is an approved use of the motors. I need to know because if it's not, then I need to source a different system for my customer.

    I also asked if the motors have protection from overheating.

    I need to make sure that the motors can drive around an 80 lb robot for three to four hours in an office environment. I have no idea how many of these I will be making but I am starting on the second one which will be designed with small scale production in mind.
  • Rural GeekRural Geek Posts: 17
    edited 2012-11-22 05:34
    Everyone thanks for the info.

    I figure that the robot will be pushing about 80lbs now with the 35ahr battery I will be putting in it. With the heat that you are getting off them W9 I will put a fan in it to help that. This kit seems the best way for me to build my first robot from scratch.

    Thanks for the help guys:thumb:
  • ercoerco Posts: 20,256
    edited 2012-11-22 19:42
    Any life tests on those motors? Prolly starting to get some serious use in the Eddie platform. I'm still leery of them since they're worm drive motors. Best thing about worm gears are compact, use very few parts & they are somewhat self-braking. Worst thing is constant rubbing of the worm, causing rapid wear and dreadful gear efficiency (compared to standard spur gears). I'd feel good about using these for intermittent motion (electric car windows) but less so for the main drive in an 80-lb robot. Noticeable heat buildup under a no-load condition in just ten minutes is hard to believe and a red flag for me. Are we talking warm or actually hot? And just because all the motors exhibit the same behavior ("that's normal") doesn't make anything right about it. Adding a fan just to cool the motors seems like a losing proposition.

    If I was building an 80-lb bot (which might end up a 100-lb bot), I'd look for a bigger gearmotor using spur gears. A higher voltage motor uses less current for the same power output, which would run cooler too. If you were making a 4WD bot, I'd suggest using four of my favorite $10 24V gearmotors (using a different wheel) which was just on sale for $3.50. Yes, for real!

    http://forums.parallax.com/showthread.php?117280-Nice-10-Gearmotor&highlight=%2410+gearmotor
  • W9GFOW9GFO Posts: 4,010
    edited 2012-11-22 20:09
    I don't recall the actual time it took to get hot. That's why I said "after ten minutes", it was less than fifteen though. Hot means too hot to hold your finger on.

    I don't have same reservations with worm drive motors since they are very commonly used in electric wheelchairs. However, I have noticed that for the smaller motors they tend to get hot quickly, not just the Parallax ones. At least some of the window regulator motors will shut down automatically when they get too hot. I still do not have an answer to whether or not the Parallax motors have any protection from overheating. They did say that 80lbs is outside the range that they recommend.

    If it turns out that the Parallax motors shut themselves down when they get too hot then I will continue to use them. If not, I guess I have to find another source.
  • Rural GeekRural Geek Posts: 17
    edited 2012-11-23 12:04
    erco Thanks for the info on the worm gear drive. I am also looking at a 24v ampflow motor to see. I am just unsure of how much power I actually need to move a bot like this. That is where the problem lies. My Bot is like the stingray style, only bigger. So its two wheel drive and a caster at the back.

    W9 I thought Matt ment they are not rated for a 190lbs. I'll have to keep looking around to figure out what I need then I guess.

    Thank you for all the advice.:thumb:
  • ercoerco Posts: 20,256
    edited 2012-11-23 14:24
    @Rich: How much current are they drawing at no load?

    Edit: just saw 1.5A @12V no load for those motors. 18W no load, no wonder they're getting hot. Put a light load on 'em and fry an egg! That's a lot of power any way you look at it. For comparison, those little gearmotors' no load current is just 50 mA @24V. Stall current is only 1A.

    In a mobile robot, motor efficiency and battery life are everything.
  • Rural GeekRural Geek Posts: 17
    edited 2012-11-23 14:59
    @erco Do you think that those motors are big enough for a 100lbs bot?
  • ercoerco Posts: 20,256
    edited 2012-11-23 16:06
    See? You're already up to 100# from 80#. :) Of course you could carry smaller batteries if you're using lower-current motors.

    No way with just 2 motors. Four, maybe. Six? Sure. Make a Mars Rover rocker bogie and you're good. :) Actually, your power requirements on a hard tile floor are pretty low. Carpet takes a bit more, but if you're 100% flat indoors, you don't need tons of stump-pulling power. Didn't you say this was a Stingray-style chassis? How big, size-wise? You'll want a nice big rubber ball bearing caster.

    The wheels on those little motors are not real strong. For a 15-20 lb, 2-motor robot they're OK. But plan to replace them for a heavy bot. My motors (got 'em LONG ago) came with different, uber strong gray/green wheels. Soild nylon or delrin. The newer ones have thinner black ribbed wheels. But there are tons of motors out there, look around before you commit $300!
  • Rural GeekRural Geek Posts: 17
    edited 2012-11-23 16:15
    @erco Thanks for all the help. I will definitely do some more research before I buy.:thumb:
  • Matt GillilandMatt Gilliland Posts: 1,406
    edited 2012-11-23 21:12
    Ok here's what I'm gonna do. I don't know if we've ever done a "continuous on" test - certainly I haven't under controlled conditions. First thing Monday I'm gonna set up a couple test motors and see what happens. More details to follow... Right now there's a little more pumpkin pie to be devoured...

    Gimme some test conditions you want to see covered...
    -MattG
  • W9GFOW9GFO Posts: 4,010
    edited 2012-11-23 21:40
    Matt Gilliland wrote: »
    Ok here's what I'm gonna do. I don't know if we've ever done a "continuous on" test - certainly I haven't under controlled conditions. First thing Monday I'm gonna set up a couple test motors and see what happens. More details to follow... Right now there's a little more pumpkin pie to be devoured...

    Gimme some test conditions you want to see covered...
    -MattG

    Sounds good. I'd like to see a time lapse video of you sitting on a MadeUSA while it continuously spins in place for a full 60 minutes. :)
  • ercoerco Posts: 20,256
    edited 2012-11-24 03:14
    W9GFO wrote: »
    Sounds good. I'd like to see a time lapse video of you sitting on a MadeUSA while it continuously spins in place for a full 60 minutes. :)

    +1. If it's 60RPM or better for the whole video, I'll buy a pair of motors, plus more pumpkin pie for Matt. :)
  • Rural GeekRural Geek Posts: 17
    edited 2012-11-24 11:24
    Matt Gilliland wrote: »
    Ok here's what I'm gonna do. I don't know if we've ever done a "continuous on" test - certainly I haven't under controlled conditions. First thing Monday I'm gonna set up a couple test motors and see what happens. More details to follow... Right now there's a little more pumpkin pie to be devoured...

    Gimme some test conditions you want to see covered...
    -MattG

    1st its the long weekend. There is turkey to be eaten. Everything else can wait till next week.

    If you are testing it. Could you try putting 100# on it and run it just above a resonable speed and see if it will do that for an hour on and an hour off and on again.

    Please..

    If you feel they take that kind of beating and still be reliable then I will take you word on it and go ahead and order a set for my bot.

    I need the motors to last at least a few years for this bot. I know the weight won't increase, but the run time might run as high as how long the battery holds out. It might get to that run time point for testing times. But it will be running in my house at a resonable speed to be safe, and on carpet and tile flooring.

    So I guess that is as close to my running parameters I can give.

    @ Matt. If you feel that these motors will fit the bill for my set up I'll take a set when they are back in stock.

    Thank you for all your advice for a rookie.

    Happy Thanksgiving.:smile:
  • Matt GillilandMatt Gilliland Posts: 1,406
    edited 2012-11-26 15:10
    I'd like to see a time lapse video of you sitting on a MadeUSA while it continuously spins in place for a full 60 minutes.
    I'm sure you would, but this old dog can't do that anymore W9 ;-) this is as close as I'll get...
    Everything else can wait till next week
    Right you are Rural Geek :thumb: - Since this IS "next week" check this out:

    Additional notes:
    WE DO NOT RECOMMEND THIS under any circumstances - this is an extreme test for what it was originally designed for, but it was fun to see what MadeUSA could do.
    This is me, plus two 12v,6.5ah SLA batteries, plus an upper deck, additional standoffs, the base platform, a couple of HB25's and a BS2 BOE. (Total load was approx 200# +/-)

    And after talking with our Sales Manager (JimC) - nobody here can recall ever replacing a single 'burned out' motor for any customer - I've damaged some, but only during "rough prototyping" episodes.

    The motor duration/heat/full-speed test is currently in process - will update that soon...

    -MattG.
  • ercoerco Posts: 20,256
    edited 2012-11-26 15:42
    XLNT video. Next, I want to be able to drive Matt around using my web browser. Which way to the loading dock?

    Actually, the Cye website used to have that feature. Anyone could log on and drive Cye around the office. That would be a cool Eddie implentation at Parallax so we could keep an eye on Matt, Jen & Ken.

    http://www.personalrobots.com/spycye/testdrive.html
  • Rural GeekRural Geek Posts: 17
    edited 2012-11-26 16:35
    @Matt Holy Smile dude I didn't figure on an answer till at least later this week. Thank you for your hard work, well it look more fun then work.:lol:

    Thank you for the info it works for me.
  • Matt GillilandMatt Gilliland Posts: 1,406
    edited 2012-11-27 08:42
    Test #2: Simple heat generation test of main drive motor under no load, and continuous duty @ full rated voltage for 7.5 hours.

    [video=youtube_share;y70SUkRWqIE] [/video]

    -MattG
  • Matt GillilandMatt Gilliland Posts: 1,406
    edited 2012-11-27 10:45
    Test #3: Sixty pound load test. Spinning in place, instant motor reversals, no PWM ramp up/down, full power drive from bench-top power supply.

    -MattG
  • W9GFOW9GFO Posts: 4,010
    edited 2012-11-27 16:14
    Good tests! How's it doing?
  • Matt GillilandMatt Gilliland Posts: 1,406
    edited 2012-11-28 09:25
    Good tests! How's it doing?
    Here you go, glad you asked :thumb:

    [video=youtube_share;NAk7GezvyAk]

    Additional test conditions:

    Ended up running just 10 minutes shy of 8 hours continuous operation, before it was turned off (intentionally - It was time to go home ;-)
    The Blue Plastic bumper (attached to my workbench) helped to keep it in the same spot for hours and hours because I did not implement any encoder feedback. Kinda like "bumper-bots".
    The constant "slinging" of the load back and forth added to the stress of the unit, but there was no noticeable degradation, in spite of this to the any parts of the machine at all.

    Unless you'all can think of something else (that I did not cover in these tests), I'd say this is pretty conclusive of the MadeUSA Robot Platform's reliability (with a 60# load).

    I'm convinced that, if the load were evenly distributed, and the terrain was flat, and you programmed the machine to accelerate and decelerate, that even larger loads could be accommodated. However, we're not going to suggest that your application won't push it beyond what it can handle - it's up to you to determine whether or not MadeUSA is capable for your application.

    Speaking for myself, I'm convinced that it'll carry this load reliably - and beyond - in fact, I'm gonna go off-road with my own machine this winter - mud and all :thumb:

    -MattG
  • Matt GillilandMatt Gilliland Posts: 1,406
    edited 2012-11-28 09:43
    Hey all -
    Another thought: It's interesting to note that the first test (static, full on motor) resulted in a motor temperature of about 170 degrees, whereas the fully loaded final test only produced a temperature of 120 degrees or so.

    The two variables that I can think of that might explain this are:
    1) Semi-intermittent on vs. full on
    2) air circulation because of machine movement

    But even with those variables, that's a 50 degree drop from a "test bench does nothing but spin in free air" to a "real-world, 87# (60# payload plus full MadeUSA base platform, batteries, etc.)

    -Robot Torturer
  • W9GFOW9GFO Posts: 4,010
    edited 2012-11-28 11:31
    That's good news. Now the question that remains is - what does it take to make them fail? And - how do they fail? Do they burn up, rendering themselves into paperweights or do they shut themselves down, to run another day?
  • W9GFOW9GFO Posts: 4,010
    edited 2012-11-28 11:38
    Matt Gilliland wrote: »
    The two variables that I can think of that might explain this are:
    1) Semi-intermittent on vs. full on
    2) air circulation because of machine movement


    If the motors were reversed every few seconds without ramping then it seems that there was no time that current was not applied, and at stall current for a moment every cycle. I can't see how that would be easier on them.

    Did you measure the temp of both motors or just one?
  • Matt GillilandMatt Gilliland Posts: 1,406
    edited 2012-11-28 11:45
    124 & 130 degrees at the time the machine was shut off - I think it's circulation through the air...
    -Dr. Thermo
  • Matt GillilandMatt Gilliland Posts: 1,406
    edited 2012-11-28 12:01
    what does it take to make them fail?
    Well, we could run them at elevated voltage/current, but that's not fair, because they would/should never be subjected to that in the wild. And since we just ran it in a circle for 8 hours with a total weight of 87 lbs. with a lower case temperature as the result, I'd say the "failure point" is significantly beyond where these tests took it.

    No warranties are implied by these comments ;-)

    -MattG
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