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Parallax's 12V Modular Wheel and Motor Mounts - Feedback Requested!

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  • DgswanerDgswaner Posts: 795
    edited 2008-05-17 12:59
    my bot is meant to have one of those stainless steel garbage cans for an exterior so these wheels will look better than what I'm using. I do intent to make it look less like a garbage can on wheels....
    Whit can you do me a favor, I'm curious to know if I'm going to need to make any serious changes, I'm hoping that all I need to do is add 2 holes per motor and I'm done, but my luck never really works out that way,
    can you tell me the measurement from the out side of mounting block the the far side of the motor (width of the space required on the bot) and height of the bottom of the mounting bracket to the bottom of the wheel, how far off the ground will it be? Thanks

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    "A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

    DGSwaner
  • WhitWhit Posts: 4,190
    edited 2008-05-18 12:14
    Dgswaner said...
    Whit can you do me a favor, I'm curious to know if I'm going to need to make any serious changes, I'm hoping that all I need to do is add 2 holes per motor and I'm done, but my luck never really works out that way,
    can you tell me the measurement from the out side of mounting block the the far side of the motor (width of the space required on the bot) and height of the bottom of the mounting bracket to the bottom of the wheel, how far off the ground will it be? Thanks
    Dgswaner,

    Mine are still unassembled. I am gathering other parts. I'll see what I can do though.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-05-20 14:53
    Whit said...
    O.k., I just re-read the the whole thread. I think I may build a simple prototype like Chris' just to work out the kinks. Then I will know that everything works before I move on to a final more asthetically pleasing design.
    Whit,

    ·· My prototype worked very nicely...It was very smooth and agile, as well as having a tight turn radius (being able to turn in place).· Now, if you're planning on using it outdoors (most customers will), you'll want better casters...Mine took a beating outside and stopped turning easily after some time.

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    Chris Savage
    Parallax Tech Support
  • ZootZoot Posts: 2,227
    edited 2008-05-20 18:19
    From the docs:
    said...
    ~150 RPM @ 12.0 VDC, 1.50 A, no load
    ~190 RPM @ 14.5 VDC, 1.60 A, no load

    Is there an estimate of current at stall? I'm saving my dollars for a pair of these, but I won't be using the Parallax motor controllers (for a variety of reasons) and I want to make sure my drivers are matched to these motors properly.

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    When the going gets weird, the weird turn pro. -- HST

    1uffakind.com/robots/povBitMapBuilder.php
    1uffakind.com/robots/resistorLadder.php
  • DgswanerDgswaner Posts: 795
    edited 2008-05-20 19:38
    Definition of torcher: Getting a set of these at work and having to wait for 4 hours until I can play with them. very impressed! I can't wait to Try them!

    Hey zoot, if you can get these to stall something serious just happened to your bot! my bot wanted to climb the walls before it wanted to stall, I did have them geared down tho.

    I'll test it out and see about getting you some numbers when I get home.

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    "A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

    DGSwaner
  • ZootZoot Posts: 2,227
    edited 2008-05-20 21:10
    "Stall" current refers to the peak current surge required to get the motors (and the platform) moving from a still position. This current snap is often much higher than the "continuous no-load" or "continuous load" current. For example, on one of my larger 'bots, each motor (similar in size it seems to the Parallax motors) peaks at nearly 9 amps when starting, then immediately settles down to about 2.1 amps under normal load. "No-load" with the wheels in the air at full speed is about 1.1 amp.

    Not necessarily the same as "stalled out because I'm stuck on something" -- in that case, if the motor is still being torqued, you will see your amps spike even higher than your "stall current" (until the motor/fuse burns out or your driver shuts down due to overcurrent or overtemp conditions). Of course with those nifty encoders your 'bot should be able to detect that it's stuck..... smile.gif

    In any case, even a rough idea of stall and/or normal load current would be really useful.

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    When the going gets weird, the weird turn pro. -- HST

    1uffakind.com/robots/povBitMapBuilder.php
    1uffakind.com/robots/resistorLadder.php
  • DgswanerDgswaner Posts: 795
    edited 2008-05-20 21:41
    shows what I know, enough to be dangerous. well that will even be easier to test, I'll let you know what I come up with. I can tell you that I had issues with my propeller resetting due to the current spike, so I opted to add a 2nd smaller battery to power the propeller. I should be able to get that for you in a few hours.

    thanks for the info, I always try to be open to learn,

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    "A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

    DGSwaner
  • WhitWhit Posts: 4,190
    edited 2008-05-21 00:20
    Hey Dgswaner,

    Glad you got yours! Sorry about the "torcher." Guess you can get your measurement now too. I've been so busy that I haven't even gotten any of my other parts. Battery and charger are still first on the list.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • DgswanerDgswaner Posts: 795
    edited 2008-05-21 03:53
    thanks whit, the "torcher" lol is over. it won't quite as easy to add these as i thought but it's only going to take slight modification. I added 8" wheel so i could use some casters I had on hand. it was really easy I didn't even have to touch the motor kit to do it.

    Zoot: no load starting peak was 5 amps
    with load the peak was 8 amps
    if I tried to stop the wheel I could get it up to 10 amps or even higher, but I didn't want to try too hard. hope that helps, oh and that was only one motor.

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    "A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

    DGSwaner
  • Ken GraceyKen Gracey Posts: 7,365
    edited 2008-05-21 04:41
    DGSwaner,

    I take it the modification you have to do to the garbage can is cut out a few slots on the bottom in order to fit the motor in? If you mount these wheels directly under the garbage can you're probably facing a cutout to allow the motor to fit into the bottom of the can. Is that what's going on?

    I'm interested in how people use these, so show some pictures or explain the garbage can modification you've done.

    Ken Gracey
  • ZootZoot Posts: 2,227
    edited 2008-05-21 04:48
    DGswaner -- thanks. Given no-load continuous, something in the 6-10 amp range is about what I was guessing for load/stall.

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    When the going gets weird, the weird turn pro. -- HST

    1uffakind.com/robots/povBitMapBuilder.php
    1uffakind.com/robots/resistorLadder.php
  • DgswanerDgswaner Posts: 795
    edited 2008-05-21 05:53
    Ken, I purchased a Stainless steel garbage can from www.simplehuman.com/. (from a local store) it is approx. 18" in diameter and about 2.5-3' tall it was one of the kinds with a foot petal to open the lid. the stainless cylinder has a plastic top and bottom, so I dissembled it leaving only the cylinder. I then lathed 3- 18" HDPE disks. 1/4" thick. I used threaded rod to stack the disks vertically. and the stainless cylinder fits around the disks. more of the disks can be added if required, for more room to add components. I would post a picture but my son decided it would be fun to get in side the cylinder and roll around, which I'm sure it was, but it really messed it up and so I through it out. The attached image is done in sketchup and I made it before I went with a larger diameter and a 0 turning radius. but it should give you an Idea of what I mean.

    The motor mount has 2 sets of holes for mounting. If your mounting to a flat surface only one side will work, with out using any other hard ware, (not a big deal). Using that side (mounted on the top side) and using the included 6" wheels it would put my bot about 2" off the ground, leaving little room for casters. so I mounted them on the bottom side, this put my bot about 4-5" inches off the ground, I had to swap out my 2" casters for 4" casters.

    I have to say tho, my bot was built around a completely different method for a drive train, if I had started with these this wouldn't have been an issue. I'm quite happy with the kit. the quality is exceptional. the shaft sleeve is 1/2" which is the diameter of the lawn mower wheels found at Home Depot, all I did was add a slit in the wheel hub to accommodate the key, and a longer end bolt and I had 8" wheels. they don't look nearly as nice as the ones from the kit. but this will save me from my 3rd rebuild of this bot.

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    "A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

    DGSwaner

    Post Edited (Dgswaner) : 5/21/2008 2:17:41 PM GMT
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  • StampNut2StampNut2 Posts: 224
    edited 2008-05-23 07:08
    Any idea what the torque and load carrying capability of these units are?

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    Never give up when things go wrong, Just work them out.

    robosapienv2-4mem8.page.tl/
  • Kevin McCulloughKevin McCullough Posts: 62
    edited 2008-05-23 21:58
    We haven't "officially" determined the load carrying capacity of each unit yet. However, to give you some idea of what it is capable of, we were able to stand on our two-wheeled test platform while driving it around. I weigh about 175 lbs and I felt comfortable riding the robot. That means that each wheel was supporting about half that weight. The caster wheels on the robot are raised slightly off the ground and only provide stability (not support) on one side or another. A different co-worker weighing about 200 lbs also tried it out successfully.

    nono.gif DISCLAIMER: This does not mean that it was designed to carry or transport people. It also does NOT in any way state or imply the maximum load capacity of the wheel kits.

    However... as a personal project I would feel pretty comfortable using these to build a robot platform that could carry someone. I would probably use a 4-wheel design (two sets of wheels and motors) for increased stability, load capacity, and torque.

    Keep in mind that the load on each wheel is roughly the total weight of the robot (and payload) divided by the number of points of contact to the ground (each wheel). Additionally it may be slightly different than that depending on where the center of mass is positioned. For example: if I built a 4-wheeled robot that could hold a 200 lb person, the load on each wheel would be roughly 50 lbs each (200 lbs / 4 wheels).

    Hope this provides "some idea" of what they can hold. smilewinkgrin.gif
    -Kevin
  • Tom CTom C Posts: 461
    edited 2008-05-25 16:29
    Whit+,

    You might want to take a look at these wheels at the Jameco Robot Store for your back and front balancing wheels.

    http://www.robotstore.com/store/product.asp?pid=905&catid=1560

    They will require a mount and an axle, but they come in a varity of sizes and are not made of hard plastic/rubber.

    Regards,
    TCIII

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    If you are going to send·a Robot·to save the world, you·better make sure it likes it the way it is!
  • WhitWhit Posts: 4,190
    edited 2008-05-26 02:17
    Thanks TCIII,

    I'll check it out.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • WhitWhit Posts: 4,190
    edited 2008-06-04 14:54
    Earlier in this thread, we discussed running the Stamp, BOE and electronics with the same 12 volt battery that powers the drive motors. Chris said he had done this. How is this done in a way that eliminates noise issues and protects the Stamp from damage. I know it can be done, I'm just not sure what is involved.

    Thanks for any advice!

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-06-04 22:16
    Whit,

    I am using a 12V SLA battery…its terminals go to a terminal block and from there branch to both the Barrel jack on the BOE as well as the + & - terminals of the HB-25 Modules. In order for the BOE to be adversely affected by the motors, the power would have to sag below 6V long enough to affect the BASIC Stamp. This hasn’t happened yet.

    On another project which uses 4 DC Motors with Planetary Gear Reductions, I have 1 HB-25 controlling two motors. This is duplicated on each side for a skid steering system. That robot is a bit smaller and uses two 7.2V R/C Battery Packs (3000mAh/ea). On that robot one battery runs the motors and the other runs the electronics. The R/C batteries have less current capability than the SLA, which is the reason for the difference.

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    Chris Savage
    Parallax Tech Support
  • WhitWhit Posts: 4,190
    edited 2008-06-05 02:01
    Thanks Chris!

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • StampNut2StampNut2 Posts: 224
    edited 2008-06-05 06:41
    In my experience it is best to have the 12v system separate from your stamp 5v system but can have the grounds tied. Does anyone know if these motors have any internal capacitors across the motor contacts? If not I will be putting some externally to reduce any interference.

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    Never give up when things go wrong, Just work them out.

    robosapienv2-4mem8.page.tl/
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-06-05 14:17
    The need for a separate supply is really application dependant. There’s nothing about the current configuration of my larger robot that requires me to have a separate supply. More batteries equals more weight, so I really have to have a good reason to add that extra weight before I will do it. I had someone recently mention to me that a 9V battery plugged into the BOE would prevent any issues on my robot from the motors running off the same battery. I had to explain to them that a 9V battery…even a 6V AA pack, wasn’t going to run the BOE since it was connected to an LCD, GPS, Servos and other hardware. The GPS alone justified the use of the main pack. Remember, with a high-end motor controller like the HB-25, noise isn’t usually an issue in a shared supply. It is sagging from current spikes. A higher VIN VS. VDD will prevent this. 12V is double the VIN of the BOE and the Wheel Kits don’t consume enough current to pose any issue on a good battery.

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    Chris Savage
    Parallax Tech Support
  • Tom CTom C Posts: 461
    edited 2008-06-05 16:47
    Chris,

    When are you going to make some schematics and software available for your robot design using the Parallax Motor Mounts and Controller?

    Regards,
    TCIII

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    If you are going to send·a Robot·to save the world, you·better make sure it likes it the way it is!
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-06-05 19:54
    Tom,

    Some changes occurred in who was handling the robot resources while the Wheel Kits were being developed and I was not on that project. However I do have a new robot design that is very similar to the first and I will be working on it this summer after a few other projects are finished. This is the robot I originally posted about that will have GPS navigation using our GPS Module. I have a prototype on another platform but I need to make the changes necessary for the Wheel Kit. One of the other delays was that I need to create a custom PCB due to the number of sensors I am including. I switched from a BS2p to a BS2p40. Yeah there are so many projects and so little time. But they all get done eventually! =) Take care.

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    Chris Savage
    Parallax Tech Support
  • StampNut2StampNut2 Posts: 224
    edited 2008-06-06 09:20
    Chris, Thanks for your input on this motor unit, I must say I am impressed with it's design, can't wait to get into a decent project with it, Like you I have many projects on the go and trying to fit them all in is a nightmare. My next project before the motor unit is a J5 from Lynxmotion, modified of course. Then onto the motor unit, I have also been thinking of fitting a J5 torso on this base unit.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Never give up when things go wrong, Just work them out.

    robosapienv2-4mem8.page.tl/
  • Tom CTom C Posts: 461
    edited 2008-06-06 11:15
    Hi Chris,

    Thanks for the quick response and update.

    Much appreciated.

    Regards,

    TCIII

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    If you are going to send·a Robot·to save the world, you·better make sure it likes it the way it is!
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-06-06 14:10
    Tom,

    No problem…Thanks for the interest in the product. We certainly had fun designing, testing and building them. Now for me it is a project I have to place into my queue to get finished. This thread is quite long and at some point we talked about the Octagon shaped frame. I was thinking of doing that still. The only thing about it is that it would limit terrain some. The robot would not be able to navigate much past floors or paved road. We’ll see what happens. I will finish the other robot so that I have a proof of concept first. This shouldn’t be a problem since the other platform is already built and all the sensors are mounted. It’s just a matter of having a couple of those custom control boards made and writing some code. As soon as I am working on it again I will start a new thread for it.

    StampNut2,

    The original test platform mentioned above is on a 4WD1 from Lynxmotion. Before we built the wheel kits I needed a quick way to test a larger platform and that was the quickest and easiest to build.

    Whit,

    See above…This is the platform I was referring to when I mentioned the slightly smaller one with the dual R/C battery packs…Sneak peek? Oh alright…since you twisted my arm! =)

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    Chris Savage
    Parallax Tech Support


    Post Edited (Chris Savage (Parallax)) : 6/9/2008 5:34:16 PM GMT
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  • StampNut2StampNut2 Posts: 224
    edited 2008-06-07 11:23
    Chris: Nice shot, love it. Look forward to your posts on your motor mount.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Never give up when things go wrong, Just work them out.

    robosapienv2-4mem8.page.tl/
  • WhitWhit Posts: 4,190
    edited 2008-06-08 01:46
    Wow Chris - Looks great. Thanks for the update. I working on my design ideas now. Will post when I have something to show.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • Tom CTom C Posts: 461
    edited 2008-10-16 22:53
    Hi Chris,

    It has been four months since your last post concerning schematics and software for your robot design using the Parallax Motor Mounts and Controller.

    Have you made any progress?

    I purchased the caster wheel kit and find it to be of the same outstanding quality as the Motor Mounts and Controller kit!

    I have started pulling together everything that I will be to build my autonomous robot using the Motor Mounts/Controller and caster wheel kit.

    Regards,
    TCIII

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    If you are going to send·a Robot·to save the world, you·better make sure it likes it the way it is!
  • Tom CTom C Posts: 461
    edited 2008-10-16 22:55
    Hey Whit,

    Where are you?

    Have not seen any posts from you since early June and this thread has been dead until today.

    Have you made any progress with you design ideas?

    Regards,
    TCIII

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    If you are going to send·a Robot·to save the world, you·better make sure it likes it the way it is!
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