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S2 Tires — Parallax Forums

S2 Tires

MSDTechMSDTech Posts: 342
edited 2014-12-03 04:58 in Robotics
I am having problems drawing with the S2. It appears that I have extreme slippage of the O-ring tires in the wheel. I can easily rotate the tire with the wheel held still. Is there any way to lock the O-ring in place to keep it from moving. The robot is still new, so I don't think its a wear problem.

Comments

  • WhitWhit Posts: 4,191
    edited 2014-11-24 06:37
    @MSDTech - welcome to the Forums and especially to the S2!

    Contact Parallax and I know that they will get this fixed - if you don't want to wait - take your "tire" to Home Depot or Lowes or a good hardware store and look in the O rings for some slightly smaller tires - they should be very inexpensive - there are other colors available too and I've often thought of getting some for fun!
  • MSDTechMSDTech Posts: 342
    edited 2014-11-24 07:23
    Actually, I just tacked each O-ring in place with a little adhesive (a plastic/rubber compatible one). Seems to work fine and will be easy to remove when it's time to change the tire. My local stores didn't have an O-ring that fits, much less an assortment of colors. One of the problems of living in a small town.
  • NWCCTVNWCCTV Posts: 3,629
    edited 2014-11-24 13:41
    MSDTech wrote: »
    One of the problems of living in a small town.
    That is why man created eBay, FedEx, UPS and USPS!!!!
  • WhitWhit Posts: 4,191
    edited 2014-11-24 19:12
    NWCCTV wrote: »
    That is why man created eBay, FedEx, UPS and USPS!!!!

    Andy - clearly erco has drawn you to the dark side... ;-)
  • NWCCTVNWCCTV Posts: 3,629
    edited 2014-11-24 20:37
    Nah, I was that way long before!!!!!
  • msrobotsmsrobots Posts: 3,709
    edited 2014-11-24 20:37
    Living in rural areas has positive and negative sides. Since some mistake in Google Maps display of streets around my place the chance I will be found by UPS and FedEx is quite minimal.

    Usually it takes three attempts for delivery until the drivers find the pace. Once they know it, no problem. Then they get replaced by some other guy and the trouble starts again.

    Did you know that FedEx and UPS are planning a merger? The new company will be called FedUP...

    Enjoy!

    Mike
  • MSDTechMSDTech Posts: 342
    edited 2014-11-25 08:33
    NWCCTV wrote: »
    That is why man created eBay, FedEx, UPS and USPS!!!!
    Of course, this means a 3 to 5 day delay and a significant increase in cost for each small part while debugging a system.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2014-11-25 09:14
    MSDTech,

    I'm glad you were able to fix the problem. However, this is something you might want to alert Parallax about anyway. Those tires definitely should not slip on the wheels. If the manufacturer is installing O-rings that are a bit too large, it's something that Parallax needs to know about so others don't experience the same issue.

    -Phil
  • MSDTechMSDTech Posts: 342
    edited 2014-11-26 08:34
    I also have noted the wheels seem to have a considerable amount of "free play". They will rock about 1/8" pushing laterally on the bottom.
    I've e-mailed support@parallax.com with these concerns.
  • MSDTechMSDTech Posts: 342
    edited 2014-11-26 08:47
    What started this debugging was the S2 not being able to reliably repeat a movement. As a test, I wrote a program to run a square 4 times using the move commands in the default S2 object-
    S2.set_speed(7) ' Set drawing speed to 50%
    S2.here_is(0,0) ' Set current S2 coordinate location
    S2.begin_path
    Repeat 4
    S2.Move_to(0,200)
    S2.Move_to(200,200)
    S2.Move_to(200,0)
    S2.Move_to(0,0)
    S2.end_path
    The result is shown in the attached jpg.
    Square.jpg
    866 x 829 - 117K
  • ercoerco Posts: 20,256
    edited 2014-11-26 09:22
    Your jpeg actually shows very consistent operation. Play/backlash is not causing that accumulated error, the problem is that the 90 degree turns are slightly off calibration. IIRC, there is a little-publicized calibration routine which might help here. PhiPi?
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2014-11-26 10:35
    Here's a post that should help with that:

    -Phil
  • MSDTechMSDTech Posts: 342
    edited 2014-11-27 07:16
    Phil, I looked at the two parameters
    DEFAULT_FULL_CIRCLE = 955
    DEFAULT_WHEEL_SPACE = 153
    What are the units on these measurements. The wheel space may be a problem, as the wheels I've got are not solid on the shafts and have about a 1/8" of free play.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2014-11-27 08:11
    Don't worry so much about the units. Just tweak the numbers a little until you get the behavior you want. BTW, your S2's wheel play is no different from that of any other.

    -Phil
  • ercoerco Posts: 20,256
    edited 2014-11-27 11:06
    If you're as anal retentive as I am about minimum backlash in the drivetrain, you can disassemble your S2 (likely voiding the warranty) and carefully add some superglue or epoxy (less risky) inside the motor shaft hole in each wheel. It's a bit loose for my tastes. The D-shaped hole in each wheel that presses on to the gearmotors

    Surely I don't need to say "don't glue your wheel in place". :) Run the motors to verify the wheels are turning true as the epoxy sets up.
  • ajwardajward Posts: 1,130
    edited 2014-11-27 12:46
    msrobots wrote: »
    Living in rural areas has positive and negative sides. Since some mistake in Google Maps display of streets around my place the chance I will be found by UPS and FedEx is quite minimal.

    Usually it takes three attempts for delivery until the drivers find the pace. Once they know it, no problem. Then they get replaced by some other guy and the trouble starts again.

    Did you know that FedEx and UPS are planning a merger? The new company will be called FedUP...

    Enjoy!

    Mike

    Hah! I live in a fairly large town and they can find my building without problem. It's finding my apartment inside the building that seems to stymie them! ;-)

    @
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2014-11-27 18:56
    ajward wrote:
    Hah! I live in a fairly large town and they can find my building without problem.
    I live in a small town. My last UPS shipment was left at the house across the street. 'Substitute driver, but still -- the house numbers are clearly marked.

    -Phil
  • ercoerco Posts: 20,256
    edited 2014-11-28 20:26
    Getting back to the original subject about aftermarket tires, I think the S2 would look pretty sweet with some 20 inch low profile tires and rims. Who's gonna chop, channel and tub an S2 first?
  • ajwardajward Posts: 1,130
    edited 2014-12-03 04:58
    erco wrote: »
    Getting back to the original subject about aftermarket tires, I think the S2 would look pretty sweet with some 20 inch low profile tires and rims. Who's gonna chop, channel and tub an S2 first?

    The 20's would, at least, give the critter some ground clearance! ;-)

    @
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