Pololu 3/4" Plastic Ball Castor for GoPiGo3

GoPiGo
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One of the “mods” I like for my GoPiGo3 robots is to replace the metal ball castor with a Pololu plastic ball castor. It turned out much easier than I imagined it would be.

Carl uses a Pololu 1" Plastic Ball Castor, and ROSbot has a Pololu 3/4" Plastic Ball Castor.

The secret to mounting the ball on both robots has come from scrounging through our plastics recycle bin to find a plastic jar lid or container for a thin, but stiff, flat area the size of the top of the existing metal ball castor assembly.

Castor_Mount
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To make the mounting:

  • I traced around the metal castor onto the plastic,

  • Marked off the unneeded area on both sides of the new plastic castor,

  • Drilled the two GoPiGo3 mounting holes

  • Drilled the two castor mounting holes

  • Cut the shape out using an electric hacksaw

  • Smoothed the edges and corners with a coarse file,

  • mounted the castor to the plate
    and put the two spacers that came with the castor on the opposite side of the mounting plate

  • assembled the castor with the plastic roller bearings

  • mounted the assembly to the GoPiGo3 using the original screws and washers
     

Pololu_Castor
Pololu_Castor4032×3024 821 KB

The plastic ball is quieter, lighter, and leaves no marks on the floor.

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I had wondered how you mounted that - that’s a great idea. I’ll have to look into doing that.
/K

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Yippee!

I found a supplier here in Moscow that has them in stock for only 200-or-so rubles! (About $3.)

I’m going to order a couple or two.

Where did you get the plastic sheet?

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Carl’s comes from a take-out chicken-parm dinner, and Dave’s from the lid of a Rubbermaid food storage thing that got separated from its mate.

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I decided to give the Pololu caster a try. I had ordered one a while back, but just hadn’t gotten around to mounting it.

The style has changed a little. I have access to a CNC machine, so I designed the mounting plate in Fusion 360 and cut it out of some aluminum I had. Turned out pretty well:

PXL_20210705_225920884_sm
PXL_20210705_225920884_sm800×603 68.2 KB

In the process I discovered that Finmark had a slight tilt upward at the front. The new assembly is a bit taller than the metal caster, so the old standoffs wouldn’t work. I really lucked out that some standoffs I were just the right length (when stacked), and even cured the slight tilt.

I was going to test it out this evening to see how much quieter it is, but now Finmark won’t consistently join the wifi network. This is the new Raspberry Pi ( as discussed previously). These intermittent hardware issues are getting really tiresome…

/K

PS - happy to share the design file to anyone who’d like it

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Wow! Only thing I know how to do with aluminum is rip off a piece of Reynolds Wrap. You really did a pro job on that mount.

I hear ya. I’ve been putting up with occasional 1 to 5 second remote shell freezing for years and gave up hope of solving it.

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Right. I used the 3/4 “ ball for Dave to level it and keep the stock standoffs.

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I had already bought the 1". It would have been smarter to look at my options. I got very lucky - I thought I was going to have to cut down the standoffs some how, or find new standoffs.
/K

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It’s worse with ROS, since the robot depends on the remote connection with my laptop for navigation. Would be nice to have the whole navigation stack running locally. But that would take more horsepower than the Raspberry Pi can provide.
/K

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