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Messages - ChrisGBG

1
Project logs / Re: Omnidirectional Remote Controlled Robot
I just did a very quick and rough assembly... and well... it works kinda, the wheels without any plastidip or similar on a wooden floor slip and slide a ton and my tiny DC motors with not much down-gearing in the gearbox spin way too fast, the robot moves in the expected direction reasonably well, but it's basically spinning at least 4 times the distance is moves if that makes sense, and since it has 4 wheels with no suspension or give what so ever going over anything makes at least one wheel free-wheel in the air.

And this is without the 300g battery, motor controller boards, arduino mega and second level on top, I expect the performance to get even worse with that weight on top.

I'm re-spinning the design, going down to 3 wheels and switching to a "medium" sized servo with lower gearing for power on the inside of the wheel, and a bearing block on the outside for more support, the design is pretty much a triangle with a flattened corner and a wheel fairly close to each corner, wheels going through the triangle in holes just big enough, axles on the underside the 6mm plexi base, this way I can use a servo horn like you have for rotation, and an axle going through the wheel and into a bearing block on the outside for more support, axle doesn't have to marry at all to the servo, it's just there to support the wheel and hold it sideways.

I'll need to find something like plasti-dip to coat the rollers with as well, clearly needs more traction.

Quick sketch http://cl.ly/image/1x3y0A2u1X19
2
Project logs / Re: Omnidirectional Remote Controlled Robot
Ah, at that scale I guess bolting a servo straight to a wheel works really well, my robot is a fair bit bigger and heavier and has motors + gearboxes with a very awkward and weak axle, hence why I'm trying to figure out a strong way to mount the wheels to a supported axle which in turn mounts to the gearbox axle, though frankly I'm starting to wonder if ditching the motors and gearboxes and going for something that has self contained support isn't a better idea.

Here is my current design:

http://cl.ly/image/3B2x2F1U410a

http://cl.ly/image/320L2e0N162G

http://cl.ly/image/0w3M2P432Y2V

tried img tags but they didn't resize properly only showing a tiny part, it has some pretty large pit-falls, like the axle adapters http://www.dfrobot.com/index.php?route= ... uct_id=645 that connects to the gearbox http://http://www.dfrobot.com/index.php ... uct_id=100 (same design except straight instead of bent) only way I could figure out to marry the M8 bolt "axle" of the wheels is gluing a nut to the end of the adapter, which ofc means I'm relying on glue to hold a rotating axle, and a nut on a rotating bolt... I'll have to locktite it. I'm not confident at all.

Advice would be greatly appreciated except "get a 3d printer" :P they don't grow on trees you know.
3
Project logs / Re: Omnidirectional Remote Controlled Robot
Very neat, I got the exact same wheels and I'm wondering what you used to fixate them on the axle? I just see something white and screws? Did you try the wheels without the plastidip? Did it slip a lot?

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