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September 4, 2008
Product ROB-10825 |
about 2 years ago
This is a decent value for a chassis, but the motors are junk. They are undergeared, no useful torque and no-load speed is too fast to be useful. Replace them with continuous rotation servos and you have a useful chassis. See build at http://find.botmag.com/091206 and http://find.botmag.com/111207
Decent value, but the 48:1 gearmotors are hopelessly underpowered. Replace them with 100:1 or more gearmotors or CR servos and then the “Magic” can start. See http://find.botmag.com/091206 for details on one PicAxe build.
Product ROB-10543 |
about 2 years ago
+1 on the recommendation to switch to Vex mecanum wheels. I bought both and there is no comparison. The Vex wheels are $60 and infinitely better than these awful Fingertech wheels.
I beg to differ. I’m using four Futaba continuous rotation servos with gobs of torque and excellent low-speed control. Square chassis layout, exactly 25% weight on each wheel. The two big problems are:
1) too much friction on the wheel’s roller shaft (bad design), which varies as the contact point on the roller changes. It’s worst at the roller tip, when the shaft is really cocked in that small “bushing” on the main wheel, and
2) wrong roller profile: the proper geometry should roll smoothly as the wheel rotates. The current design hops and stumbles as it rotates, like a hexagonal wheel. There’s nothing smooth about it and all that hopping makes & breaks contact with the ground even with pivoting axles at low speed. That introduces lots of chatter and random motion.
Did that, and removed flash, and made custom delrin washers to replace the stock steel ones, and polished the axles, and modified my chassis so the axles pivoted to ensure all 4 wheels touched the ground evenly. Still unacceptable performance. Would be OK if the price was $20 for all four wheels, but these are horribly overpriced at $75.
Quite disappointed; these are NOT high quality wheels, although sadly they are the only option available. They hop & bump & bumble & skip, even at low speeds, like rolling on hexagonal wheels. The only “bearing” is the steel shaft spinning in the central housing, so there is lots of friction when the roller tips touch the ground. Do not expect to match the smooth motions you see in Youtube videos of Airtrax forklifts. Your chassis needs to swivel axially to achieve any driveablity at all.
Product ROB-10332 |
about 3 years ago
It’s pretty lame that the servo they recommend and sell for this won’t bolt right up without grinding aluminum. Sparkfun should add that to the description, as well as the fact that the servo required is an extremely odd size and mounting configuration, so you are unlikely to find another servo that’s even close to fitting.
No public wish lists :(