Re: Fisher Price Gearbox
 

Good posts, thank you all for the ideas.

Re: Fisher Price Gearbox
 

If you're in the business of manually making an octagon without precision tools, here's what I'd recommend: Draw it in CAD, mark the center in CAD, print it out 1:1, cut it out, use 3M spray adhesive on your material, stick your drawing to it, get a cuttin!

Re: Fisher Price Gearbox
 

Quick question: I've found 2 sources of data for the gear ratio of this gearbox. One says it's 124:1, the other says it's 188:1.

Can anyone confirm?

Re: Fisher Price Gearbox
 

For the teams that have driven arms with the FP through the gearbox, have you run into any issues with heat? Specifically when you are holding the arm at a set position (up in the air). I know the FPs are cooled by fan blades that spin when the motor spins, so it seems to me that heat may be a problem when the motor is exerting torque but not spinning.

Re: Fisher Price Gearbox
 

http://store.mendingshed.com/wheeldriver1.html

I'm not totally sure that this is the exact coupler used by these motors, but my team ordered two of them (they're only $4 a piece) to see if we can make the FP gearbox outputs a little more useful.

Cheers!

Re: Fisher Price Gearbox
 

We have used the plastic couplers several years and they work well. An easy way to connect the coupler to a keyed shaft is to buy a 4" V belt pulley and cut half of the pulley off leaving a 4" round flange with a nice keyed shaft coupler. Drill 4 matching holes in the pulley flange and the plastic coupling, add screws, drill out the plastic coupling to 1/2", put it all on a 1/2" keyed shaft and you have a connection that will not fail.
We will be doing this next week for this year's robot.

Re: Fisher Price Gearbox
 

Yes, heat can be a problem if you use FP motors to hold an arm in position. If your motors are operating close to stall when doing so, you can fry the motor in about 30 seconds. I had some problems with this last year. You can solve this in a couple of ways: use more gearing, or use 2 FP motors and gearboxes. Either one of these methods will reduce the workload of your motor, and make it less likely to heat up. You can also use a worm gear so your joint won't backdrive, though this requires building a custom gearbox, and not using the FP gearbox in the kit.

Re: Fisher Price Gearbox
 

We've got the same dilema, can anyone answer? :confused:

BTW, can we check those sources?

Re: Fisher Price Gearbox
 

Source 1: JVN's Spreadsheet calculations -- some of the spec #'s are from previous years and do not apply to 2008, so that's the only reason I question it
Source 2: FIRSTWiki