FP Gearbox Ratio
 

Does anybody know what the ratio for the FisherPrice gearbox is, alternatively, does anyone have a good idea of how to measure it?

Re: FP Gearbox Ratio
 

I'm not sure what it is, but I do know the (hard) way to measure.

Take it apart. Be careful; you'll have 3-4 screws and 3 or so mounting tabs to undo. Screws first, then use a small screwdriver to help with the tabs.

CAUTION: The FP gearbox is full of thick grease. I was on a team that raided some to lube up their Toughboxes once and still didn't have a problem with keeping the FP gearbox lubed!

Next: count the teeth for each gear. This will give you 3 ratios, IIRC. Get each as an X:1, then multiply the Xs to get a final Y:1 ratio. If you like whole numbers, go ahead and get it into that.

Then put the gearbox back together and make sure it still turns right.

Re: FP Gearbox Ratio
 

1. Take it apart.

2. Wipe off grease from parts.

3. Count gear teeth.

4. Multiply and divide as necessary to find ratio.

Notice that some of the gears have 3/8" hex holes in them, us lucky Yanks can buy hex shaped aluminum shaft that size to make shafts to use those gears in our own housings (for using one or two stages of the FP gears). You folks in metric areas might have trouble finding parts like that.

edit: Eric and I think alike

Re: FP Gearbox Ratio
 

You can find pictures to go with the above descriptions in the whitepaper at http://www.chiefdelphi.com/media/papers/2284

Re: FP Gearbox Ratio
 

Assuming the gear box is the same from 2007, it is a 124:1 reduction.
http://www2.usfirst.org/2007comp/oth...tices_RevC.pdf (page 8)

Re: FP Gearbox Ratio
 

Just a word of warning if your planning to use the FP gearboxes with the FP motors:

Some teams have found that the motor that came in the kit of parts has a 15 tooth pinion on it. The gearboxes need a 19 tooth to work properly, so if your motor has 15 tooth, it won't work with the gearboxes.

Re: FP Gearbox Ratio
 

Did anyone receive an FP with the proper 19 tooth pinion on it? Or has someone found a source of an appropriate 19 tooth pinion?

Re: FP Gearbox Ratio
 

If you have access to a CNC. You can rip the gears out of the gearbox and make new plates. It works out better since you can have your own mounting holes.

http://www.chiefdelphi.com/media/photos/34184

If anyone wants me to, I can CAD up a gearbox that uses the 15T pinion?

-RC

Re: FP Gearbox Ratio
 

The reason I ask is that we have motors from a previous year (of the appropriate model number) with the 19 tooth pinion. If some teams received the motor with the 19 tooth pinion or if a COTS 19 tooth pinion is available it should be legal to use these motors.

We finally have some machining capabilities with our new shop this year (including a CNC I believe), but we are trying to avoid making anything complex until we have a chance to gain more familiarity with the machines in the offseason.

Re: FP Gearbox Ratio
 

Kevin--we made a single stage gearbox last year using the FP motor and first stage gear, and a piece of 3/8" hex shaft for the output, and some 3/8" flanged bearings. We made the the holes to mount the motor and bearings without the aid of any type of CNC or DRO device, in fact it's pretty sloppy but lasted all season.

If you need less reduction than the stock FP box gives, don't be afraid to try to make a simple gearbox using one or two stages of FP gears.

Re: FP Gearbox Ratio
 

Is there an easy way to pull the pinion off an old FP and re-fit it onto the new ones?

Re: FP Gearbox Ratio
 

Still needs to be COTS.....and no, there is not an easy way to get them off. It's possible to get the gears off, but it seems to require building your own strong gear puller.

Re: FP Gearbox Ratio
 

The idea would be to switch the whole motor with pinion attached. The 2008 and 2009 motors are the same as the ones this year with the exception of the pinion.

As Mr. Forbes posted, it is possible to get the pinion off. Teams have done this to use the FP with Banebots and AM Planetary gearboxes. Once you do get it off though I'm not sure if you could put it back onto a different motor.

EDIT: As the FP with 19 tooth pinion appears to still be available from AM I think it's time for me to head over to the Q&A and see what the GDC thinks about this mess.

Re: FP Gearbox Ratio
 

You can get the gear off with a pin punch in an arbor press, with a custom milled plate with a slot to hold it. Or, if you don't care about destroying the gear, you can crack it with a nut buster.

Re: FP Gearbox Ratio
 

The gearbox in the white paper I linked was done on a drill press as well. A drill press that is in good shape and some patience is all that is needed. Just start with a small bit (small enough to fit in the punch indentation) and open it up very slowly. I also did the mod to skip the first stage of the gearbox like shown on the HOT (FRC67) bot using just a hand drill and a dremel.