Does anybody know the pitch of the FP pinion gear? I want to gear a couple of them up for a vaccuum impeller. We hooked up 2 cims to a vaccuum fan and got the same rpms as the original AC motor. Don’t want to use up 2 CIMs so we want to make the rig run on 1 CIM and 2 FP’s.
Thanks
Bruce
This might be useful.
Eh,
The DP is 32 on the one AM sells, but the DP on the fp gear in the kop is metric: .8 module.
I would recommend buying the individual AM Planetary for Fp’s and integrating them into a gearbox since the one linked above’s ratio is off, 6.18:1 . You want a 3.667:1 to match the Cim’s free speed.
Extremely tired, so if i’m wrong, please suggest the correct approach.
-RC
0.8 (millimetre) module is exactly 31.75 diametral pitch (per inch). You won’t have too much trouble making a 32 P gear mesh with that pinion. Many teams have pulled it off without too much trouble.
(Dirty as it is, it’s not as impossible as it sounds. In fact, there are a few documented cases of a team managing to make a 0.7 module gear “fit” a 32 pitch pinion—teams 111 and 180, for example.)
Interestingly enough, the Fisher-Price (Johnson) 00968-9015 motor spins at a free speed of 15 700 rev/min, while the CIM FR801-001 spins at a free speed of 5 310 rev/min. The AM Planetary doesn’t quite match these based on that speed ratio. (It ought to work, but you might find that the load sharing isn’t quite what you’d have otherwise predicted.)
I am fairly certain that the fp motor gears are 32DP. Every other gear in the plastic gearbox is AGMA, not metric.
If the motors are the same as last year (and they probably are), their actual free speed (measured by us) is around 19000 RPM, instead of the published 15700 RPM. That would match nicely with the AM Planetary for a ~5200 RPM free speed, pretty close to the CIM’s free speed. AndyMark probably measured the free speed as well to design their gearbox.
I haven’t opened this year’s gearbox yet, but last year’s first stage was 0.8 metric.
Does anyone know what the pitch diameter of the first gear in the FP gearbox is? We’re trying to use that gear in something else, but need to know how far, center to center, to mount it from the motor’s shaft center (with the stock pinion).
You can figure this out for yourself by following the steps described in Mark Kramarczyk’s white paper.
The first step is to count the teeth on the gear you intend to use. Several others in this thread have observed that the first two gear meshes in the FP gearbox are 32 DP. So if the one you want to use has N teeth, its pitch diameter will be N/32 inch.
As far as I know, the first two stages of the Fisher Price gearboxes in the kit of parts use imperial DP gears. Currently, they use 32DP, but in the past they used 24DP. At least for last year’s gearboxes, you can take out the first two stages and install them in your own gearbox housing and run them an entire season without any problems.
Here’s a photo of a gearbox I designed last season to use the first two stages in an easier-to-mount enclosure to power intake rollers. The calculations were done using 32DP for gear pitch with +.003 added to all center-to-center distances for machining tolerance, and it worked just fine through countless hours of operation and five competitions.
'http://www.team228.org/gallery/105/slideshow/post-ship-date-practice_2a809-2a809.jpg](http://www.team228.org/media/pictures/view/5074)
http://www.team228.org/gallery/105/slideshow/post-ship-date-practice_6a61d-99c7f.jpg](http://www.team228.org/media/pictures/view/5073)
We took apart a 2010 gearbox, and discovered that the hole in the second gear is an octagon, not a hexagon. This affected our gearbox design…we decided to use two first stage gears in series insted of a first gear then a second gear, so we could use hex shaft for the output shaft.
Jim,
Unless I am misunderstanding, if you put the two gears in series then the first stage is functioning as an idler. Since an idler doesn’t affect the gear ratio, and the motor is reversible I find myself asking, why? I’m sure I am just creating the wrong mental picture, but what is the correct one? Got a photo?
The small motor pinion contacts the large outer part of the first gear. The center smaller gear on the first gear contacts the large outer part of the second gear.
It is not just an idler.
Take apart the plastic FP gearbox, see how it works! it’s fun…watch out for the grease
I think it just clicked…
…use two first stage gears …
You are using the first stage gears from both FP gearboxes to make a single gearbox. I kept reading, “…use the first two gear stages…”. Yeah, that makes sense now. Thanks for the clarification.
As Richard points out above, I have taken them apart; there good guts in them there trannies. One day I will remember to weigh the excess grease I take out. 
I opened up this year’s gearbox and the first stage really is 32 DP (72:19). Last year’s 79 teeth gear was 0.8 metric, though, and I’m as sure as my EE degree allows me to be on gear issues.
Nominal center distance, then, is 36.1156 mm.
I have seen gear prints from FP, they are definitely an English unit company, at least when it comes to gear pitch. I would be shocked if they switched back and forth between metric and English.
In any case, I am confident that this year’s first stage is 32 DP 20 Degree Pressure angle (which is close to a metric module of 0.8 but not quite 32DP =0.79375 module). It may run with a .8 module gear, but it will never be happy about it 
Joe J.