Fisher Price Gearbox Q...

[Anton Abaya]

I have gotten word that the gearboxes have stripped gears in the past.

Any other teams wanna confirm this? Have they ever failed you guys?

-anton

[Dan 550]

The plastic gears in the FP motors are extremely low quality. Any robot over 105 lbs has a magnificent chance of stripping or melting the gears if under heavy load, such as in a pushing situation. They are just overall bad for robots. The motors themselves are decent enough, but the gearboxes are horrible. Take this from a guy that saw both of his melt and almost catch the rug on fire last year.

[Ian Mackenzie]

Our team found that the problem with the Fisher-Price gearbox is not so much that the gears are bad, but that one of them is seated poorly. If you open up the gearbox, the shaft for one of the gears is sitting (on one end) in a miniscule little ring of plastic. The shaft had broken part of the plastic ring and slipped out, causing the gear to mesh improperly and strip teeth. Once we drilled right through the gearbox to secure the shaft more solidly, the gearbox worked much better.

Ian Mackenzie
Team 188

[Patrik]

Our teams philosophy is that they are good for grease and nothing else. The gear boxes do suck, I think we used them in one of the years before I came to the team and found them to be bad.

I admit we have a plan for the motors this year. It's a bit secret (for now) but let's just say be prepared for the MINI-ME!

[Nathan Kroll]

I know that Beatty and Hamond has had the fisher price gearboxes on their robot for a few years now (I am pretty sure that they are unmodified internally). They havent seemed to have any problems with it (actually there drive trains has proven to be one of the most simple and reliable I have seen). Mabye you could try and contact them. However my previous team modified the gear boxes and had some trouble with the plastic gears chipping. Nothing that couldn't be prevented with some moderatly careful driving, no jerky forward to reverse movements.

[Joe Johnson]

You may want to check with Bill or Brian or Daryl before you start using the FPs for a drive system without modifications.

My understanding is that they make a special aluminum gear that replaces the plastic gear on that last stage of the output.

Bill showed me it once.

In fact, I have used the very system they showed me.

As it turns out, W.M. Berg (wmberg.com) sells a gear that can be used to replace that last gear in the FP gearbox. It requires some machining in order to get it the torque out of the gearbox somehow (machining off the plastic gear, bolting in the aluminum gear, etc.), but the gear profile and thinkness are perfect.

FYI.

Joe J.

[Ed Sparks]

We've boken teeth off of the final gear in the past. When this happens, you get a flat spot on the gear and that broken tooth usually finds it way back into the gear mesh causing even more problems. If we use the transmissions, I'm going with an aluminum final gear.

[Bill Beatty]

Joe is correct. We have used the FP gearbox for the last 3 years. The last gear was breaking teeth, and, amazingly, it was on the gear and not the pinion. We gave up trying to figure out why it was failing and made an aluminum ring gear and bolted it onto a turned down FP gear. By taking out the gobs of grease that comes it the FP case, there is no increase in weight. Since making the mod, we have not had a failure. We make an aluminum hub that fits the FP output and connects to the wheel spokes. This setup seems to be a reasonably efficient and easy to do drive. If there is any interest out there, we will post the detail drawing of the gear which can be made from a stock gear on a lathe.

Don't know if it will do the job this year though............

Bill Beatty

[jrukes]

Bill,

Please post the detail of the ring gear. You just never know if you'll need it.

Thanks,
Jason

[Anton Abaya]

Anyone wanna post the exact part number/name of this gear u can buy at wmberg.com?

I'll definitely get some. We're using the Fishers on our drive train and that goal is scaring me.

-anton

[Bill Beatty]

Here is link to the gear drawing.

Btw. We cut these gears from stock from Small Parts last year because purchasing finished gears was not allowed.

[Bill Beatty]

Try again - bad URL

[Joe Johnson]

Bill,

Nice print. Thanks for sharing it.

While you are on the site, why don't you share your thoughts about the game with us.

I have gone on record as saying that the game is the best they have come up with so far. I think it will be very exciting.

FIRST has done a very difficult thing: They have made a game that I think should be a good game for rookies AND will be difficult for us veterans to rig too much in our favor, AND is still challenging and exciting enough that we will try our hardest to build a killer machine anyway. A nice trick if you think about it.

Your thoughts Bill?

[Bill Beatty]

Joe

In keeping with the FIRST doctrine and portray a "kinder, gentler Mr. Bill," I will have to choose my words very carefully. I will get back to you shortly.

[Joe Johnson]

Bill,

You don't have to make with the nice nice for OUR benefit. We know you AND we love you.

Well, even though you haven't told us your thoughts, you have given us some clues. I suppose that you are not such a big fan of the game or you wouldn't have to plan your walk through the mind field of your thoughts so gingerly.

Ah well, I can wait. I look forward to your reply just the same... ...when you're ready...

Joe J.