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
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.
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
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!
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.
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.
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.
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
Bill,
Please post the detail of the ring gear. You just never know if you’ll need it.
Thanks,
Jason
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
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,
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?
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.
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.
Joe
I am so far into left field that my ideal robot tournament would be a single robot, doing a complex task against the clock. I loved the “Beat The Clock” matches at Rumble in 1999. I know I am totally alone out here, and I agree that it would be very boring for most spectators.
Traveling back from left field outer space, I thought that last year’s game was the best FIRST game ever, and I congratulated FIRST within a few days after kickoff, before we even knew how we were going to go at it. I feel that last year’s game contained so very many facets (some quite subtle and way too long of subject for this posting)
Joe, in our discussions over the past seven years (has it really been that long)? We agree on many points, but I don’t totally agree with your points involving making the FIRST game attractive for the general viewing public and hence on prime time TV. I don’t think the game itself or simple scoring really matters that much. If FIRST wants to compete with the popularity of the “Battlebots”, Woodie should grow a beard, give him a blonde helper dressed in shiny leather paints and a tight T shirt and coach the crowd to jump up and clap their hands over their heads whenever the camera pans by. Adding some flames here and there would also be helpful. This large dose of hype and also the combat and violence is what I believe is what is attracting most viewers to these programs.
As for this years game, obviously, the further it moves from my left field, warm fuzzy harbor, the less attractive I find the game. I think the qualifying rounds will be exciting as well as frustrating and somewhat unpredictable, but I fear that the elimination’s will be a tangled mess of pushing, shoving, hooking, and bordering on “Battlebots.” I hope I am wrong, but we shall see. Whatever the game, be assured we will give it our best shot.
Looking forward to seeing all you folks again in the approaching weeks.
Regards.
I opened up the Fisher Price units we got this year, and guess what- they’ve changed! Our units run at about 180 rpm no load (as compared to the published values of 100 from past years and in First Update #3). The bare motor now turns at 20,000 rpm (vs 15,000 previously), and has a 21T gear on it as opposed to the 16 tooth- the net effect of the higher speed and the larger drive pinion is the higher output speed.
The last 2 stages of gearing have been changed as well- the final stage gear has larger teeth and is black (and I assume is made of a different plastic). But all the ratios (save the first- from motor to the first stage plastic gear) appear to be the same.
Anybody tested these to see what the stall torque and currents have changed to?
Is it only me who has noticed the final stage of the Chipua drive ‘copper’ gear will fit perfectly into the FP gear box? I am not suggesting anyone do this, But using the design of the FP - perhaps using the plastic gears as templates or casts for aluminum? (Nothing in the rules about manufacturing your own gears.)
All that said we probably, will make our Chipua transmissions real simple, out of a worm gear reduction.
Also on the final stage teeth stripping on FP - this will happen in head to head pushing and shoving matches. Also the motors can get HOT in this situation - I suggest if you plan to use the FP as drive motors to take the plastic housing off, and direct some air on to them. Also don’t drive the wheel directly off the plastic axle - use some sort of belt or chain drive to the final stage to avoid sharp sudden shocks to the gearbox.