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This is a first for team 1726; never before have we fabricated a custom gearbox. This one was made by several students today using some 1/8" aluminum (holes punched with a Rotex Punch) and 3/4" birch plywood as a standoff.
The FP motor has a stock pinion, and the other gear is the first stage reduction out of the plastic gearbox. Since this gear comes with a hex bore, we just had to turn down a hex shaft in the lathe to make it work. Total reduction is 4.5:1, so whatever it's turning will be going pretty fast. 
(By the way, if Andy Baker is reading this... when are you going to come out with some sort of fisher price spur gear box? A kit that came with just the sideplates, standoffs, bearings, and output shaft would be incredibly useful! If made right, it could interface with a stackerbox, too.... and it would save us all this pesky manual labor 
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Discussion
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20-01-2009 19:28
JesseK
Re: pic: Fisher Price gearbox
But the manual labor is half the fun!
Looks good for the first time! Let us know how this works out for you.
20-01-2009 23:06
GUI
Re: pic: Fisher Price gearbox
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Originally Posted by JesseK
But the manual labor is half the fun!
Looks good for the first time! Let us know how this works out for you. |
We got this bolted on and made the part it drives today (video coming soon, watch for a thread in Robot Showcase), and it seems to work great. The trickiest part about this was getting the spacing between the motor and bearing holes right, and armed with a trusty 64ths inch ruler, we got it close enough that the gears mesh fine. At full speed it didn't seem to have any problems.
20-01-2009 23:51
MrForbes
Re: pic: Fisher Price gearbox
video of it in action, turning a roller, which does not do anything yet
http://www.youtube.com/watch?v=qNH4hb7crFU
20-01-2012 00:52
nixiebunny
Re: pic: Fisher Price gearbox
The 2012 FP gearbox is worse in terms of usability. I took one of ours apart, and it has orange gears with small octagonal holes instead of 3/8" hex holes.
I'm thinking about boring out the gear on the lathe to fit a 1/4" or 5/16" round shaft and using a metal hub to clamp the gear to the shaft. A bit of extra work, but life's like that.
20-01-2012 00:54
nixiebunny
Re: pic: Fisher Price gearbox
We need Kevin to weigh in, then we'll have five Forbeses on one thread. A new record!
20-01-2012 03:44
s_forbes
Re: pic: Fisher Price gearbox
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Originally Posted by nixiebunny
The 2012 FP gearbox is worse in terms of usability. I took one of ours apart, and it has orange gears with small octagonal holes instead of 3/8" hex holes.
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If you have access to a mill, you could probably machine an octagonal shaft if needed. It sure is easier to use off-the-shelf hex stock though.
20-01-2012 03:48
Akash Rastogi
Re: pic: Fisher Price gearbox
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Originally Posted by nixiebunny
... five Forbeses on one thread. A new record!
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20-01-2012 09:42
MrForbes
Re: pic: Fisher Price gearbox
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Originally Posted by nixiebunny
We need Kevin to weigh in, then we'll have five Forbeses on one thread. A new record!
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Anyways...interesting, we need to take apart the new FP transmission, and see what it's like, and also see how many old ones we have. I know we have two of the old white first stage gears, but we may need one more if we do what we were discussing last night for transmission for this year's robot.
We were planning on using a single stage FP motor/gear to drive the shooter, and a two stage to drive the collecting roller/conveyer.
20-01-2012 12:24
TheOtherGuy
Re: pic: Fisher Price gearbox
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Originally Posted by nixiebunny
We need Kevin to weigh in, then we'll have five Forbeses on one thread. A new record!
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How many old FP gearboxes does 1726 have laying around? Perhaps we could borrow a gear...
20-01-2012 12:34
billbo911
Re: pic: Fisher Price gearbox
I love the simplicity of this design, and may copy, er em... use this idea if we find a need for it. I love re-using the parts already supplied to us.
My only concern is that shock loads might cause a bit more damage to the plastic gear in this configuration. When the full gear set is used, there will be less impact on this pinion/gear interface caused by shock loads, like the ball going through the shooter.
I know it's early, but have you seen any problems yet, or anticipate any?
20-01-2012 12:50
Chris is me
Re: pic: Fisher Price gearbox
In true 2791 fashion, we were considering copying the wisdom of the Forbes family. But we'll probably stick to the aluminium gear we got off of SDP-SI instead of the plastic FP gears, because we don't have any good FP transmissions lying around. Cons of being a younger team, oh well.
20-01-2012 13:30
WileyB-J
Re: pic: Fisher Price gearbox
Our team did a similar design, taking a FP blue gear; then putting it in a toughbox chassis. We bolted two 9013 motors to it and attached it to our prototype shooter. It sounded like a bloody circular saw and ran nearly as fast as one, here's the results:
http://www.flickr.com/photos/wileyb-...eam?likes_hd=1
As you can see, not quite the results of bolting a CIM to the shooter:
http://www.flickr.com/photos/wileyb-...n/photostream/
Oh well, time to make our own ratios/gearbox!
P.S one of the students destroyed it by running the motors reverse when it was at full speed! Snapped a 9013 shaft and ruined the plastic gear, oops!
20-01-2012 16:05
nixiebunny
Re: pic: Fisher Price gearbox
You don't need to use FP gearbox gears, apparently. I googled the fisher price pinion gear pitch and found a CD thread that says that the FP gear is 0.8mm module, which translates to 31.75 diametral pitch.
McMaster Carr sells 32 pitch nylon gears in useful sizes for cheap!
http://www.mcmaster.com/#plastic-gears/=fw31pg
We'll try this out.
20-01-2012 17:44
MrForbes
Re: pic: Fisher Price gearbox
neat! but they don't have the magical hex bore in them...
btw I found the gearbox from the original picture, it's in good shape still and we can swipe the gear and bearings and possibly the motor from it.
The wood spacer is really nifty....
20-01-2012 18:43
nixiebunny
Re: pic: Fisher Price gearbox
Wood is good.
TheR/C car world has a lot of 32p and .8mod gears available too.
20-01-2012 21:14
MrForbes
Re: pic: Fisher Price gearbox
old white, new orange. Different tooth count, too
20-01-2012 22:33
Richard Wallace
Re: pic: Fisher Price gearbox
I count 72 teeth on the orange driven gear (and 25 on its inner driver). Can anyone confirm?
Looks like the octagon hole could be drilled out to 3/8" and then broached hex fairly easily. A three jaw should locate center well enough, if my 72 count is correct.
24-01-2012 23:20
MrForbes
Re: pic: Fisher Price gearbox
We have a several of the old white first stage gears, so we decided to make a new gearbox for the 2012 robot. It is integrated with the shooter, the lexan panel it is mounted to will be the side panel of the shooter. We do need to make a new shaft, since the one shown here was fabricated in a prior year. The lexan plate that holds the motor and the hidden bearing was made tonight by students, using a 7/8" Forstner drill bit, and a small drill press. We just measured the gear spacing using a vernier caliper, laid it out carefully and drilled it. The motor is not really at tight fit in the hole, but it's good enough. If you have a way to ream or bore the hole to the proper size, that would be better. Note that this is the 2011 motor with it's 19 tooth pinion gear, not the 2012 motor.
The shooter wheel will be mounted on AM hubs, keyed to a 1/2" shaft, which will be bored to fit over the new transmission output shaft. We will probably use a roll pin or two to hold the shafts together.
25-01-2012 13:40
Tom I
Re: pic: Fisher Price gearbox
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Originally Posted by squirrel
We have a several of the old white first stage gears, so we decided to make a new gearbox for the 2012 robot. It is integrated with the shooter, the lexan panel it is mounted to will be the side panel of the shooter. We do need to make a new shaft, since the one shown here was fabricated in a prior year. The lexan plate that holds the motor and the hidden bearing was made tonight by students, using a 7/8" Forstner drill bit, and a small drill press. We just measured the gear spacing using a vernier caliper, laid it out carefully and drilled it. The motor is not really at tight fit in the hole, but it's good enough. If you have a way to ream or bore the hole to the proper size, that would be better. Note that this is the 2011 motor with it's 19 tooth pinion gear, not the 2012 motor.
The shooter wheel will be mounted on AM hubs, keyed to a 1/2" shaft, which will be bored to fit over the new transmission output shaft. We will probably use a roll pin or two to hold the shafts together. |
Also, we had a 3/8" axle but found that if we tried to bore out a 1/2" shaft to fit around it to direct-drive it, we'd have a 1/16" wall around the circumference, which is relatively weak. Instead we bored out a 5/8" shaft and drilled out the center of our AM hubs to attach it to the throwing wheel. If you're worried about the strength of the 1/2" shaft, try that.
25-01-2012 13:43
MrForbes
Re: pic: Fisher Price gearbox
The shaft is 3/8" hex, with the ends turned to fit into the 3/8" ID bearings. The older FP first stage gear happens to have a 3/8" hex hole in it.
I was thinking we might step it down to 5/16" where it enters the 1/2" shaft, or possibly make a larger diameter coupler to fit over both shafts (for example, by turning the end of the 1/2" shaft to 3/8", and using a short length of 1/2" od 3/8" id steel tube)
25-01-2012 13:50
Tom I
Re: pic: Fisher Price gearbox
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Originally Posted by squirrel
The shaft is 3/8" hex, with the ends turned to fit into the 3/8" ID bearings. The older FP first stage gear happens to have a 3/8" hex hole in it.
I was thinking we might step it down to 5/16" where it enters the 1/2" shaft, or possibly make a larger diameter coupler to fit over both shafts (for example, by turning the end of the 1/2" shaft to 3/8", and using a short length of 1/2" od 3/8" id steel tube) |
Okay, glad to see you guys are thinking about connecting the two the right way. Let me know how it all comes together! (It's kinda scary how our two designs are similar... our turrets are basically the same as well)
25-01-2012 14:25
ToddF
Re: pic: Fisher Price gearbox
I suspect this is one of those cases of design convergence around a common goal. We are doing something similar, except using a steel center gear with a 3/8" bore keyed to a 3/8" dia wheel shaft. I don't trust that a plastic gear will hold up to the shock loading the gear mesh will see when the balls are fed into the shooter.
25-01-2012 15:10
Tom I
Re: pic: Fisher Price gearbox
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Originally Posted by ToddF
I don't trust that a plastic gear will hold up to the shock loading the gear mesh will see when the balls are fed into the shooter.
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25-01-2012 15:39
Matt C
Re: pic: Fisher Price gearbox
On the bright side, Andy Mark now makes the CIM-Sim. We've got one year and with two motors on it she screams like a banshee.
http://www.andymark.com/product-p/am-0932.htm 
25-01-2012 16:03
ToddF
Re: pic: Fisher Price gearbox
If only you could actually buy one.
I've come to the conclusion that the only way to get a robot done ahead of time is to drop tons of cash on transmission components before the season starts, and hope they are legal.
25-01-2012 16:05
Matt C
Re: pic: Fisher Price gearbox
I guess we got lucky, we purchased ours last week.
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