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 Using my Little Orphan Annie Secret Decoder Ring, I have determined that the game hint reads:
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This is the base of a really basic robot that we are building this summer. It has 4 fisher price gearboxes with 8 inch Skyway wheels attached. We are hoping to take off parts of the robot and have rookie members rebuild it. Fisher price gearboxes are plastic, but we have plenty of them, so if they break, it's perfectly fine. The rest of the robot should hopefully be done soon and the pictures will be uploaded. What do you think? Any ideas?
Discussion
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24-08-2007 18:07
Greg Marra
Re: pic: Test/Training Bot
Don't ever try to push something, unless you like that "Fisher Price" smell 
Fisher Prices have a wonderful tendency to burn themselves out in a way that can be smelled all the way across the field.
24-08-2007 18:15
Grant Cox
Re: pic: Test/Training Bot
Keep this around, it can be used later on to help out new drivers. We used the drive base from last year's robot to play "defense" on this year's bot to give the drivers some extra practice. You could do something similar with this.
24-08-2007 18:50
AdamHeard
Re: pic: Test/Training Bot
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Originally Posted by Greg Marra
Don't ever try to push something, unless you like that "Fisher Price" smell
Fisher Prices have a wonderful tendency to burn themselves out in a way that can be smelled all the way across the field. |
They're using 8" skyways which have a pretty poor coefficient of friction. Less than 1, but for this example I'll just use 1.0 as a safety factor.
assuming the robot weighs 60 lbs fully loaded, it will take 60 in-lb per gearbox to slip the wheels.
Each gearbox puts out ~460 in-lb (the '07 FPs, I know they're all different... but in this example the margin is big enough).
So, at 60 in-lb, the FP will draw 8.3 amps... they'll be fine. but if we double it to 120 lbs, they'll draw 16.6... which is a little more iffy.
24-08-2007 20:16
Rob2713g
Re: pic: Test/Training Bot
Thanks for the response. We won't try pushing anything, unless we decide to demonstrate what happens if it stalls.
We realized the fisher prices are really nice for quick and simple prototyping. We simply ground down part of 4 white "teeth" and notched a slot in 2 other "teeth" on the fisher price, and the skyway slid right in. The skyways aren't epoxied or anything (although we might decide to do that later), but they do have spacers on the other side. Out of curiosity, how are the fisher prices really supposed to attach to stuff? We liked the simplicity of the gearboxes so much that we are using it in our first version of a swerve prototype.
24-08-2007 21:03
AdamHeard
Re: pic: Test/Training Bot
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Originally Posted by Rob2713g
Thanks for the response. We won't try pushing anything, unless we decide to demonstrate what happens if it stalls.
We realized the fisher prices are really nice for quick and simple prototyping. We simply ground down part of 4 white "teeth" and notched a slot in 2 other "teeth" on the fisher price, and the skyway slid right in. The skyways aren't epoxied or anything (although we might decide to do that later), but they do have spacers on the other side. Out of curiosity, how are the fisher prices really supposed to attach to stuff? We liked the simplicity of the gearboxes so much that we are using it in our first version of a swerve prototype. |
They cut an octagon that fits into the white part perfectly, then clamp down the white part with a hose clamp. Then they cut whatever kind of bore or shaft interface they desire. I have seen many teams (including us) copy this over the years, and If done correctly it never fails.
PM me and I'll send a drawing.
EDIT: what role do the FPs play in the swerve? If you plan on steering the modules with them, you're probably better off just using the globe motor. Smaller, and much easier to work with (yet, it is still plenty powerful for the job).
24-08-2007 22:35
Rob2713g
Re: pic: Test/Training Bot
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Originally Posted by AdamHeard
EDIT: what role do the FPs play in the swerve? If you plan on steering the modules with them, you're probably better off just using the globe motor. Smaller, and much easier to work with (yet, it is still plenty powerful for the job).
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24-08-2007 23:00
Dan Petrovic
Re: pic: Test/Training Bot
Why not CIMs? CIMs wont heat up as quickly as FPs. If you plan on using FPs to drive with, bring plenty of spares.
25-08-2007 13:24
AdamHeard
Re: pic: Test/Training Bot
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Originally Posted by Rob2713g
The Fisher Prices are the drive motors. They are mounted in a similar way as on the Test/Training Bot. We are building next Tuesday and I'll be sure to take some pictures and upload them. We bought a backup AndyMark gearbox, but never had to use it, so we will be steering the prototype swerve modules with it. We would like to eventually put Dewalt gearboxes on each module, but are not sure we will be able to make them. It would be great if we could look at, borrow, or buy one as an example. Thanks for all of the feedback!
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You definitely don't want to use FPs as the drive for a crab (especially during the season), they just couldn't compete with any other drivetrain; Unless something drastically changes, we only get 2 per season.... Also, the stock gearboxes have way too much reduction to be in the drive of a robot (unless it's just a demo like above). You'd be moving at 3-4 fps, totally negating the added maneuverability of a crab. Your best bet at getting a good crab is a CIM in each module with the globes steering.
25-08-2007 15:37
Rob2713g
Re: pic: Test/Training Bot
We won't use Fisher Price gearboxes and motors in the actual drivetrain. But for a first prototype they work pretty well. For prototyping, they already come with a gearbox, which is ideal because of limited access to manufacturing (especially during the summer) and we don't have to buy anything. Once we see if it works, we can let our programmer start having fun, while we begin building a more advanced prototype.
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