Fisher Price used on Arm?

[eddwahd]

I'm extremely sorry if this thread was already made, but...

How do i attach a sproket onto a fisher price motor for use to rotate my arm?
[i heard fisher price motors are the strongest?]

The only way i could think of was to detach the motor from the given gear box and gear down the motor myself. Please i have been thinking about it for three days and i am still lost!



BTW i read this forum everyday, and i see nothing on my problem )=

[Max Lobovsky]

Couple ways. You can get a hold of the FP couplers that were in the kit last year. (for some reason, there is an inordinate amount of FP toy cars in the trash. You can find one) it isn't terribly difficult to bolt a sprocket to one of those.

You could also cut slots in a sprocket to mesh to the white piece on the FP gearbox. be careful if you put a lot of tension in the chain though or try to get some more support for the sprocket; I'm not sure about loading that white piece radially.

[sanddrag]

Perhaps you could get a planetary from www.andymark.biz and then use the kit gearbox.

[eddwahd]

As much as i would like to purchase a pre-made gear box from andymark /=,

i really want to do my own gear box for my fisher price motor.

Does anybody know where i can purchase cheap, reliable planetary gears and small gears to construct my own gear box?'

I understand i have to gear down at least 124:1 to use the fisher price motor, so im planning on using 80 teeth gears with 13 teeth gears 3 times, but i don't understand the terms of a gear. What are the specs for the FP motor gear(without the given gear box)? [i.e. bore, face width, pitch diameter, face width, Diametral Pitch. hub diameter, Outside Diameter, pressure angle?


Oh yeah, Max, about your reply, i do have a coupler from 2004 but is bolting a sprocket onto that palstic sprocket strong enough?


I'm still uninformed )=

[sanddrag]

SDP-SI sells internal gears which I assume could be used as the ring gears in a planetary set, but you may want to confirm that with an engineer.

Is this the way to make a planetary? Buy an internal gear and then some small spurs for planets and sun?

[SteveO]

Or you could use belts pulleys

[russell]

Dont use the FP motor for an arm. Arm motors generally have to take a lot of stress, and the FP motors have plastic gears. Thats just what im thinking. Belts wouldnt work for the same reason obviously.

[eddwahd]

Originally Posted by russell

Dont use the FP motor for an arm. Arm motors generally have to take a lot of stress, and the FP motors have plastic gears. Thats just what im thinking. Belts wouldnt work for the same reason obviously.

What motor do you suggest we use?

I was thinking the only other motor that could handle the torque might be the globe motor;then again, i would need to buy my own gears and machine my own gear box. right?

[SteveO]

I would have to disagree with russell there. The Fisher Price motor is definitely capable of powering an arm mechanism; plastic gears shouldn't be a concern if you are building your own gearbox.

[Ryan Albright]

we used fp last year in our arm to pick up the big ball. If you want to use them you need to watch the heat on them. We burnt threw a few. YOu might even think about building heatsinks for them and invest in one of the guns that takes the heat measurements. Fps can be done if they are monitored closely and checked after every match

[Gdeaver]

We're considering the Fisher price gear box for the arm. It needs additional reduction. Heat is only a problem if you over load it. The back drive problem is my main concern. We're looking at different brake designs.

[MattB703]

Originally Posted by Gdeaver

We're considering the Fisher price gear box for the arm. It needs additional reduction. Heat is only a problem if you over load it. The back drive problem is my main concern. We're looking at different brake designs.

We have had good luck in re-using the plastic gears from the F-P gearbox in a custom made gearbox. We basically made our own side plates. (You'll need a mill for this) Don't use the last set of gears on the F-P gearbox. Instead, make a shaft with a hex shaped outside to fit into the second-to-last gear from the F-P assembly. This shaft will then rotate with the second-to-last gear and it can be used as your output. You'll need more reduction after that. It the past we used a big sprocket (about 10") attached to the arm and put a small sprocket on the gearbox output.

To calculate the final reduction you will need to figure out how much moment (torque) you will have at the base of the arm using the length and weight of a fully loaded arm. A good rule of thumb that I like to use is to keep the motor load less than 1/3 of the stall torque. So, if you divide the required toque at the base of the arm by 1/3 the stall torque of the F-P motor you will get a target for the overall reduction.

Matt B

[Andy Baker]

Originally Posted by eddwahd

As much as i would like to purchase a pre-made gear box from andymark /=,

i really want to do my own gear box for my fisher price motor.

OK, fair enough. Here is some advice:

Look inside of the Bosch gearbox from last year (or previous years), and you will find all of the gears you need to build your very own single-stage reduction gearbox. The ring gears, planet gears, and pin-plate that holds the planet gears are all in there. Unfortuneately, the sun gear (pinion) has a larger id (5mm), as the Bosch shaft was bigger than the F-P motor shaft.

These are the parts used on the TechnoKats last year to make our own Fisher-Price gearbox. We had to fabricate a housing, an output shaft that mated up with the pin-plate, and a new 15-tooth gear (we used 36dp). We used an 8mm id needle bearing to support the output shaft. This bearing failed during our summer competition (after 3 competitions of qualifying and elimination rounds), so Mark and I simply added a second bearing in our AndyMark design.

Good luck,
Andy B.

[Tom Bottiglieri]

A Fisher Price Motor with stock plastic gearbox SHOULD hold up to your basic arm needs. This is relative to what you are doing, though. If you are trying to pick up 60 pounds on an arm with a 60" swing, with no reduction to the rotation axle, you will stall the motor, probably smoking it, and possibly grinding the gears inside the plastic gearbox.

I recommend using JV N's motor calculator to find out how much torque your arm requires, then choosing the motor in the kit with the corresponding peak power.

(For reference, many teams were able to hang 130 pound robots off a FP motor with stock gearbox, without killing the motor or the gears.)

My opinion is.. make sure you need the power of the FP first. If you dont, opt for the van door. It is more reliable and not as picky as the FP. But, if it turns out you need the FP, make sure you give yourself about a week of testing on the arm. Then you can find any quirks, and see if something will go wrong. If the motor overheating becomes a problem, limit the voltage to about 9.6 - 10.5 volts. If the gearbox begins to grind, fabricate your own, using either nylon or aluminum side plates, and gears ordered off the INTERNET. You can construct this gearbox in any high school machine shop. If needed, post or search to get info about making your own custom FP gearbox.

[Nitroxextreme]

im new to this
but couldnt you use the window motor or maybe 2 window motors to power a fixed shaft at a joint