Hello,

can someone tell me if the am planetary gear box from andy mark and the fisher price motors will work for a shooter. I think we want a 1:5 gear ratio but I don’t know what the gear ratio for the fisher price and andy mark box is.

Hello,

can someone tell me if the am planetary gear box from andy mark and the fisher price motors will work for a shooter. I think we want a 1:5 gear ratio but I don’t know what the gear ratio for the fisher price and andy mark box is.

http://www.andymark.com/Gearboxes-s/55.htm Start looking at the gear ratios. All of them are freely available.

With the ratio you’ve expressed, 1:5, you’re planning to gear the motor *up*. I don’t think you want to do that (the FP already spins at 20000 RPM, give or take a few). A 5:1 is what you’re more likely to find (same gearing, just down instead of up).

With respect to your initial question, will it work for a shooter, that’s something that is way too wide open to make any fruitful comment on, other than that it depends what type of shooter. (I could make a number of assumptions, but I think you know what happens when you assume…)

Could you please tell me what the gear ratio would be for the fisher price motor with the am planetary gear box??

Specifications:

```
Weight: 0.63 pound
Outside dimension: 2.5 inches
Shaft diameter: 0.313 inch, with 2mm keyway
Materials: body is aluminum, shaft is 4140 steel
```

** Reduction: 3.67:1**

jp, if you’d like to find out whether it will work for the shooter, do this.

Talk to your physics teacher (or someone who knows basic trajectory physics) and figure out how fast and at what angle you need to launch a ball to make it travel the distance you’d like.

Next, you need to make your shooter wheels spin at the appropriate speed. If you know the free speed of the motor you are using (FP, around 19600 RPM) and the gear ratio 3.67:1, then at full speed it will spin your wheels at Free_Speed *.8 (80% efficient) / 3.67 = RPM.

Next, if you know the diameter of the wheel you are using, you can calculate the circumference, and use that plus the RPM to calculate the surface speed of the wheel.

Since, theoretically at least, the ball will leave the shooter at the rate the wheel is spinning, you can now figure out if your wheel will be going fast enough to shoot the ball the distance you need.