Gear Specifications

[Spirator]

3132 here,

Hey everyone. It's time to belt down and start designing the kicking mechanism. I'm planning to use the Fisher Price motor with another gear to pull back some surgical elastic.

We're hoping that the other gear is at least 3-4" in radius. We have people who might be willing to machine some for us, but I've got no idea on how I'm going to provide them the right specifications for the machining process.

Is there any software that can help me in this process?

[MrForbes]

Instead of using one big gear, how about using a few small gears? The gears that come in the plastic transmission are designed to work with the motor, after all.

[Spirator]

Our mechanism doesn't work like that. It's necessary to use one big gear.

[MrForbes]

Another approach could be to use a large sprocket, and one stage of the FP gearbox. We did something similar last year.



this is the gearbox we made, using two sheets of aluminum, some hex shaft, two bearings, and one gear from the FP gearbox. The second plate is not shown, nor is the plywood spacer.

here is the gearbox driving a larger sprocket with a chain.

I don't know if this idea will help you, but it could be easier to find a premade pair of sprockets, than to get a gear machined?

[Spirator]

Does the chain fit nicely on the FP motor or will I have to make modifications?

[MrForbes]

The chain will not fit on the motor, you'll need to make a shaft to fit into an FP gear, and then get a sprocket to fit on that shaft.

Do you have the speed/torque aspects of the design figure out yet?

[Spirator]

My current design would output 1.35Nm (0.995707395 lbf/ft) of torque at 1250RPM from the big gear. The FP motor would be spinning at 7500RPM at 225mNm (0.165951232 lbf/ft). Would 1.35Nm (0.995707395 lbf/ft) be enough to pull back the surgical elastic?