Need ideas for final semester project

[snaz_86]

Its me again.
I need recommendations for a motor and power supply to make a cordless grass trimer that uses battery..anyone?

 

[Plastic Photon]

What do you want to do with grass trimer? Are you looking for specific power outputs, effeciency, materials in construction, etc?

 

[russ_watters]

I'd start by reverse-engineering an electric grass trimmer and seeing what kind of motor/how much power it uses. Then I'd look into existing cordless power tools and see if their capabilities come close to what you are looking for.

 

[snaz_86]

Ok i have problems finding what components and parts...Can anyone give me an exact motor and battery specification for a cordless grass trimmer?

 

[nobb123]

A grass trimmer is a pretty simple device. You just need a battery connected to a fast spinning motor. The motor head has a piece of plastic string (I don't know the official name) that spins very fast and trims the grass. To keep it simple, you might want to use a deep cycle lead acid battery hooked up to a motor which accepts 12 volt input. Charging the lead acid is very simple, you can get a specialty charger, or build your own 13.8 volt power supply

 

[Danger]

It can't just be a fast-spinning motor; you have to have some serious torque behind it as well. Otherwise, it will just stall out. If you have to make it from some other appliance/tool, I'd recommend a router.

 

[Artman]

I imagine that a cordless drill would work for a motor and battery system. The drill would have to be altered to remove the gearing, but it would probably have a rheostat to allow variable speed and the battery and charger already paired to the motor.

They are fairly cheap now also, only about $20.00.

Here is a site showing a reverse engineered corded drill, you can see the gearing:

http://www.bergen.org/AAST/projects/Engineering_Graphics/Drill/"

 

[Artman]

Here are the specs for a Black and Decker Cordless grass trimmer:

Specifications: Voltage 12 V. Revolutions/Min 6800 rpm. Cutting Path 12". Line Diameter .065". Weight 10.3 lbs. Feed System AFS.

And here are the specs for a cordless drill:

SPECIFICATIONS Voltage 12 DC Chuck Size 3/8 in. No Load Speed 0-400/0-1400 RPM Torque 280 in.-lbs.

The drill speed is after the gearing, so I imagine much higher rpms could be achieved without the gears, not sure what the ratios are.