Need ideas for final semester project

  • Thread starter snaz_86
  • Start date
  • #1
7
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Its me again.
I need recommendations for a motor and power supply to make a cordless grass trimer that uses battery..anyone?
 

Answers and Replies

  • #2
What do you want to do with grass trimer? Are you looking for specific power outputs, effeciency, materials in construction, etc?
 
  • #3
russ_watters
Mentor
19,864
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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.
 
  • #4
7
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Ok i have problems finding what components and parts...Can anyone give me an exact motor and battery specification for a cordless grass trimmer?
:cool:
 
  • #5
15
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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 dont 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
 
  • #6
Danger
Gold Member
9,607
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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.
 
  • #7
1,490
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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/" [Broken]
 
Last edited by a moderator:
  • #8
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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.
 

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