Electric Victa Mower Conversion Build Thread-The Electric Motor
Whether you are doing an Electric Car Conversion, Electric Bike Conversion or an Electric Mower Conversion like this one, the Electric Motor is one of the major components of the conversion. The Electric Motor is the heart. The previous post discussed the fate of the 2 stroke engine and this post discusses the requirements of the electric motor for this electric conversion, what motor was selected and how it was evaluated.
What features and requirements was I looking for in an Electric Motor for Vikta Da Stinka Electric Mower Conversion?
The requirements and features I was looking for in an electric motor for this Electric Mower Conversion were:
- Power and Torque – 3hp was my preference so that I could easily cut long grass, but anything over 1 hp would have been sufficient. I had read in Issue 105 of ReNew magazine of a similar electric mower conversion where they successfully used a 500 watt (0.7hp) electric motor.
- A physical size that was no bigger than the original 2 stroke stinker it will sit on.
- As cheap as possible – I wanted the whole project to cost under USD $400. Any more than that, then it is not economically viable as one could buy a decent battery powered Stihl Electric Mower for that price.
- That the motor could be mounted on the motor face which would permit it to be bolted into an adapter plate.
- The motor could rotate in an anti-clockwise direction.
- A shaft where a coupler could be attached.
- Something that would easily run without complex electronics. This limited choices to simple brushed DC motors.
What Electric Motor did I end up using?
After putting the word out there that I was looking to convert a mower to electric, I was given a Hitachi GSB107-06 Starter Generator rated at 12V 0.9HP. This motor was previously used as a starter motor and alternator for a gas engine and are often found on Yamaha Golf Carts. What is interesting is that there appears to be a set of terminals, used for starting and there are a pair of thin wires which I assume is used for the generator/alternator component. For this Electric Mower Conversion, the generator component will not be used as there is no other mechanical or rotational energy source to move the motor.
Although I did not pull the Starter Generator apart, it appeared to me that the starter part of the motor was a series wound brushed DC motor, especially with labels such as F1,F2,A1 and A2 stamped next to terminals and the external cable that connected A2 to F1. Although, I did not open up this motor, I have often found with motors that F1 & F2 typically denote the ends of the field windings whilst A1 & A2 typically denote the ends of the armature. There was also a DF terminal with two wires coming out from it. Typically, that is the dynamo field for charging purposes, but this wire was not required for this Electric Mower Conversion.
How did I check this Electric Motor?
Once, I got possession of the Hitachi GSB107-06, before doing any work on it, I checked to see that the shaft would rotate when power was applied. Using a 12 volt battery and jumper leads, power was applied to A1 and F2. Since, it behaved like a series wound brushed motor, it did not matter what polarity was applied to those two terminals. Looking at the motor from the output side (where the pulley normally went), the shaft rotated anti-clockwise which meant that looking at the motor from the rear casing, it rotated clockwise. This meant that when connected to the mower in the method I was envisioning, it would rotate in the correct direction. (Note: To change the direction the shaft rotates, remove cable connecting A2 to F1 and instead connect A1 to F2 and apply power to A2 and F1.)
I was not able to measure the speed of the Hitachi GSB107-06, but without using a motor speed controller, I had to watch that the motor did not speed up with no load, otherwise there could have been a risk of it self distructing – something to watch for when using series wound motors with no load.
I was satisfied that the Hitachi GSB107-06 could be used for this Electric Mower Conversion so the next step was to work out how to mount this Electric Motor to the mower.
This is Al Bunzel signing out.