Open HoodDashboard
Owner's Other EV1975 Kawasaki KZ400
LocationVermont United States map
Vehicle1967 Montgomery Wards Garden Mark 7hp
This is a converted lawn tractor. No mowing deck
(I hate mowing!), just for pulling and for fun.
Maybe to be in a parade now and then. It had the
right shape to become a Tonka tractor, so I
painted it that way.
MotorMars ME 0709 Permanent Magnet DC
Light weight, high efficiency design.
Designed for 24-72 VDC battery operated
equipment. Capable of 300 amps peak (1
minute) and 125 amps continuous. Totally
open, fan cooled motor. Motor weight of 36
DrivetrainOriginal 3 speed transmission + one reverse.
Original belt drive pulley on transmission,
slightly smaller on motor. Maybe a 7:9 gear
ControllerAlltrax Alltrax 7245
Followed the instructions and hooking it
was doable without too much trouble. I
added a disconnect switch on the brake
pedal. It immediately shuts of the
controller and will not allow throttling
up until I first throttle back down to
zero first. Alltrax customer service was
great help when I sent them the wiring
diagram. Same with Carl from EV Drives
where I bought this controller almost 10
years ago. He still answers the odd
question I have now and then.
Batteries24 CALB/Skyenergy 40Ah, 3.20 Volt, Lithium-Ion
System Voltage72 Volts
Told them what I need to charge when I bought
it - they sent it. The batteries and charger
were installed in a previous motorcycle
HeaterThe sun will heat up that black seat nicely.
DC/DC Converter Something from China
Searched for DC/DC converter for 72V to 12V
on ebay - found it, bought it, it works.
InstrumentationAnalog volt meter for aesthtics. Digital
voltmeter hidden under little metal lid.
Emergency battery disconnect modified to
look like a choke button. Key switch.
Custom-built throttle lever. Lever is
original but everything inside is not. 0-
5kOhm potentiometer with carefully
calculated 3-d printed gears to achieve
exactly 310 degrees of potentiometer
rotation with lever. Works like a charm.
Top SpeedNot relevant but seems faster than a regular
lawn tractor when in 3rd gear.
Seating Capacity1 adult
Curb Weight0
No idea. A bit heavier than before since the
original had only a 7hp engine in it. The
batteries and motor combined are certainly
heavier. Of course, the mowing deck and a
bunch of other stuff are gone now.
TiresI wanted fairly narrow front tires because
that is how it used to be in 1967. Took me
forever to find rear tires with matching
tread pattern.
Conversion TimeAbout a year of puttering around.
Conversion CostNo idea. Tractor was $65. Parts were from
previous and discontinued project and were
just sitting around. Several thousand dollars
if you buy it all new.
Additional Features
It is a rare tractor model that now looks like a cute, little Tonka

code by jerry