FOR FREE ASSEMBLY DRAWING SHEETS CLICK HERE!
This project was popular with the kids - it's a
2 x 250 Watt electric motor
driven kart and got a lot of use before they grew too big for it.
As with most of the kids' buggies my aim was to try to
build the kart using mainly non-specialised
tools and
materials. The main structure is glued and screwed timber and other features
include ackerman geometry steering, rear band brakes, rear
wheel drive differential action and forward and reverse drive..
The
propulsion is from a rear mounted two
stage reduction gearbox which has built-in band brakes direct acting on
the wheel axles. Several key
strength components of the kart are made of
steel and
throughout I've made use of standard stock engineering components such as
bearings,
bright steel bar, steel flat,
gears,
sprockets etc.
Importantly, the design includes padded seat cushions... mustn't forget
rider comfort!
The
gearbox design is described in more detail here
- it is powered by two 250W permanently engaged (no free-wheeling)
24V
DC PM electric motors. It is efficient, reversible and back-driveable
and, with the right choice of
motor controller, can provide some
re-generative dynamic braking for the kart i.e. the motors slow the kart
and the energy produced is passed back into the
batteries. Built-in band brakes act
directly on the drive axles and provide the main mechanical braking
independently of the electric drive. The independent drive to each rear
wheel provides effective differential action when turning and traction
from both rear wheels allows driving on mown grass, hard gravel drives
etc.
The wheels are inexpensive pressed steel
with 10"
pneumatic tyres. The steering uses a modified Ackerman geometry
with a direct coupling to the column and steering wheel.
Brakes and accelerator are
foot operated.
The center of gravity of the go kart is
very low
because of the low slung batteries and the low seating position and this
makes it very stable on cornering. We found that gearing to produce a maximum
speed of about 12 mph is probably the maximum for use on good (hard and
flat) drive surfaces. We could chose to reduce the speed by building in
higher reduction gearing in the drive box. This would have the effect of increasing the drive torque available at
the wheels and make the racer better able to handle cut grass lawns,
hard gravel driveways etc but at a lower speed. 12 mph might
not sound much but, I'm sure you'll appreciate, it is plenty for a child driver
- see the notes on safety guidance.
The
electrical system is standard for small electric vehicles ie motor(s), motor
controller,
batteries
and speed/reverse/ignition controls. The controller used is the 24V 75 Amp
Vortex
controller from 4QD which has worked very well. Room for four 12 V 17 AmpH
deep cycle batteries wired for 24V was built-in to the structure gives a
continuous running time between charges of about
1 hour. However the time between charges depends a lot on the
vehicle gearing, condition of drive surfaces and how hard the kart is
driven.
We tested the racer on a mainly gravel circuit at full speed most
of the time which produced a lot of troughing in the gravel on cornering and a
discharge time of about 45 minutes - this demands power though and is
hard on the motors and probably shouldn't be advised. On flat, hard and smooth drive
surfaces (tarmac, concrete etc) the torque demand on the motors and
hence their current draw is much less with a consequently longer
battery life.
Here are some short movie clips showing
the kart prototype in action........
Have a look at the general
arrangement of the kart to get an idea about its size and
layout. The drawing is password protected and the password
is:
sample
(click on the image below)
For a more detailed look at the plans go to our
plans walk-through pages or.....
Online plans Previews for the 500W
mini-kart are now available here -
FREE ASSEMBLY SHEET PREVIEWS. These show the assembly drawings from
the set and will show you the build principals and methods used - for
the full plans set which contains all the detailed part sizes, final assembly drawing sheets and the component & material
buy-list go to the paid-for plans page.
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copyrighted, If you'd like more information or have any
comments please contact me at
READ THE SAFETY
GUIDANCE HERE
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