In
the vehicle and flight sim projects shown on the site I've generally found the use
of DC permanent magnet motors to be least expensive and
most satisfactory option – these are not the only type
of DC motor that can be used in small karts and EV's but generally they are easy
for the DIY-er to get a hold of, are relatively
efficient, physically compact and many can be used for
reversing and dynamic braking applications.
I've tried a range of types from DC
hydraulic pump motors to wheel chair motors but have
settled now mainly on imported Chinese built DC PM
motors intended for
electric scooter and trike spares.
Besides being designed for traction duty on small
vehicles these motors are considerably less expensive
than similar powered European or US built motors. Some
of the smaller 250W units can be picked up on Ebay for a
few pounds/dollars - which considerably reduces anxieties about
accidental overloads causing them to burn out.
They are relatively efficient (75
- 85%), especially some of the larger power units, they can be driven in both forward and reverse at
variable speeds and come with a radial load bearing
output shaft and usually with a roller chain drive
sprocket ready to be mounted on your transmission. This
is an attractive package for the DIY vehicle builder. For
the designer it is also possible to obtain technical
performance data for the motors directly from the
manufacturer's web site -
try here (connection
to this site can be unreliable), or
here as an alternative supplier for some models. Powers available range from
250W up to 1200W per motor for 24V, 36V and even 48V
DC supplies. Most of the motors I've used from this
range have rated speeds between 2500 and 3000 rpm and as
such are not suitable for direct connection on to drive
wheels - this has to be done with at least one (possibly
two) speed reduction stage(s) to bring the speed down and
the torque up to that required at the wheel. However a
number of these motors are available with built-on gearheads
and these versions are an attractive alternative to a DIY
speed reduction build.
Mounting
method depends on the motor, as you can see some have
mounting feet attached, the larger motors (above right) can be
front or rear face mounted or conveniently can be
secured to a support using large diameter hose (jubilee)
clips, see left. This by far is the easiest way to
secure them - check out the plumbing/central heating
section at your local DIY store for large hose clips.
It is worth mentioning that all these
motors will generate heat as a natural by-product of their
operation and will heat up in use, especially when run
hard. Surface temperatures can easily become too hot to
touch comfortably and care should be taken. In
particular they should be mounted where a cooling flow
or air can be provided - it is best not to fully enclose
them although it is wise to provide some form of weather
protection for types with end face ventilation holes.
The motors shown are from the MY1016 and
MY1020 families of electric motors made by Unite Motor Co.
in China and widely imported for electric scooter and trike
spares. Check the suppliers page for some sources of these
motors.
Electric
motors with integral gear heads are also available and can
simplify the transmission design in some projects. On the
DIY motion Cockpits I've used 24V 200W Unite motors with worm
gear boxes to provide some degree of load-holding when the
power is removed. These give a compact high speed reduction
design that can be very useful. Motors with worm gearing can
have fairly large reduction ratios and generally the bigger
the reduction the more the tendency for the gearbox to
resist back driving from its output shaft. In vehicle
applications this can be a problem if you are looking for
the motors and electrical drive to give smooth braking
response. Other gear head motors will use other gear types,
eg single or double straight spur gear reductions and these
will tend to have a lesser speed reduction but are more
capable of being back driven and may be a better choice for
dynamic/regenerative braking in electric vehicles.