Motors are the
driving force behind your R/C car. You
need to take care of your motor, and treat it with respect.
In this section, I’ll give you some basic, no nonsense guidelines for
caring for your motor, and some simple rules for choosing your motor once you
graduate into the modified ranks. I’m
not a technical guru, and I don’t intend to get technical here.
Let me just say this: I’ve
raced at the top level of modified in Queensland and Australia with some success
using exactly the guidelines I’m going to present to you here.
Some may disagree with my assessment, but I’m here to tell you this
stuff works in real life - good enough for most of us.
9.1
Motor Care
Johnson
540: 540
motors are very easy to care for. After
each race, brush the loose dirt/dust off the endbell.
After every second or third race, add one drop of light machine oil to
each bushing (Mobil One is ideal but any light machine oil will do the job). After every second race meeting, take the motor out of the
car, and spray it out with R/C motor cleaner (from Reedy, Orion, Trinity etc).
Don’t run the motor whilst spraying it, don’t dip in water, or
shellite or any other such things. When
you’ve finished spraying out the motor, add a drop of oil to each bushing and
work the oil in (by turning the shaft by hand a few times).
Then add a drop of Break-In fluid or Commutator drops to each brush
(inside the motor) and run on a four cell pack for about 30 seconds.
Now replace in your car. That’s
it. Simple, quick, and reliable.
If you want more performance from your Johnson 540, you can use
commutator drops (again, stick with companies like Trinity, Orion etc).
My advice would be to use them sparingly - certainly only one drop at a
time - and preferably only on big race days.
For your club racing you should be pretty right without them.
Once you’ve
graduated from 540, you’ll move either into a stock or spec-modified class
(maybe 19T) or full blown modified. Now
there’s heaps more to maintaining a stock or modified motor than a 540, but
again - I’ll tell you how I do it - simply, quickly, and relatively cheaply.
Race
Day maintenance of
either stock or modified modified motor is not much more difficult than a 540. After about every three races or so, pull the motor from the
car. Start by brushing loose dirt
from the endbell, and can. Next,
remove the brush springs and slide the brushes out.
Spray a little motor cleaner spray onto a cotton bud, and slide the
cotton bud into the brush hood - pressing firmly to ensure good contact with the
commutator. Now rotate the
commutator a couple of times. Repeat
this process about 3 or 4 times (with clean cotton buds each time) ensuring that
you use both brush hoods. Now get a
new cotton bud, and again, spray with motor cleaner.
Use the cotton bud as a cleaning stick - wiping the face of the brush
clean of any debris or carbon build up. Take
a very fine points file (or a
specialist comm cleaning stick from Trinity or similar) and smooth the sharp
edges of the brush. Don’t do this
on your own for the first time - ask someone experienced to help you.
Put the motor back together and back in the car.
That’s it. Don’t oil
bearings, or spray out the insides of the motor with spray - you can do more
harm than good.
After every second race day (or approximately 10 runs), you should disassemble the motor entirely, and give it a full clean. Here’s a basic procedure to follow:
1. Remove the motor from car, brush off any loose dirt/dust
2. Remove brush springs and slide brushes out of hoods
3. Take hobby knife and mark can and endbell to ensure you get the timing right when you re-assemble the motor (no need with stock motor as they are fixed at 24 degrees)
4. Loosen timing ring screws (on top of motor) taking care not to damage the capacitors. Twist endbell and remove from can. Place the complete endbell on a clean, clear section of your work bench next to the brush springs.
5. Take the motor shims off the top of the armature and place next to the endbell. Be sure to make a note of how many spacers there are and what order they may be in. There will probably be a fibre washer closest to the commutator - this is to trap oil and grease that may leak down from the endbell bearing.
6. Remove the armature by hand from the can. Set it aside on the bench after removing any shims from the shaft. Check inside the can for more shims (they’ll often fall off the shaft and stick to magnets) and place all shaft end shims together on your clear area. Set the can down next to them (again remember to count how many shims there are on that end)
7. Liberally spray the armature with motor cleaner until runoff is clean (do this over a rubbish bin, or outside - it’s not good stuff to get on your mum’s carpet). Spray a cotton bud and carefully clean all areas of the commutator.
8. Use a clean tissue to wipe out dust and dirt from inside the motor can and endbell. Don’t use spray.
9. Check motor bearings for wear and dirt. To do this, put the armature through the bearing from outside the can or endbell (do one at a time) and spin the armature. If the armature spins freely and quietly - you’re fine. If it grinds to a noisy, quick halt - chances are your bearings are either very dirty, or just plain stuffed.
10. You can try cleaning your bearings if you like. Remove the bearing from the can/endbell using a ‘Motor Bearing Tool’ from Trinity or similar. Then clean as per other bearings in your car. Oil lightly with a good quality bearing oil (Mobil One is a good alternative) and replace carefully. If you’re not confident about this, ask for help. Note that in “stock” classes, removal or replacement of standard bushes is illegal – check this with your club as some do allow replacement, but at major/championship races you’ll need a standard motor
11. If you decide that the bearing is stuffed (or you try to clean it and it just doesn’t improve) then it’s time for new bearings. Replacement bearings are available from companies like Orion, or Miniature Bearings Australia and can be fitted using a Motor Bearing Tool. Again, if you’re not confident - you can ask for help.
12. When you’re done with all this - reassemble the motor - taking care to get the shims in the correct location, and get the timing back to original mark. At this stage I’d recommend fitting new brushes - although if your brushes are still smooth, clean and a nice consistent copper colour they’re probably ok. Look at the side of the brush - if it is discoloured at all (maybe purplish, blue or off-white) then it’s time to replace the brush - no argument. Solder new brushes on just where the old ones come off. As always - ask for help if you’re not sure.
13.
You’re done!
After two cleaning
cycles (about 20 runs), I’d recommend that you consider having your commutator
re-trued. This is done using a
purpose built motor lathe (often with a diamond tip).
Lathes can cost between $400 and $1000 so the odds are you won’t have
one yourself. Many hobby shops have
motor lathes and can do this for you - usually for about $5.
In fact, most hobby shops offer a full motor rebuild service - including
clean, retrue and replace brushes. Ask around.
Note that in modified
touring cars now the motor winds are increasingly wild, and life-span of the
motor is as a result increasingly short. With a very high performance modified
motor (say 9 turns or less) you should clean it after every run, and probably
re-true and replace brushes are no more than 5 runs.
The exception to this is the Orion/Peak V2 based motors which are
designed for longer life span, and motors fitted with some impressive brushes
from CS which are designed to do the same thing.
9.2
Modified Motor Brush Selection
When you’re using
your modified motor you’ll quickly discover that there are a range of motor
brushes available for you to use. These
might be called soft, hard, cut, timed, serrated, silver, copper etc. Pretty confusing. Let’s
try and give you some very simple guidelines.
Brush
compound: Some
brushes are known as hard, or soft. You
might liken brushes to tyres. The
softer the compound, the greater the performance, but the greater the wear rate.
With brushes however, the performance gain is small, and the increase in
wear is great. Only when you’re
seeking the ultimate little extra in horsepower is it worth considering a soft
brush. The fact is they’re
probably not worth the hassle. You
need to clean your motor more often, and change brushes more often - sometimes
after just 2 or 3 runs. I recommend
that you always use hard compound brushes.
Fine examples of these brushes are available from Ozcharge (#1130),
Trinity (Serrated Face Hard) and Corally (Standard Hard Brush).
If you’re desperate to use a softer brush - again these three companies
offer a good choice.
Brush
material: Brushes
are a copper colour (brilliant aren’t I).
That’s because copper is one of the ingredients of the average brush.
There’s a whole cocktail of other ingredients that go into every brush.
One of the more common ingredients is silver.
Brushes with a high silver content are generally expected to perform
better - although as with softer brushes there’s usually a trade off for both
brush and motor wear. Again, a
standard material, standard compound brush is the best choice for consistency
and life of the motor.
Brush
Shape: Brushes
can come with different shaped (or ‘cut’) faces. Some have half the face cut away, others have a slot across
the centre, or a hole drilled in the centre.
There’s even a brush called the ‘H Cut’ (guess what the face of
that looks like!). All of these
‘cuts’ are designed for different purposes - often for US style ‘Stock’
racing, or even for on-road. For
most racing purposes, you are better off sticking to a standard, full faced
brush. Some otherwise full faced
brushes in recent years have a series of small grooves, or serrations across the
face. These serrations are designed
to help the brush run-in faster. These
types of brushes are ok.
Lay
Down Brushes: A
standard modified motor takes standard ‘upright’ brushes.
That describes the brush that is taller than it is wide. Some motors are available with ‘lay down’ brushes (like a
normal brush tipped on it’s side. Additionally,
some manufacturers offer ‘lay down’ conversion kits for standard modified
motors. In some conditions, lay
down brushes can offer a slight performance gain.
It’s hard to say when, where and what those conditions exactly are -
it’s mostly a case of experimentation.
In general, let me
say this. I very, very rarely use
anything other than a standard, full faced, hard, upright brush.
Many, many races around the world are won with this type of brush - and
you will never go wrong.
Note to that once
again this information does not apply to Orion/Peak V2 based motors.
These motors take a brush that is round/circular in cross-section and at
the time of writing are supplied only by Team Orion or Peak.
They supply two types of brush – and Enduro (good for up to 30 runs)
and a Sprint (more power but only good for about 5-6 runs).
9.3
Motor Selection
In 540, or spec
classes (such as 19T), motor choice is very, very easy.
Just take it out of the box and bolt it into the car and work out your
gear ratio. That’s it.
Stock motors
typically don’t vary too much – but some have slightly different
characteristics (more torque or more revs) and you may find one more suited to a
particular track. More importantly
you may need to vary gear ratios from one stock motor to the next.
When you’re racing
modified however, it’s a whole different kettle of fish.
Choice in motor wind is almost infinite and there are certainly no hard,
fast rules. There are, however,
some general guidelines to help you choose a good strong motor. Remember - these guidelines are general only - there will
always be exceptions.
The less turns of
wire on a motor (e.g. 11 turns
compared to 15 turns), the faster it will generally be.
However, it will also be generally tougher on batteries, and harder to
drive. Higher turn motors will be
easier on batteries, and generate more torque - allowing you to gear higher.
The more strands of
wire on a motor (e.g. triple compared to double), the more top end it will
generally have (very general statements here).
A multi-strand motor will generally be easier on batteries, and smoother
to accelerate. You’ll generally
be able to gear it higher (thus the higher top speed).
But (and it’s a big but) you probably won’t get stump pulling
acceleration out of it. That’s
where low strand count motors are strong (singles and double).
I have to stress this again - this is a very general understanding.
In years gone by, the
choices were fairly simple. The
more power you wanted, the lower the number of turns, and strands you opted for. Something like an 11 Double would have been considered to be
an enormous motor. That is no
longer true. New motor winding
technology and new battery technology has meant that motors are gradually
slipping into the 6/7/8 turn range. (and
are incredibly fast). Still,
here’s a rough guide to motors for you:
New
to Modified: When
you’re choosing a 2wd motor, steer clear of stump pulling torque.
Remember you’ve only got a small tyre contact patch
in contact with the ground. Try
to run multi-wind motors like triples, or quads and generally stay around the
11-12-13 turn range. For tighter
tracks, or higher grip, you might try a 12 double.
When you first start out, a 13 Triple or Quad will be an excellent,
consistent choice.
Club-Racer:
Once you’ve
been racing modified for a while you might like to step up your power a little.
At this point you’ll need to be driving consistently and need fairly
decent batteries. Try something in
the 9-10 turn range – probably a double or perhaps triple wind.
Pro:
Once you’ve got
your car and driving nailed, and when you’re looking for ultimate pace you can
start to think about 8 turn motors and lower.
You will have to be very smooth to make run-time, and be very switched on
with your motor preparation and maintenance. These are the motors that are winning state and national
championships. Note though that
even the best drivers will usually back down to something a little easier on
batteries and maintenance for regular club racing.
9.4
Stock Motor Tuning