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How to Build a Better Battery Pack
This tip was sent to us by Adam C. of New South Wells,
Australia. He shows us a really cool way to make a
professional-looking battery pack using a pair of old shock spacers as
battery spacers. Thanks for the tip Adam!
_ ____ _
| | |__3_| | |
|2| ____ |6|
|_| |__4_| |_|
Have cells 1 and 2 tagged together
as well as 5 and 6. The rest may be tagged individually to make
them easy to solder.
2. Get 2 X 4mm shock spacers from a Kyosho 1/10 scale on road, such as a
VoneS or other. You could also glue 2 X 2mm spacers etc. No idea if
other brand spacers would work but it's worth a go.
3. Cut off the top plastic part (usually used for removal from the
shock) to make a complete curve.
4. Cut off about 2-3mm from one edge. This allows it to slot
around the positive terminal on cell 2 while not interfering with the
tag and will separate the cells perfectly to sit in the precut slots of
5. Repeat this for cells 5 and 6.
6. Trim the excess from the individual tags.
Simple Inner-wheel Drum Mod
This used to be one of the most difficult modifications to
perform, and now it just became the easiest. You will only need a
pair of curved Lexan scissors (available from almost any hobby shop, or
most likely already in your pit box) and a set of HPI inner-wheel drums.
Using the Lexan scissors, begin making a cut from the edge of the wheel
drum to the center of the wheel drum. Cut in small portions all the
way around the wheel drum until you have a nice clean cut. Trim away
any excess plastic on the wheel hub and Voila! Your inner wheel
drums are perfectly cut and will now accommodate the long can of almost
any 540-sized motor.
Begin cutting from edge towards center
Continue cutting the all the way around
Finished mod should look something like
Close-up picture of modified wheel drum
Equal Offset of Rear Wheels
In order to fit a 540 motor into a Micro we had to
significantly push out the left wheel to accommodate the long motor's can.
We include in the kit a 3mm spacer which goes between the stock purple hub
and the bearing to help everything fit. NOTE:
No modification to your motor is required for normal operation of the 540
Well as it turns out there is a way to eliminate the 3mm spacer all
together and create equal offset of the wheels. Which in turn will also
sink the wheels better under most bodies. We don't know that
this works with all motors, but with the Reedy MVP it works fine.
The trick is to use the little 1mm HPI spacers that are included with each
set of inner wheel drums. Put one on the diff side and one on the driver's
side. Then as described in the instruction manual, the wheel drums must be
cut down as far as possible. However we've never really been too adamant
about how far to cut these down, as the 3mm spacer pretty takes care of
any slop in the cutting. But if you Dremel down (or use the trick
mentioned above) the wheel drum so far as to almost cut right through it,
you can create more room for the motor without having to push the hub (or
wheel drum) out any further on the axle.
You can't stop there however, next step is to Dremel the endbell of the
motor itself. Now don't get too crazy though! On the MVP, all
I needed to Dremel was a small portion of the heat sink fins and I was
able to get the motor to fit. With different motors, the amount or
grinding will vary, but in no way should you ever need to grind away more
than necessary and what is simply cosmetic.
Now when everything is installed, the spacing between the endbell and the
wheels will be about 0.5mm, which as long as they aren't touching, should
Understanding Gear Ratios and the Micro Hybrid
The Micro Hybrid's Motor Plate was designed to accommodate
any standard 48 pitch pinion from as small as 26T to just larger than 35T.
The largest pinion that most manufacturers make, including HPI and
Robinson Racing, is a 35T. At no time should there be any reason you
would want to gear the car any higher than that. So with a 10 tooth
span in gear options and about a million motors to choose from, where do
First, let's get a few phrases understood before we go into
Gear Down - To switch to a smaller pinion
Gear Up - To switch to a larger pinion
Run a Tall Gear - Run a large pinion
Overgeared - Pinion is too large
Undergeared - Pinion is too small
Low gearing - Small pinion
High Gearing - Large pinion
Low Gear Ratio - Large pinion
High Gear Ratio - Small Pinion
These phrases are used interchangeably throughout almost
any magazine or web article related to RC cars. I only mention the
pinion gear in each of theses cases because with the Micro there is no
transmission and you can't change the spur gear. So the pinion gear
is all you've got to adjust your gearing.
Every motor is different. Because every motor is
different, every motor needs to be geared accordingly in order to make it
run it at its maximum potential without exceeding its limits at the same
time. A good general rule of thumb to go by is gear up for stock
motors and gear down for modified motors. The lower-turn motor you
run, the smaller the pinion should be. That having been said, you
might not want to run a 35T pinion on a 10-turn modified motor.
The result would be not enough low end, and the motor may never completely
wind out resulting in poor top end as well. You could also damage
your motor and your cells by overgearing your motor.
By the same token, a stock 27-tun motor with a 26T pinion
would probably be undergeared. In other words, you wouldn't be
pushing the maximum performance capabilities of your motor and your setup
would suffer. You'd have too much low-end torque and not enough top end.
Pretty much the opposite of the overgeared modified motor scenario
mentioned above. It is imperative that you find the right gear ratio
for your motor and your driving style in order to get the best performance
out of your Micro Hybrid.
First rule: always start small. There is no harm or
foul in running a pinion that might be a tooth or two too small. A
27T-28T pinion is a really good place to start with any motor. Now
you bigwhig 1/10th scale guys are breaking out your calculators and doing
the math and realizing that amounts to a gear ratio of only 2.15:1!
Who in their right mind would gear any car to 2.15:1? I will tell
you...Micro owners! There are two other factors that allow such a
high gearing (compared to your average 1/10th scale car): one of them is
weight. The average weight of Micro Hybrid with all the
electronics, a 6 cell pack, and a hefty 540 motor is around 23-24 oz.
That's about half what a fully equipped TC3 weighs.
You remember any of your Physics classes from High School?
Newton taught us that F = mA where F = Force, m = mass, and A =
acceleration. If we take the same motor that pushes a TC3 and drop
it into a Micro, then we can safely say the the Force is constant, being
that the same motor provides the force and is the same in both cars.
If we flip the equation around to allow us to solve for our only unknown,
acceleration, then you get a = F/m. So what happens as the mass goes
down and the Force remains constant? The acceleration goes up!
In fact, if you halve the weight of the car, then you double the
acceleration. (Now whether or not you can get that kind of power
from the wheels to the ground in a Micro is a completely different physics
lesson :-). But the fact of the matter is that high gear ratios are
required to overcome the weight of the car. If you reduce the weight
of the car, you can safely run a taller gear, which ultimately means, more
RPM's to the wheels.
Now the other factor (which is the major one) is the tire
diameter. Anyone who is really competitive when it comes to racing
knows that as the tires wear down on your car, you need to gear up to
compensate. Otherwise as the tires wear out, you would
begin to see more low end and less top end. Well just imagine if the
wheels on your TC3 wore all the way down till they were the size of a
Micro wheel? How many teeth would you need to gear up to completely
compensate for it? 1 or 2? How about 10?
What is all boils down to is this: as far as the motor is
concerned, an 8:1 gear ratio in a 1/10th scale RC car or a 4:1 gear ratio
of a 1/12th scale car will behave a lot like a 2:1 gear ratio in a Micro
Hybrid. And it's all because of the reduced weight of the car
and the small diameter of the wheels. So try not to get hung up on
gear ratios and numbers, because they aren't directly comparable to the
normal figures everybody is used to seeing in the bigger cars. When all is
said and done, just remember: you should always gear up for stock motors
and gear down for modified motors.