Aktion RC is proud to present the all-new x3 Series 540 Micro RS4 Conversion Kits.  All the power, all the speed, all the fun - times three.


Have a tip to share?  Send it to us at support@aktionrc.com and we'll include it here on our web site.

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!

 _         _
| |        | |
|1|        |5|
|_|        |_|
 _   ____   _
| | |__3_| | |
|2|  ____  |6|
|_| |__4_| |_|

1. 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 the chassis.
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 the drum

Finished mod should look something like this

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 Conversion Chassis.

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 be plenty.

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 you start?

First, let's get a few phrases understood before we go into explaining anything.

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.




Accessories shown in pictures sold separately.  The Micro RS4 is a registered trademark of HPI Racing. 
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