What can you do to improve speed and run time...
Nov 07, 2006
 

I've done it. The motor was tested on the 11th of February with mixed results.

The session didn't last long because of radio problems that I could not identify at the track. It could be just interference or just because some people turned their radios without any regard for the other drivers. My frequency was just 5Khz away from 3 other drivers and they happily turned their radios on on the pit whenever they wanted.

Trying to find a radio problem in this scenario is near to impossible so I had to stop the testing session.

However I still got some impressions of the motor and controller.

I mounted it on my HPI Pro2 (now I'm glad I did because of its capacity to withstand punishment). The motor fits perfectly, screwed to the mounting plate, and only the controller needed a little more thinking.

The Controller is a little big compared with the ESC that we are now used to, and the space on the Pro2 is really small for any of them. The Tekin G10 and the Novak Cyclone TC were my choices until now.

After some trial and error I decided to mount the controller on top of the transponder mound securely strapped. This guarantees a very secure way of having the controller, but the weight is on the upper part of the chassis. A purist would say that it affects handling (and he's probably right), but there aren't more choices in this chassis.

The power wires are too short and they don't reach the battery poles, so I had to do a couple of extensions to connect it to the battery. The wires to the motor have the perfect size and a re well within the limits of the chassis.

I use Corally plugs (I'm using them because I like the idea of being able to use the batteries and motors in all my cars without the need of a soldering iron). There may some voltage drop but I guess that the goal here is to test the motor and not be distracted with marginal problems.

With all the voltage drops and resistance, this motor is still a lot faster than the best brushed motor that I have.

On the safe side I chose to start with a very small pinion (19/115) and this was probably the reason why I just didn't destroy the car on the first run.

The acceleration was amazing, but the car was lacking some top speed. We are talking about  a Final Ratio of 13.0, a Spur/pinion ratio of 6.05 and a Roll Out (mm) of 15.21. This is a very conservative ratio. Imagine 13 revolutions of the motor for each on the wheels.  Almost half of what we can have with a 9T.

It was with this ratio that the first crash happened. And what a big crash it was. In the middle of acceleration a radio interference caused the car to turn left and reach top speed before hitting the corrector. Then, already in flight, hit a small separator with 4-5 inches high and it went to the air with incredible ease. The flight was 6 or 7 meters long. Only the steering ball cup was loose. A friend snapped it right in again and the car was running again.

This is the best thing I have to say about the durability of the Pro 2. The car is a tank.

The car felt very good with the power reserve that the motor has. At any time you just hit the throttle and there he goes, even with a very high ratio.

It was time for going up a little bit. I installed a 22 pinion. The top speed increased a little but the motor seemed to be able to withstand much more.

The brakes are very powerful. you can go at full speed and stop the car completely with just a touch of brake. This happened to me many times. I stopped the car completely a few times and after that the motor takes one or two seconds to resume rotation. I fell in that error several times. Then I adjusted the EXP brake to -100%. It still is very strong.

The other thing that you notice immediately is the way the car keeps going when you let the throttle go. It goes forever. I never had a car with one ways (I only tested my Yokomo after this) but I concluded after that the car freewheels more than a car with center and front one ways with a normal brushed motor.

Time to change pinion to a bolder 32. Now we are talking about a Roll Out (mm) of 25.62, and this is much higher than the first test. The acceleration didn't suffer too much. The time it takes this motor to spin to max RPM is very very short, even under load. It's where the power comes to play.

The thing is a rocket. And the brake is like a wall. It stops it in no time.

When I was starting to have fun and compare the speed with 1/10 on road cars, the radio problems increased to a point where the car would gain it's own life and do whatever it wanted. Things like doing complete circles on the track or just go to the barriers on a 180º curve happened again and again.

To make things worse there are guys that think that a 5Khz margin between frequencies is perfectly OK for switching the transmitter on. And they do it. I got so mad with the attitude that I decided to return home and assess the damages. My beautiful Stratus body took a beating. It's very scuffed on the front and sides.

The batteries lasted for the entire session. They a were a pack of 2000 matched and the sum of all the tests was about 10 to 12 minutes. When I returned home the pack still had some juice to deliver. In a race situation I guess that 10 minutes is a reasonable time to expect from batteries like this. This time is very good, even when compared with nitro cars.

First impressions

This motor is not for the rookie (it may even be a little over the top for me). It requires some adaptation of the way we drive. A sudden punch of throttle may send the car to the sky. The freewheeling is something that we need to get used to and use to our advantage, and the brakes are the most powerful thing that I've seen. I'm used to brakes in nitro cars with a lot of initial stopping power, but this is ludicrous.

If you are used to soft brakes (like the Novaks have) this may the biggest surprise of all.

I give it 4 stars. The fifth star will be reserved for the day when I'm able to race an entire 5 minute run against a 9T or 8T on a TC well tuned and well driven.

The small test showed that I can leave that car behind in a hurry. I'm glad the way I spent my money.

Another small test session

Today (15/02/2001) after sorting out all the radio glitches I conducted a range test with the car just to see if it would be safe to drive such an incredible machine on a track.

I installed a pack of non matched Panasonic 3000 batteries and made a few runs with a duration of 6 or 7 minutes. The batteries, I thought, could give some minutes more, but how much?

So I decided to go to the garage of my building (don't fear, its big) where I could stretch it a little more. There is a distance of more than 40 meters from where to run the car in straight line. And I did.

I could also simulate curves where brake has to be applied and I can do a circuit (an H) where turning and accelerating it's always happening. In between I would go at full blast for 40 meters in a surface that has not the best grip of all.

What I found is that the car can accelerate to full speed (and believe me it's not for a person with a weak heart) in less than 4 meters. The car has a ratio of 32/155 installed and this is below the ratio I use with 10T motors. With a normal motor braking after each drag run could be a problem, but even with the exponential at -100% the car stops. I did this for what it seemed like an eternity, and I had started my stopwatch.

So I played and played and played. The turns were mad, kind of like what the Rally drivers do. A little bit to one side to put the car sideways and then to the other at full throttle. It was amazing. I've mastered the technique of not letting the motor go to 0 rpm, so that the acceleration can be done smoothly and in an instant.

And there I was playing like a kid under the eyes of some of my neighbors that arrived after a day of  work to see a guy (that should have been wiser) running a toy car in the huge garage.

It lasted for 18 minutes and I'm not counting the first 6 or 7 and the energy that I spent doing the range check with the car on the stand. I must have played for more than 25 minutes.

I'm going to blow away the guys at the track. I can even let them go just to catch them (that's what I like to do with my 1/12) because it gives you a more precise view of what the difference is.

In one second the car was in front of me and the next second it was at the end of the straight. A small bump with no more than 1 cm (ramp) would launch the car into the air like if it was a TT track. This thing is awesome.

At the end the batteries were barely warm, the motor was at a temperature of 42º (I measured with my Raytek probe) and the ESC was barely warm also. At that speed the batteries and a normal motor take a huge beating. I've measured my deceased D4 at 85º Celsius.

What more can I say? I just hope that the next day at the track is not plagued by radio problems. Oh boy it's going to be fun.