Shiny Green + 63,000RPM = Fast?

Mamba Max Time

What sounds like a catchy intro for tonight’s episode of dancing with the stars (don’t ask why I know that) is actually an intro to the motor I’ve chosen for my dragster. http://www.castlecreations.com/products/mamba_max.html

The Mamba Max is a motor made by castle creations that offers brushless power & high RPM’s for a decent price. I ended up choosing the Mamba Max for 3 reasons.
The price. I snagged mine off of eBay with shipping for around $100 less than what the other packages cost. This enables me to stay within my original budget goal.
Allot of people are using them. Drag racing, off road racing, carpet racing. They all seem to agree that the Mamba line of motors is versatile enough for all of these applications.
The RPM rating makes it a capable candidate for my 100mph project. Also it will fit in a touring car or a truck, so it enables me to try to reach 100mph in a variety of platforms.

For my application I chose the model that will spin at 5700 RPM per volt. They do make a Mamba Max 6600, and a Mamba Max 7700, but those are limited to 2s lipo packs. They are limited to prevent mechanical failure so a quick estimate of the math shows:

7700RPM x 7.4V (2s Lipo) = 56,980
6600RPM x 7.4V (2s Lipo) = 48,840
5700RPM x 11.1V (3s Lipo) = 63,270 RPMs!!!

Here is s nice link castle puts out that shows the capabilities of their products. (Ignore the speed results that they have since those are with different gearing & weight than what I will use.) http://www.castlecreations.com/support/documents/speed_and_gearing_chart.pdf

Did I forget to mention that I will be using lipo packs for this project? Ah yes, the new “black gold” of electric power, lipo (lithium polymer) batteries offer more voltage at a higher discharge rate for a longer period of time than similar Nickel Cadmium batteries. The problem? Lipos can catch on fire if they get too hot, too low in charge, or too much of just about anything. So you must have a specific charger, and other equipment to properly charge the batteries. This sounds like a big deal, but there has been a ton of literature written on the subject, and it seems straightforward. I haven’t used the lipos yet, but Ill post any explosive results I get with these little powerhouses. I ordered My LiPo’s from Max Amps. I’ll do a full review when I’ve used them in multiple vehicles.
http://www.maxamps.com/index.php

Back to the motor
So as you can see from my calculations the Mamba Max 5700 has a higher RPM rating when being used with the recommended batteries. In order to stay within my rules of being able to operate the car after the run, I decided doing what the manufacturer says to do would be best. Now if I break the 100mph barrier and decide to test the limits, you can bet I will strap one of the 7700 Mamba Max’s to my dragster and see what happens.

Powerplant Wanted

Now that the chassis is assembled I need to find a motor that will push it over 100mph. Electric motors have come a long way in a short period of time, and that makes my project significantly easier.

I am by no means an expert in RC or motors, but I will try to provide a brief description of what I have found out (please feel free to add to this in the comments if you feel compelled to do so).

For a long time the remote controlled car was powered by the brushed motor, this motor offered speed and affordability, but the performance could not meet that of a nitro motor. Also the brushed motor has miniature brushes that need to be replaced periodically that adds to cost and downtime. The brushed motor kept RC cars stuck at a certain ceiling of performance and durability for a long time. I think it should be noted that there have been several 100mph passes made with brushed motors in the past, so the limits on performance are not absolute, but 100mph runs were defiantly the exceptions.

Along came the brushless motor into model aircraft. This motor offers durability and high performance that could compare with some nitro engines. The brushless motors are essentially turned inside out so that the magnets rotate inside of the motor, instead of the fixed magnets in a brushed motor. This configuration allows the car builder to forgo the necessary rebuilds, and set the limits higher that previously restricted electric motor performance.

This wikipedia article sums it better than I can so you can get the idea
http://en.wikipedia.org/wiki/Brushless_DC_electric_motor

I think Its easy to see why I chose a brushless motor for my car project. In my search for the perfect powerplant I considered 3 different brushless motors and electronic speed controller combinations.


Neu motors – These are model airplane engines. They come in a wide range of RPMs, shapes, and electrical parameters. The current RC world record holder of 134mph used a Neu motor for his car. The drawback in one of these is the cost, and the fact that they don’t come matched to an ESC. In fact the cost of the engine alone is more than many of the motor + ESC combinations that I’m considering for this project. http://www.neumotors.com/20061222/Welcome.html


Novak Motors – Novak offers a High Voltage brushless motor and ESC combination. This would allow me to run several LiPo(See future article) batteries, so generate sustained RPMs that are needed to run at high speeds. The motor and ESC combination is cheaper than the NEU motor, but seems to have less performance capabilities also. This is still an expensive combination, and seems limited in its capabilities. At the World speed record challenge there was a car that used this setup to make several 100mph passes. http://www.teamnovak.com/products/brushless/hv4.5_system/index.html


Castle Creations – The mamba line from Castle creations seems to be very popular among the drag racing crowd, so it immediately grabbed my attention. The recent release of the 1/10 Mamba Max seems to be very popular right now. These motors are capable of the ~60,000rpms that are needed to go over 100mph. They also come packaged with an ESC that is programmable from a laptop. This means that you can adjust different parameters that control aspects of the motors performance from your laptop. The best feature of this motor is the price. Of the 3 I reviewed it has the lowest price tag, and the ceiling of performance is yet to be determined. http://www.castlecreations.com/products/mamba_max.html


I think that any of the 3 above motors will propel my dragster to the desired speed. Check back later this weekend and ill photos of the winning combination.