High Speed Pursuits

While I'm in love with the dragster, I felt like I needed a more general purpose RC vehicle. I wanted to keep my parts current so I decided to look for another vehicle that runs on brushless & lipo power. I think that if and when my dragster starts running consistent 100mph passes, I will probably retire the chassis and put the motor and battery in another vehicle since it would be a tragedy to let them sit on the shelf. Now this lead me to the conclusion that I need to build 2 vehicles. Why? Because 2 is more fun than 1. My next 2 victims will be a stadium truck and a pan/touring car. I chose these because they are both 2wd, and both can run on the parts I already have. So in my mind at least I'm getting a 3 for 1 deal. I also can test a variety of parts in many different setups so that anyone wanting to know how a particular combination works doesn't need to spend their time and money working out details that many people have already tried.

The Stadium Truck

In a game of chance I have acquired a Traxxas VXL Brushless Rustler. For the Naive the rustler is this: http://www.traxxas.com/products/electric/rustler3708/trx_rustler.htm . Traxxas claims that it is "The Fastest Ready-To-Race electric stadium truck you can buy." I thought it would be a good idea to hold Traxxas to their word and test out the truck.

This truck already has a brushless motor in it, the "Velineon Brushless Power System." http://www.traxxas.com/products/electric/rustler3708/images/velineon_motors_both.jpg. While this should go pretty fast, at some point the Mamba will find its way into the truck and well see if that makes a difference.

For a few magic beans I managed to get a 3s 11.1V 5000mah Lipo pack from Max Amps. Traxxas says I need a 6000mah lipo and gearing, but whatever, the 5000mah came in the RTR run kit. The kit also included a pretty cool Hyperion charger (More on this in another post) and a Lipo bag (to conceal explosions?). http://www.maxamps.com/proddetail.php?prod=VXLRTRKIT-5000-111&cat=75 . Going along with Traxxas's claim this kit portends to propell my little rustler to 70+mph. Sounds fun.

I don't have any real goals for this vehicle except to make it fun. I wanted something that I can play around this at the beach or the parking lot, yet is really fast, and this seems to be the thing. I will review the VXL truck in depth next week, so check back for an ultra boring a long post about it.

I have modified the truck already. There seems to be a glut of wheelie bars and wheelie bar accessories for this truck. This led me to the conclusion that this truck might do a wheelie with the high voltage battery that I chose for it. so on go the wheelie bars. Pictures will come soon.

Formula 1 Cars are fast.

The Touring Car I spoke of will be a Tamiya F103GT Pan/Touring car chassis. I chose this because it has direct 2wd, it is light, and it is cheap. It also has many option parts, and my components that I already have should fit right in. This chassis is made to accept regular touring car bodies and tires, so that makes it easy to complete. It does come with a little scrawny brushed motor, which will either be annihilated by my lipo pack or never used. I have not received this kit yet, but when I do ill include some build photos and the modified parts I choose for it.

My goal with the touring car is just to hit 100mph. Will my Mamba Max + Lipo combo do it? Maybe, but if not I'll get as close as I Can and switch to a more capable setup. This car still operates within my original parameters, so I don't need to change my own rules.

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.