ASK Cub Reporter- 03.14.2011- Sit Down, Shut Up and Learn Noth’n

G’day,

Ive recently bought the Thundertiger Sparrowhawk XXT, and I’ve noticed that you guys have done a review on it. Also I’m using it for a research project, looking at what i can do to eek out as much power from the car as I can. I’m thinking battery wise, but also is there anything you can do to modify the motor without swapping it out?

Regards Liam

Cubby- G’day to you too mate, what’s up down under? Is your water still spinning the wrong direction in the loo?
So…. you want to extract maximum power from the brushless motor that came with your TT SparrowHawk. What are your options?
Well… you can never make a 300 watt motor into a 500 watt motor, but you can do a few things to ensure you are getting max power from your motor.

1. Use a good battery. A motor can’t put out max power if it can’t consumer enough energy to meet its thirst. Let’s say your motor is good for 300 watts at full tilt. It’s obvious you’ll need a battery that can put out more than 300 watts (to allow for energy losses). In the case of a 2S pack you’d like to see it maintain 3.5 volts per cell on a 45 amp load (315 watts). If a pack dips to lets say 3 volts per cell at 45 amps (270 watts) your brushless system won’t be putting out all the power it’s capable of.

2. Keep the bearings in your BL motor spinning nice and smooth. If the bearings are dirty or worn out your motor will be wasting power turning those bearings over, power that it could be using to blow your tires off the rims. Btw, what might feel like a small amount of bearing resistance spinning the rotor at 10 rpm with your hand can turn out to be a lot of resistance at 40,000 rpm when your motor is screaming down the bad straightaway.

3. Use good connectors, or skip’em and simply direct solder. If you are looking for maximum output, you want maximum voltage to make it to your motor. A bad connector (or solder joint) costs you voltage, plain and simple. Let’s say you use a junk connector between your battery and speedo and it costs you half a volt. Doesn’t sound like much does it? But lets look at the math… Let’s say your battery puts out 7 volts on a 45 amp load using a good connector or direct soldering, that’s 315 watts available to your BL system. But… if you use a crap connector and it only puts out 6.5 volts at 45 amps that’s only 292 watts. Your motor can’t put out power that isn’t available to it in the first place. Good connectors can not make a slow motor fast, but they can help make sure it puts out all the power its capable of.

Lastly… if you I were you Liam, I’d pop a 3S pack in your ThunderTiger and gear it appropriately. What is the correct gearing? Well that’s completely up to you, but you should use GearChart.com to get in the ballpark. If you are looking to go 60 mph then gear it for 65, not for 35, and certainly not for 265.

Cub Reporter,

I have recently been looking to buy a Traxxas slash. My friend will sell me his used slash for $100 but I have been thinking about just buying a new one. This would not be my first truck as I am getting back into the hobby after being gone for 5 years, what do you think is best for me?
Christopher

Cubby– Hey now Chris, thanks for the email.

Hummm… tough question, but easy answer- it’s your cash, do what ya want. Some guys like saving some cash and buying used, others don’t want to take the risk of a used truck being a pile. What kind of person are you?

If it were me, this is what I’d do. If the used truck was coming from a friend of mine, to me that’s a huge plus. It means I know his cell number and can melt down on him if the truck has issues, much better than just buying an anonymous truck off a site like E-pay. And, Slash 2wd’s are pretty simply trucks, when you look at one it’s going to be pretty easy to see if it was well taken care of or if someone purposely hucked it off their roof every day (hehehehe!). So in your case, if your friends used truck looks to have been well taken care of and works properly, I’d save the cash and buy used. If it looks abused, hit your LHS and pick up a nice new shiny Slash. Whatever you decide, have fun with it, drive it like you stole it, and shoot me pics!

That’s it! Shoot me your questions, love letters, death threats and amputated body parts to Cubby at BigSquidRC dot com!

YOUR Cub Reporter