ASK Cub Reporter, 08.30.2012, Version: Your Letters, My Drivel

Hi Cubby,
I am pondering the question should I buy a new Traxxas Stampede or not. All I do is parking lot plus the dirt hills behind my house. Is there a better option? Help.
Jose L.

Cubby- Que pasa Jose? Thanks for shoot’n in an email.

Ya know… Traxxas has sold an awful lot of those Stampedes, and I can say from first hand experience that they are a good truck. However…. is there a better option out there? We get a lot of emails like this one, and that’s the exact reason we did our way-super-uber 2wd Monster Truck Shootout. We took the Stampede and put it head to head against its primary competition- the ECX Ruckus and the ARRMA Granite, just to see which one is the overall basher. We’ll be posting the results of our shootout on our front page Tuesday, September 4th. Hopefully our shootout will help you make an informed buying decision.

Hey Guys, I read your review of the Dominus being a noob I went an got one an have been bashing it since. I would like to upgrade the motor to a brushless, would you be willing to tell me which ones would fit? I know you’re busy but I figured the fastest and easiest thing to do would be to ask a pro!
Thanks for your time.
Luke D.

Cubby- Hey now Luke, be sure and shoot Brian your snail mail so we can send ya some free BigSquidRC stickers.

So…. what brushless motors fit the Helion Dominus 4wd SCT? Pretty much all 540 and 550 brushless motors will bolt up without issue (you’ll want a 550). I don’t know how much of a noob your are, but just fyi, the stock speedo isn’t designed to run a brushless motor, so you’ll need a brushless speedo to boot. Oh and, the stock battery that came with the Helion is less than optimal for use on a high powered brushless system, so you’ll want to look into better batteries as well. And really, really lastly… we did a hop-up article on how to install a brushless system in the Dominus, HERE is the link.

Cubby what difference does a 5000 mah 7.4v Lipo make to a 5000 mah 11.1v Lipo if they are both 35C?
Kevin W.

Cubby- Hey Kevin, thanks for taking the time to shoot me an email.

There is a big difference between a 2S 35C 5000 and a 3S 35C 5000.

Let’s say you have a brushless system capable of 400 watts in your truck. For it to put out its full 400 watts it has to draw more than that from your battery (because your speedo/wires/connectors are not 100% efficient), lets say it draws 500 watts.

Lipo cells under heavy load are going to dip down in voltage substantially, lets say down to 3.5 volts per cell for the purposes of demonstration here. Your 2S pack under heavy load might only put out 7 volts, the 3S pack only 10.5. For the 2S pack to provide the 500 watts your brushless system is asking for, your brushless system will need to draw over 71 amps from the 2S pack, on the 3S pack it only needs to draw 47 amps. To boil it down- a 3S pack is capable of a third more power delivery to your brushless system than a comparable 2S pack can, thus allowing your brushless system to put out more power.

If you aren’t looking for shear power output, a 3S Lipo can provide longer run-times than a 2S of equal capacity and “C” rating. The 3S pack carries a third more stored energy on board than a 2S pack. That third more energy can be used to provide greater power as shown above, or via gearing, it can be used for greater run-times. For example, if you gear your truck for 30 mph on a 2S 35C 5000, you might get 10 minutes of runtime. If you gear the exact same truck for the same 30 mph with a 3S 35C 5000 pack, you should get 15 minutes.

But like everything else in the world, 3S does have its downsides. A 3S pack costs a third more, has a third more weight, and cheap chargers might not be able to charge them at a reasonably fast rate.

That’s it for this week amigo’s, submit your questions, answers, and whatever else you have bouncing around in those minds of yours to Cubby at BigSquidRC dot com! If your question makes the front page you get free stickers, if I proclaim yours as letter of the month you get a free t-shirt, so send’em in!

YOUR Cub Reporter