Which motor,esc, and battery for vac-u-cracker

[yellafishdog]

After a visit to vac-u-boat's website, I decided to buy the crackerbox kit and all the hardware rather than try and build my first boat. I am ordering from the website tomorrow. I have just a couple of newbee type questions about motor's and ESC and batteries

1. I am looking at stock 540 motors. What does the number of "Turns" mean when refering to a motor? and how does that relate to performance?
2. When choosing an ESC, how do I make sure it is compatible with the motor?
3. What do I look for when trying to select batteries for the above?

Thanks, any input is appreciated, Jeff

[Doc]

Jeff,
The number of turns refers to the number or windings on the motor. Usually, the less number of turns the faster the motor will turn (more rpm). That's great, but only knowing the number of turns in a motor just doesn't tell you anything useful. Less turns mean less resistance to the electrical circuit, which means more current draw, which means less run time for the 'same' size of battery compared to a greater number of turns per motor. In short, faster but shorter.
When choosing an ESC you should be aware of the ESC's ratings for current and voltage. Any particular ESC will handle only so many amps at a particular voltage. The higher the amperage rating the better, sort of. It should also handle the amount of voltage applied to it (otherwise it turns to ashes). So, in a nut shell, you should know what the maximum current draw of your motor(s) is. You find that out by doing a 'stall' test. Feed the motor current and measure it while you hold the drive shaft still (like a locked up motor). Whatever that 'stall' current is should be capable of being handled by the ESC (otherwise it burns up, right?). Read the specs of the ESC. Select the one that has the features you want (forward?reverse) and that can handle what you will put it through.
Batteries. The bigger the mAh rating the better, till it becomes too big for the boat. Naturally you have to keep the voltage in mind. No point in feeding a motor 24 volts when it can only handle 6 volts (or whatever). You can 'over-volt' most motors but it does depend on how much the motor can stand, and for how long. No easy way to know that, mostly just by 'reading' the ashes, sort of.
Wanna 'push' the limits a little? Great, but don't expect miracles!
Hope that helps...
- 'Doc

[yellafishdog]

Doc-

Thanks alot, that does help quite a bit. Guess I will just have to continue reading , but at least now I have some idea what to look for...never knew there how involved this could get!

[CG Bob]

Get a ROAR (http://www.roarracing.com/) stock 540 motor, 6 cell 7.2V battery pack, and an ESC. Electric Crackerboxes are raced in many areas, and those are the standard "stock" requirements. A ROAR stock motor (http://www.roarracing.com/downloads/2006rulebook.pdf) has 27 turns.

Here are the International Model Power Boating Association (IMPBA (http://www.impba.net/)) Crackerbox class rules. The North American Model Boating Association (NAMBA (http://www.namba.com/content/default.asp)) has similar rules.

1/10 Scale Crackerbox
General
A Crackerbox is a Specialized N-1 MONO class not offered for records. The Purpose of the 1/10
scale racing Crackerbox class is to race a scale model of the APBA Crackerbox, one design,
runabout.
Hull Classification
The basic hull lines of the 1/10 scale Racing Crackerbox must be taken from the drawings of APBA,
an approved source. All commercially manufactured hulls that meet these specifications are legal.
To qualify for 1/10 scale Crackerbox competition, hulls must be within + or - 1/8" of approved lines.
The deck/hatch must resemble the deck of a full scale racing Crackerbox.
The boat must be painted or finished in the spirit of racing a scale model.
Each boat will have racing numbers preceded by the letter P.
Two drivers of scale-like appearance must be used in the driver/rider compartment. The driver and
rider must have orange colored helmets and life jackets.
The dead rise at the transom shall be 3/8" in total (3/16" per side) with a transom width of 6-3/8"
Motor/Battery Specifications
Any single 05 motor with "ROAR" and year stamped on the end of the can from the factory. Roar
motors cannot be opened or end bell must not be removed. Paradox template 27 turn motors are also
allowed. It is OK to change brushes and springs.
Drive motor batteries must conform to Sub C specifications and be a standard 6-cell pack.
Drive Train.
1. A single motor shall be coupled directly to a straight drive shaft. A flex shaft may be
used in a straight tube.
2. The propeller may not extend beyond the back edge of the transom.
3. Steering shall be by a rudder mounted under the hull or affixed to the transom.

[n.h.schmidt]

Hi
The part in the rules about the end bell can't be removed or the motor opened.that no longer valid.All roar stock motors are now rebuildable and can be easily opened. If you are going to be useing a Roar stock motor ,I can recomend a couple. The Trinty P2K or P2k2 are ideal on a crackerbox. They can lug down better than most of the other Roar stock motors. I have seen a lot of other stock motors burn up in crackerbox raceing. If you have your typical old clunk 540 or 550 motor laying arround ,you can use anything like that too. They will likely be slower though.
A well setup cracker box can do about 20mph with low cost stock motors and esc's . Any regular size car controller will work. A Duratrax Streak works great and is cheap from Tower. A cheap Octura X431 prop is competive . n.h.schmidt