Project Update I

Sorry for the delay, lots of things have been happening and its been tough to slow down long enough to write.

When we posted the original article, we were in the final phase of component selection. Batteries were in hand ( a pair of 7.4 volt / 4000 mAh with plans to wire in series for 14.8 volts), we had plans to implement our racing phase with an NEU motor but due to cost and time constraints we went with a Fiegao so we could get our testing platform on the track sooner. We expect the 4 pole NEU to be more efficent for battery life, run cooler, with more power than the 2 pole Fiegao. Stay tuned for this summer's racing on that part of the program.

The remaining component selection decision was which ESC to go with. When we found out the hi voltage cut out on the Traxxas VXL was around 12.5 volts it more or less became a done deal, no VXL, as it just wouldn't perform under the higher power we wanted - so we bought a CC Mamba Max. While the MM is rated to handle up to a 3 cell LIPO, its also known to actually handle 4 cell and even 5 or 6 cell LIPO voltages. There is the added (crucial) benefit of being able to program in custom throttle curve and breaking profiles, as well as LIPO cut outs.

( Editors note, maybe higher voltage at lower amps is less heat stress on motor / electronics? )

Once we were committed to battery / motor / ESC - the next thing was to pick up the steering servo (we went with a $30 Futaba high torque metal gear servo with ideas to buy a more expensive higher performance servo if needed for racing), we selected the Castle Creations BEC to run the receiver and servo and one cooling fan, picked up a couple of cooling fans from various sources and ended up running one fan (Integy) off the BEC to cool the bottom of the ESC (by drilling holes in the case) and a small Radio Shack 12 volt fan running directly off the battery to cool the top of the ESC (by blowing directly across the heat sink).

We went with an www.rc-monster.com heat sink / support bracket borrowed from a friend at the track to support the (known weak endbell) Fiegao motor, we still need / want to figure out a better cooling setup for the motor, design a fan mounting for a follow up.

We then had to actually figure out the precise wiring harness arrangement. As it turns out the way we mounted the ESC, receiver, BEC and connectors all to a custom made top plate running between the center diff to the rear bulkhead - it all ended up being a modular type arrangement so we could easily lift the entire assemblage away for service to the drive train. (See spur / pinion gear discussion).

We also went with bullet connectors for the (3) motor leads, and Dean's for the battery Y-harness and associated connections to the ESC (all this leaves us with a non-solder setup for quick turn around service and repairs on race day).

Up till the wee hours, we finally called it quits with a few remaining loose ends to deal with the next morning prior to practice / racing.

Up again a few short hours later, first thing in the AM after arriving at the track we charged our batteries, finished with last minute wiring and component connections, and powered up the rig.

No smoke. WHHHOHOHOHOHHO

We made our motor installation wiht a 12 tooth pinion mated to a 46 tooth Kyosho plastic spur.

First thing out on the test track we picked up a small stone and ripped ONE gear out of the spur by the roots.

Craptastic.

2nd time out on the track for testing, our pinion came loose and scored the motor shaft and pinion bore. We were able to clean the burry off the motor shaft and with a borrowed 11 tooth pinion we were back in action (we were unable to quickly clean out the bore of our 12 tooth pinion and had no backup).

We completed the first (5 minute) heat race, finishing with a respectable time / lap count - but more than anything SUCCESS with finishing the race - BOTH with a brand new rig, and with a driver who was driving it for the first time under race performance conditions. WAY TO GO.

2nd heat race, we stripped out the spur gear and didn't finish. 3rd heat race, came close to finishing, but again stripped out the spur gear and didn't finish.

Close inspection revealed we were having trouble getting close enough to the spur on our gear mesh adjustment due to our motor bumping into the chassis center brace. Apparently the difference between and 11 and 12 tooth pinion diameter was enough to obstruct our freedom of movement for motor / gear mesh adjustment.

To solve the problem we figured out a way to clean out the bore of the 12 tooth pinion and put it back in and were re-assembled in time for the main race.

Not only did we finish, but we completed the race with good time and on the lead lap with the rest of the pack (except the winner who got the extra time around for an 11th lap). OUTSTANDING.

I would love to take pictures, but the digital camera has gone missing and still not ready, however I do have a couple of blurry pics from race day via the camera-phone.

(I know, clear as mud):






Race results for those folks who want to see how performance under race conditions pan out:

http://www.rcproductdesigns.com/docu...%202-16-08.htm