Xtreme R/C Mag Issue 112 (March 2005) Words: Derek Buono
Trinity is usually at the forefront of motor technology. While most
companies are searching for a round brush, Trinity set out to prove
that it's not the shape or angle of the brushes that matter, but the
overall package. The last Trinity motor was the final entry in the
long-standing D-series nomenclature. Instead, Trinity has named its
new motor the Cobalt, and with the new name, Trinity hopes to prove
that it can compete with the best brushed motors out there. And if
our initial impressions are correct, it will.
New Features…
The Cobalt does owe a lot of its technology to the D6 motor. It still has Trinity's Flatwire technology, and basically the same can design, though in a brilliant blue finish. Those similarities aside, the Cobalt has a list of innovations that should make it the best Trinity motor ever.
Brushes in the Hood…
The brush hoods received some serious attention. The Cobalt hoods
are now keyed into the end bell so that there is less of a chance
that they will become out of alignment. Keen eyes will also note
that the brush hoods actually sit lower in the end bell than before.
Trinity explained that sometimes when the armature was centered
in the magnetic field, the P-94 brush would actually hang off of
the top of the commutator, so with the brush sitting lower this
problem is eliminated.
No Brush Wiggle…
The Cobalt has brush hoods that extend almost to the commutator.
This is to keep the brushes from wiggling inside of the hoods. The
previous design held the brush too far out and could cause some
brush wander that could result in harmful arcing and actually change
the timing of the motor. With the combination of the new keyed and
lowered design, and the hoods extending almost to the comm, the
result is brushes that stay nearly perfectly aligned all the time.
Cooler is Faster…
One of the issues addressed with the new end bell design is airflow. The Cobalt has two huge heat sinks to draw heat away from the motor. To make sure plenty of fresh air is entering the motor, two huge slots have been milled into the heat sinks and end bell to allow the rapid exchange of cool air and hot power-robbing air. If that's not enough, the heat sinks are also designed to accept an optional motor fan that will force-feed the motor fresh air under high-current conditions.
Brushes that Last?…
What is probably one of the best new features has nothing to do with the actual motor itself, and a lot more to do with the brushes. The Cobalt comes with a set of Trinity's new XXX brushes that are designed to last up to 20 runs without suffering any performance losses. They claim you can get 5-10 runs without truing the motor's commutator with little-to-no performance difference. That's pretty impressive, and is just what modified brushed motor technology needed.
Trimming Up…
The instructions include lots of tuning tips and information about the brushes. Trinity is the first to include information about cutting the commutator and the effects it will have on the motor's timing. They explain in the instructions that for every 0.001 in. removed from the comm via truing, that you must remove 0.0006 in. of the brush width. For those who aren't familiar with making that small of a cut in anything, you may want to wait a few cuts, since if you could freehand that small of a cut it would be amazing. Also, it's important not to start whittling Pinocchio out of the brushes. You should only narrow the beginning of the brush and not the entire brush to prevent the brush from becoming too narrow and wiggling in the hood. Our suggestion is take the edges off the brush at about a 45-degree angle to remove the same amount.
Dyno Testing…
We threw the Cobalt on the dyno after a short 30 seconds of break-in as recommended by Trinity. I always make several pulls to get a consistent graph, so after each run the motor was allowed to stand and cool off until it reach the ambient temperature before the process was repeated. While we love to look at graphs, they are only a representation of the motor's performance and the true testing of the Cobalt will be on the track.
Track Testing…
The more I stare and try to compare motors on the dyno, the more I itch to just get on the track with it. I strapped the Cobalt into my Losi XXXT MF2 that I've been running over the past few months at Titus Raceway. I've run several other motors in the car and have a good idea about what kind of power they produce and how many runs I get before I need to pay some attention to the motor. My plan was to run the motor as I normally would and cut the comm every 5 runs as Trinity recommended.
I drove two practice runs before qualifying and got a feel for the motor and what it could do. I haven't actually run a 12-turn in a long time so I took some time to get used to the power band, which was a little tamer than the 10-turns I've been running lately. After the first qualifier I took the motor out to inspect the brushes and found them to be in perfect condition. Since the motor was out of the car, I inspected the commutator and found that it needed to be cut, so I skimmed the surface and put the motor back together. Power was excellent, with the power coming on very strong in the mid-to-high RPM range. I liked the blue LED being visible on the endbell, it looks cool and can distract the other drivers! I kept an eye on the motor temperatures and they didn't seem abnormal at all. After the night was over, I took out the brushes and they were still the same shade of silver with no signs of being overheated whatsoever.
Conclusion…
The Cobalt represents Trinity's best electric motor to date. While the motor is really similar to the D6 in many ways, its list of improvements separates it from the pack. The brushes are probably the biggest news in the motor, since they actually last more than a run or two and provide good power throughout the life of the brush, and not just for the first couple of runs. Trinity seems to be back on top of the motor game and the Cobalt should be finding its way to the winner's circle on a regular basis. |
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