Modified electric racing has always taken a back seat to the stock class in participation nationwide. However, the modified class has consistently attracted the world's best driving talent at the most prestigious racing events.

Trinity, which has pioneered many of the innovations seen in electric motors, fired the latest shot in the power wars of modified racing with the introduction of the D4 Copper Head motor. This motor represents the latest in high-performance technology from Trinity and features a host of innovations.

Can. The D4's shell is a 1.4mm can with a black crinkle finish. According to Trinity, this coating is supposed to provide better heat dissipation. The can doesn't have large vents around its circumference or on its mounting surface. Trinity claims that large vent holes compromise the integrity of the magnetic field and result in a subtle loss of efficiency and torque production. It's what's inside the can, however, that is one of the D4's truly unique features. For the first time ever, the industry has a modified motor with removable magnets. Trinity devised a clever system of stops indented in one side of the can and a slide-in clip on the other to secure the magnets. The obvious advantage is that the magnets can be replaced when they begin to lose their strength; there's no expense of buying a new can or even an entire motor.

Trinity also parlayed this feature into another innovation based on a lesson learned years ago in manufacturing slot-car motors—matched magnets. Trinity matches the magnets that go into every D4. Using a gauss meter to measure the magnetic strength of each one before it's placed in the can, Trinity pairs magnets of similar strength. All other motors, including Trinity's previous D3.5, have the magnets epoxied into place at the factory. If the magnets are of different strengths, Trinity claims it creates a condition in which the magnets "fight" each other—something like trying to race a horse with stubby front legs. The process of matching the magnets, irrespective of relative strength, keeps the magnets "in phase" with one another, and improves overall performance.

Armature. Trinity uses two armatures in the D4, depending on the number of winds. Motors above 12 turns use a thin-web armature; motors in the 12-turn and fewer range take advantage of a beefier armature with a thicker web. Some winds use armatures of both styles, but 12 turns are usually the benchmark.

Left: It's what's inside the can that is one of the D4's truly unique features. For the first time ever, the industry has a modified motor with removable magnets. Right: The armature with the groove on the crown (left) features a thick web for motors with 12 turns or less. The thin-web version (right) is for motors with more than 12 turns. Using different armatures is claimed to provide better wire-to-metal ratios and make power delivery more consistent across a variety of winds.

The purpose is to balance the wire-to-metal ratio of the assembled armature. According to technology that's way above me, there is supposed to be an ideal ratio of wire-to-armature mass to maximize performance. According to this principle, using a single armature for a wide variety of configurations isn't ideal. If an armature is best suited to a 13-turn setup, using the same armature with more turns (15 or 16, for example) would result in good torque output but in a disproportionate loss of rpm.

The opposite is true of motors that have fewer turns. Nine-turn motors, for example, would be able to produce very high rpm but would fall short in the torque department. Yet another available option related to the armature has to do with the wind configuration rather than the stacks. Trinity also offers what's called a High-Variance (HV) Split Double wind that uses one strand of thick wire and one strand of thin. This is supposed to reduce inductance and make throttle response a little more crisp for high-traction applications like touring cars and 4WD buggies. I unfortunately didn't get a chance to test one of the HV motors because they were not available during testing.

Endbell. The endbell is where the D4 gets its "Copper Head" trademark. Affixed to the endbell are pure copper heat sinks and brush hoods. The purpose of using copper hardware is to take advantage of the reduced resistance copper offers and get more power through the brushes to the armature. Copper is soft, so it's more susceptible to breakage if bent back and forth, but Trinity is already working on an update for the brush hoods/solder tabs to make them as durable as possible.

Left: The D4 has pure copper heat sinks and brush hoods. Copper is an excellent conductor, so it allows more power to get through to the motor. The design of the soldering tabs is being changed to prevent the softer copper from breaking if it's bent too much. Right: The built-in surface-mounted capacitors are visible when the brush hood is removed. The D4 motors have three capacitors—the number recommended by most radio and speed-control manufacturers.

The brush hoods are affixed to the endbell using a standard spring post on one side and an Allen-head screw and blue-anodized aluminum heat sink on the other. Brush vibration dampers are also installed in the top of both brush hoods.

Trinity has also installed surface-mount capacitors in the endbell, thus eliminating the need to solder capacitors on the motor prior to installing it. This technology was first seen in Orion's chrome modified motors, but Trinity one-upped it by including a third capacitor.

Left: Each motor has a label that shows its dyno-test data. Although the label data is relatively consistent from one motor to the next, the tests conducted for this article showed considerably better numbers. On our dyno, this motor produced: 42,328rpm; 233.9 watts of power; 79.5 percent efficiency; 248.3 Nmm torque. Right: The magnet clip slides between the two magnets to hold them firmly in place. Once the endbell has been installed, the locking ring prevents the magnet clip from working its way out of the can.

My point is, you can count on these motors performing better than indicated by their label. It isn't a bad thing—just helpful to know that motor performance easily exceeds the label's claims.

It's worth noting that removable magnets introduce the issue of maintenance to modified racers. Whenever magnets are removed and installed, it's critical that the inside of the motor can and the magnet's outer surface be clean and completely free of debris. The tight tolerances between the magnets and armature are such that even the smallest piece trapped between them will cause interference. The armature will probably come into contact with the magnets, and that can introduce a host of other problems. Just be aware that you need to take extra care in this area when you're doing maintenance jobs.

The magnet issue brought an oversight to my attention. Replaceable magnets are new for many of us, including me. As I attempted to remove them for inspection, I realized they are pretty tough to dislodge, even with the magnet clip removed. I ended up jolting the can with the palm of my hand in an attempt to dislodge the magnets from the side of the can. This proved to be the wrong move, as I chipped a corner of both magnets. After installing a new pair of magnets, I quickly found the best method of removal is to slide the magnets away from the indents in the can that hold them in place. As it turns out, the indents still maintain a firm grip on the magnets even after the magnet clip has been removed. By sliding the magnets away from the indents, you make it much easier to pry the magnets away from the can with your finger so you can remove them. Just be careful not to slide the magnets too far around the can. The magnets are extremely strong and can be tough to separate if they come into contact with each other. When installing them, it's important to note that the magnet that's white along its top edge with a red dot is the positive one. Be sure to line up the positive side of the endbell (timing adjustment notwithstanding) with the positive magnet. Getting back to my original point: the oversight is that magnet removal and installation procedures aren't outlined in the instructions.

FINAL ANALYSIS
The Trinity D4 series offers a measurable improvement over any of the company's past offerings. The combination of the new can, armatures and endbell and the option of standard or HV winds offer racers more application-specific mills than ever before. The can's modular design and replaceable matched magnets also score points for those of us who watch our wallet. It simply costs less to maintain a strong level of performance with the D4.