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Trinity Paradox rebuildable stock motor

Trinity Paradox rebuildable stock motor

Pond, Steve

Trinity* is well-known for its motor-design innovations and the controversy that usually accompanies them. The company’s latest release-the Paradox stock motor-screams of both because its end bell is removable, and it’s the first stock motor that’s built to ROAR specifications but can be dismantled for maintenance. The controversy? Current ROAR rules don’t permit stock motors to have a removable endbell. Kind of makes the “Paradox” name pretty appropriate, don’t ya think ….


Ine Paradox design is based on Trinity’s Midnight 2 ROAR-legal stock motor. According to Trinity, the Midnight 2 was originally designed to have a removable endbell, but design complexities compelled Trinity to release the Midnight 2 with a fixed endbell. The primary difference between the two is that the Paradox has a locking ring in the can. This ring is similar to a modified-motor timing ring, and it’s what allows the endbell to be removed from the can

The Paradox can features flat sides and the latest wet-press magnets. The can’s flat sides make it virtually impossible to rotate the endbell to increase timing and improve performance. A notch in the can that’s indexed to the endbell further ensures that the timing can’t be altered (it’s set at 24 degrees to comply with current ROAR stock-motor rules). The can also features vents designed primarily to keep the motor cool. They also act as “windows” that inspectors can look through to verify that the proper armature is being used.

The Paradox and Midnight 2 endbells are similar but not interchangeable because the Paradox endbell is shorter to accommodate the locking ring, and it has been reconfigured to place both brush springs on the same side of the endbell. This makes the springs more accessible while the motor is in a car and offers a minute improvement in conductivity when both speed-control wires are soldered to the tabs on the same side of the endbell.

One of the brush springs is coiled in reverse, so if you ever have to replace them, you’ll need a special, non-standard spring. This won’t be a problem as long as hobby shops stock them, and they’ll be available when the motor is released. Starting with the release of the Paradox, all of Trinity’s brush springs (including those for the Paradox) will use the psuedostandard color coding. Instead of the old gold, silver and black that we are used to seeing, Trinity will use the blues, reds, purples, etc., that other brush manufacturers are already using.

The Paradox armature is the same as the Midnight 2’s. It’s a double-rotor design that is wrapped with 27 turns of 22-gauge wireagain in accordance with ROAR rules. The armature’s unique characteristics are its special shaft and identifying tag. The motor shaft is visibly longer on the endbell side to make it easier to verify that the correct armature is being used. The end of the shaft has a distinguishing taper that makes it easier to check the motor at a glance. The armature also features a tag that’s epoxied into place to make motor tampering easier to detect.

For a stock motor, the most obvious benefit of having a removable endbell is that it can be disassembled for maintenance. The commutator can be trued on a modified comm lathe that provides a much cleaner, truer cut than a stock lathe and should result in slight performance improvements. If this becomes standard, hobby shops and serious racers will no longer need to have both a stock comm lathe and a mod lathe because the stock armature can be removed from the motor.

So what happens if one of the Paradox’s components is damaged or wears out? They’ll all be available separately, so, for example, if the comm has been cut so many times that the armature is no longer usable, you simply buy a new armature for somewhere around $12 (instead of buying a new motor for $40). The same goes for the motor can; if its magnets lose their strength over time, it can be replaced for somewhere around $12.


How will the introduction of a stock motor with a removable endbell affect the hobby? For consumers, I think it’s a positive move: a stock motor that may easily be maintained will last longer, and it’s cheaper to buy individual components than an entire motor.

For the racing set, there are some concerns: will a stock motor with a removable endbell allow cheating? There has been much speculation about this, and concern about cheating is why we have fixed endbells. I think it will reduce cheating. Let me explain: a number of stockclass “lifers” are very adept at removing the “fixed” endbells on current stock motors; they make modifications and reinstall the endbell without leaving any sign that the motor has been altered.

At most tracks, there is very little technical inspection because it would destroy motors (the armature wire would have to be removed to verify that it’s the proper 27 turns of 22-gauge wire). It’s very time-consuming and expensive for the track operators to inspect even the suspect motors, so they often don’t do it at all.

The Paradox doesn’t have to be disassembled to be inspected. Its extended, tapered motor shaft is clearly visible even when the motor is installed in a car. The tag on the armature may be checked through the vents in the motor can (in certain types of vehicles, the motor may have to be removed for this inspection). To verify that the timing hasn’t been altered, officials can check the perfectly aligned marks on the can and the endbell. If the timing has been changed, a look at these marks will make it very obvious because they will no longer be perfectly aligned.

If a full inspection is necessary, the armature can be removed from the can and stripped of its wire. Even if the inspection has to be taken this far (and in most cases, it shouldn’t), a new armature costs far less than an entire motor.

Other concerns for the racing community involve factors that aren’t covered by current rules. Could a hand-wound armature be used to replace the machine-wound stock armature? Might you, for example, be able to use a Reedy armature in a Trinity can? Now that motor components may be replaced individually, will cost controls be established for motor parts as well as for the whole motor?

In the final analysis, a stock motor with a removable endbell can be positive for consumers, track operators and hobby shop owners. If the race-sanctioning organizations institute rules that prevent additional costs from being introduced in the name of performance, there is a very good chance that running or racing a stock-class motor will look a lot more attractive.

‘Addresses are listed alphabetically in the Index of Manufacturers on page 273.

Copyright Air Age Publishing Jan 1999

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