How to: Select and Maintain your Motor

17 frequently asked questions

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Based on info from Trinity and various magazine articles
  1. Why does my motor run slow and drain my batteries quickly?
  2. When should I change my brushes?
  3. Is it important to true the commutator?
  4. Which brush is best for my application?
  5. How do I know when I need a new motor?
  6. What can I do to my stock motor to make it faster?
  7. What does timing in a modified motor do?
  8. What gearing should I start with on my Buggy?
  9. What gearing should I start with on my Scale Saloon?
  10. What does brush spring tension do for my motor?
  11. My car glitches with a particular motor, how do I fix this?
  12. Can too much comm drop solution wreck my motor?
  13. What's the performance difference between a single, double, triple, quad, etc...
  14. What makes a 10 turn faster than a 15 turn?
  15. When would I want to use a Torque armature over an RPM armature?
  16. How do I install capacitors on my motor and why would I need these?
  17. Do I need to break-in new brushes when I fit them?

 

1) Why does my motor run slow and drain my batteries quickly?
Normally the reason is a deterioration in the brush and commutator condition. If you have several runs on the same motor without maintenance, chances are the brush has too many heat cycles on it, has turned colors,and no longer makes good contact. This causes the brush to wear the comm more than it should. The end result is a motor that arcs, runs slow, and uses more battery than it did when it was new.
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2) When should I change my brushes?
Brushes should be changed if they discolor or are excessively worn (photo 3). This can happen in one run if the motor is over geared and the amp draw is extreme (photo 2). On the other hand, if everything is right and you are in a circumstance where you are not hard on the motor, brushes can last quite awhile. Typically in a competition you will get 8 to 10 runs out of a set of brushes, then you will see performance severely decrease until you clean the comm or true the comm and replace the brushes.
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3) Is it important to true the commutator?
Yes. New brushes on a bad comm wear out quickly. Worn commutators are not round, so the brush bounces, arcs, burns, and is no better than your old ones were in a couple runs.
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4) Which brush is best for my application?
Go to the Trinity Website for full details for their motors.
Click Here
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5) How do I know when I need a new motor?
As a general guide it is probably best to buy a new motor when the comm cannot be skimmed any further as it has reached it's minimum size. Theoretically, you can replace components and re-zap the cans for a long time, but sometimes it is not practical. Today's magnets are durable but over heating will kill the field. If you have a comm lathe, and your comm is at the .270 inch point, it's time for a new one. Trinity will not race an armature with a comm under .270. There are very few runs left at this diameter.
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6) What can I do to my stock motor to make it faster?
There are several things, but good maintenance is one of the most important. Starting with the bushings, make sure the armature is free as it spins. If it feels as if it is binding, either run the motor with a little bushing buster (RC4049) or spin it with a Dremel® until the shaft has no drag. You do not want to go too far since the bushings will wear in as you race. If they are too loose, the comm won't stay in one place long enough for the brushes to make contact.
Next, shim the armature so that it won't touch either bushing, there should be a little play on each side of center. Use our Teflon® shims (RC4030) for this. Motors create their own magnetic centre and the armature will move to the middle of this magnetic field. If not shimmed this way, the armature will create drag against one bush as soon as the armature is energized and forces itself back into its' magnetic centre. Finally there are the brushes. There is no one brush setup. Trinity recommend their (RC4499). For touring or heavy cars, use a full brush and heavy spring. For 1/12 scale and light cars you can cut up the brush and use lighter springs.
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7) What does timing in a modified motor do?
As a general rule, the more timing, the faster you go, and the more battery you use. If racing, you need to gear down to finish a race when timing is added.
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8) What gearing should I start with on my Buggy?
(As a guide, drop one tooth on the pinion for every turn you drop on the mod motors)
Losi XXX 48 pitch (Stock - 23/78) (12T Mod - 21/78)
Assoc. B3 48 pitch (Stock - 22/81) (12T Mod - 19/81)
Schumacher FireBladeEVO 48p (Stock - 23/95) (12T Mod - 20/95)
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9) What gearing should I start with on my Scale Saloon?
(As a guide, drop one tooth on the pinion for every turn you drop on the mod motors)
Losi XXXS 48 pitch (Stock - 25/90) (10T Mod - 19/90)
Assoc. TC3 48 pitch (Stock - 26/72) (10T Mod - 21/72)
Schumacher Mission 48p (20t pulley) (Stock - 23/90) (10T Mod - 19/90)
Yokomo MR4 48pitch (Stock - 26/81) (10T Mod - 20/81)
Hudy X-Ray 48 pitch (Stock - 27/93) (10T Mod - 22/93)
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10) What does brush spring tension do for my motor?
Spring tension keeps the brush on the comm. Usually, the higher the amp
draw, the heavier the spring. A light spring in an off road car will arc and
burn up the brush, but a light spring in a 1/12 scale car works great since
they are 1/2 the weight and run twice as long. In general the lower the turn on the motors the heavier you want the brush spring. Trinity recommend (RC4033S) for 4 or 5 minute mod races and (RC4028S) for 8 minute mod 1/12 scale. For stock 4 or 5 minute races use either (RC4028) or (RC4389S).
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11) My car glitches with a particular motor, how do I fix this?
Glitching can be caused by a bad comm / brush condition, radio interference, bad capacitors on the motor, the antenna touching metal, or the receiver mounted too close to the speed control. Start by checking the condition of the brush and commutator. If the comm is black either skim it orclean it using a Trinity Comm Pen (RC4053) and replace the brushes. If it still glitches check out the article on Radio Glitches.
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12) Can too much comm drop solution wreck my motor?
Drops used in the wrong way will plug the pores in the brush and create arcs. If you use drops, you need to rebuild the motor more often. Only a few drops per run are needed and the motor should be cleaned after each run with motor spray.
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13) What's the performance difference between a single, double, triple, quad, etc...
Rule of thumb....Singles have the most bottom end, then doubles and so on. Multi-wire armatures usually move the power band up in the RPM range. There are exceptions to this rule, but this is a good guideline.
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14) What makes a 10 turn faster than a 15 turn?
The resistance of the wire. The length used for ten turns is much less than 15 turns of the same wire and with fewer turns there is room for thicker wire. An extreme example is a stock motor since it's 27 turns of relatively thin wire. This also goes for wire size. The larger the wire size the less resistance there is and the faster the motor will run. Less resistance means more electricity can be passed and hence more power generated.
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15) When would I want to use a Torque armature over an RPM armature? or vice versa?
Torque arms, as they are named, make bottom end. Trinity use the torque blank in nearly every class. We can use the rpm blanks in oval racing if the track is large, or in off road when you do not want bottom end because of slippery track conditions. They are also good for F1 cars.
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16) How do I install capacitors on my motor and why would I need these?
Capacitors help eliminate electronic noise from the motor that can cause radio problems. Most motors have them pre-installed now. If not already installed they can be fitted externally.
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17) Do I need to break-in new brushes when I fit them?
As received, the brushes in most motors should require no break-in period. If however you elect to change to a different type of brush, follow that brush manufacturer’s recommendations for use and break-in.
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Running your Motor: First oil each bushing (bushing motors only) with one drop of RC4026 Stock motor oil, install your new motor into your R/C car or buggy, connect the motor leads from your speed control, and off you go. If you are unsure of how to properly gear this motor for your application, please start on the conservative side (smallest pinion) and work your way up until you find the optimum gear ratio.

 

 



A Hudy comm lathe
A 10 double motor armature
A complete motor end with brush wires soldered on for better conductivity
The brush holder and 2 sets of brushes