540 Brushed Motor Care, Installation, and Troubleshooting

Quick and dirty summary

If you purchased a Holmes Expert or Pro motor you are ready to time and install.  A Holmes Sport motor will need breaking in for best power and life.

Always gear your vehicle to prevent motor overheating!  If you are not sure, start with 5/1 spur/pinion ratio if possible.  The #1 cause of motor destruction is overgearing.  Keep your motor under 160f for long term running, or 180f for short runs.  If the motor is always too hot, a larger rotor or switch to brushless is needed.   Axial Wraith trucks going bashing speeds is an example of needing Puller 540 brushed or Brushless systems to keep up with demands of power.

Give your motors 6 to 12 degrees timing advance for best brush life.  Brush and Commutator maintenance will depend on the motor speed.  It can be as frequent as every 20 minutes for fast motors such as 13 turn or 21 turn TorqueMaster 540s, or a whole season for slower motors such as 55 turn through 35 turn TorqueMaster 540s.

Cleaning your motor can be done with soap and water.  Alternator and Starter motor cleaner from automotive supply stores can also be used.   Oil your bearings with one drop of 10W-30 motor oil.

Any brushed motor can work well in water, but all motors must be dried afterwords. Compressed air is easiest to remove water fully.  You can also take it apart and dry with a towel, then break it in to warm the parts and evaporate remaining dampness.  Re-oil the bearings after the motor is dry, but before motor is ran. 

Replace your brushes when they are 5mm.  If they are shorter, commutator damage will occur.  A comm cut is recommended every two sets of brushes, for best motor life.   A comm cut is recommended after running in water or dirty conditions, for best motor life.   Holmes Hobbies offers this service if you do not have access to a motor lathe. http://holmeshobbies.com/Brushed-Motor-Rebuild.html

Motor Break In

Place the motor on a stable surface, or remove the pinion if motor is installed in a vehicle.   Allow motor to spin with no load.  Apply between 2.5 and 3 volts to your motor for three to five minutes with  six to twelve degrees timing.  The brushes should be “seated” with at least 90% of the brush face touching the commutator.   Slow motors such as 55 turn TorqueMasters may need more time to fully break in.  Some brush types may require more time.   Visually inspecting the brush during the process will ensure you see the changes and know the condition.

Gearing

Volt up, Gear down!  This has been our motto for a decade, and it still holds true for motors of all types.   Use 11.1v to 14.4v lipo whenever possible.  Using voltage to gain motor speed while gearing down to slower wheelspeeds is win-win.  Torque at the wheel is gained, low speed control is improved, and overall horsepower will increase as compared to low voltage and high geared systems.   You should always keep a close eye on your system when installing a new motor or adding voltage.  Keep the motor temp under 160f for long runs and 180 for short runs!  When in doubt, fit the largest spur and smallest pinion gear possible.  For most R/C Crawling rigs we suggest 15/84 or slower as a good starting point.   For robotics installation use your best judgement.

Timing your motor

Unless specified at the time of purchase, your brushed motor will have neutral (zero) timing and operate properly during clockwise (CW) and counterclockwise (CCW) rotation.  When the motor will rotate in one direction more than another,  timing advance is suggested. You can check the timing advance in many ways.  We suggest using more than one method until you are familiar with the task.  We suggest 3 volts for easy motor handling. 

• 1: The motor will spin faster “forwards” as compared to “reverse”.

• 2: The no-load amp draw will be higher than neutral timing.

• 3: A visual inspection reveals advanced brushes.

   

1: You can check to see if the motor spins slightly faster in forwards direction with a tachometer, or with motor sound.  A faster motor or machine will generate higher pitch noise.  Press your motor against a table while you change timing to listen for the increase in RPM to indicate advanced timing. 

2: Timing the motor with amp draw requires an amp meter, we suggest all motor owners to have this tool.  Loosen the endbell and spin the motor with low voltage.  Rotate the endbell slowly until you find the lowest amp draw.  This is neutral timing, and may not be exact to the motor markings because of motor variation and brush tilt.  10 to 20% higher no load amp draw in the advanced direction is a safe setting.

3: To advance the timing visually, rotate the brushes (endbell) in the opposite direction of motor shaft rotation. This energizes the segments sooner during rotation. If your motor rotates clockwise for forward locomotion, rotate the enbell counterclockwise in relation to the can. Most Holmes motors have marks on the can and endbell that indicate 12, 24, and 36 degrees for CCW pinion rotation.  About 6 degrees of timing is what we have found to be an optimal balance of brush life and reverse/ brake performance below 20,000 rpm.  Twenty degrees of timing is best for very fast motors such as the 13t TorqueMaster for Twin Hammers. 

 

 

Brush Replacement

Your motor will need brush replacement, it is only a matter of time!  We suggest that “540” brushes are replaced when they are half the original length, this is about 5mm.  If you wait too long the armature can be permanently damaged.   This could be required every 20 minutes of runtime for a fast motor, like a 3000kv 20t TorqueMaster.  This could also take a whole season for a 1000kv 55t TorqueMaster!  It is always best to inspect the motor before every run.

 

Commutator Cutting

A freshly cut comm will make an old motor spring back to life!   Look at how pretty this copper commutator looks, yours should look like this after a new comm cut…

 

 

Brushed motors need their commutator serviced for top life and performance.  We suggest a cut every two sets of brushes or every time the motor is run in dirty or wet conditions. At the least, it should be cut whenever there is noticeable drop in performance or physical signs of wear.  We recommend a minimum comm size of 6.86mm for 7.5mm comms, and 9.14mm for 10mm comms.

The basic guide to cutting the commutator:

Most “toy” lathes for commutator cutting use a rubber O ring to drive the armature.  Toy lathes using a 55t motor generally work best between 11 and 12 volts, whereas lathes using 27t motors run well between 2.5 and 4.5 volts.  These are loose and fast recommendations though, if you want to get technical then you need to know the speed of the commutator face.  It is generally safer to spin the armature slower to prevent the risk of damage, but you must make extremely light cuts at slow speeds.

The more technical aspect of turning copper:

Holmes uses HSS and diamond bits depending on what is handy. Both can do a superb job. Holmes does not recommend using standard carbide bits for the amateur as they typically do not have proper rake for copper.  Learning to cut your own HSS bits will save money and make a great skill! Good diamond bits can last thousands of cuts, but one mistake will break it!

Commutator surface speed of 200 to 300 feet per minute is good for all around cutting with any bit.   A 10mm diameter commutator converts to .39 inches roughly. Multiply times Pi and we get 1.2246″ circumference. That is close enough to .1 foot, so we can turn the 10mm comm at 2000rpm and expect a good result. Smaller 7.5mm comms will need to spin 33% faster for the same face speed.  Faster, lighter cutting allows for better cuts with a machine that is less rigid, as many of the toy motor lathes tend to be quite flexible.  It is for this reason that we recommend cutting as fast as possible with light depth of cut.  

Most toy motor lathes have roughly a 3 to 1 geardown from drive motor to armature. Using a 55t drive motor on 11.1v gives about 9,000rpm; a 27t motor would be ran at 3.7v for the same speed. This gives an armature speed of 3000rpm and face speed around 300fpm for the 10mm commutator.  One can switch to 7.5mm comms and the face speed is 225fpm, still in a good zone without having to change the voltage.  A laser tach aimed at the flat spot on the armature shaft being cut is an easy way to find the face speed of any setup if you are unsure of the equipment. Divide RPM by 10 for 10mm comms and divide by 13.3 for 7.5mm comms. Keep the result between 200 and 300 for easiest and most consistent work. 
Be patient, be cautious, and always err on the side of too little material removed and you will be fine!

Cleaning

Use dish soap and a toothbrush, or alternator and starter motor cleaner from an autoparts store.   Spray it off with compressed air or dry with a towel.  Finally, relube the bearings with oil such as 10w-30 or lighter.   Do not use unknown aggressive chemicals, as they can weaken the glues holding the motor parts together.

 

Troubleshooting

The brushed motor is a simple machine.  If you are having problems with the motor there are only a few causes, typically the commutator or brush condition.  Bad bearings or a shorted armature can also cause running issues.

Problem- Motor does not work at all (no noise)

• Ensure power is connected to motor properly
• Check brushes for proper length and contact to commutator, they should be free moving and held by the spring.
• Inspect the commutator for burned condition, cut if needed.
• Is your battery plugged in and the motor controller in proper working order? Try another radio or motor controller if possible.
• Check the motor resistance with an ohm meter.  If it shows open circuit, you may have a dead armature or VERY dirty commutator.

Problem- Motor sometimes runs, runs weak, rough, or needs a push to start

• Check brushes for proper length and contact to commutator, they should be free moving and held by the spring
• Check commutator for wear and contaminants.  Cut the commutator if needed
• Spin the motor slowly by hand and feel if there are spots where the brush is hanging on the commutator.  If so, cut the comm.
• Inspect the motor for contaminants, small particles can cause the motor to hang.  Clean it out!
• Bearings should spin absolutely free with no rough or sticking spots.  Replace if needed.
• If all else fails, there may be a shorted section of the motor.  In this case a new armature is needed.

 

Contact us through holmeshobbies.com for further assistance!