Wednesday 23 September 2015

Controlling treadmill motors by Pulse Width Modulation.

Permanent magnet DC motors used in fitness industry

Home use treadmills are equipped with DC (Direct Current) motors.  The Permanent Magnet DC Motor (PMDC) is the most commonly used type of direct current motor available producing a continuous rotational speed that can be easily controlled.

The rotational speed of a DC motor is proportional to the Voltage applied to the motor.

PWM Regulation as standard regulation for home use treadmills motors

PWM regulation on a treadmill DC motor

Pulse width modulation (PWM) speed control works by driving the motor with a series of “ON-OFF” pulses and varying the duty cycle, the fraction of time that the output voltage is “ON” compared to when it is “OFF”, of the pulses while keeping the frequency constant.

The voltage applied to the motor can be controlled by varying the width of these applied pulses and thereby varying the average DC voltage applied to the motors terminals, ie, the longer the pulse is “ON”, the faster the motor will rotate and likewise, the shorter the pulse is “ON” the slower the motor will rotate.

Advantages and disadvantages of treadmill motor regulation by PWM

The use of pulse width modulation has the advantage in that the power loss in the switching transistor is small because the transistor is either fully “ON” or fully “OFF”. As a result:
  • the switching transistor has a reduced power dissipation 
  • linear type of control which results in better speed stability
  • the motor can be rotated very slow without it stalling
The main disadvantage is that the motor is driven with high voltage pulses (about 300VDC for a network current of 230VAC, 150VDC for 110 VAC). When a reduced rotational speed is required by the application (such as walking at slow speed on the treadmill) associated with the heavy load (user weight, treadmill maintenance conditions, running belt friction factor) the motor is subjected to heavy stress and overheating. This could bring easily to electric leaks inside the motor and consequent damage to the motor itself and/or controller.

Friday 4 September 2015

Adjusting treadmill motor position when replacing treadmill motor

When installing a replacement motor, a difference in the position of the fixing holes may be noted

In this case, you must not work on the threaded holes on the motor.

Drill the motor fixing bracket on the treadmill frame. If it's a curved bracket, it's better to do uninstall it before drilling

fix the motor in correct position, so that the belt is perfectly aligned, the motor is in good contact with the bracket and the fan doesn't touch anything in the back.

As an alternative to drilling the motor bracket, you could fix the motor with metal bands /jubilee clips (the one used in plumbing) as they are resistant enough for this.

Wednesday 2 September 2015

Reinstalling the Rear Roller (Nautilus)

8.1   Slide the rear roller inside the belt and let it hang loose.
8.2   Install the alignment bolts through their holes in the  end cap and into the holes on the roller (see Figure 8.3).

8.3   Install the end cap onto the rear of the treadmill, making sure the alignment pins go into the holes on the ends of the side rails.
8.4  Hand tighten the adjustment bolts.
8.5   Align the walk belt so that the edges of the belt are equal distance from the side rails.
 8.6   Tighten the adjustment bolts to take the slack out of the walk belt.
8.7   Perform the belt tension and belt tracking procedures outlined before

9.    Reinstall the Treadmill Hood
9.1   Install all treadmill covers previously removed in step 1.2.
9.2  Plug the AC power cord into the treadmill, and turn on the treadmill circuit breaker switch.

Nautilus treadmill maintenance: Attaching the Deck & Reinstalling the Front Roller

6.  Attaching the running Deck

6.1  Align the deck mounting holes with the compression mounts.
6.2  Install all eight (8) deck screws and hand tighten.
6.3   Use Loctite 243 and a 10 mm socket to tighten all the screws to 15 in.lbs. (1.7Nm).


7.  Reinstalling the Front Roller

7.1  Slide the front roller inside the walking belt.
7.2   Insert the end of the roller opposite the pulley into the cut-out on the side rail (see Figure 7.1).

7.3   With your free hand, slip the motor drive belt onto the Front roller pulley and the motor flywheel.
7.4   Align front roller pulley with motor flywheel, then install the retainer plates in the grooves on the roller. Tighten all the screws on the retainer plates. (see figure 7.2).

7.5  Place Tensioner assembly onto the tensioner bracket and screw in bolt finger tight.
7.6  With a 15/16 wrench. Place on the large nut of the assembly and push forward until the adjustment knotch is even with the top knotch on the left side of the wheel and hold. (See Figure 7.3 and 7.4.)

7.7  Place a 9/16 wrench on bolt and tighten (counter clockwise).

Inspection and Cleaning + Installing new running belt (Nautilus) checking Belt direction arrow

4.    Treadmill Inspection and Cleaning

4.1  Check the compression mounts for any wear and cracking. Make sure they are tight.
4.2  Check the deck for signs of wear.
  Important: Do not apply any cleaners or petroleum products to the deck surfaces.
4.3  Inspect the motor drive belt for wear and cracking. Cracking is prevalent between the grooves on
the belt.
4.4 Vacuum the deck and inside the motor housing.

5.  Installing the New Walk Belt

5.1   Slip the new belt over the deck. Make sure the arrow on the inside surface of the walk belt points in the proper direction of belt travel (see Figure 5.1) toward the rear of the machine.

5.2   Lift the deck with the installed new walk belt and place it on the compression mounts.
5.3   Lift and slide the belt until the arrow is visible on top of the deck. Verify that it points toward the back of the treadmill.

nautilus treadmill: Removing the Walking Deck

3.1  Remove the right and left Rubber Side Extrusion exposing the Side Rail Bolts (see Figure 3.1).

3.2  Remove the right Side Rail Bolts and Side Rail exposing the Deck Bolts, then repeat for the left side (see Figure  3.2).

3.3  Remove the left side Deck Bolts, then repeat for the  right side (see Figure 3.3).

3.4  Lift and slide the Walk Deck out and replace if needed  (see Figure 3.4).

3.5 Reverse steps when re-installing the Walk Deck.

IMPORTANT:  When reattaching the Walk Deck with the Deck Bolts, apply a small amount of Loctite #243 on the threads and torque to 15 in. lbs

Replacing the Walk Belt (Nautilus) whenever the walk belt is still too loose after adjusting the tension or when the belt is worn or frayed

Perform this procedure whenever the walk belt is still too loose after adjusting the tension or when the belt is worn or frayed.


1.   Remove the Treadmill Hood
1.1  Turn the treadmill circuit breaker off, and unplug the power.
1.2  Remove the Front Trim, Right Lower Cover, Left Lower Cover, and Top Motor Covers.

2.   Remove the Rollers

2.1  Remove the left and right end caps (see Figure 2.1 and 2.2).

2.2  Carefully slide the roller out from the machine (see Figure 2.3).

2.3  Remove the Kick Plate and four (4) screws (see Figure 2.4).

2.4  Remove the Pivot Bolt on the left and right side of the Upright Weldment (see Figure 2.5).

2.5  Remove the screw from the Front Roller Retaining Bracket on the left and right side, then remove the brackets (see Figure 2.6).

2.6  Remove the Bolt and Tensioner assembly from the frame (see Figure 2.7 and 2.8).

2.7  Slide the Front Roller over to the left, then use the belt to lift and slide out the roller from the
machine (see Figure 2.9).

Adjusting belt tracking (Nautilus) whenever the treadmill belt moves to one side or the other.

Perform this procedure whenever the belt moves to one side or the other. Stay off the belt when adjusting  the tracking.

1. Start the treadmill at minimum speed and grade.
2. Increase speed to six (6) mph, and make the following adjustment:

2.1. If the belt moves to the right, turn the right adjustment bolt 1/4-turn clockwise.
2.2. If the belt moves to the left, turn the left adjustment bolt 1/4-turn clockwise.

3.  After making an initial adjustment, run the treadmill for five (5) minutes and observe how the
belt tracks. If the belt continues to move away from the center, adjust the appropriate side until
properly centered.

Adjusting Belt Tension on Nautilus Gym Treadmills

Adjust the belt tension whenever the belt slips or moves unsteadily during operation by following the
steps below:
1.  Start by loosening the two (2) adjustment bolts (see Figure 1).

2.  With the walking belt loose, place two marks 35 inches (89 cm) apart on each side of the belt
near the edge. The belt must be loose enough for you to move it from side-to-side on the front or
rear roller (see Figure 2).
3.  Turn the adjusting bolts clockwise by equal amounts until the marks are between 35-3/16 inches
and 35-5/16 inches apart. Proper tension for the walking belt is between .5%–.6%. This should
be about six full turns of each adjustment bolt from the point where the belt begins to stretch.
Important: Do not exceed 35-5/16 inches.


4.  Test the belt by running on the belt at about four (4) mph.  Hold the handrail lightly and resist the belt movement with your feet.


5.  If you feel the belt slip on the front roller, increase the tension of each adjustment bolt by 1/2 turn
and re-test. If you feel the belt slip again, check the tensioner adjustment.

Suggested maintenance for Nautilus treadmills

Daily Treadmill Maintenance

• Inspect the power cord and walking belt for wear.
• Check the position of the walking belt. Verify it is not rubbing against the frame. The belt should be
evenly spaced on the deck within 0.25 inches of each side rail. Adjust the belt if necessary.
• Check the optional side handrails to ensure they are fastened securely.
• Remove potential hazards from the treadmill area.

Cleaning Treadmill
Keeping the Nautilus ®  Commercial series T9 treadmill clean on a regular basis will help to improve
operation and increase the lifespan of the components.

•  Keep the treadmill and controller free of dust and debris. Use a damp sponge to wipe the exteriors
and walking belt; do not soak surfaces. Dry all surfaces thoroughly.

•  Elevate the treadmill to maximum incline and vacuum the floor under it to prevent excess dust and
dirt from interfering with operation.
•  If the magnetic key is being used, check it for rust. If you detect rust, replace the magnet. Rust on
the magnetic key will cause power-up problems.

Treadmill Interior

Depending upon the treadmill environment, dust and or lint can accumulate under the hood. Clean the
interior of the treadmill following the procedure below:

1. Turn the treadmill circuit breaker off, and unplug the treadmill power cord.
2. Remove the two (2) screws on the treadmill hood.
3. Lift off the hood.
4. Clean inside the unit.
5. Reinstall the hood and the two (2) screws.
6. Plug in the treadmill power cord, and switch on the treadmill circuit breaker.

Model T912 / T914 / T916 by Nautilus. Viewing Maintenance Information | Engineer mode for treadmills

Treadmill Model T912

The total time and distance the treadmill has been in use can be viewed using the Maintenance Screens.

This information can help you schedule treadmill maintenance and check treadmill usage.
To view the treadmill’s  total Run-time and total Distance information:

1. Press and hold ENTER and STOP keys on the console for at least 3 seconds.
2. Use the INCLINE UP/DOWN keys to scroll to ConF selection.
3. Press the QUICKSTART key.
4. Use the INCLINE UP/DOWN keys to scroll to view TOTAL HOURS and TOTAL MILES.
Model T914 & T916
In addition to the total time, the distance the T914 or T916 treadmill has been in use can be viewed using
the Machine Status console codes.
To view the treadmill’s run-time information:

1.  Press the SPEED UP key on Ergo Bar, then 4, ENTER on the console.
2. The words "Machine Status" will be displayed.
3. Press the SPEED UP key on Ergo Bar, and scroll to "Run Hours".
4. The current Run Hours will be displayed.
5. Press the CLEAR key to exit. 
To view the total distance the treadmill has been used:
1.  Press the SPEED UP key on Ergo Bar, then 4, ENTER on the console.
2. The words "Machine Status" will be displayed.
3. Press the SPEED UP key on Ergo Bar and scroll to "Distance".
4. The current Distance in the current machine units (Miles/KM) will be displayed.
5. Press CLEAR to exit.

Routine Maintenance Schedules
Performing routine maintenance will help prevent unnecessary wear to the treadmill and/or injury to the user. The maintenance schedules are meant only to serve as a guide. Depending on where and how the treadmill is being used, more frequent routine maintenance may be required.