Disneyland Mark VII Monorail - motor upgrade

Most motor upgrades draw considerably more current than the original motor. No surprise there since there is no free lunch with motors, more power out takes more power in. I tested the motor drive circuit of a Mark VII model to see how much power it can deliver to a motor. The answer is "not much". At 230 mA, about what the stock motor draws, the voltage drop is about 0.2 V. At 500 mA, what a faster motor may draw, voltage drop is up to 0.5 V. It gets worse as the current draw goes up, to the point where the power is limited and the voltage drops to where the monorail will probably stop.

The solution, if we want more speed, is to power the motor with a different circuit and control that circuit with the original outputs to the motor. Pololu makes this almost easy with their DRV8835 circuit board, the original motor wires (brown and black) can be connected to the circuit board and the board powers the motor (up to about 2.4 amps, more than we should need).

https://www.pololu.com/product/2135

Disney's designers used tiny wire which also limits the current to the motor. the 24 AWG I install is 4x as large as their 30 AWG. Btw, my choice for motors is Tamiya's Torque Tuned (add carbon brushes), others like the more powerful Tamiya Hyper Dash (which may come with carbon brushes installed)..

The Mark VII power switch does not actually disconnect power (like the WDW model does) but controls a FET switch. Because of this the auxiliary circuit board continues to draw a small amount of power (about 4 mA) when the monorail is switched off. This will cause the batteries to be drained in about 3-4 weeks so if the monorail is not run for a long time the batteries should be removed (as they should anyway to prevent leakage).

The details: the wires from the motor go to EN (BR) and PH (BK). O1 and O2 go to the motor. (these are all on side "A" of the circuit board)

VM goes to battery +, GND goes to battery -. VCC goes to the wire from the switch that does not have power when the switch is off (on mine this is the middle terminal of the switch but this could vary so check first).

Using just side "A" provides up to 1.2 A continuously which is more than enough for most motors. Paralleling side "A" and side "B" (OUT, ENABLE, and PHASE) doubles the available current if you need more.

I use silicone adhesive to secure the circuit board in the left rear corner of the monorail. The chips on the board should not touch the plastic as they can get hot if the motor stalls.

copyright Pololu

and of course the usual disclaimer: I have installed three of these, all of them worked perfectly, YMMV...

This still does not address the noise and roughness of the original gearbox, for that I have WhisperJet.

Here is a photo of where I placed the components:

The motor controller board is on the left side of the lower shell, where the bunch of wires go. The voltage converter for the white LED headlights is secured to the remote board, on the other side from the black glob (otherwise known as the remote controller chip).