Updated on July 7, 2019
Programming a 1958 Edsel Pacer’s Teletouch Transmission
In 1958, the Edsel was born. This car had incredible features that were unheard of in mid-range cars of the time. One feature in particular, the Teletouch Transmission, was supposed to carry the car into the future but ended up being part of its demise.
I own a 1958 Edsel Pacer. This car originally came with a Teletouch transmission, which is essentially a windshield wiper motor which has been customized for Ford.
The design of the motor is the same as a windshield wiper motor with a custom analog servo attached to the armature. More about that will be described in a future post, with images.
Inside the car are a set of buttons in the center of the steering wheel. The buttons are designed to stay centered and level while the steering wheel rotates around them. As you push a button a contact is made, which powers a circuit, rotating the motor into a new position. When the transmission shifting motor has reached the end of the rotation, determined by contacts inside the servo part of the Teletouch motor, it stops and the transmission is locked into gear.
While there were numerous problems with the Teletouch transmission system, I will only cover those that lead me to the decision to reinvent this system.
- The original fuse was a 10amp bus fuse. The motor needs at least 12amps for small hills, possibly more current for when the transmission is locked in Park.
- The engineers of the day decided to route the motor’s wiring unreasonably close to the exhaust manifold, causing the wiring to melt and short circuit.
- There was nothing that prevented owners from going directly from Park to Drive, but doing so would reduce the motor’s lifespan, or break it.
- The motor was too weak. Not only were the fuses wrong, but the old design of the motor wasn’t as efficient as new windshield wiper motors of today.
- Repairing a Teletouch Transmission motor is upwards of $350 each time it burns out, and I had already replaced 2 motors.
Let me just point out that this short list shouldn’t hide the fact that this motor is absolutely ingenious. The engineers of the late 50s designed an analog servo motor out of relatively new windshield wiper motor technology (at the time most cars had vacuum windshield wipers, including the Edsel) and created relays, circuits, and lockout mechanisms that prevented the transmission from shifting into gears when it was in motion. Looking over this today, it’s absolutely incredible.
Here is a PDF copy of the diagnostics manual hosted by Edsel.com.
Planning and Waiting
I’ve been planning this upgrade for the last 20 years, however the technology has just recently become available, and cheap enough, for me to complete this project by myself. I also needed more knowledge about programming, electronics, and hardware development.
I took Electronics Engineering in college, Computer Science, programmed all my adult life, taught myself hardware programming with Arduinos, and hacked circuits and motors until they worked the way I wanted.
My first idea was to use an Arduino and a linear servo. Due to some unfortunate power supply issues (battery chargers are not the same as batteries!), I changed course and decided to use a linear actuator instead.
If you’re not familiar with what an Arduino is, it’s basically a miniature computer system with a real processor and input and output pins. It uses a form of C++ for programming and carries the program on EPROM, giving it an instantaneous startup time.
Why not Raspberry Pi?
Raspberry Pis are excellent computers with huge range, but for this particular project it has one flaw.
When a car is started the driver typically only takes a few seconds before shifting into gear. This means that the computer controller needs to be ready within 1-2 seconds after power is restored. Unless customized, the Raspberry Pi, like any computer, takes 30-60 seconds to boot up.
The other concern is improper shutdowns can corrupt a Raspberry Pi’s MicroSD card. I would need to create a method of shutting down the Raspberry Pi safely whenever the car is shut off.
Why a Linear Actuator/Servo?
Instead of a wiper motor perhaps? Wiper motors are not servos. There’s no position sensor, they don’t have feedback. It seems as though newer cars have more intelligent motors, but the older styles, like those that resemble the original Teletouch motor, are simply motors with basic forward, reverse, and high speed wires.
I guess the other choice would be some sort of custom servo motor, or worm gear servo. I thought of this as well, but the amount of force/torque required, and the waterproofing requirements kept leading me to industrial motors that were cost prohibitive and probably wouldn’t have fit in the original housing. I didn’t want to have to invent a new mounting structure to attach a different motor type to the transmission.
Linear Actuators had the beauty of being slim. They had documented torque and load requirements, they were incredibly easy to mount, and programming was a breeze. It seemed like a perfect fit for version 1.0.
The included Arduino code in this Github repository allows an Arduino Uno to interact with a Cytron Shield MD-10 R2 motor controller. The motor controller is then connected to an HDA4-50 linear actuator from ServoCity. This produces 115lbs of thrust for a 4″ stroke.
The 115lbs of thrust is likely not necessary to shift the Edsel transmission, however it was chosen as a good starting point. It’s unclear whether 25lbs of thrust would have been enough while parked on a hill.
The motor is connected to an auxiliary fuse panel with a 10A fuse.
The Arduino is connected to USB car chargers which accept 12V input and produce 5V output for the Arduino.
The USB chargers are each connected to one terminal of the Edsel push buttons with Tap Splice connectors to prevent the original wires from being cut.