question: hub-mounted speed sensor?

[Farrar]

I don't really know anything about how it works, but I have noticed that some modern cars' ABS use a wheel speed sensor mounted inside the wheel hub. From the pictures I have seen, there's a hole on the top of the hub assembly that the sensor plugs into. I hope I have described this correctly.

I know some folks have been looking for a way to replace their angle drives for a while; would it be possible to come up with a solution which uses a wheel speed sensor mounted in the hub, like a modern ABS wheel speed sensor, but which instead would send a signal to an electronic speedometer/odometer?

Again, I don't know how it works, so I am hoping someone here more familiar with modern cars can chime in and tell if it's possible or not. Or if it's already been done on a DeLorean and I just haven't heard about it yet. Or if it's a bad idea. Whatever.

Thanks in advance!

[Exolis]

I'm not a 100% sure on the location of sensor. I heard some are in transmission now too, but it does make sense for sensors to be in the wheel for traction control systems. In modern cars, the speed goes to the ABS system(now commonly known as Vehicle Dynamic Control) where wheel speed is input to the controller and sent out on the Controller Area Network for other ECU modules to read the Vehicle Speed.

To do this, you would need a meter and VDC system from a modern car (of the same make, model and year) to modify and install on the DeLorean.

I imagine there are other ways that are much more simpler, such as some kind of sensor hooked into a Microcontroller that sends out a processed value to a Display.

[DMCMW Dave]

If I was going to do that I'd put the sensor on/in the transmission rather than on the front wheel.

It's certainly do-able but at this time it would hardly be cost-effective since you'd have to figure out a sensor, some electronics, and a new speedometer head that looks/fits in the original cluster. I'm not sure what the market for a "get rid of your angle drive for $600" solution would be.

[Farrar]

I'm not sure what the market for a "get rid of your angle drive for $600" solution would be.

Probably the same people who spend $4,000 on EFI and turbochargers

[justlooking]

Probably the same people who spend $4,000 on EFI and turbochargers

You can buy a Cable-X, which puts an electronic sensor in place of the angle drive, and then adapts a small DC motor to drive the mechanical speedometer. It's not cheap, though. ~$350.

Not sure how much noise it makes either. Would you like to hear an electrical motor whirring faster and faster as you speed up? Probably not. Then again, if you liked how the BTTF time machine sounded in the movie, it could be perfect!

[jangell]

I haven't had a functioning speedometer for years now. If I hook up an angle drive it dies within 5 miles. The cable feels turns fine until I hook it up to the angle drive, and then it becomes very difficult to turn. I have no idea why.

My plan was to mount an magnet between a couple of the bolts on the transmission's drive flange, and mount a hall effect sensor just above that. I was probably going to 3D print a simple plastic holder that would secure the magnet in place and to mount the hall effect sensor (if I ever get my 3D printer working). Then I was going to to use an Arduino to count the pulses, covert it to a speed, and send it to a computer to put on a large LCD. The computer bit's a longer term project, though; sending it to a simple display like the ones from Adafruit would be much simpler -- like this four-digit clock-like LED display backpack. This whole thing, including all the parts, would be under $50, and the Arduino could be set up for other projects as well.

Of course, it's a very DIY kind of thing, and you'd need a way to mount the display near the instrument cluster, and probably a nice box to put it in. Or you could use some gauge-style electric speedometer that takes pulses or varying voltage as an input, and replace your current speedometer with it. For a while I was toying with using an electric motor to turn the stock speedometer's drive cable, but my knowledge of motors is fairly limited, and I had trouble finding a motor that could run at very slow speeds but also go up to higher speeds to get the speedometer up to 85 MPH just by varying the voltage.

I still want to do EFI one of these days...

-- Joe

[jangell]

You can buy a Cable-X, which puts an electronic sensor in place of the angle drive, and then adapts a small DC motor to drive the mechanical speedometer. It's not cheap, though. ~$350.

Neat -- I didn't know that existed. I agree the price is pretty steep, though, although probably cheaper than the number of angle drives I've gone through.

-- Joe

[Farrar]

If you DIY, it doesn't necessarily have to be massively expensive... Once upon a time, someone found a speedometer from another car 1997 Nissan Maxima?) which would line up perfectly with the face of the D speedometer. If you could drill two small holes in the wheel hub (one for the sensor, one for the screw to mount it), and have it talk to the Nissan speedometer, you would not be out an inordinately huge pile of cash, and have something which, ostensibly, would last a long time.

[Edit: the reason I was thinking of having the sensor mounted at the left front wheel is because it's closest to the original design of having the angle drive on the left front wheel. No other reason, really.]

I still don't know how those wheel hub-mounted sensors works, though -- how they get their pulse, I mean.

However, I think from the general consensus here it seems that a transmission-mounted sensor is better. Why is that? More reliable output?

[jangell]

I was going to mount on the transmission just because it was easier to fit in there, and I wasn't really sure how to make something work where the angle drive was, or mount something to the hub area.

I also toyed with the idea of using an electric motor with a rubber head mounted on the shaft, which was pressed against the transmission drive flange. As the car's wheel turned, it would turn electric motor, which in turn would generate electricity and be read by an Arduino. The advantage was that it would react more quickly to speed changes than counting how quickly the magnet went around the axle, but the down side is that the motor could fail, since it contained moving parts and would be in physical contact with another moving part (magnets and hall effect sensors should never fail, or at least last a very long time).

-- Joe

[Farrar]

By the way: In theory, this would only be needed for drivers of manual transmission DeLoreans.