Inside the speed-O sensor. And why it's so inaccurate!

Maybe I've missed something. I do not see that using 2 gears to drive a signal generator makes it inaccurate. In the 70's that was a pretty clever way to eliminate a very troublesome and expensive flex cable 8 feet long going from the rear of the propulsion unit to the back of the dash board. The inaccuracy in the system lies in the junk instruments Ferrari always insisted on buying from somebody's cousin Guido. The same junk instruments they buy today.

They could easily be one of the best cars on earth if there was not so much corruption in the procurement process for their vendors. Nothing else explains it. 90% of the parts purchased outside is absolute trash. The in house stuff is done quite well.

 

Hi Brian
I agree completely. I have (much like RJay) been pursuing solutions to various electronic issues on GT4's. Specifically the speedo circuitry. It is so poorly protected from spikes and other vaguaries of automotive +12v systems that it is guaranteed to fail if something else goes wrong, e.g. a bad alternator. The good news is that except for the speedo and tach there are no electronics in the car that matter (I don't count radios

David, I am thoroughly enjoying the photos you are supplying, it is very educational, I will likely need them in the future for my own synchro efforts.
However your description of the sensor drive as sloppy is incorrect . The mechanism you describe is purely mechanical. It guarantees a fixed relationship between final drive ratio and the number of pulses needed to indicate odometer and speed. Even the Veglia sensors are quite solid, considering the heat they have to take near the exhaust. (I think at one time there was a heat shield in that area but can't find any pictures of it. The bolt bosses are on the rear header for it).
If you look at the square socket in the transmission drive end, it is identical to the socket required for driving a speedo cable. In fact the early GT4's had mechanical speedos. I for one wish they had kept it that way. Many European cars at the time started using the same VDO and Veglia style senders to convert from mechnical to electronic speedos without having to retool the transmissions.
The later 308's switched to a different means of generating pulses, after the mechanical design was altered probably to remove costs. Thus we have two incompatible styles of speedo sensors.

I'm realy glad you rescued Mickey though, he must have been hungry after all those years!

 

Hi David
I wasn't really really knocking you. In fact I am glad you posted the pictures, they make it so, mmnnn, so accessible. Please don't stop sharing......

I can supply the dead cockroach, aka the dead IC in my speedometer

Now the hamster, there is an idea. I think by replacing the gear on end of gearbox shaft and making a new casting to hold the drive we could add the HP (Hamster Power) to get the car off the line quicker.

Gerrit

 

That's hilarious! Good joke.