[Wesley Kagan] is building a Corvette with a V12 engine swap. Much of the driveline will be entirely replaced, which means the components to drive the mechanical speedometer and tachometer will no longer be present in the final car. Instead, [Wesley] came up with his own electronic gauge conversion to do the job.
It’s a build that respects the original aesthetic of the car, reusing the original gauges but driving them differently. In place of the original mechanical drives from the transmission and distributor respectively, the speedometer and tach instead get servos installed in the back with a 3D printed gear train. The odometer gets its own continuous rotation servo, too. An Arduino Nano is used to drive the servos, using data from a GPS module and the car’s ignition system.
Files are available for anyone wishing to 3D print parts to modify their own gauges. We can’t wait to see how the gauges look when finally installed. We can imagine some teething problems with slew rate or update speed, but we’re sure it’s nothing [Wesley] can’t engineer out with a few revisions. Custom gauges are something we’ve seen a few times around these parts; this digital setup is particularly useful for engine data. Video after the break.
The odometer servo is very noisy. Using a small stepper motor with a quiet driver would solve that.
What happens to the gauges when the GPS looses signal? With extra sensors, you can do a bit of dead reckoning for when you go into tunnels and such. Perhaps some fancier GPS modules might have that built in?
Or take a different tack: Do you have a gear indicator from the transmission? Use that with the tach to compute the speed.
Or use both systems, with the GPS providing corrections when available.
I would think the easiest and most accurate solution would just be to put a hall effect sensor + magnet on any part of the drivetrain after the transmission. Isn’t that what speedometers/odometers in modern cars use?
I agree GPS has a lot of cool uses but not the most practical for this application – takes time to lock on, accuracy is greatly reduced by buildings, terrain, foliage, etc. Plus the GPS antenna has to be mounted with clear view of sky/not blocked by metal body paneling.
It’s totes adorbs that you think Corvettes have metal bodies. A 12 cylinder Vette is an abomination as is eveything that comes along with it.
As many have said, not a fan of relying only on GPS.
That said, with a sensor either measuring the driveshaft or measuring a wheel pair ghetto ABS style and approximating their combined value would be a great way, while keeping GPS for occasional calibration.
Many modern cars don’t even have a speedo sensor, instead they rely on the sum of all ABS wheel sensors, with failsafe for signal errors or outright sensor loss.
As a 20 year GM Dealer hack a hall effect sensor setup is the absolute proper way to go. A little math and some amazon shipments later you are set. Hope he knows hith mafs.
I planned to replace the cable only with a motor that rotates just like the cable would, so i don’t need to modify the gauge. There’s some cheap and simple Honda sensors in Ali (for example) that i’m planning to use. I haven’t yet tried to figure out the mechanical side of attaching the Honda sensor to the TH-400 (or other friend’s transmissions), but we’ll see, maybe.
With a GM TH-350, TH-400, or 700-R4 the tailshaft housing can be take off and a mechanical drive speedometer gear installed. Then get one of the mechanical drive pieces that goes into the side of the housing. Easiest is from a 1990’s police Caprice because it had both the electronic sensor for the computer and speedometer and the mechanical drive for the connection to the device that subtracted the cop car’s speed from the RADAR signal when moving. If you can’t find one of those, Jags That Run has speed sensors that screw onto the mechanical speedometer drive on the transmission.
What year did the Caprices and Roadmaster go OBD-2 ? I think it was earlier than mandatory, like ’94??? I think that’s when they went all electronic, so maybe manual drive before that. Unless GMs OBD-1 computers needed it earlier. IDK, I try not to play with the General, too many sharp edges LOL
*mechanical not manual (LOL hand cranked speedo)
He was running the odometer at the full speed of the servo, in use where it should be slowed down to match the speed of the vehicle I doubt it’ll be nearly as noisy.
I like how you are thinking, I have 2 points of order:
How will you hear this servo over a V12?
What makes you think the V12 won’t accelerate this fast?
(Is this the same guy who made a 50s style indy car out of a boxster and is putting ‘diy freevalve’ on a miata?)
I do appreciate the effort to maintain the heritage car’s aesthetic and styling. A chunk of the old car collector populations are “purists” and wiil only put parts in their car that were available when the car was made (or direct replicas) of those parts. Me personally, I think there’s nothing wrong with taking a beautiful machine and updating it with newer technologies that improve performance, reliability, comfort, etc. – AS LONG AS the car’s original beauty/styling/essence is preserved.
Example, for a classic car
NOT OK: Putting in an in-dash GPS car stereo with 7″ touchscreen
OK: Gutting the stock radio but tapping into the volume knob, which is interfaced to a modern speaker amp mounted out of site, and using an also hidden BT receiver or hidden AUX cord for audio source.
I also like the kits that add power windows to vintage cars while 100% preserving the look and feel of the old school manual roll up windows. The window hand crank is left in place, but instead of being a mechanical drive component, it becomes an electrical switch that triggers the window motors to raise or lower the windows. This type of implementation is awesome because you still INTERFACE with the car the original, classic way. You go to “roll the window down” the original way except you only have to rotate the crank a couple degrees and the motor does the rest, rather than having to make a couple full revolutions with the crank to fully lower the window. Plus no adding of window buttons that would reduce the car’s vintage look.
What if you design a GPS with a curved glass screen so it looks like a CRT?
Well this is how they would have designed them in 1964…
https://www.thecinetourist.net/maps-in-films/124-goldfinger-guy-hamilton-1964
I would argue that the tech contemplated there would have been maps on microfilm, back projected and indexed somehow for relative position, and dots/markers independently projected.
Doesn’t every gearbox have a drive gear on the output shaft and a port for the speedometer cable? It can’t be too hard to find the cable and read the turns with an encoder.
By about 1990 the majority of cars had electronic speedometers of one form or another. They’re pretty common even before that. 1980 was about the end of guaranteed mechanical speedometer drive available on the transmission.
1988 Chevrolet pickup had tail shaft socket for cable to speedo. In socket was a gear & PM generator for pulse output to speedometer. My 2 less old trucks have later versions of same for same purpose, mounted on rear housings of transfer cases in 4WD systems.
Replace the odo with a small eInk display – Inverse it would look almost identical to the stock counter….
I wonder why they didn’t use a stepper just like GM does now, they’re cheap and are made to do the ~300 or so degrees of rotation… without noise.
To those asking why GPS and everything, GPS speedometers are already a very reliable commercial technology. They are probably better and more accurate in every way and are used for performance cars mostly.
as evidenced by SSC 331 mph top speed record!!1 ;-)
Would it be easier to digitize the tachometer and speedometer shaft output with magnets and hall-effect sensors (or similar) and convert the pulses to drive a dashboard stepper motor adapted to fit in the existing gauge? Gee I’ll bet aftermarket stepper gauges already exist for this vintage car in the first place. Dashboard gauge stepper motors are inexpensive and fairly reliable. Example:
https://www.amazon.com/Dr-Roc-Instrument-Cluster-Stepper-Backlight/dp/B01B782OFC
This tutorial shows how to drive a dashboard gauge stepper with an Arduino (an ATmega328 is over-kill, a cheap ATtinyXX or even cheaper 8051 clone will do):
https://arduining.com/2012/04/22/arduino-driving-a-micro-stepper-motor/
Or maybe the gauges driven this way would drift over time? The dashboard steppers are relative, not absolute and there is no feedback it seems. How do existing dashboard steppers work on modern production vehicles? I can see the dashboard controller(s) resetting to zero when the vehicle comes to a stop. But if you are driving for many hours at speed, won’t the steppers drift? Maybe the “steppers” are actually BLDC motors driven by PWM after integrating the shaft pulses?