So I won this on eBay! From everything I can tell I think it's pre-1920, and as such will be period correct as a tach on my speedster. Granted, I'm going to have to engineer some things in order to make it work.
Here's what I'm thinking, and would like input as to what might not work like I'm thinking.
The threads to the head unit are 13/16-16, I'm thinking a thread adapter into the head unit and then this:
And then I can attach a Stewart Warner cable housing and cable, which are available from Lang's. I'll attach the other end to a pulley supported by my alternator bracket. The pulley will be the same diameter as my crank pulley, giving me 1 to 1, and will just be a simple single groove run by a belt from a vacuum cleaner brush.
The good part is that the direction of rotation doesn't matter. The tach works fine either way.
Seth, can you come off the front of the alternator? A double pulley or drill and tap the shaft. I have seen tachometers run off the back of a Model T generator by drilling and tapping the shaft and attaching the cable directly to the generator shaft. First thing you need to determine is the required input speed to the tach. Put a battery powered drill to the tach. See what speed it registers at maximum drill speed which you know. You may need to speed up or slow down the input speed for the tach to read the correct speed. Good luck.
I'll double check it, but the tach has a nicely stamped "1 to 1" on the back. My serpentine belt doesn't use all of the grooves in the alternator's pulley, so I was going to use one of those. But that's why I need the tach pulley to be the same diameter as the crank pulley, to get 1 to 1.
Holy crap, that's beautiful.
Seth, I think you can still get those adapters in other ratio's. Dave in Bellingham, WA
I need the ratio to just be 1 to 1. It's super easy and simple, if I get something turning same speed as crankshaft then I'm good to go. Pulley should turn crankshaft speed, and then cable and ultimately the head unit. I've tested it on the drill.
Hi Seth: I love this subject, that I struggled with for a couple of years. For everyone interested, the first step should indeed be to verify the required input ratio to the tachometer. I believe most manufacturers chose to go 2:1 driving the tachometer at camshaft speed for the internal gearing of the tachometer could run at half the speed -(less wear) -that would be involved if they had decided on 1:1.If yours is indeed stamped 1:1 OK! My Stewart-Warner, early 20's vintage unit that I was able to "shoehorn" into a brass 1912 speedometer case, to match my speedo, is in fact 2:1.Making up my own drive system back in 2013, I found a suitable angle drive and proceeded to mount it on the front end of the commutator- being driven directly from the end of the camshaft. To my disappointment, I found the resulting tachometer readings to be at 1/2 the actual engine RPM! I had assumed the unmarked angle drive to be a 1:1 ratio and I had foolishly neglected to verify this important characteristic prior to doing all the work! Some months later, back to the drawing board. This time I correctly used the same angle drive while installing a suitable drive from the front of the crankshaft with the serpentine belt that also drives my 65 amp (Geo Metro) alternator. Obviously I use the same 3" diameter pulley for the tachometer drive as I have installed on the crankshaft. I'll include a few photos for clarification, as well as my latest upgrade to a modern VDO Fuel Gauge c/w built in Low Fuel Warning light! Just love the challenge! Tom
Seth in A. What you have is a Tachometer that measure the RPM of an Engine or a shaft. In the old days we used that to know what the exact RPM of our Threshingmchine was .
The gear driven generator and alternator runs at 50% faster than the motor. Then when the engine is at 1000rpm, the camshaft is at 500rpm and the generator at 1500rpm