400 gas 12v alternator with tach drive

jim_uny · Oct 27, 2012

have a 12v delco 10si without tach drive. how can i adapt it so tach will work. is there a tach that works on electric or do i have to buy a rebuildable core alt with tach drive option ?

Janicholson · Oct 27, 2012

To the best of my knowledge there are no tach drive alternators (at least there are sure none used on X00 series Farmalls). the tach is driven from the distributor drive housing (very similar to the cable drive on a speedometer on a car. Electronic tachometers using a sample of coil primary pulses to operate are commonly available in many sizes. I would choose that option unless you are making a restoration that needs to be stock. (which you are evidently not doing) Jim

Hayfarmer · Oct 27, 2012

most electric tachs go from 0 to 8000 or more. I purchased one for my SMTA this year from NAPA, ordered in that has a range of 0 to 4000. Works much better on tractors as easier to read with lower RPMs. Believe the brand was VCO

jim_uny · Oct 27, 2012

i have philco distributor with electronic ignition upgrade without mechanical tach drive.
my distributor base has a plate with two holes. took it off and is solid. cant put tach drive.

Owen Aaland · Oct 27, 2012

(quoted from post at 10:32:20 10/27/12) have a 12v delco 10si without tach drive. how can i adapt it so tach will work. is there a tach that works on electric or do i have to buy a rebuildable core alt with tach drive option ?

I have seen tach drives off the end of generators but I don't recall seeing any on 10SI alternators. I think there was a 10DN that had a tach drive and some Motorola units also have them.

The tach drive on a 10SI is the third plug-in terminal that is available on some units. As far as I know IH did not use that option for a tach though other manufacturers did. The third terminal is a stator lead that gives you 21 full wave cycles per revolution. The rotor has 7 negative poles and 7 positive poles rotating inside a stator with three separate coil windings. Each stator winding produces 7 full wave cycles per revolution offset from each other by 1/3 of a cycle.

Dividing the alternator cycle peaks per minute by 21 will give you the alternator rpm. Figure out the rpm ratio between the crankshaft and the alternator and use that ration to determine the crankshaft speed.

Anonymous-0 · Oct 28, 2012

allis Chalmers used a delco alt with a tack drive. I know they were on the 185,190x and 200s
Probable more models.

rhtx55 · Oct 28, 2012

Factory tach drives on the hundred series were made by Stewart Warner, they had a different distributor drive base that was furnished to drive the gear driven cable that ran back to the tach head on the dash.
Only the diesel versions of the 350 & 450 had the tach drive on the back of the generator.

Owen Aaland · Oct 29, 2012

(quoted from post at 07:07:35 10/28/12) allis Chalmers used a delco alt with a tack drive. I know they were on the 185,190x and 200s
Probable more models.

I'm pretty sure the alternators Allis Chalmers used were Delco 10DN series.

400 gas 12v alternator with tach drive

jim_uny

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Janicholson

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Hayfarmer

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jim_uny

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Owen Aaland

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rhtx55

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