Generator to Alternator Incorrect RPM's

Jim Bellamy

New User
I converted my 3000 Ford from a generator to a Delco 10si alternator with a mechanical tach drive. I have verified with a hand held photo tachometer that the PTO is running at 540 rpm's while the engine is running at 1800 rpm's. Which is as it should be but the tach reads 2300 rpm's. Has anyone else had this problem and if so what did you do to fix it?
 
Dieseltech is correct however in addition to same diameter pulley as your generator you have to make sure it is the same groove depth otherwise the belt will ride at a
different height just as though the pulley was a different diameter.
 

Thanks for the response. I have considered both of those solutions but it should work as is. I contacted Yesterday's Tractor on Friday and they are getting with the manufacture for a possible solution. They suggested in the meantime I post it to the forum to see if this has been an issue for anyone else.
 

I have the same issues with both of my conversions, I had the original Lucas generator pulley bored to fit a Delco which helped. It now shows 2100 rpm at pto speed instead of 2300 but the only pulley I can find thats larger in dia is one of those 5" race car pulley's, I'm afraid if I slow the alternator down that much it won't have good output, I have extra work lights on some of my tractors for night work, with all lights on and the Lucas pulley the gen light has a dim glow at night, if I rev the engine past pto speed the light goes out. This leads me to believe I'm right on the edge of the alternators capability at pto speed.
The solution is the proper gear reducer on the back of the alternator if one was ever made, these conversion alternators remind me of the ones used on Massey's back in the day.
 
Perhaps the gear drive at the rear of the alternator has a slightly different gear ratio than the gear drive at the rear of the original generator?
 
Same issue as you

Figured out the tach was showing 2200 rpm instead of 1900 when the pto was turning 540, so that's where I run it
when using a pto implement.

It was several years ago when I made the alternator conversion. Annoying at first, I'm used to it now.

Fred
 
(quoted from post at 22:14:14 11/04/18) Same issue as you

Figured out the tach was showing 2200 rpm instead of 1900 when the pto was turning 540, so that's where I run it
when using a pto implement.

It was several years ago when I made the alternator conversion. Annoying at first, I'm used to it now.

Fred
aybe just as simple as a little yellow stick note that says 2300 indicated is actually 1800. Cheap, too. As Honda used to say, KISS! :)
 
(quoted from post at 15:16:01 11/04/18) Perhaps the gear drive at the rear of the alternator has a slightly different gear ratio than the gear drive at the rear of the original generator?

It has to be. The v and the diameter matches the pulley on the generator. The tach was correct with the generator. That only leaves the gear drive.
 
(quoted from post at 16:28:55 11/04/18) If my math is right a 4 1/2 inch pulley would get you close.

I hope your math is right.... I came up with the same size pulley as you and it should run the tach at 1791 rpms.
 
I want to thank everyone for their responses. I will wait to see what (if anything) the manufacturer is going to do. Then I will change to a 4 1/2" pulley.

It's a sad thing that you buy something that should be made and tested for your model tractor and then have to modify it to make it work.

I will update this post to let you know how the pulley works if the manufacture can't provide me with the correct ratio gear drive.
 
(quoted from post at 08:19:53 11/05/18) I want to thank everyone for their responses. I will wait to see what (if anything) the manufacturer is going to do. Then I will change to a 4 1/2" pulley.

It's a sad thing that you buy something that should be made and tested for your model tractor and then have to modify it to make it work.

I will update this post to let you know how the pulley works if the manufacture can't provide me with the correct ratio gear drive.
do feel your pain, but more times than not, whenever we use non-OEM parts we run into some 'file to fit, paint to match' work that we don't want & didn't expect. :(
 

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