Mechanical Tach Driven from Alternator or Generator?
- Thread starter Jay Ess
- Start date
Kevin in NJ
Well-known member
The alt can drive a tach electrically, but I doubt it does much good as I bet it slips a lot.
Look up boat tachs driven by alternator.
Look up boat tachs driven by alternator.
Jay Ess
Member
Hi Kevin. The alternator has a mechanical gear driven adapter on the rear of the unit. The black object in my original post is another type of drive that attaches to an alternator. Regarding slippage, If they work on a tractor I would guess the performance would similarly acceptable on an A.
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Tom Wesenberg
Well-known member
The degrees of belt wrap is small at the alternator pulley, and to add to that most people use a very small diameter pulley and this gives even less grip, so it can easily slip as Kurt mentioned. If a person wants more amps and a cable driven tach, then I've seen 50's Corvette generators for sale.
If I needed more amps, I'd use a later generator.
If I needed more amps, I'd use a later generator.
Willie Krash
Well-known member
I would think you'd have to size the pulley more so than worry about belt slippage.
Those old Massey's had pretty large dia. pulleys.
I have the formula somewhere at work.
Those old Massey's had pretty large dia. pulleys.
I have the formula somewhere at work.
Kevin in NJ
Well-known member
The alternator has alternating current that is converted to direct current.
The frequency of the alternating current is directly proportional to the RPM. So if you tap off before a single diode you will have an 'electronic tach'. Some alternators have a tap already from what I gather.
Boat Tach
The frequency is dependent on how many 'circuits or phases' in the alternator. I think the common car has 3. Next you count the crossings or average the current coming out of the tap. You now have a tach without the mechanical drag.
FWIW as I have pointed out before. The smaller diameter shaft of the alt used on the A is apparently not capable of transferring the full amount of energy to get the full output of the common alt. This can be looked up online. More than one site has the amount of HP that can be transferred depending on the size of the pulley. Other sites tell you the amount of HP needed for a given amperage output from the alt. As I recall, the 60 amp alt needs over 1 HP for full output. The diameter pulley on the A can only transmit a small fraction of a HP.
There are also some details about having a fairly tight belt and so on. I just know that when all the alt installations have the belt so loose that alt moves easy by my pinky finger that there is no way you are getting much out of the alt. So why bother?
The frequency of the alternating current is directly proportional to the RPM. So if you tap off before a single diode you will have an 'electronic tach'. Some alternators have a tap already from what I gather.
Boat Tach
The frequency is dependent on how many 'circuits or phases' in the alternator. I think the common car has 3. Next you count the crossings or average the current coming out of the tap. You now have a tach without the mechanical drag.
FWIW as I have pointed out before. The smaller diameter shaft of the alt used on the A is apparently not capable of transferring the full amount of energy to get the full output of the common alt. This can be looked up online. More than one site has the amount of HP that can be transferred depending on the size of the pulley. Other sites tell you the amount of HP needed for a given amperage output from the alt. As I recall, the 60 amp alt needs over 1 HP for full output. The diameter pulley on the A can only transmit a small fraction of a HP.
There are also some details about having a fairly tight belt and so on. I just know that when all the alt installations have the belt so loose that alt moves easy by my pinky finger that there is no way you are getting much out of the alt. So why bother?
Jay Ess
Member
As always, great responses and an abundance of knowledge!
I probably should have presented my initial inquiry differently.
I was hoping to run this reverse mechanical tach in my 1930 A and I am looking for a way to drive it.
I was trying to keep it short and sweet and not upset any of the traditionalists. This is not a stock bodied car and as such I was hoping to avoid those who would tell me to go to the HAMB (been there for 9 years), and that this site is for restoration only.
This car is 90% original (mechanically) and has an aluminum boat-tail body. I purchased it as a partially completed project car. While I know it is not historically accurate, I am trying to make it somewhat period correct.
It came with 1990's SW gauges that just look wrong. I have a new rebuilt oval speedometer and an original ammeter that I will be installing in a new dashboard. I plan on covering the tach's odometer with a pewter Ford emblem, and thought this tach would be a good addition to the car.
Any other ideas? Tach drive like on my flathead? Run it off an idler pulley?
I recall someone was going to manufacter a distributor with a mechanical Tach drive for the Model A???
Thanks,
js
I probably should have presented my initial inquiry differently.
I was hoping to run this reverse mechanical tach in my 1930 A and I am looking for a way to drive it.
I was trying to keep it short and sweet and not upset any of the traditionalists. This is not a stock bodied car and as such I was hoping to avoid those who would tell me to go to the HAMB (been there for 9 years), and that this site is for restoration only.
This car is 90% original (mechanically) and has an aluminum boat-tail body. I purchased it as a partially completed project car. While I know it is not historically accurate, I am trying to make it somewhat period correct.
It came with 1990's SW gauges that just look wrong. I have a new rebuilt oval speedometer and an original ammeter that I will be installing in a new dashboard. I plan on covering the tach's odometer with a pewter Ford emblem, and thought this tach would be a good addition to the car.
Any other ideas? Tach drive like on my flathead? Run it off an idler pulley?
I recall someone was going to manufacter a distributor with a mechanical Tach drive for the Model A???
Thanks,
js
