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Old 30-01-2013, 13:10   #1
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Adjusting ARS-5 to Correct Revs on Perkins 4-236

Perkins 4-236 with Amptec small case, to Balmar ARS-5 reg to VDO tach (I think).
Tach is indicating double the measured crank RPM.
Tach is set for 4 cylinder. (4,6, 8, and 12xxx on the back of the tach)
Cant find any info on the alternator. 12 or 14 pole?
Balmar info says consult tach builder. No response.
Thanks
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Old 30-01-2013, 22:28   #2
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Re: Adjusting ARS-5 to Correct Revs on Perkins 4-236

Can't help you directly with that tach. If it is reading twice the rpm then I would suspect that changing the tach to 8 cyl and see what happens.

I'm assuming that you are using some kind of external RPM meter....

On my 4-236 with a balmer 100 amp and 612 reg I used an external rpm meter to set the engine to 1000 rpm. I have a motorola Tach so I was able to adjust the pot through a hole in the back of the tach to read 1000. I checked it at other rpms and tweaked it to get accuracy at 80% WOT and close enough at other rpms.

Regards
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Old 31-01-2013, 04:29   #3
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Re: Adjusting ARS-5 to Correct Revs on Perkins 4-236

For consistancy sake. I wired thru the ARS-5 tach input and output terminals to the tach.
I'll try alternator straight to tach and see if there is difference.
Owner gives me info about previous set-up which leads me to believe that tach was not accurate inold install.
Further confounded by finding the old set-up had the tach on the 6 cyl. setting. Scratching head on this one.
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Old 31-01-2013, 06:13   #4
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Re: Adjusting ARS-5 to Correct Revs on Perkins 4-236

I doubt you'll see any difference wiring straight through (except when you have no reading on the tach with a full battery, possibly). The adjustment should be on the tach side. I've found various VDO tach manuals via Google.
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Old 31-01-2013, 09:47   #5
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Re: Adjusting ARS-5 to Correct Revs on Perkins 4-236

Thanks Paul.
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Old 31-01-2013, 10:17   #6
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Re: Adjusting ARS-5 to Correct Revs on Perkins 4-236

Quote:
Originally Posted by Blue Stocking View Post
For consistancy sake. I wired thru the ARS-5 tach input and output terminals to the tach.
I'll try alternator straight to tach and see if there is difference.
Owner gives me info about previous set-up which leads me to believe that tach was not accurate inold install.
Further confounded by finding the old set-up had the tach on the 6 cyl. setting. Scratching head on this one.
Blue...

I think you're going to find that this tac will never work properly.

The tac marked by 4cyl, 6 cyl..... means its a tac for a gas engine, and it's pick-up is from the coil, and pulses are counted each time the points in the distributor open.

An alternator tac is based on the pole count of the alternator ie: hz signal.

Lloyd
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Old 31-01-2013, 11:14   #7
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Re: Adjusting ARS-5 to Correct Revs on Perkins 4-236

Lloyd, had that thought myself, --but, it is the original perkins tach that has been there for ten years or so.
Not sure if it ever was accurate,because owner told me he got 6.2knts (GPS) at 1500rpm on a 46ft REALLY heavy motorsailor.
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Old 31-01-2013, 20:28   #8
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Re: Adjusting ARS-5 to Correct Revs on Perkins 4-236

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Lloyd, had that thought myself, --but, it is the original perkins tach that has been there for ten years or so.
Not sure if it ever was accurate,because owner told me he got 6.2knts (GPS) at 1500rpm on a 46ft REALLY heavy motorsailor.
It may or may not be the original tac, as Perkins used a mechanical tac sender.

Al tac signals are AC Pulse, either generated from, a small ac alternator aka; diesel tac sender, a charging alternator phase signal, or as in gas engines the point closure.

A gas tac sees the pulse from the points closing, 4 cylinder = 4 pulses per revolution, 6 cyl. = 6 pulses per rev, 8 cyl. etc...

A diesel tac is typically driven from a shaft either cam, fuel pump, sometimes crank shaft, depending on where, it has relationship to the crank and the gear ratio of the driver.

A Charging Alternator tac is dependant on the number of poles devided by 3, bc alternators are 3 phase, then a crank pulley to alternator pulley ratio.

To determine the signal rate take a multimeter with the abilty to measure Hz, and with the engine running, at a speed determined by a laser tac W/MAG PU, devide the reulst and you will know the ratio of output of the signal to actual RPM's.

Lloyd
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Old 01-02-2013, 00:42   #9
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Re: Adjusting ARS-5 to Correct Revs on Perkins 4-236

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Originally Posted by FlyingCloud1937 View Post
It may or may not be the original tac, as Perkins used a mechanical tac sender.

Al tac signals are AC Pulse, either generated from, a small ac alternator aka; diesel tac sender, a charging alternator phase signal, or as in gas engines the point closure.

A gas tac sees the pulse from the points closing, 4 cylinder = 4 pulses per revolution, 6 cyl. = 6 pulses per rev, 8 cyl. etc...

A diesel tac is typically driven from a shaft either cam, fuel pump, sometimes crank shaft, depending on where, it has relationship to the crank and the gear ratio of the driver.

A Charging Alternator tac is dependant on the number of poles devided by 3, bc alternators are 3 phase, then a crank pulley to alternator pulley ratio.

To determine the signal rate take a multimeter with the abilty to measure Hz, and with the engine running, at a speed determined by a laser tac W/MAG PU, devide the reulst and you will know the ratio of output of the signal to actual RPM's.

Lloyd
That would...be.

"the results"...


seems I am going to have get a new editor... or just learn how to proof read.

Sh.t, I don't know.

hope I'm helping

L
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