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modirt 
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Joined: 18 Jul 2018
Location: Missouri
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 Posted: 19 Sep 2025 at 7:51am |
That is a really good resource I wasn't aware of. This one might work........
That assumes 17mm is same as 0.625 diameter shaft on alternator. The math isn't exact, but close. Frustrating that they have to mix apples and oranges (SAE and metric) to to make it more confusing.
Past that........the plot thickens........meaning my education on all this continues. This from Powermaster (whose material is both excellent and abysmal).........
Edit: Measured and it's 6.25" / 2.65 = 2.358 (better than I feared, but still not good)
I'll have to measure, but my guess is OD of big pulley is no more than 5 inches.....turning a pulley of about 2 3/4"......so ratio is not much more than 2:1. At engine RPM of 1,000 fast idle speed, even this high amp alternator is not putting out much juice. Even in use in the field, engine rarely exceeds 2,000 RPM's. Documentation that came with alternator shows it tested to 65 amps at idle speed, but that was with 3:1 ratio. At my idle speed, may not be doing much at all.
So a lot of this then goes to operation. If working at night and are moving from field to barn.......and back........best let the engine rev......(do not shift up)......to get RPM's to 2,500 or more for as long as you can. Alternator really isn't doing much unless you do.
All part of the puzzle.
Edited by modirt - 19 Sep 2025 at 8:48am
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modirt
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Joined: 18 Jul 2018
Location: Missouri
Points: 8776
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Posted: 19 Sep 2025 at 8:58am |
Just got off phone with Powermaster tech support. Long story short, belts as now configured are good to go.
As per those guys, they don't have a 1/2" groove pulley for this alternator. Running high on those grooves at low speed not going to hurt anything. Pulley has OD of 2.65", so is faster than what I can replace it with, which BTW, the pulley is held on by some strange screw setup......maybe along the lines of a tamper proof setup. Not the nut and torque wrench change over some show to use. Best leave it alone.
Alternator kicks in at around 1,800 RPM alternator shaft speed, and comes up to rated speed at around 2,400 RPM, which at my fast idle speed ** will be around 2,400 RPM. Most transit and field work way above that, so should be OK.
** - Fast idle needed when unloading at the barn. Needed to turn the hydraulic pump to get drag chains moving, and is also needed to keep the radiator fan (runs on hydraulic motor) spinning fast to keep cooling system working. Those all speed up and slow down with engine speed. 1,000 RPM is about right.
Edited by modirt - 19 Sep 2025 at 9:07am
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PaulB
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Joined: 12 Sep 2009
Location: Rocky Ridge Md
Points: 5118
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Posted: 19 Sep 2025 at 10:08am |
Be aware that if the belts are not down in the groove where the top of the belt is flush with the pully, you are effectively running a larger diameter pulley. Measure what you get for the OD of the belts around you alternator pulley. Do you have a mechanical tachometer that you can actually measure the alternator RPM ?
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If it was fun to pull in LOW gear, I could have a John Deere.
Real pullers don't have speed limits.
If you can't make it GO... make it SHINY
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modirt
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Location: Missouri
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Posted: 19 Sep 2025 at 10:29am |
Good call.....it may be sitting 1/8" or so proud, so maybe 2 3/4" plus effective diameter of pulley. The one from Brillman better than that, and 1/2" to boot. If I can figure out what "special tools" are needed to make the swap.
No.....do not have a shaft RPM. Just tach on the engine.
But do have an electric meter, so may be able to measure voltages and amps when running to see what I got.
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steve(ill)
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Joined: 11 Sep 2009
Location: illinois
Points: 88041
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Posted: 19 Sep 2025 at 1:09pm |
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alternator output is not linear.. Generator output is relative to SPEED... Alternator might take some RPM to kick in, but after that the output is a curve.. running half speed might get you 75% output..( 1200 engine rpm, 2500 rpm alternator).. they are all a little different, but the main advantage of an alternator is good amp output at lower rpm as compared to a generator. .... once an alternator goes above 3000 rpm the output starts to go flat...
Edited by steve(ill) - 19 Sep 2025 at 1:16pm
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Like them all, but love the "B"s.
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iowallis
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Joined: 04 Jun 2017
Location: North Iowa
Points: 372
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Posted: 19 Sep 2025 at 3:17pm |
 modirt wrote:
Frustrating that they have to mix apples and oranges (SAE and metric) to to make it more confusing.
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And make things simple?? I have done repair work on late 1970s to late 1980s vehicles that are mish-mash of metric and SAE bolts/nuts. There was one manufacture (Chevy?) that 2 out of the 3 starter bolts were metric and the other SAE. Then the Ford 5.4 oil filter, supposedly the engines built in Windsor Canada has SAE threads on the filter and the engine built in Romeo MI (USA) has metric threads.
Sound like you are making much progress on this project, might as well go all the way and restore it to its original, as sold when new, glory.
Edited by iowallis - 19 Sep 2025 at 3:18pm
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Les Kerf
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Joined: 08 May 2020
Location: Idaho
Points: 1323
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Posted: 19 Sep 2025 at 9:09pm |
modirt wrote:
Just got off phone with Powermaster tech support. Long story short, belts as now configured are good to go.
As per those guys, they don't have a 1/2" groove pulley for this alternator. Running high on those grooves at low speed not going to hurt anything. Pulley has OD of 2.65", so is faster than what I can replace it with, which BTW, the pulley is held on by some strange screw setup......maybe along the lines of a tamper proof setup. Not the nut and torque wrench change over some show to use. Best leave it alone.
Alternator kicks in at around 1,800 RPM alternator shaft speed, and comes up to rated speed at around 2,400 RPM, which at my fast idle speed ** will be around 2,400 RPM. Most transit and field work way above that, so should be OK.
** - Fast idle needed when unloading at the barn. Needed to turn the hydraulic pump to get drag chains moving, and is also needed to keep the radiator fan (runs on hydraulic motor) spinning fast to keep cooling system working. Those all speed up and slow down with engine speed. 1,000 RPM is about right.
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It will be just fine. Install a voltmeter if you are concerned (a voltmeter tells you far more than does an ammeter).
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modirt
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Joined: 18 Jul 2018
Location: Missouri
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Posted: 20 Sep 2025 at 7:25am |
When this thing showed up on my doorstep, don't think any gauges were working (along with a lot of other stuff). One of first things I did to start rehab was to install full set of new gauges. Could not stand operating blind.
Might work OK for a lawnmower, but not a big piece of equipment like
this. Hardest part was to find a tachometer.....with hour meter. Those
are not cheap!! All gauges are Auto Meter.......which offers good quality gauges for automotive and marine use.
Watching the volt meter work was how I concluded changes had to be made.
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modirt
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Posted: 20 Sep 2025 at 7:29am |
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As for rest of rehab, once engine is running again with no issues, plan it is to drive it to local welding/fabrication shop for a few welding projects, then start working on getting it painted. Not the full deal, but the visible sheet metal. 50 to 60 years of sitting outside in the weather takes it's toll.
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Les Kerf
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Joined: 08 May 2020
Location: Idaho
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Posted: 20 Sep 2025 at 8:09am |
modirt wrote:
When this thing showed up on my doorstep, don't think any gauges were working (along with a lot of other stuff). One of first things I did to start rehab was to install full set of new gauges. Could not stand operating blind.
Might work OK for a lawnmower, but not a big piece of equipment like
this. Hardest part was to find a tachometer.....with hour meter. Those
are not cheap!! All gauges are Auto Meter.......which offers good quality gauges for automotive and marine use.
Watching the volt meter work was how I concluded changes had to be made.
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Was this photo taken while running the new alternator? I like to check the voltage with my Fluke 88 meter to verify the calibration of the dash gauge; a full 14 Volts makes me happy  |
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modirt
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Posted: 20 Sep 2025 at 8:26am |
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Yes, but as indicated, was only running slightly over 1,000 engine RPM's. Documentation that came with new alternator says it is set to 14.2 volts charging when operating at "normal" speed. I'm guessing that will be around 2,000 RPM's plus. So far, I've not done more than idle as since it all went back together, has been running hot. I'm thinking thermostat may now be stuck closed having sat dry for past 2 months or so. Either than or water pump went bad just sitting. Have another new issue with an exhaust manifold that has showed up. Need to get that sorted too...........then can take it out on the road for a joy ride to see what happens.
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