Measuring/calculating PTO speed (not PTO speed = Machine speed / implement speed)

[ruffdog]

Like this?..


View attachment 783595

This is an old one made by Warner Instrument Co in Beloit WI

 

[OldNick]

It's very common for these smaller Japanese tractors to have 4 PTO speeds. Something like 540 - 750 - 860 - 1000. All achieved at the rated RPM, probably in the 2500 engine RPM range like Ruffdog says.

It's also common to use the 750 RPM with less engine RPM to achieve 540 PTO RPM with less engine RPM, also known as 540E (E for economy).

Ahah! OK, thanks for that. Sounds like all this theory is overthink. If I had not found out about it, I would have just experimented until it sounded and felt right. Back in my younger days that's what I used to do.

 

[OldNick]

It should be noted that running a higher pto gear at a lower engine speed will greatly reduce available HP.

And even more so, reduce torque for the implement. But that's where you drop the _tractor_ gear and just move slower.

 

[Tinhack]

I went ahead and added a 12v digital tach even though the new dash has a tach. I wanted to verify the accuracy since my tach is driven by a cable. Come to find out. it's spot on. The push-on/push-off switch and the box are waterproof as is the sender. The sleeve on the output shaft has a magnet and set screw.

 

[zzvyb6]

A 6 spline shaft at 540 rpm would generate 3240 square wave beats per second if it made contact with a flexible strip. Remember clamping playing cards to your bike wheels ?
Then ask Google to play you a 3240 Hz. tone on your phone and compare the 2 tones. Adjust the throttle accordingly in any of the transmission selectors. The tone is actually played on a youtube clip loaded with your specified frequency. Try it ! Even though the generated tone is a sine wave, you can't miss the hook up (well yas you can if you're DEAF, but that would kill the mood). As you get close to a match, you might hear a beat frequency as the difference between the two signals. Ignore any sharks that might appear in the area....

 

[OldNick]

A 6 spline shaft at 540 rpm would generate 3240 square wave beats per second if it made contact with a flexible strip. Remember clamping playing cards to your bike wheels ?
Then ask Google to play you a 3240 Hz. tone on your phone and compare the 2 tones. Adjust the throttle accordingly in any of the transmission selectors. The tone is actually played on a youtube clip loaded with your specified frequency. Try it ! Even though the generated tone is a sine wave, you can't miss the hook up (well yas you can if you're DEAF, but that would kill the mood). As you get close to a match, you might hear a beat frequency as the difference between the two signals. Ignore any sharks that might appear in the area....

Thanks for that idea. It is good. There are actually a couple of sites ... Online Tone Generator - Free, Simple and Easy to Use....for instance. Does all the standard wave forms.

However I have other jobs for a tacho, where doing that trick would be a lot harder..a saw blade for instance

I think I will go for the laser. Fleabay has them for Aud $20, post free.

There is no real urgency. The weather here in Perth is VERY hot and dry ATM. This is about a flail mower and I am not about the rip around with steel being passed through the grass and small stones!

 

[zzvyb6]

I had a PTO alternator to power the house & barn for which getting 60 Hz from the A/C output was needed. I used a Kill-A Watt device that plugs into the genny outlet to measure the frequency of the output voltage. This verified my 540 pto Tach indicator. The Kill-A-Watts are available here in most hardware stores and fleabay/Amazon etc. $20.

 

[CobyRupert]

Thinking outside the box, would this works using a standard 60hz incandescent light?

Find where 600 PTO rpm is (because it works well with 60 sec/min and 60 cycles/sec.) as follows:

The PTO shaft turning 600 rpm, means 10rev/sec. The PTO shaft has 6 splines. At 10 revs per sec, that means 60 splines pass by per second.

An incandescent light operating at 120v/ 60 hertz flashes 60 times per second. That means, the splines will look like there not moving when PTO is at exactly 600rpm. (“Strobe effect”.)

Once you know engine rpm for 600 PTO rpm, multiple that by .9 for 540 PTO rpm engine setting.

The problem, you might also observe “stand still” strobe effects at 15, 30, 60, 120, splines/sec, (150, 300, 600, 1200 rpms, maybe others?), so you have to know you’re operating in the right ballpark when looking for the 600 rpm strobe effect.

Suuuuuure, that’ll work…..in theory!

 

[ning]

Thinking outside the box, would this works using a standard 60hz incandescent light?

Find where 600 PTO rpm is (because it works well with 60 sec/min and 60 cycles/sec.) as follows:

The PTO shaft turning 600 rpm, means 10rev/sec. The PTO shaft has 6 splines. At 10 revs per sec, that means 60 splines pass by per second.

An incandescent light operating at 120v/ 60 hertz flashes 60 times per second. That means, the splines will look like there not moving when PTO is at exactly 600rpm. (“Strobe effect”.)

Once you know engine rpm for 600 PTO rpm, multiple that by .9 for 540 PTO rpm engine setting.

The problem, you might also observe “stand still” strobe effects at 15, 30, 60, 120, splines/sec, (150, 300, 600, 1200 rpms, maybe others?), so you have to know you’re operating in the right ballpark when looking for the 600 rpm strobe effect.

Suuuuuure, that’ll work…..in theory!

Incandescent lighting doesn't really flash, because the filament itself is incandescent, and it doesn't markedly change temperature/light output during the brief interruption of power.

Fluorescent lighting does flicker with the cycling, and many people can see the flickering at 60Hz. You'd be better off using a fluorescent.

 

[dieselscout80]

Well I certainly do not want to run my engine at 2500! Anyway does that have anything to do with a 4-speed PTO, or refer to my question?

Why not????

Tractors are designed to run at rated power & rpm all day long everyday for many thousands of hours.

PTO operated equipment is designed to be run at a set speed typically 540 or 1000 rpm for most North American tractors. Run at lower speeds may not operate effectively, but some do okay at lower speeds.