How do I guestimate MPH at PTO speed rather than engine rated speed?

[sixdogs]

I need to know my forward MPH travel speed with the PTO at 540 RPM to spread fertilizer. Problem is, Kubota (and probably all) list MPH travel speed in the owner's manual at the engine rated speed and that can often be several hundred RPM faster than the speed at 540 PTO. So, if I used those charts I would be going slower than I think and putting down the wrong amounts of fertilizer.

For example, a Kubota I have has a 540 PTO engine speed at 2295 RPM but the engine is rated at 2600 RPM and that's the MPH speed listed in the owner's manual. At 2600 RPM in 5th gear, it's going 6.5 MPH. But at the 2295 RPM and 540 PTO I think is going only 4.9 MPH. Now, I have a Kubota with the electronic dash that shows the RPM and speeds together but those tractors are too big for this use. So, does anyone know if Kubota has MPH speeds listed that show forward travel at PTO speed as opposed to just rated engine speed?

Any ideas?

 

[Jchonline]

If you have a phone with GPS and app capability there are many apps that will give you a speed. Just have it running while you are moving!

I use Gaia GPS, there are many others. Motion X, etc etc.

 

[sixdogs]

If you have a phone with GPS and app capability there are many apps that will give you a speed. Just have it running while you are moving!

I use Gaia GPS, there are many others. Motion X, etc etc.

Should have stated I use a basic phone. Any less would be broken in 15 minutes.

 

[Katahdin]

Basic GPS Speedometers exist. Prices start at $30 on Amazon.

 

[atitus74]

old school approach works. if you have one of those wheeled pedometers, or just a tape, mark off a fixed distance say 50 feet or so. Get up to speed ahead of the markings and then time yourself with your watch, stopwatch whatever see how many seconds it takes to go the 50 feet, then you can do the math to figure out MPH. 1 foot per second is 0.681818 mph.

 

[jmc]

In your example, it would be 2295/2600 times 6.5=5.74 MPH

That would be for a geared drivetrain all the way back. An HST tranny might throw in a wildcard.

 

[MossRoad]

The OP says he has gears.

 

[4570Man]

You could use a phone GPS which you don’t have. You could have a helper count the RPM of the tires and measure the rolling distance of the tire or you could time how long it takes to travel a given distance.

 

[Zebrafive]

In your example, it would be 2295/2600 times 6.5=5.74 MPH

That would be for a geared drivetrain all the way back. An HST tranny might throw in a wildcard.

Simple math as you stated. I agree with your formula.

 

[sixdogs]

In your example, it would be 2295/2600 times 6.5=5.74 MPH

That would be for a geared drivetrain all the way back. An HST tranny might throw in a wildcard.

Simple math as you stated. I agree with your formula.

I don't think that is correct. Before seeking advice here, I tried to guess by comparing to a known speed in a digital dash tractor. The simple math thing didn't work. Also, I need different speeds for different applications so speeds will change. Surely there's a Kubota chart around?