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

[Jchonline]

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

Not so. There are cases for smartphones that make them waterproof, or allow you to drop them from multi story buildings, or run over them with cars. Pretty sure they will ***** your basic phone. I totally get the reason for a basic phone, my aunt still has a flip. She says if you want to contact me you will have to talk to me However, durability isnt one of them.

 

[LD1]

Math is right, and you are correct that you can remember that speed factor for any of your application rates....but dont forget that is ONLY for that gear.

Gear up one or gear down one and there will be a different factor.

But it would be real easy to confirm the 4.09MPH....

Remember this simple number...1.467....

Thats how many feet per second 1 MPH equals....

So 4.09 x 1.467 = 6.0 fps...

Now break out a stop watch and a whatever your method of measurement is...

Mark off 60' and it should take exactly 10 seconds.....or 600' in 100 seconds....or whatever distance you want.

This will confirm your 4.09mph figure and give you piece of mind.

 

[jmc]

Your math seems ok, but
what is "engine rated speed"?

Seems like a meaningless phrase (or only has meaning in these days of sealed fuel pumps). What ever the meaning, it's a pretty useless term. Just look at the confusion it's causing here. Any ground speed chart should be based on (calibrated at) the engine rpm that matches 540 PTO rpm.

Maybe "Rated Speed" is the RPM at maximum HP? I can't even find a "Rated Speed" listed on my spec sheet, which lists about everything else, including HP.

 

[sixdogs]

Your math seems ok, but
what is "engine rated speed"?

Seems like a meaningless phrase (or only has meaning in these days of sealed fuel pumps). What ever the meaning, it's a pretty useless term. Just look at the confusion it's causing here. Any ground speed chart should be based on (calibrated at) the engine rpm that matches 540 PTO rpm.

Rated engine speed is the point at which maximum HP is obtained and I view as a close-to-redline number. More important, it's the RPM that matches the MPH travel speeds shown in the owner's manual. They are not at PTO speed but at rated engine speed. Most people don't know that.

In the old days there was a decal on the fender or a separate ring on the tach that showed the speed range driven in different gears. Of course these days many tractors are digital and you can easily know PTO speed at any RPM number. No problem.

If you are spreading fertilizer commercially with modern PTO spreaders, it's all based on speed at 540 RPM or you run the risk of working for free because of application errors.

 

[sixdogs]

Math is right, and you are correct that you can remember that speed factor for any of your application rates....but dont forget that is ONLY for that gear.

Gear up one or gear down one and there will be a different factor.

But it would be real easy to confirm the 4.09MPH....

Remember this simple number...1.467....

Thats how many feet per second 1 MPH equals....

So 4.09 x 1.467 = 6.0 fps...

Now break out a stop watch and a whatever your method of measurement is...

Mark off 60' and it should take exactly 10 seconds.....or 600' in 100 seconds....or whatever distance you want.

This will confirm your 4.09mph figure and give you piece of mind.

Why would I need a different "factor" for a different gear?. The final drive to the rear wheels would still be 1.00, right?

If I went to the next gear, and lets just say it's 5.2 MPH, I should just multiply that by the factor (PTO engine speed divided by rated speed) times the MPH speed shown at rated RPM for the 5.2 MPH, right?

 

[LD1]

You are correct. The ratio of rated speed vs PTO speed won't change.

 

[sixdogs]

You are correct. The ratio of rated speed vs PTO speed won't change.

Small point here but on your MX5100 the PTO speed and rated engine speed are the same. Both at 2700 RPM. I have one too so, other than your engine event, we're livin' the dream. Glad it's all fixed.

 

[LD1]

Small point here but on your MX5100 the PTO speed and rated engine speed are the same. Both at 2700 RPM. I have one too so, other than your engine event, we're livin' the dream. Glad it's all fixed.

Mine is a HST MX5100....and I dont recall the PTO speed being the same as rated speed.

Maybe it is?? But I was thinking my PTO speed is somewhere closer to 2400-2500rpm....and dont know what "rated" speed is but it will wind to 2900rpm max.

But either case....accurate ground speed based off only RPM is impossible with a HST.

 

[LD1]

Mine is a HST MX5100....and I dont recall the PTO speed being the same as rated speed.

Maybe it is?? But I was thinking my PTO speed is somewhere closer to 2400-2500rpm....and dont know what "rated" speed is but it will wind to 2900rpm max.

But either case....accurate ground speed based off only RPM is impossible with a HST.

Found an old pic with my dash in it....you are right...2700rpm is PTO speed.....but thats still 200PRM lower than max as it goes to 2900.

So I guess that begs the question....what is "rated" speed.

I have been assuming that the 7.3MPH in M range was WOT and not bogging down.....maybe its not? Maybe it can actually go 7.85 in M range. And maybe it can actually go 17.3 WOT in high range as opposed to the 16.1 claimed???

Not that it really matters though

 

[sixdogs]

LD1--I have a gear tractor so I'm not sure on some of the issues. For the MPH speed in H at 540 PTO RPM you could just look in the owner's manual. Beyond that, I don't know since mine is a gear tractor.

On the engine rated RPM speed, I always presumed that was the maximum point of power for the engine and it stuck in my mind as a max RPM point. Maybe not redline but a start to be careful point. On max output of power that could be in torque or whatever but I don't know. MHHarry would know but he's not here. Not sure I would go to 2900 RPM without someone more informed than me. It's a guess but I don't think you gain anything from 2700 to 2900 RPM.