Determing MPH

[dcsobob]

Good afternoon!

Tractor newbie here. Pretty much anything-on-the-farm newbie. I have finally manage to purchase a tractor and I am now entering the lovely world of determining how to properly spray my pastures.

In reading all the instructions on herbicides, fertilizer, etc, i see where sprayer calibration is important. One of the first things I need to determine, and can't, is how fast i'm going in MPH. My tractor (Mahindra 3016 Gear driven) does not have a MPH readout, just RPM. In the manual for hte tractor it gives me a MPH reading for each gear, but fails to tell me what the engine RPM needs to be set at to obtain that speed. so short of staking out a distance on the ground and driving/timing it, is there any trick to determining how fast in MPH i'm going so I can calibrate for my spraying?

Thanks

 

[davrow]

Have you tried a GPS? Your phone or tablet will probably give you a speed reading, too. Calculating it will only get you close (tire size variations, etc.)

Most recent tractors have a mark on the tach to indicate the RPM to hold so the PTO is turning 540 RPM. I would bet your manual uses that same RPM for its MPH calculations. Just a guess, though, and only applies if your tach has that mark.

 

[boggen]

ditto a cell phone, or a cheap GPS / map finder unit. the device may not know were you are going and wondering HUH? but it should give out a MPH.

 

[boggen]

err sctach that, now that i think about it, tire pressure shouldn't matter. just amount of tread on the tire.

 

[Zebrafive]

Got a friend with a 4 wheeler (quad) that has a speedo? Have him follow you and when you signal him , have him note the speed

 

[David_Kb7uns]

Have also heard of using a digital bicycle speedo with magnetic pickup, but not all have tire size calibrations that would work for a tractor wheel or drive shaft.

David Kb7uns

 

[rockinmywaypa]

I used the cell phone to determine how fast my most optimum gear was in mph. I have an app for area and distance which came in handy for determining how big each field was too.

 

[Pete Judd]

For speed over the ground, even the cheapest GPS will give you the speed down to 0.0 MPH. I sailed all over the world using Gps, Loran and even a knot log, just make a log(a notepad), showing the gear that you are in and the rpm and speed over the ground. Save that, and use it forever for that tractor unless you change tire size..

 

[Sportsman762]

The speeds for the Mahindra should be at 540 PTO RPM's.

 

[cycle_gator]

I wish I could remember where I read it, maybe it was in my sprayer instructions, BUT, there is more to it than just ground speed. You must also consider the sprayer pressure. If your sprayer has graduations, fill it with a pre-determined amount of water, just plain water, set the pressure so that you do not get a lot of mist out of the nozzles, run a measured distance in what will be a comfortable spraying speed taking note of gear and RPM. Note the amount of water that goes out of your sprayer over the measured distance. By using the spray width and the lineal length, that will provide square feet which can be converted into acreage then you can determine the application rate per acre, that is what you really want to know, at what speed and at what pressure you are delivering an amount of spray per acre. Most of the sprayer manuals will have a good starting point, especially for the sprayer pressure.

I know this all seems a little trivial, but depending on the type of spray, it can either be totally ineffective, not enough application per acre, or too effective (with a herbicide) and you kill everything, even if all you want to do is knock out the noxious weeds and leave the range grass, or you waste a lot of money by over-applying material. There is some wiggle room in all those calculations, but you will be happier with the results if you are at least close to where you want/need to be on the application rate.