Ground speed question

Drafthauler · Apr 16, 2013

I have a Jinma 284 that I am wanting to use with a new(to me) pasture spray rig. I need to know what my ground speed is in order to calculate the dosage of chemical per acre. The jinma tach has a speed scale on it in kilometers per hour.
Does anyone know what gear this is based on? Converting from kph to mph is no problem once I know what gear its' based on. The difference between 4mph to 10 mph with everything else equal can be threefold in chemical applied so I want to get it right!

Diamondpilot · Apr 16, 2013

I would use a gps ot a gps app for your phone and actually drive the tractor across the pasture to see what is comfortable.

You need a spead that keeps you from getting bucked off the seat and the spray rig in one piece.

Chris

pjbci · Apr 16, 2013

If you dont have a gps, just measure off 528 ft or 1/10th of a mile. Time it in the gear and the rpm's that you will be spraying at and do the math. Gps would be much simpler tho especially if it shows mph in tenths for a more accurate application of chemical.

Drafthauler · Apr 17, 2013

pjbci said:
If you dont have a gps, just measure off 528 ft or 1/10th of a mile. Time it in the gear and the rpm's that you will be spraying at and do the math. Gps would be much simpler tho especially if it shows mph in tenths for a more accurate application of chemical.

Now that you guys mentioned GPS , I do have a handheld unit. I'll give it a try.

Still would be nice to know what Jinma had in mind when they put those kph markings on the tach.

RonMar · Apr 17, 2013

Well with the GPS, you will be able to try different gear combinations and see if one gets the tach scale to agree with actual speed

I havn't read/heard about any correlation between a particular gear and the speed scale...

Drafthauler · Apr 17, 2013

RonMar said:
Well with the GPS, you will be able to try different gear combinations and see if one gets the tach scale to agree with actual speed I havn't read/heard about any correlation between a particular gear and the speed scale...

Good idea Ron. I will report back with that correlation if it exists. I kind of think it will be based on one of the high range gears as I understand these tractors often double as road transportation in China..

RonMar · Apr 17, 2013

Oh, instead of using a GPS, which I own, but didn't think of either

, I installed a magnet on the inside of a rear wheel rim on my garden tractor and installed a cheap digital bike speedometer. This worked very well to setup a speed appropriate to my spray nozzles and pump pressure on my tow behind spray rig...

Drafthauler · Apr 23, 2013

OK, the data is in. I used my handheld GPS to verify.

High range 1st gear at 2,000rpm gives me 4mph ground speed; about as fast as I want to go with the FEL mounted spray rig on rougher pasture areas.

And, the answer to the rpm/kph per the tachometer face is as I thought. The kph markings correlate to High range, 3rd gear.