How to know MPH travel speed with B7800 hydro?

[sixdogs]

I need to use a B7800 hydro trans Kubota to spread some fertilizer and I need to know my MPH travel speed to spread the correct amount. It's not that I need to a specific number, I just need to know a number and then can adjust the rate of spread to work with the ground speed. Anything in the 5 MPH range would work as long as I kind-of know what it is. Doesn't have to be exact but I need the PTO to be at 540 RPM.

How do I figure this out? The owners manual only gives a range of speeds.

 

[TMGT]

Mark a distance on the ground, set engine rpm at pto speed, select a range (most likely L or M), time the distance with stop watch and calculate speed.

Make sure you start before the mark and just start the stop watch when you pass the start marker.

I've done this on other hydro tractors for spraying, they had a hand control so I could mark the dash with tape once I found the speed I needed, with the foot control, full pedal is about the only way to be consistent.

 

[MossRoad]

Yep. Time your travel over a marked distance with the engine set at an exact RPM and your foot all the way down on the forward pedal. Don't let up on the pedal.

 

[David_Kb7uns]

You can also use a good GPS or find a bicycle speedometer that has enough range that you can calibrate to the tractor tire size that you have and just mount a magnet on the rim to trip it.

David

 

[bdhsfz6]

I use my handheld Garmin GPS for this purpose and made a tractor mount to hold the device. It reads speed to a tenth of a MPH and distance to within 10 feet depending on tree cover. The GPS also provides other useful information such as time and temperature.

 

[sixdogs]

I use my handheld Garmin GPS for this purpose and made a tractor mount to hold the device. It reads speed to a tenth of a MPH and distance to within 10 feet depending on tree cover. The GPS also provides other useful information such as time and temperature.

View attachment 504769 View attachment 504770

I have a plug-in NUVI-57 Garmin for the truck. Suppose that has the same info?

 

[TMGT]

I haven't had much luck with the vehicle gps with speed accuracy, when I tried my garmin it was somtimes a couple mph off, not bad when driving but too much for low speed imo.

 

[bdhsfz6]

I have a plug-in NUVI-57 Garmin for the truck. Suppose that has the same info?

The Nuvi-57 is mainly an automotive unit. Although it will help, as TMGT says, the speed accuracy isn't that good. You would also have to rig up a power outlet for it. You are better off with a handheld unit which has better slow speed accuracy and the ability to customize the display. These units are designed for slow speed hiking use. You don't need an expensive model, you can get a basic hiking or biking model for less than $100. On eBay, used ones are going for much less. With a handheld, you don't need to wire up a power outlet. Just use rechargeable batteries which in my case, last for a couple of weeks on the tractor.

 

[sixdogs]

The plan now is a handheld Garmin. I have done the measured distance thing before, and that is good advice, but Garmin is easier. I'm also going to look for my old B7800 sales flier from 15 years ago since I think it mentions a speed range. That might be something.

 

[TMGT]

An accurate gps is definitely the best way to go, especially with a foot controlled hydro.

Just an fyi, the speed ranges in the sales flyers are usually only listed for ag tires which I believe are taller on the b7800 so it won't be accurate for turf or r4.

 

[sixdogs]

An accurate gps is definitely the best way to go, especially with a foot controlled hydro.

Just an fyi, the speed ranges in the sales flyers are usually only listed for ag tires which I believe are taller on the b7800 so it won't be accurate for turf or r4.

If I can get rolling circumference, I can math out what ought to be correct for different tires. I have done this before. It only has to be sort-of close anyway. I'm pretty sure it was in the original sales flier and I know I have that flier so it's just a case of finding it.

 

[TMGT]

Yup, just a little math, they sometimes specify different speed with different tires but not always, however the defult is almost always for ag with a few exceptions.

 

[CobyRupert]

Use a watch

5 mph = 7.333 ft/sec

Paint stripe across tread of tire.

Determine distance traveled by driving 1 revolution under real world conditions (example soft soil, pulling a load, etc.. .) Note I didn't say determine tire circumference because there are real world slippage factors). Example: One revolution of a 10 foot circumference tire may only travel 9 feet in soft soil pulling a load.

You now know 1 revolution of the tire = x feet traveled.

Use a watch to determine time of 1 revolution = y seconds

Divide 'x' feet by 'y' seconds = this is your speed in "ft/sec". If less than 7.333 ft/sec go faster, if more, slow down.

 

[sixdogs]

I found my original sales brochure last night and under statistics it listed tire sizes and speed of R1 (only) at rated RPM. Here's what I learned:

12.4-16 R1 37.6" diameter-- speed 0- 3.1mph @ rated rpm (540 pto, 2600 rpm) in L, 0-5.5mph in M and 0-12.2mph in H
12.4-16 R4 36.9" dia
13.6-16 turf 38.0" Dia

Since I have R4 tires, I figure the tractor will be going about 2% slower than the 5.5mph in M gear, I can get close enough for my purposes. The fertilizer is flinging out in a 30 to 40 ft pattern, depending on how I set it, so it will have good coverage and my human error exceeds the variables anyway. I'm going to check this with a handheld GPS if I can borrow one or I bet a cell phone will have the same accuracy.

Sound OK?

 

[bdhsfz6]

I found my original sales brochure last night and under statistics it listed tire sizes and speed of R1 (only) at rated RPM. Here's what I learned:

12.4-16 R1 37.6" diameter-- speed 0- 3.1mph @ rated rpm (540 pto, 2600 rpm) in L, 0-5.5mph in M and 0-12.2mph in H
12.4-16 R4 36.9" dia
13.6-16 turf 38.0" Dia

Since I have R4 tires, I figure the tractor will be going about 2% slower than the 5.5mph in M gear, I can get close enough for my purposes. The fertilizer is flinging out in a 30 to 40 ft pattern, depending on how I set it, so it will have good coverage and my human error exceeds the variables anyway. I'm going to check this with a handheld GPS if I can borrow one or I bet a cell phone will have the same accuracy.

Sound OK?

You can try a smartphone using a navigation app but the accuracy issue will be the same as an automotive GPS. It would be better to use a hiking / biking app on a smartphone that is WAAS and GLONAS capable. Many smartphones don't have true GPS functionality. They use cell tower triangulation to determine location and are ok for basic automobile navigation but lack the accuracy you are looking for.