Calibrating the Seed Drill

John Deere Type B Seed Drill

My John Deere Type B Seed Drill needs to be calibrated so that it dispenses the seeds at a predetermined rate – usually pounds per acre. This drill emits seeds based on volume/size rather than weight.

I learned how to calibrate a seed drill from this video.

Setting the drill on stands so the wheels can spin freely and turn the drill to emit seeds.

The first step is to get the drill off the ground so you can spin the wheels freely. It’s a delicate operation as there aren’t many safe places to lift the drill.

I use a shop lift with a chain around the short axle.

The drill is quite heavy and there aren’t many places to lift or jack without damaging the axle or gears.

I use a jackstand to hold the drill up while I’m working on it. Note the very narrow space for the jack stand to rest without damaging the axle and gears.
A good grease job every time helps insure that my drill be continue to be useful in the future. I invested quite a bit of time in rebuilding it so I want to make sure it lasts and works well for a long time.

Greasing equipment is a nasty job but definitely worth it. This drill sits outside (too big to fit in the barn) so taking a little extra care is worth it.

The drill is fully elevated and ready for calibration.

The purpose of elevating the drill is to allow you to spin the wheels freely and emit seed. It also requires that you lower the discs to the lowest position so the seed can flow freely through the seed tubes.

I collect the seeds in an empty water bottle but since we’re going to be dealing with very small measures, a tare on the bottle is necessary.
Water bottles are mounted on stands (bricks or blocks) to mate closely with the seed tubes and accurately collect all of the emitted seeds.
Closer detail of bottle setup for seed collection.
This lever controls the feed rate for one half of the seed drill. There is another lever on the other end of the drill.
The drill wheel is marked with tape to accurately count wheel revolutions.
A small amount of millet seed in the hopper for calibration measurement.
Seed collection while the wheels are turned.
Weighing collected seeds.

Here are my calculations:

Wheel diameter = 86″ or 7.1666′

Row spacing = 7″ or 0.58333′

Tare weight of bottle = 21g

I desire 55#/acre for each of foxtail millet and hegari.

Hegari is first to calibrate since it will plant last.

48g of seeds (plus 21g of tare) needed in each bottle based on calculations from video above.

Loosen and set seed flow lever to 8 based on very faded instructions on the inside of the seed hopper lid for wheat at 60#/acre as a reasonable starting point.

Turn wheel 20 times and weigh seeds.

The 4 bottles resulted in 51g, 54g, 61g, 67g – so too little and need to open seed flow lever a little bit. Also, the right side feeds more than the left side.

Add 2 notches on the left side and leave the right side alone and will be good enough for millet.

Restart calibration with Foxtail Millet.

The 4 bottles resulted in 52g, 55g, 50g, 45g – again too little and need to open seed flow lever more. Sides appear to be balanced though.

Adjust left side to 8 and right side to 10 and retry.

The 4 bottles resulted in 72g, 62g, 55g, 60g – on average too little but good enough to go with.

Adjustments in the lever increase or decrease the seed feed rate.
Seed drill calibrated and ready to plant!

Afterwards…..

I measured my acreage at 1.8 acres and used 100# each of foxtail millet and hegari seeds. I planted each separately at the rate of approx 55#/acre so I should have almost exactly run out of seed at the end of my planting for each seed.

But, the hegari ran out early at 80% planted (20% short) and the millet ran long at 80% over.

As I was cleaning up I noticed that I had not cleaned out the hopper and seed feed mechanism well enough. I use compressed air and was blowing out the seed hopper and all kinds of crap came up from the seed feed gears that I did not notice early in the process.

I need to do a better job of cleaning and prep to get a more accurate planting next time.