Robs Stupid Rototiller Land


This is Robs Stupid Rototiller Page. It is Stupid. It is so stupid, you can click on any of the pics to enlarge them.

I had a really normal rototiller. The motor died and needed to be replaced.
I couldnt find a replacement motor, so I decided to convert it to electric.
I stole the electric motor from one of my robots that never became a robot.
The motor is an ME0909 and is rated to put out 4.8HP continuous or 12ish HP for 30 minutes.

Ginormous Motor Specs

May 7, 2021 Making a bracket for the electric motor to bolt in place of the gas motor was prety easy.

Tiller with an electric motor


I also decided to use the Lithium Polymer batteries that powered the quasi-robot.
Each battery group is 3 packs of 5AH x 6 cell batteries that makes 15AH @ 24V
They are rated to put out 30C which makes 450 Amps. Should be plenty to power a tiller.
I hadnt charged the batteries in several years and it turns out they were completely dead.
Lithium batteries dont like being discharged all the way for any length of time
I decided to take them outside to charge them since Ive heard of Lithium batteries going violent when treated wrongly
While I was charging the first pack, it made a little popping noise and a waft of smoke came out.
Didnt think much of it, but set it aside and decided to try charging a different pack.
About 5 minutes later, I heard the wife scream something, and I ran outside to see what the problem was.
Batteries died a fiery death.

Just one of the 3 battery packs

The other 2 packs in the group


I charged one of the other battery packs quite a bit slower and monitored the individual cell voltages pretty close.
2 cells in 2 of the 3 packs were shorted to 0V, and 2 in the third pack were really low voltage.
So out of 18 cells, only 8 were charging, and only up to 16V.
Decided to see how well it would run the tiller on 16V.
It was a little slower than the gas motor was, but tilled about 10 feet pretty easy
Then I saw a little puff of smoke come out of the area near the batteries. Arggghh.
I immediately diconnected the battery pack and placed it in the fire pit, in case it was going to burst into flames like the other one.

Decided to use Lead-Acid batteries to power the tiller instead of the volatile Lithium Polymer ones.
Didnt think too much about it before I ordered them, but the tiller has a flat tire and adding 130lbs would make an already unwieldy machine even more crazy.
Really need to have both tires in good shape to wrestle with the extra weight.
The only place that had a replacement tire was online and couldnt be gotten for at least a week.
Since Im stupid, I decided to convert the tiller to be pulled behind a 4 wheeler.

May 14, 2021 For the tiller to be used like a trailer, it has to have extra wheels to act like a trailer.
The wheels that the tiller was born with need to go away.
The wheel hubs were rusted to the axle and had to be cut off.
The new wheels are needed to keep the tiller upright while tilling.
Also, they are needed to allow backing up, whether or not tilling at the time.
In a perfect world, the wheels would be able to be raised and lowered with a push of a button.
Will have to see how much the feature is needed after a bit of use.

Ruined wheels

Stupid looking tiller in transport mode.


May 15, 2021 Thought of putting batteries in a few different places.
Ended up setting the batteries on the 4 wheeler for now.
Some 2 guage cable wired up and its ready to till!!

Wiring all done.


I envisioned a fairly complicated lifting mechanism involving part of a scissor jack for a car.
Ended up just using a cranky strap to hold the tines off the ground during transport.

Super hi tech lifting mechanism.


Got tired of messing with it and decided to use it.
I just locked the drive into reverse rotation mode, and strapped the lever to always be on.
It works AWESOME!

The travel speed doesnt seem like it matters much.
Sitting still for several seconds, then moving forward 4 inches or so works well.
Driving at a really low constant speed works great.
Driving at a walking pace seems to work well too.
Happy Giggles!

I thought it would be hard to back up, but it turns out that with the motor off,
it turns the tines backwards when backing up.
With the motor running, it kinda pulls the 4 wheeler backwards to help back up.

I tilled an area about 20ft x 6ft in about 20 minutes.
Amazingly, there were no issues.
Batteries, wires, and motor didnt seem to get any warmer than they would from just sitting in the sun.

Area of tilled dirt.

Tilled dirt closeup (How stupid is that?)


Recharging the batteries took 14.8AH, which means that tilling took an average of 44.4 amps.
44.4 amps x 24 volts = 1065watts, which equates to a bit over 1hp average.
Quite a bit lower than I would have guessed.
I think Im gonna try a bigger pulley on the motor, since going faster is almost always better.

There were only 2 concerns:

Driving really slow seems to ride the clutch of the 4 wheeler.
Hopefully thats not going to wear out the clutch prematurely.
Maybe using the forward tine rotation mode would take less power to propel?
Not sure if it would til as well though.
Tilling in forward mode before it was a trailer went way too fast and was too hard to control.

Twisting around in the 4wheeler seat to watch the tiller as it is working is kinda uncomfortable.

May 18, 2021 Got a longer battery cable to enable installing the batteries on the trailer

Much better setup


May 22, 2021 Put a larger pulley on the motor. Faster is good.
Went from a 2.25 inch to a 3.5 inch. Should be about 1.5 times faster (theoretically).

Much bigger pulley


Lifting the tines off the ground was too annoying, so I got a 200lb linear actuator to do the lifting for me.
Took a couple tries to get the right geometry, but it works now.
The lifting part just hooks under the tine cage, so it doesnt get thrashed around while tilling.
Maybe later, I will attach it with a flexible piece of something, to avoid having to reattach it to lift back up.

Silly lifter thing


Mar 25, 2021 After replacing the pulley, I used the tiller for about 15 minutes.
Watch 30 sec clip of tilling, oh joy!!

I expected it run about 50% faster, and take nearly twice the power.
Seems like it was running nearly twice as fast. No measurement to confirm such things though.
It took 13.05AH to recharge the batteries.
So a little over 52 Amps average. Not much more than the 44 Amps it was with the smaller pulley.
More than likely, the cause for it to be similar, is that I was forced to go slower this time.
Since the belt tensioner wasnt attached, the belt slipped when it hit a hard spot, and I slowed down or stopped.
Will have to setup the tensioner and try again tonight.

Mar 26, 2021 I tightened the tensioner and ran it for about 30 minutes.
The belt didnt slip at all, and it worked way better!
Every once in awhile, it would hit a hard spot and the motor would actually slow down instead of slipping.
It took 20.3AH to recharge the batteries, so an average of 40.6 Amps.
I expected it to be much higher, but part of the area I was going over had already been done.
Im pretty darn happy.



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