The good news is that I have ridden the riding mower. It occurs to me that I have put a motor where the battery was and batteries where the motor was. If that is progress. I’m taking a bit of a (holiday) break to regroup a bit. Some notes:

Speed: it is slower than I would like. I used a large gear for convenience which also has the effect of slowing things down. I have ordered a smaller gear that would speed things up. In no real hurry to change this. I can even eventually revisit direct drive with a shaft coupler.

Power: the original mower had a 14 horsepower engine. That would be a very large electric motor (at about 750 Watts per horse). I figured half that for general efficiency and half for moving the blades. Still a hefty motor. I was looking at a 1800W motor but eventually just went with the 500W based on gut. 500W turns out to be enough power for this vehicle, at least for my purposes. In the short test drive, power was never an issue, and the motor wasn’t even warm when I was done. Anyway, it looks pretty easy to swap out a motor if I want to upgrade.

Batteries: I went with the battery I had, a 12V lawn tractor starter battery. Not in any way ideal. I bought a second to get 24V. They are cheap and seem to be adequate. I can always change these. The new lithium batteries are light and hold lots of charge, but are expensive and don’t necessarily have a high output. This has led me to looking at chargers for battery banks and perhaps using the mower batteries as backup power, perhaps with solar charging. That seems like another project, though.

Electronics: Bought some new parts for control (variable resistor, switch, LED displays). Going to make a prettier display for the controllers. Ordered a second identical controller for the eventual blade motors. Also bought some proper wire and connectors (right now I’m using bits from the old mower which are not the correct sizes).

Blades: I have some ideas for the blades. That will be the second half of this project.

These projects aren’t much like the engineering projects I did professionally for years. I’m not constrained by a schedule or (within sane limits) costs. In that sense they are more Art Projects. I will mess around with them until I like what I have. There isn’t necessarily an endpoint deliverable. It is all for enjoyment.

Bolted the batteries down and attached the controller under the dash. Had hooked up some wires temporarily just to test things out. Decided to bolt the seat on and see if I could make it go. The chain kept coming off but tightening the bolt that held the pulley / gear on seems to have mostly fixed it. The gearing is probably too low, but I’m not in a hurry. Bought some parts to make a better dashboard. Going to start thinking about the blades.

There’s A Subculture Turning Riding Mowers Into Off-Road Monsters And It’s Fantastic

Four bolts and the engine was out. Not as heavy as I expected. Bought a second 12V battery and ran the motor at 24V. Chain keeps coming off but it is definitely happening on the master link where I shortened the chain. I didn’t use a proper chain cutter tool, just a hammer and punch, so I might have bent something a bit. Put some oil on it and it seems better.

Looked at the new foot pedal. Not sure I like it. I may just buy another controller like the one I have. I suppose having the throttle on a knob is ok since I have brakes that seem to be working well, and a brake switch that cuts off the motor ought to make this ok. Actually, the original throttle was on the dash.

Removed the deck that shields the blades. It was heavier than I expected. Hurt my back a bit lifting it. Seems overkill for what I want to do. Removing it made the mower look taller and sleeker, almost like something to race. Also drained the oil, removed the throttle control and the last of the belts and pulleys on the underside. Also got the main pulley that attaches to the main engine shaft loose. I feared this bolt might be my undoing, but it came off pretty easily. Ready to pull the motor, but going to give my back a rest. In the photo you can see my candidate for a blade (in green). Used to retrofit string trimmers for heavy work. 4 or 5 of these should do the trick. Need to figure out a new deck now. Also found a nice little electric switch that can signal braking to the controller (I think).

Up until now I’ve really just removed the battery and drilled a few harmless holes. But there comes a time to start really doing a Teardown. There is a bit more going on than I appreciated. First I removed the dual 42″ blades and the pulleys that ran them. Then I removed the controls and disconnected them from the engine. Then drained and removed the gas tank. A wiring harness was next. There is a somewhat complicated set of manual and electric interlocks that I still need to think about. For instance: shutting off the motor when the seat isn’t occupied, but only if the blades are in use (good if you fall off while mowing) or decoupling power from the drivetrain while braking. Removed the exhaust from the front and explored the engine mounts.

Also looking at wiring and placement of controls. A bit more to it than I realized at first. Will need two controllers, one for the drivetrain and one for the blades. A foot control is probably a better idea than a dashboard knob for a throttle. The second motor controller I have has little documentation. Wires are labeled in Chinese and something resembling English. Some experimenting is probably going to be necessary.

As far as blades, I’ve decided on 4 or 5 small blades used as string trimmer replacements. The whole deck is big and heavy and probably massive overkill for what I want to do. Might dump it all, but I will need a way to figure out how to support the blades and motors and how to make a safety cover. Probably not too hard, but something I didn’t intend to do.

Next big step: engine removal. Really not much left after that, just a frame and some wheels.

Lastly, I’ve started tagging blog entries. My goal is just to be able to group similar entries. I was just using keywords in the title, but best to use the proper tool for the job. Will go back and add tags to older posts.

I have the mower drivetrain (sorta) working. The chain slips off occasionally but if I am gentle with the throttle it seems ok. Because I had originally planned to go with a direct drive, the chain gears it down yet another notch. So max speed might end up 2 – 3 MPH. Probably ok for mowing.

Up until now I could easily re-assemble the pieces and go back to a traditional gas engine power. There comes a point when you have to make a more serious commitment to a project like this and going back is not an option. I think I am at that point. I pulled the blades and pulleys and disconnected most of the wiring. Next is draining and removing the gas tank and lastly, getting the engine out.

Then I’ll mount the electronics and start thinking about a for a test drive and details for the mower blades. Right now I’m planning on multiple (4 or 5) small motors driving small circular metal bladed made for string trimmers.

Again, I’m not really a mechanical guy (my specialty is electronics) but so far so good. Made an appropriately sized chain and bolted everything down. I ordered a chain tensioner (whatever that is) on line. Hopefully it will all fit together. Resisting the urge to bolt the seat on and go for a ride. Oh, need another battery. Running this 24V motor at 12V right now.

Started getting serious with the mower. I had the new motor on the bench working and now all that is left to do is install it. This is all experimental for me, so I’m hoping to be able to put it all back together an carry on with the the old gasoline engine if things don’t go well. To get more room to work I took off the seat and fenders and disconnected some wires. I feel like I’ve crossed a line here.

While I would have preferred direct drive, for very practical reasons I have decided to go with chain drive. The electric motor is made for a standard 8mm T8F chain common in modern electric scooters and such. I decided to stick with this since modifying it looks difficult. On the other end I have a large pulley made for a drive belt. It is attached to the transmission which has a spline shaft connection (I’m learning lots of new terminology here). I couldn’t find an 8mm sprocket that would hook to the transmission shaft so I figured the path of least resistance is to get a sprocket and drill and bolt it to the existing pulley. So far not hard. I also drilled and mounted the motor and things seem to fit well. Could probably even upgrade to a more powerful motor without much work if needed.

Now that I have this 8mm sprocket the smaller sprocket on the motor means a lower gearing. I was expecting a 1:1with the direct drive. Right now it is something much smaller. I found a bigger sprocket I can easily swap for the one that came with the motor, but it still is geared down a bit. We will see how that all works out. Have a chain and some bolts on order and probably need a tensioner. Figured I would deal with that once I have all the other pieces more or less put together. Then it could be getting close to a test drive.

Got my little 500W motor for my riding mower conversion to electric. The good news is it fits in the space under the seat near the differential. My hope was that I would easily and directly be able to hook my motor shaft to the shaft of the differential of the mower. It might not be that simple. There is a whole catalog of shaft couplers out there but the particulars of both the motor shaft and the mower shaft might make this a non-starter. I’m not skilled or set up to do metal work so I’m searching around for the simplest way to do this. I could go with a belt drive which keeps the belt pulley for the differential in place, but I’ll need a belt pulley for the motor and probably another on a spring for tension. Or I could use the chain sprocket on the motor but I would have to fit a chain sprocket on the differential shaft. There might be an way to use the existing belt pulley as a plate and bolt it to another plate fixed to the motor. Need to think about it.