Electric Power Scythe

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Hodor
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Electric Power Scythe

Post by Hodor » Thu, 03 Jul 2014, 22:09

Hi I have a 5 acre property, much of it covered in grass that gets very long in spring and summer, creating a fire hazard.

I was wondering whether it would be possible to convert one of these petrol driven power scythes to electric?

http://www.tracmaster.co.uk/bcs/crusade ... cythe.html

Cheers.

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BigMouse
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Electric Power Scythe

Post by BigMouse » Thu, 03 Jul 2014, 22:34

As with any cordless power tool, its usefulness is determined by its portability and run time. You -could- convert something like that to electric, but remember you'll be pushing the batteries around with it everywhere you go, you'll end up with less run time than the petrol engine, and you'll have to wait a few hours for it to charge between uses. To trim 5 acres, you'll probably end up taking several days to get through it all with charging time taken in to account. Assuming you work for a living, these days would probably get spread out over a few weekends. By the time you finished it, it'd be time to start over again.
Last edited by BigMouse on Thu, 03 Jul 2014, 12:35, edited 1 time in total.

Hodor
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Post by Hodor » Thu, 03 Jul 2014, 23:11

Oh. I was thinking if I were to provide the push power and mount one of these to some sort of frame with very large batteries attached?
Image

Wouldn't need to do it all in one day. At the moment I mow as much as I can once a year that nearly killed my last petrol driven mower. So could easily break up mowing over a few weekends.

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4Springs
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Post by 4Springs » Fri, 04 Jul 2014, 04:26

Hodor wrote: Hi I have a 5 acre property, much of it covered in grass that gets very long in spring and summer, creating a fire hazard.

I was wondering whether it would be possible to convert one of these petrol driven power scythes to electric?

Are you sure you want a scythe? The scythe is designed to cut without damaging the plant - good for cutting chaff or another crop, but probably not suited to just slashing grass and weeds. The grass is cut low down and just sort of lies over. It would need to be raked up after being cut or it would smother the growing grass underneath.
Scythes have that cutter-bar to avoid damaging a crop, but the cutter-bar itself is relatively prone to damage. Wire, rocks, sticks or pine-cones will all break the cutter-bar. Normally the cutter-bar is made of two blades which run the entire width - so if one bends or breaks then you have to replace it all.

The flail mower shown in that link would be more suited to what you describe. Mowers are designed to cope with a certain amount of rough treatment. You can normally replace individual blades, and damaging one blade doesn't make the whole thing inoperable. Mowers also chop up the grass into much smaller pieces, meaning that you don't have to rake it away (although it is a good idea if it is very thick). Having said that, the one in your link would be a very expensive mower! In my opinion you would be better served by a more normal ride-on mower. If you want to convert to electric then perhaps look around for an older ride-on that would take the weight of a few batteries?

I'm on a 5 acre property here, and we use a combination of cows and a slasher to keep the grass down (the slasher is behind a tractor). I've often wondered what the tractor would be like as an electric machine!

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Post by Hodor » Fri, 04 Jul 2014, 05:25

Yeah I wasn't going to use that mower, that price is bs. I've been looking into getting a ride on mower, but the only electric one on the market is the club cadet which costs about 4500, and I'm not even sure if they're available in Aus.

The rest of the commercially available cordless electric mowers look pretty sh*t. I was just thinking the power needed to work a sickle bar would be considerably less than a flail mower?

I'm talking about really tall grass, and these look a LOT better at taking it down than a normal rotary mower. Ie. the grass doesn't get jammed between the mower and the ground. when I used a standard petrol mower to take some down (it was a bloody ordeal) I ended up raking most of it anyway as having dead hay everywhere leading into summer isn't fantastic.

It just seems to me that these mowers look much better at tackling grass that has gotten too long for a rotary mower.

Cows or sheep would be great, but then you have to make sure they don't die. And me especially, as I'm a vegetarian I would feel like a bit of a tool if one died on me. :)

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Adverse Effects
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Post by Adverse Effects » Fri, 04 Jul 2014, 07:21

i think making a mower like my one would be more fun

stick a cam on it and sit back in the loung room and mow the grass with a beer

My Remote control lawn mower Monster Style
Last edited by Adverse Effects on Thu, 03 Jul 2014, 21:23, edited 1 time in total.

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4Springs
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Post by 4Springs » Fri, 04 Jul 2014, 14:31

Ha - I remember seeing that remote control mower but didn't realise it was you that built it AE!

I agree with you Hodor that a scythe would use a lot less power if you are cutting long grass. Each stalk of grass is cut only once instead of dozens of times. If you are happy to rake it away and sure it will be only grass (not rocks & sticks) then it could well be the way to go. Pick the time of year and you may only have to do it once each year. Using a flail mower means that you need to do it often to keep it manageable as you have found.
The modern equivalent of the finger mower is the disc mower. They use small, cheap blades which can be easily replaced in the field. They also only cut the grass once per stalk. They are much more complicated though and correspondingly more expensive so I think a scythe might be the way to go.

For 5 acres I think you will need to have it self-propelled, and will need a reverse gear.
Finger mowers have been around for a long time so there should be heaps of cutter-bars out there, both new and second hand. I wonder if you could adapt an old ride-on? If you removed the petrol engine and the mower deck then there would be some room in there for motor and battery. Traditionally the finger mower sits out to one side, not at the front like the one in your link. Doing this electric would probably be easiest if you used a different motor to run the cutter.

Or use a tow-behind like this: https://www.youtube.com/watch?v=pUPGAXRLzB4 Tow it behind your electric car and you'll be able to go all day! Note that the vehicle only drives on the part that has already been cut.   

Do you have any neighbors who make hay? If you don't want to use it at all then they might cut it, bale it and take it away for you. Would depend on the quality of the grass as to whether this would be an attractive deal for someone.

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Adverse Effects
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Post by Adverse Effects » Fri, 04 Jul 2014, 16:09

For 5 acres you would need a lot of battery's wouldn't you?

that is if you wanted to do it in 1 hit

you could always get borrow a few sheep or goats
Last edited by Adverse Effects on Fri, 04 Jul 2014, 06:10, edited 1 time in total.

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4Springs
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Post by 4Springs » Fri, 04 Jul 2014, 18:23

Adverse Effects wrote: For 5 acres you would need a lot of battery's wouldn't you?

I really have no idea!
Let's try some guesses:
If I had a 2m wide scythe towed behind the Brumby I could cover the entire 5 acres by driving about 10km (or maybe a bit more because there are lots of corners).
10km of driving would use about 1/10th of my battery capacity = 2kWh.
Driving the Brumby at road speeds and pushing a scythe along at a crawl would probably be in the same ballpark power consmption-wise. So 2kWh might be a rough idea to do the whole 5 acres.

How heavy would this be? Again as a ballpark figure, let's go to the EV Power website. They have 40AH CALB cells there.
40AH x 3.2V = 128WH.   
2000 / 128 = 15 cells required.
15 cells x 1.5kg = 45kg total.
Seems do-able!

Not sure on price for that cell, but if the pack was 1/10th the price of mine then it would be about $800. You could do it in lead-acid for half the price and double the weight.

Hodor
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Post by Hodor » Sat, 05 Jul 2014, 05:43

Adverse Effects wrote: <a href="http://youtu.be/rEsIP9WaSo0" rel="nofollow">My Remote control lawn mower Monster Style </a>


Hah! That's pretty cool. I'm surprised that really went through long grass quite well.

That tow behind looks sweet. I'm Guessing having the sickle bar to the side is so you can keep an eye out for debris. Your probably right I'll need a self propelled one for 5 acres. I was considering trying to convert a ride on. But considering I have know idea how to do any of this stuff, I'de just concentrate on making a electric powered sickle bar.

Then ideally make something like this and put it on the front.
Image

Thanks for the info, good to know its possible. Image

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Adverse Effects
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Post by Adverse Effects » Sat, 05 Jul 2014, 08:19

where are you? as if your not to far away i may have a ride-on mower carcass (mostly there) you could use as a base unit

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4Springs
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Post by 4Springs » Sat, 05 Jul 2014, 14:01

There is of course the Polaris ATV EV as shown here: http://http://www.polaris.com/en-au/atv ... /home.aspx (choose Ranger, then choose EV). 48VAC, 11.7kWh, 40kph; looks like it would be fun! A quick google found one for $18000.

On the tow-behind and on tractors generally they have the sickle-bar to the side so that the wheels don't run over the crop before it is cut. If you run over it then it can miss being cut - the blades will go over the top of some of the squashed stalks. I've driven over a paddock (of grass) with the tractor before I cut it. Once the hay was taken away the paddock was uniformly smooth except for those tracks of poorly cut grass!
You need a fairly heavy vehicle to have the bar out the side or it will twist around, although I'm sure the tow-bar on the trailed versions helps with that. On the disc mowers they had a spring arrangement so that if you ran into something the bar could swing around to point directly out behind you. Otherwise you can imagine that if you ran into a stump at speed you might cause quite a bit of damage to the mower.

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