Page 1 of 3

RC Mower

Posted: Thu, 12 Jan 2017, 04:20
by EV2Go
Hi All,

I had a 120hr old John Deere ride on mower lined up for $1000 but stupid me never paid for it before the guy changed his mind :(

So failing that I am now looking at building a big remote controlled mower instead. My partner and I bought a 1600sqm block late last year and it takes me about 4hrs to mow it with a 21" self propelled hand mower(with long grass).

So that should give you some idea of the scope of what I am looking to build (plus some overkill), If I built one somewhere around 36" - 42" I should be able to mow the block in about half that time. Put a house on the block and it should be even less time.

Since I have next to no experience in this field, I have very little idea how big the motors need to be to power it.

If I work on a weight of 300kgs all up, can anyone recommend twin drive motors from this website for me please (or if you know of a better source).

This is an incomplete idea of what I have in mind
Image


RC Mower

Posted: Thu, 12 Jan 2017, 05:31
by EV2Go
Two of these? too much, not enough? 48v DC 500A Brushless or perhaps two of these instead 24v 350w direct drive

RC Mower

Posted: Thu, 12 Jan 2017, 20:57
by Richo
All that looks too complicated.
I'd buy 2 used/damaged hoverboards that gives you get 4 single sided axle hub motors and mounting bracket.(~$150 total)
4 controllers off fleabay. (~$100 total)
Now you have a low profile base 600W+ with skid steer drive.

Then I'd go with an outrunner with 190kv and less ~$120 (hobbyking)
RC motor controller ~$100.
And while your at it get the remote transmitter and receiver.

Last is the reduction belt drive ~5:1? to go from the RC motor to the blades.

Off the shelf electric mowers are ~1000-1500W.
I've always put 50cc as around 2kW.

Batteries 1kW for 2hrs is 2kWh.
36V 55Ah (5 leaf cells?)
48V 40Ah

Nice pic tho Image

RC Mower

Posted: Thu, 12 Jan 2017, 21:21
by Richo
3S3P 12V20Ah SLA is still ~$700 and 60kg.
I guess 5 leaf cells would be ~$900 and 20kg.

RC Mower

Posted: Thu, 12 Jan 2017, 22:27
by Adverse Effects
ok drive system best would be old wheelchair DC worm drive

the hover board wheels are a no go as there is nowhere near enough power in them not to mention you are going to need at lest 2 drive wheels that are like 200mm to 300mm wide just to get enough traction(i know this because the 50mm wide ones i have slip all the time even on a minimal grade)

as for running the blades (3 blade deck) you want them spinning at around 3K and up to 5K RPM and am just guessing about 250 to 300 watts to run each?

so if a belt drive 1000watt motor or some way of individually running each blade with a blade mounted on the motor shaft

24VDC systems are easiest to get drivers for but 48 would be better as same watts less amp draw


RC Mower

Posted: Thu, 12 Jan 2017, 22:55
by Adverse Effects
something along the lines of this and notice the lever on each one it is a dog clutch letting you disconnect the wheels from the motor

Image

wheelchair bldc gear motor

but finding an old 2nd hand wheelchair cheep would be just as good to rob the parts off

RC Mower

Posted: Fri, 13 Jan 2017, 06:06
by EV2Go
I'm only thinking electric for the propulsion at this point, because a petrol engine can also be used as a generator for the wheels. Nothing on that motor website I posted of interest?

Is there a formula to determine motor power needed to propel 300kgs?

RC Mower

Posted: Fri, 13 Jan 2017, 17:59
by EV2Go
Been giving some more thought to your AWD idea Ivan...

How did you plan to set the motors up? both on one side connected, both on the other side?

RC Mower

Posted: Fri, 13 Jan 2017, 18:18
by Adverse Effects
if DC brushed motors yes 2 speed controllers (one for each side)

if BLDC 1 motor + 1 controller each side and chain drive from the centrally mounted motor to the wheels and mount the motor high on the frame

RC Mower

Posted: Fri, 13 Jan 2017, 19:16
by EV2Go
OK well looking to do duel steer (opposite directions for very low speed, same direct for high speed) which means each wheel / motor would need to be able to turn independently like on a stub axle.

So I guess that kind of leans me towards four of these and two of these for a combined power out put of 1.4kW @ 24v is that enough?

RC Mower

Posted: Fri, 13 Jan 2017, 19:22
by TooQik
Would going tracked instead of wheels offer any advantage in your situation?

RC Mower

Posted: Fri, 13 Jan 2017, 20:22
by TooQik
Found this prebuilt-2wd-66in-lawn-mower which is roughly the same weigh you're targeting.

They use this motor pair to drive it wheel-chair-motor-pair

If I'm reading the motor specs correctly, it looks like you'll have more torque using your selected motors than their version; 73.2 Nm (4 x 18.3) v 33.9 Nm (2 x 16.95), so I'd suggest your motor selection is fine.

RC Mower

Posted: Fri, 13 Jan 2017, 20:39
by EV2Go
TooQik wrote: Would going tracked instead of wheels offer any advantage in your situation?


If I was going to skid steer it would, but since I need all four wheels to turn to avoid chewing up the grass it needs to be wheels.

Image

RC Mower

Posted: Fri, 13 Jan 2017, 20:41
by EV2Go
TooQik wrote: Found this prebuilt-2wd-66in-lawn-mower which is roughly the same weigh you're targeting.

They use this motor pair to drive it wheel-chair-motor-pair

If I'm reading the motor specs correctly, it looks like you'll have more torque using your selected motors than their version; 73.2 Nm (4 x 18.3) v 33.9 Nm (2 x 16.95), so I'd suggest your motor selection is fine.


That was the direction I was originally thinking, but Ivan is right traction is a big problem with heavy mowers and any kind of incline.

RC Mower

Posted: Fri, 13 Jan 2017, 21:06
by Richo
Adverse Effects wrote:the hover board wheels are a no go as there is nowhere near enough power in them
Really?!?
They are rated for 350W - 500W peak each.
4 drive wheels 1400W/2000W.
They aren't high RPM either so a lot of that is torque.
Don't confuse the motor performance with the designed "usable" operation of the hoverboard.
Adverse Effects wrote: 2 drive wheels that are like 200mm to 300mm wide just to get enough traction(i know this because the 50mm wide ones i have slip all the time even on a minimal grade)
You mean the mower not hoverboard right?
Go stand on your mower and tell me if it still slips...
I have seen bigger off-road wheels just bolted through the back plate of the hoverboard wheels for faster off road fun!
You can't tell me a $25 bunnykings wheelbarrow wheel wont work.
Adverse Effects wrote: as for running the blades (3 blade deck) you want them spinning at around 3K and up to 5K RPM and am just guessing about 250 to 300 watts to run each?
...individually running each blade with a blade mounted on the motor shaft
3 blades now - designing on the fly ;)
3k-5k you can run each direct drive on an RC motor.
You'll still need the low KV motor
Adverse Effects wrote: 24VDC systems are easiest to get drivers for but 48 would be better as same watts less amp draw
Both hoverboard wheels and RC controllers will work on 36V.
36V is available for both.

Basically they only reason you wouldn't build it this was is if you were making a sellable product.

RC Mower

Posted: Fri, 13 Jan 2017, 21:10
by Richo
EV2Go wrote: Is there a formula to determine motor power needed to propel 300kgs?

Sure there is.
But it's quicker to go out and load up your mower to 300kg and push or pull with a set of scales.
This will get you your Force(kg->Nm).
Then just map this over your motor power curve...

Still would it really be 300kg?
How heavy is a 3 blade base?

RC Mower

Posted: Sat, 14 Jan 2017, 00:21
by EV2Go
Richo wrote: Still would it really be 300kg?
How heavy is a 3 blade base?
Hard to know how far over the top I will go... But I found a generic figure of 600lbs (268kgs) for a ride on mower, and considering some parts will be heavier (motor - batteries) and some parts will be lighter (frame - no seat - panels) add 30kgs for good measure I came up with a ball park of 300kgs all up.

Catch 22 on the push pull method I can't do the test until I build it, but will need the motors in place to do the test.

RC Mower

Posted: Sat, 14 Jan 2017, 01:36
by Adverse Effects
EV2Go you do realize your introducing in 4 more motors and controllers over and above the ones that drive the wheels if you want them to vector not to mention the programing to get them to work out weather to turn the same way or the opposite way   Image
Richo wrote:
Adverse Effects wrote:the hover board wheels are a no go as there is nowhere near enough power in them
Really?!?
They are rated for 350W - 500W peak each.
4 drive wheels 1400W/2000W.
They aren't high RPM either so a lot of that is torque.
Don't confuse the motor performance with the designed "usable" operation of the hoverboard.
yes china 350 watts so about 150 to maby 200 and there also a 60 volt system and the BLDC so you lose torque over a DC brushed motor running the same watts
Richo wrote:
Adverse Effects wrote: 2 drive wheels that are like 200mm to 300mm wide just to get enough traction(i know this because the 50mm wide ones i have slip all the time even on a minimal grade)
You mean the mower not hoverboard right?
Go stand on your mower and tell me if it still slips...
i can tell you with out a dout in the world that it will keep slipping because i thought the same thing more mass over the wheel better grip
i have had anything from 1 12V car battery to 2 20Kg 12V truck battery's directly between the 2 rear drive wheels the only difference it made was on slightly soft ground i had to go over and push it out of the ruts the wheels dug in to the ground with the 2 truck battery's only
in some cases that may be true like on cement and bitumen but on wet grass and dirt it is not the case it just cuts a grove this is why you need wider wheels to spread the the load/foot print (why do you think 4x4s put on wider wheels and tires? more grip)
I have seen bigger off-road wheels just bolted through the back plate of the hoverboard wheels for faster off road fun!
You can't tell me a $25 bunnykings wheelbarrow wheel wont work.
well i looked for the wheels you mentioned and all i found was china plates(go figger)

so they "just bolted through the back plate of the hoverboard wheels"
there a BLDC with windings just "through the back plate" so they must have done something funky with them
Image
not to mention you would need BLDC controllers for each wheel
Richo wrote:
Adverse Effects wrote: as for running the blades (3 blade deck) you want them spinning at around 3K and up to 5K RPM and am just guessing about 250 to 300 watts to run each?
...individually running each blade with a blade mounted on the motor shaft
3 blades now - designing on the fly ;)
no if you look at his pic you will see clearly 3 blades not to mention we have been discussing this fore about a week b4 this thread in emails
3k-5k you can run each direct drive on an RC motor.
You'll still need the low KV motor
are you in the RC hobby? i am and have spent more money on it than i care to admit even to my self to run the blades on a "BLDC outrunner motor" as there called in the hobby you would need as you say a low KV motor so lets take a look at the cheapest suppler there is hobbyking
your looking from $70 to $400 each motor (price denotes quality in these bit motors)
controllers $40 to $170 each (again price denotes quality)
then you have the problem of the bearings on the hobby grade stuff are of the lowest quality so collapse kind of young

not to mention the 6 to 8mm shaft the bigger BLDC outrunners have in them
i dont know how much of a load they could take wouldnt take much of a rock hitting the blade to bend the shaft and trash the motor
Richo wrote:
Adverse Effects wrote: 24VDC systems are easiest to get drivers for but 48 would be better as same watts less amp draw
Both hoverboard wheels and RC controllers will work on 36V.
36V is available for both.
ahh most hovverboards are 60V and RC controllers are just about any range you want depending on how much you want to spend

there again i have spent more money than i like to admit on this hardware you havent seen all my toys 1/2 filling the lounge room of my house EV2Go has
Basically they only reason you wouldn't build it this was is if you were making a sellable product.
or if you where building a unit once and didnt want to have to "fix" it every time you wanted to use it and EV2Go is like me in that aspect have a look at the CNC Mill he is building i think if a truck hit it the truck would lose and he (baring him selling it) will have that till the day he dies i wouldnt dout

RC Mower

Posted: Sat, 14 Jan 2017, 02:03
by EV2Go
Adverse Effects wrote: something along the lines of this and notice the lever on each one it is a dog clutch letting you disconnect the wheels from the motor

Image

wheelchair bldc gear motor

but finding an old 2nd hand wheelchair cheep would be just as good to rob the parts off


Sometimes talking to the Chinese is a bloody good waste of time. Tried contacting the seller. The showed me other motors, so I asked if they had the motor shown or not, no response...

Finally got a response US$390 plus postage for 2 Image

RC Mower

Posted: Sat, 14 Jan 2017, 02:24
by EV2Go
Adverse Effects wrote: EV2Go you do realize your introducing in 4 more motors and controllers over and above the ones that drive the wheels if you want them to vector not to mention the programing to get them to work out weather to turn the same way or the opposite way   Image
4 Motors to turn the wheels, something like 2 linear actuators to steer left right at front and back. Not looking to power the blades by motors too much hassle, too many batteries and expense.

RC Mower

Posted: Sat, 14 Jan 2017, 03:00
by Adverse Effects
EV2Go wrote:
Sometimes talking to the Chinese is a bloody good waste of time. Tried contacting the seller. The showed me other motors, so I asked if they had the motor shown or not, no response...

Finally got a response US$390 plus postage for 2 Image


HAHAHA yep been there done that

but i did say "something along the lines of this" and "finding an old 2nd hand wheelchair cheep would be just as good to rob the parts off"

hehehe look around and see if there is a mobilaty shop up there and see if they have an old trade in chair they will part with cheap

RC Mower

Posted: Sat, 14 Jan 2017, 03:03
by EV2Go
I'm not very good at finding second hand bargains and when I do I let them go... Otherwise I would be trying to remote control a John Deere ride on mower right now :(

RC Mower

Posted: Sat, 14 Jan 2017, 03:07
by EV2Go
Shaping up that these guys are looking like the preferred front runners. They're brushed so they could be used in pairs Image

RC Mower

Posted: Sat, 14 Jan 2017, 03:12
by EV2Go
Voltage: 24V
Power: 350W
No Load Speed: 213 RPM
Loaded Speed: 181 RPM
Output Torque: 18.3Nm
Reduction Ratio: 16.5:1
Splined Shaft
Brushed Motor

A 13" (330mm) tall tyre at 181 rpms = 11kph seems like a winner to me.

RC Mower

Posted: Sat, 14 Jan 2017, 03:16
by EV2Go
Something like 4 of these wheels and tyres