Lawnbot...

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Will Dobbins

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Sep 1, 2016, 10:28:55 AM9/1/16
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I saw this thing on a facebook group yesterday for sale for ~$600 in Wisconsin... and my lawn is in desperate need of attention... because I'm fat, have bad knees, a bad back, and generally lead a busy enough life I have little desire to go mow the lawn when it's 100 degrees out...

I also am pretty sure I have almost everything I need to build something like this... I have a Taranis (Transmitter) and a wide variety of receivers, I have more video cameras and transmitters than I can count, and to take it up a notch I have Pixhawk compatible flight controllers which generate PWM signals to drive the thing... and firmware already designed to run land based vehicles...

So I'm looking for some guidance on the drive train - I don't need speed, but I'd like it to be pretty torqey as I have a decent hill in my back yard, and I think with the batteries slung nice and low the CG will allow it to safely navigate said hill.  Any suggestions on motors/speed controllers that would take a PWM input and be reversable?  (Planning on tank drive so need 2)  Also advice on how much torque will be needed would be appreciated... I've got 2 SLA 70AH batteries to mount on it, which is about 100LBS of battery, the electronics mean nothing compared to that, and I have no idea what the mower weighs...


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Ray Scheufler

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Sep 1, 2016, 10:38:01 AM9/1/16
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Personally I would go with wheelchair motors (and their associated gearboxes) and use FRC motor controllers.  I don't know if I would go too far into figuring out all the math and torque.  I would just try something and see if it works. 

From experience, the SPARK motor controller with two CIMs on each side will move a 150lb robot around a competition field pretty quickly.  I suspect that you will be fine using a single wheelchair motor on each side.

Ray Scheufler

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Will Dobbins

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Sep 1, 2016, 11:02:01 AM9/1/16
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The controller indicates 30% duty cycle, and cites 3 minutes on 7 minutes off, as mowing the lawns likely to take 1+ hours is this likely to be an issue or just provide good airflow and heat syncs?

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Tim-S

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Sep 1, 2016, 11:15:37 AM9/1/16
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Walk behind mowers range from about ~40 - 80lbs depending on the size (19" - 21"), how thick the metal is, whether it's a steel or alloy deck, whether it's self-propelled, etc. Once you add the weight of the batteries, framing to hold them, etc., I'd bet you are looking at a 160 - 200lb machine.

As someone who has flipped a walk-behind mower on a very steep hill ... yeah. Make sure the COG is as low as it can possibly get.

Will Dobbins

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Sep 1, 2016, 11:18:41 AM9/1/16
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Batteries will be in a tray just in front of the rear wheels as low as possible because the idea of flipping a lawnmower is horrifying!

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Ray Scheufler

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Sep 1, 2016, 11:39:15 AM9/1/16
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About the only thing I can say is try it and see.  Fans and heatsinks will be helpful.  I don't have much faith in any of the rc car motor controllers not exploading themselves.  I trust that the spark will protect itself pretty well.

You could go with china ebike controller but they won't take RC signaling.  You could also go with a forklift controller but again it won't take RC signaling.  It probably wouldn't be hard to convert between RC signaling and what those controllers want but it would be something that is needed.

Ray Scheufler

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Will Dobbins

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Sep 1, 2016, 11:41:08 AM9/1/16
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It's a bit much for try it and see to be a viable option... I'll continue digging!

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Dan Hockey

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Sep 1, 2016, 1:45:52 PM9/1/16
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One of the larger mowers with hydrostatic(hydraulic) drive would be easier to control with servos than trying add drive motors and batteries to a small push mower.

Will Dobbins

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Sep 1, 2016, 1:56:43 PM9/1/16
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It certainly would be, it would also be a whole lot more expensive.

On Thu, Sep 1, 2016 at 12:45 PM Dan Hockey <icep...@gmail.com> wrote:
One of the larger mowers with hydrostatic(hydraulic) drive would be easier to control with servos than trying add drive motors and batteries to a small push mower.

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Don Cady

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Sep 1, 2016, 2:22:31 PM9/1/16
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Don't we have some wheelchair motors on the hack rack?
Good timing Will! We're about to clean that out tonight and may be tossing those motors. If I'm recalling correctly, would you like some who-knows-where-they-came-from wheelchair motors?

Don

Will Dobbins

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Sep 1, 2016, 2:36:12 PM9/1/16
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If they don't have a more appropriate home Absolutely!
On Thu, Sep 1, 2016 at 1:22 PM Don Cady <don...@gmail.com> wrote:

Don't we have some wheelchair motors on the hack rack?
Good timing Will! We're about to clean that out tonight and may be tossing those motors. If I'm recalling correctly, would you like some who-knows-where-they-came-from wheelchair motors?

Don

On Sep 1, 2016 9:38 AM, "Ray Scheufler" <dr.bob....@gmail.com> wrote:
Personally I would go with wheelchair motors (and their associated gearboxes) and use FRC motor controllers.  I don't know if I would go too far into figuring out all the math and torque.  I would just try something and see if it works. 

From experience, the SPARK motor controller with two CIMs on each side will move a 150lb robot around a competition field pretty quickly.  I suspect that you will be fine using a single wheelchair motor on each side.

Ray Scheufler
On Thu, Sep 1, 2016 at 9:28 AM, Will Dobbins <zan...@gmail.com> wrote:
I saw this thing on a facebook group yesterday for sale for ~$600 in Wisconsin... and my lawn is in desperate need of attention... because I'm fat, have bad knees, a bad back, and generally lead a busy enough life I have little desire to go mow the lawn when it's 100 degrees out...

I also am pretty sure I have almost everything I need to build something like this... I have a Taranis (Transmitter) and a wide variety of receivers, I have more video cameras and transmitters than I can count, and to take it up a notch I have Pixhawk compatible flight controllers which generate PWM signals to drive the thing... and firmware already designed to run land based vehicles...

So I'm looking for some guidance on the drive train - I don't need speed, but I'd like it to be pretty torqey as I have a decent hill in my back yard, and I think with the batteries slung nice and low the CG will allow it to safely navigate said hill.  Any suggestions on motors/speed controllers that would take a PWM input and be reversable?  (Planning on tank drive so need 2)  Also advice on how much torque will be needed would be appreciated... I've got 2 SLA 70AH batteries to mount on it, which is about 100LBS of battery, the electronics mean nothing compared to that, and I have no idea what the mower weighs...


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Justin Richeson

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Sep 1, 2016, 6:25:12 PM9/1/16
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Let me know how this goes for you Will! I was looking at the commercial electric options the other day as I also have issues with the time and the lawn..... if there are any extra motors like that let me know. Unfortunately I'm out of town all weekend. We'll be back to check out the maker faire Monday afternoon.

Ray Scheufler

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Sep 7, 2016, 10:08:38 AM9/7/16
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This just came across the Arch Reactor list:
https://youtu.be/xyJCN61mtpM3

May be someone you can chat with to figure out what all is needed.

Ray Scheufler

Jordan Burklund

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Dec 4, 2016, 5:23:22 PM12/4/16
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Will, if you are still interested in a remote controlled lawnmower, I have one that I built about 9 years ago that is taking up space in my parent's garage.  I'd be willing to let it go for less than the price of the one in Wisconsin, and can include an appropriate motor controller if you don't already have one.  The mower engine and everything else runs well, and the only thing that needs replaced is the batteries.




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Jordan

Brad Freese

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Dec 4, 2016, 7:37:48 PM12/4/16
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Jordan,
If Will isn't interested, I'd be curious to know how much you're selling it for. My email address is bradley.[my last name] at gmail.com
Thank you!
Brad Freese
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Jordan

Jason Keller

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Dec 4, 2016, 9:46:59 PM12/4/16
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Let me know price if he is not interested 

Jason Keller

Will Dobbins

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Dec 6, 2016, 7:13:31 AM12/6/16
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What sorta price are you looking for?
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