Chestnut harvesting sled

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Sorry, mistyped the title. Here we go:
Folks, first post here is a carryover from the General Topics forum. Subsequent posts will be here.
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Hello, all !
I am a DIY entusiast and have learned much from the AtomicZombie site and plans.

Inspired by Brad's creations, I am building an e-powered sled to assist in harvesting chestnuts on my nascent commercial chestnut orchard in West Central Illinois. The core of the device is constructed from two hacked mountain bike frames.

Essential features are: low to the ground, stand-on, driven by two independently controlled, rear hub motors, castering front wheels, with steering by differential throttle. Hub motors are geared, low ground speed, high torque electric wheelbarrow motors, sourced from the Chinese manufacturer through Alibaba, and are due to arrive tomorrow.

Much work is yet to be done. To give a general idea, I will attach a photo of the core of the frame to this post (if I figure out how). I will attempt to post a build blog of the project in the Yard and Farm section of these forums.

Looking forward to your comments!
Mike S.
Atlas Nuts
 
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The "chassis" is hacked together from two ladies mountain bikes that were on sale at Walmart for $59.99@, including delivery. Not being as resourceful as Brad, and needing two matching rear frames, buying new seemed expedient, and I'm left with lots of other parts for future projects. The rear bike frames I connected together using a close-fitting tube through the crank holes, a sheet of 1/8" cut to fit between the inside arms of the rear frames (with lightening holes), and a rectangle of 1" square tubes in front. The operator will stand on the platform, with his weight just ahead of the two rear wheels. Castering front wheels will be added to forward corners. The chestnut collection basket will be carried on the forward frame.
 
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The two geared (I hope) electric rear hub motors (with wheels and 10" ag tires), controllers, and thumb throttles arrived today.
 
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Having had zero experience with e-bikes (or any electronic circuitry, for that matter), I was happy to find this thread on the Endless-Sphere forum, in which a "philf" explores a Brainpower controller, which is a different model, but has exactly the same nest of connectors. He very helpfully includes an English language directory of his findings, and comments about the various functionalities.
 
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For the castering front wheels I'm using the head tubes and bearing assemblies from the two bikes I hacked, plus surplus anti-scalping wheel assemblies retired from a mid-mount mower deck. Because the wheel assemblies are offset, I needed to fabricate brackets to bring the wheels back in line (and somewhat trailing) the head tube pivot points. Hoping they will track properly.
 

Radical Brad

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One thing I found out on my robotics platforms using wheelchair motors is that tracking is a real problem.
What I mean is that on the wheel chair, the pilot is the nav system, using a joystick to make non stop adjustments.
On my bots, I tried sending the same power to R/L motors and the bots would never go in a decent straight line.
I ended up having to add expensive encoders to the motor shafts and a microcontroller to sort it all out.

I think your system will suffer this issue much worse for a few reasons...

  • You are going very fast. My bots only did 3 MPH.
  • You have independent controllers per wheel (same as my bots).
  • You have terrain that will introduce differing friction per wheel.
Your machine is a prototype that will certainly evolve, but if I had to venture a guess so far, I would say that control will be almost impossible.
Some type of serious gear reduction to limit your top speed to say walking speed (say 1:6 reduction) will probably help a lot.

A further solution would be to control with one joystick, using encoders to keep the motors synchronized as per the control unit.
At that point though, it would be less work to build your own controllers and driver from scratch.

Brad
 
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Brad,
Yes, this certainly is a prototype. Haven't bench tested them yet, but at 48volts drawing 16 amps with no load these motors are rated to max out just under 400 rpm. On 10" wheels I calculate that to be 11.7 mph. At 24V and 15amp top spead is rated just over half that. Walking speed is all I need. Perhaps knock down the voltage and use suitable controllers? Begs the question will there still be enough torque? I have spent a lot of time operating a Wright stand-on mower, 19hp Kawasaki gas motor, powered and steered by hydraulicly driven differential rear throttles (even forward one side and reverse the other is possible for zero turns). Sometimes it feels like riding a bucking bronco, and it is no good for extended straight line mowing, but it is superb at close maneuvering. Customizing or building my own controller(s) is way beyond me.
Thanks
Mike
 
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BTW, having some trouble updating the imbb album. Here's the latest pic of the castering fron wheel assemblies.
 

Radical Brad

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Thanks for the pic, this reminds me of my ZTR mower...

3580

if you are just on mowed grass, it may not be too difficult to "skid steer" your unit.
The longer wheelbase will help, as it will make it harder for the unit to turn, which is a good thing.

Will be interesting to see the initial test run for sure!
I still vote for... far too fast, but it's all just a wild guess.

16 amps just spinning? I think you may have a problem with something there.
My Yard Mule draws less than that driving on the lawn, and it weighs 500 pounds.
With a wheel in the air, it spins up on 24 volts with maybe 5 amps at the most.
My motors are 20,000 watt capable as well, so something does not add up with your 16 amp unloaded draw.

Brad
 

Radical Brad

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When you get a chance to do a spin test, it would be interesting to see the actual current draw.
At 16 amps idle, that would mean they are using sandpaper for bearings or something crazy!

Brad
 
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https://i.ibb.co/xHkdRPd/image.jpg[/img
Took it for a test run today.
It works!
So far unable to load the video on imbb, as the file is too big.
Perhaps a YouTube link?
 
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