Mini E tractor project advice/collaboration

[Tom Allen]

Project I've been working on that I wanted to share and see if anyone had advice /wanted to collaborate on. It's for a good friends off grid not for profit farm as a bit of an experiment to save them pushing thousands of wheelbarrow trips per year!

Requirements 

Vehicle for use on an eco farm , muddy tracks, many slopes but nothing steep, site 1km wide roughly

Tow a trailer (they already have) with loads on it - main use

No fossil fuels or combustion

No wider than 1m to fit on existing paths

Not faster than jogging pace for safety

Easy to use for less able users (older volunteers etc)

Stretch goals

Removable battery for charging elsewhere in winter

Two batteries

Load rack on front

Upgrade trailer with electric tipping action

Lighting for dusk use

Other farming accessories attachments? 

 Parts acquired so far

A broken 125cc mid size quad bike (I've already removed the dinosaur juice engine) with large good knobly tyres . Suspension, steering and brakes all seem to work. Missing seat and some body panels. Rear axle is fixed, no differential, which isn't ideal but it was only £100. drive is a large sprocket and thick chain

50 X 20ah lithium polymer pouch cells - according to data sheet they are good down to 0degrees C and can deliver 80a continuous. Connection is M5 bolt. 

Copper Link bars for pouch cells to make series packs

Daly BMS 50a - simple version, no UART or bluetooth

48v lipo charger, pretty dumb but does cut off when full

1800w (claimed) brush less motor 3500rpm with cheapy no name controller and throttle/reverse switch etc 48v . Output is tiny 8mm sprocket at the moment. 

Cheapy led volt and amp metre (100v, 50a shunt)

11 : 1 reduction box from the original engine setup. The clutch and CVT belt system from the original engine was totally broken so this is the only part usable. This fits in the frame and connects to rear axle with existing chain. Input is currently a thick steel shaft with keyway

Foam and faux leather to make a seat

Thoughts so far

Direct connect motor to reduction box with coupling or use another chain? What ratio do I want in addition of the 11:1 ? System where I can switch out to a different ratio after testing without too much rebuilding/cost? 

Main jobs

Motor to reduction box mechanicals. Chain? Coupling? Belt? Mod shafts to take whatever transfer mechanism chosen

Fabrication of motor mounts etc

Chain tensioning?

Battery box fabrication, assembly and testing of 48v pack

Housing for all electronics (waterproofing?)

Fit and mount all parts inside existing frame space (plenty of room)

Seat fabrication

Trailer mounting point welding

Let me know your thoughts!  

Tom

[Gavin]

Gotta say, and not sure if this is helpful other than for inspiration / ideas, but when I read the basic requirements I thought - golf buggy

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[Vidar Velle]

Loads of electric agricultural quad bikes and tractors out there for sale. The decent ones are rather expensive though. 

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[Tom Allen]

I did look at buying a golf buggy and tried two of them out. They were too wide and too expensive for this project and only came with tyres suitable for grass not mud, so that would be an extra cost to replace them. The gearing was also too high so that would need work too and the 1000w brushed DC motor on the cheaper one I found was under powered for the job. They still wanted £2000 for it with no batteries ! So far I've only spent £1000 including the 50 lipo cells which is more than I think I need for this project. 

On Sat, 7 Aug 2021, 23:40 Gavin, <gavi...@gmail.com> wrote:

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[Ian Petrie]

Or there is always ....

https://www.dragondriving.co.uk/horseforsale-172672.html

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[Frans Wilbrink]

How about one of these?

https://www.amazon.co.uk/Greenworks-40V-Cordless-Garden-Cart/dp/B06Y11W8KH/

https://www.manomano.co.uk/p/makita-dcu180z-wheelbarrow-brushless-18v-lxt-body-only18v-19385042?model_id=19383044

On Mon, Aug 9, 2021 at 12:39 PM Tom Allen <t...@randominter.net> wrote:

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[Tom Allen]

Frans

We have tried the makita e wheelbarrow and it was woefully in-adequate and very small motor and battery for the money, it also struggled going up inclines with more than 75kg on it despite the claims on the box. also 2mph is a bit too painfully slow to work with all day. we sent it back for a refund!

i am aiming for 300kg load at 6mph up the inclines on site (sorry i haven't measured them yet) for under £1000. i am also aiming for 6 hrs of use per charge. the makita barely managed one hour.

and surely making some crazy contraption from broken other vehciles is more in the hacker spirit? hehe

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Tom Allen
+44 7939 025 131

[Frans Wilbrink]

Deffo more fun!

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[circle]

Repurpose a hover board

https://github.com/NiklasFauth/hoverboard-firmware-hack

If you want larger wheels then use the hoverboard motors as hubs with 8 inch trailer wheels or similar 

If you want more precise control of where it gone 

https://github.com/alex-makarov/hoverboard-firmware-hack-FOC

what about pairing it up with differential GPS setup oops I am getting carried away 

[Tim Masson]

I used to tow a 5' * 3' trailer behind my ride-on Lawn-mover until some scruds came and stole it from me :-(.  The trailer is rated for 300 kg probably weighs more than 100 kg empty.  The Lawnmower was 7.5 hp (according to the manufacturer) but could easily tow the trailer around the garden - there are a few small inclines  and when it was wet the tyres would chew into the lawn so you definitely will need big treads.   

For electric propulsion I think you will need something heavier than a hover board.  

Electric Drive will be a bit of a challenge.  Could you re-purpose the drive from a mobility scooter?  I know the trade-in value for these tends to be pretty meagre - and an old one will have shot batteries (which you don't need?) - does anyone in Hack-space have a contact with a dealer - who might be able to find a bit of a junker that you could buy at trade-in value? 

[Tom Allen]

Will be coming down tonight to work on this if anyone is interested. Mostly battery stuff tonight I think

Also now thinking about making a shell for it that looks like the Tesla Cybertruck hehehe I've got shiny coated aluminium sheets that could possibly mimmic the stainless look 

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[Alex Gibson]

Dooooo iiiiiiit!!!

 

Alex Gibson

 

+44 7813 810 765    @alexgibson3d    37 Royal Avenue, Reading RG31 4UR

 

admg consulting

 

edumaker limited

 

·         Project management

·         Operations & Process improvement

·         3D Printing

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Virus-free. www.avg.com

 

[Jeremy Poulter]

https://youtube.com/playlist?list=PLbncXbXlaNQdXNRtgoENL0UmLw86i1wWz

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[Tom Allen]

Oh yeah that's totally my inspiration :) love the hacksmith channel (although it's a bit too ' hyped up for TV' style for my preference, they do make some seriously impressive stuff)

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[Carlo Zinzani]

How are you planning to charge your batteries? 

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[Stuart Ward]

This is a TED talk on creating the 50 open source machines that would be needed to restart society.

https://www.ted.com/talks/marcin_jakubowski_open_sourced_blueprints_for_civilization

One of the first was a tractor.

Stuart

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[Jeremy Poulter]

This has just come up in the Open Energy Monitor community forum: https://community.openenergymonitor.org/t/the-little-electric-tractor/18975

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[Frank in Woodcote]

I just read this, so not sure if it's still a goer... 

My thoughts are to work backwards. If you know the final top speed of the thing, say 6mph, you can work out how many RPMs you need from the motor. You know the wheel size, then the circumference and ultimately how many rpms the wheels need to do. Then you can work out the gear ratio through your reduction box.

 If the reduction is 11, you'll get a huge torque multiplier, so it'd be easy to break something, or split a mounting. For a speed controller, especially if it runs lowish voltage (under 20ish), you could simply use an old speed controller module from an electric drill. The fun bit would be to make proportional control, so that the harder you try to pull the thing, the harder the motor would work to try and catch up with you (or get away from you if you were pushing). A bit like how power steering works in a car.