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David Brown 880 Tractor
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Discussion Starter · #1 ·
I'm looking do a 40hp tractor conversion. I've managed to find, and have now bought, a David Brown 880 Selectamatic with a tired engine - rest of the tractor is mechanically sound (so I'm told), but it does need some TLC (definitely doesn't look anywhere near as good as the one in the photo below :) ). So, here's my plan for the conversion so far:

If you look at the David Brown 880 picture below, it shows you the tractor and how the major engine and transmission components are layout.

Wheel Tire Vehicle Automotive tire Tractor


And, the following gives an exploded view of those major components:

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My plan is to remove the engine - basically everything above the sump frame including the crankshaft. The sump frame will remain, as it provides the structure for the front frame (and front axles and wheels) to stay connected with the rest of the tractor. Although the sump frame may need some reinforcing, which I'll hopefully be able to do when mounting the electric motor and structures for holding batteries.

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The flywheel and double-clutch, one for PTO and one for transmission, will remain (NB. the orientation of the double-clutch diagram is 180deg out - i.e. the PTO friction plate end goes into the right-hand side of the flywheel in the left diagram). So, the electric motor will be attached to the flywheel - I will need to get a coupling manufactured to match how the crankshaft was bolted to the flywheel.

However, as the engine normally runs from 700 to 2000rpm, I expect a reduction gearbox, or pulleys and belt, will need to be used between the electric motor and the flywheel. Plus the reduction box/pulleys-&-belt will also allow the motor to be mounted above the sump frame, as I don't expect there will be enough room down in the sump frame where the coupling will attach to the flywheel.

Anyway, that's my plan thus far (still waiting for the tractor to arrive). But, what do you think of my plan thus far?

Next step, researching electric motors (I'm think around 20kW?), controllers and batteries.
 

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David Brown 880 Tractor
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Discussion Starter · #5 ·
My donor tractor finally arrived last week. So, I started stripping the ICE over the weekend.

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On investigating how to remove the engine block (which means splitting the tractor between transmission and clutch housings) I've now realised that my Plan A (see posts above) to attach the motor via gearing to the flywheel (thus keeping the use of the double clutch for running transmission and PTO off the one electric motor) is flawed. The weight of the flywheel, currently supported by the ICE's crankshaft, would be quite complex to support without ICE, and then keeping it balanced and not putting strain on the shaft (I'd have to fabricate) and bearings supporting it. And the crankshaft can't be used, as it attaches to the block and not the sump frame and will need the oil pump running (essentially keeping most of the ICE components, which doesn't gel with me).

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So, Plan B is to now do away with the flywheel and clutch and instead use two motors & controllers - one attached via gearing to the PTO shaft (the smaller shaft within the outer transmission shaft in the above photo) to drive PTO and rear hydraulics, and the second motor attached to the outer transmission shaft (the rear spline pictured above) to drive the tractor gearbox. Removes heaps of dead ICE weight from the tractor (more room for batteries :)) and I believe this will be a lot more efficient too - don't need to run the PTO motor unless the PTO and/or rear hydraulics are needed. Could also use different gearing to suit each use too.

Right, this weekend's job - try and block & tackle out the great lump of an ICE :D
 

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Great project! I have a Leyland 255 in the barn which I am planning to start converting later this year. Have a leaf motor ready for it.

I have also been pondering the clutch/no clutch issue in order to deal with the independent PTO and hydraulics. Very interested to see how you solve it on your project.
 

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David Brown 880 Tractor
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Discussion Starter · #7 ·
Thanks, LrBen.

I decided to go the no-clutch route. Quite glad I did now that I've stripped the ICE, clutch and flywheel out. The flywheel and clutch were quite a lot heavier than I thought and were basically supported by the ICE's crankshaft and the clutch's pressure plate splines mated to the PTO and transmission drive shafts. Anyway, here's progress to date:




Time to get rid of that fossil fuel burner...

To remove the engine first the tractor needs to be split at the clutch.




You can see the clutch pressure plate within the flywheel housing in the above photo.

Removed the clutch and flywheel (damn, those were heavy - glad I decided on Plan B). Then removing quite a few bolts (and one that took me ages to find 😀) and the oil pump, the engine could be hoisted out.




Clean up time and there we have our "blank canvas" - all the remaining bits of the tractor I will add the electrical bits to.




So, those shafts sticking out of the transmission are where I need to attach the reduction timing belt pulleys that will be belt driven by the electric motors.





But, they'll need a bit of support.



The reduction timing belt pulleys will be splined and matched to the shafts like the old clutch plates shown below.




Only remaining issue I can see is that the flywheel housing won't allow me enough room to fit the motors, pulleys and belts inside it (as those shaft splines sit pretty much mid-way within the flywheel housing). So, I've now cut out the top of the flywheel housing.



This will allow the two electric motors to be mounted just above the flywheel housing (one probably facing backwards and one forward) with their belts running down through this cut-out to the pulleys on the transmission and PTO shafts.

I then bolted the front and rear back together (flywheel housing bolted back to the clutch housing). Might need to add some structural bracing to the cut flywheel housing and sump frame, but I think my 'blank canvas' is ready to go.






Bunch of parts on order - pillow block bearings, timing pulleys and belts, motors and controllers, batteries (cheap deep cycle lead acid ones for testing), etc. So, no action for a little while, but plenty of tidying up work to do in the meantime...

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Drained and replaced transmission & hydraulics oil and filters. Rebuilt the steering column and rack. Repaired rust in guards. A lick of paint and the rear of the tractor is now looking sweet!

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Motors, controllers, batteries and a few other parts recently arrived (I'll provide details if these in another post soon). So, I could then mock up the layout:

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My father-in-law is a design engineer, so he's now designed mounting brackets for the motors and confirmed timing belt pulley and belt sizes. So, with them on order it's more waiting now for a while :) . But, it's all starting to come together...

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I've worked a lot with tractors this size and larger. Those motors look pretty small for the job. The overall power required shifts mostly to the implements when using tillers and large mowers, through the PTO, and to the drive wheels when plowing or pulling large loads. For this reason it might be better, power-wise, to use one larger, more powerful motor to power both the PTO and wheel drive.

This tractor probably has a lever and dog clutch PTO engagement system. Without a clutch, you would have to stop the motor to engage the PTO, possibly also to disengage it. For safety reasons, you need to make sure the PTO can be quickly stopped. This goes for any set-up.
 

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David Brown 880 Tractor
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Discussion Starter · #9 ·
Thanks, electro wrks for your reply. I'm hoping I've done my sums right on the motors, at least for my needs anyway. We only have a small (12 acre), flat lifestyle block of land, so I don't need the tractor to do anything too meaty. Mainly towing a small car trailer around with hay on it and occasionally topping (small 1.5m slasher mower) some paddocks (takes about 20mins to top a paddock with my current Fergie 135 tractor).

I've also bought these cheap motors and controllers to start with, in case I have got it wrong. If I have to 'upgrade' to better motor(s) later, I'm ok with that. I've also gone with two different types of motors and controllers too, just to make the project even more interesting ;-). Fyi, the motors and controllers details are as follows:

For transmission: QS-Motor QS-180 motor with Far Driver ND72850 controller. Hope we get the 8kW rated (@4200rpm) & 15kW peak (6000rpm) and 18.2Nm rated & 65Nm peak (@1895rpm => and using 2.6:1 reduction this equates to 728 shaft rpm, which was pretty much the idle speed of the diesel engine).

For the PTO: a Golden Motor - HPM-10kW motor with VEC500 controller. Should give 10kW rated (@3700rpm) & 20kW peak (5000rpm) - 26Nm rated & 85Nm peak (again with 2.6:1 reduction it will increase the toque and power to the PTO shaft). The VEC500 has cruise control, which should be good for holding PTO speed.

Both motors running at peak power/torque is around 400A using 48V, so hopefully it's all enough. For comparison the DB880 ICE had peak 47Hp (35kW), when new, and 120 lb ft (160Nm) of torque, so with the 2.6:1 reduction and split load across the motors, I'm hoping we're within the realms of usability.

Yes, the PTO lever is at the rear, behind the seat. Will need to stop the motor to engage the PTO, but the PTO can be disengaged using the lever without stopping the motor. However, for both motors, I'm also mounting large 'emergency stop' buttons on the dashboard.

What do you reckon?
 

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(again with 2.6:1 reduction it will increase the toque and power to the PTO shaft). The
The torque is increased proportional to the gear ratio, but the horsepower, or Watts in SI units, remains about the same. Horsepower is a measure of the ability to do work. That is to say to move a given weight a given distance over a given time. If you are satisfied with a tractor that can do less work, that's fine.

In practical applications it might mean you have to run a smaller diameter mower, a not as wide tiller, and to me the most frustrating part: crawling along at a slower speed on the public roads between fields.

My father-in-law is a design engineer, so he's now designed mounting brackets for the motors and confirmed timing belt pulley and belt sizes.
I would recommend you have PTO slip clutches on any PTO driven implement that might jam and stop suddenly. Without a clutch, the teeth on the belt might be overloaded and stripped off. This just might be an application where a properly sized multiple V-belt drive system, that slips to accommodate a rare overload, is a better choice. On the overload subject, I don't know about you, but my first reaction when things go sideways on a tractor with a clutch(es) is to slam my left foot down on the clutch pedal. Maybe in addition to the kill buttons you could have some kill switches activated by the clutch pedal.

This looks like a fun project. As in: I wish I had the time and resources to finish the projects like this sitting in my boneyard! Keep up the good work and let us know how it goes.
 

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2015 Leaf, 1964 Oliver 1800 Tractor
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Following with great interest... I'm in the early stages of converting an Oliver 1800 tractor. Trying to come up with ideas for a clutch design (want to keep the live PTO), and single leaf motor.
I will be interested to see how things go for you with the geared belts - I'm thinking of 5-v-belt pulleys for the reason mentioned - in case things need to slip.
 

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David Brown 880 Tractor
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Discussion Starter · #13 ·
David Brown Electric Tractor is coming along
She's starting to come together nicely!

While waiting for the motor mounting brackets and timing belt pulleys to arrive I tackled the bonnet. Having all those electric bits I needed to make the bonnet more waterproof, including sealing over the fuel, water, exhaust and air-cleaner holes, and making a solid front grill (with mock mesh). And, of course, including new LED headlights 😃.

David Brown bonnet refurbishment & LED headlights
And, new decals and "EV" stickers.

Electric Tractor Dashboard

As shown above, I repurposed the old tractor dashboard (which needed a sturdy mount, as it holds up the rear of the bonnet too) and installed the gauges (Cycle Analyst CA3 ones), switches and other controls I needed - one set each for the separate motors and controllers.

Yay! The motor mounting brackets have arrived, so now some real progress...


Motors mounted (still awaiting pulleys)

If anyone's interested, here's the CAD drawing for the mounting brackets:


After completing all the wiring and hooking up the batteries I gave the controllers and motors a test run. After trouble-shooting a few minor issues and getting a Hall Effect throttle for the transmission controller (couldn't get the Far Driver ND72850 to work very well with a potentiometer throttle) everything is working as expected.

Electric motors mounted and wired up


Wiring is still a bit messy. I'll loom it all better once we've had some decent test runs and are happy that no changes are required.
 

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David Brown 880 Tractor
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Discussion Starter · #17 ·
Still a bunch more to do (motor controller tuning, lots of test runs to measure power loads, better batteries then procured and installed, chassis front-end refurbished, etc), but at least she's moving :).
 
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