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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.

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

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Motor vehicle Automotive design Automotive exterior Engineering Auto part


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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