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Discussion Starter #1
hi,

Reaching out for ideas on how to mount leaf motor/gearbox.

My intention is to mount the unit at the rear ( like the big boys do with the tesla drive units)

I have gone ahead and bought a used leaf sub frame, my initial idea was to fab/fit the sub frame at the back and fit the motor straight on its own mounts.

But looking now the sub frame weight somewhere about 35Kg and I will still have to build some kind of box section frame to mount it on.

thinking now is either make custom mounts or cut down the sub frame and fit the mount parts that are needed only.

Appriciate any ideas that you think of





 

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It looks like you have some cracked and broken aluminum castings on your motor/inverter(M/I). You should probably deal with those first.

Next, I would mount the M/I onto the sub-frame, since you already have it. I would clear out the area where it's to be mounted under the vehicle. Lower the vehicle onto the M/I/sub-frame(M/I/S) or raise it up under the vehicle to check for initial fit and clearance.

Next, you want to evaluate the suspension. Will the existing hubs and control arms, if it has them, work with the sub frame? Are you going to use the Leaf hubs and suspension parts? If it has leaf springs, will a de Dion axle fit in the available space? If necessary, someone specializing in fabricating trailer axles could probably make up a de Dion axle for you.

With these decisions made, you can proceed with the fitting of the M/I/S closer to its final location. The 4 perimeter mounting points on the sub-frame are a very convenient mounting system for the sub-frame. Do they and other parts of the sub-frame need to be cut off, repositioned, and rewelded? Do the mounting points on the vehicle need to be reinforced? At some point, you'll probably need to cut a hole(s) in the floor for vertical clearance. Shock and spring towers/mounts, if used, will need to be designed, fabricated, located, let-in to the vehicle chassis/body, and welded into place.

If you want to evaluate the suspension geometry throughout the wheel travel, it's a good idea to just tack-weld the parts in place. This is so they can be easily cut and moved later, if necessary, to adjust the geometry.

The half-shafts will probably have to be made-up to match the trans axle output to whatever hubs are used.

Does any of this give you some good ideas?
 

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Discussion Starter #4
It looks like you have some cracked and broken aluminum castings on your motor/inverter(M/I). You should probably deal with those first.

Thanks for the ideas.

You have me concerned now can you elaborate on where the cracked and broken aluminium castings ?
 

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How valuable the Leaf front subframe might be depends in part on the car it's going into, and what will be used for suspension. For instance, if it will be used with a McPherson strut or perhaps double wishbone suspension, you might be able to use the Leaf arms and the subframe would be ready to use with them. So... it's going in the rear of something, but what, and with what suspension?
 

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It looks like you have some cracked and broken aluminum castings on your motor/inverter(M/I).
You have me concerned now can you elaborate on where the cracked and broken aluminium castings ?
From some angles it looks like the stud hole in the front left mount area looks cracked, but from above it looks like an intentional slot.

electro wrks, is that the only one?
 

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Discussion Starter #7
How valuable the Leaf front subframe might be depends in part on the car it's going into, and what will be used for suspension. For instance, if it will be used with a McPherson strut or perhaps double wishbone suspension, you might be able to use the Leaf arms and the subframe would be ready to use with them. So... it's going in the rear of something, but what, and with what suspension?
Its a 1973 BMW its going into, I want to keep the original double wishbone suspension setup. Thats why I'm thinking I wont need the whole subframe.

Going to start stripping the back end of car this weekend, That is a large subframe to get in.

 

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Its a 1973 BMW its going into, I want to keep the original double wishbone suspension setup. Thats why I'm thinking I wont need the whole subframe.
That looks like a typical 1970's BMW, complete with the classic semi-trailing arm suspension. It is not a double wishbone design at all.

With this suspension the Leaf subframe is not likely workable. I'm not convinced that the Leaf drive unit (motor and gearbox) will fit at all, without the motor housing running into the right-side suspension arm and/or the right-side spring. The Leaf's drive unit configuration and McPherson strut suspension work with each other, but the drive unit was never designed to work with semi-trailing arms.

The other challenge is that it looks like the motor will try to occupy the same space as the structural rail areas of the body which runs to the right side of the final drive (diff) housing. The Leaf unit is much taller than the original final drive, especially with the inverter still mounted on top of the motor (as shown in the first post); at least the converter and charger are not still on top of the inverter.


One detail to keep in mind as you work out the installation and a subframe: the BMW's existing suspension subframe consists of a beam running across the car and carrying the suspension arms, plus the final drive or structure around it forming the third arm of a sort of T-shaped structure, presumably attached to the car by those two horizontal bolts at the back of the final drive housing. Assuming that the Leaf drive unit is not used as part of this structure, you need some framework to connect the beam to the point where the final drive currently mounts.
 

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Discussion Starter #9
The other challenge is that it looks like the motor will try to occupy the same space as the structural rail areas of the body which runs to the right side of the final drive (diff) housing. The Leaf unit is much taller than the original final drive, especially with the inverter still mounted on top of the motor (as shown in the first post); at least the converter and charger are not still on top of the inverter.


One detail to keep in mind as you work out the installation and a subframe: the BMW's existing suspension subframe consists of a beam running across the car and carrying the suspension arms, plus the final drive or structure around it forming the third arm of a sort of T-shaped structure, presumably attached to the car by those two horizontal bolts at the back of the final drive housing. Assuming that the Leaf drive unit is not used as part of this structure, you need some framework to connect the beam to the point where the final drive currently mounts.

I am planning to remove the whole boot floor area

I am thinking to cut and remove the cross beam that supports the diff at the moment.

Was even thinking of separating the invertor from the gearbox

One question. If i mount the gear box say 3" of centre from the drive shaft will the CV joints be OK with that or do they need to be in line?

Only reason for this route is the ongoing issue with coupler for the leaf shaft, or I would go conventional route with mounting to the cars gearbox.
 

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Hi Zippy

You can move your diff (in the leaf transaxle) a good bit further back than the BMW's diff is
The CV joints will work fine

If you have a look at the way the driveshafts work in the BMW I bet that they normally droop about 70mm to 150mm - so they are used to operating at that angle - and the angles change as the wheels go up and down

Looking at the pictures I don't think you will have enough space - unless you cut the BMW suspension arms and make them longer and move the beam they attach to forwards

OR - you may be able to put the Leaf unit in backwards
 

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Discussion Starter #11
OR - you may be able to put the Leaf unit in backwards
Think this discussion has been made in the past, that would be a ideal solution
I think the standard leaf invertor has limits about going in reverse.

Pauls controller will make the motor run at full speed in reverse, but the leaf gearbox isnt designed to run at speed in reverse.

I dont want to cut out the diff support beam in the boot to find it doesn't fit

Its not looking good at the moment :confused:
 

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Like Brian says, What I saw as a crack must be a slot in the mounting boss casting. Mounting this unit in the rear seems like a lot of trouble to go to because a suitable coupling can't be found for a bolt-to-the-transmission mounting. Has anyone come up with a coupling to fit the Leaf motor?
 

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I think in this discussion we're seeing why there are only rare instances of an electric drive unit being mounted anywhere which wasn't originally an engine location. Those rare cases all include specific design features which are significantly different from the combination of a Leaf drive unit and semi-trailing arm suspension.

I am planning to remove the whole boot floor area

I am thinking to cut and remove the cross beam that supports the diff at the moment.
That leads to substantial work to restore the structure of the rear of the car. Also, the suspension subframe needs that third mounting point to the car's structure.

Before cutting anything, it would make sense to me to unbolt the whole suspension from the car and set it up with the motor to see how it might fit together.

Was even thinking of separating the invertor from the gearbox.
It's really separating the inverter from the motor, but okay...

While that's easier with the earlier style of Leaf drive unit (in which the parts are connected by external cables), it should be possible even with this later style to pull off the inverter and build some cables and seals for the terminal access openings to separate the components.

One question. If i mount the gear box say 3" of centre from the drive shaft will the CV joints be OK with that or do they need to be in line?
As Duncan said, you can shift the drive unit (presumably rearward for more clearance to the suspension arms) so that the outputs are off line from the centre of halfshafts, within reason. Lots of production vehicles have an offset like this, usually because a rear-mounted engine is too long to fit otherwise. Watch lengths - you don't want a CV joint to hit its length limit and try to pull apart at full suspension compression or extension.

You can also shift the whole drive unit sideways (to the left), putting it closer to the centre of the car, for better clearance to the right-side suspension parts. That means a longer axle shaft on the right side and a shorter one on the right side, but you're going to need custom shafts to connect the Leaf drive unit outputs to the BMW hubs anyway.

CanadaLT28 has the only combination of Leaf drive unit and semi-trailing arm suspension that I've seen, and to make it work he has the drive unit shifted to the left, relatively narrow suspension arms, and a wide vehicle.

Only reason for this route is the ongoing issue with coupler for the leaf shaft, or I would go conventional route with mounting to the cars gearbox.
If you can fit the whole drive unit in the rear, you also remove the motor and transmission weight from the front (which is going to be heavy once it is stacked up with battery), and provide much more space in the front for battery (by getting the motor out of the engine compartment).
 

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Looking at the pictures I don't think you will have enough space - unless you cut the BMW suspension arms and make them longer and move the beam they attach to forwards
I agree that space between the arms is a real problem, but both extending the arms and the related relocation of the subframe forward would have substantial consequences to suspension geometry and structure.

I think it would be more feasible to modify the suspension arms to narrow them, so that the inner pivot point is further outboard, leaving more room for the drive unit between them. Even that would require stiffer bushings and substantial structural re-working of the arms.
 

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It might help to start with a chassis drawing such as this one, and see how the Leaf drive unit (and possibly the subframe) would fit into it - you have the drive unit so you can measure key dimensions.

2002-Chassis.jpg
 

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Discussion Starter #17 (Edited)
Thanks for feed back very informative.

Had a quick look in the garage tonight, Think everyone's response is correct that the sub frame wont fit, I'm not even going to think about cutting and modifying the suspension arms.

Back to the drawing board, if you look at the leaf motor setup, there is no reason why the front engine mounting arms cannot be removed, they have a three bolt triangle setup.

Im sure with some 6mm steel plate, shorter mounting arms could be made. maybe even use different mounts, the middle part of the leaf mount has to be in the air.

had a rough measure up .I think that the width of the engine could be down to 26-28 inches.

Make a H frame engine cradle for the engine to fit. this is probably more like CanadaLT28 has done

If you can fit the whole drive unit in the rear, you also remove the motor and transmission weight from the front (which is going to be heavy once it is stacked up with battery), and provide much more space in the front for battery (by getting the motor out of the engine compartment).
My thought exactly, think of the weight and space saving by losing the whole original transmission setup
 

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Back to the drawing board, if you look at the leaf motor setup, there is no reason why the front engine mounting arms cannot be removed, they have a three bolt triangle setup.

Im sure with some 6mm steel plate, shorter mounting arms could be made. maybe even use different mounts, the middle part of the leaf mount has to be in the air.
I do see how the two mounting brackets that are visible in the photo are bolted on, and I assume that the other is similar. Different brackets could certainly be used, as long as sufficient distance is maintained between them (for stability) and room is left for the rubber isolators.

had a rough measure up .I think that the width of the engine could be down to 26-28 inches.

Make a H frame engine cradle for the engine to fit. this is probably more like CanadaLT28 has done
Great, but if you look at CanadaLT28's setup the whole width of the drive unit is between the inner ends of the suspension arms. Looking at the BMW chassis, the distance between the arms is barely more than the width of the final drive housing... not nearly wide enough for the Leaf gear. It works for CanadaLT28, because he has a wider vehicle, and probably narrower suspension arms.
 

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I don't have a great pic showing my setup so I'll take a better picture tomorrow. Not sure if it will help at all as it looks like yours will have to be quite different.


I'm still interested in the motor coupler if anyone has a pic or a product to look at.
 

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Discussion Starter #20
I don't have a great pic showing my setup so I'll take a better picture tomorrow.
Have you made engine mounts or is the engine sitting in the air
 
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