# Motor in place of half shaft. Dual shaft hub motor?



## brian_ (Feb 7, 2017)

I'm trying to understand what you are proposing. Do you mean that instead of the motor being the hub (a "hub-motor"), you would want a normal hub and bearing assembly, but with a motor attached directly to the hub, so it moves with the hub? You might call that a hub-mounted in-wheel motor.

If that's it, any motor could be used, and all will be too heavy and bulky... especially if used without gearing between the motor and the hub. If you add gearing, you can use a smaller motor, but you are carrying a gearbox on the hub as well.

An example of an axle with a motor mounted on each end, and each motor equipped with a reduction gearset to drive the hub, is the ZF AVE 130 system; of course, it's a huge and heavy setup since it is for big buses (and it is also used in a Mercedes battery-electric truck).


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## kennybobby (Aug 10, 2012)

Not sure what you are asking, but here are two concepts, probably not direct drive, but have some diff gears.


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## brian_ (Feb 7, 2017)

kennybobby said:


> Not sure what you are asking, but here are two concepts, probably not direct drive, but have some diff gears.


The Acura unit (used at the front of the NSX and rear of the MDX and RLX) includes two motors (one for each wheel), each with reduction gears to an axle shaft. The two side are also connected by an interesting differential and clutch arrangement, possibly unique to Honda.

The Bolt unit is typical of modern EVs, and consists of one motor, driving a differential via two stages of reduction gearing, with of course the two outputs of the differential driving the axle shafts.


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## brian_ (Feb 7, 2017)

rmay635703 said:


> ... a hub motor with an input shaft or a motor that could mount in the place of a half shaft...


Okay, it has just dawned on me what might be wanted here...

Is the idea to supplement an existing drivetrain (which includes axle shafts a.k.a. half shafts) with electric motors, with one motor for each wheel, rather than centrally located at the engine output or transmission output?

If that's the case then no, I have not seen a motor set up with one end of its shaft connected to the hub by an axle shaft, and the other connected to the output of a differential; however, it could relatively easily be done, since motors are routinely available with either the shaft sticking out each end or an internal spline on one end.

A challenge is packaging - assuming an independent suspension - since the length of two motors end-to-end plus a differential between them plus the shortest workable axle shaft on each end can easily add up to be too wide to fit between the vehicle's hubs. The solution is "pancake" motors: anything relatively short, but large in diameter to have enough power. Many pancake motors such as the YASA products are axial-flux, but even the HVH motors (from Borg-Warner, previously Remy) are reasonable short and have a very short bearing-to-bearing length. Each motor would need either a splined shaft compatible with insertion into the differential, or an internal spline to accept a stub shaft from the differential.

The bigger challenge is gearing. If the motor shaft is simply connected to the axle shaft, the motor turns at hub (wheel) speed, so it has all of the high-weight and low-torque issues of a direct (no reduction gearing) hub motor... it's just mounted inboard instead of outboard.


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