Double thick motor wires by half in one side and half in the other of a fully hollow shaft??

I've been looking at hub motors where ALL the wires go into/out of the motor through one side of a hollow shaft, with much ado about maximizing wire thickness to avoid them getting hot.

That left me scratching my head:
If you want thick wires that stay cool etc; why not have a fully hollow shaft all the way through, so that 2 of the phase wires can go in one side of the shaft and the 3rd phase wire and neutral in the other? (Yes Hall Sensors etc)
Surely I'm not the 1st person to think of this, so there must be some reason no-one has stuck their shaft in a lathe to make it hollow all the way through so wires can go in from both ends, so they can run 'double thick' wires into the motor??

What am I missing?
Shaft strength issues?
Or is the 'One Side Only' thing really just; No outside the box thinking!?


While I'm at it, there's much ado about what plugs work best as in 'don't overheat' too.
Surely simply soldering the wires (untwisted together) is so much better that the whole issue/question goes away?
Then simply keep an 'Unplugger' that looks just like a gas powered soldering iron in your toolkit along with some heatshrink..?

If one wants to simplify the quick de-solder/solder process then an easily desolderable/solderable plug is the answer?
Obviously any/all all high current wires are already soldered into plugs are they not!??

Obviously any/all all high current wires are already soldered into plugs are they not!??

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No, they're crimped. For various fun reasons, that actually makes a better bond with the connector if enough force is applied.

of the phase wires can go in one side of the shaft and the 3rd phase wire and neutral in the other?

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Might be interesting from the RF standpoint. Otherwise, it's mostly about much more complex installation and cable routing. Most bicycle hubs simply don't use cables thick enough to cause problems.

Surely simply soldering the wires (untwisted together) is so much better that the whole issue/question goes away?

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It's just not practical. Making a good solder connection for wires of this thickness requires a lot of heat, fast, and it's not something you want to do unless you can avoid it. The cheapest way to avoid a "connector" is to use simple crimped eyelets and three screws in a plastic block. This is how my motor came and it's a simple, cheap and robust solution - as long as you have the space for it.

make it hollow all the way through

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And finally this. The shafts for common bicycle hubs are already way too thin - the reason being using thin, weak bicycle dropouts. Assuming a proper frame, you can use a properly sized axle - 20mm in diameter and up, and then you can make it hollow to your heart's content - which also means it'll easily fit all the cables. But that means losing pedals, and a lot of people aren't ready for this conversation It would be technically possible to have a large diameter hollow axle inside the motor that ends with smaller diameter pins that go into dropouts, and the cable going out from the larger section - and that's kinda what the bigger motors already do.

Perhaps having the feed wires more vulnerable to heat damage saves the more difficult to replace coils in some cases?

Why does the wire have to go through the axle anyway? It doesn't on Grin's All Axle motor, right?

It don't need to. I suspect it is done to limit upsizing to larger wires/more amps

I just cut the phase wires an inch out of the axle approximately, then attach super beefy wires.. about 90% as good as replacing all the wire.

lnanek said:

Why does the wire have to go through the axle anyway? It doesn't on Grin's All Axle motor, right?
View attachment 367583

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Technically, it's still going through the axle. It's just that the axle is machined differently on that side and around an inch in diameter with a bigger bearing. So the cable doesn't need to go through the center of the axle. The bearing on the other side is normal sized.

Amusingly, just looking around my garage, there's also a Bionx motor here where the cable doesn't go through a hollow center axle:


You could probably get an old one quite cheaply since no one wants to open them up to run wires out to use an external controller when their Bionx kit breaks otherwise, like the battery dying.