On Mon, 12 Dec 2016 13:11:03 +0000
Recliner wrote:
On Mon, 12 Dec 2016 09:39:45 +0000 (UTC), d wrote:
of the live axle, differential and half the prop shaft. Incidentally,
the units also include a reduction gearbox.

Christ, they must be heavy. Obviously a clever piece of engineering and I'm
trying to figure out how you can have a reduction gearbox with a hub mounted
motor because the whole point of the latter is the motor shaft is fixed to
the chassis while the rest of the motor is attached to the hub and rotates.

But these heavy buses plod along at low speeds in dense urban traffic,
so I don't think the unsprung weight will be nearly as serious a
problem as it would in a higher speed vehicle.

I suppose so.

--
Spud

On 2016-12-11 22:52:00 +0000, Recliner said:

The batteries are several tonnes heavier than an engine+fuel tank.

Didn't know that. Might explain why the MK battery buses allow fewer
standees (only 7) than the otherwise identical diesel versions (which
allow a crush-load - the number permitted is more than you would
physically fit on).

I wonder how, given the UK's generation profile, this affects their
carbon footprint?

Neil
--
Neil Williams
Put my first name before the @ to reply.

On Tue, 13 Dec 2016 00:52:00 +0000
Neil Williams wrote:
On 2016-12-11 22:52:00 +0000, Recliner said:

The batteries are several tonnes heavier than an engine+fuel tank.

Didn't know that. Might explain why the MK battery buses allow fewer
standees (only 7) than the otherwise identical diesel versions (which
allow a crush-load - the number permitted is more than you would
physically fit on).

Isn't there a maximum number of standing for diesel buses which is routinely
ignored anyway? Can't see the driver enforcing that 7 in the rush hour. Anyway,
surely the bus suspension and handling characteristics should be designed so
it can take as many passengers as a diesel of the same size?

--
Spud

In article , d () wrote:

On Mon, 12 Dec 2016 13:11:03 +0000
Recliner wrote:
On Mon, 12 Dec 2016 09:39:45 +0000 (UTC), d wrote:
of the live axle, differential and half the prop shaft. Incidentally,
the units also include a reduction gearbox.

Christ, they must be heavy. Obviously a clever piece of engineering and
I'm trying to figure out how you can have a reduction gearbox with a hub
mounted motor because the whole point of the latter is the motor shaft is
fixed to the chassis while the rest of the motor is attached to the hub
and rotates.

AC electric motors are very light compared to axles and transmissions.

--
Colin Rosenstiel

On Tue, 13 Dec 2016 04:24:59 -0600
wrote:
In article , d () wrote:

On Mon, 12 Dec 2016 13:11:03 +0000
Recliner wrote:
On Mon, 12 Dec 2016 09:39:45 +0000 (UTC), d wrote:
of the live axle, differential and half the prop shaft. Incidentally,
the units also include a reduction gearbox.

Christ, they must be heavy. Obviously a clever piece of engineering and
I'm trying to figure out how you can have a reduction gearbox with a hub
mounted motor because the whole point of the latter is the motor shaft is
fixed to the chassis while the rest of the motor is attached to the hub
and rotates.

AC electric motors are very light compared to axles and transmissions.

Not compared to a normal wheel though.

--
Spud

On Tue, 13 Dec 2016 11:44:51 +0000 (UTC), d wrote:

On Tue, 13 Dec 2016 04:24:59 -0600
wrote:
In article , d () wrote:

On Mon, 12 Dec 2016 13:11:03 +0000
Recliner wrote:
On Mon, 12 Dec 2016 09:39:45 +0000 (UTC), d wrote:
of the live axle, differential and half the prop shaft. Incidentally,
the units also include a reduction gearbox.

Christ, they must be heavy. Obviously a clever piece of engineering and
I'm trying to figure out how you can have a reduction gearbox with a hub
mounted motor because the whole point of the latter is the motor shaft is
fixed to the chassis while the rest of the motor is attached to the hub
and rotates.

AC electric motors are very light compared to axles and transmissions.

Not compared to a normal wheel though.

No, but a normal diesel bus also has the live axle, differential and
half the prop shaft as unsprung weight. The BYD site says:

"BYD's self-developed wheel-hub motor is adopted in the BYD ebus. It
is installed in the rear drive axle together with regenerative braking
technologies. Compared with a normal motor, the rear drive axle system
in the BYD ebus has no gear box, no transmission shaft, and no
differential mechanism. The power from the motor is directly
transmitted to the wheels, so that significant improvements are
achieved in transmission efficiency and reductions in noise and
vibration. In addition, the bus weight can be cut by 300kg, and
interior space is greatly saved."

http://bydeurope.com/innovations/tec...ndex.php#motor

I note that the reduction gear has a 17.7 ratio, and the bus has a
very low top speed -- 70 km/h (little more than 40mph) -- so the
unsprung weight isn't going to matter very much. You can see from the
illustration that the permanent magnet synchronous motor is inboard,
driving through the slim gear box that's between the motor and the
wheel.

On Tue, 13 Dec 2016 12:29:28 +0000
Recliner wrote:
differential mechanism. The power from the motor is directly
transmitted to the wheels, so that significant improvements are
achieved in transmission efficiency and reductions in noise and
vibration. In addition, the bus weight can be cut by 300kg, and
interior space is greatly saved."

Cut by 300Kg? Is that including the batteries? I doubt it.

Odd suspension design though. They had the opportunity to make give each wheel
fully independent suspension, yet they didn't bother, instead deciding to join
the sides by some sort of plate looking at that diagram. Quite why you would do
that when you don't need to baffles me frankly.

--
Spud

wrote:
On Tue, 13 Dec 2016 12:29:28 +0000
Recliner wrote:
differential mechanism. The power from the motor is directly
transmitted to the wheels, so that significant improvements are
achieved in transmission efficiency and reductions in noise and
vibration. In addition, the bus weight can be cut by 300kg, and
interior space is greatly saved."

Cut by 300Kg? Is that including the batteries? I doubt it.

Yup, me too.


Odd suspension design though. They had the opportunity to make give each wheel
fully independent suspension, yet they didn't bother, instead deciding to join
the sides by some sort of plate looking at that diagram. Quite why you would do
that when you don't need to baffles me frankly.

Having that bogie-like frame probably makes it easier to mount on the
chassis.

On 2016-12-13 09:41:55 +0000, d said:

Isn't there a maximum number of standing for diesel buses which is routinely
ignored anyway?

There is, but on most buses these days it is higher than a crush-load.

Can't see the driver enforcing that 7 in the rush hour.

I only had it brought to my attention by a driver having a loud
conversation about it and why he did enforce it because he valued his
driving licence - though in reality in MK crush-loaded buses are rare
as not enough people use them.

Anyway,
surely the bus suspension and handling characteristics should be designed so
it can take as many passengers as a diesel of the same size?

So you'd think but apparently not. Some must do, though, as the Red
Arrows would be a bit useless if they couldn't take a standing
crush-load.

Neil
--
Neil Williams
Put my first name before the @ to reply.

Someone who employs is an employer. Someone who is employed is an employee.