I sometimes contemplate the irony of being born in and surviving the
dangers of the steam age, only to face the prospect of meeting one's doom
by being run over by an autonomous electric buggy or tripping over a safety
warning sign at a retirement home.

Tony P

On Tuesday, 27 July 2021 at 09:32:58 UTC+10 Matthew Geier wrote:

>

>

> On Tue, 27 Jul 2021 at 09:01, TP histor...@...> wrote:

>

>> I

>>

> Also, with the general preference for slung motors with gearboxes and

>> general lack of interest nowadays in having 100% adhesion for better

>> performance (thus contributing to that slow performance that's a hallmark

>> of modern light rail), most trams would be unable to use this Jacobs bogie

>> because it needs gearless hub motors and electronic (mimicked) "axles". The

>> general industry tilt towards cheap cheap eschews this sort of cleverness.

>> Also, I suspect electronic "axles" require pretty high standards of input

>> and maintenance.

>>

>

> An electronic diff is just software. We have a 4WD 'buggy' at work that

> uses hub motors and an electronic diff - and the motor controllers are

> standard off the shelf parts. The buggy is being used for autonomous

> driving research, and the builder of the buggy has dreams of selling these

> things to retirement villages and running a local bus service, ie you want

> to go the letterbox or the route bus stop, call for a ride, the buggy

> drives itself to your villa, you hop in and it drives up to the bus stop or

> letterbox (or 'club house') where you hop off and the buggy returns to the

> depot to top off the battery and wait for the next call.

>

> However, the problem with hub motors is unsprung weight. One of the

> reasons the Variotram's wheel motors fell out of favour is the rather high

> unsprung weight. They hammer the track and the motor bearings take a

> pounding. There is the same issue with hub motors on-road vehicles and

> probably why electric vehicle manufacturers are often using transaxles and

> mechanical differentials.

> And the Variotram has a virtual axle too - the traction converter drives

> the motors in pairs - across the bogie from each other and being 3 phase

> motors, the opposing motors are frequency locked to one another - this

> simulates (to a degree) the axle of a traditional bogie.

>

> Part of the VKUV patent is the clever arrangement where the hub motor is

> supported on the bogie frame and some sort of quill drive arrangement

> couples that to the separately sprung wheel. I've seen this in person in

> Pilzen but I was not allowed to take photographs inside the Škoda

> Transportation factory. (And they take their underframe painting so

> seriously that I was requested not to actually touch the undercoated

> frames, lest oil from my fingers mess up the final coating!)

>

>