S stock delivery & introduction - discussion

So when are they scheduled to start operating? I read somewhere that they want to start doing the Wimblewares in December

Can anyone tell us the train numbers that will be formed of S7s on the H&S and Circle from 19th of May please?

MTIA

If it was 21335 it was delivered last Thursday so there shouldn't of been any engineering work happening unless it was overnight work

How are they then transferred to Hammersmith? (or Neasden as the case may be)

It would have needed a pilot loco, as the S7s don't have the central ATO system

The S7s transfer from Ruislip to Neasden like this:
Ruislip->Ruislip Siding (REV)->Harrow OTH (REV)-Watford (REV)-Neasden

I would imagine quite long. I think the Croydon Trams are still on their original concertinas,and they do alot more flexing (especially in and around central croydon), and the oldest one is 15 years old. Even if they were replaced during the tram's refurbishment that would still have seen them carry out at least 10 Years of service, so I would expect the S stock ones to last probably the train's lifetime. Don't forget that they will also have been made with this design consideration in mind.

I would assume it is becaus the size of the contact patch (the area where the wheel is in contact with the rail) is related to the radius of the wheel. For a perfectly circular wheel and flat rail the contact patch would be a line of infintesimal width (and therefore zero area) transverse to the direction of travel, (and the zero area means the pressure would be infinite) but in practice wheels and rails distort under the weight of the train so that the contact patch is typically about the size of a 5p piece. To achieve that size, a smaller-radius wheel needs to be distorted out of a true circular shape by a greater amount than required for a larger wheel, putting more tensile stresses on the wheel (or, for the same force, the contact patch would be smaller, leading to less adhesion).

(The really enormous driving wheels used on steam trains were required as they had no gears - the larger the wheels the higher the gearing, which is why express locomotives had much larger wheels than freight ones where getting the thing moving was more important than outright speed).

Duplicate post, Mods please delete.

Also,smaller radius wheel magnify the effect of bumps in the track more than larger ones.
I don't really understand the maths involved,but it is to do with the ratio between the size of the "step" in the track to the radius of the wheel.
Try pulling a loaded small-wheeled trolley up a kerb,then try shifting the same load with a large-wheeled barrow up the same kerb.

I know I must be missing something here but why can't the S7 stock transfers from Ruislip to Neasden go straight into Neasden from HOTH? Why reverse to Watford first?

Its all to do with the 'angle of approach', the larger the wheel the lesser the angle.

Eagerly waiting to see if this is the start of the 'real' replacement of the C Stock with S7's or whether this will be yet another damp squib and we'll be told it will all happen after the new WTT in December.

So, we can look forward to spending this coming Christmas expecting the full scale introduction to start in May '14.

If we continue the trend for the last 4 half years.