First day at Northfields

Excellent Seth!

I am very glad to hear you are enjoying your work experience, all the best of luck.

Keep us updated with how things go.

Glad you had a good first day.

Given the amount of dirt there is under trains the phrase "Happy as a pig in brown stuff" springs to mind. ;D

Your captions are OK.

BTW - isn't it time you changed your avatar for something more appropriate?

That would have been the RPA, or Rotary Pneumatic Accelerator. Like Ronseal, it does what it says on the tin ;D It rotates, using main line air, to accelerate the train. It does this by starting with all the resistances in the resistance grid in circuit. As the train starts to move, the motors can take more current, so the RPA turns one notch to take one bank of resistances out of circuit, thereby increasing the amount of current going to the motors. This continues until all the banks of resistance are out of circuit, and the motors are receiving all the current. One thing to note, some stock, including the 67, 72 and C stock use 2 RPAs, one for winding up to series, and the other for winding up to parallel. Other stocks only use 1 RPA. I'm not sure whether the 73s use 1 or 2, but I'm sure someone on here WILL know

Well done Seth. Wait till you have to change brake blocks!

There's something ticking away in the back of my mind that seems to think that 73s were the first to use a single camshaft and is one of the reasons for low reliability when first introduced.

BTW - on other railways that use/d the device they're known as the camshaft, 'cause that's what they are.

Sorry Mr PP but I thinks you is mistook. Without being pedantic all stocks up to and including 1962 TS used a single camshaft RPA. Prior to 1935 all stocks had either Accelerating relays or Potentiometers. Or have I misunderstood your last post?

Bookmark this page everyone - an admission of fault/failing memory from PP - doesn't happen oftenj (ever?).

Glad the Work experience is going well - we all look forward to further accounts from northfields Depot I'm sure!

I had a go with one today - there are some interesting announcements which you don't hear all that often! I must have gone through all 25 of them, and I only recognized about five!

I also made the mistake of making it do a 'Walk through' . I must have driven the entire depot completely mad ;D ;D

Ahh - I should have been more explicit in my post. What I SHOULD have said is that when the 67 stock was introduced, using rheostatic braking for the first time on LU, then 2 RPAs were used, as it was the only way they could do it at the time. As technology improved, and experience was gained, so it became possible to use rheo braking with a single RPA. As has now been confirmed, it was the introduction of the 73 stock that allowed the rheo to be used with the single RPA.

So I wasn't completely wrong after all. ;D

Funny that! I seem to remember asking my I/O what it did, all he said, never touch it, as it goes on for quite a while!