Stevebr

On my copy the 94xx is on page 98. Haven’t read the magazine but on a quick flick through it looks a good issue

This is looking pretty cool. Looks like a January project for me

This looks really interesting. Please continue

1N4001 diodes drop 0.6volts across each so 8 to 10 in series would drop the voltage

My grandfather, also GPO did exactly the same

After finding the last issue a bit average this is a really good issue which I read cover to cover (well the electronic equivalent)

That looks really good. Care to share the construction details. In term of spacing the lighting was generally much poorer than would be acceptable now. Based on my dim(!) memories no closer than 25 yards apart but happy if anyone has more knowledge

It looks like it could be a surface mount diode or perhaps a transient voltage diode (TVS)

I use RS components who have an extensive reasonably priced and easy to order selection. Try code 320-203 or similar. There is a detailed data sheet available. Delivery is excellent

Hi, Thank you everyone for the great insight. The issue around the 4th gear ratio appears to be 1:1 as it it shown as a direct drive with no reduction being shown (source railcar.co.uk/Technology/Gearboxes/Gears) and a document from the Western Region CMEE available at Silvermoon consulting. I did notice when looking at a picture of the DMU rev-counter that it was marked between 1100 rpm and 1800 rpm (as expected) but that it was calibrated to 1950 rpm which would give a theoretical speed of around 73mph on new wheels and 70 mph on worn which looks about right. I can definitely

Gravity plays a part definitely but the RPS archive shows many class117 units exceeding 70mph out of Paddington on the level. I do have a vague recollection that the rev counter was marked to change up at 1800rpm but was calibrated further (1850? or so)

Can anyone confirm the 1.1:1 ratio. In some publications it is shown as 1.1 and others 1.0

As I recall the 1st generation DMU's had a top speed of 70mph. If I use the maximum engine rpm of 1800 it equates to around 66-67 mph with new 36inch wheels. Did the engine operate beyond 1800rpm (my docs indicate it was governed to 1800) or are my assumptions wrong? I definitely remember them achieving 71-72 between Swindon and Kemble in the 1970's

I recall seeing them very occasionally at Gloucester. Didn’t usually stay that long before returning to Midlands

Try https://signalbox.org/~SBdiagram.php?id=%20270