Update from Saturday 21st July.
With contributions from Ian Robins, Terry Deacon, Janet Royston, Paul Conibeare and Glyn Warren.



On Saturday we had a few issues with D6566 sadly as Ian has reported below. The loco failed, but was quickly
and efficiently replaced by recently overhauled Class 14 D9526 which took over the remainder of the Diesel
Driver Experience Course.

Meanwhile on Monday 23rd July Hymek D7017 left Bishops Lydeard bound for the Gloucestershire and
Warwickshire Railways diesel gala this coming weekend (27th-29th). She will be a popular attraction appearing
alongside former Williton resident Warship D832.

Ian takes us through the technical explanation of what happened with D6566.
Whilst in use on Diesel Experience Course duties on Saturday 21st July, the loco unfortunately experienced a
battery explosion whilst on the climb of Washford Bank.
This resulted in the loco being failed on arrival at Williton and was replaced by D9526.
Some significant damage has resulted not least to one of the battery boxes that has been badly distorted and
the door has yet to be found!
It is likely that a new battery box will need to be manufactured.
A new battery has been ordered and should be delivered in the next week or so.
Investigation revealed that a spring washer had become trapped between the two heavy AGAZ lugs in the
Auxiliary Generator (AG) connection box.
Even though the nut had been correctly tightened down this had resulted in the lugs being held apart by a
miniscule amount that was not visible.
But the resulting small contact area caused overheating and eventually burnt through the smaller cable that is
the negative reference to the AG Automatic Voltage Regulator (AVR).
This caused the AG output voltage to go very high and overcharged the batteries, hence the explosion.
Also, the Battery Charge Resistance was severely overloaded and caused at least three of the elements to
burn out. These will need to be replaced and it is likely that these will come from another preservation group
unless a resistor manufacturer can come up with some direct replacements.
On Sunday, Thomas disconnected the remainder of the damaged cells and flushed out the battery and cell
boxes to get rid of any residual electrolyte.
I managed to dismantle the AG connection box and it has cleaned up satisfactorily.
That will hopefully be re-assembled this coming Saturday.


First four photos from Terry showing the Class 14 in action.
Then we have some photos of the Hymek being carefully loaded by Janet and Paul.
We then have some photos of the various electrical components described in Ians report.
Finally a selection of Gala photos from Glyn Warren.