Sunday, 13 March 2016

Let's get these bolts fitted...

Quite a lot of progress with 828 in the last few days. Most of the attention has been on the RH Driving Hornblock where we need to true up the bolt holes in the frame and the horn block casting. One disadvantage of inside cylinder locos is that the piston thrusts are transmitted through the axleboxes and the hornblocks. On a loco like 828 each piston thrust may be as much as 12 tons so the bolts need to be a tight fit. Because the bolt holes have been progressively opened out at different times in the long life of the loco it's important that we remove as little metal as possible when truing up the holes. This meant that it's better to do it with an expandable (adjustable) reamer driven by hand. It is excellent exercise....then having reamed the holes truly circular and parallel we need to make up bolts that are a very precise fit in the holes. The bolts need to be slightly bigger than the holes and driven into place using a heavy hammer. In our case the bolts, properly known as fitted bolts, are manufactured in the shed machine shop by Mr Nathan Lightowler who can turn them up from hexagonal bar stock in a very short time - and every one is a perfect fit...!

John Greig has carried on white-metalling the remaining eccentric straps and these are now all ready for machining in the lathe and then hand-fitting them to their respective eccentrics. The eccentrics themselves will need to be dressed and polished to ensure there are no rough surfaces to tear the white metal.



Starting to ream out the bolt holes with an expandable reamer and a big tap wrench...


eight holes reamed circular and parallel ready for the fitted bolts.

Nathan Lightowler machining the first of the fitted bolts......only 43 to go after this one, Nathan...!

The first fitted bolt alongside my calibrated lunchtime orange...
The first eight bolts driven home.....

The hammer that drove the bolts home.....they are a tight fit...!





View of the bolts from inside the frames...

Crankaxle moved down to the machine shop awaiting fitting of the big end bearings and the eccentric straps - all newly white-metalled by John Greig
General view from the new mezzanine floor...828 crankaxle, 5025 bogie and main springs plus No.17 "Braeriach" just crying out to be converted into the 0-6-2T that Eric Cooper had always intended....!!!!!

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