Saturday, 19 March 2016

Reaming, Reaming, Reaming.....

This week's work on CR 828 has been mainly about reaming bolt holes and trying to avoid as many steel skelfs as possible... Nathan Lightowler has also been very busy machining fitted bolts for the RH Driving Hornblock. He's also progressed the machining of the new steel casting for the LH Driving Hornblock. We had a bit of a disappointment when it became clear that despite Nathan's very best efforts the Shed milling machine just doesn't have the capacity to handle the new horn block. So rather than struggle on and perhaps get an unsatisfactory result we took the decision to send the casting out to a suitable third party machine shop. The silver lining to this particular cloud is that it frees Nathan to tackle the machining of the big end bearings and the eccentric straps. We plan to crack on with this during week commencing Monday 21st March. Once the machining is complete there will be a lot of hand fitting to get the components bedded properly to their respective crank pins and eccentric sheaves.

A welcome sight..! The RH Driving Hornblock now fully bolted to the frames. The new bolts were made a slight interference fit and then driven into the holes using a seven pound long handled hammer. Hopefully it will be a long time until they are next removed...!

With the RH Hornblock refitted it was time to make a start on truing-up the holes in the LH Driving Horn where we had to make a weld repair to a crack that ran through several bolt holes. The Welder did a great job in trying to preserve the holes during the repair and it was possible to ease them back into a circular section with some filing and then the trusty reamer. There will be no need to anything more here until the horn block casting is lifted into position.

All the holes in the leading edge of the horn are now reamed circular and to the same size...

This object is the horn clip that bolts onto the underside of the RH Driving horn. It has two main functions. 1) It ties the open ends of the horn block together to give the structural rigidity necessary to resist the powerful thrusts of 828's 18 1/2" pistons. 2) It transmits the weight of the locomotive to the suspension springs on the crankaxle. In total the crankaxle carries about 18 tons of the loco's weight so the horn clips on either side of the loco carry about 9 tons each. The circular holes in the clip are for the spring hanger pins that connect to the axlebox. In this view we are looking at the top surface of the clip. The square holes at each end are for the studs that carry the large nuts that clamp the clip to the hornblock. 

This view shows the side and the bottom of the clip. The seatings for the springs are the two large circular recesses. The clip weighs about 35kg and is made of cast steel. It looks a strange colour because it had just been removed from the Shed sandblaster. We decided that it would be a good idea to get two new clips made and these will be produced in the next week or so by Blantyre Castings who manufactured the new horn block a few weeks ago.  

The weather in Strathspey was very sunny and warm during the week and here is our old friend enjoying a view of the Spring sunshine......hopefully it won't be too long till she'll be back out enjoying it....

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