Tender Chassis

November 2013

The big news so far this year is the commencement of the trial erection of the new tender frames.  This is a culmination of a couple of years of effort at preparation, and is really the first tangible sign of significant progress with the build of the new tender.

Frame plates ready for lifting

Frame plates ready for lifting

Before we could safely lift the frames into position, it was necessary to improve the floor in our workshop to allow the use of a gantry crane.   We thus had to cast two concrete strips suitable for the crane wheels, and this can be seen in the picture above.   Some means of non manual lifting was going to be essential for the erection of the frames – each main frame plate weights 800kg, which is obviously vastly beyond what can be safely lifted by hand and muscle power alone.

Main frame plates lifted to vertical

Main frame plates lifted to vertical

We are constructing the frames upside down, as this allows easier access for trial assembly and drilling.   The frames are temporarily sitting on two cross beams (seen in yellow) which have been levelled in both planes, as it is essential that the frames are constructed ‘true’ and square.

Frame erection progressing.  The inner frame plates can be seen between the main frames

Frame erection progressing. The inner frame plates can be seen between the main frames

The frames were set to the correct ‘back to back’ dimension by installation of the lower cross-stretchers (the red items which are clamped in) and by the use of two purpose machined temporary spacers (the yellow tubes).  Once this was done, the correct relative position of the frames was checked by ‘tramelling’ the diagonal dimensions between the centres of the axles, and moving one of the frames forwards or backwards to correct any error.  This took some time to do, as multiple measurements and a certain amount of trigonometry was required.

Front of the frames with dragbox installed

Front of the frames with dragbox installed

Once the frames were correctly set – the cross stretchers were drilled and fitted with tap fit bolts – thus ensuring that the relative position remained fixed during all subsequent operations.  After this the front dragbox and buffer beam were installed and similarly drilled.   Following this, we then proceeded to install and drill the angles which run for the full length of the frames, followed by the rear dragbox and bufferbeam.

The rear buffer beam and dragbox in positoin

The rear buffer beam and dragbox in position

All this work has to be carried out very accurately to ensure that everything is correctly located.  Even the smallest errors could result in problems later on, so we are taking our time, and measuring once/twice/three times before drilling…!

George drills holes in the tender frame top angle

George drills holes in the tender frame top angle

The frames will be fully riveted construction, and thus there are many hundreds of holes to be drilled…  Anybody who makes the mistake of walking into our workshop is likely to get collared for drilling a few holes…!

 

To be continued….

 

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