Monday, September 21, 2015

How I increased the offset of my GRS whitemetal flycranks

Recently, I converted the last of my track powered locomotives to battery power (see How I converted my Fowler diesel to battery r/c). Fowler(ish) Loco No. 7, Tollemache, was the first loco which I scratchbuilt and so has particular poignancy for me (see How I constructed an early Fowler diesel locomotive).

During the build, I had a major problem with the layshaft. The only flycranks I could find (from Garden Railway Specialists - GRS), had 8mm offsets but the cranks on Tollemache's drivers had 10mm offsets. I solved the problem at the time by slotting the connecting rod to compensate for the 2mm differences at each end of the rotation.

This, of course, meant the motion was very sloppy which was especially notable when the loco was running at low speed. I don't have any video of this - I wonder why.....?

 I searched websites of various suppliers (eg GRS, Essel, Roundhouse, Brandbright) to see if anyone was marketing flycranks with 10mm centres, but to no avail. I considered making my own from brass, but precision metalworking is not one of my strengths. Then, inspirationally, I remembered that I had recently acquired skills in soldering whitemetal (see How I constructed an IP Engineering Plate Frame Simplex). The GRS flycranks were whitemetal.

The head of the crank was excised with a razor saw.

The ends of the two pieces were coated in flux, tinned with low-melt solder and then joined together with a 2.5mm fillet of solder (0.5mm to allow for the width of the saw blade).

The solder was then filed to shape - et voila, one fly crank with 10mm centres!

The slotted connecting rods were discarded and two more connecting rods cut from brass strip. These were then bolted on to the wheels and to the new flycranks which had been quartered and fixed on to the layshaft with cyano gel.

 The motion is now a lot smoother and so I am more than happy to video the loco moving slowly while, for example, shunting in the Copper Mine sidings.


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