Posts

Axle Box Cover part 4. Disaster and recovery

Image
I was really pleased with the results of engraving the axle boxes and I was in good spirits when I offered them up to the chassis this did not last long .... As you ca see I have machined them all at 90 degrees to where they should be :-( This was very disappointing I did take them down to my local model engineering club so everyone could have a laugh at my expense, luckily they were a bit more supportive than that. After several weeks of being glum, one of the members suggested cutting the covers off with a slitting saw. So I did! There was just enough meat on the slitting saw to remove the covers in one cut. This slitting saw is rigid enough not to be deflected during the cut. Plenty of swarf generated but I had lots of material to play with. Due to the low cutting speeds the cover did not fly off to the far corner of the workshop. As you can see there is a small curl of material still attached I had to file this off in the vice usin...
Post a Comment
Read more

Axle Box Timken Covers Part 3.

Image
Looking at the Axle Boxes on Oliver Cromwells tender there is a fifth stud which is not on the same PCD as the rest. This was the next job. Rather than use the centering indicator I opted for a simpler method. A machined centre! Distance from centre of cover (Y axis) was 4.7mm, PCD for comparison was just over 5mm so not a huge difference.  The X axis was set up by eye to be centred between the two lower holes.  Hole was started with a slocombe drill The opened out to 1.5mm to give a slack fit on a 12BA stud. These will sit proud of the surface unlike the four counterbored bolts. Now moved over to the Pantograph Engraver, I'd calculated a reduction in size of 6:1 but this left the Letter height too large. I've set it to 7:1 at the moment but might have a look at using a wider font to see if it matches the original better. Will try some test engraving I think before committing to the real axleboxes - not like me at all! The tes...
Post a Comment
Read more

Axle Box Timken Covers Part 2.

Image
A distinctive feature on the Timken covers is the four studs with accompanying nuts. I decided to add this feature to the axle boxes using dummy 12BA studs and nuts these would be glued into each corner. I ordered some 12BA nuts and bolts from EKP supplies and tried to figure out how to use the Pitch Circle Diameter feature of my milling machines DRO. After a bit of head scratching I realised the DRO has to be in ABS mode which is effectively the base measurement axis (the DRO supports different 100 axis or rather 100 different origin (0,0) points. Once I figured that out I used a centering indicator to line up the first axle box. Here I'm checking right to left its within 0.1mm Next job is to set up the DRO. Axis 00 selected (ABS Mode) The X and Y axis were Zeroed using the Xo & Yo Buttons. PCD Mode selected, Centre is same as ABS centre, hit down button. Pitch Circle Diameter is next, 14.27mm was scaled from a photo. Relative to the di...
Post a Comment
Read more

Axle box Timken Covers Part 1

Image
The axle box castings have dummy Timken Bearing covers cast in. These were quite rough and oversize so I have turned up a 19mm stub mandrel  from some scrap aluminium bar and cleaned them up. Axle box was super glued (cynoacrylate adhesive)  to the stub mandrel and left for 5 minutes to bond.   Front face had the barest minimum removed to clean it up. Diameter reduced to around 20.3mm, then length reduced to 7/16" (5.56mm) to match the drawings. I bought a box of shaped lathe tools from Myfords before they shut down the Beeston Site and sold everything off to RDG Tools. A quick rummage found a nice curved tool, it did need a bit of work with a stone to sharpen it but nicer than making one from scratch. Machining the rounded corner. The full size engine has a more gentle curve, but I have been true to LBSCs drawings, this will make it easier to Engrave the Timken logo on the front face. The valve on my chefs mini but...
Post a Comment
Read more