Wednesday, 19 September 2012

Salami Warning

As suggested last week, I've spent my shedweek machining the lever pivot castings or ankles as Mr. Middleton would probably refer to them. Recall that these are cast from p20 and then annealed to make machining easier. Actually, they machined quite well with carbide, but drilling with HSS is out of the question.

The first job is to machine the bore straight through the casting. I used a Keats angle bracket/plate. This mounts to the faceplate and is very useful when boring holes in round objects that can't otherwise be easily held. It's the perfect tool for these castings. When the casting is flipped around in the bracket, the bore will still be concentric, which means that both bearing surfaces can be easily machined into either end.

The Keats Angle Bracket - perfect for this job.

Both bearing races can be machined concentrically.

Testing that my formula works

The fork ends were not quite round after the cut and shut welding technique used to produce the tapered tube. To remedy this, I made a split clamping die with the appropriate tapered bore. Clamping this around the ends of the fork legs has cold set the first half inch of the tips to be perfectly round with the correct taper.

The split clamping die

Squeezing the fork ends to a the correct round taper took considerable force.
I used a long lever to tighten the vice.

Remount in the 4 jaw and centre.

Machine a plain bore the same ID as the through bore and 
then machine the tapered socket to match the fork ends.

Then drill and thread the holes for the oilers and then drill the holes with the unknown use. These holes are a bit of a mystery, they are either for lamp brackets or foot rests. Some bikes have them and some don't, it's also not an early versus late model thing either as I've seen early and late versions both with and without them. The versions without use simpler, symmetrical castings. I have woodcuts of faciles with twin lamps down in this location, one per leg. Also note the photo at the top of this page, it has footrests, although not sprouting from this location. The example I am copying has the holes and a lamp bracket on the head. As I said, a bit of a puzzle. Does anybody know the answer?

The castings are now more hole than casting, the weight for the pair before machining being 1lb 3/4oz (~ 0.475 kg). They are now a Svelte 7oz (~ 0.2 kg)

Finally, clean up some of the casting seams and roughness from the outside. They are now ready to be nitrided before brazing on, although I do need to make a suitable jig to hold everything square whilst I apply the heat.

In other news, on Sunday we all went for a bike ride, the route selected being the Tuhaitara track between Woodend Beach and Waikuku Beach with a detour to the cafe at Pegasus for a coffee. As usual my daughter was on the tandem with me.

Whilst at Waikuku playpark, somebody decided to test the tsunami warning system. Which is right next to the playpark. And very loud.

Instead of sirens, the system uses large speakers. The following text is followed by a series of unpleasant, raucous squawks.

This is a tsunami siren test.
This is a tsunami siren test.
It is only a test.
Do not be alarmed.

Repeat until deaf.

Actually, it was good to hear. There was some talk when the system was built that it wouldn't be loud enough. I beg to differ. My daughter then spent the tandem ride home happily chattering about the new Salami Warning System.

Also this week my lovely wife and I celebrate a significant wedding anniversary. Which reminds me

What's the longest sentence in the world?

"I do"

It's a good job that she doesn't read this nonsense.

1 comment:

  1. I just ran across this trick for making a straight knurl with one wheel from a diamond knurling tool: