What to do on a rainy day.

When the rain falls, there ain't a whole lot to do 'round here. UNLESS,,,

Your Dio.

While I can't do any casting today; or for another week while I am waiting for my new crucible to come in, I decided that wasn't going to hold me back from doing something else.

There are parts for the stirling motor that don't need cast. Actually casting them would probably be bad. Far too many stresses to be absorbed by said parts. One, the crankshaft. Never made one before and I have a few ideas on how to go about it. In this case, I decided to do an assembled shaft. One where the components are made separately, then assembled in a, more or less, permanent fashion. I thought about welding it but the parts are so small that my welder would turn them into a puddle pretty quickly. That left either brazing, or silver solder. I decided to go with the solder as it is fairly easy to use without having to use near the amount of heat that a braze would. Also, glad I did too, since I have to take the danged thing apart again. Looking at it, I decided the shafts are just a tad too small for what I want. The main shaft in the pic is 1/4" and the crank arm is 3/16". There is also a slight imperfection in the alignment that I didn't catch until I had the main shaft cut. I will be upgrading the shafts to 3/8" and 1/4" respectively.

Now, How to go about building a crankshaft out of your scrap bucket? First, you have to have an idea

This is my wooden mockup using brass as the mainshaft and crank arm. (the connecting rod is actually my blank for when I go to cast them)

Then you have to figure out how to do things consistently. In this case, the actual crank weights will have to be identical.
This is my jig for 'machining' the bottom of the arm. Both pieces are held together by a brass pin that I hammered inplace on the top of the crank. The 1/4" bolt is actually the guide in this case.
Here is the jig being used on the grinder to shape the bottom of the arms.
I tried to mill this part but the stresses induced by the mill were threatening a broken tool. This actually worked better and faster so it is a technique I WILL remember.

Shaping the top portion was a bit easier since I had the two holes in place and these were straight cuts. I bolted the two pieces to another chunk of metal that I drilled and tapped to the right sizes, this was then mounted up in the vise on top of a set of parallels and machining commenced. The top curve was eyeballed on the grinder in similar fashion to the bottom edge though I didn't use the jig in this instance.

Here are the finished arms.



This is how to set up the shafts for soldering (in this case.)

Note how the shafts go completely through both sections. This is to maintain alignment. As I found out though, even 1000th of an inch play in the holes is enough to throw the whole mess off quite a bit. There is a very pronounced wobble in the end shaft. Either my shaft was bent or it developed one while I was heating things up or I didn't have things as straight as I thought. More than likely the latter.

And the 'soon to be taken apart and remade' crankshaft. (like my cheapo v-blocks?)

But this is only a start. I have never done this before, and I am learning in leaps and bounds what to do, and more importantly, what NOT to do. Always a better option than staring at the propaganda machine and stewing about how the rat bastards continue the box of lies.