Dave Stilldrillin' was in a bit of a quandry.
Having destroyed his original displacer for the engine he was restoring, whilst trying to repair it, and subsequent efforts to get a replacement to fit, to no avail, I stepped in and offered to make him one to the dimensions he would supply me. This is the story of that journey.
This is the info that was supplied. More than enough to make the part, and I had free reign with some of the figures.
Not having the want to start to do any spinning at this time, I decided to work from the solid, and if I did things right, no problems should occur.
So grabbing a bit of brass bar end, it was soon faced off and taken thru the usual state of drilling out to remove most of the internal metal.
Next came the boring out to width and depth.
If you notice, all the work on this part is done OUTSIDE of the chuck jaws. Once you start to get thin walls and boring out inside the jaws, problems of distortion start to occur, and it is very easy for something to 'grab' and start on a journey of destruction. I think that is what happened to Dave's original.
Once the internal bore was to size, a small recess was put in to take the later to be fitted top plate.
All things had been calculated out to have 0.030" thick walls, so it was then turned down to size. It 'sang' a little as I started to get thinner and thinner walls, but by taking it steady, I managed to keep the chatter marks at bay.
This is the first time I had used my deep parting tool since I repaired it, and it parted off with no trouble at all, leaving a 0.040" thick base.
After a bit of a clean up, the 'cup' was ready to have a top made for it.
I piece of 0.060" thick brass plate was marked up roughly with what was needed.
Cone drills do a great job of drilling thin sheet, and this was no exception, hole spot on size and no distortion.
A quick date with Mr Bandsaw had the rough circle cut out.
To make things easier for me, I used a special bit of kit, an expanding mandrel. I also used my recently made 'nudger' tool for getting it perfectly straight.
A gentle bit of outside turning had the lid spot on size. I don't want a gap for silver solder penetration, I am going to do all the joining for this part on the surface.
I cut a chamfer on the top edge for the solder to sit in. It can't be seen very well here.
The mounting 'cup' was then made, and this will be silver soldered first to the under side of the lid.
This shows the top face of the lid and how it will look. You can see the chamfer much better in this shot.
BTW, the reason I don't want the solder and flux penetrating inside the displacer is that I won't be able to clean it out after soldering. By keeping it on the surface, I will have no trouble cleaning things up.
Silver soldering in the cup. The usual practice of flux up, a ring of solder wire and heating from underneath until everything flowed.
I forgot to take pictures of the rest of the soldering up, so here is a shot of the finished item after just a little clean up.
I now needed to remove 0.010" from both the top and bottom faces of the displacer, to get them to the correct thickness, and to remove excess silver solder from the top face.
For this exercise you need as much support from the chuck jaws as possible without massive gripping power that will distort what you have already done, so out came the soft jaws, which were bored to fit the displacer perfectly.
By gently gripping the part in the chuck jaws, the faces were skimmed up and finished off with a bit of fine emery.
After finishing off the displacer, a stepped 3/16" rod was made to the correct length and to fit the thread I had machined into the cup (4mm)
The finished article.
I just hope it works OK
Bogs
