7 Transfer Manifold I realise I am falling way behind with this build log, steady build progress is being made but I am way behind with the postings. I will attempt to catch up
The last major part of the two stage supercharger to be made is the horse shoe shaped transfer manifold which connects the larger low pressure compressor to the smaller high pressure stage. On the full size engine the transfer manifold was on integral parts of the two supercharger housing, which required very elaborate castings in magnesium alloy. I am machining my engine from solid billets of aluminium as there are no castings available. I am attempting to machine a very 3 dimensional object from 2 dimensional drawings on 3 axis milling machine. I needed to carefully consider how to machine what is basically a curved hollow tube and how to make it fit the existing supercharger casings.
To help me visualise the transfer manifold, a friend made a Solidworks 3D model from my drawings and quickly 3D printed something for me to play with.
This printed part was a great help in planning the machining steps. The transfer manifold consists a left and a right half, joined at the centre by a large pipe clamp. I decided to machine both sides joined together in order to maintain their correct alignment and to separate the left and right halves after all the machining was complete. I was able to design the hollow transfer manifold as two hollow shells to be bolted together with hidden screws. I would use the same grade of aluminium alloy for the manifold and for the fixing screws.
Here you can see the first stage of machining the internal contours of the rear half of the transfer manifold. You can see the small lands which are designed to accept the hidden screws which will hold the two halves together. The process is the same as before, start with a big block of aluminium and convert most of it into small chips and hopefully an engine part will emerge.
Part of the outside profile was also machined without disturbing the set-up. The wall thickness of the shell is about 1.5mm.
The rear half of the transfer manifold is offered up to the high and low pressure compressors. So far, so good
The front half of the transfer manifold was machined in a similar manner to the first. The two halves were glued and bolted together using bolts made from the same material as the manifold. A lot of hand filing was then required to complete the outside shape of the assembled transfer manifold. The fixing screws blended in and were lost from view during this process. The low pressure (the far side) of the manifold was a sandwich of three parts while the high pressure side was made from two halves.
The supercharger cooling fins were carefully filed away from the two compressor housings where the transfer manifold would eventually fit.
The transfer manifold is made to fit snugly onto the two compressor housing before the mounting bolt holes are drilled.
M3 cap head bolts are partially buried in the mounting flanges.
The left and right halves have been separated at the centre point. The rubber band was used to hold the two halves in position while the mounting flanges were being worked on.
I was very relieved to have got this far without too many problems. The transfer manifold is a very prominent feature at the front of the engine and therefore needs to look right. I would not have wanted to redo that part.
Time to relax and enjoy a nice cup of tea.