Thanks Guys
I've been a bit side tracked: the weather has been horrible and I have just started a couple (yes 2 at the same time
) of rather nice new cross stitch pieces that have been taking my attention. But today....
If you recall the valve would not fit inside the steam chest so it needs opening up. Hand filing is easy and quick and is less likely to break an expensive long reach milling cutter. I chose to use the mill:
The valve rod guide/gland needs to be added to the steam chest. I have turned up a piece of bronze 8mm diameter and cut the thread using a die.
It is easy for a die to start out of line so you can see I am using the drill chuck against the back of the die holder to keep the die square. You can also use a dedicated tailstock mounted die holder to do the same
I have drilled the centre of the guide 3.8mm for a 4mm diameter shaft and used a countersink to form dip around the end of the hole to encourage the steam packing to go towards the shaft rather than just squash under the gland nut.
And also need that gland nut. This is nothing special just a piece of brass hex with a 3.8mm hole through it but we want the internal thread to end nice and square so I am using a home made D-bit to cut the 7mm hole:
The thread is cut with a tap which is supported from the tailstock to make sure it goes in true:
With that ready to go I can use a wobbler to find the centre of the steam chest and the lower edge
from which I stepped up 9.5mm and drilled 7.0mm and making sure the tap went in true tapped the hole for the same thread as the spindle guide.
The guide has been loctited into the steam chest, which will require 24 hours to harden. But as on this it has a locknut everything is firm enough for me to put the gland nut in place and ream through the guide and nut together. You can also see that the spindle is along the centre line of the steam chest:
We now know the height of the valve spindle so it is time to centre on the valve:
and drill it 4.1mm for the 4mm diameter spindle:
Notice this is not a tapped hole
this is clearance as we want the valve to "float" and for the steam to push the valve against the port face. This is one of those horrible designs that uses two nuts on either side of the valve:
This makes timing the engine a right pain as you cannot just drop off the Eccentric road and give it a twist
you have to faff around with little spanners inside the constrained steam chest area. Lets slide the valve on the spindle and check the side clearance:
Missing Photo
of it all mounted on the engine
The next bit I am going to think about is getting the crankshaft in place. The reason for this is because it allows us to line things up. This engine came with two cross head castings and one main bearing casting
this means I need to make two replacement main bearings. Yes
two not one. Why? Because both bearing need to be made of the same material so that they wear evenly. As I am a skin flint I have knocked up three pieces for each bearing:
The hole through each is on the centre of the crankshaft and I am using it to align the three pieces for the purpose of silver soldering them together. Before threading them onto a piece of dowel I am applying silver soldering flux to one of the faces:
I did this by dampening the surface and dabbing the damp face into my pot of flux. I should mention at this point Silver Solder flux is Poisonous so no finger licking until after you have washed your hands.
Over to my heating hearth. These are large pieces so I will be using a large nozzle on my propane torch and I have put those two large lumps of metal behind the two bearings to reflect the heat back on the pieces. The first requirement is to heat the pieces so that the flux does its job i.e. it cleans the surfaces - it normally bubbles a bit. I then will waft
the silver solder in the flame to warm it slightly and dip that in yet more flux. The idea is to heat the work such that the silver solder will almost run round the piece without the gas flame, rather than using the gas flame to melt the solder. If you get the temperature right the solder will whizz all the way round the joint:
Once cool they can be removed from the hearth using a pair of pliers:
Never assume they are cool enough to handle with your fingers
These can then be cleaned up. I normally leave them in a pickle tank for the time it takes to have a cuppa before washing them off with cold water and giving them a light wire brushing:
We are ready to go. But that will be another day as it is time for some more cross stitch
Jo