Gallery, Projects and General > Project Logs
Fixing the how NOT to make an engine
bogstandard:
This is a bit long after the original repair, but I am trying to juggle time in my shop and keeping a very inquisitive visitor happy.
Ralph's visit this afternoon (he disturbed me from my afternoon power nap), gave me the push I needed to carry on with this post. He wanted to see how I used a co-axial indicator. I don't think Ralph learned how to use it because it was such a short demonstration, but I think he went away with an understanding of how and why it is used, which is half the battle. Maybe another time Ralph.
So onwards and upwards as they say.
Using my coaxial indicator, I centred up the RT to the quill.
Having previously turned up a holding mandrel on the lathe, and without taking it out of the chuck, the chuck was unscrewed off the lathe, and screwed onto the matching thread on the RT. This put the mandrel on the centreline of the quill.
The RT was set to zero on it's angle scale, and the machine DRO was zeroed up all round. This is showing it in metric, just after this, I reset it to read imperial, as that is what the drawing calls for.
The X axis on the mill was locked up, as all movement for this operation will be done on the mill Y axis and the RT degree scale.
The casting was dropped onto the mandrel but it was not tightened down, yet.
This is the method I use to make sure that the holes are drilled perfectly in the correct position around the cylinder pivot, even though the pivot centre and the crank centre might be slightly out. This will automatically ensure that when the cylinder swings from side to side, even if the centres are slightly out, the holes will line up perfectly with the ports in the cylinder (assuming the holes in the cylinder are on the centre line, which on this engine, they are).
This shot is taken slightly from the side to show what is going on.
I mounted up a bit of rod, the same diameter as the crank hole into the chuck. By moving forwards on the Y axis only, disregarding what the readings were, I moved it forwards until the rod slipped nicely down the crank hole.
Then I tightened up the screw to lock the casting onto the mandrel. So now I had the two centres perfectly aligned down the Y axis. The rod was withdrawn, and the Y axis was wound back to the zero position.
This is what is required on the drawing. The PCD is 15/32", so that was halved, giving 15/64", and the Y axis moved forwards by that amount.
As shown on the DRO. The Y axis was then locked up. All work now is using the RT and the quill.
As can be seen from the drawing, there is a spread of 38 degs between the port hole centres. That means 19 degs either side of the centre line.
So a quick calculation gave me settings for the RT. 19, 161, 199 and 341 degs. 19 degrees either side of the 0/180 deg centre line. A quickie centre drill at those setings, followed by drilling down thru the silver soldered plugs, until the correct sized drill hit the previously drilled ports.
Once one side was done, the same thing was done on the other cylinder pivot point by repeating the exercise.
I took this shot on an angle to show how the new holes join up with the previously drilled out of position holes. It doesn't matter that they are not quite in line, the steam will find its way thru. The main thing is that the holes on the surface bearing face are in the correct position now.
I think the next bit will be the rescue of the cylinder bottom plate/bearing and piston/rod, as they should all be made as a matched set.
When, I have no idea. A contract job is waiting in the wings and the delivery date is getting close. I have now got all the materials together, so that must take priority.
Bogs
Darren:
You just had to throw fractions in didn't you...... :doh:
Quick calculations.....umm....for some eh.... :lol:
bogstandard:
I can't help it Darren, that is how the drawing comes from my favourite casting supplier, by using fractions, it shows just how good they really are, not.
Get yourself a ZEUS book, and that takes care of all your problem conversion calculations for you. But you do need to be able to read first :lol:
Once you get to using your RT, you will totally understand what I was on about.
0/360+19=19, 180-19=161, 180+19=199, 0/360-19=341
John
Darren:
I think I get the jist of what you are doing John....
Just to prove that I have been reading your last sum is wrong, but I know what you meant :thumbup:
bogstandard:
Darren,
When you use a RT, your zero point is actually 0 or 360, 360/0 being the start of the journey around the circumference, 0/360 being the end of the journey.
Because it was the end of my journey, I used 360. So 360-19= 341 degs.
That is just the start of it, wait until you get to the minutes/seconds vernier scale. That is why, when I have to start working it all out, I take the easy way out, and fit the dividing plates on and let them take care of all the calculations. Unfortunately, your RT doesn't have that facility, so you will need to do it the hard way.
John
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