May 2021
In desperation I’m going to use a 10inch solid cast iron wheel as the starting point of this effort and a taste of things to come!
I like slow running long stroke engines and so this one is going to have a bore diameter of 30mm and a stroke of 120mm – the longest yet. It will need a lot of steam or air and to help economy I have settled on making it single acting (piston is pushed from one end only) relying on that heavy flywheel to keep things moving.
Fabricated crankshafts are a bit demanding on alignment and in view of that flywheel weight I have opted for an outside con rod set up but with a different method of operating the slide valve, not the usual eccentric.
(Best I admit to already having made the eccentric and discarded it!)
Due to the long stroke this engine is going to be quite wide or high …
June and the lack of useable junk is really holding up the project but that heavy flywheel is now supported on a 17mm spindle with ball races, all high up on a cast iron base.
I’ve opted for the long/wide version to avoid excessive height and that has presented problems with weight distribution, it tips over due to an inadequate base plate. The heavy flywheel supported in the middle of the baseplate helps but the assembly looks wrong… all one sided.
June 20th and I have decided to balance things up by making it a fake opposed twin cylinder layout with the 2nd cylinder being the slide valve chest. It will be stupidly wide but different!
Perhaps I should report a bit of trouble. In my quest to lighten things I machined some relatively big holes in places where it doesn’t matter and on one of the tall main bearing pillars the hole was quite near to the top so I hacksawed down into the hole to make it neatly open ended. Then I started hand filing the sawn edges to blend and make things all nice and neat but soon got tired of this and decided to open things up by using the bench grinder. The sawn gap just happened to almost fit round the grinding wheel, sort of horse shoe shape. Unfortunately.
I thought it would be easy to simply use the sides of the grinding wheel to open out and smooth the gap.
The grinding was going fine until a catastrophic ‘dig-in’ suddenly occurred.
The grinding wheel shattered with a deafening bang and a cloud of dust, the remains of the wheel continued to rotate on the grinder spindle and being wildly out of balance nearly shook the workbench to bits. I couldn’t get to the ‘off’ switch due to this shaking and resorted to cutting off the main power, it took some time for things to come to rest and even longer for the dust to settle and I’m hoping my heart rate and tinnitus will calm down soon.
Perhaps safety goggles might be a good idea in future!
4th July and to mark American independence day the engine actually runs…
The relatively large cylinder bore and long stroke make it a bit demanding on air or steam but it runs slowly and smoothly ok on very low pressure 5-10psi air.
Eagle eyed observers might spot my flexible coupling in the slide valve rod, a bit of an experiment but I’m getting tired of making the usual fiddly fork/clevis joints. Did Michelangelo tire of painting cherubs ? 😁
It will need a fair bit of tidying up before being named and this one is rather plain due to lack of interesting brass or copper additions although the crazy layout labels it as one of my creations.
England are in the final of the World Cup football and if they win I will name this engine The Southgate after England’s coach! (Lost!)
Lessons learned-
* Long stroke leads to disproportionate layout problems.
* Flywheels can be too heavy and difficult to machine in my small lathe to achieve true running.
* Flexible joints can be troublesome.
* Air passages need to be big enough.
… AND be careful when offhand grinding!
[Note to myself… don’t go back to work after having a ‘Sundown’ glass of wine. Recently I had a tipple and on returning to the workshop I drilled two holes in the wrong place and one too big 😏]
End of July 21 and adding a balance weight has smoothed the running out and allows very slow running.
Finally I couldn’t resist fixing Jane’s antique hunting horn to amplify the exhaust sound.
I think that’s it 👍
Bernie's Engines 