291. Progress. Slow, but progress
Yesterday I spent all day making new guides for the pushrods.
You can see what they do here, complete with a graphic video.
The ones I made originally were intended for retrofitting to an already assembled engine, and weren’t ideal, so I’ve made some new ones which should be more secure and not need to be checked before each flight. The trouble is that while each one is fairly simple to make, nine of them take a long time! These need to be threaded over the pushrods before they are fitted, so it seemed a good opportunity to get the job done.
Then today Theo and I and Chill met up at Shuttleworth to get as much work done on the airframe as possible while we await the completion of the engine.
The engine itself has made a little progress since last week – our nice new pistons have been honed to fit the gudgeon pins.
These are aluminium pistons, copiers of those made by Thulin in Sweden when they manufactured them under licence, as opposed to the originals which are steel, as made for the American-built examples.
The valve gear has been fitted to each cylinder, so they just need screwing back into the crankcase. (Theoretically you can up the compression ratio by screwing them further in, but I doubt it would be a good idea. You’d need to take corresponding bits off the pushrods as well…)
I thought you might be interested in this picture of the crankshaft, taken from the front end. You can just see daylight coming through the hollow crankshaft. The carburettor goes on the far end where the daylight is.
And you can see the brass keeper for the main ballrace on which the crankcase revolves. I think it’s astonishing to think they could make such big ball bearings in 1908, and even more astonishing to think that it has survived everything we’ve thrown at it!
Once the pistons and rings are fitted, the cylinders have to be screwed in just the right amount and locked in place. then the complex cam rings and followers have to be fitted to the front of the crankshaft and the pushrods inserted. Finally the front cover plate has to go on. I suspect I’ve missed out some important stages from this list, but I’ve never reassembled a le Rhone myself.
We found that the propeller hub had picked up a little surface rust, so Shuttleworth kindly let me use their wirebrush and polishing mop to clean it up before refitting it to the propeller.
Also on the bench in Dave’s workshop is his current masterpiece – a new end for the feeder mechanism for the Spitfire cannon which will go inside the wing. You can see the original in the middle, and the new end on the right – a mirror image of the original. Dave’s machined it from solid. Amazing!
Meanwhile, Theo and Chill were retensioning the cabane rigging and refitting the refurbished tachometer and tachometer cable, complete with its new gearbox, which should make the tachometer read correctly for the first time.
Progress was slower than it otherwise might have been, owing to the glorious weather outside, and the sounds of all the Shuttleworth machines being run up and flown as part of practice week. Noisiest by far was Matt Pettit who was trying to sort out the problems with a Harvard, which involved running it at full power in very fine pitch about half a dozen times. As you may know, the Harvard is famous for the fact that under these circumstances the propeller tips go supersonic, and the resulting howl penetrated to the furthest corner of the workshop. making conversation impossible.
I also took the time to polish the copper inlet ducts, which will make the engine look as it it’s been refurbished once it’s reassembled.
Thankfully, as we had a final cup of tea before departure, Matt came in with his customary cherubic grin – Matt is just like a 6ft 3in schoolboy let loose in an airfield full of his favourite toys – to announce that he’d finally got to the bottom of the problem. The Harvard – a two-seat trainer – was never designed for fuel economy, and the ground running, most of which was at full power – had consumed 60 gallons of fuel!
We had a great day, but for us the tension is starting to rise.
The engineers were tinkering with the engine of the Avro 504K all day. Indeed the main reason that our engine isn’t assembled is that they’d been working on it all last week.
In a week’s time, we need to be packing the Scout up ready for her first static display of the season in Ludlow, and the engine must be installed and running.
The Shuttleworth knows this full well – I pointed it out to Chief Engineer Jean-Michel Munn today – but they only have limited resources and it’s going to be touch and go.
But we know that they will do everything they can to be ready, and we can only keep our fingers crossed…
The Shuttleworth Collection is just round the corner from the historic Cardington sheds, which housed the R100 and R101 airships in the 1930s, and today houses the amazing Airlander airship. And on my way home I spotted it outside, so stopped to take a couple of pictures.