A job for Jim

I've been challenged with this job for Jim. I've made a start...

A broken undercarriage pivot

A new part in the process

A fine days' flying

The forecast for today has looked promising for a few days and lo and behold, it was right. Almost windless for most of the day, until mid afternoon when the wind picked up from the South.

Ians F15 Eagle

Today was a near perfect day. No one had a serious accident, Jims new jet had a bit of a kangaroo landing and scratched some paint, but no serious damage, and I lost a tail wheel from the Yak, hey-ho!

I tried out my KT120fsT this evening (before it rained) and got nowhere with it, It still stops when hot, and it certainly gets hot, too hot, but the engine isn't tightening up as its free to turn over by hand immediately after stopping. There is some pre-ignition at times and I think this may be a clue to the problem. I may have to have a closer look at the valve timing, and/or place yet another gasket under the cylinder heads. Some experimentation required.

I've had it running again...!

...with more success. I turned up a pair of 0.3mm thick copper gaskets to reduce the compression ratio and tested the running characteristics again but there was still some pre-ignition going on at higher revs. Back to the machine shop then, and two more copper gaskets for reducing the compression ratio even further. Now there's hardly any pre-ignition, but I'm now finding the engine stops when it gets hot and there's hardly any compression. I know the bores were a bit rough on surface finish even after honing and this is due to the cast iron being porous. I'm tempted to make two new sleeves from a different material. That way I can build in the extra thickness required to reduce the compression ratio and do away with one gasket under each cylinder head.

Here's a short video:-

Ketro KT120fsT in action

Cornwall was a real success

Everything fell into place, even the weather was spot on. We drove down early Friday morning in heavy cloud which turned into drizzle and fog over Bodmin Moor and although the fog cleared the drizzle remained on and off all the way to North Cliffs. We parked the caravan and put up the awning and waited for Geoff and Mary to arrive. They started out before us but didn't arrive until after 12:30. They'd been mooching around Redruth and Camborne all morning because they thought it may be muddy as well as wet up on the hill. But things didn't improve so they came up later.

On Saturday the weather changed. After an early shower it turned fine with 8 MPH winds from the West and broken sunshine all day, and Sunday was even better, 2 MPH winds also from the West, and near unbroken sunshine.

Me with Yak 54, photo courtesy of Geoff.

There were some nice aircraft to be seen at the show including a Stirling bomber, a deHavilland Mosquito and a Spitfire. A few jets put in an appearance with a Rookie, Kangaroo, Boomerang and an F16 flown very realistically by its skillful pilot. The electric slot was well over subscribed so the time allocation was doubled, electric gliders and slower craft first, followed by the faster EDF (Electric Ducted Fan) jets and other fast craft. That included me with the Pico-Jet.

A 180 panoramic

deHavilland Mosquito built and flown by Roger Kellow

Rogers Mozzie developed a problem during flight in that the undercarriage failed to lock down, but was able to recover from the situation and landed safely. Well done Roger.

Also impressive was a helicopter built by Kim Johns. Now helicopters leave me cold, I just can't get interested yet I feel compelled to watch in case it starts heading this way in an uncontrolled manner. But this was different. Modified and developed to accept a gas turbine, it was flown expertly by Mark Milne and performed just like a full sized helicopter. Even the sound and smell was the same. I'm told its the only one of its kind in the world - very impressive.

I've had it running...!

...on both cylinders! Driving a 16" x 8" Master Airscrew propeller, and its too small. I've found it labours when it gets hot, so I think the pistons may be expanding, reducing the clearance in the bore. Its not been up to maximum revs as I'm still trying to find the best carburettor settings.
I can confirm the pistons have expanded whilst hot as there are shiny areas on the sides where friction has occurred. I set them up in the lathe and machined off a minimum amount, just enough to clean the sides. The rear bearing had just started to break up, this is a very small bearing at 3mm id x 6mm od x 2.5mm tk. Part of the metal dust cage had come out and some balls were missing, so I removed the what was left and replaced it with a spare. Now in the middle of reassembly. Should have it running again soon.
Off to Cornwall this coming weekend, but I don't hold out much hope of having it ready in time. There's too much work to do on the aircraft (Ultimate Biplane).