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149. Fuel and Oil


I’ve spent a satisfactory day getting various bits installed – at least temporarily – on the fuselage.

The engine controls and mixture valve are mounted now, though they’ll all have to come off again for painting, and the pushrods haven’t been fitted. The picture shows them both with strings showing where the pushrods will be.

Engine controls in position. The large lever is the 'coarse' control, which operates the bloc-tube carburettor, and the small one is the 'fine' control which works the mixture valve mounted just behind it.

Engine controls in position. The large lever is the ‘coarse’ control, which operates the bloc-tube carburettor, and the small one is the ‘fine’ control which works the mixture valve mounted just behind it.

I’ve also had a fun day routing the oil piping.

The pipe from the tank to the oil pump is enormous – 35mm diameter. I assume this is because the castor oil is very high viscosity, and although the flowrate isn’t huge – 5 lt/hr – you need to be sure the oil pump suction doesn’t dry out. In fact the actual oil pump suction connection itself is only 28mm dia., so it’s been fairly straightforward to use copper pipe and fittings for domestic water. We’ve included a lever valve in the system so that we can leave the aircraft stored for long periods without worrying that all the oil will work its way past the pump and onto the hangar floor! It was an option on the original drawings, so we’re making sure it’s included. The rubber hose connections at each end should ensure that any vibrations or movement of the engine are isolated from the pipework. They also make access for maintenance and repair easier.

Oil pump suction pipe

Oil pump suction pipe

One downside is that the long bit slopes upwards when the aircraft’s on the ground, making it possible to get an airlock in the system. There doesn’t seem to be any way around this, and I think we’ll just have to lift the tail into a flying position when we fill the tank for the first time to make sure no air bubbles get in.

The output from the pump is in an awkward position at the bottom of the pump facing inwards. I’ve had to use a combination of rubber hose and 8mm copper pipe and fittings to get a sensible run.

Oil Pump outlet.

Oil Pump outlet.

The pump outlet has a rubber hose connection to reduce vibration, then there’s an elbow and a tee, all in 8mm. The pipe that curves upwards goes to the engine inlet; the other one goes to the oil pulsator.

Oil Pulsator connection

Oil Pulsator connection

I’ve tried to route it as straight as possible so as to get as few airlocks as possible, but once again it’s impossible to eliminate then when the aircraft’s on the ground.

The location of the pulsator makes connecting to it rather difficult; we were going to make a hole in the plywood gusset plat underneath, but this would (a) weaken the fuselage structure and (b) make it difficult to remove the pipe, so I’ve come up with another solution as you can see.

(You may remember that the pulsator is an open-ended pipe covered up by the glass dome. The idea is that the strokes of the oil pump will show as pulsations in the surface of the little bit of oil inside the dome. In practice, I’m told, it never works, and it’s much easier to go by the smell of castor oil and the film of it on your goggles. If either stops, start worrying!)

Pulsator and its connecting pipe

Pulsator and its connecting pipe

Finally, Rick and I spent much of the day in Hereford A&E yesterday, after he came very close to losing the tip of his middle finger in a circular saw. It’s looking as if the damage may be relatively limited, as all the tendons appear to be intact, though probably damaged. But part of his index finger was sliced off, and the top joint of his middle finger is dislocated and broken. Thankfully it’s his left hand (he’s right-handed) so it’s not as disabling as it might have been, but it was a very shocking and unpleasant experience, and the result of just a moment’s inattention. Rick’s a professional, and uses the saw all the time for his work. He is very, very careful at all times, and it’s hard to see how he could have done more to protect himself. Let’s hope he makes a quick recovery and can get back to work without too much delay.


From → Building

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