ptwizz

Mark, PM sent.

Cheers Simon. All the machining is manual. I have a 1926 Drummond round bed lathe, a Sieg X3 mill and a pillar drill. The mill is of Chinese origin. When I received it, I stripped it down and rebuilt it, carefully setting everything square and straight. With a little care, it is fairly straightforward to produce perfectly good parts on a very affordable machine. I have CAD software, which I have used to design the engine. Each part is designed such that I can manufacture it with my own machinery, so, for example, the crankcase is an assembly of 9 parts bolted together. Some of the set-ups required to produce large-ish parts on the small machines need to be 'imaginative'.

Another significant chunk of engine: The master rod. Made entirely on my Chinese milling machine, from 2014A-T6 aluminium.

It is true that injected engines don't have a venturi as such, but they (i.e. our petrol engines) still have a throttle which causes a significant pressure change, more than the venturi of a conventional carburettor. The difference would be that the carburettor has a fuel jet at the location of the pressure change. Evaporation of the fuel has a cooling effect which may contribute to icing. The icing then affects the flow around the jet and prevents the carburettor from operating properly, resulting in poor engine performance. I am interested to know whether injected engines avoid icing altogether (by removing the jet from the area of pressure drop) or are simply more tolerant of icing?

Sent.

A few points here: 1) To properly compare 'new' and 'aged' fuel, you'd have to test samples from the same batch using a calorimeter. The uncontrolled variables involved in measuring RPM of an engine driving a prop are too numerous to list. 2) It is difficult to know how long your 'new' fuel has already spent in the petrol station tanks, in a tanker on the road, in a holding tank, at sea, etc. 3) High octane fuels allow running with higher compression ratios without pre-detonation. Running higher octane does not, in itself, create more power. 4) If your fuel has been sitting in a stationary container for a while, give it a good shake up. Some of the lower density fractions may begin to seperate out over time, but they're still there and just need to be mixed in. This used to be compulsary practise with the old 2 stroke oils, which would settle into the bottom of the tank and carb, causing much frustrated kicking of BSA Bantams and the like. 5) Don't throw away old or degraded fuel. mix it in with a larger quantity for your car, bike, lawnmower or other inferior machinery. Probably best not to put any 2 stroke in your car if its one of the new fangled type with a catalytic CON verter.

Why would someone do that? If I wanted to give an extreme example of avoiding local turbulence (or 'rotor'), I couldn't do much better than 'directly beneath a hovering helicopter'. I sometimes wonder whether an individuals skill in recovering from a bad situation isn't outweighed by their foolishness in getting into that situation in the first place.

Guy, Did the person who told you of the Baileys design flaw by any chance also warn you that it would kill you because it is an outdated design and has no crumple zone?

I bought my V3 second hand. It had been updated with the V4 crank and seals, but I believe the piston is original. I have flown 10 hours since I got the motor, with no problems. The engine shows no signs of overheating, no smell after an hours flight. Was your piston scuffed over a patch, or a few distinct scratches?

A long, long time ago, in a thread far, far away, I mentioned that I was planning to build a radial engine. The engine is not destined for a Paramotor, but for anyone who may be interested: To date, I have modelled the whole engine in Catia and manufactured the oil pumps (one for feed, the other for scavenge). The engine uses Russian Dnepr heads, barrels and pistons. These were chosen for being the right size and very cheap. Dnepr engines are not known for their reliability, so I have reduced the compression ratio and valve lift to reduce mechanical and thermal stress.

Your training should include enough meteorology that you will be able to judge for yourself whether conditions are suitable for you to fly. The simple rule is if you're not sure that conditions are good and will remain so for the duration of your flight, you don't fly. Until you have sufficient knowledge, it is your instructors responsibility to ensure that you are not flying in unsuitable conditions. In the early stages of learning, it is best that you fly in calm, stable conditions so that you can concentrate on basic control. I have flown about 10 hours since passing BHPA Club Pilot. I have flown in mildly thermic conditions, which can be a something of a roller coaster ride and unnerving for a novice. As you gain experience, you will be able to tackle more challenging conditions and that will open up more opportunities to fly. Flying in conditions which are marginal for your ability will detract from your concentration on some of the more basic stuff, like looking out for other aircraft, watching the weather, navigation etc. We all progress at different rates. I still consider myself a novice and prefer to fly in calm conditions until I am confident that my control, observation and navigation are second nature.

Not very new.. Google 'sliding vane rotary steam engine' and you'll find a rich history. Fundamentally, the design has the chamber pressure acting at 90° to the vane motion, which produces the highest possible friction load between vane and housing. Piston engines and Wankel rotaries have the sliding element acting in line with the load, minimising friction load. Pretty much every possible configuration of engine was invented 100 years ago. One or two may become viable as new materials become available, but the piston and crank will be hard to beat for simplicity and efficiency.

I would treat a solar farm on the scale shown in those pictures as a built up area and avoid it anyway. I wouldn't fancy an emergency landing in one. The second picture looks like a solar furnace. Fly too low over that and you significantly increase your risk of overheating (by 1000° or so!)

It is possible to adjust belts by frequency without the expensive kit. 470 Hz is A# above middle C. If you have a means to generate or measure that tone (i.e. the device on which you are reading this, or perhaps a guitar tuner) then you can simply 'ping' the belt at the middle of the long run between the pulleys and adjust to match the frequency. This is also a useful technique for finding parts which are likely to vibrate. At 6000rpm, an engine generates a primary frequency of 100 Hz. Anything near that engine which vibrates at 100 Hz or less when you ping it is going to vibrate when the engine is running.

If the 6-stroke engine were properly designed, the hardware would operate at the same temperature as the 4-stroke. The 5th and 6th strokes recover energy from the exhaust gas. The temperature at which the hardware operates is limited by the properties of the materials. If it is possible to configure the engine to run hotter, effeciency and specific power output are increased. Some of the smoothest flying is during the winter months. If you've waited for the fog to clear before launching, humidity will be high. On launching, the throttle will be open for the first 30 seconds or so of flight. All the ingredients for carb icing are there. I think the thread has managed to stick to the heading "Engine Design Project" fairly well. I haven't seen any pictures of cats, nor any comments on politics, religion etc. Please sign my petiton to call for a ban on scientologists creating images of gay buddhist felines.

Any engine can suffer from carb icing. http://www.kfackler.com/gtuf/carb_ice.html I had a motorcycle which would ice up on icy, damp mornings. Icing would occur at the pilot jet, causing the engine to die at low throttle settings. Not ideal in icy conditions. This was fixed with the addition of electric carb heaters, controlled by a temperature sensor in the airbox.

Since solar panels absorb energy from the sun and that energy is carried away from the site, I would expect them to heat the air less than a dark, absorbent surface such as a road or car park.

Thermal shock shouldn't be too much of an issue. All the heat that goes into the cylinder and head is generated in the few milliseconds of combustion. The flame temperature (2000°C+) is very much higher than the cylinder & head temperature (100 to 120°C). Water or air injected at ambient (say 20°C) is only 80 to 100°C cooler than the hardware, so the thermal shock will be much les than during combustion.

1) Gas Turbine: Apparently they don't scale down with the power to weight ratio that might be expected, probably because various ancillary systems (ignition, oil, fuel pump etc.) are very similar for 50kg or 500kg thrust. http://www.gasturbine.pwp.blueyonder.co.uk/ct3201.htm 2) Sixstroke: The sixstroke concept is nice in theory for improving efficiency, but has some issues attached. Specific power output is less than either a 4 stroke or a 2 stroke, due to less frequent firing. This is to some extent offset by the additional power extracted on the 6th stroke. The engine will need a substantial water reservoir, which will be heavy. http://en.wikipedia.org/wiki/Six-stroke_engine

True, Pete. If the oil is delivered directly to the bearings and cylinder wall, the total rate of oil consumption is reduced. Why is this not done in carburetted 2 strokes (to my knowledge)? The modern 2 stroke engines I have dealt with have a metered pump, but it just squirts the oil into the cylinder and crankcase to thrash around with the fuel/air mix in the accepted manner.

[youtubevideo] [/youtubevideo]The video was taken by my colleague, Paul. He says the pilot was arrested on landing.

A couple of my colleagues were at Stuttgart airport yesterday, when they saw and filmed a hot air balloon drift gently into the airport, while aircraft continued to operate. The balloon landed in the middle of the airport, between runways. The number of security vehicles which turned out suggested this was not a planned event. I'll try to get hold of some pictures / video later.

A direct injection 2 stroke requires a seperate system to distribute oil to the bearings. If the engine has crankcase induction (conventional) then it either burns that oil or it needs a means to keep the oil out of the induction air. This is possible, using a complex array of seals at each bearing and a dual path oil system.

Thanks AdEves - more to it than I thought.