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About facthunter


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    non pilot
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    New Gisborne
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  1. They are just oil drain holes. A lot of the engines friction is from the oil rings, and some MODERN bearing materials. (alutin and copper lead) which must have extra clearances to allow more oil flow. Short con rod to crank throw figures give high side loads and more piston slap noise. There's always one side of the piston firmly against one side of the cylinder. Heat is not particularly a problem in a LOW HP/Capacity motor. 85 HP for 2.2 litres. About 38/litre PROVIDED you get most things right. A new aero engine should not be tight, or it would risk failure. You can't run them in at low
  2. What I covered above and heat a piston to about 220 on the crown top with a strong gas flame gives an indication of likely expansion.. From all the data I have had and Pistons I've made. (No failures) you'll need about .010" at the bottom of the skirt. (the usual place to measure it). This is with a solid piston.. Expect the motor to be noisy cold. Nev
  3. Piston temps will be helped if you don't use slotted pistons and reduce the ovality to about .003" Your skirt clearance will have to be determined and will be a lot more that with the slotted piston, when cold. IF you get it right it will be very little when hot but must always be SOME or she will lock up. It will also need some taper. .Nev
  4. No they aren't jetted . Oil will cool but you need a lot of it and in excess it will cause loss through the breather and be a bit of a brake on the engine. Slotted pistons depend on a temperature difference between crown and skirt.The cylinder getting to the temps they do creates a difficulty there. Those pistons are compromised in an aircooled motor, particularly when the whole thing is quite hot and alloy is expanding much more than steel and it's shut down. nev
  5. Yes . Proximity to the ground is the main ingredient. Speed might be a factor too, but not very relevant here. Nev
  6. Whenever gas expands, it will lose heat. P1V1/T1= K There's still a lot of pressure when the exhaust valve opens especially at high power settings and your EGT's will be around 1100 C Nev
  7. Gas in the ports doesn't reach sonic speeds, it's the pressure waves that do and that's what you can tune to with varying lengths.. Similar to waves on the surface of the ocean where the wave speed has nothing much to do with the current movement in the water underneath.. Nev
  8. I can never quite understand how that plane is balanced There's a lot in front of the wing and you can't use useable fuel as balance. Nev
  9. Usual reason to lose compression would normally be a stuck valve, almost always the exhaust. OR the head broken right off. With the last you will most times get secondary damage to the head and piston crown. Inlets are relatively trouble free. Cause, grunge build up on the stem OR a part seizure. Crook oil (too much additive) or not enough running clearance respectively. IF you had stuck rings there would be a lot of blow by and also noises from the high pressure gas blasting past the rings. (If this happens in a diesel you'd think a bearing was gone, it's so loud). Nev
  10. It's my understanding the bores were made for the maximum oversize of those pistons (plus.040"?) you couldn't rebore the cylinders and fit bigger ones. Early ones were made in class sizes of small increments and selectively assembled in the car engines various bores. In the later models of that engine this practice ceased and all pistons are "whatever they are" and so are the bores but based on nominal sizes.. The running clearance was made larger so that no engine could be too tight whatever was assembled in any combination. This of course results in engines with generally looser running fit
  11. Re the last bit you should feel it in the controls if it's happening.. Nev
  12. Load and RPM (Frequency and intensity). Much the same as spark plug temps. react . The location of the exhaust valve will move the max temp location unless it's centrally located . (never happens in practice). Area of piston skirt in good contact with the cylinder wall will affect heat loss rate and therefor temp attained. Slipper pistons or large ovality will reduce heat transfer. an oval piston only has line contact A slotted piston will transfer less heat from the crown than a solid one., because you have cut off the path over much of its skirt.Nev
  13. Not that rare in that line of work either. I thought they were using heli's rather than fixed wing. Nev
  14. Some pistons have webs to support the top and take load to the gudgeon pin boss.. Most are for strength and rigidity Short conrods are for reducing engines size. This gives more side thrust as a result requiring stronger design and also causes more mechanical noise . Steel sleeve (rare) has more lubrication problems than cast iron . Cast iron is like a fruitcake and holds oil in it's pores. Steel depends on the hone pattern being retained . Works better on a nitrided surface. Cast iron is more likely to keep it's dimensions than steel but it's rare in aero engines being weak in tension and c
  15. On many aircraft with full flap down you really won't go very well at all as far as climb performance is concerned. It's the excess power over drag that permits climb. When you don't have it you don't climb. Larger flap angles have much more drag than extra lift. Some flaps don't provide a lot of extra lift at all. They mainly give you a steeper approach. OK from you about 5 posts ago.. Control of airspeed is the biggest factor relating to safety . Since power is at idle it's about attitude. IF you are low the recovery becomes more critical. The smoother and more positively the proces
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