ChristerRE: Rebuild or Replica??
This discussion pops up every now and then. I have taken part in a few but neither of them have reached a conclusion.
I think that the originality question can be viewed this way:
Total originality is gone when the aircraft is put through maintenance the first time but “originality for all practical purposes” is maintained if the aircraft is maintained and repaired according to manufacturers instructions.
This would mean that a fighter used in WWII, maintained and repaired for serviceability, is to be considered original. I think no-one will argue otherwise.
When the fighter transfers into a warbird, if the operator continues its maintenance and repairs according to the same specifications, then it´s still in original condition.
The only issue, so far, would be modern airwothines requirements dictating the substitution of modern details for inadequate original details.
I think that a considerable proportion of the systems have been modified to comply with modern airwothines requirements so, the question is: Do we want to see it fly or do we want to see it in original condition in a museum?
If the mentioned maintenance and repairs requirements lead to major work being done, then we are into the rebuild/reconstruction/new build question.
To be considered a rebuild, I think that a substantial proportion of the airframe would need to be re-used in the process – say 75% or more. This would mean that only airframes without major damage can be candidates for a rebuild.
I would consider the work carried out on an airframe after a major accident, or if the project otherwise is in poor condition, to be a reconstruction – less than say 25% re-useable but at least the data plate.
Then there´s the big grey zone between 75% and 25%. I´m not discussing originality here but the line between a rebuild and a reconstruction. A simple way to decide is the “more than 50% or less than 50%”.
How do we establish the percentage? By weight or by number of items? If it´s the latter then any re-riveted airframe would be a reconstruction ……
New build then, well, we have seen examples of new build aircraft with fresh serial numbers and the rest of the package so, there´s a thin line between a reconstruction and a new build, the thickness of an original data plate.
Finally the sad story about the Me 262 accident, when repairs are finished and it takes to the skies again, is it a new build or a rebuild?
Christer
ChristerRE: What about multi-row radial engines?
Hi Keith!
This is an engine layout that I´ve never seen before. Very interesting and my sorry excuse for a brain hurts when I try to figure out how it works.
I think we can forget about the conventional radial thinking, e.g. the ignition sequence of a radial requires the number of cylinders in each row to be uneven.
The X-layout Rolls-Royce Vulture was not considered to be a radial engine but a multi bank engine, four banks of six cylinders with 90° between the banks. The 90° between the banks and the number of cylinders in each bank was what gave good mass balance without dynamic balancing and a reasonable firing order.
Is it possible that we are looking at an engine that really is four 90°V or maybe four horisontally opposed, four cylinder engines, fitted to the same crankcase?
How was it developed from the Octagon?
Maybe I ought to try to understand that one first ……
Christer
ChristerRE: What about multi-row radial engines?
Hi Keith!
I´ve tried to find more information on the web about the Octagon and the Hydra but I couldn´t find anything.
Do You have more information on layout and such, possibly even pictures?
As I understand it, the Octagon was a single row 8 cylinder engine and the Hydra was a double row 16 cylinder engine.
The designs can´t have been radial-ish, at least not in terms of ignition sequence.
Please, help me to regain my sleep, if not at night so at least at work!
Christer :'(
ChristerBooster pumps
I´ve got a copy of the Spit Mk.XIX and Griffon 60-series manuals and this is how I understand it:
There´s an engine driven fuel pump which works only when the engine is running.
The booster pumps are immersed in the fuel tanks and are to be used under certain circumstances. According to the manual they should operationally always be used and the drill when changing tanks was to start the booster pump in the “new” tank, change the fuel c-o-c-k to the “new” tank and finally shut off the booster pump in the “old” tank. Doing it the other way around wasn´t a good idea.
Prior to start-up the booster pump is used to prime the fuel system to make sure that the fuel lines are full. Otherwise the cylinder priming pump doesn´t work. This is a manual pump which injects small amounts fuel into the cylinders and induction manifold.
The Griffon had a Coffmann cartridge starter which cranked the engine a few revolutions when fired.
The throttle should be opened an inch, magnetos (ignition) on, fuel booster pump on, the stick held back, press the ignition booster button and fire the cartridge at the same time, when the engine starts turning release the fuel cut off lever to the on position.
If the engine didn´t start the fuel cut off lever should be set to off immediately, if not fuel kept being injected and the engine would become flooded.
If you count the things to do during start-up another arm with two hands would be helpful ……
Today electric starters have been substituted for the cartridge starters which has changed the procedure a little.
The booster pump is not turned on prior to start-up which means that there´s no fuel pressure. The fuel cut off can be left in the on position and when the electric starter cranks the engine the engine driven fuel pump builds up fuel pressure quite rapidly and the engine starts with (hopefully) less fire hazard.
Christer,
waiting for someone with hands-on-experience to tell me I´m wrong x(
ChristerRE: Radial engine running in reverse ?
[updated:LAST EDITED ON 05-11-02 AT 04:31 PM (GMT)]It would take a lot of enginuity to get a four stroke engine running backwards, sucking through the exhaust manifold and blowing into the induction manifold!!!!!!
It works with some two stroke engines though. If the idling rpm is adjusted so it only just ticks over, sort of hesitates, then there´s the possibility that it changes the direction of rotation to backwards.
It has nothing to do with the radial design. The main prerequisite is a two stroke engine.
Christer 😉
Edited:
It´s possible that it works with the old radials with an automatic inlet valve in the piston head and a rod actuated exhaust valve in the cylinder head. When the piston decends in a cylinder with a closed exhaustvalve, the automatic inlet valve opens due to the underpressure. The engine can rotate in any direction if the ignition system is adapted for reverse rotation.
It still has nothing to do with the radial design. It´s about direction of gas flow.
A two stroke engine doesn´t require adaption of the ignition system, it runs backwards but not very well.
ChristerRE: Which Spitfire is this?
Me and my spelling, when am I going to learn to proof read?
Christer,
typing according to the FW-principle (Fast and Wrong)
ChristerRE: Which Spitfire is this?
I´ve had a look or two as well and these are my thoughts:
The propeller is totally wrong, the shape of the blades suggest a right hand tractor which is correct for a Merlin but the blade pitch would make it fly backwards.
A lot of structural detail is wrong, lacking rivetting handholes, movable details seam to be fixed etc.
The close-up of the tail shows black aluminium rivets, never seen those before.
Symmetric under wing radiators exclude all variants that doesn´t have a two stage Merlin so, Mk II or Mk V it isn´t. Most single stage Merlins also had two-into-one exhaust ejectors, not twelve separate.
For what it´s worth, my bet is on a GRP model of a Mk IX.
Christer
ChristerRE: RW382
[updated:LAST EDITED ON 30-10-02 AT 11:47 PM (GMT)]I did a search for N382RW on The NTSB aviation accident database;
http://www.ntsb.gov/ntsb/query.asp
and this came up;
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001211X10344&key=1
This thread on the FlyPast forum mentions that RW382 is currently undergoing rebuild;
http://www.keymags.co.uk/dcforum/DCForumID1/1597.html
Maybe Bradburger knows more ……
Hope this helps,
Christer
ChristerRE: Rotary engines
Wombat!
I know these things can happen and I said it with a wink and a lol.
It has never happened to me though but, the following has:
I type a message and while doing this I hit “back” to check the post I´m referring to and then “forward” again to continue typing. From time to time a gremlin is there and nicks what I´ve typed and that´s irritating since I´ve got a low hitrate on the keys.
Now I always highlight what I´ve written so far and hit “ctrl-c” before stepping back.
Christer :+
ChristerRE: Charter Member!!
As I remember it, I became a CM at the time of a forum upgrade to a new version. I think that goes for all who were here at that time.
ChristerRE: Charter Member!!
As I remember it, I became a CM at the time of a forum upgrade to a new version. I think that goes for all who were here at that time.
ChristerBreaking the brake ……
Well, I sat there thinking that something is wrong but couldn´t find out what.
Thanks for pointing it out but, did You have to rub it in twice? 😉
Christer 😀
ChristerHorse Power
Ant,
Break Horse Power (BHP) is a unit used in the non metric countries.
One BHP = 745,400 W.
It originates from how much work a horse could do in a mine. It´s a convention that a person just decided to use, albeit after some study of the working animals.
The term was Horse Power, the Break was added when engines were tested by breaking them on a test stand.
The Metric Horse Power (MHP), also called Cheval Vapeur (CV), is different. Is this what You mean by straightforward horsepower?
One MHP = 735,499 W.
I´m not 100 % sure but I think that it is connected with converting a certain measure of steam into boiling water in a steam engine.
What is measured on the test stand is the torque over the operating range of rpm. A formula is used to convert torque to BHP. Maximum torque is alwas at a lower rpm than maximum BHP which means that rpm is in there somewhere in the formula.
I found these links:
http://www.howstuffworks.com/horsepower2.htm
http://www.howstuffworks.com/question622.htm
Hope this helps,
Christer 🙂
ChristerRotary engines
[updated:LAST EDITED ON 02-10-02 AT 09:51 AM (GMT)]I was borne in the swedish town where Enoch Thulin had his aeroplane factory in the early twentieth century. It so happens that, in our club house at the flying club, we have a LeRhône rotary engine and this is what I know about it.
First of all, engines are stupid. They don´t know if the crankshaft or the crankcase is supposed to turn. It really doesn´t matter and if you start any engine and let it loose on the floor the crankcase will rotate in the opposite direction of the crankshaft.
So if you fix the crankshaft to the airframe the crankcase will rotate.
The crankshaft was hollow to allow the air/fuel/lubricant mixture into the crankcase.
The principle was four stroke with two valves. The exhaust valve is in the top of the cylinder with an outside actuating rod. The inlet valve is an automatic valve in the top of the piston. At the top of the exhaust stroke the exhaust valve closes, when the piston travel down the cylinder an underpressure is created which opens the automatic inlet valve and the mixture is sucked into the cylinder.
This wasn´t very efficient so, soon the inlet valve was moved to the top of the cylinder as well and it too was controlled by an actuating rod. On these engines there were tubes running along the cylinders connecting the crank case with the inlet valve becuse the mixture was still ingested through the crankshaft.
Neither this arrangement was efficient and to allow further developement in terms of HP the rotary design was abandoned.
I hope this helps,
Christer 🙂
(who seems to be older than Keith)
ChristerRE: Centaurus
Hi Keith!
I´ve seen pictures of sleeves and the intricate design of the ports to fit the holes in the cylinder when rotating/oscillating. In the sleeve there were two inlet ports, one exhaust port and one port that was alternatingly inlet/exhaust.
I´ve tried to figure out if valve overlap was possible for a sleeve valve engine? It seems to me as it wasn´t possible!?
If I´m correct, wasn´t this a drawback in the design which gave a lower volumetric efficiency?
For those who might not know, valve overlap in a poppet valve engine means that the inlet valves open before the exhaust valves close. In a suction engine, valve overlap is short whereas in a supercharged engine it´s longer.
On the exhaust stroke, it seems to me that at the top of its motion the piston covers the ports. Are the exhaust ports designed, elongated towards the top, to allow gas to sneak down beside the piston?
Thanks for the new “series”!
Christer 😉
(Who didn´t understand the comment about getting out more in the other thread! Maybe I should too and all other people with a teccie interest?)
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