View Full Version : Comper Swift..G-ECTF (Naked)
22nd Jul 2012, 06:28
After 12 years of hard work Phil Cozens Replica Comper Swift is now only a year away from flying (we hope).
She came out of the workshop yesterday (thanks to the weather), for a test rigging. And went together very well.
Loads of photos here...
Phils Comper Swift. - a set on Flickr (http://www.flickr.com/photos/tupperware_pilot/sets/72157630690242988/)
22nd Jul 2012, 07:25
That is very nice indeed!
Nice one Phil. If my Swift is finished after another 12 years I will be very happy!
22nd Jul 2012, 09:10
Not sure why it is classed as a "replica" - surely if built to the drawings, it is a "real" Comper Swift!
22nd Jul 2012, 12:52
Not sure why it is classed as a "replica" - surely if built to the drawings, it is a "real" Comper Swift!
It's buit to a set of PFA (LAA) plans.
22nd Jul 2012, 13:22
Very nice indeed.
It's built to the original plans with a few changes required to be incorporated in the build. The plans are NOT a full set.
The story of how the plans survived is an interesting one; perhaps another time.
If you wish to see the surviving originals (pencil tracing, ink on fabric) they are now lodged with the RAeS library. Another near identical set is with the RAF library at Hendon.
How did they survive then...? :)
10th Aug 2012, 13:04
Don't know if you've seen this guys but in case you haven't this is Arthur Butler in a Comper Swift flying England to Australia, to retrace Bert Hinkler's great flight of 1928 http://http://www.youtube.com/watch?v=qQWU00ub9ow
28th Oct 2012, 23:39
Had a great chat this week to the grandson of Arthur Butler - of Comper Swift fame.
His name is Mark Pitts and he is a top boxing trainer whose fighters have included Sakio Bika (v the great Joe Calzaghe) and Arnel Barotillo (v the great Manny Pacquiao).
He says Arthur - who ended up running a big transport company which was then sold to Ansett - taught him boxing when he was a small boy
A subject close to my heart.
Arthur Butler wrote an account of his amazing flight from England to Australia.
"Flight to a Lady" was first published in 2007, ISBN 978-0-646-48244-6. Well worth a read.
Anyone who is prepared to fly over the shark-infested South China Sea behind a Pobjoy engine has truly got 'Balls of Steel'....! I'm shuddering just thinking about it. :\
31st Oct 2012, 15:15
The best one I ever saw was Pete Channon's Comper he used to keep at Redhill. Don't know what happened to it. Pete might well see this and add to it.
31st Oct 2012, 16:07
Very nice little aeroplane but view forward was not too good!
31st Oct 2012, 18:13
When I did my ATC giding course in 1964 I seem to recall a Comper Swift looking more like a pile of wrekage than an aircraft buried deep in the darkest recesses of the darkest hanger on the station. Anyone know of it or what became of it.
31st Oct 2012, 22:22
Of course the Pobjoy engine is happy in its lack of knowing if it is over water (Sharks included) or not,as the sharks will not be intererested in munching on its
aluminium and steel.
However this fine engine will give good service if given the required servicing it requires; but has to live with mags that rev twice as much as normal and then deliver a spark to a rather insecure distributor cap.
In fact it was a failing rotor arm that put me down in Iran,and forced a return (over the shark infested Gulf of Oman) back to Dubai on only one mag with a very much 'spare' arm.
It was either that or leave the machine at Jask (not much of a choice).
As an exercise in power to weight and actual thrust the Pobjoy has little equal.
In order to give some chance of survival in event of a ditching (no dinghy) the Comper's empty space was filled with polystyrene blocks.
The engine would be an excellent candidate for electronic ignition.
Prangster, ABTC had had a bit of a prang in the sixties up that way,and was rebuilt by Jeremy Menzies down south.
Pobjoy;- The Pobjoys have probably got a better chance of being reliable now with the help of modern technology. They were/are powerful, but pilots in the '30's, when the engines were new, suffered numerous problems and forced landings - and that was often with 'factory-support'. As you state, these were mostly ignition-related issues. Lots of character though and they sound great...!:)
1st Nov 2012, 08:04
Talking with Phil the other day, the ignition is a possible weak-link, but there is a plan B. It's ready for covering, so should be flying next year. (we hope)
The early Pobjoy engines did indeed suffer problems because of the speed of the rotor rotation. It was magneto failure that caused the P Type engine #P1 to fail its type testing in 1926.
Further failures of the BLIC G7R magneto in 1927 on engines #P1 and #PII were established by RAE to be caused by various problems within the magneto. They also found that running at between 5250 and 6053 rpm the imbalances in the magneto would also cause shaft deflection and rotating members to foul the pole shoes.
A redesign to use the BTH M1 F1 magneto required quite a bit of modification to the rear engine case. Following the redesign, engine #PII completed its type testing in August 1928.
Engine #PII then went on to fly in the Parnall Imp in 1929. #PI was also modified. It was displayed on the Parnall stand at the 1929 Olympia exhibition before being sold to Russell Nicholas and fitted to the Beazley Pobjoy Phantom racer in the USA.
Later, when Steve Whittman bought the aircraft, it was replaced by a R Type engine. Some time later #PI was installed in a Florida swamp boat (looking for more info on this). During the late 1990s - after Whittman's death, the engine returned to the UK and found it's way into a 3-wheel Morgan; it still runs to this day.
Only one other P Type is proven to have been built and that was the one built in part by AC Cars shortly before they went into voluntary liquidation in 1929. Engine #P3 was the the first Pobjoy to be fitted to a Comper Swift, G-AAZF (S30/7).
The Niagara II was intended to use the Rotax NAE magneto which improved reliability because of its slower rotational speed. Very few (if any) Niagara II engines actually had the NAE magneto fitted because Pobjoy had far too many of the BTH M1/2 magneto used on the R type still sat in storage. Only some of the late built Niagara IIIs would have the Rotax mag fitted.
Sorry if I've gone on a bit.:O
2nd Nov 2012, 13:01
Indeed the Pojoy is a light and powerful unit,but aside from the mag situation the valves are a 'weak spot' and need to be changed to a modern material.
The R had exposed valve gear supposidly lubricated by grease (not very well) and the main advantage of the Niagra and Cateract was the oil fed enclosed system.
This system relied on small pipes giving a metered oil supply to the rocker covers (top cylinders),but this can 'silt up' and it is best to actually inject oil into the rocker on a regular basis to ensure some lubrication takes place.
Aside from that i have never had a mechanical failure of the engine or gearbox in hundreds of operating hours.
Used to have 'issues' before changing the valves,but one has to accept that with the territory.
The unit had a fairly low overhaul life because of this,and would have seen valves replaced on a regular basis when they were readily available.
All in all this is a great engine to fly behind and gives great thrust for little weight.
Sir George Cayley
2nd Nov 2012, 22:15
I admire craftsmanship and the photos above shout that out. All I can make is sawdust so this work is beyond outstanding.
It seems sad that it will be hidden under fabric and paint, could Visqueen be the answer?
When John Greenland crafted the first replica Comper Swift he set the bar for workmanship VERY high.
Its a while since have seen Phil's Swift but I recall he has indeed done a splendid job so far.
If you admire craftmanship then have a look at this
Sopwith Snipe Project (http://www.theaerodrome.com/forum/replica-aircraft/36007-sopwith-snipe-project.html)
I though you and others might like the designer's take on the sludging of the Niagara II. I found this in a paper wrtiten by DRP in early 1938. I doubt many have had sight of it as it has been buried away in an archive for a very long time. The good news is that I also found 40 or so Pobjoy engine drawing of various parts from the P-Type though to the Niagara series. All are now digitized. :ok:
The Niagara Engine and its Descendants.
The Niagara III engine (Rotax 4-pole magnetos) has now reached a stage of satisfactory reliability and durability.
Its immediate predecessor, Niagara II, gives trouble in service from the following two causes:
(a) The high speed BTH 2-pole magnetos are insufficiently reliable. They are replaced in the Niagara III by the slow-speed 4-pole Rotax magneto which, although much more expensive than the BTH type, has so far given very good service.
(b) The fully enclosed valve gear is lubricated from the main pressure oil supply, the feed being controlled by a needle valve. This needle valve is too sensitive; either an excess of oil is delivered to the valve gear and results in “oil-slinging” or it sludges up and the gear runs dry.
The following sequence of troubles develop, being much more prevalent in “Scions” than the “Monospars”, evidently due to the comparative inaccessibility of the engines in the former machine:
The ground engineer in the endeavour to reduce “oil-slinging” cuts the valve gear supply to the danger point.
The valve gear sludges up.
The valve gear runs dry, the valve guides wear, the valve rocks on its seat and begins to wear the latter away.
The clearance is taken up and the cylinder loses compression.
The hard-pressed ground engineer neglects the incipient trouble until serious damage results to the valve gear.
The more conscientious ground engineer curses and starts to pull the cylinders off.
It must be admitted that the cowling on neither Niagara II nor III is designed for easy removal of individual cylinders. It was originally hoped that the engines would run 400 or 500 hours without the cylinders having to be touched.
Owing to this trouble with the oil system of Niagara II, we find a crop of complaints that at about 200 hours or even less it is necessary to pull the cylinders off. By the time the local engineers have replaced everything, further troubles are liable to develop due to mal-adjustment of the parts. The ground engineers are then liable to develop a “hate” towards the engine.
This problem was fairly well tackled in the Niagara III (which engines have now been in service about twelve months) by the provision of a non-adjustable non-sludging piston valve control of the valve gear lubricating system. Improved oil joints are also provided to reduce oil slinging.
This scheme is nearly trouble-proof and gives the engines an opportunity to complete between 400 and 500 hours between complete overhauls, top overhauls being omitted. The later gain has been achieved by improved piston and scraper ring design. Oil consumption is now well under control in the Niagara III.
16th Dec 2012, 08:35
Saw some Viagras on Ebay. Any use to anyone here???
Pobjoy aircraft engines | eBay (http://www.ebay.co.uk/itm/Pobjoy-aircraft-engines-/160940446590?pt=UK_CPV_Aviation_SM&hash=item2578cc537e)
16th Dec 2012, 18:20
I think it is fair to say that the 'servicing' and operation of a Pobjoy is more akin to a cross between a sewing machine and a small turbine.
The engine was very small and light for its power,but had to live with materials and oil of the period.
Because the oil has to cope with a reduction gear (SAE 50-60) this is not ideal for good flow through a tiny metering system to the top valves.
As mentioned the cowling system would not have encouraged much extra probing,and indeed the valve design (and material) left little reserve for poor lubrication.
However i changed my valves very early on and ensured the guides got a sploge of lubrication with direct injection between flights.
The Gypsy engines of the time had valves that were 'bathed' in oil due them being downstream in the system.
It is only the top three cylinders that need attention on a PJ so in the 'open' (no cowling) system of a Swift giving them an occaisional squirt is no problem (just like many non aviation engines of the time).
The real benefit comes when you fly behind one,Power,thrust,and that Pobjoy 'growl'. As i soon binned the collector ring exhaust in favour of 'no problem' stubbs the slightly grimy face was a small price to pay.
In non aviation use an early Morgan would be a suitable home for one.
As most of the current engines have the BTH mags fitted it is good practice to open and close the throttle SLOWLY thereby allowing the the mag drive to absorb the input,and giving the piddly little BTH bearing a fighting chance.
Under no circumstances should the 'Gypsy' mag coupling be substituted for the original Pobjoy one, it will not cope with the exta rpm.The original drives may look 'sloppy' but that is the secret of their worth.
17th Dec 2012, 17:13
Hi bral et al,
I enrolled at the Cambridge University Library today, looking for Pobjoy drawings, but I failed my quest. I was under the impression that the UL had _everything_ ever published. I'd love to know of other libraries where I could obtain drawings that would enable me to construct an engine in 3D CAD. I have a project in mind, along the lines of rotec, jabiru, but remarkably similar to the Pobjoy.
Drop me a PM with your own email address and I will get some Pobjoy drawings to you.
18th Dec 2012, 09:52
Might be worth getting in touch with Ron Webster. He seems to be quite clued-up and he might be willing to sell you a kit of parts.
Clutton FRED | Power to the people and FRED! (http://cluttonfred.info/post/14232541880/webster)