Recycled Flyer

This explaination I like and agree with.

But again with an engine in the style of a PAW that has the volume above the contra bounded by a slip on cooling jacket and a threaded comp screw I stand amazed that it would ever seal well enough to be pressurized above any part of the combusion cycle!

But the proof of the pudding in is the eating as they say and if a relief hole works then I have to believe it!

Though its probably better to fix the leak though rather than add to it - a good diesel should hold pressure for 2 minutes at TDC and one that seals this well is usually much easier to start.

Cheers.

AMB

Multi Engines.... Talking to Bob Davis today and we were discussing the Lancaster with the 4 Irvine diesels and he brought up a very good point trying to get the sync on 4 glow engines at the same time would be quite difficult, the Diesels are easy, tach the one that the lowest at full bore then adjust the compression screw on the others to match. It is not going to be much maybe a 1/4 turn or less (backed off) to match the running at the lower RPM. By the sound on the video you could tell very very close on the revs, think you would being goi8ng nuts or spending a long time adjusting carbs on glow to acheive this martin

also easy hand starts a few flips and no tangles with glow power wires, plopping them on and off, big as the plane is that hassle gone and no chance of one winding up in the prop of its neighbor

Recycled Flyer

Martin, Iwould assume that with a project of this magnitude simply providing hard wired glow plugs like they do with four strokes would be not much of an issue. So no loose leads are necessary, just one socket for all four plugs and its nice and neat.

And why would synchronising glows be any harder here?

Ilike the diesels better though.

AMB

Recyled flyer, Good point if glow used certainly he would hard wire and one hookup point, I must admit not that much time with 2 cyle glows sines they all became diesel (except my one irvine 39. but I think tweeking the tommy bar might be easier and quicker than fooling with the needle
my only mult-engine is a twin star with 2 tt25s (davis heads) static run but not flown yet it zinger 9-7 (lots of pull hanging on to it) and that is under propped should be 10x7 but ground clearance issue, may have to go to a three blade or 9x8 (if made) suggestions welcome thx martin

gkamysz

My Feedback: (19)

If you are good at tuning engines 1 or 4 glow or diesel will be fine. My C-130 will be electric however.

qazimoto

My Feedback: (1)

I also find it hard to imagine a set of conditions that would allow a brass contrapiston to fall into a cylinder bore when the engine was running. Brass expands very nicely against aluminum (presumably the c/p is in the al head) as temperatures rise, and if the engine starts and runs and has the right tapers, the c/p is only going to get tighter. However a severly worn brass contrapiston at the limits of its adjustment might just fall into the cylinder if an engine was turned over by hand. Perhaps Irvine users are wearing out c/ps by over enthusiastic use of the compression adjustor.

I have a few Irvine glow 25's and .75 and 1.3cc diesels. They are superbly made and beautifully engineered. If it was a common problem surely they would have addressed it?

Ray

Recycled Flyer

Hi again mate,
If you really want to see some four engine bomber goodness just look up Paul Walkers B 17 and how he did it with glow engines and a common bladder tank.

This takes away a lot of the differences in the engine runs, that and detune the engines for a steadier run.

But I would only entertain electric with multi engine flight with their rev limiters on board.

Cheers.

AMB

Lock tite 401 Mine dropped at a low idle with a large clank, stopped, the head was history large grove banged in bottom on edge of contra bore when hit by the contra, engine no damage
had a spare head ran fine but still replaced with the Davis one martin

Hobbsy

My Feedback: (102)

Martin, have you converted an Irvine Q-40 and compared to the 40D? Q-40 has red head.

gkamysz

My Feedback: (19)

Does anyone have port timing figures for the 40D?

Recycled Flyer

Just getting back to the four engine thingy, here are two photos of a control line stunt flyer here in Oz with a four engine Lancaster, enjoy!

And they are Enya 0.19 glows.

AMB

Hobbsy Yes the runs are identical problem now I cannot tell them apart with the heads on, will check the carb bore maybe bigger on the Q40 martin

Hobbsy

My Feedback: (102)

Martin, if I remember correctlythe Q-40 and the .40D have the glow .46 crankshaft but a .030" smaller bore than the glow .46.

AMB

Dave right you are, 030 smaller bore and 46 crank, I really do not now which came first as a release the 40D or Q40 martin

Hopefulflyer

Hello RF.

Yes I agree it wouldn't be a big problem really, but it does add some complication.
If you have a single socket, it would be on the fuselage away from the props. It would need to be wired out to each wing with some disconnect for when the wings are separated from each other and from the fuselage.

If you put a socket on each wing, maybe on the outer nacelles it might be easier, but nearer the props.

It is a constant worry to me when I are working on one engine when its neighbour is running.

Cheers
Tim

Hopefulflyer

Martin and Locktite,

This was my story exactly.

I was running in the engine on the bench. Speeding up / slowing down in cycles while adjusting mixture. When just idling, it suddenly stopped with a clunk.

In fact, I found no damage at all and pushed the contra piston back in, put the head back on and carried on.
Second time it happened, about 10 minutes later, I stopped for good. Too risky.

It may be a combination of inadequate design and sloppy tolerances.

The other three engines were OK to start with and were run in for 1 hour before being put in the plane.

Later on, when I was doing engine tests in the plane (engines now mounted inverted, home made fuel tanks, throttle servos connected, dustbin silencers, etc), another of the engines played up - contra piston jammed. I couldn't screw it down nor would it pop up, even at full throttle. Maybe in this case the combination of tolerances were all too tight. I may have run it too hot also - really not sure.

Anyway I had received all four of the DDD heads by then, so I put them on and have never had another problem.

Cheers,
Tim