Camit engines - anyone got one?

[facthunter]

That's it. I will buy an inherently ice resistant carby. Why didn't we all think of that? They are still making the old dribble injection system. With a bit of ""tuning" what's wrong with one of those? Manual leaning. Learn to start it and not set the grass on fire and away you go Nev

 

 

[Bob Llewellyn]

That's it. I will buy an inherently ice resistant carby. Why didn't we all think of that? They are still making the old dribble injection system. With a bit of ""tuning" what's wrong with one of those? Manual leaning. Learn to start it and not set the grass on fire and away you go Nev

CS-VLA 1093(a)(4)... there's no "Acceptable Means of Compliance" explaining which carbies will do; so obviously we need to ask at our local carby shop.

ps I got the wording slightly wrong; it's "...a carburettor tending to prevent icing..." - does that means it protects the wing leading edges as well?

 

 

[Oscar]

Different piston skirt design, or maybe oil jets. It is very likely the piston crown runs too hot. We run CHT gauges but have no idea about piston temps, which is the other half of the combustion space. They way some look they are obviously HOT. Nev

CAMit is very aware of the piston crown heat problem / situation and I'm sure they have it 'on their list'. As with everything else they've done, we won't be told what they have found to be the answer until it's been tested thoroughly and found to be a) of positive benefit, and b) reliable and effective in real flying conditions.

 

 

[ianboag]

The Merlin - which normally fought day VFR - used a water-heated butterfly... with a 1,200hp heater...

There is no way that a coolant-heated butterfly could change the induction air temperature by any meaningful amount. It's basic heat transfer stuff - there's just not enough surface area or temperature difference. It doesn't matter how many hp are warming the coolant. If some ice forms on the butterfly it acts as an insulator, so the temperature of the butterfly goes up which melts the ice enough for it to detach. That doesn't need a lot of kw - think of the difference between heating your bedroom with a couple of kw or just using a 100w electric blanket in your bed ....

 

I'm talking about the physics, not the FAR 23 thing. The Merlin probably wasn't FAR 23 compliant either ..... :-)

 

 

[Russ]

Rotating the pistons 180* ( reverse the offset ) according to an engineer, makes good sense to jab engines. ( gave me the reasons why......long story )

 

 

[David Isaac]

Rotating the pistons 180* ( reverse the offset ) according to an engineer, makes good sense to jab engines. ( gave me the reasons why......long story )

There has been quite a bit of debate on that one issue Russ.

 

 

[Russ]

Thanks Dave.....mind pointing me there.....( save me trolling about )

 

 

[Bob Llewellyn]

There is no way that a coolant-heated butterfly could change the induction air temperature by any meaningful amount. It's basic heat transfer stuff - there's just not enough surface area or temperature difference. It doesn't matter how many hp are warming the coolant. If some ice forms on the butterfly it acts as an insulator, so the temperature of the butterfly goes up which melts the ice enough for it to detach. That doesn't need a lot of kw - think of the difference between heating your bedroom with a couple of kw or just using a 100w electric blanket in your bed ....I'm talking about the physics, not the FAR 23 thing. The Merlin probably wasn't FAR 23 compliant either ..... :-)

Indeed, that's why igloos are built of compressed snow, it's thermodynamics.

The point of the Merlin butterfly is simply that, rather than raise the air above impact icing temperature before the carby, RR ensured a high heat flow per square inch on the butterfly; the point of that being, when supercooled water droplets are ricochetting off the butterfly before ice has formed, the heat flow out of the butterfly is much greater than either caused by cold air alone, or after the butterfly is insulated with a nice blanket of ice. If you're not using a RR scale heat flow, the blanket of ice better not get too thick before it's cooked off, or it can simply choke the cold manifold downstream of the carby... The Rotax electric carby mitten is challenged just by the airflow and evaporating fuel cooling; supercooled droplets lead to ice, which, yes, soon breaks off in slabs. This does not garauntee immunity from power interuptions, which Rotax themselves state.

 

 

[Oscar]

Rotating the pistons 180* ( reverse the offset ) according to an engineer, makes good sense to jab engines. ( gave me the reasons why......long story )

Yes, the physics behind reversing the pistons appears pretty sound, though has certainly been the subject of debate (arguing slap vs thrust line). Additionally, Jabiru use a tighter piston-cylinder tolerance than most piston manufacturers recommend for an air-cooled engine, which I suspect may be a part of the reason that the standard Jab engine tends to be very tight just after shutdown; however I am not an engineer and my reasoning here may not be correct.

 

 

[facthunter]

The offset gudgeon pin holes are a left over from the fact that the pistons are from a car where quietness matters. They should be installed noting the direction of rotation and giving the least thrust on the firing stroke. Having them all the same would be a good start as it slightly affects the ignition timing. Due to a short rod to crank throw relationship, increasing the sidethrust is not a good idea, and it is a maximum on the power stroke. Nev.

 

 

[XAIRVTW]

I have sent an email to Ian with picture attached as soon as I get a reply I will post it for you.

Attached is the response from Ian at Camit.

Hi Tony.docx

 

Hi Tony.docx

 

Hi Tony.docx

[Oscar]

Great stuff!. I had it ALMOST correct... but as always, there's no better advice than you will get from 'the horses mouth', as it were. That response is 'classic' Ian Bent - not just what, but why and how things interact to produce results. If I sound overly enthusiastic, I probably should apologise to Ian if other people take this as unwarranted - but as a business systems analyst by (previous) profession, I spent a considerable part of my professional life looking at 'systems' to make sure that any changes were not just a band-aid to an obvious problem but did not introduce new problems ('the law of unintended consequences'). I suspect that there are quite a number of Jabiru engine owners who wonder if the same intellectual rigor had been applied to the introduction of hydraulic lifters...

 

The keen-eyed will note that Ian Bent's response contains an extract from another document. Suffice it to say that such a document might be a step along the way to a wider application for CAMit engines than for 19-reg aircraft. I'm guessing here, but having been involved in the preparation of an extensive EO for modifications and repairs to our aircraft so it can remain in 55-reg., there's a vague familiarity. Maybe presumptuous to say 'watch this space', but I'll be watching nonetheless.

 

 

[Garry Morgan]

Its only Camit motors for me now . Jabiru didn't listen to Ian when he wanted to improve the motor. It now will be one of the best motors you can by.

 

 

[facthunter]

It is commendable. I hope the results are significant reward for the effort. Nev

 

 

[Dafydd Llewellyn]

The system appears well-engineered, but is a patch on a bad design. Why not line the steel barrels with Nikasil and use appropriate rings?

Every additional process in the manufacture of (especially) a type-certificated product, involves an additional set of process controls, with audit, paper trail etc. A process like Nikasil is likely to involve a complete plant by itself. This would double the cost of the engine, for not much real benefit. Also, you cannot hone-out a Nikasik barrel to the next oversize, as you can with a plain steel barrel. The barrels are carrying the tensile load from the combustion pressure on the head, which has to be carried all the way down to the main bearing caps. Steel barrels will do that, aluminium ones won't; they need the head hold-down bolts to go all the way to the crankcase - which fouls up the finning and also the airflow through the fins.

Lycoming put plain steel barrels in the 0-320-E2A in the PA28-140; I had one. I made a point of doing a circuit or two in it once a week. It held full compression all the way to 2000 hours. Plain steel barrels are much less prone to glazing than nitrided ones. In short, plain steel barrels are a damn good practical compromise. Adding an inhibiting squirt to them sounds to me like a really smart solution. Zer Chermans do not go in for that sort of thing; they use unobtainium, but it's not so practical when it comes to overhaul time.

 

 

[Dafydd Llewellyn]

Not really. There are a lot of 912s flying round with zero carb heat and/or electric/coolant heated jackets on the manifold downstream of the butterfly. The aim being not to heat the air but just to melt ice off the manifold wall which of course needs far fewer kW and does not significantly change the air inlet temperature.

Horse ****. Firstly, the provision of induction heating is NOT a requirement for the engine manufacturer; go look at JAR 22H. It's a requirement for the AIRFRAME manufacturer. And there are no ifs or buts about it. It's in FAR 23.1093:

§ 23.1093 Induction system icing protection.

 

(a) Reciprocating engines. Each reciprocating engine air induction system must have means to prevent and eliminate icing. Unless this is done by other means, it must be shown that, in air free of visible moisture at a temperature of 30 °F.—

 

(1) Each airplane with sea level engines using conventional venturi carburetors has a preheater that can provide a heat rise of 90 °F. with the engines at 75 percent of maximum continuous power;

 

(2) Each airplane with altitude engines using conventional venturi carburetors has a preheater that can provide a heat rise of 120 °F. with the engines at 75 percent of maximum continuous power;

 

(3) Each airplane with altitude engines using fuel metering device tending to prevent icing has a preheater that, with the engines at 60 percent of maximum continuous power, can provide a heat rise of—

 

(i) 100 °F.; or

 

(ii) 40 °F., if a fluid deicing system meeting the requirements of §§23.1095 through 23.1099 is installed;

 

(4) Each airplane with sea level engine(s) using fuel metering device tending to prevent icing has a sheltered alternate source of air with a preheat of not less than 60 °F with the engines at 75 percent of maximum continuous power;

 

(5) Each airplane with sea level or altitude engine(s) using fuel injection systems having metering components on which impact ice may accumulate has a preheater capable of providing a heat rise of 75 °F when the engine is operating at 75 percent of its maximum continuous power; and

 

(6) Each airplane with sea level or altitude engine(s) using fuel injection systems not having fuel metering components projecting into the airstream on which ice may form, and introducing fuel into the air induction system downstream of any components or other obstruction on which ice produced by fuel evaporation may form, has a sheltered alternate source of air with a preheat of not less than 60 °F with the engines at 75 percent of its maximum continuous power.

 

(b) Turbine engines. (1) Each turbine engine and its air inlet system must operate throughout the flight power range of the engine (including idling), without the accumulation of ice on engine or inlet system components that would adversely affect engine operation or cause a serious loss of power or thrust—

 

(i) Under the icing conditions specified in appendix C of part 25 of this chapter; and

 

(ii) In snow, both falling and blowing, within the limitations established for the airplane for such operation.

 

(2) Each turbine engine must idle for 30 minutes on the ground, with the air bleed available for engine icing protection at its critical condition, without adverse effect, in an atmosphere that is at a temperature between 15° and 30 °F (between −9° and −1 °C) and has a liquid water content not less than 0.3 grams per cubic meter in the form of drops having a mean effective diameter not less than 20 microns, followed by momentary operation at takeoff power or thrust. During the 30 minutes of idle operation, the engine may be run up periodically to a moderate power or thrust setting in a manner acceptable to the Administrator.

 

© Reciprocating engines with Superchargers. For airplanes with reciprocating engines having superchargers to pressurize the air before it enters the fuel metering device, the heat rise in the air caused by that supercharging at any altitude may be utilized in determining compliance with paragraph (a) of this section if the heat rise utilized is that which will be available, automatically, for the applicable altitudes and operating condition because of supercharging.

 

[Amdt. 23-7, 34 FR 13095, Aug. 13, 1969, as amended by Amdt. 23–15, 39 FR 35460, Oct. 1, 1974; Amdt. 23–17, 41 FR 55465, Dec. 20, 1976; Amdt. 23–18, 42 FR 15041, Mar. 17, 1977; Amdt. 23–29, 49 FR 6847, Feb. 23, 1984; Amdt. 23–43, 58 FR 18973, Apr. 9, 1993; Amdt. 23–51, 61 FR 5137, Feb. 9, 1996]

 

You will find a similar requirement - somewhat watered down in some cases - in all aircraft certification requirements.

 

Of course, with a homebuilt experimental, you can ignore this - which in my books should qualify you as a Darwin Award candidate.

 

 

[Old Koreelah]

...you cannot hone-out a Nikasik barrel to the next oversize, as you can with a plain steel barrel...

I discovered this in 1982 when my mechanic tried to bore out the barrels of my wife's Moto Guzzi. He broke every tool he tried, then finally gave up. Strangly, the reason for trying a bore-out was extreme localised wear on the bores; the crank bearings were so sloppy that shaft movement allowed the pistons to flap all over the place.

 

 

[facthunter]

Through bolting with alloy cylinders/heads has another difficulty with differential expansion rates. Some parts get cooled more than others. some studs are encased in thin pipe to adjust the cooling effect. the Bentley rotary used studs. I don't know how they overcame the problem. Nev

 

 

[Dafydd Llewellyn]

Horse ****. Firstly, the provision of induction heating is NOT a requirement for the engine manufacturer; go look at JAR 22H. It's a requirement for the AIRFRAME manufacturer. And there are no ifs or buts about it. It's in FAR 23.1093:§ 23.1093 Induction system icing protection.

 

(a) Reciprocating engines. Each reciprocating engine air induction system must have means to prevent and eliminate icing. Unless this is done by other means, it must be shown that, in air free of visible moisture at a temperature of 30 °F.—

The "unless this is done by other means" allows scope for the airframe manufacturer to embark on a research project to evolve an alternative means, and prove to the satisfaction of the certificating authority that it works. Fine, if you happen to be a State-funded aeronautical research organisation; might get a Master's paper out of it - maybe.

 

However, this is a case where the design standard provides a means of compliance that the manufacturer can apply without having to set his program back by months and maybe a hundred thousand dollars, simply by having an exhaust muff and a simple valve operated by a bicycle handbrake cable. It relies on the experimental fact that a 50C rise in temperature upstream of the carburettor, will give a 15C rise in the temperature in the carbie throat downstream of where the fuel is admitted. Pulling full carbie heat does NOT raise the temperature of the air reaching the cylinders by 50C; the rise is around 15C, due to the latent heat of vaporisation of the fuel. Provided the carburettor bowl venting is done correctly, there will be almost no perceptible power loss (This can be observed in the Gazelle; it was one of the few things that were done - eventually - very well, in that aircraft).

 

The route to less costly certification is to have a greater proportion of the design standard codified in this sort of manner. CAR 3 used to be largely codified; unfortunately, Ralph Nader pointed out that government should legislate for the end, rather than for the means. That resulted in FAR 23 being written to a far greater degree in the style of the required end result, without specifying how that could be achieved. Fortunately, the FAA then set about writing a whole library of Advisory Circulars that specify "acceptable means of compliance". Almost all the recreational aircraft standards that have appeared since, are watered-down versions of FAR 23 - usually with the same numbering system - but without the Advisory Circulars. So much for "progress".

 

So, nowadays, one has to look up the requirement, and then go hunting for the current version of the AC that addresses it. If you use the means of compliance given in the AC, the certificating authority will usually rubber-stamp it. If you choose to invent a new way, this brings the certification process to a dead stop whilst the certificating authority researches the matter and satisfies itself that your method is acceptable. Meanwhile, the Applicant's finances are steadily running out. Being clever is a real good way to go broke, trying to certificate an aeronautical product.

 

So, how smart is it to muck about with electric heating pads on the induction system? The gain is likely to be very small, and the overall cost, staggering. If you want to play about with such alternative methods on your homebuilt, fine. But if you just want a safe aircraft to fly, simply follow what is already a proven means.

 

 

[geoffreywh]

Dafydd said " you cannot bore out a Nikasil barrel to the next oversize, as you can with a plain steel barrel" .................... Mainly True................. But this statement is dodgy on two counts....one being that nobody bores out Nikasil barrels anyway, and why should they? It's simple enough to de-electroplate the barrel, repair any damage in the alloy and replate. I have had it done. The second is "as you can with a plain steel barrel" Good luck with boring a Jabiru barrel 20thou oversize. If they break at full size, they may break quicker with a thinner wall?.....By all means try to replace the steel barrel with an alternative, please.....

 

 

[Keenaviator]

Dafydd said " you cannot bore out a Nikasil barrel to the next oversize, as you can with a plain steel barrel" .................... Mainly True................. But this statement is dodgy on two counts....one being that nobody bores out Nikasil barrels anyway, and why should they? It's simple enough to de-electroplate the barrel, repair any damage in the alloy and replate. I have had it done. The second is "as you can with a plain steel barrel" Good luck with boring a Jabiru barrel 20thou oversize. If they break at full size, they may break quicker with a thinner wall?.....By all means try to replace the steel barrel with an alternative, please.....

Do Jabiru cylinders break? Laurie

 

 

[Gpshaun]

Just a link to the plating process http://www.nzcylinders.com/Our%20plating%20process.html

 

 

[Oscar]

Do Jabiru cylinders break? Laurie

It would be interesting to know about the statistical incidence of that. What the standard barrels certainly DO, is bend at the base flange (particularly under detonation) and thus add a major stretching moment to the through bolts that either breaks them or reduces the clamping force so the crankcases start working (or 'fretting') against each other that starts a chain of minor damage that then continues with compounding results. The thicker bases that CAMit have introduced in conjunction with the inhibition on shutdown idea seems to me to be a sensible and cost-effective way to be able to employ steel barrels.

 

 

[Dafydd Llewellyn]

Dafydd said " you cannot bore out a Nikasil barrel to the next oversize, as you can with a plain steel barrel" .................... Mainly True................. But this statement is dodgy on two counts....one being that nobody bores out Nikasil barrels anyway, and why should they? It's simple enough to de-electroplate the barrel, repair any damage in the alloy and replate. I have had it done. The second is "as you can with a plain steel barrel" Good luck with boring a Jabiru barrel 20thou oversize. If they break at full size, they may break quicker with a thinner wall?.....By all means try to replace the steel barrel with an alternative, please.....

Firstly, I said "hone", not "Rebore" - there's a difference, you know. The hone finish is critical for oil retention. Secondly, I was talking about CAMIT barrels, not Jabiru barrels.

Also, what I said about process control holds; putting a steel barrel into an electroplating or stripping bath? Ever hear of hydrogen embrittlement?

 

CAMIT works under a CASA Production Certificate; we're not talking about motorcycle engines, here.

 

 

[geoffreywh]

errrrr? forget I said anything.........god speed