Jethro Belle

Thanks for confirming @Yenn. I noted your post in #158. I was hoping you may be able to shed more light since it was a while ago. What sort of improvement was expected? Was it a problem with operation due to head quality? After searching more I found the Liquid cooled heads thread which is probably where any reply should be posted (sorry TP). Reading both that thread and Rotec Liquid Cooled Heads for Jabiru Engines clearly indicates that water cooled heads solved overheating problems ( ) even for those who felt Rotec quality was very inadequate. The fact that quality sand casting of aluminium is difficult, and requires inert gas blanketing to avoid porosity and other problems, seems to be a major issue (Something D-Motor is struggling with also), but some simple machining quality reports leaves me wondering . Most people seem to claim their system over-cooled! While Nev believes in air-cooled simplicity, he also states that a leaner mixture is possible when heat is not an issue, and so better fuel economy should be possible with LCH, offsetting some of the additional weight. I take it your friend noticed no improvements in fuel economy either?

Yes the starter post was about CH-701 engines. Sorry for subverting the thread to a wider engine discussion

Yes please John. I haven't heard overheating in a rev range Keen to learn about real experiences and how problems are avoided by some and not others. Unless Jabiru owners are a different breed to Rotax owners, it can't all be down to maintenance and operational factors (IMHO). My preferred engine would be a reliable Jabiru. A VH registered J430 would allow me to take my children flying and second hand ones are available at 'good' prices, but the engine issues put me off. I suspect the 'good' second hand prices are related to the engine issues. I am unaware of other problems.

I think it probably is also (more like rapid thermal changes), but clearly there is some issue with at least the older Jabiru heads and the centre cylinders (from memory) of the six, or the 'fixes' would not be dreamed up/ marketed. My reply was pointing out that adding two cylinders seems to make the thermal control more problematic, not better. More is not always better

Agree about smoothness and desirability. Acquiring a six cylinder Jabiru was a serious consideration me, but when reading about them I came across threads discussing the problems six owners have with uneven temperatures and "thermal shock" from touch and go training! Some where fitting CHT to every cylinder to keep them 'safe'. That is when I became aware of the Rotec WC heads! I think the "thermal shock" discussion was UK based, where they may encounter far colder conditions than average for Australia.

Yes. That was my starting opinion. I wish it wasn't so obvious and boring I hope Jabiru can challenge Rotax, but suspect lengthening the fins any more is chasing diminishing returns and physics rules the day. Rotec water cooled heads on the Jabiru would change the physics. I have found some limited discussions initiated by @Yenn on the Jabiru Engine 2200 Mechanical Problem Reporting but no posts since from anyone using them. Anyone have/heard good reports?

Thanks for posting about your ex-Sonerai. It looks/looked like a nice one. Do you believe it is possible to 'cool' any VW enough for service in Australia without derating power output IYO? Academically I am interested about how much the power output from an air-cooled engine (say the 2 L factory rated at ~70hp for intermittent full power and prone to overheating on the road) can be increased for WOT application in an aircraft without the inevitable top end overheating. You can increase power output by increasing BMEP, boring, stroking etc, but you can't change air-cooling fins much, so that limit is built in. Only increased forced/ram air will raise the cooling effectiveness. My experience with road VW beetles and Kombis is WA is that motors failed if you drove them hard for long distances on a hot day. I did it twice, but they were not pristine engines, so not saying all were so prone. I grew up in one of those 1100cc reduction hubs split screens that now fetch a gazzilion dollars, and can't see how such a heap of s$@t has improved that much since then Before I am flamed, it was brilliant in some ways, but it was without doubt a SLOW with a death trap swinging rear axle, drum braked cross-ply shod .... Oh and the carbon monoxide poisoning heater option

Yes we are, I think (not to fly across Bass straight: Just local fun and practice for low $). That is what powers stock Sonerai. I know there are many installed and it has a long track record (Without it I doubt I would look at the 'Beetle' motor), so I will check proven-builds and statistics if I go that way. I think that motor is a legacy item now, rather than what you (I) would install in a new build. The Corby Starlet is a nice little aircraft and performance specs seem good. Some Starlets have been outfitted with 2180's (75-80 hp) and these cruise at VNE (185) and climb at 1900 fpm. That is upgraded Sonerai territory! I like having the second seat of the Sonerai II, but its fuel tank location worries me. I see Aaron25 "Sonerai IIL For Sale" had cooked the orignal VW motor, so @Marty_d is on the money I found the LycomingThunderbolt Engine which is red, and red Lycoming from If You’re Looking for Horsepower and Reliability You’ve Come to the Right Place! - Aero Sport Power and Superior Air Parts :: Features and Benefits of unknown colour. What is the RED superior Lycoming you keep mentioning?

Per the Small aircraft crashworthiness thread the consensus was 'pole vaulting' it above your head through clever collapse of the support. Easy for a high or pylon mount, but not an engine embedded at the rear of the cockpit. This is were a @Dafydd infinitely rigid crash cocoon is needed :pizza:Shame he isn't online anymore. My solution is a close mounted twin arrangement, arranged so the engines flick out and around to the side. I like safety through redundancy, as cost/difficulty skyrockets (say exponentially) as you pursue extreme safety of a single failure route. The question is: can duplication be done cheaper than reducing risk with a single fail route design? If duplication doubles cost, then a risk level is reached when it is the best option, but that is a different thread. Two small auto-derivatives made 'safe enough' may well be cheeper than a single aeroengine. To avoid asymmetric thrust I have considered 'clever' duct design etc etc, but it all adds weight and reduces efficiency and I am no genius to think I can do it when so many others have failed. I wouldn't go with long drive shafts. Bugatti proved that wasn't real good. Several aircraft have been designed such that a drive shaft (passing near the pilot) failure would chew up the pilot I have imagined long drive belts. They would have their own slapping vibration issues and require a stiff heavy rigid structure. Of course both could do it and have done it. It is how reliable and safe they are.

Could you elaborate what tank features would be good please Nev? Bladders? Inversion valves? Foam? I had not thought of flipping a low wing like the Sonerai Thanks for the hazard identification. Not an easy risk to mitigate because roll cage would not be light or easy to retrofit. Has any low/mid wing forum members successfully mitigated the this risk, or know how to?

Just browsing diesel and electric ( A great idea) progress and notice that development has generated is first statistics. More details can be found here. Basically it is a Smart Car engine in series with a 50 kW electric motor done by Magnus and Siemens! Rather sums up all that my posts have said. Magnus and Siemens should know what they are doing. A Tesla model S in flames on the ground is bad! I hope this doesn't kill it. The Ecodiesel itself may be an interesting option for some. I have good reports from smart car owners They also have a petrol offering 22 hp more for 10kg less!

Yes it always interested me since I first saw a picture of the Custer as a boy Hellish wing construction. With power on you will get more lift! Never could work out if it was a good or silly idea (ignoring stone chip protection). Less complaints abut flying activities was probably not on the inventors mind back in them good ole days. You may like to build yourself the Stealth SSDR Archon SF-1 kit It is @Litespeed mount in his avitar image It is effectively a channel wing even though they call it a flying fueselage aircraft. Or just build a Custer patent number D176839 :spot on:

Yes, good thinking, but efficiency drops at RA air-speeds as the 'propulsion disk' reduces in diameter. The duct weight offsets some/all of a gearbox weight and a G/B allows a larger (more efficient) prop diameter. Placing equipment in the duct may look neat, but it will be in the highest velocity region = high drag. Ducts around the fuselage doubles the area exposed to high velocity so more drag. Turbo-fans work as a unit with the high pressure jet in high velocity aircraft. They generate significant pressure differential, and to my understanding that is when the duct becomes effective by avoiding tip re-circulation, especially at low speeds such as on take-off. Original turbo-fans were direct drive from the power turbine. Striving for increased efficiency has seen gearboxes added to drive larger bypass fans in the high-bypass designs filling the gap up to turboprops. My understanding is the turbo-props don't do near sub-transonic speeds (probably because the tip speed must be kept subsonic). I have done almost nothing with jet engines (undergrad thermo-labs and theory) so hopefully someone who is can post. They are an engineering field in their own right.

You mean like an RA version the Edgely Optica or the Ligeti Stratos? The Optica was claimed to quiet (see the linked article and Utube videos). I am with you, because small RPT turbo props seem to make more noise than larger Turbo-Jets, but the paper I found suggests otherwise, so cannot be ignored without sound reasons. In the case of the Optica the duct is 'propeller' sized, so I think it controls tip noise without generating much jet turbulence. You are however pulling a lot more drag and weight with a duct that size. A rear mounted engine puts the noise behind you and a duct will avoid stone chips so it has merits (unlike the Long-Ez) . Crash survivability with the engine behind you needs considering. A ducted propeller is safer on the ground.

Yes, and other things. To mitigate risk on such an aircraft you would need to seriously avoid Tiger country or do serious/regular engine checks/upgrades or run something like the hybrid Axter or the Pipstrel system. A BRS would be on my list to consider, plus some AAI MOOC CREEP crash survivability upgrades. That is why I am not rushing into anything, as figuring it all out will take me a while. Cooling seems to be hot topic of discussion on relevant forums I have read, however I am not sure it is particularly worse than other air cooled engines, is it? A matter of getting your cooling air-flow set up correctly, and that is not really the engine. Of course if the VW output has been significantly increased over stock (it has to be), it would be running into the heat dissipation limits as has been well explained by @turboplanner. What is your take Marty?

I think @skippydiesel was referring to tips going supersonic noise, rather than them failing mechanically. I too thought ducted fans could be made quieter than a prop, but according NASA JPL Tech-Report 32-7462" A Review of Aerodynamic Noise From Propellers,Rotors, and Lift Fans" by Jack E. Marte 1970 so you are correct! source: JPL TechReport 32-7462 The difference is not great, and I suspect the 'higher frequencies' from ducted fans may be easier to exclude from a cockpit. I suspect reduction in tip noise is less than jet turbulence noise increase, so maybe a wavy exit nozzle as appears on some modern Turbo jets may help. Does anyone have first hand knowledge? I only know my RC electric 'jet' whines, unlike my RC electric prop aircraft.

Impressive Did you do the calculation about how many tonnes force the piston-rod combination was placing on your cranks at that speed?

To challenge accepted wisdom is healthy, to ridicule those who believe it is more than expressing humble opinion. I qualified most of my comments and stand by them. I have thermodynamic mechanical lecturer engineering background, plus over 40 years of working on auto-engines, so feel able to post. Your post reminds me of students I taught who "knew everything". Like you I am hoping that those who have done conversions or have greater expertise/experience are good enough to post corrections. If you take a car racing (unless it is exceptional) you upgrade a heap of things including cooling. The conventional wisdom ensures cowboys (if they listen) don't bolt a motor straight out of a car into an aeroplane and expect it the be reliable and have a long life. It does not say you can't start with one and modify it up to work in an aircraft (The questions are: 1) Is is worth it? 2) Is it safe?). Everyone who has followed various aero-conversions with interest knows only a precious few live up to what is claimed in the original press coverage, and even less continue in production today and those move away from their automotive origins each 'upgrade'. You are correct that many car engines have been converted for use in experimental aircraft where safety is not highly process regulated and those doing it take the risk. Those transplants targeted are exceptional engines (most older car engines were not suitable) I am not sure what your point is. My understanding is the Rotax Brand originated from snow-mobiles, which I place in the high performance motorbike class. Where is the humour The fact that Rotax (who have proven themselves to know what they are doing) have chosen push rods shows that decisions must be based upon sound engineering, not pulp-fiction SciFi. What is your conspiracy theory about what Rotax is holding back? Something Bill Gates said? I notice Bill Gates made a big loss on the EcoMotors deisel. I am inspired by those who have successfully used auto-derivatives in aircraft, but do not underestimate how hard it is to make it safe, reliable and long lived. I suspect if the time and modification costs is fully accounted for, those who have done it from scratch will say a Rotax/Lycomtinental would have been cheaper. If you are building to an existing proven conversion, you will be financially in front on capital cost and probably fuel cost or you wouldn't do it, but IMHO you are part of the test pilot elite. I am considering VW conversion aeroplanes, so I am in no way ridiculing anyone who flies behind an 'interesting' engine. If I do go that way I want to have the risks correctly identified so appropriate mitigation back to better than Rotax/Lycomtinental level (my target: not imposing on others who like riskier lives) can be implemented.

As an afterthought Bex, do you think the Peugeot diesel would last 10000 hours operating at its redline? My post indicated that to my knowledge auto-engine manufacturers test against a typical load cycle, not at a fixed maximum speed like aero-engine manufacturers.

Check out the Edgley Optica. I am pretty sure early plans were for it to be rotary driven, but common sense (certification) got in the way when it was built. Even with the Lycoming it suffered some crashes and buyers lost interest. My take is that a ducted fan would only make sense as a styling exercise or to avoid stone chips on normal speed RAA aircraft. Maybe for low noise also. A high speed small diameter fan will not match a low-speed large diameter propeller efficiency and the ducts can add significant weight and drag. They also tend to be more speed specific in my understanding. A mock 'fighter jet' aircraft is the only situation I could see a rotary powered, direct drive, ducted fan makes any 'sense' ! Not efficient, but a more appropriate noise, reliability and fuel consumption

A good data point performance on the Suzuki G13B. Thanks Bex. An exceptional engine. I suspect the 'myth' originates partly comes from British/Australian/US... motors (pre-1980 say) and that it is possible to specify and allow a peak power output much higher than the thermal ability of an engine to deal with for more than a few minutes. Good for sales and quarter-mile drag figures In automotive use engines seldom run WOT and I would never do it, especially on a hot day, as my costly experience is that it results in engine failure. Maybe youngsters haven't experienced that, or ECUs "idiot proof" cars nowadays. A con-rod certainly knows if it is operating at red-line revs (aviation or road). Due to weight restrictions aircraft need to push red-lines to develop enough power to weight. No mystery. Lycomtinentals (all reputable aero-engines) are designed/tested from scratch to be run all day at the power outputs they quote. Ex-motor cycle engine manufactures seem to have an edge in aeroconversions (IMHO). There is usually some origin to myths. I am dubious about any high quoted power output engines unless extensive testing or usage verifies it is possible. It is easy to get extended engine life by 'derating' it. For an unknown engine it is still a 'myth' I am comfortable with, if for no other reason than I will get twice the engine life.

Apart from tetra-ethyl lead increasing octane, I understood coating the exhaust valve seat are it key actions (ignoring the exhaust slowly poisoning everyone ) Can you explain your statement please? Why is the Rotax 912's different?

I wasn't doubting you FT. Just expressing surprise this was the case as it is counter intuitive to me at least (always learning). I guess you concluded Wankels were not for you in the end? What was your conclusion? You have done the exercise obviously.

Off course Chill Nev. @Old Koreelah did indicate That seems to refer to test dynamo-meters in the Pug test facility, and Peugeot motors (always had a good reputation for reliability (until recent electronic gremlins) could achieve that under those conditions. I doubt it was full noise for that period, but some load cycle representing typical vehicles use (as you keep reminding us ;-). I hope @Old Koreelah will be kind enough to post more so we can get the actual in-plane performance and engine life so far. A very exciting case study.

Thanks Nev, I agree with all you say, but my musing was why they need to when auto-derivatives don't. I picked it up from the Lycoming site discussing why not to use motorcar oils that alerted me to it. Why do hot air-cooled heads require greater clearances on Lycomtinentals and not VW and Jabiru? I don't see your reply answers that. Hot heads would increase the clearance at the top of the piston stroke, not reduce it, which prima facie is opposite to running large clearances. Maybe their 'large clearance' is code for heat expansion caused by hot heads I am interested because the Rotec build water cooled heads for Jabiru engines and the same must apply to them, even though oil burning is not something I read about Jab engines.