---------------------------------------------------------- Europa-List Digest Archive --- Total Messages Posted Thu 07/20/17: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:18 PM - Re: Re: Rotax Engine Alternatives - Aeromomentum (Pete) ________________________________ Message 1 _____________________________________ Time: 12:18:51 PM PST US Subject: Re: Europa-List: Re: Rotax Engine Alternatives - Aeromomentum From: Pete I have no first hand experience, but have been watching these auto conversio ns for many years. My conclusion is that the gearbox is always the weakest l ink. The Honda fit core for example is an amazingly durable engine (also use d in their outboard marine engines). The issue with the geared engines is o ne of harmonic resonance - but contrary to what most think the issue is not w hen loaded, but rather when the prop is unloaded - typically at idle or on a pproach. Regardless of the engine's HP, when resonance feedback peaks it ca n be very destructive, needing to dissipate possibly hundreds of HP to dampe n it back down. The simple rubber isolators used by Viking (and also aeromo mentum) are IMHO totally inadequate...... indicated finally by a VIking in-f light failure (I expect more to come). Rotax have dealt with the issue usi ng dog-clutches etc., a high idle and other tricks? Could it be that the ai rboat application mentioned is different in that the engine is either at idl e (normally set above the resonance frequency to avoid the issue) or high po wer.... no approach-no-prop-load conditions. I concur that if one is only looking to save money: don't - go with the rot ax, or a direct-drive non-geared engine, it will be cheaper in the long-run ( no bent airplane parts). As others have already mentioned an auto-conversio n is an exercise in engineering ... which can be a fun and rewarding effort. Cheers, Pete A239 PS - Looks as if the D-Motor folks are getting their act together and will s oon have a very nice liquid cooled, light, direct drive, simple, durable eng ine - the 6cyl will be about equivalent to the 914 (tho not normalized obvio usly). PPS- At osh now.... the place is looking good and the weather is great. B52 j ust landed. Don't forget to drop by and grab a beer/pop :-) > On Jul 19, 2017, at 11:11 AM, GTH wrote: > > >> Le 19/07/2017 =C3- 12:37, graemeh a =C3=A9crit : >> I realise that installing an alternative engine will be more work and tak e more time. My challenge is to assess the extra build time vs how long it w ould take me to save for the Rotax and also add in a risk factor to allow fo r the extra risk in going for an alternative engine. >> >> [...] >> Thanks again for all who have contributed and I'd appreciate hearing furt her from anyone with direct experience in using alternative engines (on a Eu ropa or other aircraft). > Graeme and all, > > As one who made an alternative engine *installation* albeit with a proven e ngine, I hope you'll allow me to express my opinion ;-) > Devising a correct engine installation from scratch is not really the prob lem. It takes time, research an lots of common sense, you'll find lots of in fo on Contrails ! > > The problem is with those alternative engines. The best way would be to in terview several knowledgeable people with direct experience of a working ins tallation, and a few hundred (preferably thousand) happy engine flight hours in their logbook. > But if those people did exist, then we would not be talking about an *alte rnative* engine, but about a *proven* engine. > > Bottom line, if you have time and money, and are eager to help develop the engine, by all means go for it. You'll be a pioneer, have lots of fun, lear n lots of things, and discover there is no substitute for thousands of engin eer hours, test cell time, destroyed engines, and thousands of flight hours b efore you achieve a reliable aero engine. > > But don't trust the degree on the wall, the videos and the "we addressed t he torsional" blah blah. Ask for the blueprints, the actual number of engine s actually flying, the address of actual users atctually flying the engine, s tudy the Service Bulletins - if there are none, caveat emptor, the engine ha s no flight experience. > > On the other hand, if money, or time, or workshop equipment is key, then g o for a Rotax (even a second hand one), devise a correct cooling installatio n, and you'll soon be a member of the happy flyer-builder family. > > FWIW > > > -- > Best regards, > Gilles > http://contrails.free.fr > http://lapierre.skunkworks.free.fr ========================== ========= ========================== ========= ========================== ========= ========================== ========= ========================== ========= > > > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message europa-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Europa-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/europa-list Browse Digests http://www.matronics.com/digest/europa-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.