We promised that following the Sun N’ Fun Air show, we would provide an in-depth report on exactly what was happening on the power plant development and installation program.  We also said that we would be collecting funds from those who wanted to utilize the 700cc Rotax version.  What we saw at Sun N’ Fun however has

simply changed everything.


            We’ll begin this report by recapping the positives and negatives of the 700 cc development to date:



                        1.         We successfully completed a dyno test program and installed the package in the HELICYCLE©.

                        2.         The installation is light and powerful.

                        3.         The fuel specifics are good – SFC. .61 -.63

                        4.         The installation fits the engine mount in the first and second production run airframes.



                        1.         Rotax wants nothing to do with helicopters and refuses any assistance.  They no longer supply a short block.  You have to bolt water jackets, heads and accessories together yourself.

                        2.         We have not yet been able to make the pattern for a 2 plug head.

                        3.         The electromotive ignition system we have very successfully used in the past is not working well at our 6300 RPM.

                        4.         The mechanical carburation we are using is okay for our experience, however we are unsure of how easy it will be for our builders to adjust.

                        5.         The costs of the rotax engine pieces continues to escalate way out of proportion to inflation.


            A report on the progress with the Rotax 912, four stroke:

                        1.         Enclosed is a photo sheet with captions.

                        2.         The Rotax 912 according to factory specs has 80 hp at w.o.t. & 5500 rpm with 77 ft. lbs. of torque.  These numbers seem a little inflated to us.  We don’t have time to check it out on the dyno, if the numbers are correct they are almost equal to the 700 cc engine.

                        3.         With a 2 hour range the 912 will weigh only 25 lbs. Net over the two stroke.

                        4.         We will have to subcontract the exhaust system, this may get a tad pricey; it has to be stainless and has lots of bends and flexible connections.  A typical commercial set up.

                        5.         We plan to have the 912 installation operating at Arlington (July 10-14).  We will know a lot more about the performance by then.  Reliability and over haul times should be better than the 2 stroke, however if the engine has to work hard to put out 65 - 70 hp, reliability and durability could suffer.  We did not want to start out using the 100 hp 914, it’s much more expensive and the 10.6/1 comp. ratio gives us some heart burn.  Our plan if all goes well with the 912  80 hp is to pass along our O.E.M. savings to our builders so that the cost of the engine installation kit will be mostly off set.

                        6.         The 912 installation is more complex than the 2-stroke.

                        7.         The 912 and a 220 lb. pilot plus full fuel (10-12 gal.) is probably not the best recipe.  A 190-200 lb. pilot would be a happier situation.

                        8.         We’re really looking forward to flying with the 912.  It represents a great 4-stroke option, in any case.


        See the 912 flying in the Helicycle at Arlington 2002


            Okay, what changed everything at Sun N’ Fun.??


            I was standing on the trailer next to the HELICYCLE giving a dissertation.  After I finished, two gentlemen came forward and shook hands.  One was Siegfried Gobler the president and owner of Hirth Motors and the other was his chief engineer.  They began to tell me about the helicopter power plant they had been developing and were now ready to produce.  The engineer spoke fluent English and we got our heads together in spades. A photo page and captions on this power plant is enclosed and here are some interesting stats.


                        1.         This 2-stroke is 939 cc’s, but will weigh only 10-13 lbs more than our 700 cc Rotax installation.

                        2.         3 cylinders don’t need a large tuned exhaust.  Their aluminum after-muffler weighs only 6 lbs.

                        3.         The power plant makes 87 hp at only 5000 rpm.

                        4.         The engine has duel ignition and is electronically fuel injected.  Altitude is automatically compensated for.  Normally we’re not real excited about single redundancy electronic fuel injection systems,

                                    however Hirth really seems to have done their homework on this one.

                        5.         They want to work with us and are willing to modify their crankcase patterns for our engine mount requirements.

                        6.         The engine is properly oil injected.

                        7.         The best news is a reasonable price of $6-7,000.  This includes all accessories, starter and exhaust manifold.  We can’t come close to this price with the Rotax 700 cc.


            We made the decision to have Hirth build an engine for the HELICYCLE.   They quoted a 4 month delivery.  We should be finished with the 912 program before then and have most of the parts ready to mount their engine as soon as we receive it.




            We realize a dozen or so of our first production run builders are getting pretty fidgety about the engine situation and so are we.  Do you remember the movie Cat Bellou?  Lee Marvin was very drunk and leaning against a wall while astride an old nag.  His partner comes up and says, “what a time for you to fall off the wagon, just look at your eyes!”  Marvin replies, “hey, you should see them from the inside.”


            All we can say is, “ hey, you should have fought this alligator from our side.”  We’re soooo glad this power plant nightmare is almost over we can’t shout hooray loud enough!


Stay on the bandwagon, it’ll be worth it!!

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From 12-27-2004