gcrowder2
Joined: 09 Jan 2006
Posts: 136
Location: Golden, Colorado USA
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 Posted: Sat Aug 02, 2008 7:26 am Post subject: Hornet LSA flies with the Rotamax 2 rotor |
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.ExternalClass .EC_hmmessage P {padding:0px;} .ExternalClass body.EC_hmmessage {font-size:10pt;font-family:Tahoma;} This post is forwarded from the Rotary Aviation list
Glenn
| Quote: | Date: Fri C 1 Aug 2008 06:48:55 -0700
From: rotaryeng(at)earthlink.net
To: rotaryeng(at)earthlink.net
Subject: Hornet flies with the Rotamax 2 rotor
The Hornet guys got a few hours flying the 2 rotor Rotamax powered
airplane before departing to OSH. Unfortunately I did not get a video
yet. The muffler is half a spin tech and it is rather quiet.
The rubber gear box coupling was replaced with a 50 durometer version
down from the original 60 durometer version with a noticeable reduction
in idle speed. 50 durometer is the lowest available for that brand
of coupling. Like all geared 2 rotor aircraft engines they tend to
resonate around 1800 RPM. The quick and simple cooling system
worked great despite being installed BEHIND the cargo pad 
That is the president of Hornet (Robert) removing the gear box from the
engine.
The Hornet is a cute little airplane. I can imagine having fun with
something like that. I am surprised it is using the RotaMax two
rotor--as that seems like a lot of engine for this aircraft. But I
am just guessing what its hp/weight requirements might be. So C how
did it perform? Two more observations: first C that narrow motor
mount will take some getting used to. I would not be comfortable with
it. And C secondly C how big is the fuel tank? I think the two rotor
will be thirsty. Jerry
It was estimated at about 480 gallons an hour based on the half
gallon of fuel burned in 3.7 minutes. Not an accurate way of
measuring the fuel burn. A rather unlikely number in fact.
Something wrong there. Perhaps my notes are wrong.
The static RPM was about 5000 with a 1.9 gear box. From the Rotamax
web site: 4750 is about 100 HP. Engine weight claimed is 145 pounds.
Assuming it is 100 HP a BSFC of .6 would be 60 pounds an hour or 10
gallons an hour. A much better guess. It is not like you are going
on long cross country flights with an LSA anyway so fuel burn is not
much of an issue. The claimed engine weight is 145 pounds. The 80
HP Rotax 912 engine weighs 132 pounds. That is about 100 pounds less
than a Subaru.
The big advantage right at the moment is the cost.
It is about $5000 cheaper than a Rotax 912 I am guessing.
They also flew the airplane briefly direct drive with a max RPM of
3000. The power must of been down around 50 HP and that is how the
airplane flew. Like it had 50 HP. The Hornet has flown before
with low HP engines as it was close to an ultralight concept in it's
early days. In other words it has a lot of wing area for its weight.
Apparently C and as far as I can determine C the RPM C HP and therefore
the gear ratio is limited by the rotor needle bearings. Currently
they are using a composite needle cage which may be softening as the
rotor temperature is quite high. An easy change would be to use a
steel needle cage. Rotamax could easily test that hypothesis. The
loads on the rotor bearings are a minimum at 6000 RPM. If they can
get the RPM up to 6000 there should be another 20 HP available or
about 120 HP total. That would make it suitable for some
experimental aircraft. It would also make the
60 HP one rotor version more competitive with the 80 HP Rotax 912.
That should take another $5000 out of the cost of an LSA.
Paul Lamar
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I think the fuel consumption stated in the first paragraph should
work out to about 8 gph at 5000 rpm/100 hp. Jerry
Lets see 60 minutes divided by 3.7 is about 16.2 So 16.2 times
one half gallon is 8 gallons and hour. You are right Jerry. My
mistake. So 8.1 gallons an hour is 48 pounds of fuel per hour. Ah
so that is were the mistake is. 48.6 pounds divided by 100 HP is
.486 BSFC. Rather good if it was actually making 100 HP.
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