View Full Version : Finally Complete and photographed
08-24-2004, 12:25 PM
I completed the addition of my new 912S engine, streamline tube frame, new shock gear system, prop, prerotator, instruments, etc. and took some photos.
If anyone wants to see the new work please visit my web site (Ken's Gyro below) and click on "New Engine" and "4".
08-24-2004, 12:36 PM
Looks different, but still terrific!
08-24-2004, 01:10 PM
Just a question, if you moved the HS up to where the bar is on top of your rudders wouldn't this help deflect some of the torque roll. It would basically act as a tall tail but on its side... Or am I smoking something? Of coarse you would probably have to beef it up quite a bit.
08-24-2004, 03:23 PM
Nice gyro and all it is lacking is a nice tall tail like on a Dominator.
08-24-2004, 03:50 PM
You sure love stirring the Sh*t don't you!
08-24-2004, 06:25 PM
I am not stirring it Mike, I am being serious. Ken is having problems with all the torque of that 912 engine and a tall tail would have his machine flying straight and true. Anyway I guess I could have sugarcoated it, but I don't usually do that. I guess that is one of my better - or more likely worse - traits.
08-25-2004, 08:18 AM
Toby (and Ron),
Yes, I have designed a new tail as you suggested - moving the HS up to the center of the prop. To make it strong they would no longer be "full flying" rudders, but fixed vertical fins with hinged rudder surface at the rear (typical rudder design). This is on my list of "things to do", but for now I just want to enjoy flying the gyro for a while and make all the fine tune adjustments.
I still need to alter my rotor head teeter towers so I can put on the new Sport Rotor blades. This is a wonderful hobby, as it will never be finished!
Thanks for your advise.
08-25-2004, 02:41 PM
You're gonna love em' Ken. Did you see the covers he sells for the blades?
08-25-2004, 05:01 PM
No, I didn't know about the covers. I checked out their web site and saw them. Thanks.
Do you have them? If so, are they padded inside? Will the blades with the covers fit in the blade box for traveling?
Can you lend me $160? ;)
08-26-2004, 03:13 AM
Ken, your workmanship is a lesson for us. Thanks.
08-26-2004, 02:57 PM
Ken, did you paint the valve covers? I thought they were color-coded so that the "S" model covers were green and the 80 hp ones were some other color... or is it I who's smoking something?
I'd expect a full-span centered HS to get rid of a lot of the prop's rolling torque. Not quite all, though, if my 912S Dominator is any guide.
08-26-2004, 05:51 PM
Yes, I did paint the valve covers red. The green just didn't look good with my red, white and blue color scheme.
Apparently the 912 engines have different color covers: black = 80 hp, green = 100 hp and red = 115 hp. So, I guess I'll have more hp now that I painted them red!
Then you need to put a "Type R" sticker on the tail somewhere like them ricer guys do with their car so it will have even MORE hp!!!
08-30-2004, 07:56 AM
Hey Ron, I agree with the tall tail principle, BUT, engine out with a pod. Not likely the safest forced landing design.
I am beginning to see the advantage of the moment arm of a fin and rudder with the full span h/stab on the top of the fin. What say ye all?
Open frame not a problem.
08-30-2004, 08:38 AM
Paul, the tail design has to be such that it fits the rest of the design. The HS must be placed where it will get good airflow, both power-on and power-off, at all airspeeds. That may dictate placement high, low or in between. A relatively short-spanned HS certainly won't be a success on a wide-bodied side-by-side with a blank wall at the back of the pod.
OTOH, pod designers could have a go at better streamlining. Most pods are slick as can be up front where the maximum sales appeal is. Generally, they wall off abruptly or are just open right ahead of the prop. This can actually add drag as compared to an unfaired frame, and it wrecks the flow into both the prop and the tail surfaces.
Furthermore, raising the occupants' feet into a semi-prone position can dramatically reduce the frontal area of a pod. This, in turn, both cuts drag and improves flow to prop and tail.
It's hard to argue with the cancelling of torque roll that comes from the use of either a full-span centered HS or a full-span centered vertical fin. If both of these ideas are abandoned, some other torque-cancelling setup ought to be considered to eliminate low-G torque rollover: something like differential HS incidence or even the revival of Cierva-style mini-wings.
08-30-2004, 09:08 AM
Hi Ken it looks great. How does it fly? How do you like the new Landing gear? Does it change the ground handlin? Take off? Landing? Is torque roll a problem? How does the extra power feel? Can you feel any difference from the reduced drag? You changed so many things, It must be hard to sort out the difference each change made.
You are an Inspiration to us all!! Thank You, Vance
08-30-2004, 09:48 AM
Vance, I still haven't had time to do much evaluating, but to be honest it scares the hell out of me!
I'm not used to power and speed like you are. I've always been a "low and slow" type of guy. My gyro now feels more like a rocket. The engine has a power problem between about 4300 and 4700 rpm. On the take off roll it runs smooth from 2000 to 4300 rpm (about lift off speed) and then it seems to just sit there while I push the throttle forward gaining rpm very slowly, but when it gets to around 4700 rpm the rpm jumps up quickly and the gyro shoots up like a rocket - about 10 Gs (at least it feels that way).
Vance, as an engine expert, what do you think causes this?
08-30-2004, 10:19 AM
Hi Ken, I am not an engine expert. In my limited experance something is upsetting the carburators at a particular rpm. Usualy the sorce is the exhaust resonating back thru the carburator. This can be addresed in many ways such as jetting, intake or exhaust changes. Even something as simple as changing the aircleaner. That is a particularly anoying rpm to have that problem. My contact with the Rotax distributor has always been very informative and I think that would be a good place to start. It apears that you are not using a rotax exhaust but I would think that they would want to resolve the issue anyway. They may be able to save you a lot of experimentation because I expect that you are not the first one to have this challange. They seem to be very nice people and their representitve seems very clever. They also provide a lot of good information in their manuels. Sorry that I can't be more specific. I would love to be there for the experimentation.
It has been my experance that an excess of power can be nicely handled by using the throttle in an inteligent way. Your current flat spot takes away some of that option. I suspect that you will become a power addict when you get it resolved.
I just got back from Bonniville where one friend of mine broke the land speed record for motorcycles at over 336 mph. And another set a record for a 45 inch push rod open bike on a chassis that we built 20 years ago. We also got a model A Ford to over 270 mph. My friends and I would add fuel injection, a blower and run a little nitro so we are not a good sorce for common sense to fix your hesitation. Thank You, Vance
Ken - this problem may have something to do with the torque curve of your engine. At any RPM, the engine has to overcome the torque required by the prop at that RPM. Your Engine torque may be too close to the prop torque between 4300 and 4700 RPM. Reducing prop pitch a little may solve this problem.
Does the 912 have a tuned pipe? If so, it may "come on the pipe" at 4700 RPM.
08-30-2004, 12:21 PM
Vance & Udi,
Thanks for your input.
No, my muffler is not "tuned", just the normal can.
I will talk to the experts and re-check my carb balance. I'll also try the prop pitch change idea - sounds like an easy fix if it works.
I guess I'll have to take off from work this afternoon, as this is too important to be left undone!
08-30-2004, 09:34 PM
the type of carbs used on the 912 Rotax engines are REAL sensitive to the way the airflow is introduced into the carb. I would strongly suggest looking at your intake plenum design and make sure all is well.
On certain installations using the Jabiru engines - which use the same carbs - you would have to use a lot of creative ideas to get the airflow into the carb just right to make the engine run as it should.
08-31-2004, 06:06 AM
Ron: That's interesting. I initially ran my 912S for a short time with no air cleaners. That worked fine, but made me feel guilty. I switched to my present system right after that, and it's worked well ever since.
I have a Rotax dual-carb air cleaner (the type used on Rotax DC 2-strokes) mounted on the back of the mast, with the spigots down. I ran 2" black CAT duct from the carbs to the spigots. There's no plenum chamber as such.
This "remote" setup was necessary because I mounted the engine as far forward as possible. This meant that the Dominator shock assembly was immediately forward of the carbs, leaving no room for separate air cleaners to be clamped right to the carbs. It runs very well, and has picked up a couple hundred RPM as it's broken in.
09-05-2004, 02:29 AM
I'm with you Doug.[but I'm not argu'n with Ron,again]
With the 912 I'v got I'v had 4 different typs of intakes,with and without carb heaters and 3 different exhaust setups,and none made a noticable difference to performance.
I'd be interested to hear wots wrong with Ken's.
09-05-2004, 03:10 AM
hi ken ! (sorry for my Frenslish)
just to say you really did a great work, balanced, not skunk, just enough innovative and if i can see it by the pictures and your website, very well done ... nice.
it seems your design is "actual", lookt at the latest MAGNI prototype
09-05-2004, 07:49 AM
Thanks. Looks like Magni now has a twin tail gyro - similar to mine, but I expect much higher quality. They make beautiful gyros.
09-05-2004, 06:21 PM
David, Argue with Ron Please, dont let him off easy, GEEEZ! Ok Ron guess its just me against you lol. MJ :)
Thanks Ch# 13 for your very Kind Donation to Sunstate. Batten down and be ready for Frances, and Ivan!
01-21-2005, 04:29 PM
Just an update:
I adjusted the prop pitch and the 912S engine now pulls evenly all the way from idle to full rpm.
I changed the pitch on the Sport Rotor blades to increase the rpm - now spins at 305 rpm - flys very smooth with a lot of lift.
The trim spring had to be adjusted to pull very hard so I replaced the turque tube with 5/8" offset rather than 1". Now it only need a small trim spring pull and is much easier to hold the stick forward while taxing on the ground.
The best cruise speed seems to be about 75 mph, but it can go much faster with little effort. I cruise at 55% power - 4300 engine rpm.
I am a very happy pilot!
I added a new page to my website. Click on "Ken's Gyro" below, then "Flying Again #1".
01-21-2005, 04:41 PM
you have replaced yous shock absorbers, no ? do you mind giving their main features please ?
01-22-2005, 04:29 PM
My shocks are Azusa shocks, 700 pound maximum. The website below shows them, however I think there is an error in their description, as the travel distance is 3" (not 2.4" as shown):
01-22-2005, 04:43 PM
Great Ken, thank you.
01-24-2005, 07:00 AM
Other things being equal, increasing RRPM by de-pitching a rotor will decrease the flapping angle for any given airspeed, and so will require less gimbal offset. If the gimbal offset stays the same, you'll have increase the trim spring pressure to counteract the force created by excess offset, just as Ken observed.
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