Kermit continuing flight log

gyrodeputy

Newbie
Joined
Jun 6, 2007
Messages
973
Location
SD
Total Flight Time
200 and growing
Upgrade

Upgrade

We have had some nasty winds and thunderstorms today including hail. The forecast is the same for the rest of the week.

As a result, Tomorrow I am going to take Kermit to the exhaust shop and we are going to change the exhaust.

I have a new 4 into 1 collector and new pipe that are longer. I will post pictures of before and after tomorrow.

Wish me luck!!!
 

gyrodeputy

Newbie
Joined
Jun 6, 2007
Messages
973
Location
SD
Total Flight Time
200 and growing
Prerotator Issues

Prerotator Issues

For the past couple of weeks I have been having a series of problems with the hydraulic prerotator.

I would go for a flight and during post flight inspection I would find the pump either very tight or completely locked up.

It reminded me of helicopter maintenance. 1 hour of flying and 5 hours of maintenance.

To say it has been frustrating is an understatement.:mad::mad::mad::mad::mad::mad:

Twice I have completely drained and flushed the system. Twice I have disassembled, cleaned and reassembled the pump AND motor. I spun everything up and same result. Each time getting more black particulates out of the system.

The particulates are fine dust from when the hydraulic hoses were cut and crimped.

Talking to a hydraulic expert a couple days ago, he told me to run the pump backwards by hand and keep filling it up with fluid and cycle no less than a 1/2 gallon through the system.

Additionally, he provided me a part number for a very small and cost effective ($39.00) in line filter.

Today I put everything back together and added the inline filter.

The preliminary results are in... I spun up the rotors on a ground test and reached 150 RRPM within seconds and at a much lower engine speed than in the past. :whoo::whoo::whoo:

I shut everything down and the pump spins like magic. I am CAUTIOUSLY OPTIMISTIC that the filter and extensive flushing has solved the problem.

Flight tomorrow weather permitting...thunderstorms in the forecast.

I will update you all with a progress report as soon as I have one.
 

All_In

Gold Supporter
Joined
Apr 21, 2008
Messages
14,771
Location
San Diego, CA. USA
Aircraft
Piper Archer, Aviomania G1sb
Total Flight Time
Not sure over 10,000+ logged FW, 260+ ultralights, sailplane, hang-gliders
I hope you have found the problem Heath!

who's prerotator are you using?
 

gyrodeputy

Newbie
Joined
Jun 6, 2007
Messages
973
Location
SD
Total Flight Time
200 and growing
AWESOME FLIGHT and PREROTATOR IS FIXED!!!

AWESOME FLIGHT and PREROTATOR IS FIXED!!!

So today I finally had favorable winds for a flight.

Wind variable at 4. Density altitude 8,100. TIME TO FLY!

After a through preflight I had to back taxi the 4500 feet to the far end of runway 8. Although reported as variable by AWOS the sock favored runway 8.

I lined up on the centerline. Engaged the prerotator and in seconds 150 RRPM. Engine instruments in the green, stick back, release brakes and prerotator. Smooth roll out and blades quickly advancing.

Nose light at 280ish RRPM (sorry not focusing on the instruments just a quick glance. Another perriferal glance and the windsock is straight at me in line with the runway. Off the ground smoothly in about 800 feet.

Good climb out at 300-400 FPM 7800 RPM and indicated airspeed of 55 KTS.

Left turn from the pattern and north bound I went.

My current limitations are no flights over densly populated areas so I stayed west of Custer City, flew around my friends shop (with permission) at 750 AGL. We waved at each other and then back north bound. IFR (i follow roads) over highway 16 past The Crazy Horse monument and to Rushmore Helicopter Adventures where my beautiful wife Laurie works. A couple of traffic anouncment on the Mount Rushmore unicom (that is they frequency they use for the helicopter operations) and after 1 helo departed the area a 500 foot pass to wave at Laurie and some of the other helo pilots.

I stayed up another 60 minutes for a total of 1.7 hours. The landing was uneventful with almost no roll. I let the blades spin down naturally to under 75 then light rotor brake. Taxi off the runway and to the hanger.

The best part of today's flight was when I did my post flight inspection the prerotator is free and spinning great. I think the mulitple flushings and pump/motor cleanings and the inline filter solved the problems.

Cruise speed was 65 to 70 KTS (75% throttle about 6500 RPM) with a matching ground speed. The winds really cooperated for some more fine tuning tests.

Fuel burn rate I believe to be in the 2.4-2.6 GPH.

AWESOME DAY!!! :party::party::party::party:
 

Smack

Re-member?
Joined
Nov 3, 2013
Messages
585
Location
Georgetown
Aircraft
Kitfox IV / F1 Rocket / Magni M-16 / Beech 18
Total Flight Time
500+
Heath, it might be a good idea to replace that hydraulic filter after a few hours of use just to be sure you're scrubbing all the loose bits out.
Brian
 

All_In

Gold Supporter
Joined
Apr 21, 2008
Messages
14,771
Location
San Diego, CA. USA
Aircraft
Piper Archer, Aviomania G1sb
Total Flight Time
Not sure over 10,000+ logged FW, 260+ ultralights, sailplane, hang-gliders
Great new Heath!
 

gyrodeputy

Newbie
Joined
Jun 6, 2007
Messages
973
Location
SD
Total Flight Time
200 and growing
Smack aka Brian,

It is the plan. I am going to do that after about 5 more prerotations. It is actually designed to be removed, cleaned and reinserted.
 

gyrodeputy

Newbie
Joined
Jun 6, 2007
Messages
973
Location
SD
Total Flight Time
200 and growing
Kermit Update

Kermit Update

I have been swamped with work and projects but wanted to give a brief update on the progress with Kermit.

I now have about 15 hours on him. I started to notice some paint rubbing on one of the control rods near the coolant tank. The investigation concluded that when landing the rod would make light contact with the coolant tank.

I worked with Nicolas and decided the best solution was to put in a walking beam control assembly to correct the clearance issues. 4 new heim rod ends, some lathing and new rods in place. That is all done.

(Just to clarify, this was not a design flaw from the original kit, but rather because I am using a non-standard engine and the clearances are much different.)

During this modification, I also was able to make some minor adjustment to the stick limit points. Before, when full aft it would bury into my (fat) belly. Now it is more comfortable and does not hit the panel. It is smoother and has full range of motion.

I am also finishing up an electric pitch trim assembly. This will make fine trim adjustments much easier and more convient. This also involved changing the stick grip from a single push to talk button to a grip from a Huey that I picked up on Ebay. It will have pitch trim, PTT, radio flip flop and Ident for the transponder.

During the sturgis motorcycle rally the artist (Sue Hopper) was here who did the original artwork on Kermit and the American Flag. She added some more personal touches for me this year in exchange for staying at our home during the rally. This includes a picture of our dog Bella that we had to put down this year, my EOD (bomb tech) badge, a small gatlin gun on the nose and a thin blue line police flag.

I am hoping that next week I can get the exhaust changed from very short primary tubes and a long secondary to the opposite so that I can change my power curve to a more managable pattern.

I will post some pictures and updates...in about 2 weeks.

I look foward to your comments.
 

j bird

Gold Supporter
Joined
Nov 11, 2005
Messages
1,711
Location
Cave Junction,OR.
Aircraft
Dominator/Airworthiness Certificate 9/06/12
Total Flight Time
26.5 duel,RAF,Sparrow-Hawk,Cavalon,Calidus.
"A thing of beauty"
 

Kevin_Richey

Yamaha gyro...Oregon, USA
Joined
Nov 16, 2003
Messages
2,187
Location
Oregon, USA
Aircraft
Sport Copter gyroplane
Total Flight Time
300+ gyroplane, 11 airplane, 1.5 PPC, AND... a ZILLION hours of flying in my dreams!
Is the thin, blue line in reference to the police standing between the two-legged cockroaches and the rest of normal society?

Where did you have Kermit in the photos? It looked like some sort of street fair? It doesn't look like the Custer airport...

RE: your exhaust setup. Are you having some sort of rpm surge in certain ranges, similar to some older two-stroke engines?
 

gyrodeputy

Newbie
Joined
Jun 6, 2007
Messages
973
Location
SD
Total Flight Time
200 and growing
Details

Details

Is the thin, blue line in reference to the police standing between the two-legged cockroaches and the rest of normal society?

Where did you have Kermit in the photos? It looked like some sort of street fair? It doesn't look like the Custer airport...

RE: your exhaust setup. Are you having some sort of rpm surge in certain ranges, similar to some older two-stroke engines?
Kevin,
During the Sturgis Motorcycle rally there is a wonderful painter that comes here and paints bikes, cars, jackets, helmets etc. She is the one who did the original kermit, badge and flag. It is in downtown Custer.

Regarding the power.

Because my primary exhaust tubes are so short into the collector I do not have any midrange power. I basically have idle, fast idle and full or near full throttle. This will be corrected by making the primary tubes longer before going into the collector. I am being told it is about dwell time before being constricted into the smaller area. Basically because the tubes now are so short there is no time for the exhaust to get out of the engine before it is compressed and as a result you have to power through to full power to force the exhaust out and into the secondary. I am trying to get some mid range power for cruising and routine flying.
 

All_In

Gold Supporter
Joined
Apr 21, 2008
Messages
14,771
Location
San Diego, CA. USA
Aircraft
Piper Archer, Aviomania G1sb
Total Flight Time
Not sure over 10,000+ logged FW, 260+ ultralights, sailplane, hang-gliders
Sweet artwork; great job Heath!
 

NoWingsAttached

Unobtainium Member
Joined
May 21, 2006
Messages
4,788
Location
Columbia, SC
Aircraft
Air Command Tandem w/ Arrow 100hp; GyroBee w/ Hirth 65hp; Air Command Tandem w/ Yamaha 150hp
Total Flight Time
>350
Excellent work, great to see the Kermit is so GREAT! I see a question earlier about the life of the Rotax C gearbox, and your response about HP.

In discussing what a particular type gearbox limits are, although it may seem convenient to conversationally express what has been found in the field on motor "xyz", putting out a rumored n HP, it is not used in the actual calculations for bearing life.

Although the bearings may be able to run under the total dynamic loads listed in the mfr spec sheets, and stand up to static loads of a lesser factor, speed plays an enormous factor in how long they will stand up to the load placed on them.

The life of the gearbox is determined by three things:
  1. Rotating inertial mass, determined by diameter and weight of the prop blades, that the prop shaft can handle cantilevered out distance x from the main bearing
  2. The gears themselves
  3. Bearings, top and bottom
There is a worksheet posted here

https://www.rotaryforum.com/filedata...hotoid=1127238

which provides the details required to arrive at bearing life in the gearbox under IDEAL conditions (shown side-by-side with the larger gearboxes we normally use on YG4 conversions). Note that in the spreadsheet horsepower doesn't appear. That is because HP is not a force, but rather the amount of work done over a period of time. The force is torque, and in the American standard engineering numbers that is lbs of force (lbf) divided by distance from the axis about which the force is being applied, in feet or inches. Engine torque is measured in "foot pounds", ft.lb. - not to be confused with lbf which is force applied regardless of distance.

In our case, the radius of the drive gear tooth face in the PSRU is 1", and the YG4 puts out an 94 ft lb torque = 1128 in lb @ 12 inches, running 7000 SRPM and 8330 ERPM. The resultant lbf applied to gear tooth, and therefore bearings, at 1 inches R, is 1080 in lb x 12 in/1 in = 13,536 in. lb. Bearing loads are measured in the universal standard kilo Newtons, kN. and the conversion yields 5.52 kN

Assuming running temps < 150°C and suitable, clean lubricant (anything from red tranny oil up to 85/140W gear oil) under ideal conditions the Rotax C can be expected to last a little over 1000 hrs with a prop up to 74 inches diameter weighing a bit over 10 bs total, with hub.

The model allows for the regular 6% increase of forces seen at the bearing due to contact angle of the gear teeth, (not to be confused with helical gear angle) but only allows an extremely conservative 4% wear factor for vibration/harmonics. In other words, it does not accurately account for prop harmonics and gear vibrations, let alone constructive wave formation of the two which will have serious impact on bearing life.

In many gearbox bearing life models it can be found that, due to the wear factor determined by real-time, accurate measurements of harmonics and constructive wave formation, a reduction in bearing life of > 50% is not uncommon.

With bearings expected to last 1000 hrs under ideal conditions, it is a crap shoot whether or not any particular installation will last even 500 hours as of this writing, since I haven't yet written the software to interpret the wave output on my PC's MIDI data screen for the transducer I have had since the 1980's when I was in a bar band and needed to amplify my upright piano for the stage.



As for KERMIT:

With the very low power settings and ERPM you fly currently in the light single-place gyro "Kermit", it is easy to imagine the gearbox lasting past recommended 1000 hr TBO to change the bearings.

--------------------------------------

I don't recall if Kermit uses an RK400 clutch or not. If you bought an RK400, you need to remove and inspect it every 75 hours. You should already know this, one would hope, since it is discussed in the mfr installation instructions. (We know Teal Jenkins never told you about this mfr requirement because I had to tell him about it myself, just last month, publicly in Avidfoxfliers - even though he has been selling them as part of his RX1 conversion kit since 2014.)

If instead you are using a Rotax rubber donut (Hardy disk), at low power settings you might be OK, but as warning: we just found out last spring that on a YG4 140hp at 75-80% the donut cracked through and through after just 12 hours. (Teal Jenkins learned of this the same day I did. We waited several days for him to come forth and post the news, but he kept it quiet instead. I finally had to be the one to do it. To this day he has not so much as posted a response nor re-post of the info in any forum on which he is routinely active.)

When using a Rotax C box, the drive gear bearing shim must be put in the correct position in order to balance the axial shaft loading between both bearings. Since you must tear down the gearbox to inspect the RK400 or the rubber donut every 75 hours, this becomes even more important to pay attention to, since incorrect shim reassembly at any one of those times will result in bearing failure very quickly following thereafter. (Teal Jenkins hid this failure for many months, intentionally neglecting to inform the public and his customers about it. It was not until after I came forward, and first made the announcement, that Jenkins found himself forced to finally admit and discuss it publicly, offering any plausible explanation and providing any useful public information on how to hopefully avoid such an imminent, catastrophic gearbox failure.)

(Do not look to Teal Jenkins for any answers or any attempt at determining the expected life of the Rotax C on a Yamaha conversion. He either won't or cannot do it. Jenkins has had fully at least a year by now to do his homework and figure things out after learning about the Rotax C failure - to determine bearing life, etc - yet he has done nothing. Instead he is in the middle of designing, ground-up, a gearbox for the YG4i 150 HP which he now claims will be good to 200+ HP. The only way to make such a claim is if one figured out the processes involved and did the math to determine bearing loading and expected life for a minimum 1000 hrs TBO. His claim would seem to indicate that he knows how to arrive at these conclusions, do the bearing life calculations on his own. Why, then, the man has not published any information regarding expected life for his existing kit with the Rotax C is anyone's guess. Either he is making unsubstantiated claims about the design he is now involved in, or he has neglected to figure out what his existing kit is worth in terms of safety and duration.)

(I will take another look at the prop shaft bearings and will post in the above mentioned thread if they are significantly lower life than the drive shaft bearings or not. I challenge Teal Jenkins to figure it out for you instead, but seriously doubt he has a clue - or if he does, that he is willing to be forthcoming with any information, given his checkered past on such delicate matters in every single situation we have learned about regarding his kit's equipment to date.)
 
Last edited:
Top