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Author Topic: Hiller UH-4 Commuter  (Read 12355 times)
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Ray_K
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« Reply #150 on: June 08, 2016, 07:00:54 PM »

6-8-2016

Sorry Roman, I gave you the wrong weight of my Hiller, with pilot it weighed in at 38 grams so you are right on the money, mine flew fine at that weight and would fly heavier.

Cheers, Ray K.  Wink
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rgroener
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« Reply #151 on: June 09, 2016, 04:50:31 AM »

Ray, I nearly got a heart attack when I checked the weight after your 28g info!!!
Now I can sleep again quietly.... Grin Thanks for clarification.

I did the pedals yesterday evening and prepared to sand the Cockpit instruments.
The tiny bits take quite some time... but I can see the light at the end of the tunnel Smiley

Roman
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Ray_K
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« Reply #152 on: June 10, 2016, 09:27:01 PM »

6-10-2016

Hello Roman,

I am getting goose bumps just thinking about you nearing completion, I ca'nt wait to hear about flight attempts!  Grin
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rgroener
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« Reply #153 on: June 13, 2016, 08:57:48 AM »

Ray, I realy hope that I can make it fly at least 30 secs.....
This Weekend I had some time for building. But I was to stupid to prepare it. When I wanted to start, I found out, that I had no white colour for making the Cockpit instruments...
I have to buy some... I also might buy a new double sided adhesive tape. I plan to attach the canopy with it. For me, it worked better than using glue.
How did you glue the canopy to the fuselage? Any Special gue?

Roman
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USch
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« Reply #154 on: June 13, 2016, 10:10:29 AM »

Roman, did you find a magic tape that holds down the canopy forever? My experience about double sided tapes is that it holds the canopy for 1-2 or 3 month and then starts to break loose. There is always some tension in the plastic which tends to separate the canopy. I normally use canopy glue 560 from Pacer. PM me if you cannot find it. End of week I will meet a Swiss modeller who could bring it to Z├╝rich.

Urs
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Ray_K
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« Reply #155 on: June 13, 2016, 07:29:40 PM »

6-13-2016

Hello Roman,

I just used canopy glue 560, that worked the best for me.

Cheers, Ray K.
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rgroener
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« Reply #156 on: June 14, 2016, 02:01:35 AM »

Urs, thanks for your offer, but I think it is not necessary. I just checked it, I could buy canopy glue in switzerland. I just never used it.
Double sided adhesive tape worked fine for me. I have several planes still in use with no indication of braking loose. Also the canopy of the Piper Vagabond is attached with the same method. I would say, ist now 2 years old, and I cant see a Problem with the adhesive tape.

I plan to go to a Hobby store this evening. If they have the 560 glue, I will give it a try. If not, I still could order it from a store in my area.


Thanks for your help Roman
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rgroener
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« Reply #157 on: June 22, 2016, 12:22:53 PM »

I bought the suggested glue, but I did not use it Huh Roll Eyes
I had to fixate the canopy somehow to the fuselage and I did it with tissue. Gluestick and the canopy material work quite well.
But I plan to use it on one of my next builds. This time, there was just an other solution handier.

Picture of the glued canopy will follow as soon as I finished it.
But to post anything, I add a picture of the cockpit interior of my Hiller. I am happy with it so far.
It is not hard to see that it is made manually, but for me this is no problem so far...

By the way, Ray's seats look more comfortable Grin I like the cusion.

Roman
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Sky9pilot
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« Reply #158 on: June 22, 2016, 02:48:51 PM »

Roman it looks great!  Really looking forward to your progress.
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Ray_K
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« Reply #159 on: June 23, 2016, 05:49:33 PM »

6-23-2016

Hello Roman,

Your seats look great, I used foam for my seats. I hate to be the bearer of bad news but I noticed in your pictures that your seat location is way to far forward, for reference look at the pictures of my Commuter. Your pilot would have his knees way bent up to his chest. Just an observation.  Wink

Cheers, Ray K.
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rgroener
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« Reply #160 on: July 14, 2016, 01:27:47 AM »

Ray, indeed bad news... Sad
I already had the canopy glued to the fuselage. To readjust the cockpit interior, I had to tear the whole thing away...
Finally, I have done it and I am ready to glue the canopy on again.
This time I wont change anything, even someone finds anything Roll Eyes

By the way, the pilot had to change his position to the right side since there wouldn't have been enough space for the collective lever in the old configuration. I hope he dont mind...

Roman
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Ray_K
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« Reply #161 on: July 14, 2016, 07:37:33 PM »

7-14-2016

Hello Roman,

Looks way better now, my pilot sits in the right hand seat too!

Cheers, Ray K. Wink
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rgroener
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« Reply #162 on: August 01, 2016, 05:22:46 AM »

Finally the Hiller is finished and awaiting its first flight.
I always tried the motor with only one loop of 3/16" rubber and was disappointed that it had not enough power...
For flying it is thought to use a double loop of 3/16" rubber. Reading the instruction helps a lot Roll Eyes

Now I am waiting for a calm day to let this beast fly.
I try to take some pictures.

Roman
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dputt7
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« Reply #163 on: August 01, 2016, 06:28:02 AM »

Really nice Roman, well up to your normal standard, now can you impress us with some of your stunning inflight shots!  Best of luck.
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Don McLellan
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« Reply #164 on: August 01, 2016, 01:44:01 PM »

Beautiful Roman!  Looking forward to hearing how it flies.
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USch
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« Reply #165 on: August 01, 2016, 04:17:18 PM »

Bello, bello, bello!!!
I am very curious to read and see how it fly's.

Urs

(Saugut hesch das gmacht)
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rgroener
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« Reply #166 on: August 02, 2016, 01:37:17 AM »

Thanks Don and Urs Grin

I thought there is no need to delay the first flight and headed to the field since there was not to much wind yesterday.
I only managed two flights, now I have some minor repairs on the schedule.

Here is flight Nr.1 http://vid340.photobucket.com/albums/o351/rgroener/Hiller_1.mp4

What do you think? My thought is to remove some weight from the back... Any other ideas?
At least the first few seconds looked like flying Grin

More to come...  Not sure if the pilot dares again to fly this beast Roll Eyes

Roman
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Prosper
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« Reply #167 on: August 02, 2016, 05:38:03 AM »

Hullo Roman, I've been watching yours and Don's lovely helicopters coming together with great interest. The following ideas are based on my own observations of a contra unit I made a while back for a fixed-wing aeroplane model. I started skimming through your Hiller thread to see the posts relating to the contra mechanism but started floundering around with paddles and teetering rotors - it's a long thread! So, your contra system may have some design feature that makes it categorically different from mine, but assuming it's the same, I have some ideas about the flight, which I watched in slow motion several times as well as real speed. 

Of course I wanted to try my contra unit before having built the model (Cheesy) so I tried it over some grass. The flights were very like yours, except without the lower CG that the Hiller body provides. Within a second the whole assemblage would start toppling about its CG, so the vertical thrust was reducing rapidly and sideways thrust increasing rapidly, until inevitably the unit dived into the ground. I see the same tendency in your video except that the low CG is able to keep the model from toppling completely. I was 'flying' my unit in a breeze. I think the slightest whisper of a breeze is enough to destabilise the system and commence the toppling. A hand-launch in which the contra-unit's thrustline wasn't exactly vertical would start the same gyrating motion too.

I also see that the lower rotor isn't turning nearly so fast as the upper. Now, this could be due to video compression software or some other camera artefact, but if it's a true picture, this suggests that there's more friction in the bearings between the torque tube and the Hiller body than there is in the bearing between the torque tube and the top rotor. I'm guessing it's this friction that's making the body rotate. The aerodynamic drag of the lower rotor could possibly be higher than that of the top rotor, causing the lower rotor to spin more slowly, but that shouldn't act on the Hiller body. If the RPM mismatch is to do with friction, then the poor rubber motor is having to turn the whole body as well as the rotors - a big waste of energy!

I would first establish where the CG is, both vertically and horizontally. I would try static runs to see if I could judge the friction in the bearings. I wonder if you could wind the unit up and hold the top rotor, then release the rest and watch the lower rotor spin. If the body starts spinning too you could touch it with a fingertip to judge the friction. I would try launching from level ground in zero wind.

Just to give some context, my torque tube is ~310mm long; the prop disc diameter ~190mm (7 1/2") the rubber a loop of 3/16" about 20" long. The whole unit with this rubber weighs 21.5g. The CG is marked with a pink dot. Note the very coarse (high) pitch; I figured the rear prop should have a coarser pitch than the front. On a static run you'd imagine that both props would be completely stalled, but with approx 60% of full turns the thing could climb vertically for a few seconds. However, the big surprise was that this thrust in flight wasn't enough for the model, despite a modest wing-loading. I had to reduce the blade pitch, and i think it needs thicker rubber too. I guess your Hiller rotor pitch must have been optimised by Ray K at the design and R&D stage, but perhaps the loss of vertical lift component due to the model gyrating means it can't keep aloft as well as it should.

I want to try a 'copter sometime so following closely!

Stephen.
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dputt7
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« Reply #168 on: August 02, 2016, 06:20:16 AM »

Reading Stephens well thought out reply reminded me that I too had built a contra rotating mechanism for a fixed wing model. I built a jig to test the gearbox and used, I think, two 8" 3 blade commercial props, I found I could actually fly the test rig in my lounge room, with the appropriate number of turns it would climb nearly to the roof then hover before finally descending to the floor.   There was no wobble or pitching of any kind, I put this down to the accuracy of the  propellers so my suggestion is that maybe your problem could be caused by a discrepancy in the pitch or a slight difference in the rotors, not very scientific I know but hope this helps. I couldn't find the original photo of my test rig but you can see it here  http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=4256.msg37879#msg37879

regards Dave
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rgroener
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« Reply #169 on: August 02, 2016, 09:46:49 AM »

Steven and Dave, thaks for your input.

Quote
I started skimming through your Hiller thread to see the posts relating to the contra mechanism but started floundering around with paddles and teetering rotors...
I am still not sure if paddles are the best thing for stability. I want to try weight at the end of the fly bar instead of paddles. As I understand, paddles instead of weight is there to destabilise the rotorhead and thus make it maneuverable. But I think we want to have it stable... So why paddles and no weight... Anyway. I did go on as suggested in the plan. And Ray wrote that his version was flying with it.
It sometimes has still problems to run stable (top rotor) in the vid. You see me stopping the top rotor since the blades where wobbling. The second run was smooth, therefore I let it fly.


Quote
...I was 'flying' my unit in a breeze. I think the slightest whisper of a breeze is enough to destabilise the system and commence the toppling...
There was also some wind during my tests. Not that much, but is was definitely not calm.

Quote
I also see that the lower rotor isn't turning nearly so fast as the upper....
Your are right. I know this and thought about it myself. But I think friction is not the main reason for the lower speed of the lower rotor. The blades of the lower rotor have the higher pitch. I only noticed this fact when it was to late... Roll Eyes But as I see it, I dont think that this is a big problem. At least, I did not notice a significant turn tendency of the fuselage.
To me, it looks like it is somehow stabe until it starts to fly backwards. Maybe due to the drop-shape of the fuselage it starts to turn abruptly. If the pointed end of the fuselag hits the airflow, it will definitely turn to one or the other side. Then at the end it seems to be a bit more stabilised again...

Quote
I would first establish where the CG is, both vertically and horizontally...
I will check that, but have first to repair it. I will also look for the vertical CG. Did not check it yet. I dont think that I can change there a lot, but it will be interesting to know where it is. (ok, I can add weight at the bottom of the fuselage...)


Dave, I have to read your thread in a quiet minute. Interesting to hear what you found out with your configuration.

Roman

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tom arnold
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« Reply #170 on: August 02, 2016, 09:49:40 AM »

I have experimented with autogyros, not helicopters, but I found that moving the CG slightly forward of the rotor shaft sometimes helps. What it seems to do is take away the machine's ability to move in any direction it wants and forces it to move in just one. You might wind up with a 45 degree climbing flight path instead of a pure hover but full-size helicopters spend very little time hovering anyway. This may not work at all but it is something to try if your bag of tricks runs dry.
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« Reply #171 on: August 02, 2016, 01:06:34 PM »

Roman...great first flight.  Looked to me like she was flying till a bit of wind upset the stability.  Your progress is amazing.  Hope the repairs are not too serious.
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rgroener
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« Reply #172 on: August 03, 2016, 01:23:54 AM »

Stephen, for what plane did you build your contra rotating mechanism?

Thanks Tom, I will try it.

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...great first flight
well... I would not cal it a flight. It was more a somehow stable moment before falling down Roll Eyes But thanks anyway. I dont give up yet. The glue from repair has dried, I am ready and waiting for calm weather (and some freetime) to try it again.

Roman
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Don McLellan
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« Reply #173 on: August 03, 2016, 01:49:49 AM »

Hi Roman,

I think a great first attempt.  And it did look like something disrupted quite a stable launch.

D
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« Reply #174 on: August 03, 2016, 11:02:37 AM »

 
Hello Roman, a friend who is corporate helicopter pilot and I had great fun last night going over the video again, frame by frame, and we think that you are close to greatness. The model seems to take off OK, then it gets a bit upset that tilts the rotor plane off the horizontal to almost the vertical. This drops the lift and the model slides down in a spiral but it appears to attempt to right itself. It does for a second but the swinging, spiraling fuselage tilts the axis of the rotor shaft off the horizontal and the whole process starts over again 2 times before it hits the grass. The peanut gallery half way across the world concluded that you may never have a true hovering helicopter in any breeze (except for a few seconds) as even full size ones will fall off after an extremely short time if hands are taken off the controls. Modern full size ones have stability augmentation systems that are on full time so hovering today is much easier but you can't really compare them to your efforts. My friend also commented that an off-center forward CG (with the stab aug system off) in his helo creates a "pull" forward and he has to work to override it.
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