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HelicopterScale Model RC Helicopters › RCA UH-1N and Century Bell 47
12-17-2011 07:08 AM  5 years agoPost 1
Jockobadger

rrApprentice

Snoqualmie, Washington USA

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Hello Forum,

I am writing in hopes that I can get some advice from you knowledgable folks. I've already gotten a good bit of "PM" help from Mojave and Doorman, among others, and I sure appreciate it.

Bell 47

I've flown pod/boom for a couple of years now, but have wanted to build a scale heli for a long time. Finally found myself with the time (partial layoff combined with divorce) and the finances (dumb luck) to try building one. I started with the Century Bell 47 kit. I have completed the airframe and have finally gotten the electronics sorted out and wiring done. I'm using a Tango 45-8, Kont. 85hv, 6s (3s2p in boxes on the UC) and HC3SX for stab. with Mikado head. I've included photos. I finally did a test hover and it's great! I have the head gain set on a rotary switch on my TX so I can adjust gain in the air. The test hover allowed me to establish the best gain number and now I can enter that into the Helicommand menu and then activate the auto-leveling feature - something I'm anxious to try. Once I get that done, I'm going to move everything around and build my cockpit, etc. The fuze, tanks and cockpit are painted with SAC Bomber Green. Got graphics from Callie. I have scale blades and did my tests with those.

RCA UH-1N

This is my favorite heli with the Bell a close second. I traded Cliff at RCA for the new Huey with a Chaos mechs kit. It comes with a "short" frames kit that allows all of the mechs to sit inside the doghouse leaving the interior open. The wood was already installed and appears to be nicely done. The fuze has sort of embossed panel lines with a few rivets. In certain light it looks pretty ok, but they are hard to see on the shiny finish. The kit comes with torque tube drive, a 40 deg (or so) gearbox and another short TT that extends up to the tail (see photo) I've pieced it together and it seems to work smoothly. The gearbox is installed via a hatch on the right side of the tail. I also got the Huey "Scale" head with a "dummy flybar." It has built in dihedral of about 3-4 deg or so.

Questions for the RR Experts:

1) I want to use a Neu 1907 (966kv) it's wide, but fits in the frame nicely. I want to use a Kont 55-10-32 and will probably use either a HC3 or a Microbeast for stab. The kit comes with a 12 tooth pinion. I tried doing the math, but what do you guys think? I want lowish headspeed because I intend to putt around the field with this thing. I could up the voltage to 8s or 10s if necessary?

2) This fuselage is 60"+ long and seems big for 600 blades. Also, the blade grips on the head are 14mm rather than the 12 of all my other heads and blades. Is this head intended for a 700 or bigger? There appears to be room to use up to 680 or 700 blades without fouling the TR. What do you think. I have several other heads that I could use.

3) The rotormast that comes with the kit is a bit short for true scale, I think. I've looked at lots of UH-1N photos and it's pretty close, but short. The rotormast is narrower at the base, so it's not a simple of matter of using a longer one, unless you all know of something like that.

4) While the paint scheme is nice, I think it's too shiny. I'm going experiment with ways to tone it down a bit (kit came with nice "Marines, etc. decals.) I'm also going to paint the top of the nose a nice flat black like some I've seen on airlines.net. The magnets that hold the doors closed and the doghouse on a bit lame. I'm going to install better ones.

All in all, I'm not that happy with the way it's going together. I'm perfectly happy to do the work to "make it work," but the quality of the mechs seems a bit iffy. I'm beefing it up and smoothing things out as I go along, but I've seen much better. Oh well, I may get it built, fly it this spring, and then strip it down completely and really add the scale bits. Btw, I have lights, cable cutters, antennas, etc., that I'm going to add - all stuff of my own. I DID get the cockpit kit with it and I have to say that it's pretty nice. I'll take more photos and post them.

Sorry about the crappy quality of the photos. I left my good camera at our Boy Scout Troop meeting - used a point/shoot. Next ones will be better.

Any other suggestions, hints, etc., you could give me would be most appreciated.

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12-17-2011 07:33 AM  5 years agoPost 2
Jockobadger

rrApprentice

Snoqualmie, Washington USA

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One more question!

Sorry Gents,

Something else I've been wondering: The so-called "dummy flybar" on the head (I've looked at the photos carefully and it's a bit to big to be truly scale) has some fairly weighty brass ovals on it and it is free to rock back and forth on it's axis. What is that likely to do to the head/rotordisk/stability of this heli? It is well balanced - goes to level if I rock it. It's also adjustable. Any ideas/thoughts/previous exp? I put the head on my spin balance, sans flybar, and it was beautifully balanced from the factory. Also, the instructions indicate that one should fly the bird and get it dialed in without the flybar on it and then install it later. Will this cause problems with my stability system? Any input is appreciated. Thanks again. Badger

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12-17-2011 09:01 PM  5 years agoPost 3
Mojave

rrElite Veteran

Palos Verdes, Ca. USA

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IMHO, I think the main mast height is fine for this bird. I also like the new style RCA frame set up that puts the mechs in the doghouse area. It makes for a more scale look. I also like the TQ tube direct tail drive, much easier to set up.

At 58" long that fuse is 700 size. My 63" long huey is 800 size. Does that head have a sleeve for the mainshaft, so that it will fit a 10mm mainshaft, or is it just bored to 10mm? The 14mm grips can be used with 700-800mm blades, or 600mm blades by using blade washers in the grip, depending on the bolt size 4mm or 5mm. You can use tubular spacers in the blade root if needed.

The biggest issue with the teetering head is TR and boom clearance. Put the 700mm blades on it and see if they clear the blade circle and don't teeter down far enough to damage the boom.

As for the motor KV, I think it will work with your gear ratio. 800KV 6S on a 170 tooth main with 15 tooth pinion will net you 1410 RPM head speed.

800KV 6S 14 tooth pinion = 1316 RPM headspeed.

700KV 6S 14 tooth = 1152 RPM
700KV 6S 15 tooth = 1234 RPM

I'm not a big fan of running less than 14 tooth pinion on a rex600. The maingear gets fragile because of the decreased tooth count in contact with the main gear.

Flybar: Do what the mfr sais and fly/tune the heli with it off, then put it on after you have it dialed in. It is solidly mounted (not articulated) so it should not negatively effect the flying dynamics of the heli.
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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12-18-2011 02:40 AM  5 years agoPost 4
Jockobadger

rrApprentice

Snoqualmie, Washington USA

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Hi Mojave,

Thanks for your kindly reply. I appreciated your comments on the scale head. However, I wanted to make sure that we're talking apples and apples. The dummy flybar is free to move on it's axis e.g. the brass weights can tilt up and down approximately 25 deg above and below the rotor disk. I have it balanced now so that when stationary, it sits horizontal "above" the rotor disk. I am curious to know what might be the effect of it as the rotor disk tilts in aileron or elevator. It isn't connected to the blades or grips in any way, so it can't have a direct affect, but the gyro effect??? What about that? Perhaps nothing?

Also, what effect will the blade dihedral have? I know that certain full-size helis, including the Huey's, have dihedral built it.

Thanks much. JH

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12-18-2011 03:21 AM  5 years agoPost 5
Mojave

rrElite Veteran

Palos Verdes, Ca. USA

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Hi Bud, when I first read the review on this head it stated that the flybar was designed to be tightened down, so as not to move during flight. maybe this design has changed since it was first introduced. As for the dyhedral (coning angle) of the head: This feature makes the heli much more stable in a hover and has no detrimental effect on forward flight.
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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12-18-2011 03:58 AM  5 years agoPost 6
Jockobadger

rrApprentice

Snoqualmie, Washington USA

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Hi Barry,

Thanks for the info and clarification! The flybar could certainly be tightened down but I assumed it was supposed to be allowed to move because it has two bearings on each side. Seems like it was designed to be allowed to move, but since you read that, and certainly know more about all this than I do, that settles it. Where did you read the review? I'd like to check it out. Great to hear that the coning helps in hover. Thanks jh

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12-18-2011 06:09 AM  5 years agoPost 7
Mojave

rrElite Veteran

Palos Verdes, Ca. USA

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I'm still looking for the info on the head. I may be mistaken regarding the flybar. I know that the vario flybar is tightened, which may be what I'm thinking of. But either way, the flybar is not linked to the pitch control system, so it's just along for the ride. I can't see it being a negative influence on the helis handling.
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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