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HelicopterScale Model RC Helicopters Docs  700 cobra
10-11-2013 06:00 PM  4 years agoPost 41
spiderco

rrVeteran

Henderson, Nevada

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That's too bad, I was really eye balling the Cobra. I have sent them multiple emails in the past with no response. The "Notify me when in stock" button also does not work, I've used that several times with no notification on items I see went in stock.

fly til its dry

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10-13-2013 06:59 PM  4 years agoPost 42
edge_pilot

rrNovice

Lagrange, Ohio United States

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OK, just got done the last hour test flying the Cobra again. This thing shakes like there not tomorrow! No matter what I try it doesn't get any better or any worse for that matter.

My assumption, this thing is a piece of ****!!!!! No matter how pretty the wrapper is, **** is still ****!!!!!!

I think all the vibration is coming from all the slop in the linkage. The ball links are not very good quality and are not tight, or even snug for that matter.

Until I replace all the ends with new high quality ends this thing is back under construction. I sure hope I get it figured out before the armament pods break off!!!!!

This post may upset some but I call it how I see it and I expect a lot more for this kind of money.

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10-14-2013 01:50 AM  4 years agoPost 43
Mojave

rrElite Veteran

Palos Verdes, Ca. USA

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Not to pee in your Wheaties but I saw this kit first hand and saw it fly at Scale masters. I found it to be well engineered and it flew like it was on rails. I am NOT a RCA sponsored pilot and my opinion is mine and mine alone. If you have a vibration issue, my first guess would not be a ball link, it would be a shaft or a rotor head main bore that was incorrectly machined (bore is not concentric). I have seen this issue on more than 1 rotor head over the years. I would remove the rotor head and bolt it to a stock mainshaft and spin it in a drill at high speed. You may find that it has a small wobble. This wobble will equal a lot of vibes at flight head speed. The other thing I would look at is blade weight and CG. Put the blades on a gram scale and check the weights, then put them on a piece of round stock and move them back and forth to find the CG, then mark it. Check the other blade and compare them. Again, this was JMHO and I'm trying to help
Barry

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

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10-14-2013 02:18 AM  4 years agoPost 44
edge_pilot

rrNovice

Lagrange, Ohio United States

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thanks for the help.

As far as the main shaft, I am using the replacement that Aerodyne sent me, if they in fact sent me a new one and not my old one back? They are sending me another from China whenever it gets here.

I will try the blade thing. Once I balanced the blades there weight was dead on with each other. I did not check the CG of each one. I will try that.

Do you know if the one you saw fly was bone stock, right out of the box and nothing was done to it to make it fly better???

Now that I have some time, very little, the blades move almost 2 degrees (1.7 to be exact) because of the slop in the ball joints, would you consider this acceptable??? I don't by any means. This slop was not this bad when brand new, this is why I personally think the vibration got worse since new.

The reason I personally think it mite be this issue causing the vibration is with this much slop the FBL unit try's to compensate and then starts fighting itself and it all leads to what looks like vibration. Just my thought.

I'm not sure about the head, I have spun it and it "looks" good. Not saying it isn't off but the only way to prove that is replace it.

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HelicopterScale Model RC Helicopters Docs  700 cobra
10-14-2013 03:09 AM  4 years ago •• Post 45 ••
Mojave

rrElite Veteran

Palos Verdes, Ca. USA

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First things first: I understand your frustration, but would cool the rhetoric that Cliff is somehow doing something dishonest. I have bought more than one heli from him over the years and he has always stood behind his product and made right on anything that he sells. Nuff said

That slop is a lot more than I would like to see and may be caused by another issue. Vibes do funny things to FBL units, so yes it may be hunting due to vibes. The very FIRST thing I would do is bolt that head to a standard rex600 shaft and spin it. Check all of the boxes and eliminate the things that are unrelated to the issue. Yes, the cobra that I saw was bone stock. As a matter of fact, I got to look at the mechs. The 700 size Cobra and Bell 429 are both Roban helis, not RCA. RCA sells them, but it's not their specific product. RCA makes the bigger 800 size 429. I was impressed with the mechs layout and reliability built into the design. I'm told that they are developing a kit to convert the mechs to clutch drive soon.

I would also look at your head speed and the tightness of the blade grips. This heli comes with the new wide chord Roban scale profile blades and they do not need high head speed to fly. After seeing the cobra fly, I would opt for 1400 rpm HS if I bought one. The blade grips should be snug, not crazy tight. If you eliminate the head machining as a culprit, my next step would be to swap on another set of blades and see if the vibes go away. Sometimes it's the simple things that bite us in the A$$
Barry

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

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10-14-2013 03:20 AM  4 years agoPost 46
edge_pilot

rrNovice

Lagrange, Ohio United States

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I will check the head while it is apart.

My head speed is at 1450 right now.

The geartrain to the mechanics is solid and nice. I have seen better servo setups and tighter linkage.

I have an email into Aerodyne also to see what his ideas are. I realize it's Roban but Aerodyne is the distributor and were I bought it. It's up to them to make it right.

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10-22-2013 08:58 PM  4 years agoPost 47
creamer

rrApprentice

Smithfield, Utah

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Here is my video of the heli that I just made. This thing flies like a dream and the video shows it.

Watch at YouTube

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HelicopterScale Model RC Helicopters Docs  700 cobra
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