SR120 tail horrible wag?

**Delarado** · 22-02-2012 08:18 PM

Anyone else had this?
IVe just put a microheli frame on my brushless MCPX (HP05) and a 120SR tail with it.

Its horrible.

Wags constantly, when you are turning it does not turn; It wags around. Youll have no tail movement, then a wag, then a stop, then a wag.

I dont know what could have caused it?

Zeeflyboy, did you have any issues?

**n00by** · 23-02-2012 01:45 AM

hmmm dodgy tail motor connection, is it wired directly to the 3in1?

or maybe some sort of vibe.

**Delarado** · 23-02-2012 02:02 AM

It turned out to be the size of the tail rotor I think. I trimmed it, but i dont think I trimmed it enough.

In the end I took about 8mm off each blade in 2mm increments and it slowed down... now seems to have stopped with the final trim.

Turning performance is still a little strange, but I think it just needs some fine tuning (A bit more trimming maybe)

**Zeeflyboy** · 23-02-2012 09:58 AM

I trimmed it a bit, I had some mild wagging with the full length blade.

Are you using a 3mm boom? I found 2mm way to flexy with the weight of and sr120 motor on the back. How much you trim from the blade will all depend on how long you made the boom.

Apparently the plantraco prop is the key to a perfect tail on the sr120 motor, but I've been happy with my trimmed sr120 one for now and it looks nicer lol.

**Delarado** · 23-02-2012 11:11 AM

Yes I have the 3mm boom. I didnt trim it at all? I just stuck the standard SR120 boom into my frame, should I have cut it down?

One thing I really dont like about the microheli frame is the delrin tail mount doesnt include the anti-rotation flat thats present on the standard boom. How do you stop the boom rotating? Ive done the screw up fairly tight but I dont want to do it too tight in case it just strips!

Does yours spin flat as well when you piro?

**n00by** · 23-02-2012 11:24 AM

good to hear u got it sorted

got to agree the stock 2mm boom is to flexible, i drill out and reinforce the stock frame to fit 2.5mm it makes a very big difference, no need for supports and no flexing at the frame either the whole frame moves if u get wihat i mean lol

a bit of tape may help stop it from slipping, i'd would like to try a plantraco prop may just end up ordering it from someone in the US if microcontrol don't get theri finger out!

**Zeeflyboy** · 23-02-2012 12:26 PM

Yeah you need to trim it down a bit - that's why you had so much bounce... By leaving it full length you gave the tail too much mechanical gain.

It also means its impossible to get CG to balance, which will explain your dodgy piros.

The mcpx does unfortunately seem to have some funky mixing going in that means piros are never dead flat, but if you get your CG spot on it will go a long way to improving them.

The tail mount is designed to just clamp it. I haven't had any trouble with it slipping around at all I must say... I did have a problem with the screws that hold the mount to the frame stripping out in a crash though - solved with bigger screws. I imagine the fact that you didnt trim the boom means you get worse clamping too though, since the mount was designed to clamp a round boom and you are missing a chunk due to the flat section. Microheli just came out with an aluminium rear block though, might be worth getting if you want stronger clamping?

Edit - just for info, my boom is approximately 12.3cm from tip to start of motor mount. With no tail fin, but an RKH CNC motor mount, Hyperion 550mah mounted pretty much as far forward as you can and a big spin motor and XP-12 ESC at the front the CG is pretty much perfect with canopy fitted.

**Delarado** · 23-02-2012 04:44 PM

How did you cut the tail boom? unsolder the connection, pull the wires out, cut and then rethread and re solder?

What did you use to cut the boom?

Ill chop mine down now.

**Zeeflyboy** · 23-02-2012 06:21 PM

Dremel cutting disc... But a file or something would work (just slower)

Yes I desoldered and pulled the wires through first, I shortened them anyway since otherwise it's just added weight. If you shorten just bear in mind you need to burn off the enamel coating at the tips.

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