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Ron’s HeliProz South . Century Helicopter . MTA Hobbies

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e-Lite Machines Corona > I just installed my BT tail belt drive and now I can't stop the tail from hunting!?!?
 
 
slowracing
Heliman
Location: Williamsburg, VA

I know similar questions have been asked before; I searched the forum and found all the threads on the tail wag but none of them helped. So here it goes again

First let me tell you my setup:

Lite Machines Aluminum Crutch
Atomic Force brushed motor
BT reinforced feathering plate
BT carbon flybar
BT tail belt drive conversion
Standard size stock tail blades
Stock main rotor blades
I was running a 2 and 4 degree hubs, but after the BT flybar install I went to two 4 deg hubs.
CSM-200 light wait head hold gyro
HDS_877 Digital Micro Servo (I was running a Hitec MG85)

Before the belt drive conversion the tail was pretty solid, not perfect but very close to it. Now it is wild at best. More gain gets me a fast smaller hunt and less gain gets me a long slow hunt and a lot of drift. I installed the digital servo after the belt swap, it heloped a lot but the hunt is still there. The biggest problem I can see is the play in the tail blades themselves. I can move either blade what seems like a deg or two without the bell crank of servo arm moving (all those parts are good and tight). This type of play was the problem in my Trex until I got it out, now it’s rock solid!!! Is there anyway to get this setup tighter…less slop?? I’ve looked it over a lot and can’t see anywhere to improve it (without buying a BTR setup).

Any thoughts or advice would be greatly appreciated.

Also are any of your running the 110 tail blades? I see Helihobby sells them just for the tail belt drive setup!?!?

Thanks,
Sonny
05-03-2006 Over year old.
 
 
computerbob
Senior Heliman
Location: Westchester County, New York

Sonny,

Same here after switching to the BT belt. Here is what I did, following the suggestions of others, and not necessarily in this order. Carbon Fiber tail pushrod (3.5mm OD or even 5mm). Purchased a 21-tooth pulley from sdp-si.com to replace the blue, 28-tooth BT pulley. Added two #6 nylon washers between hub and each blade instead of one. Cut down 120 TR blades about 1/4 inch with a radius (instead of a square tip) and beveled the leading edge. (Matt suggested this blade mod awhile back.) Put a #4 steal washer between spider eyelet and spider and made sure the spider eyelet and collar were very snug against spider. This is real tricky -- if you tighten too much the spider will build up friction and melt. I also tighten the 2-56 screw so that bellcrank was rather snug. Also try different bellcrank holes. In the end I went back to the 28-tooth pulley, so the fix, as you say, is to eliminate as much slop as possible -- and the mod to TR blades worked wonders. I also flew with 110 blades with no problem, but liked the cut-down 120s a lot.

-Bob-
05-03-2006 Over year old.
 
 
coroman
Heliman
Location: France

Hello !

I have got that problem to ,with my BT elevated tail rotor ...

It's horrible to paid 150$ for bad result
05-03-2006 Over year old.
 
 
slowracing
Heliman
Location: Williamsburg, VA

Bob,

Thanks for all the helpful hints. I try the washers, and the cut down blades. I have the servo mounted on the tail about and inch from the rotor so I know the rod is not the problem. What pulley did you order from sdp-si.com (pitch size that is)?

.080 (2.03mm) MXL?

Thanks again,
Sonny
05-03-2006 Over year old.
 
 
computerbob
Senior Heliman
Location: Westchester County, New York

Sonny,

21-tooth pulley part # A 6n16-021df1208 (mxl, .125" belt width, .250" bore ID)

I guess the main problem is that the higher ratio of the BT belt will exaggerate any faults in the LMH tail system at higher rpm. It appears some people have this problem and others don't. You can try the 21-tooth pulley, but the best solution is to get the slop out of the tail. Also try the 120 cut down blades (example: http://users.bestweb.net/~davidson/corona/TR.jpg). And make the spider as snug as you can without friction and use the metal washer on eyelet to help give more surface area to eyelet. I keep a second spider on hand just in case I tighten it too much and it melts.

Coroman, The elevated tail can be more of a headache because of slop in the added length of pushrods. I've also mounted a small HS-56HB servo (and also tried a HS-81) on the elevated section of the tail and used a very short piece of 2-56 rod connected to bellcrank. That helped a lot. But most of the problem is the LMH tail. It's a great and simple design, but seems to be happy with lower rpm.

Also, running high head speed (with 2-dot grips or high kv motor) will increase tail blade rpm and cause the same hunting. Any vibrations messing up gyro? Not too sure about settings on CSM-200.

Good luck to all.

-Bob-
05-03-2006 Over year old.
 
 
slowracing
Heliman
Location: Williamsburg, VA

Well it looks like you guys did it. The tail wag is all but gone completely. I cut down the blades, added extra teflon washers around the balde mounting set screws and added the washer to the spider. It's as good or better than before

Thanks again.
05-03-2006 Over year old.
 
 
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e-Lite Machines Corona > I just installed my BT tail belt drive and now I can't stop the tail from hunting!?!?
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