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Thunder Power RC . Real Raptors . Mikado Modellhubschrauber

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Tandem Rotor Helis Vertol Chinook > Hirobo CH-47 Chinook; Timing belt problem
 
 
Reindeer
Heliman
Location: South Oregon Coast

Looking for feedback on this problem. Lifted a newly assembled CH-47 into a hover on its maiden flight. Everything appeared to be working fine until main blade covering and parts started to fly off the blades. As it turned out, the timing belt had slipped a few cogs, causing the rotors to go out of synchronism, and the front and rear rotor blades began striking one another.

I'm absolutely certain the timing belt was properly tensioned and sequenced, according to the instruction; and, upon shut-down of the flight, it still appeared properly tensioned, but the blades had slipped out of timing sequence. In fact, there is no way I could grab hold of the belt and pulley and intensionly force the belt to slip on the pulley. What's going on here?? Is there something that I am missing??

The real shocker is the cost of replacement blades; $200!!! For a set of woodies????! Has anyone found an acceptable substitute? I found a set of Helimax carbon fiber blades that would be the right size, for about half the price. The problem is, they are fully symetrical, rather than semi-symetrical. Has anyone tried this substitute? If I don't get any negative feedback, they would be worth a try at half the price.

Other than this incident, I have no negative comments about the model. The instruction are very good and complete. The finished model is a thing of beauty!

Regards, Garren
03-01-2006 Over year old.
 
 
bwellmaker
Senior Heliman
Location: Long Island

Sorry to here about your 47. I built one and had the same issue. If I remember correctly it says to set the tention to 3mm. The problem I had was with how much force on the belt to move it 3mm. Tighten the belt until you feel the cogs when turning the rotor head with out blades. I will look thru my notes and some old post in the scale threads and see if I can find the measurement for the jack tention screw.

Good luck,

Butch
03-01-2006 Over year old.
 
 
Reindeer
Heliman
Location: South Oregon Coast

Thanks for the input, Butch. Did you break blades with your incident? If so, did you just bite the bullet and buy factory replacement blades?

Tower Hobbies is selling sets of Helimax carbon blades sets, 470mm. for $38; with a $25 total order discount, this equates to less than half the cost of factory replacements. The fully symetrical airfoil wont have as much lift as the factory semi-symetrical; but the blade is slightly wider (which gives more blade area, and, hence, more lift). I figure with the on-board controller, I should be able to program out the difference. For the difference in cost, its worth a try.

Garren
03-01-2006 Over year old.
 
 
dgshaffer
Elite Veteran
Location: New Jersey

Been there! Broke that! Bought them!

Like any belt, it needs to be broken in and stretched. I've got mine tight enough so that I can barely twist it at center and I can feel each cog as I turn the rotor heads.

I tried the MS composite 470 blades but they were too flexable. MAH makes a set but by the time you're done buying 3 sets you close to the cost of the semi-symmetrical Hirobo replacements which perform really well on the heli. WAY to Friggin expensive though!!!!
03-01-2006 Over year old.
 
 
bwellmaker
Senior Heliman
Location: Long Island

Garren,

I took the bite. I did not try any other blades. For woodys they are expensive. I only used the factory blades so cant help you on that one. I have to agree with DG on the factory blades and belt tention. I felt if I made it any tighter it would have bent the heli in to. Feel lucky it was only the blades. That is the cheep part of this heli. I think to replace the mixer/gyro unit would set you back about 900 frosty's.

Good Luck,

Butch
03-02-2006 Over year old.
 
 
Free Bird
Senior Heliman
Location: Somewhere in the USA

Vertol Belt Tension

I've been flying my Vertol (new version) for several months off and on (about 3 gals), and so far I haven't encountered any problems with the belt or the heads getting out of sync. Per Jeff G. I made sure that the belt was super tight, I too can feel it cog slightly when I turn it by hand. I too agree that the instructions could mention something about the amount of force used to judge belt tension.

FB
03-02-2006 Over year old.
 
 
Reindeer
Heliman
Location: South Oregon Coast

I'll bring this thread to a closure. I talked with Jeff Green about the slippage problem. He gave advise, which seems to answer the question as to whether there is sufficient tension in the timing belt. Basically, regardless of what the instructions say about testing for proper belt tension by measuring belt deflection, if you can grab hold and twist each head in an opposite direction, and the belt will jump a cog, there is not sufficient tension in the belt.

He recommends: pre-tension the belt; test for slippage; run the heli without blades for a brief period (to equalize the tension for a new belt); make the slip test again; then install the blades. Thereafter, He recommends making the slip test after each flight (well, maybe after each day's flying). He's been flying without incident for over a year.

I'll be replacing with factory blades. He made me an offer I couldn't refuse.

Garren
03-02-2006 Over year old.
 
 
TURBINE MASTER
Senior Heliman
Location: SW ENGLAND

Hi
NHP blades in england sell carbon set for vertol and yes have belt extra tight and check every flight
03-02-2006 Over year old.
HOMEPAGE  
 
 
Free Bird
Senior Heliman
Location: Somewhere in the USA

Vertol Blades

can you supply more details about the NHP Vertol blades? Part number, cost, where can you get them? Thanks!

FB
03-03-2006 Over year old.
 
 
Copter Doctor
Elite Veteran
Location: daleville/ft.rucker, al

the reason why you really cannot use just any blade on this machine is that the weight and cg of the blades designed for this type head. as with all multibladed heads, there is a lot of weight positioned at the tips and in the leading edge. semi symetrical blades provide more lift and it wouldnt make sense to do them symetrical cuz i know of no vertol/ch47 owner who want to roll theirs inverted. if theres someone who does, please take videos anyway...........yeah.

drive a rotary, fly a rotorcraft
03-03-2006 Over year old.
HOMEPAGE  
 
 
TURBINE MASTER
Senior Heliman
Location: SW ENGLAND

NHP blades

Hi Free Bird
Revolution Models England
www.revolutionmodels.co.uk
Hope this helps
Turbine Master
03-03-2006 Over year old.
HOMEPAGE  
 
 
dgshaffer
Elite Veteran
Location: New Jersey

Those blades are symmetrical although they're advertised as being for the "Chinook"
03-03-2006 Over year old.
 
 
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Tandem Rotor Helis Vertol Chinook > Hirobo CH-47 Chinook; Timing belt problem
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