Flying Sites - R/C Aero Portal - HOW TO...TROUBLE SHOOT THE BELL 47 TWISTER

This article is aimed at the complete beginner, the person who knows very little about the Bell Twister or the Graupner Bell 47 Micro.

The Graupner Bell Twister Out Doors...

but what if you have trouble with your Bell Twister?
Read On!

This article covers some of the most asked questions - regard Twister Bell 47 and Graupner Micro 47 Helicopters.

Before we get into the general Questions and Answers part of the article, I would like to give some general advice regarding Li Po batteries as per the type used in this model.

Always stay with the battery and charger when charging. If the charger goes wrong and does not auto cut off a Li Po battery can catch fire. If the battery ever swells or gets hot, disconnect it and get it out of the house. You can immerse it in salt water to prevent it catching fire or exploding.

When flying your helicopter and the power runs down. STOP FLYING. Recharge the battery. If you take the battery down too low in voltage held, it may never take a charge again.

Deep Discharge of battery packs is not covered by warranty, so it can be a costly mistake as you will need to buy a new battery. The Twister chargers feature a very safe cut out when a battery is below voltage. This is to prevent a cell being charged with miss-balanced cells. See later in the article.

Q : My Twister tail keeps glitching and the trim keeps changing, how do I cure it?
This could be a number of things. The trim changing automatically has us all reaching for the screw driver to alter the settings on the trim pots on the 4 in 1 box.

DON'T!
Before you adjust electronically check the collets. This mast collet is likely to be the culprit.

The mast collet is similar to wheel collet, but with a grub screw or screw to tighten it against the mast. What you will probably find is that the collet on the bottom of the mast is loose and this is causing the trim to change and occasionally the tail to glitch. If the collet keeps loosening, try a bit of thread lock and if that doesn't work, invest in a new collet. The collet comes in the screw set bag.

Q : Before I realised my tail glitching/ twitching was the mast collet. I fiddled with the pots on the 4 in 1 box
There is no easy fix to this, if you are a beginner, then I would visit your local model shop or let an experienced flyer to re-trim the heli. If you are able to hover straight and level and feel you are capable of trimming the heli, then re trim very small amounts on the pots (or pot if using the single pot version). Each time disconnecting to reset and trying a hover in-between adjustments. Remember - patience and small adjustments! The heli will retrim, dont panic!. An experienced flyer will trim it in minutes; a beginner could struggle for hours.

Q : I crashed my heli and broke a blade, I've put a new blade on, but the Heli now vibrates. What has changed?
Again this is an area that could have several causes, but most likely is the inner shaft. A slight bend on the inner shaft and the whole airframe vibrates. There are two possible cures.

One is to take the inner shaft and roll it between to flat pieces of wood or tiles and if the bend is slight and the mast is only bent once - you may straighten it.

The easiest fix is to buy a new inner shaft. There is actually and option inner shaft which is worth fitting to the helicopter when you are proficient at flying. The option inner shaft is CNC cut and features an aluminium U shape fly bar holder which of course does not break like the plastic one. However the shaft still bends in a rotor strike, so the option shaft is something worth considering after you have learnt to fly the model.

Q : I crashed my heli and broke the blades, I've put a new set of blades on, changed the inner shaft but the Heli still vibrates. What has happened?
Most likely you have bent the outer shaft as well! Time to change both the inner and outer shaft. Don't run the helicopter with excess vibration as it damaged the bearings, gears and can upset the radio gear.

Q : I bumped my heli and the fly bar flew out. I have put the fly bar back in, but now the heli has the death wobbles. Every time I try to take off the airframe goes mad and gyrates.
The fly bar is designed to fit a certain way. There are two ways it will go back, you have put it back the wrong way. Take the fly bar out, seat it correctly and all should be fine.

The Fly Bar coming out (alone, from it's normal connection swivel joint) and being replaced cannot cause this symptom.... but the Fly Bar flying off WHEN STILL CONNECTED to the top section of the head down to the normally hidden square peg in hole joint (by the joint separating), and being replaced the wrong way DOES cause it! It can only happen if the Fly Bar shaft top section is connected to cause the bar to trail the blade, and you cannot do that from the top fly bar swivel joint.

Q : The fly bar is in the correct way, but the helicopter sometimes gyrates and changes trim. Sometimes it flies backwards and full forward doesn't stop it. It can be uncontrollable.
What we probably have here is a separated swash plate. In a good bump the swash plate can become separated. The answer is to clip it back together using some force. I actually advocate a slight FIX here. Read On. If you use a drop of cyno ( super glue) to fix the swash plate shut, it will never separate again! Be careful as you do not want to glue the top of the swash plate, just the part where it clips together. If you take the swash plate out, use a drop of cyno and then press the swash plate back together with pliers ( not to much force, but be firm). Make sure the top of the swash still rotates. It's a fix I have used and it lasts and lasts.

The other alternative is to buy a new swash plate, fit it and avoid bumping the heli in future.

Q : Motors spin, but the rotors do not work.
Check the mast collets. They have become undone.

Q : When flying the heli for long sessions, the power suddenly drops.
This can happen if you fly battery pack after battery pack indoors and do not give the motors time to cool. Basically the motors are over heating. In some cases a tired battery might be the culprit, but generally hot motors cause a lag in power. Try to allow the motors to cool between flying sessions.

Q : The canopy splits all the time.
By its lightweight nature/ nature of the model the canopy can often be split down the middle from new. It has a small overlapping join with a super glue fixing. Generally at some point in flying it becomes split. Often in delivery with a slight knock, while still packed in the box the canopy can split. It is a weak area of the model, but if it were made stronger it would not be as light weight and so the heli would not fly as well as it does. Its not a big problem as cyno will stick it. If you re-enforce the inside of the canopy with thin masking tape and drip cyno on to the tape, that will stop it coming apart ever again. However - if you do leave it as it comes ( weak) , in a crash it generally splits and can be glued back with no damage. If you re-enforce the canopy, in a crash it can crack and is impossible to repair successfully.

Q : I flew my Twister for a full battery charge and now it will not charge up again.
This is most probably caused by flying or running the rotors until there is no life left in the battery. DO NOT DO THIS with Li Poly Cells. They are not like NiCads or Nmh batteries, they do not need to flattened before charge. The charger that comes with the Twister is set to detect a low voltage and refuse to charge. If you have gone below the voltage the battery is safe to recharge at, then this is the reason the battery will not take a charge.

Other makes of charger may bring it back to life, but I would consult your local model shop regard such problems. In the even the battery is dead, you will have to purchase another battery. It is an expensive mistake to make. DON'T RUN THE BATTERY COMPLETELY FLAT. The moment the heli starts to loose power, stop flying and recharge.

Q : One of the motors does not turn, what do I do?
The motor not turning could be something jammed in the mechanisms, but if you check it and is not.Take the motor out and check it, if the shaft will not turn, then usually the motor is finished. Generally a bump, over heating or brushes failing could be the cause.

We ask a lot of these small motors and the easy fix is to buy a new motor. They are expendable and economic to replace. Do not attempt to fly the heli with a seized motor as you will damage the 4 in 1 unit, which is much more expensive to replace.

Q : I want to paint my model, what would you recommend?
Generally you could use Tamiya Acrylic paints, Humbrol Enamels are also O.K as they are plastic friendly. If you use different paint, then test a bit first. Most model shops stock Humbrol in sprays and tinlets and Tamiya in pots and sprays.

The model below was repainted by a Flying Sites Forum member called Novice. It is a Twister Bell painted as Westland Sioux 'X-Ray Tango 243', a training machine used by the British Army in the 1960's