Upgrading Helicopters

Introduction

Considering that there is a huge after market in this area, as a sceptic you would be forgiven for assuming it's all just a Sales pitch ! To a certain extent this is true, but how do you sort out the wheat from the chaff ?

Reviews are usually not much help because constructive criticism is hard to find - it's difficult for a Magazine to criticise Advertisers anyway.

However, there are logical and tested (by me and Vincent) improvements to be had. Vincent flies Raptors and I fly Shuttles.

Improvement Areas

These areas can be improved ;

a) Tail stability and control.

(It's much easier to fly a Helicopter if the tail stays still and only moves when you tell it to)

b) Overall stability.

(This is all to do with Mechanical and Radio setup)

c) Control precision.

(This involves mechanical range and servos/servo arm alignment/movement)

d) The pilot perceived way the Heli. flies.

(This is all about confidence in the machine - if you are confident, you can approach new manouvers. If not, no progress is made, or progress is slow).

1) Stable Designs

Ideally, you want a Heli. that will sit still in the hover (a relative term ! ) without use of the throttle stick under no wind conditions. Of course, setting up for this condition is paramount.

Of the Helis I have flown so far, the two that stand out are the Raptor 30 V2 and the Hawk Pro. Both are very stable in the hover, especially in a wind.   This makes control and moving around far easier.

The two Raptors flown have all high spec. digital servos , 560 Gyro or GY401 and fast servo (JR8700 and 9254) on the tail.

The Hawk flown has all standard Futaba 148's and was very stable on these and HLG200. The tail has been was upgraded to a fast servo (Futaba 9254) but did not curw the tail issue.

I remain to be convinced yet that a Shuttle is as stable as the two above, and I have flown 4 (2 were older designs Z, ZX and ZTS and 2+) so far. To be fair, the Shuttle is an older design, and has been superceeded by the Sceadu, so this is not an equal / fair comparison. What I find strange is that Shuttle-1 was a better flier than Shuttle-2 - and I don't yet know why ! However, Shuttle-1 did have the benefit of carbon main and rear blades. This could also be due to excessive wear on Shuttle-2.

Current Contenders (30 class)

a) Hirobo Shuttle

If set up properly, is an ideal beginners machine as it is very stable for learning. It is lighter than a Raptor, so a .32 runs well and a .37-.40 is very responsive. Can run standard 148's on all controls except the tail. Getting rid of the worn parts on Shuttle-2 has improved it by 100%.

Upgraded tail to 401/9254 combination which is a big improvement. Interestigly, the 401 Gyro performs better at the rear boom mounting point, allowing 100% gain to be used. Mounting in the standard Shuttle bay area only allowed 75% max gain and tail was not stable. Doing this on the R22 chassis was successful and 95% gain was obtained.

Upgraded the tail to Quick UK parts due to shredding two belts and changed tail rotor mechanism to avoid chains reversing themselves.

The most effective mod I made to the Shuttle was to add the autorotation plastic bar (£5.00) to the rear of the swashplate. This holds the swashplate rigid and makes the Heli. much more stable. Works also with the Quick UK metal swashplate. Controls are more precise and responsive.

After the loss of the tail twice (autorotating piroettes tend to cause damage), which were both due to the boom moving inwards and slackening the belt, as standard I now put a screw in the chassis to boom end, and another in the gearbox to boom connection.

Club Check

Not in favour as generally not as aerobatic as the Raptor. Does not have the pitch range of later designs.

b) Kyosho Nexus

Flew well and was as stable as the Shuttle 2 Plus once tail was sorted out and the Gyro changed to a Gy401 and 9254 servo, even with a "flapping head".

Club Check

Not as stable as the Raptor, but close. As stable as the Shuttle.

c) Thunder Tiger Raptor 30 V2

Very stable, even in a wind. Ideal beginners machine.Standard servos - unknown. Upgrades improve performance. Kit cost is higher. All ball joint version costs more. Has enough pitch for Aerobatics or 3D.

Club Check

A quick check of the members at Red Kite shows that the Raptor is the most popular, which speaks volumes. However, they are generally used with 9254 servos and Futaba GY401 gyro which is a £150.00 combination.

Needs a screw in the rear fuselage to boom joint for the same reasons as the Shuttle above.

d) Century Hawk Pro

Very stable, even in a wind. Ideal beginners machine and works well with standard servos. Yet to be tested with upgrades. Kit price very reasonable. Has non-belt driven tail and is all ball joints. Using a .32 is underpowered - use a Toki .40 as it is 1/2 a pound heavier than the Shuttle.

Upgraded tail with 401/9254 combination which is a large improvement. It now is as stable as a Raptor.

2) Training Undercarriage

It's imperative that this is used  ;

a) On a new Heli. when trimming and setting up.

b) Any time major changes ( Gyro ? ) are to be tested.

c) When practising new  or low-level nose-in manouvers.

3) Linkages

Z bend linkages are to be avoided if possible as they introduce "slop" when they wear. These are unavoidable on a standard Shuttle as the servos are so close together. Introducing ball joints would cause the wires to clash with each other. The pitch servo arm length (and movement) is limited by the tail servo mount.  

(It is possible to raise the aileron servo and use the Quick UK tail mount servo kit to overcome this limitation and allow more pitch) Already done and tested on Shuttle-2.

In general, all z bends should be dispensed with, and replaced with ball joints, if possible.

Likewise, when looking at prospective purchases (kits), make sure all connections are ball joints.

2) Main Blades

a) Wooden Blades

Wooden blades are fine for hovering, and basic eights and circuits, but not much more. They suffer from changes to the material from combinations of  heat, humidity,  and temperature. They also need constant adjustments to tracking and go out of balance easily. They are however, very cheap to replace, and ideal for learning.

b) Carbon or Fibre Glass

Symmetrical consistent profile blades are necessary for aerobatics.

Much stiffer than wood,hold shape, and are more constant/predictable than wood, but a lot more expensive. 

Reputed to improve performance. However, not all blades suit all Helis ! Like propellors, testing is required to find the right blend. How do you evaluate ?  - borrow some !

3) Rear Blades

a) Plastic Blades

Usually supplied with the Heli. kit. Tend to suffer from flexing along the length of the blade. Tend to be not very wide either. Cheap to replace and fine for learning

b) Carbon or Fibre Glass

Tried and tested some carbon blades which were around 50% wider than the original Shuttle's. Made the tail more controllable and much more responsive.

An improvement.

4) Gyros

Heading hold Gyro is an improvement over the standard piezo.

Having tried both CSM HLG200 and Futaba GY401, there is no comparison.

The CSM with a 9254 is not fast enough to keep up with the servo. The GY401 in non DS mode cannot send frames fast enough for the 9254. The GY401 in DS mode and 9254 is perfect and allows 100% gain to be used as necessary. (Assuming Tracking and Blades balance) Tail is rock solid in the Hover with this setup.

Club Check

A majority of the members are using the Futaba GY401 and 9254 servo combination. From my own testing the CSM HLG200's performance is unacceptable with standard servos and cannot control faster servos. Have yet to try the recomended Hited servo.

5) Tail Servos

There is a possible improvement depending on how fast the Gyro can send messages (pulse or packet) to the servo and how fast the tail servo is. (0.12 s / 60degrees is minimum standard for an HLG200)

Tried a 9254 (0.06s), with HLG200 on my Shuttle-2 and it still allowed tail wavering in a wind.

6) Header Tanks

Header Tanks serve two main purposes ;

1) To keep the fuel supply level with the Carburettor needle valve and thus the flow constant.

2) To act as an easily seen extra fuel resevoir.

Improved starting on my first Shuttle, and added to second automatically. Also gives an extra 2 ounces of fuel reservoir meaning 10mins. on the Tx timer is now feasible.

A worhwhile improvement on any Heli.

7) High Wear Parts

Certain common parts on a Heli. are always moving and therefore are likely to wear quicker than others.

On a Shuttle these are the Slide Block, Radius block, and Swash Plate. I was about to replace these with new plastic parts when the metal versions (Quick UK) became available on E-bay at approximately the same cost.

a) Slide Block

No play at all now.

b) Radius Block

No play at all.

c) Swash Plate

90 degree one used with existing plastic Autorotation unit. Much more solid.

d) Flybar Carrier

This was changed due to the fact that I have already broken 3 of the plastic ones. The metal one gives more Elevator movement and is stronger.

8) Boom Mounted Tail Servo

The reason for doing this is to get more Pitch available. The tail servo depth limits the length of the pitch servo arm to the 2nd hole. The standard Shuttle therefore, only has 0-9 pitch range and if set for 5-6 degrees at mid-stick, has no negative pitch. This is a problem for circuits and wind as the Heli. will not come down. For autorotations the manual advises +12 to -5 (a range of 17) which is unobtainable with the standard set up. Additionally, the connecting rod now uses ball-links instead of the original Z-bend/wire/ball link configuration.

Moving the servo to the tail and substituting a 4 hole servo arm gives approx. +10 to -10 (a range of 20) which covers all three (Aerobatics / 3D / Autorotations).

9) The biggest improvements ?

On a Shuttle fit an "anti-rotation guide".

On a Shuttle fit a boom mounted servo and raise the aileron servo to avoid the elevator wire.

On any Sport Helicopter fit a Futaba GY401 and 9254 servo combination.

10) Standard Model Weaknesses

After a few very annoying mechanical failures, Vincent and I decided to document our collective (and the Club) experiences as it should help avoid similar problems. It is very frustrating when you don't know about these issues, and then crash, only to find out there is a weakness that "everybody" knows about (except you).

One of the things you notice with the more experienced Flyers is the modifications they make to the "standard" kits to avoid mechanical failures. By standard, I mean kits that are not designed to withstand the rigours of 3D aerobatics.

Thanks is due to the Contributors to this section ; Vincent O, Alan D, Dave N, Myself , etc.

1) The Hirobo Shuttle.

Weaknesses

a) Tail Gearbox moves.

b) Slight Hover Instability.

c) Rear Gearbox - Chain Reversal.

d) Lack of Pitch Range.

e) Tank Feed Height.

f) Rudder linkage is a Z bend rod.

a) The Tail gearbox moves towards the main mast, slackening the belt drive. This will allow the belt to jump it's runners and the resulting loss of tail power (or belt shred) will cause a fast pirouette and disintegration if not experienced. The correct remedy is to shut the engine (idle-3) and autorotate down (and pray ?)

The solution is to drill a small retaining hole through the plastic and aluminium boom near the rear of the gearbox. Be careful to use a small screw (Fut servo screw is ideal) and minimise it's length so as not to touch the belt. Or replace gearbox with Quick UK parts.

b) This is due to the lack of an option part, which is not fitted as standard. The part clamps the rear of the swashplate, minimising movement and improving handling. Note that most Helicopters have these fitted as standard nowadays. If an older Shuttle, the swashplate and the stabiliser will have to be added. I originally did not want to strip my original Shuttle, so found a piece of wire of the correct thickness, and having cut and filed the swashplate to take the wire, heated the wire on the gas ring, and melted the plastic to take the wire. Having then added the optional stabiliser, the Helicopter was much improved.

The Shuttle Plus 2+ has the newer swashplate and stabiliser fitted as standard.

c) The chains on the older Z and ZX, ZXX jam and a loss of tail power results. If one chain jams, you may get it down in one piece - if both jam then see weakness a) above.

Solution is to replace the gearbox, either with Quick UK parts, or Shuttle 2 Plus 2 parts.

d) In standard guise the rudder servo is mounted directly above the pitch servo and restricts the pitch servo arm length. Consequently it also restricts the pitch range that can be achieved.

The solution is to remove the rudder servo and re-position at the rear on the boom using either the Hirobo or  *Quick UK"  parts. Use a longer servo arm to get full movement of the pitch range and use the pitch arm hole nearest to the paralel position of the aluminium arm. This is linked   to f) below.

e) Tank feed height is too low - should be in line with the carburettor intake. For consistent engine runs a header tank is necessary.

f) Change rear pushrod to a ball joint or better - a rear mounted servo (Quick UK or similar) 

2) The Raptor .30

Weaknesses

a) Boom moves

b) Gearbox Pins

a) The Raptor suffers from a loss of the tail when the boom slips forwards and loosens the belt,

Solution is the same as the Shuttle, but at the main mast end.

b) Pins on tail gearbox shaft come out.

3) The Hirobo Sceadu .30 or .50

Weaknesses

a) Tail Slop.

b) Main Gear Wheel's Teeth Wear.

c) Standard Exhaust fails.

d) Header Tank Needed.