One thing that seems to cause a lot of
uncertainty is which micro heli is the right one? Well there is no simple answer
to this as they all have their own place in the market. So to help you make a
choice I have laid out the basics of each model.
Currently the Align T Rex 450 followed by the
Thunder Tiger Mini Titan are by far the most popular mini helis although this is
a very dynamic part of the heli market so things are changing all the
time.
All the effective micro/mini helis are
battery powered, an IC (internal combustion) engine at this size is not very
practical and is a noisy messy little thing which is not really what you want
for flying around or close to the house anyway!
A Little History
The development pace of small electric models
has been incredibly rapid, just a few years back the standard micro heli would
have been the Icarus Picolo or Century Hummingbird, both are conventional single
main rotor fixed pitched models, their size and slow rotor RPM made them
effectively very unstable and hard work to fly, they don’t tolerate wind at all
well which means they are more suited for flying indoors, but their poor
stability makes flying them indoors very hard work.
At the same time if you
wanted a micro heli with collective pitch and aerobatic / 3D capability then the
MS Hornet was the best available but needed very careful building and set up to
get the best out of it, for it’s size and time it was great but needed a good
amount of skill and experience to have any really chance of making it fly
well.
The two most significant things to happen to
this size of models and in effect split it up into two separate size and types
of models was:
Firstly the development of the contra
rotating models like the Twister Medivac (click here to see) & more recently the Blade CX 2 (Click here
to see).
The advantage of this type of model is they are much more stable
than a model of this size should be due to the very heavy flybar weights, a
feature which would not work well on a conventional model. These models all come
ready built and ready to fly. They are the most economical way to get into model
helicopters, their stability and size mean they really can be flown inside the
average house with little practice. As they are still fixed pitch type models,
which run at a relatively low rotor speed, they have little energy in them so
don’t tend to damage themselves much in a crash. The flip side of this low rotor
speed and their small size means they do not tolerate much wind so although they
can be flown outside it really does have to be truly calm.
Secondly small models got a little
bigger, the 450 sized was developed of which the Align T Rex 450
(click here to see) has been the most successful and practical.
All these models feature collective pitch control of
the main rotor and have significant advantages over the older collective micro
models like the MS Hornet just by being a little bigger means they are big
enough to use more conventional construction techniques, i.e. they are screwed
and bolted together rather than glued together which means construction,
maintenance and repair is a whole lot easier! That little extra size also means
they are no where near as fiddly to build or set up, the stability and ability
to fly in wind goes up dramatically to.
At one time there was some pretence
that one model could be used for both indoors and outside flight. Whilst any
small model can be used for both, anything with collective pitch will run at too
high a rotor speed and be too sensitive to cyclic inputs to comfortably fly
inside an average room but great for a garden, park or large sports hall. The
contra rotating models like the Blade CX2 or Medivac are absolutely ideal for
flying in a limited area as they have the stability and slow damped reactions
you need to learn to fly and progress in a limited area. So decide what sort of
model you want and where you plan to fly it, Garden, Sports field etc then
collective pitch is the way to go, if it’s going to be mainly around the house,
office or work shop then got with one of the contra rotating
models.How Big are they? How
Long will They Fly for
on 1 Charge of the
Battery?
First of all these models are small.
The
contra rotating models are about 340mm rotor diameter and weighs about
230grams.
The T Rex 450 is roughly 700mm rotor diameter and weighs about 800
grams.
The average 30 sized glow model like the Raptor 30 V2 which has a
rotor diameter of 1245mm, is 1150mm long and weighs about 3000
grams!
Because of their small size they do not and
can not have the same stability as a larger model but their low mass does allow
them to bounce much better than larger models so survive a crash that would
re-kit a larger model. Spares are also normally cheaper for the smaller
models.
All of the later electric models use Lithium
Polymer (Li-poly) battery packs with a few using Lithium Ion packs, these all
have much better performance than the older NiCad batteries and are basically
the same type as used in Laptops and mobile phones. Lithium batteries need a
little more care when using and charging but are really the only practical
option.
Flight times on most small electrics either a
contra rotating model or 450 sized will be roughly the same at about 7 to 8
minutes depending on flying style. Recharge time is normally about a hour, it’s
common to buy 2 or 3 batteries so you can have a good flying session although in
the early stages of learning you will find your brains fairly cooked after one
pack and you will need to take a short break anyway.
Contra Rotating Indoor Models
All these models come ready to fly out of the
box, you just have to charge the flight battery and put the none rechargeable
batteries in the transmitter. The transmitters supplied with most of these
models can be used with a flight simulator which a very useful feature but they
are non computerized basic transmitters so can’t really be used with a more
advanced helicopter. They are simple models which are a very easy and cost
effective way in to helicopters but are limited to hovering or slow forward
flight only, can only be flown out side in calm conditions.
450 Class Helicopters
Most of this size models come in kit form or
possibly with the airframe mostly built but the radio equipment still needs
fitting.
As they have collective pitch they need a reasonably capable radio
control transmitter, the ones supplied with the contra rotating type models will
not do the job. The good thing about needing a reasonably capable transmitter is
that this same transmitter can then be used for almost any larger helicopter or
even fixed wing model in you might acquire in the future.
You will need a motor, Electronic Speed Controller,
4 small servo’s, a receiver and tail rotor gyro to finish fitting out the model,
obviously you will need the flight battery and a charger for this before it can
take to the air as well. Batteries and chargers are a mine field but don’t get
too worried about these at this time, one thing is for sure you will need and
eventually buy more than one battery and charger!
Do not be fooled in to
thinking it’s a good idea to go for the cheapest model and fit the cheapest
servo’s and gyro in it because your only learning to fly and that you will get
something better when you can fly. This is very much a false economy as the
model will be much harder to fly and will not be so robust in a crash - leading
to a longer more frustrating and demanding time learning to fly it.
Always fit good quality servo’s preferably
with metal gears, the best ones for the T Rex 450’s and Mini Titan’s are the
Align DS410M. The Spartan Quark gyro is at this time the best gyro to go for, go
for a cheap gyro and you will almost certainly not be happy with it and will end
up buying Quark shortly afterwards anyway. The radio control (transmitter) will
make up a big part of the cost of your purchase and currently the newer 2.4G
radio’s seem the way to go as they offer lots of advantages to any one flying
electric models in particular as they are almost immune to interferences which
can be a issue with electric models. The number of 2.4G radio’s available
currently is limited but the available choice is set to grow rapidly in the next
few months, a 6 channel radio is all you need for this size of model but if your
planning to move up to bigger or glow engine powered models then you ideally
need 7 channels so keep this in mind.
