The story so far - What else do we know? - The model - So what's really new? - The engine - Finishing the model off - Flying - Conclusions - Finally - Specification .
This is a rather different kind of review to that which we normally present and the result is one man's (probably jaundiced) view of something which is certainly different to the current trend. Read on and decide...
It is no great secret that the Kalt company is in the process of producing a new '30' size helicopter of metal, rather than plastic, construction. Some prototypes of the machine have been seen in this country, in the hands of various demo flyers, and it has become known as the 'Alpha 30'. This is the Kalt name for the machine, although the potential UK importers would prefer to call it the 'Genesis'. When fellow editor, Mike Cherry visited Japan recenfly, he came back bearing photographs of a prototype of the above machine, fitted with an Enya '53' four-stroke engine. Raving expressed some interest in this machine - purely because of its curiosity value - I was surprised to learn, a few weeks later, that there was one on its way to Traplet from Kalt, courtesy of Mr. Oki, for Mr. Day to review! Er, yes, but we would have preferred the '30' two-stroke powered machine! Sorry, too late!
When the machine arrived. superbly packed in a large cardboard box. an even bigger surprise was that it was already built, with engine and servos fitted. A mixed blessing titis, since I was now faced with talking about a machine which I had not built and for which I had no instructions! With no knowledge of - and a pronounced dislike for - four-stroke engines, I was clearly about to embark on a steep learning curve.
A little research has established that Kalt intend to market the machine in three forms:
1) A 30 powered basic machine with a belt start. which can also take an engine fitted with a pull-start.
2) An up-dated '46' powered machine with a top-start system.
3) A '53' four-stroke powered machine with a top-start.
The top-start system will be available as an up-grade for the '30' size version. Prototypes of all of the above are actually being advertised for sale in Japan, but are not available elsewhere. The reasons for this are that the people who might import them into the rest of the world are waiting for a fully developed version and are not convinced that the world at large wants to go back to metal-based helicopters. As to the interest in a four-stroke powered machine...
All-in-all, it seems that we are extremely honoured to have this prototype to play with, so I will swallow my personal prejudices and determinedly refuse to look a gift horse in the mouth.
In some ways, this could be described as a metal 'Space Baron S'. The undercarriage and the complete boom, tail drive, tail gearbox, tail rotor and tail feathers are, in fact, identical to that machine. Two metal sideframes clamp the boom between them in a manner very familiar to those who have owned earlier Kalt models. These frames appear to be one stamping which is bent into left and right hand versions. The undercarriage is bolted onto the outside of the frames just as it is on the 'Space Baron' with metal spacers between the frames. A complex machined aluminium mount accommodates the motor and fits between the sideframes. The motors crankshaft points upwards and the cylinder head faces forwards. The clutch/maingear/tail drive set-up looks almost identical to the old 'Baron 2OMX', although closer examination reveals that everything is actually different. The clutch is a one-piece metal item, which is almost unique on a Kalt model. Pitch input is accomplished by means of a 'Space Baron' pitch yoke pushing a wire up and down the centre of the mainshaft. The shaft itself is a new item, but with a very familiar-looking autorotation unit. All of the swashplate controls are again identical to the 'Space Baron', with the same mixer being driven up and down by the same system. The difference is that the top bearing holder is of aluminium, with a spigot to accommodate the clamp-around 'SB' unit.
As supplied, the tail rotor pitch linkage consisted of a length of thin piano wire, encased in a plastic tube, which extended all the way from the tafl gearbox to the front-mounted tail servo. Despite having two supports on the tail boom, the front half of the wire was unsupported and there was a lot of lost motion in the system. To make things worse, the supported section took a very winding course along the boom. More anon.
A metal gyro plate bolts between the rear of the frames and has offset holes which allow it to bolted in two positions. There are also two sets of holes in the frames at different heights so that you actually have a choice of four positions. An identical plate at the extreme front of the model serves as a receiver/battery mount. A standard 'SB' tank is clamped between the sideframes. These frames are rather further apart than the 'SB' plastic frames and the tank is free to move something like a quarter of an inch sideways. A Kalt three-way filter is used which allows the tank to be filled via the feed line.
Two vertical metal frames separated by spacers serve to mount the servos in a very similar manner to the 'SB' and are attached to the front of the side frames.
The canopy is of similar design to the 'Alpha 60' and is attached to two side stand-offs (similar again to the 'Space Baron'), with a clip which attaches to the front undercarriage crossmember. This is quite a convement system as you can unclip the front attachment and hinge the canopy upwards for glow-plug and switch access.
Supplied with the model was a set of K&S blades, very similar to those recently supplied for the 'Enforcer', but without the angled tips and weighing 125 grams each. These were quite well matched, the spanwise CG's being a 'mere' 2.5 mm different.
We made brief mention last month of the new rotor head. Apart from the use of the bladeholders and flybar paddles from the 'Space Baron S', this is completely new. It also features what I believe is the first underslung flybar from Kalt. A complex centre moulding incorporates guides for the top end of the wires which drive the mixer unit up and down (unlike the 'SB', where the guides are incorporated in the main shaft) and this is supported by an aluminium collar which also accommodates the two fixing screws whieb screw into the mainshaft from each side (ala 'SB').
The flybar has two operating cranks which look remarkably like Baron 20' items, apart from which the whole system of inputting pitch commands is identical to the 'Space Baron'. The bladeholders are connected by a 'through axle' which floats in two rubber 'O' rings. An interesting difference here is that the blade holders are retained by nylock nuts on the end of the axle, rather than the familiar capscrews going into the axle. A metal collar inside each bladeholder butts up against the 'O' ring and serves to hold the axle central, but there is a big. big difference between the diameter of the axle and the size of the holes in the 'O' rings!
This means that the entire blade/bladeholder/through axle assembly can be raised and lowered by some 3 to 4 mm without any resistance being met. The assembly can also be rotated by some 5 to 10 degrees in each direction relative to the main shaft. Perhaps it should be pointed out right now that it feels perfectly normal in the air!
So far, much mention has been made of the 'Space Baron' and other previous Kalt machines. I feel that I should apologise for this, although I really cannot see any other way of making the comparison. It is difficult to decide whether the machine is to be regarded as a 'metal Space Baron', or as a throwback to earlier designs. Fortunately, I have a 'let-out', because it has a four-stroke engine fitted!
As mentioned earlier, this is an Enya '53' four-stroke engine. On this engine, the valve gear and pushrods are mounted at the rear, with the carburettor attached to the backplate. Examination reveals the rather surprising fact that the carb appears to be a two-needle unit which has been modified to an air-bleed type.
The relative disposition of the tank and carburettor means that the carb is about one inch below the bottom of the tank. It is no surprise, therefore, to find that fuel literally pours from the carb when the tank is filled. What is, perhaps, surprising is that the model came complete with a pressure line from the silencer/pipe to the tank vent!
Another surprise is that the silencer (in itself an item which is frequently omitted from a four-stroke) appears to be a tuned pipe (apparently, a turned-from-solid K&S unit). This is on the end of a very long header and it seems very unlikely indeed that it can operate in the conventional sense. After some experience of running the motor and flying the model, I believe that the purpose of this exhaust system is to act as a rev limiter, rather like those currently employed on state-of-the-art (?) control-line aerobatic models (FAI F2B). Although so far unexploited, I believe that this technique could be used to advantage in '3D' flying - though this cannot be the purpose here.
It was very soon established that the pressure pipe served no useful purpose and made the engine go very rich in certain circumstances. It also gave a very large 'flat spot' when the throttle was opened. It also became full of brown 'gunge' making its way from the silencer to the tank. Removing the pressure line gave a great improvement, but the real secret was to increase the nitro content of the fuel. I started off on 'Duraglo 5', but as I was already using 'Superglo 16' on the OS 615X in the XI-pro', it was convenient to try this on the Enya. This was a real breaktrough and the motor now runs very consistently. On a subjective note, I find the persistent flat drone to very boring!
One characteristic which still persists is that, if the model is landed and the motor allowed to tick-over for several seconds, on opening up and lifting off again the motor will hesitate momentarily before continuing. I suspect that this is caused by the plug cooling off. Incidentally, the plug does not resemble the usual Enya type and I have no idea what it is!
Er, no not that way! The model came fitted with a 40 Mhz PCM receiver (we wondered whether the transmitter was still to arrive!), which we couldn't use, an obviously elderly (and, therefore, suspect) l000 mAh nicad and no gyro.
Having acquired a suitable receiver, gyro and battery (the manufacturers are not relevant here, but the battery was a nickel metal hydride, if you must know), it was discovered that some considerable setting-up and adjustment was needed and it was apparent that the model had not been flown.
In fact, there was no threadlock, or lubrication, anywhere and many items were loose, while the mixer unit and all head linkages were extremely tight. Add to this the previously mentioned tail rotor linkage.
None of this should be construed as criticism, but it all seems rather odd. The mystery of a fully assembled model deepens!
At this point, I paid a visit to J Perkins (Distribution) Ltd, the importers of previous Kalt machines to show it to them (they hadn't yet seen an 'Alpha 30' in four-stroke form) to find that they already had an up-date for the tail linkage (I'll leave it to you, dear reader, to ponder that one!). This consisted of a reverse bellcrank fitted to the rear of the left sideframe. One side of this is attached to a shortened version of the existing piano wire link to the tail and the other side connected to the tail servo by a rigid pushrod.
This whole set-up is worthy of further comment. On the 'SB', the tail linkage is all on the right-hand side and, with a little care, it is possible to get a dead straight run from the transfer bellcrank to the tail pitch belicrank. On the 'Alpha', the servo and change-over bellcrank are on the left side, while the tail pitch bellcrank is still on the right. As supplied, the linkage on the 'Alpha' started from the servo (on the left side), then passed under the boom, through the guide on the tailplane saddle (on the right side), then to the pitch bellcrank.
In the up-rated system,rigid pushrod, and change-over bellcrank are all on the left, leaving the wire-in-a-tube to pass under the boom as before.
Where is all this leading? Well, there is no reason whatever why the tail servo and switch plate should not be swapped over, putting the tail servo, pushrod, bellcrank, etc. all on the right side. This would then allow a dead straight linkage as per 'Space Baron'.
Following all of this, it only remained to await some suitable weather, although I did spend some time running the motor under an awning in the pouring rain. Actually, I was quite impressed!
Like most people who enjoy the English climate, I eventually got fed up and flew the machine in very windy, blustery conditions. It coped with this quite well, except that I could not stop the tail from oscillating. Really, that's not quite the right word for a swing of about 30 degrees each way at a frequency of about 3 or 4 cycles per second! Reducing the gyro gain to virtually zero made very little difference and I had to turn the gyro off before I could do any real flying.
This was an interesting experience, because the machine was quite docile and the lack of a gyro didn't cause any real problems. For years I thought that I needed one and it's quite a shock to find that I don't!
Later investigation showed that there was a lot of mechanical gain in the tail rotor linkage and this was reduced to the same amount that I am using on the editorial 'Enforcer'. I could now fly quite comfortably with the gyro off, but things still weren't right with it working. The whole process of setting the model up was very much one of suck-it-and-see, because I had no instructions and no experience of four-strokes. There is a lot more torque available and you have to run at a lower speed, which means that much more tail pitch is required and this makes things much more critical (and easier to fly!).
With no idea of the pitch range that was required, this had to be set by trial and error and took some time to get right. The change to higher nitro helped considerably but, at the time of writing, I still have no idea what the head speed is, or what the pitch range is.
Having got things somewhere near right, I could relax and begin to enjoy it. At this point I discovered that the gyro was now working the way that I expected it to. I suspect that the gimbal on this particular unit was tight and needed some flying to free it up.
With a copy deadline now fast approaching, the weather decided to stop co-operating (?). It wasn't just the almost continuous rain, but a drastic lack of light. When a shot taken in mid-day sunshine (quick, or you'll miss it!) looks like it was taken at sunset, you have problems. So now you know why we have studio shots this month (for 'studio', read 'Tony Wright's garage').
I still don't like four-strokes! However, I do have the feeling that some better weather and the chance to do some more flying might just change my mind. That rotor head really does work very well, and the whole machine is rather more smooth than its near-twin brother, the 'Space Baron'. How much of that is due to the engine and different gear ratio is hard to say.
Although smooth and docile, it is surprisingly lively. Advancing the throttle produces a fast climb without any tendency to 'load-up', although the tail wags quite noticeably. I have yet to find a cure for this, despite trying 100% 'Up mix', I suspect that this is my chance to find out what 'Acc mix' is for!
All-in-all, I like It, but it is difficult to see it as a new machine with something different to offer. I know that there are people who like four-strokes and they seem to be the fashion in Japan at the moment but, despite the 'silencer', they are not any quieter to my ear. Add to this the increased complexity and maintenance costs and I just don't see the point.
I must thank Kalt Sangyo Co. Ltd. and it's President, Mr Oki, for the chance to try this intriguing development machine. As far as your being able to buy one is concerned, it is a fully developed version of the two-stroke machine that is most likely to find its way onto the European market and we understand that the price may be a little off-putting!
|Product:||Kalt 'Alpha 30 FS/FC'|
|Manufacturer:||Kalt Sangyo Co. Ltd., Itopia Roppongi SO3, 2-2-2 Roppongi, Minato-Ku, Tokyo, Japan.|
|Main rotor diameter:||49.25 in. (1.25 m.)|
|Overall length:||42 in. (1.067 m.)|
|All-up weight (dry):||6 lb. 13.75 oz. (3.12 Kg.)|
|Main gera ratio:||7.33:1|
|Main to tail gear ratio:||1:4.6|
|Control requirements:||5 servos and a gyro|
|Power requirements:||Enya '53' four-stroke glow-plug engine|