A return to model building and flying. Part 73

August 2011

Leicester Model Aero Club
(Open) Control line Carrier Competition

It all went surprisingly well considering the weather forecast was for strong winds and rain. It did not look promising at all in the early morning with trees doing the usual thrashing about, although the clouds were letting the sun through.

First flights in the morning were enough to wake anyone up! but I did manage to get the Hellcat down on the deck even if it then fell off the side. As the wind was  so turbulent I had decided to fly the Hellcat; I know it's traits very well, which helps; it's also very stable at speed, also very heavy; just means I don't get good slow scores, but stand a better chance of completing a flight.

After a leisurely wind up in the morning with contestants doing a lot of fiddling. I don't think anyone appreciated that on our site we have to have a compulsory one hour quite period when no ic powered flights can take place, which meant that the leisurely wind up left us running an hour later than we should have been at the end of the day. I couldn't make up my  mind if the mornings slowness was hoping the wind would drop or just unpreparedness, but after stuffing the barbecue down themselves, prepared by our hard working CD Andy Green, the enthusiasm seemed to get turned up a notch and indeed the wind did abate considerably as the afternoon wore on. I think everyone enjoyed themselves I certainly did, even managing two good landings which has restored a bit if confidence for the Nationals. We only flew Basic Carrier but there was more than enough excitement and organisation involved in the that event alone.

One thing I 'must' now complete is the spread sheet for carrier scores I have been working on. Working on paper is OK, but doing it electronically has too many advantages to ignore, like instant updating of positions, keeping track of pull tests/noise tests/ entry fees and not having to calculate anything and just typing in raw data. I don't know about anyone else but as the day wears on and I get tired my brain turns to pudding, so anything that takes away effort and brainwork is a blessing ( I do still soffer with ME/CFS although it may not look like it, I just manage the symptoms reasonably well ). As well as being more accurate, hooked up to printer, everyone could go home with a score sheet as soon as we finish too.

Picture below is me and my Hellcat on the day, all the messing about I have been doing with the Irvine 40 finally paying off.

Zoe Hellcat

All the picks can be seen here and will say far more than I can,
although you would think there was no wind to look at them, which was far from the reality.




Please note: regarding references to Motorvation Model Engines in the folowing piece, MME is no longer in business and I do not know what the present situation is? I am unable to answer any queries.

Sharma Diesel

sharma19Recently I have been cooped into evaluating a Sharma .19 diesel for Motorvation Model Engines with a view to MME becoming a dealer. For those that don't know, Sharma Engines are manufactured in India. As you can see this example bears a superficial resemblance to the old PAW design, but on closer inspection it is quite different. I am no engineer, so I won't pretend to do an in depth breakdown of how it's made or what it's made of. I don't even possess rev counter, and have never needed one in all my years of flying. It's quirt easy to tell if an engine is any good in a CL model, (1) does it start easily? (2) is it easy to set? (3) is it consistent? (4) will it drag mode the model you are trying to power with it around at the speed you want?  The last is the most subjective as a stunt model will have quite different requirements for team race, speed, or combat. Just timing the laps with a stop watch and keep changing props for comparison is one simple way of telling if things are any good, I have enough experience to tell if an engine has potential or is a dog just by using it. I tend to get dizzy and desperately try not to fallover if a model ever gets near or over the 160kph/100mph mark together with an arm that feels like it's  pulled out of joint, or end up doing a lot of swearing and running backwards in a strong wind if it is underpowered ( all experiences that flying an RC model can never give you LOL ). I am a very average flier that likes to thrash something every now and again if I get the chance, so that is where I am coming from and what you will get from me.

Now get ready for a good moan! Oh how I wish model engine manufactures would use sensible units; the entire global automotive industry uses cubic centimetres, but here we are apparently stuck in the middle of the 20th century with model engines still using cubic inches! I've lost track of the number of tv presenters that  state a distance in metres then in the next sentence quote yards, or metres that suddenly become feet then back again, or temperatures that seem to fluctuate between Celsius and Fahrenheit. It's no wonder that people get confused. There was a time when you could tell a diesel form a glow just because all diesels were in cubic centimetres and all glows in cubic inches (although I must admit things did go a bit woolly with either side quoting each others units when over 2.5cc at one point in time. I suppose I ought to thankful that that at least it's decimalised, or we could be stuck with likes of a 21/100 or a 7/20th... Doesn't quite have the same ring does it........! Strangely the Sharma website does quote the diesel sizes in cc and the glows in ci thus maintaining the old tradition, so why is this diesel stamped in ci? I'm still waiting for the first manufacturer or marketing idiot to call a diesel a Nitro engine.....!

Anyway, enough of my drivel.

John Walton of MME being ever the perfectionist, was not too enamoured with the finish on the engine, which apart from a few dints on the fins looked fine to me. So it was duly squeezed into my my now old Hallam Swift You will have to forgive the tatty front end of the model, its had many engine changes and is on it's second nose section, plus the fact that Solarfilm is not known for it's diesel fuel resistant qualities...!!. hallam swift and sharma diesel
The First problem was the fact that the bottom of the engine bearers had not been machined at all, and were not flat. This was just a little too much to ignore as it was twisting the bearers, but not enough to stop me flying it.

One thing I can say is that it has one the best piston liner fits I have experienced for a long time on a new engine. This undoubtedly gave it the very easy starting characteristics I experienced, bordering on a lazy flick more akin to hand starting a glow engine. Another thing that came as a pleasant surprise was the lack of vibration, I am used to engines of this size being a bit rough running with sometimes unpredictable in starting.

Flight testing was uneventful with the engine running at a steady rich misfire to avoid it over heating for the the first few runs. Because the compression and needle settings were so soft, by that I mean not critical, it was easy to get consistent runs what ever you set things at. The next days flying was cranked up a bit with a just breaking two stroke. Again no problems what so ever, except for one mysterious moment when it refused to start and would only respond to an exhaust prime. This turned out to be the needle being a lot more open than it should have been and flooding the engine. Restoring it to it 's original position gave a near instant start again. The needle restraining spring needs a little tensioning.

Couple of other things of note, the crankshaft is not threaded but hollow to accept a prop retaining bolt, not a new idea, but a very practical one, and the large compression and locking lever is very easy to use if you wear gloves, (which I always do for hand starting and they are reasonably thick leather), so that lever is a boon; as it would also be if you had to start the engine in the winter.

I was beginning to warm to this engine, I will be a bit reluctant let it go at the end of testing. Having got rid of a new PAW 19 some time ago because of it's very unpredictable starting and debatable performance (whether I just had a bad one I can't say as I only had the one to judge by), but this engine was like chalk and cheese. I have no idea what I can get out of it yet, as it it is still running in, and I had no muffler because none is available, so I was pushing things by attempting to flying it at my club anyway because of the noise regulations.

I have a strong suspicion that the lack of an available muffler has been the main reason I have never seen any of these engines about. It's nice to have open ported engines revving away, if nothing else they are easier to tune when you can hear what's going one, and any engine will be somewhat restricted in performance when you put on a muffler (strangler would be a better term);  but if you have nowhere to fly them, or get thrown out of your club because of it, I know I would sooner put of with a loss of performance  and still be able to fly; it's that simple: a case of put up, or shut up!.

In this day and age it is essential to have some form of quietening supplied with an engine, it can always be removed or modified by the owner post purchase. But not having one, or being able to easily get hold of one, is a recipe for customers ( that includes me ) thinking twice before handing over cash.

sharma proto mufflerSo after after the initial testing, with a bit of nudging and none too subtle hints from yours truly, J.W. produced a workable prototype muffler for me to test. The design should should also make it possible to fit it to other older radially ported engines that never had one in the first place, something that has been lacking on the market for a very long time. Although if they employ sub port induction all bets are off performance wise. PAW do make two types of silencer, but the standard one they supply with an expansion chamber makes the 1.5cc incredibly difficult to start for newbies. I suspect it has put more people off than encouraged. That size of engine becomes much more manageable when they are removed; but then you end up in a catch 22 situation if your club insists on silenced engines. The simple ring collector muffler works better, or should I say is more practical after a bit of sensible tweaking, but is too flimsy to fit other makes of engine.

J.W. also levelled up the bearers to a less stressful angle and also cleaned up the conrod which was a little poorly finished, and it has to be said that some internal parts are a little crude to say the least. But I have a pragmatic approach to low priced engines, I don't care what the engine looks like as long as it runs, runs consistently, and bits don't fall off. In this instance the bits that matter do seem to work properly. I have no way of knowing if this less than optimal finishing is standard, or if new ones any better. We may find out in the months to come? So all I can do is comment on the one I have loaned to me and not surmise about something I have no knowledge of.

A couple of days later I had the chance to test the muffler. I can report that it made only a very slight difference to starting, for me that amounts to not being easy to exhaust prime with a side mounted engine. One solution would be to have small hole in the collector ring on the opposite side of the engine, but I suspect for most people an inlet prime would suffice, as indeed it did for me once I had found the right settings. As previously when starting without a silencer and from cold, it still seems to need the needle open half a turn and the compression turned up a quarter of a turn from the running positions to get easy starts; nothing unusual there then. Hot starts are a doddle, just flick and go.

There is marked reduction in noise when flying, but I didn't notice all that much difference in performance. This could be down the the fact that I am using a 9x6 prop which is obviously on the large size and holding down the revs. All I can say at this stage is that In a model the size of the Hallam Swift I could quite easily go through the stunt schedule without the model racing away with me (given a little practice). In a slightly larger model I suspect vintage stunt events would be do-able, and some of the larger vintage FF models would be well suited too. I have yet to test smaller props and go for higher revs, but with the UK Nat's  looming large,and the engine is still running in, I am in no hurry to try right now. I'm just glad I can continue testing it now at my club site.

With regard to running in I have experienced no signs of a sudden reduction in compression, something that sometimes happen with poorly machined piston liner fits, and can't see any perceptible scoring on the piston surface after what must amount to five large tankfuls through in flight, even with the occasional accidental over compressed grind to a halt.

These engines are obviously build down to a price, so don't expect major manufacturers standards in finish or performance if you ever buy one. But they look like they could be an ideal power plant for sport flying, or tuning and experimenting with, I can imagine them suiting a whole range of vintage models. So providing a batch of other engines and sizes are a similar quality (or better) they will make very usable sport diesels in the 1.5, 2.5, 3.2 range, (.09, .15 and .19 if you must) and Coupled with J.W's silencers this will make a bit of killer combination, and even more so if the rc throttles work too. J.W. is already hintng at coupling a throttle to a variable restrictor in the muffler to try and keep up the head temperature when throttled down, an interesting concept. I'm impressed enough to already have an order in for a pain venturi 1.5. I am sure J.W. will not let any of these engines off his premises (assuming the deal does goes through) without all the minor niggles being fixed first; and probably run them too, just to make sure :-D

In conclusion: a bit roughly finished inside and out, but the bits that matter are well thought out and working, at least on this example. So you pays your money and you takes the risk if you buy one today. If Motorvation Model Engines gets the dealership, you can expect something that may cost a little more, but will be a little less likely to spring any nasty surprises.

I have no idea what the prices will be like, I want to know myself? So watch this space.

Knocking your own countries products?

I haven't had time to write anything about another abysmal UK Nationals weather wise. I'm actually at the point of wondering if it's worth writing anything at all? But one thing did strike me during a conversation with a non British Citizen whilst there, when I asked what lines he was using and mentioning that we had seen a few failures of this type of line. The reply was to the effect that they had never had any problems and that we British have a habit of knocking our own products.

Now I would be the last one to dispute this, but unless you live here for a considerable length of time and have first hand experience of a lot of shoddy goods over the years right up to the present day, this is not quite the whole story. The phrase, 'Rip Off Britain' didn't just appear out of thin air for no reason, the only reason it's not so prevalent these days is because we hardly manufacture anything! If things are good or even reasonable I will say so, if they are bad or there is a worry, I will say so too; only louder!

In this instance I have seen lines fail and in a very worrying manner. They were stranded tinned steel bought as a bulk reel for making up lines. A new set of lines had failed a pull test, and upon closer examination the failure had occurred on black patches in the middle of the lines. Obviously this was corrosion, either happened before tinning, or the tinning was not thorough. Either way this was no joke, as a whole bulk role is now suspect. On talking to others it appears not to be an isolated incident. As these lines all come from one supplier it does make you start to question things.

This is not restricted to lines made in Britain. Again I have seen crimped stainless steel lines give way or slip at the crimp on more than one occasion ( let alone things like the lines being wildly different lengths if they are made up ones from companies that you would think would care more? ). Let me state categorically that there is nothing wrong with crimping. Let me also state emphatically that this only holds true if the crimping is done properly. The latter implies strict quality control and testing. which I doubt goes on with the likes of made up control lines. And how often have you seen lines made up at the field with a pair of pliers or worst still cutters employed to produce the crimps? I have, and more than once.

All this is one reason I don't use crimps on stainless lines. I bind and use adhesive. I have even pull tested samples using weights with no adhesive to see how good they are, so I know that I have some latitude for error after applying the adhesive. Binding can also be used to spread the stress so that there is no sudden change as there is in the last crimp. Obviously this is not possible for producing lines as a business, for time reasons alone, so crimps are used along with all the attendant ways of failing.

So as you can see this is not simply knocking my own country's products but born out of a genuine concern about safety, and also not wanting to loose the hard work that goes into building models. So please check your new lines visually and carefully before even getting near a pull test, and then make sure you get someone to help you give them a good pull before that first flight. It could save a lot of embarrassment, money, and someone's good health. We don't have many accidents with CL., it must be be one of the safest forms of powered modelling around, but lines are what we rely on; so treat them with great respect and don't rely on the manufacturer to get it right all the time.

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