Comparative engine statistics

[Len Ward]

Why oh why cant we have comparative engine statistics with engine reviews?
I'm personally not interested in the finer engineering details but do like to know if it'd well made and how it performs.So why cant I see how various [say]45 two strokes stack up against each other when the latest offering from China or wherever is tested?
Eh?

[Allan Jordan]

Hi, Len, what a good idea, it could then serve as a buyers guide

[Flanker .]

It would be invaluable. I want to buy a RCV 58, but would love to be able to compare its stats with others in its class. Perhaps an online thing refered to a review along with maybe 3 other motor stats in print ?

[Peter Roberts]

Great idea - would be good for Electric motors too from various manufacturers. Either that or I use Motor Calc for electrics.

[Stephen Grigg]

Great idea Ive now several 46 type engines but the power varies dramatically.I had an OS46LA in a Seagull 40, but it didnt run to well and I couldnt figure out why.I took it out and gave it to an OS guru to investigat.Id bought a GMS 2000 47 at the club bring and buy for £10 and popped ir in .It totally transformed the model into  a much faster responsive  beasty fantastic.Ive now just bought a couple of OS46 FX on E bay itll be interesting to see how they perfom. it would be nice to have a scale of power chart so you had an idea of the power possibilty available on IC and Elecreic.I recently bougfht a Fusion electric and it had a chart with it that will be very helpfull to me in the future

[IanN]

The engineering whizz's on here will no doubt tell us you can't compare chalk and cheese, and that it depends what application you use the motor for. E.g. a long stroke motor designed to swing a large prop slowly isn't really comparable to a short stroke high rev screamer of the same c.c.

 

That said, I know exactly what Len is saying and I believe there is a use for such a fig.

 

Indeed, that used to be widely available - the old M.A.P. plans handbooks had a comparitive ratings system for engines where power was rated from A (lowest) upwards. That measure thus enable you to see that certain 1.5cc engines were rated E, and others F (& so on). More importantly, the quoted figs seemed to broadly correlate to what modellers actually experienced and so were a reliable and handy source of ref when selecting between brands of motor which you had no personal experience of.

 

 

[Mike Rolls]

A long time ago (in a galaxy far, far away) when the Aeromodeller did engine tests they included RPM figures for typical prop sizes, Although the way they did it wasn't perfect - like running tests for, say, 2.5s but using different props, the principle was very good and for more useful for the vast majority of folk than being told engine X gave such and such a BHP reading at so many RPM.

It would be extremely helpful if engine  and electric motor reviews were to include such figures.

Mike

[Mike Rolls]

Ian

As you say, the system used by the MAP plans service was pretty useful - although needed using with a bit of care as it tended to lump together motrs od very differnt characteristics (and there is the occassional howler in the listings caused, presumably, by transcription errors over time)

Mike

[Andy Mc]

That sounds a brilliant idea!

But I should imagine it would be a nightmare to compile, there's so many variables, prop size, fuel, optimum RPM, plug and weight, just to name a few.

[John Privett]

Mike - as you say, back in the dim-and-distant,  engine reviews gave tables of rpm vs prop sizes and also a power/torque vs rpm graph.  Using those anyone who knew what they were looking at could easily compare engines.

 

These days engine reviews seem to be more about the colour of the anodising on the head...

[Braddock, VC]

As most modellers tend to stick with one fuel be it 0,5 or 10%  it should be pretty easy to test all three which would give an indication of the fuel most likely to perform well.

Similarly with props, a selection from the most popular makes, say graupner, apc and master and use the same sizes for similar capacity engines, after all the power output at 16000+ rpm isn't of much interest to most modellers.

Edited By John Gibbs on 28/12/2009 10:08:39

[Peter Beeney]

    Reading these posts about older engines and RPM/BHP/torque graphs etc. induced me to go back and see what I could remember. I’ve never been an expert, on this, or anything else for that matter, but I used to read as much as I could.
    Just to try and enlarge a little on all the good stuff above, I believe that Aeromodeller were, at one stage, around the late 50’s, as I remember, developing a small dynamometer to be able to test the output of the engines at the time, mostly small diesels and some glow, all for control line use; consequently they didn’t have throttles. Some results were obtained and published. After that I’m not sure what happened to it.
    A dynamometer is a device that is capable of applying a varying load to the engine and then measuring all the output parameters. They had previously used a torque reaction beam, but like the ones that had been used on full size aero engines in the early days, this had been seen to be giving very inconsistent results.
    As with all these things, there always seemed to be quite a lot of mathematics involved in this, but one way of using these charts was to note, from the RPM/BHP graph where the maximum power output was and then, from a prop size table, i. e. diameter by pitch by RPM, prop it accordingly. Or in fact some 10% below this figure, to allow for the propellor unloading in the air. Some authorities gave this figure as up to 20% for sports models.
       Looking at this from today’s point of view though, it unfortunately doesn’t seem take into consideration some other important aspects, particularly from that of the the beginner. Ease of handling, reliability, longevity; some engines, it seems, can wear out very quickly. Even cost may play a part. Maybe a combination of all these things is the way to go?  So we either ask around and find out what everyone else is doing, or just rely on our own experiences. Which is now beginning to sound suspiciously like where we came in. It would seem that little changes.
    I reckon John Gibbs suggestion of the propellor test is good. They may vary considerably. Is much attention paid to propellor efficiency? After all, you could simply fit a large round flat wooden disc to your engine, it would certainly absorb some torque but the model might not fly very well.
    Personally, I think it would be nice to see electric motors subjected to a dynamometer test of power output. Then perhaps we could begin to get some form of comparison between both individual power plants and systems.  At the moment there is confusion in some areas, I believe. There is also a great deal of success, it has to be said, but is this simply sometimes a case of trying what the previous pilot has done? Or, in fact, just trying different set-ups until you get a result?

    For me, this is another nice nostalgic wallow here.  PB                                     

Edited By Peter Beeney on 28/12/2009 16:36:52

[Mike Rolls]

Peter

Nostalgia in spades! The dynnamometer you are remembering was referred to as the eddy-current dynamometer and was introduced in 1954 by the late Ron Warring. He had been unhappy with the earlier torque reaction beam which he reckoned was subject to gross levels of error from a variety of causes, including windage effect from propellers. In his original writings on the dynamometer he said that existing tests were over-estimating actual BHP levels by as much as 100% and to back up his contention his first test was on the K&B Torpedo 15 which  had won the F/F worls in 53 - and did again in 54.

He reported the K&B as produing 0.142 bhp (can't remember the revs off hand); it caused some ripples as tests within the previous year or two had given figures of between 0.25 and 0,30 for other comparable contest 15s such as the ED Racer, Elfin 249 and Oliver  Tiger Mk II.

Oddly enough, Ron's tests very quickly showed an upward curve - within a year or so of the K&B test he reported the AM 25 as reaching 0.181 bhp, and good motor though it was, the AM was no match for theTorp. Other 15s - Enya 15D, Webra Mach-1, Frog 249, etc., were also soon reported as having ouputs well in excess of the K&B. No explanation was ever forthcoming.

Mike

[Peter Beeney]

    Mike,
        Thanks for that, very interesting indeed. I suspect you must have really been into these engines, and aeromodelling, at that time. And probably still are!
    Was it possible some discrepancies were beginning to creep into these dynamo results, do you think? Although the integrity of these gentleman, I’m convinced anyway, would not be in any doubt.
    This was a very different age, bygone times indeed! I’d say that these people were only concerned with establishing some performance facts and figures, without any particular bias. Did they get overtaken by the speed of progress? In today’s rather more commercial world, are there any totally independent concerns prepared to organise and run such an enterprise as a suitable dynamometer for testing small power plants?
    I’d have thought that because the range of modern i/c engine manufacturers is, relatively speaking, now fairly limited, that most would be known by reputation. For instance, a standard trainer, where most beginners start, has the ubiquitous 46 as a power plant. One of a choice of about 4 or 5. With the equally ubiquitous 11 by 6 ACP propellor. Or, at least that’s how it more or less is on our patch. With the greatest respect to Stephen Grigg, in his post, if you have an OS 46LA, a plain bearing cooking engine, it’s unlikely to have the performance of, say, an Irvine 46. But it is probably cheaper! The competition amongst the maker’s is fierce, I think.
    In the electric motor department, however, it may be a different picture. It seems there is a bewildering array to choose from. As you said, to make a choice, a set of motor output performance figures would be a very good start. Plus a general quality check and report, such as that given by the WOO and occasionally Mike Billington, when they are doing engine tests. This might start to quickly narrow the field, I’m not sure the industry would fully approve, so I guess that’s already a non-starter then?
    Closely allied to this must surely be ESC’s and batteries. Should these be getting the same treatment? Again, the choice is vast.
    Anyway, the chance to reminisce about those past memories is very pleasant, looks like I shall start 2010 thinking about 1960!       Again, many thanks, and a HNY.    PB

[Mike Rolls]

Peter

They were indeed interesting times. I have always wondered about the speed with which Ron's figures escalated over tests. Like you, I am totally convinced of his integrity - he had a reputation second to none at the time. I do wonder if it was a case of hime becoming more at ease with the machinery being  used, but obviously I have no idea,

I looked up the K&B test again - not the full one, but the synopsis in the Aeromodeller Annual and I had fogotten that he actually tested two examples, one considerably better than th eother. I do wonder if indeed he was unlucky with the samples he had and that they might have been both done on the examples used successfully at the Worlds (the '53 event was the first appearance of the motors). The poorer example only managed 10,600 on a Tornado 9x3, whereas the motor he used for the test did 12,200 - big difference!

Maddeningly, I can not find that he used a 9x3 Tornado on any other 15 he tested, but he did use a 9x3 Tiger on several which was turned at 11,500 by an Eifflander Special (rated at 0.249 BHP), 12,200 by an Enya 15-D (0.252), 12,2oo by a Frog 249 (0.252) and 11,100 by a Barbine B40 Testa Nero ().189).

Of course, I have no way of knowing if the Tornado was a significantly lesser (or greater) load than the Tiger, but the variety of figured do puzzle me,

All the best

Mike

[Ed Darter]

tables of stats would indeed be a good idea, but would need to be used with a degree of caution. Fuel used (not just nitro content), current atmospheric conditions and type of prop will all have a bearing on the results. For instance, not all 12x6 props are made equal !

[Steve Hargreaves - Moderator]

I think it would be a great idea too.....get a selection of motors & commonly used props...use a standard 5 or 10% fuel & measure the revs of each motor.....I don't think we would actually need to know the power produced but could go off the revs......after all if a Super Enya 40 turns a 10x6 at 13,000 rpm & an OS Tigre 40 only turns it at 12,000 then the Super Enya is more powerful yes....& will pull your model around with more authority!!

 

Oh I know that certain engines produce more power at higher/lower revs than other & the OS Tigre 40 will leave a Super Enya 40 for dead if you strap a 12x6 on it but as a comparison for the ngines used most of the time by most modellers in most models then I think it would be facinating......

 

I wonder whose engines would be "the best"....my money would be on OS but I wonder by how much??

 

Mind you what is a "good" engine? Is it one that pulls your model around at warp speed but demands expensive fuel, is a pig to tune & cuts out as soon as the mixture is a tiny bit wrong or is it an engine that goes a bit slower but is more tolerant of its owner.....h'mmmmm!!!

 

Facinating subject....

[ken anderson.]

RIP ic engines.......

 

   ken anderson..

[Steve Hargreaves - Moderator]

Mike, I wonder if the difference in performance from those yesteryear tests might simply have been variations in the tolerances of the engines tested....as we know modern manufacturing & CNC machines have made consistency a byword for machined parts...I suspect this was not the case on the older capstan lathes & such.

 

Thus two modern engines would probably show very little difference whereas one made by Old Joe could be significantly better than the one the new apprentice turns out!!!

[Mike Rolls]

Posted by Steve Hargreaves on 04/02/2010 13:50:02:

Mike, I wonder if the difference in performance from those yesteryear tests might simply have been variations in the tolerances of the engines tested....as we know modern manufacturing & CNC machines have made consistency a byword for machined parts...I suspect this was not the case on the older capstan lathes & such.

 

Thus two modern engines would probably show very little difference whereas one made by Old Joe could be significantly better than the one the new apprentice turns out!!!

 Steve

There certainly were greater discrepancies back then between individual expamples of the same motor than one would expect  now, For example, I had two Elfin 149s, one of which was much better than the other.  I don't think that can be the reason for the upward trend in RWs figures, however. With the exception of the twoTorp 15s, one of which was certainly a clunker, and the other may have been, dependent on just what sort of a load a 9x3 Tornado represented, there was a definite increase over time from motors which simply didn;t reflect what people were getting in the filed. Perhaps the variations between individual examples was even greater than we realised at the time, and Ron was lucky woth his exmaples of low poowered engines and unlucly with his powered ones, but that does seem to stretch credibility a biot.

Mike

[Steve Hargreaves - Moderator]

We did used to hear dark whispers about manufacturers/distributors...er..."refining" their products before submitting them for test.....effectively "blueprinting" them.....not that I'm cynical or anything but I wonder if this might be a reason.....

[Mike Rolls]

I'm sure that if they had the opportunity, the manufacturer or distributor would want to ensure that a good example was tested rather than a poor one. Whether they had that opportunity or not I, simply don't know.

Mike