I'm doing a statistics project on engines and would appreciate any thoughts or information you could help me with. I am comparing YS and OS two and four strokes, pretty much the engines that are available now, with a few extra YS for a little more data.

[link=http://cid-e6c10583b12bccdc.skydrive.live.com/browse.aspx/.res/E6C10583B12BCCDC!112]Link to the report[/link]

The main thing I could use help with is prop information. People say with four strokes 'you can swing a bigger prop' so I'm trying to find the best way to quantify this. One idea was to sum the pitch and diameter. But most importantly I could use some help with evaluating the prop selections I found for each engine. If you have any ideas of how to quantify engine vs. prop load I would really really appreciate it. And any ideas of what kind of statistics you would like to see about these engines. Thanks so much!

YS 63FZ 12x8
YS 91FZ 15x8
YS 110FZ 14x12
YS 110FZs 15x11
YS 120SF 16x10
YS 140L 16x12
YS 140Sport 16x11
YS 140DZ 17x12
YS 160DZ 18x8
YS 170DZ 18x10

OS FS40 13x7
OS 56FSa 13x7
OS 72FSa 14x7
OS 81FSa 14x7
OS FS91 16x6
OS FS91 pump 16x6
OS 110FSa 16x8
OS FS120 16x7
OS FS120 pump 16x7
OS FS200s 20x8
OS FS200s p 20x8

OS 46AX 12x7
OS 55AX 13x7
OS 61FX 13x7
OS 75AX 15x7
OS 91FX 13x9 (15x6?)
OS 120AX 16x10
OS 140RX 16x14
OS 160FX 18x12
OS BGX3500 20x10

Joe, if you have access to all these engines, I would setup a bench stand that would allow me to measure static thrust. Select a range of prop diameters with pitches between 4 and 10.

I would determine top RPM for each prop on each engine, Determine the static thrust of each prop on each engine. You may want to check head temp also.

Another data point would be fuel consumption, both at full RPM and at "cruise" speed.

So what eles are you going to do this summer???

Don

ONe more thing, as different engines will have differnt shaft dimentions, make sure that you use one brand and series of props on all. There will be some differences between brands and types of props.

Don

Is your real quest somewhere in here?

Bill

Here is some published info on engines versus props and rpms by different users. You can select either by prop size or by engine size and also for small engines or large engines. Hope this helps your info gathering task.

http://www.rcfaq.com/RPMSTATS/rpmbymfr1.htm

Richard

i also find that interesting
a .91 4 stroke can swing a 14x6 (os)
while a 91 two stroke (os) can spin a 13x8 or 14x6
only difference is rpm
id like to see the end result

Thanks guys.

I added a link to the report I made so far.

I am NOT personally gathering any data, just finding specs online and making comparisons.

Sort of. I guess what I personally want to see in the report is the real benefit of running a four stroke, if any.

This is never going to work (OS FS40 13x7) use a 11-6

Whoever dreamed up most of those OS prop sizes had been looking at the bubbles in the beer glass too long

Clarence Lee for the most part had a set of Zinger "test props"( the same props used not just same size) that were used, so you could compare engine to engine because the props were standardized. If the manufacturer specked a different prop he would use them too. He never would say anything bad but let the numbers speak.

I think the largest problem you might find is that 2C and 4C engines only really "cross paths" at about the .90 mark. OS and Laser make an .80 4C but that is a really odd size for a 2C. 2C's come in .60's but that is an almost unheard of size in a modern 4C. What would you compare probably the most common engine in the world, an OS .46 AX, to? Satio 1.00 is very common but there will always be doubt if you compare it to a .90 or 1.35 2C. I guess you could dig for a K&B 1.00 ( http://www.mecoa.com/kb/67/9500.htm ) but I think the obscurity of this engine would still leave doubts.

The only real place these engine cross paths is about the .90/91 mark. OS, YS, Jett, Satio, Rossi, Magnum, Thunder Tiger and so on... all make either or both 2C and 4C engines in this size. I think the answer to your question is in the .90's.

Bill

Yeah some of the specs I got are pretty absurd. Fortunately statistics are generally based on samples, and samples always tend to have some degree of inaccuracy. I think it would be save to say the 13x7 is an 'outlier'


I was really hoping that by plotting the different data against things like size, weight, and cost would show...something. So far it's confirming that 2 strokes offer the most bang for the buck, however the big YS engines compete fairly well against similar size (displacement) OS 2 strokes.


Thanks for everything so far, it has been helpful including the PM's I've received. This certainly beats cramming for some stupid exam about "how many boys and how many girls like commercial A, B, and C". Yuck.

Four strokes of the same displacement as two strokes use the same or slightly smaller props. What is different is that the four stroke is somewhat lighter and you can use a larger displacement engine. So because you can use a larger four stroke you can use a larger prop.

the formula for prop load D+P in your graphs is not correct.
You should use D^4*P instead.

PR you are correct but the original question was about statitically quantifieing the un quantifiable to me.Engines are inanimate things,we make them work for us the way we do.I'm a saito like that sound person and will fly a heavier model to suit.

Maybe there's a better angle to approach this from.

Suppose you started with a popular kit like the Sig Four Star or a popular ARF like something from Hanger 9.

From there, you could test every two and four stroke engine within that model's practical power range.

Bill's post on the common displacement of .91 led me to this idea.

But, the important aspect of this approach is that you are putting the same work load on all of the engines, i.e., the same airframe/drag/lift, etc.

I know some will disagree with me on this, but using a bigger engine does not always result in a better flying model. Anyway, this would allow you to test performance and not just rpm and static thrust calculations.

David

I agree with the start of your post dave but i think you miss my point in that i'm saying cob the power to suit what you are flying and go with the sound your engine is making,go with the flow.It's an art that you cannot quantify.

The first problem you have is that YS motors use a different induction system, so comparing them to anything else would not work. comparing 2 stroke to 4 stroke would make more sense if you compared an OS 2 stroke to a an OS 4 stroke. Same quality of motor built for a similar application. You will find that prop size generally follows displacement size as rule and that bigger props at a lower rpm are more efficient. Because 4 strokes and 2 strokes motors due the same job at comparable weights and a 4 stroke uses less fuel per unit of output. 4 stroke would be favored for most general applications, but cost is a big factor as well. What are you trying to prove here is my question. Big props more efficient then little one? 4 strokes are more efficeint then 2 stroke?, etc. This is why your doing this class so you can sort these things out. good luck

The important issue here is power and how it translates to performance. That is very tricky to sum up over a wide range of models. One model expected to fly at one speed with some sort of take off distance in mind would allow you to compare fuel consumption and power plant weight.

You can put a 20" prop on a FS-20 and it will run. That doesn't mean it's making a lot of power. For any of this to have meaning you have to quote power or at least RPM with the prop size. Anyhow this sort of data might be useful if you are truly optimizing an airframe, but to Joe Modeler it's useless trivia.

If I would compare engines, and one engine turns a specific prop faster than the other engine, that faster spinning engine clearly delivers more power. There are no if's about that.
But when I need fast spool up, fuel puddling and power curve play large roles, which makes four strokesmore desirable.
Because engines are inanimate, they can be quantified very well! An engine is defined by it's measurable characteristics, and exacting choices can be derived from that. There is no magic or feeling involved. Just plain mathematics.

Engine comparisons i like but people are more difficult to quantify than inanimate engines and we make them.You say you need a fast spool up/fuel puddling etc..this is all about your need and wants,emotions in other words,qualify that for me?

qualify or quantify?
IIRC this thread is about quantifying engines, not my personal needs.