I'm trying to choose an engine in the 50-100cc range. I've drawn up a spreadsheet with all the big names in this range, and distilled the important data (HP, weight, cost, etc). In addition, I stripped all the RPM data that RCFAQ's offered, and entered it in the spreadsheet with the results of ThrustHP for that combo as a comment in the cell.

As you can see, RCFAQ's data is a little spotty at times, so I'm asking for anyone with one of the following engines to please post their RPM data if they have it (include prop please). Just reply to this thread and I'll update the sheet. Thanks!

Fuji CDI
Fuji EI
G62
FPE 4.2
FPE 5.8
BME 50
BME 105
BME 110
DA 50 R
BCMA 60
ZDZ 50NG
ZDZ 60RV
ZDZ 80RV
ZDZ Super 80
3W-50
3W-55i
3W-60
3W-70
3W-70US
3W-75
3W-75TS
3W-75US
3W-80Xi

[IF YOU WANT TO VIEW THE SPREADSHEET, SAVE THE ATTACHMENT BELOW TO YOUR HARDDISK AND RENAME IT WITH A .xls EXTENSION... SILLY FORUM]

Well I only have 2 comments.

#1 People just dont buy an engine in the "50-100cc range" Thats a wide range and you have to match the engine to the plane.

#2 You have missed a bunch of quality engines: Brison, Brillelli, Taurus and some nice twins offered by companies listed ie DA 100...3w 106 etc etc.

Find the engine size and weight that's suitable for the size of th plane you intend to fly for awhile. Find the engine that you can afford. Don't run it lean and go fly.

Not all aircraft come with an engine suggestion on the box. My application would do fine with anything in that range.

Thats precisely what I'm doing.

Maybe you guys misunderstood me. I'm doing this to help myself choose, not neccesarily to provide a comprehensive reference tool. The engines I listed are the ones I'm interested in seeing numbers on. So that said, do you have any numbers you could share please?

3W55i.....7000 rpm 22x8 xoar prop

Well it's very unusal that someone would need this much data to select an engine for their plane.

try this chart http://www.rcaerobats.net/GAS_ENGINE_WTS.htm

doesnt go up to the 80cc range

Most people predetermine what plane they want to fly along with a general wingspan class. That determines what weight class they are intending to fly. The list of engines and sizes you have provided indicates that you don't have any idea at all what you intend to do and are simply "shopping" engines. I think more than a few of us anticipate that after a 6 month period of beating the engine numbers to death this same situation will come up with a plane selection list as well. Pick a plane before you pick an engine. Better yet, pick a size of plane that you intend to fly for a period of time. Then start looking at engines.

Most of the engines in each size class you have provided do pretty much the same thing as another in it's class. RPM numbers have too much diversity due to propellers used, altitude, muffler used, and owner tuning knowledge/ability to provide an accurate baseline. Performance levels are often a matter of perception. A perfect example is when an engine is described as having "authority" in pulling out of a hover. Just what the heck is "authority"? Weight of the aircraft has a profound impact on the engines ability to pull the plane. Is it a biplane or a mono plane? That also has an impact. What price range can you, and want to, afford? If you are designing an aircraft most would first determine the task that the aircraft is to fulfill then determine what engine size and type will power the craft.

Essentially what you have done is to have provided the perfect thread to begin an engine war of epic proportions and I don't think anyone wants to get it started. I don't believe that many carry much faith in manufacturer HP numbers as well. Those that provide HP numbers usually provide a number that appears high because, if it's accurate at all, was obtained at an rpm level that will rarely, if ever, be reached in modeling applications. Therefore that number is useless.

Worse, you built a list that fails to include some engines that may well be superior to those listed on it. Your personal location suggests in the abstract that this may not be for sport modeling, which impacts the engine facts you are trying to develop to an even greater extent.

Why not just pose a question and draw upon the enormous bank of experienced R/C pilots on this board? If you are trying use a spreadsheet to choose a suitable power plant, you will no doubt end up with a less than perfect combination for your intended purpose. Have you factored in such things as vibration levels and prop sizes. I would be a expensive mistake to mount a BME 110 to your plane only to find that the 28" prop it requires will not clear the ground.
Not trying to bash you here, but save yourself the aggravation and don't try to re-invent the wheel.

AirWizard, thank you very much.

SilverSurfer, I respect your right not to help me, but I would imagine that silence on your part would be the best way to deny me your assistance. In that light, as well as under the auspices of common courtesy, your most recent post seems rather rude. At no time had I considered that I would need to prove myself worthy in order to solicit assistance from this forum (after all, if people were unwilling to help, one would assume they wouldn't be on the forum at all). I will, however, indulge you such that your assumptions are proven false and perhaps other members may yet salvage my project.

Contrary to your accusations, I have already chosen my aircraft, and constructed (most) of it. I've designed and built it from scratch with wood, foam, fabric, 3D vortex panel codes, and my masters degree in Aeronautical Engineering. I have absolutely no regard for "back of the evelope" parameters like "authority", which is the impetus for creating this list. Making this list comprehensive is not an investment of time I'm interested in undertaking, and your assertion that I've omitted "better" engines without offering a metric for comparison is exactly the kind of valueless gossip that I'm looking to avoid.

As to the wide range of displacements I'm considering, you should not be so suprised. It is not my intention to do 3D sport aerobatics. Surely you haven't forgotten how all of the prevalent rules of thumb in this hobby produce aircraft that are stunningly overpowered by GA standards: you don't see 800HP Cessnas, now do you?

I can see this was a bad idea (in practice, not principle).

Oh, now I understand, he's an engineer. That speaks volumes. I have been working as airframes and powerplants mechanic at Patuxent river MD for thirteen years and have to deal with these types on a regular basis. You can't tell an engineer much, is the saying

Good luck to you sir, you need no help from what I see.

Now that was simply unfair. Your criticism was that I should rely on the board to tell me which engine is suitable based on my chosen aircraft. However I'm telling you my aircraft is a one-off, so if anyone is going to discover a prop-sizing issue (as you mentioned), it is likely to be me. How is that arrogant?

You are missing the point here.. People dont build planes that will handle 50-100 cc engines... That is a huge difference in performance and weight.

How big is the plane.. whats it going to weigh?

You are the one who is being vague... and I pointed out several engines that you didn't list which is exactly what Silver is talking about.

amaurer,

It wasn't unfair (to me, anyway and I am an engineer as well), it was based on your extremely vague question and nasty responses to some pretty reasonable answers. You should know that if you want a specific answer, you must ask a specific question. Some of the people on this forum have thousands of hours operating R/C aircraft and you WILL find the answer you need. You don't give the aircraft size, weight, mission envelope, your piloting experience, expectations or goals and you ask about a range of engines that will fly aircraft from 13lb up to full scale ultralights. It is rather hard to provide an intelligent answer to a question that vague. Be specific and you will get specific answers.


Mark

The 3W-80 weighs .6lbs more than the 3W-50: that's 70% more HP for only 13% more weight. Your post is a brilliant example of the kind of wisdom that having a single repository for the facts alleviates.

My aircraft is more than 100lbs; I'm using two of whatever engine I choose. It will fly fine with engines in the 50cc range, however at this scale using a larger engine adds negligible weight so it will certainly also fly fine (better) with 100cc+ engines.

I realize this is unconventional, but I'm certain that there is enough information here to prompt a valuable exchange of ideas. Of course, all I asked for was prop and RPM data, but hell...



Mark,

I don't see how I was vague. I asked for prop and RPM data for a specific list of engines. At no time did I ask for estimations of performance based on my (admittedly) vague application, or for any other information that required knowledge of my end-use. The responses I got suggested that it was either impossible to choose an engine in this way (which is untrue) or that I was not qualified to do so (also untrue). I'll start a thread later to satisfy curiousity, if thats what this is, but for the time being all I wanted was engine data.

Jeeesh, guys - give this poor guy a break. he asked a simple, albeit incomplete, question.

Zenoah G-62, 6700 rpm, Biela 20x10 3-blade prop, 90 degrees, 300 feet.
DA-50R, 6900 rpm, Menz 23x8 2-blade prop, 3 degit temps and 300 feet.

there, that was easy. don't know what good it is, but it was easy

OK
G62, 22-10 DynaThrust 7400
MSC 22-10, 6400
MenzS 24-8, 6700
No muffler

Without trying to be rude, for I am not, I had already presumed from the spreadsheet that "engineering" was a factor. Nor am I trying to avoid providing you with an answer. It just seems to me that not having a "target" makes a selection or comparison difficult if not impossible. Whether that targer be in price, weight, usable rpm, thrust, propeller size, r whatever. There needs to be a goal rather than a blanket information to fill the cells of a spreadsheet.

Unfortunately I'm not currently aware of any publically available information that accurately defines any of the parameters you require other than prices and weights, and the vast majority of those can be had directly from the manufacturer. Just make sure that the manufacturer includes all the required parts to run the engine other than an ignition battery, switch, and propeller. Muffler and propeller weights have such dramatic weight differences that they can significantly skew the final ready to run weights of an engine, as can the ignition battery.

Performance criteria can also be significantly skewed, especially in rpm line items, by selecting a propeller that's lighter as well as less rigid than another and less efficient, thereby generating higher rpm at lower thrust levels. A perfect example would be comparing the rpm differences between say a Zinger 22-8 and a Mejzlik 22-8. Though both may be in a similar rpm range, the Mejzlik would provide greater performance.

Another factor would be in carb tuning where there is considerable room for performance gains and losses due to the experience level and ability of the engine owner to correctly set the needles for the propeller, atmospheric conditions, muffler choice, and oil ratios used. You can take any one given engine and make what appear to be minor changes to an area and end up with dramatic changes in the apparent performance of the engine. I don't know of anybody that has compiled an engine data sheet that denotes true rpm/thrust/propeller charts for us to make comparisons with. For an accurate graph it would have to be developed by knowledgable people in a controlled and well monitored enviornment.

Although I admit that I don't want to expend the time, expense, and effort required to make determinations on a tremendous number of engines, without a what, where, and why it becomes even more difficult to perfrom the tasks requested. As for the mention on engines not listed that may be better choices, there just is not that much empirical data for any of the engine types to be explained in depth. A good "for instance" is the line of Taurus engines. I just paced an order for one of the 52cc engines because I know they are of better construction than many, generally turn higher rpm and thrust numbers than many, and run smoother due to their internal design. Their failure rate for design and construction reasons are virtually non-existant, but they are also a bit more expensive so many would quickly turn away because they are not "cheap". I "know" this to be true, but substantiating this for everyone would require that I spend all my free time performing numerous tests and I would not get any flying done. Where's my benefit in that?

Do I and others appear to be reluctant to get into this? It's not becaue I don't want to, it just seems to me to be a very large expenditure of time for little return or gain. Nothing rude or personal I assure you. There are just too many factor involved that would effect the comparison chart, and some of those would include design parameters of the aircraft itself. Front or rear engine, desired flight envelope, Cp, Cl, and Cg, to name just a select few.

...

Never mind the rest...

Try looking in the Tachometer Forum for test data for the various engines.

The ThrustHP calculator is wildly optimistic about how much thrust is produced. pe reivers posted a calculator a while back that is much more accurate, based on test data I have compared it to. PM him and see if you can get a copy for much better prediction ability before you buy.

Mark

Test elevations all between 400 and 1500' msl.

Airframes: W/H 28% Extra and Edge, Weights deliberately varied from 17 to 21 lbs. W/H 29% Ultimate, weight: 18lb. 9 oz.
Brison 3.2, MSC 22-8 prop, Bisson down draft muffler/diverter- 6700-6800rpm
Mejzlik 22-8: 7300
Zinger 22-8: 7450
Zinger 22-10: 7250
Menz "S" 22-8: 72-7300
Biela 22-8: 7000

Best 3D performance of props used: MSC 22-8
A pair of these could easily handle a 100 lb.plane, then again, so could a pair of 35cc engines if length of t/o roll and performance envelope where not major considerations.

Brison 6.4, 105cc, Bisson rear angled mufflers, Airframes: 35% Giles 202 and 35% Sukhoi. Aircraft weights: 26 lbs, +/- 1/2 lb.
MSC 26-10: 57-5800 rpm
Menz "S" 27-10: 61-6200
Mejzlik 27-10: 6050-6150
Biela 28-10: 6100
Fuchs 27-10: same as Mejzlik 27-10

Best climb performance of props used: Biela 28-10

BME 115, stock mufflers.
I haven't seen rpm counts of less than 6600 rpm with any 27-10 prop to date. Some much higher.

Taurus 3.2 info when I get around to logging some of it.

It is hard to find Scientific data on a particular engines output without an accurate measure of torque and rpm. The typical modelers method ranges from inaccurate to subjective. The only engines on your list that I would avoid are any single over 80cc for vibration, the small 3W and cheap engines in general for their excessive weight. All of the now less popular Sachs based engines such as Brison, Fox, and Taurus are still very good performers, and have more accessible carbs. For extreme value there is no beating that ebay G62. Good luck!

Not knowing the mission your plane is intended for, and weighing 100lbs (as you have stated) I would go with nothing less than two 100cc engines. You did mention twin??
Now your choices, by my minimum standard, would be 3W 106 or BME 115. Flip a coin If you are not well versed in gas engines maybe try a DA100. They are a little more forgiving for a newbie.

BME 115 new Mejz 28x10-6650+ (stock muffler) Both weigh the same as the 80cc engines you have mentioned
BME 110 new Mejz 28x10-6400+ (stock muffler)
The BME 110 is no longer in production.

If you want the most accurate thrust/hp calculator going, find the one Pe Rivers has made. Nothing comes close to it, and it is made in a spread sheet format. Free Too

Truthfully, under the right conditions a pair of 50cc engines set up and propped correctly will handle the 100lbs and then some. It all depends entirely on how the aircraft is to be flown, and the type of departure and arrival with terra firma. I used the term aircraft instead of airplane deliberately to allow for extreme differences in flight profiles. I have this strange and unsubstantiated feeling that the need for information will not be used for what most of us consider to be a normal flying platform or profile. I'm thinking either aeronautical competition or UAV development. If someone was to have the thousands of feet of available runway like they do at Moffett then small engines and high weights aren't much of a factor.

From my experience of pulling draggy loads with heavy airplanes, I would steer away from any single cylinder larger than 50 cc because the vibration levels are high enough that it is tough on the airframe over an extended period of time. The 3w-106 has been giving me fits with losing the prop and hub until the single bolt-Ralph fix occurred. I would steer away from that engine also. I would suggest the older 3w-100, the DA 100 or the 3w-85 which are all twins. I personally had overheating problems and related component failure problems with ZDZ engines. I have not had any experience with other brands of engines.

Hope this helps. If you want additional details, send me a PM


Elson

Now if you are looking for something a little different I can connect you with someone making a 107cc inline twin. Depending on the set up, centerline thrust, or wing mounted there could be some nice drag benefits, especially where a critical engine application was to be encountered. See why I noted that the task/target would be helpful?