Hello was hopping if someone can tell me if this is right. I bought two engines off a guy that said I was buying two Rossi R40 Aereos for $60 but I didn't fire them up until now. I was reading what the rpm are to show with an APC 10X6 and they say that I should be getting 17000 but when I turned this engine on they are hitting around 25500rpm. The sides don't say what size they are and it has a gray head on it.I'm scared that I will blow the engine with these reading. What I would like to Know is if the guy that sold me these engines knew what he had or am I doing something wrong. Second I bought these engines for a trainer because I got two for $60, I didn't buy the os46FX did I make a mistake.

Just a wild guess for what it's worth, there are no .40 sized engines on this planet that will turn a 10X6 APC 25,500.

I would say your tach is malfunctioning, or you are running a 3 blade prop with your tach set on 2 blade.

Something is up since 17,000/.6666=25,500 seems like a coincidence....and then again there are no .40 sized engines on the planet that will turn a 10X6 3-blade 17, 000. So back to the malfunctioning tach.

I'd go ahead and run it knowing that if your prop is a 10X6 it won't over-rev...17000 is a pretty good speed for a 10X6 on a .40 if this is what it is really turning I'd be a little surprised.

It will be fine for a trainer...your transmitter should have a stick to control the throttle, that will be what you will need to learn to use.

Tested the tech on my friends engines, and on the MDS 40 it reads 12000 and his 0s 40 la reads 12500. The tech it set for 2 blade, I'm using a 2 blade. Then put back the Rossies and it said the same thing 25000 to 25500RPM's steady (screaming very loud) This engine is not much bigger then a 40 size.

Well then I would put them on Ebay.

A .40 that will turn a 10X6 APC @ 25,500 should be worth several hundred dollars, maybe thousands. There has never been one in the history of the world..two of them would be quite a treat!

Of course you know I'm kidding with you. But even if they were Rossi .60's and were mistaken for .40's they won't turn 25,500 with a 10X6..trust me.

It would be a stretch for the most powerful .90 sized ducted fan engine running on a tuned pipe to get even CLOSE to 25,500..

So whatever you have, rest assured it is not turning a 10X6 APC at 25,500.

Have fun

Now that's interesting. Another thread on Rossis led me to their web page (thanks for the link Chuck ) where they claim the R40 Aero puts out 1.9HP at 17K revs. I happen to have a chart for various props and it shows that the APC 10x6 needs 1.88HP to drive it at 17K revs, virtually exactly the same as apapa is getting. A manufacturer that's honest with their HP ratings?? Just for interest's sake, that prop needs just over 6.3HP for 25,500rpm.

The MDS40 is developing .66HP and the LA .75HP

Apapa,

If we chose to believe the Rossi claim, of 1.9 HP @ 17,000 RPM and it would do it spinning an APC 10x6. Well, turning the same prop at 25,500 RPM will require over 6.4 HP, IF we don't talk about compressibility...
Your blade tips are doing 339 m/s; almost Mach 1. Some places on your prop blade profile are going supersonic. That will require even more HP.

Sell them on Ebay... But tach them again with another, different tachometer.

Sincerely

Let me guess: You're taching the Rossi engines at home using an AC powered light source, but you met your friend at the flying field to test your tach against his engines.

Hold your tach up to a light in your house. It will read 3600. I don't remember all the mathematics involved, but I am pretty sure that the spinning prop and flashing light will combine to give you weird results.

Use only DC light sources, such as a flashlight, or natural sunlight.

If the engines were really turning 25,500 RPM, you wouldn't be here to make the claim, IMHO. The engine would've exploded and killed you while you were taking the readings.

The only other possibility is that the RPMs are out of your tachometer's range.

Just because his readings seem unbelievably high, doesn't mean they are impossible.

I own an ASP .40 which throws a Master Airscrew 10X6 up to 22,500 RPM in sunlight. The same tach measured my friend's Webra .91 at 17000, and SuperTiger .61 at 16,500. All props were 2 blade, with the tach set to 2 blade. Another tach has since confirmed my readings.

Numerous calibration tests with an AC lightbulb have always read 3600 "RPM" (proper reading).

Thrust HP claims this would require 4.88 HP. I have often heard that ThrustHP doesn't match real-world results. At higher RPM's, the prop blades are traveling through the turbulent air created by the previous blade(s). This results in lower resistance to the blade than non-turbulent air. Perhaps ThrustHP doesn't take this into consideration... I am no aerodynamic engineer, so I can't explain it further.

I am at a loss to explain WHY my engine (and apapa's) reach such high RPM's. I only know that my ASP .40 has considerably more power than my Magnum XL .40 with the same prop.

American house current at 60 cycles per second multiplied times 60 seconds per minute gives 3600 cycles per minute.

Now, why doesn't the tach see that as 3600 prop tips passing by per minute divided by at 2 tips passing for each prop revolution to give 1800 revolutions per minute? Gosh I love math -- if only the numbers would make sense once in a while!

Because the light bulb pulses for both sides of the AC curve (positive and negative). I.E. - the light bulb pulses at 120Hz.

120Hz X 60 seconds = 7200 pulses per minute.
tach on 2 blade setting reads pulses per minute / 2
7200 / 2 = 3600 "RPM" reading.

Strato,

Master Airscrew said the maximum safe RPM for their glow G/F props to 160,000/diameter, so a 10" prop is limited to 16,000 RPM; see:

http://www.masterairscrew.com/techbull.asp#C

By all likelihood, at 22,500 RPM, this prop could potentially throw a blade. No one could say it is safe. APC has a 19,000 RPM limit on the same prop size:

http://www.apcprop.com

Two engines made on the same production line, in a CNC process, cannot differ so much from one another. The range of RPM demonstrated on the same prop, can be no more than 300 RPM; between the weakest engine and the strongest.

Making 3.3 TIMES the rated, run-of-the-mill horsepower, is not within the remotest scope. It is like finding a 20' tall man...

Not even a quirk can explain this.

Sincerely,

I said I couldn't explain it - Just reporting my results. Never threw a blade either. I have since replaced the 10X6 with an 11X6 with good power (no tach readings yet).

Where did you see me say the two engines were made on the same production line? One is an ASP (12 years old), the other is a Magnum (2 years old). Both with factory equipment (no mods or tuned pipes). Although I've never seen another ASP .40, other ASP owners I've met have reported extreme pleasure with their engines (.61, .91, 1.20 size).

I told a friend of mine at the Field that I go flying about these engines and he's bringing this tech to see if mine is given the wrong readings. He said that the readings that I'm getting is for a R40 Pylon engine, so I looked up that engine and mine does not look like that one but it is an older engine. I'll let you guys know what the readings are. Thanks for all the remarks guys.

Thank you ... It had to be simple, but it wasn't coming to me.

That means it can't even meet the manufacturer's stated maximum RPM's ?!?!?! :stupid: Imagine if I threw a 12 X 4 on it...

The max practical RPM rating of the current batch of ASP engines is 17,500 (click here).

I've ran so many engines over the years I can't count them. While not saying your claim is false, I find it extremely unlikely that an ASP .40 could turn a MA 10X6 at these RPM.

Jett makes some of the finest engines on the planet. His FIRE 50 is advertised to spin an APC 10X 6 at 17~18K. He verifies this before he ships one. For an ASP to beat a Jett FIRE 50 by 4.5K (albeit on a different brand of 10X6) is astonishing.

You ASP also bests the Jett .60L by 4K on a 10X6 (again an APC).

Then again you are out performing basically every other engine on the Jett website, so I guess I shouldn't be surprised.

I'm running a fairly well modified Rossi RIRE .65 with an APC 9X8 and only get 21K. In my experience the 9X8 and 10X6 are fairly close to each other as far as RPM. For an APC 40 to out-turn what is basically a Rossi .65 fan engine on a pipe by 1500 RPM is just simply amazing.

I run a pair of modified OS 46 VF engines with 9X8 APCs and they both turn about 17~17.4K on pipes. This is an extremely good number for an OS 46VF. Again, hearing that an ASP 40 is more powerful by an estimated 5K is just incredible. I worked these engines over to get a measley 1.2K gain, to see 5K more would be a feat beyond imagination.

And I do own an ASP .46 on a pipe...mine is not a particularly powerful engine.

I tested the engines today with another tech and got the same reading. My buddy said that this is not a R40 Aereos it is an older engine and it might be a Q500. hes never saw anything like that so he offered to buy the other engine off me for $60. I told him I will let him know I first have to talk to you guys about how much. here are some pictures of the engine so maybe you can tell me what they are.

another picture

another picture

Looks just like any Rossi .40, and it is not old..at least the carb is the new style.

A pic from the Rossi website



Yours has the older style muffler.

I find it amazing that you can get 25.500 out of a front intake, side exhaust engine with such a small bore carb and a stock un-tuned muffler. Every other Rossi .40 on the planet would have to run with nothing but the spinner to get those numbers..and it would have to be a smaller spinner than the one you are running at that.

Which brings on an even more incredible feat. That you are able to run a plastic spinner at 25,500 and not grenade it. Of course I would like to point out that your plastic spinner is more than likely the only plastic spinner in history that has not flown apart at 25,500, but then you probably knew that.

An interesting side note..your tip speed is about 758 mph.

At STP this is roughly .99 Mach.

You guys up in Canada are sure getting a LOT better engines
than we are down here!

I also see in your pics that you have it in the garage..under lights.

It must be the cleaner, colder air...

Chuck - If a spinner is properly balanced, why should it explode at 25,500? Mine withstands 22,500 (although I reduced it to 20,000 before flight by running it a bit rich)

As for the lighting, I have previously stated my RPM's were measured in sunlight....

apapa - since you've confirmed the readings with another tach, you can get more than $60 for it... I've been offered $150 for mine a year ago.

I really don't have much to add...the centrifugal force at 22,500 or 25,500 is great enough to overcome the strength of the plastic, so they just fly apart.

The fact that neither of you guys is shucking spinners should add another hint to the equation, but as you are both convinced of your engines performance I will now bow out of this discussion.

Good luck to you both.

Chuck - I hope you didn't feel like we were attacking your statements. I for one was dumbfounded the first time I had tach'ed my engine.

I ran it for 8 years before I ever bought a tach. I was wondering why I couldn't get as much power from my new Magnum. When the Magnum tach'ed at 15,500, I turned to the ASP for comparison... Imagine my surprise. I then checked my friend's, and it read 15,200. He doesn't own a tach, so I waited till I could borrow one to validate my #'s. 4 different days, 2 different tachs, 2 different props (both MA 10X6), always peaked around 22,000.

I can understand the hesitance to believe my readings, but my own disbelief has caused me to verify them a few times. I don't mention the RPM's often because it always results in discussions like this where the naysayers say it can't be. I just live with the fact that it runs great, and "don't look a gift horse in the mouth".

If you're ever in Winnipeg, let me know and I'll let you measure it with your own tach.

BTW - any physicist will tell you there is no such thing as centrifugal force. What you're refering to is inertia applied to an object kept on an angular path by centrepital force.

Strato, Irrespective of centrifugal force being non existent in the theoretical sense, you cannot deny the fact that having a monster spinner on your engine does not get affected by it's on inertia, and in my expericence with plastic spinners some form of deformation.

Sorry, but I agree with chuck on this one, I've been playing with engines a LONG time, and even our pylon motors would be hard pressed to clock over 21.

Here's a tip, record it's sound and by using a pitch tach, see what you get. You might be suprised!

I don't know where to borrow a pitch tach from, but I'm not about to go out and buy one. I can tell you that my ear tells me it has a noticably higher pitch than anyone else at the field. Next time I run it, I'll take a tape recorder with me, and post it here.

P.S. My spinner is much smaller than the one pictured above. 1 1/2 inch I think.