Yak13

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Anybody has experience with this engine? The manual states a top RPM of 21,600! I'm thinking of using for a ballistic pattern ATLAS (intended to be very fast). Need info on real numbers 10-12" props. The engine looks awesome with a top HP @ 18000 rpm, but the plane might be too big to use those RPM.

Thanks

TFF

Just advertising numbers to claim the high HP. Real life will be a prop that will spin it about 15,000 for a ballistic. I knew someone with a Jett 91 running a 10x10; the engine screamed but it seemed slow for all that noise.

MJD

My Feedback: (1)

How fast do you want to go? Classic "ballistic" pattern planes were quick, yeah, but not insanely fast. That's a big ol' airframe to pull with smaller props. If I wanted to go fast with a strong .60 size engine on an aerobatic bird, I'd put it in a classic .40 size pattern airframe with a thinned airfoil.

The type of props a sport/pattern timed .60 will spin in the 18-21k range are 10-6, 10-7, 9-9, 9-10, that sort of thing, and IMHO they will do little for a .60 pattern airframe. An 11" prop low enough in pitch to let the engine spin up there would be great for a class D free flight but will do little for the Atlas except give you killer vertical lines.

That engine ought to do a good job but I think you will need to swing an 11" prop to get anywhere. I'd guess in the range of 11-7 to 11-8, and set up the pipe accordingly. If the powerband is fattest up in the high teens you'll probably do better spinning there with moderate pitch than lugging it down with a high pitch prop.



The cited example of a Jett .91 and 10x10 prop (which that engine can spin in the 15.5-16k range) was probably on too big/draggy an airframe. It will pull the right airframe like stink, but too big an airframe and like TFF says, it will make a lot of noise while it wastes HP spinning 10" pitch prop blades at very wasteful angles of attack. That's a combo for aircraft that can move 150mph+ on that much horsepower.

Yak13

My Feedback: (17)

Thanks MJD.

I understand the limitations of these engines, but wanted an opinion regarding if it was worth putting the R75 on the Atlas. I have some other options to make it go fast, including an OPS 60 FIRE, a Novarossi 61 FIRE and even a Tower .75 or a Rossi .81 FIRE (which I'd rather use on a speed plane). Right now it has an OS 61 FSR w/pipe, 11x11 prop spinning at 11,400 static. It delivers around 130 mph. But IMHO a little more speed makes the old pattern planes incredibly fun, even if they lose some of their pattern potential.

I am now flying more sport, with my 9-yr old son, and he LOVES to do speed passes and gigantic loops with MY Atlas & Arrow.

MJD

My Feedback: (1)

You may get more speed out of it with the Novarossi, but I'm just saying you'll need to get it up in the powerband and prop accordingly. More speed = more horsepower combined with the right transmission ratio (prop pitch and dia). I can't say what kind of power the Novarossi makes down in the 11-12-13k range, but if it is indeed timed for 18k peak, less pitch/more rpm might be the answer.

Sorry, this is not an answer with hard numbers, just an opinion based on the type of engine I think it is (aggressive sport timing).

OPS .60 FIRE - my favorite >2.5cc glow engine, I have three..

On the other end of the spectrum, I fly an OPS Speed .65 (ducted fan timing) on 8.25" diameter props - you wouldn't believe how little static thrust they produce, barely 5 pounds, and I doubt it could get a pattern model off the ground. But on a small, clean airframe.. yeehah!

Sounds like your son has fun.. not all 9 year olds get to fly 130mph pattern planes. One of the better video games out there.

Yak13

My Feedback: (17)

Oh, he has serious fun. And it is one of the better video games out there. Except that the "GAME OVER" doesn't have a reset button.

Yak13

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Proof of kid having fun:

http://www.capturemyarizona.com/photos/917121

MJD

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Great photo! Nice looking model too.

Warbird40

My Feedback: (24)

My Rossi 45 turned 15,000 with a 10x7 and they claim 16-16,500 which should be achievable with a 9" prop, but 21,000 seems unrealistic....they are however sweet sounding and powerfull. You should see maybe 18,000 or slightly more with the right prop.

MJD

My Feedback: (1)

??.. he could see 21,000rpm with the right prop. 21k is perfectly realistic, but the issue is what prop this .75 might spin at those rpm. It will not spin an 11" prop that fast, maybe a low pitch 10" prop (at risk of shedding the blades if it is an off the shelf molded APC or the like), or a 9" prop with some pitch. Ducted fan .60 - .90 engines spin 9" props happily up in that range and beyond without a whimper. But these prop sizes are useless for large aircraft, they need more disc area (prop dia).

Novarossi "rating" this .75 at up to 21,600rpm simply means "we at Novarossi are confident in the engine mechanics up to that rpm". Little else, since they also note peak power at 18k.

WB40 - when you say "they claim 16-16,500", what does that mean? They rate it for peak power in that range? If so that is useful information for prop choice, and that fact you are propping it about 1k less means your are probably near or at peak power in the air.

If the power peak on the .75 is at 18k then it is pointless to prop it above that figure. Since a horsepower curve falls off on either side of peak, if you are not propping it for peak power in the air, then prop it below peak with more prop load, rather than above peak with less.

For this application, for top speed I'd work with 11" props that it will spin north of 15k on the ground. Again, pipe setup is important.

aspeed

A high pitch prop will unload a few thousand rpm in the air too, so 15,000 on the ground would be a good start, and if it gets on the pipe in a dive and stays on, then that is where you want to be for pipe length/prop sizeand pitch.

Warbird40

My Feedback: (24)

Well I changed from a 10x7 APC to a MA 11x5 due to the fact that the Tiger was landing too hot so I had to kill the engine about 25-30 short of the runway to slow it down. With the 11x5 I haven't tached it, but it sure seems to be screaming louder in the air!

Yak13

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Installed and flew the old Atlas with the NovaR .75. What a difference from the OS61!!!

Warbird40

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Great numbers Ed! I am very happy with my Rossi R45. I just got a used Rossi R60 (just have to find an airframe for it)

Yak13

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Warbird, is the R60 the rear exhaust?

Warbird40

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No its actually a very unique, custom LEFT side exhaust! Someone went thru a lot of trouble in switching in from right side to left side. I think I have the only one ever with that set up.....its a screamer!

Yak13

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Just back from some testing and awesome flying in 25 mph wind.

I installed an OS 7D carb with no intake reduction (10.5mm throat) on the NR75. Flew it with an APC 11x11 (spinning @ 12850 static). Flew very impressive.Later tried an APC 11x12 (12350 static). Flew like a beast! Forgot to take the Eagletree, but wil fly and record official data later this week.

The beauty of this is conserving the pattern characteristics of the big Atlas and amplifying everything flying close to 150 mph.

turbo.gst

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That sounds awesome!

airraptor

My Feedback: (66)

No not always as some "high" pitched props will lose rpm in the air if not matched to the airframe.


If I was going for max speed level i would go with the largest CC engine for the same weight as most of the 60-75 engines out there. This is where the OS 95 AX comes in. run this engine with a Jett Red pipe for the 90's with a 11x13 prop. I bet the Rossi engines are heavy.


Also MJD is correct on all his posts.

Yak13

My Feedback: (17)

I'll have some hard data soon, but the Novarossi 75 is defintely getting on the pipe on every shallow dive, and staying there. The 95 AX I haven't tried and maybe with the 11x13 will give good results. BUT...
I can't imagine myself pulling the NR 75 out to put in an OS. Any OS. The 75 is just too nice an engine, too much of an attention grabber and an excellent performer with a full pipe.
I will experiment with a rare APC 11x14 I have here with me too. Maybe too heavy but nothing is lost by adding some length to the pipe and trying it.
Let's see what the numbers say.
Thanks all for your comments.
Ed

airraptor

My Feedback: (66)

just so you know i ran the 11x14 on a OS 120 with stock muffler and recored 11,500 with it. the same engine turned a 16x8 at 8,600 on stock muffler

Yak13

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Thanks Airraptor.
Let's see how the 75 performs with the 11x14

iskandar taib

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Get a Q500 airframe, stick it in front of that. It'd probably need some tailweight. Check APC's site for a suitable carbon fiber prop - that's what you'd need to turn that fast without shedding blades. (Or a wood prop, believe it or not..). You might have to go down to 9 inches to get it to turn 18K - see what sort of props the pylon racing pilots use on .40s!

Iskandar

airraptor

My Feedback: (66)

have you ever flow a fast plane and have you ever flown a Q-500 plane heck have you even seen one before??

you wil need a new fuselage made to fit that engine. That engine is heavy also so would be as fast as the normal set up for a Q-500 and would be hard to land and fly if not break.

iskandar taib

My Feedback: (5)

Of course I've seen one. What a silly question. They bring dozens to the Nats every year. I've even sat in a cage under the pylon, counting cuts.

They use radial mounts on the firewall, engine hangs out in the breeze, you should be able to fit one of these on there, no problem. Balance would be a problem, you'd need some tailweight to balance the model. With 500 square inches, I think it'd carry the weight just fine. And they're immensely strong, so I don't think you'd risk folding the wing or anything like that.

Iskandar