Club FOX!
05-01-2014, 10:22 AM
#3452
I agree with all of that. I saw a video a couple of years ago of a giant scale biplane with (I believe) four electric motors rigged to a gear drive. The prop howl when it flew made it sound just like it had an engine.
The intake noise, especially on a two stroke engine, is much louder than most people realize. If you remove the air filters and cap off the exhaust momentarily on for example a motorcycle engine while it is running, you would be amazed at exactly how much noise the intake can make. Lower performance engines have an intake port design that somewhat lowers the noise by opening the port gradually but the intake is still noisy.
Years ago when they started trying to control noise on pattern planes, the answer was to use more pitch to lower the rpms, use soft mounts, air filters, etc. Larger props, (in diameter) many times aren't less noisy because then the tips can go supersonic. More pitch is the answer, but that would be against the current popular 3D flying requirements.
AV8TOR
The intake noise, especially on a two stroke engine, is much louder than most people realize. If you remove the air filters and cap off the exhaust momentarily on for example a motorcycle engine while it is running, you would be amazed at exactly how much noise the intake can make. Lower performance engines have an intake port design that somewhat lowers the noise by opening the port gradually but the intake is still noisy.
Years ago when they started trying to control noise on pattern planes, the answer was to use more pitch to lower the rpms, use soft mounts, air filters, etc. Larger props, (in diameter) many times aren't less noisy because then the tips can go supersonic. More pitch is the answer, but that would be against the current popular 3D flying requirements.
AV8TOR
05-01-2014, 10:41 AM
#3453
Well we did used to fly the pattern planes with large high pitched props and special tuned pipes with silencer chambers built in just so they could reduce the noise. I still have props in the odd sizes like that 11x10, 11x11, 11x12 and 12x10, 12x11, 12x12, 12x13. If you play around with the long lower RPM tuned pipes on a Fox .60 Schnuerle engine you can get it to turn the same big high pitched props at about the same RPMs that the classic OS Hanno .61 pattern engine did too. I was testing out a Fox Eagle III rear exhaust engine this last weekend with different configurations and a Hanno pipe even for someone wanting to do some classic pattern flying to see which prop combo was going to work good. Heck they have similar high pitched props for the four stroke 1.20 engines too.
05-01-2014, 02:32 PM
#3454
I've used 12x10, 12x11, 13x10, and 13x12 APC props on my Enya R120-4C for speed but at the expense of a major absence of thrust. I had to step down to a 13x7 or 13x8 to get some thrust back. If I had this engine in a plane the props would work perfectly fine. Regardless of the prop, the prop noise is horrendous. It's hard to hear the intake noise on the 4-strokes.
Based on APC's rotational limits, many props would be grossly over spun if the tips were spinning at supersonic speeds. MA props have a lower rotational limit yet, so supersonic tip speeds would be quite dangerous if someone was gutsy enough to turn them that fast.
IIRC the rotational limit for APC is 190,000/Prop Dia. and MA's rotational limit is 170,000/Prop Dia.
Based on APC's rotational limits, many props would be grossly over spun if the tips were spinning at supersonic speeds. MA props have a lower rotational limit yet, so supersonic tip speeds would be quite dangerous if someone was gutsy enough to turn them that fast.
IIRC the rotational limit for APC is 190,000/Prop Dia. and MA's rotational limit is 170,000/Prop Dia.
05-01-2014, 06:33 PM
#3455
Yes the APC 12 inch props have a max speed of about 12,400 RPMs which is around mach 0.6, that is where they get real noisy.
The Hanno .60 engine with the Hanno pipe was tuned to turn the 12x11, 12x12 size props at lower RPMs of around 9,600 to 9,700 RPMs.
I actually have a Fox Eagle III rear exhaust .60 engine that can turn a APC 12x11 prop at about 10,500 RPMs, using the Hanno pipe even. But with a fuel pump and Cline regulator it ought to hold the peak RPMs even better. The Hanno engine used a special, just for that engine, OS three needle pump carb and fuel pump.
The Hanno .60 engine with the Hanno pipe was tuned to turn the 12x11, 12x12 size props at lower RPMs of around 9,600 to 9,700 RPMs.
I actually have a Fox Eagle III rear exhaust .60 engine that can turn a APC 12x11 prop at about 10,500 RPMs, using the Hanno pipe even. But with a fuel pump and Cline regulator it ought to hold the peak RPMs even better. The Hanno engine used a special, just for that engine, OS three needle pump carb and fuel pump.
05-03-2014, 05:43 AM
#3458
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I got a notice from R/C Universe that Broken Wing had posted a sale bulletin from Fox. All the usual stuff was there with one big exception, Fox now has a .50 gasoline engine. They sneaked this one in on us didn't they. But having known Duke for years, he was pretty good at doing that too, looks like he passed it on down.
05-03-2014, 06:06 AM
#3459
I got a notice from R/C Universe that Broken Wing had posted a sale bulletin from Fox. All the usual stuff was there with one big exception, Fox now has a .50 gasoline engine. They sneaked this one in on us didn't they. But having known Duke for years, he was pretty good at doing that too, looks like he passed it on down.
05-03-2014, 10:55 AM
#3460
05-03-2014, 11:17 AM
#3461
I don't know if they ever really released the .50 gas engine or not to anyone. No one has posted any information about their experiences with it yet. So I don't think they shipped it to anyone. I think that someone would have posted something about the engine if they did release it. Fox's website is not updated very often. I think the sale has been going on like that for a few years now. You really need to call them to ask about buying a engine or something.
05-03-2014, 11:29 AM
#3462
I don't know if they ever really released the .50 gas engine or not to anyone. No one has posted any information about their experiences with it yet. So I don't think they shipped it to anyone. I think that someone would have posted something about the engine if they did release it. Fox's website is not updated very often. I think the sale has been going on like that for a few years now. You really need to call them to ask about buying a engine or something.
NEW FOX .50 Gas (12cc) Engine. It was $399 on sale for $275... I would think they've shipped if they're having a sale on them?
Last edited by Broken Wings; 05-03-2014 at 11:36 AM.
05-03-2014, 02:24 PM
#3463
05-03-2014, 05:05 PM
#3464
I was going to ask what year. I saw previously that they have halted production "temporarily" because of tough competition from China. Don't know how temporary that is, a month or three, or year or three. It was only a couple of months or so ago that I read it. I didn't pay too much attention because I only use the one Fox .15 BB, and all the rest just sit.
05-04-2014, 03:26 AM
#3467
05-05-2014, 09:52 AM
#3469
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It has been reported elsewhere that Fox is getting out of the model airplane engine business. This is not true, I just talked to Sharon, they have taken a hiatus from mfg them to concentrate on their real business and will resume engine mfg at some point. They are currently out of engines.
05-05-2014, 11:06 AM
#3471
I wonder why Sharon never returned my calls when I was looking for head shims for my Fox twin. My buddy and I decided to make our own. Oh well. Glad to hear they will make more engines sometime.
05-13-2014, 09:03 AM
#3472
Well we did used to fly the pattern planes with large high pitched props and special tuned pipes with silencer chambers built in just so they could reduce the noise. I still have props in the odd sizes like that 11x10, 11x11, 11x12 and 12x10, 12x11, 12x12, 12x13. If you play around with the long lower RPM tuned pipes on a Fox .60 Schnuerle engine you can get it to turn the same big high pitched props at about the same RPMs that the classic OS Hanno .61 pattern engine did too. I was testing out a Fox Eagle III rear exhaust engine this last weekend with different configurations and a Hanno pipe even for someone wanting to do some classic pattern flying to see which prop combo was going to work good. Heck they have similar high pitched props for the four stroke 1.20 engines too.
05-13-2014, 09:27 AM
#3473
06-16-2014, 07:26 AM
#3474
Finally got a test stand put together to test run the big Fox twin. I could have used the crate I normally clamp my regular test stand to but I felt I needed something better looking. This is what I came up with using scraps of wood from work. Hickory and South American Andiroba. I used neoprene tubing from the clunk fitting on the tank to the Carburetors due to the butterfly carbs' non-barbed fittings. Throttle operation is controlled by a Master Airscrew 6x3.5 prop I bought and had no use for. Hoping to run the engine soon.
06-16-2014, 10:23 AM
#3475
Finally got a test stand put together to test run the big Fox twin. I could have used the crate I normally clamp my regular test stand to but I felt I needed something better looking. This is what I came up with using scraps of wood from work. Hickory and South American Andiroba. I used neoprene tubing from the clunk fitting on the tank to the Carburetors due to the butterfly carbs' non-barbed fittings. Throttle operation is controlled by a Master Airscrew 6x3.5 prop I bought and had no use for. Hoping to run the engine soon.