Charley

My Feedback: (2)

What I believe about the Eagle series of engines is that they were never intended to be high-revvers, but boy did the have mid-rpm torque. I always figured that if I wanted more speed I could go to more pitch.

CR

Sport_Pilot

I recall my Eagle I had about the same power as my K&B but weighed more and was a lot louder. Not as pleasant of an engine as my K&B and STBlue Head, but a lot cheaper. I don't recall how it did on larger props, but Idon't think I was flying anything at the time that would make me want a larger prop.

The Eagle IV seems to be great on both large and small props. I don't own one but have seen others numbers and the prop charts from MAN. I recall it was best on almost all but the very smallest props where the Tower .60 was ahair better.

earlwb

The Eagle I was a crossflow scavenged engine. It had a baffle on the piston. It was not really intended to rev up high and Fox suggested a 11x8 prop for it. It basically was par for the course in power with the other baffled crossflow scavenged .60 engines of its day. Fox actually made and sold the engine from the early 1970's up through the early 1990's. I remember seeing the Eagle I at some hobby shops still in the 1992.

The Hawk .60 was Fox's first Schnuerle engine design done about 1976. He wanted to impress people and I think he did a bang up job in that respect. The engine would run a small prop and rev up high. But it tended to not like big props above a certain size that had it get lugged down too much. Although it could rev up to 22,000 RPMs the prop used was too small to be really practical, so not having it go much over 18,000 RPMS would be better as the torque curve drops off quickly above that RPM range. They changed the molds once of twice as the early engines had a shiny polished crankcase and the later models had a bead blasted darker gray color crankcase. But the engine was too expensive to make and sell so they phased it out eventually in favor of the newer Eagle Schnuerle engines.

The Eagle II Schnuerle engine was Fox's high performance engine at the time. But he quickly made improvements, namely the crankcase in order to make it more stiff with the Eagle III version. He used the parts to make the Fox 1.20 twin engine out of the II and III engines. When he discontinued the twin engine then he came out with the Eagle IV engine. The main limit to RPMs was the crankcase being in multiple sections would flex too much at high RPMs and leakage would result. The other limit is the smaller 15mm diameter crankshaft.

The Eagle IV came out with a larger more stiff and solid one piece crankcase with a removable cylinder and a backplate, so it handled higher RPMS better and it has a broad torque curve so it runs well with smaller props on up to bigger props. The Eagle IV had several improvements along the way. The latest version is pretty solid. Where the old Eagle II and III engines had a 15 mm crankshaft the Eagle IV has a 17mm thick crankshaft so it can breathe better than the older engines can, so it develops more power and RPMs than the older engines.
Thus the Eagle IV is a very versatile engine with the cylinder that can be rotated, plus they have a reverse rotation crank for it too.

Now then the mufflers was a aggravating point for Fox, people wanted free or low cost mufflers. Plus the muffler has to fit in the box with the engine. When Fox made really good mufflers few people bought them as they were expensive. So Fox did like many other engine companies did and just tossed in a cheap muffler into the box with the engine. So the stock OEM mufflers aren't all that good and tend to be more noisy than some other brands. The mufflers also can reduce the engine output by quite a bit too. Putting on a better muffler really lets all the power in the engine loose.

My Fox Eagle IV runs like a Rossi with a good muffler on it.

landeck

My Feedback: (1)

Earl, that is an excellent write up on the history of the Hawk and Eagle Fox engines.While I remembered much of it, you did a nice job of filling in the holes. Thanks.

Bruce

Sport_Pilot

Yes, very good. Man I want to try one. Can't afford to be in the hobby right now. Just fussed at my wife for sending money to the kids when she could have waited a day for the paycheck to come in. Whew! 3 kids in college is tough.

hsukaria

Ouch!! Three kids at the same time? I am bracing for my kids to start college in 3 years. I better do all my buying now before it's too late.

jessiej

Good point about the mufflers, Earl. I still view them as something of an annoyance, while OTOH, I have come to view supressors for firearms as both a hearing protection and relief of annoyance for neighbors, yet we must have an expensive federal losence to own one. Go figure.

jess

earlwb

The Fox Quiet Mufflers are great, they cause very little power loss, almost like using a open exhaust with no muffler on the engine. But you had a muffler that was very quiet. Fox also had a tuned racing muffler on the Fox Quickee 500 engine too (this was popular with the pylon racers of course). But at the time people just were not all that interested in the better mufflers. It was a while later before Nelson sold his tuned mufflers under the Performance Specialties brand, but even his tuned mufflers were not all that popular either. Jett continues the tuned mufflers with their series of Jett mufflers too. Unfortunately they have the same problem with people just not wanting to buy them all that much either. Even Rossi had some cool tuned performance mufflers and they weren't very popular either. I think MVVS has something like a tuned muffler too, but it is based more on the Mousse can type of tuned muffler. But people would invariably go with the cheaper standard muffler as well. Someone in Austrailia made a adjustable tuned muffler that was pretty neat actually. it looked like a extra long tube, but inside it had a baffle that you could slide back and forth to tune it for a particular engine and prop combination. Yup, you guessed it, it wasn't popular either. Full length tuned pipes tend to not be popular as well, but it might be more for the difficulty in tuning a engine to use them more than the cost. Davis Diesel Development had their nice Soundmaster mufflers which are very quiet and only have a modest power loss too. He quit making them too.

So that is why you see substandard mufflers on a engine being sold by everyone. The muffler has to be cheap and included with the engine and it has to fit inside the box too. Plus the engine box can't be very large or no one wants to stock them in the hobby shop either or mailing costs are higher if it is maul order too. So even the hobby shops drive how big a muffler can be too. The mufflers can cause a engine to lose from 1,000 to more than 3,000 RPMs off the top end of a engine. It depends on the muffler design. Years ago it was a easy 500 to 750 RPM gain if you removed the inner baffle from a muffler on some engines. Fox decided to give up on the inner baffle on their cast teardrop shaped mufflers and just leave it off as everyone was taking it off anyway.

Here is a good example of how much a muffler can affect engine performance. The difference is eye opening. MyRossi .60 engine exhibits the same performance and the difference inRPM between the Fox and Rossi is in the variations on the tachometer when making the measurements.
MyFox Eagle IV with the stock OEM muffler that comes with the engine, 11x7 Zinger prop and 5% nitromethane glow fuel (Omega).


Here is the same engine, prop and fuel using a old Performance Specialties Ultrathrust muffler on the engine. I could lean the engine out a little more but it is still being broken in though. So it'll peak out a little over 15,000 RPMs with this muffler on it.



If you get way down to here to read this... I discovered that there were some Performance Specialty mufflers made for the Rossi engines which have the same exhaust opening and screw hole spacing as the Fox Eagle engines. So there is something to look for, so you don't have to make a bridge adapter for it. of course the old Rossi tuned mufflers is another option too. or you can get a tuned pipe header and make a mouuse can muffler.

Cougar429

My Feedback: (3)

As I posted earlier my ONLY complaint with my Fox motors was the much higher noise levels when pitted against comparably sized offerings from other manufacturers. I never had a problem with their less elegant exterior finish and could always count on a powerful, reliable powerplant.

I came up with the adapter for the 50BB on my own but copied Earlwb with the Eagle IV. As I never ran the Eagle with the stock muffler and some carb and pump problems there is no way to compare how much difference in performance the muffler mod created. However, I can pretty much say the 50BB with the OS muffler, (now has the "Powerbox" muffler from one of my OS 55AX motors installed) has the noise level reduced quite a lot. It is now pretty much standard to all of my other 40-55 size 2-strokes in sound level under all conditions with no discernible loss of power.

As for the carb and pump problem, as promised Gary Conley brought the new bits to Toledo and I picked them up today. Carb is installed and I started fitting the pump and new plumbing. If no other distractions I should have that finished this weekend. Once the belly is buttoned up again I will be able to report on how the break in is progressing.

Cougar429

My Feedback: (3)

As I posted earlier my ONLY complaint with my Fox motors was the much higher noise levels when pitted against comparably sized offerings from other manufacturers. I never had a problem with the less elegant exterior finish and could always count on a powerful, reliable engine.

I came up with the adapter for the 50BB on my own but blatantly copied Earlwb with the Eagle IV. As I never ran the Eagle with the stock muffler and some carb and pump problems there is no way to compare how much difference in performance the muffler mod created. However, I can pretty much say the 50BB with the OS muffler, (now has the "Powerbox" muffler from one of my OS 55AX motors installed) has the noise level reduced quite a lot. It is now pretty much standard to all of my other 40-55 size 2-strokes in sound level under all conditions with no discernible loss of power.

As for the carb and pump problem, as promised Gary Conley brought the new bits to Toledo and I picked them up today. Carb is installed and I started fitting the pump and new plumbing. If no other distractions I should have that finished this weekend. Once the belly is buttoned up again I will be able to report on how the break in is progressing.

Cogburn

To quiet down the fox muffler I use a mousse can with a couple of pieces of hose on the end of the fox muffler to adapt it.

The Mousse can with 2 pieces of hose an inch or so long (stuffed inside each other for a bushing) in the end pops right over the end of the fox muffler and another piece of 5/16 fuel hose out the end of the mouse can for exit hose.

I've also seen them with lawn mower mufflers adapted to the end.

earlwb

Actually it was J-Tec who came out with a lawn mower muffler setup for engines. They had single and dual muffler setups.
Here is a dual muffler setup


Here is a example of the Davis DieselDevelopment Soundmaster muffler, I am using one on my old Fox .60 Blue Head engine


This engine survived a mid air once but the back of the muffler was broken off, so I stuffed a short lawn mower muffler onto it like this. I flew it like that for several years. That is a old ragged out beater plane that was a Hobbico Starfire .40. The plastics are all coming apart on it. The plane was retired.




That engine is now on a Combat Airmadillo but it has a OEm stock muffler on it now.


A while back I experimented with different things to make engines less noisy too.


Here is a bridge adapter I made for a K&B muffler to fit a Fox .45 engine too



Fox Eagle IV with a Fox Quiet Muffler on it.


I once tried to make a Fox Quiet muffler myself too and attempted to make it better as well.



I had talked about these farther back in this thread.
But one can make one or two piece bridge adapters to fit a muffler to a engine. One can also make a one piece off set adapter for a muffler too.
It depends on the exhaust opening and the screw hole spacing.

earlwb

Some more thoughts about engine noise. Fox had actually put a lot of thought into how the engines work. When he had a rear intake Fox Eagle III engine, the intake was buried down inside the cowl of the plane resulting in a 3db noise reduction. It is one reason the carbs are down low and closer to the engine, it helps reduce intake noise when the engine is cowled to some extent. He controlled the amount of axial movement the rod had on the engine so that it wasn't knocking against the backplate which made the engine quieter, especially at idle. You might have noticed a rather noisy click sound some engines make as you flip a prop over top dead center, etc. If you have heard some bushed crank engines at idle before, you'll understand how this quiets a engine by quite a bit. Plus not having the crankshaft slam back and forth as well. Another big noise reducer method was his patented exhaust port shape. The odd oval or triangular shaped exhaust ports reduced noise by a big margin by controlling the sonic shock waves coming out of the engine as the exhaust ports open. The straight cut exhaust ports exposes the entire shock wave suddenly to the outlet resulting in more noise. Remember there is a sonic shock wave effect that 2 stroke engines take advantage with using tuned pipes. So he controlled that sonic shock wave reducing noise. Another trick was using higher compression and lower nitro or no nitro fuels in the engines. This results in more power going to the crank and less out of the exhaust, as well as reducing that sharp high nitro crack noise you get when running high nitro fuels in a low compression engine. Another method is having the engine turn larger propellers at a lower RPM versus higher RPMs, as this results in less prop noise, which can be more loud than the engine itself. You can measure the noise difference with the Fox Eagle IV and another brand engine, using the same prop and fuel, when you run them both without a muffler and measure the noise level with a DB meter. So even with a not so good muffler, the engines tend to be more quiet than people might think. Do watch out with the props as many props are extremely noisy and cause much of the noise off a model airplane engine.

You see a similar effect with the Honda gasoline engine powered generators versus the regular gas engine powered generators. Just putting on a really good muffler does little to nothing to reduce the generator noise of the engine and generator. One has to engineer the engine and generator to work along with the muffler to make the engine much quieter, like Honda did with theirs.

1QwkSport2.5r

I've had this engine sitting here ready to run and just when I was going to start breaking it in, I found it wouldn't fit my test stand. The stock fox muffler dropped down too low. So, I dug through my few leftover mufflers and decided to fit a Thunder Tiger Pro .46 muffler to the little Fox since the TT muffler doesnt drop down. I didnt feel like taking the stock TT muffler off my Enya .30, so I pulled the Jettstream from the TT .46 that isnt being used right now and made a bridge adapter.

I have some trimming to do on the adapter yet, but it will function as it is. I doubt the Fox will turn fast enough to get on the pipe, but to at least break it in it should be fine. I'll try running it with the stock muffler when I have something to put it on where the muffler will clear.

Cougar429

My Feedback: (3)

I finished the Perry carb and pump installation and fired it up this afternoon. It took a turn in on the pump and some carb tweaking, but now have it running relatively good. Still rich with some leaning when nose up. I attribute that to a new engine and old fuel, something that once broken in should become less finicky.

NOTE: Had to disconnect my so carefully drilled muffler pressure fitting as the pump recommends against any additional feed source.

Numbers were a bit disappointing. If the tach is to be trusted, despite the fact at full throttle I could basically hold the fuse straight nose up by only one tire I could not get the prop over 9500. I may try a 2 blade to compare once peaked out. Should I expect more on a 3-blade? Have a Graupner 11/7 mounted now. I'm running that remaining jug of last seasons 10%. Trying to use it up before opening any of the 15% I picked up Friday, as well.

earlwb

The muffler looks good and your adapter is great. Nice job.
Is that the small case Fox .40 engine I see there?
If so, a 11x7 three blade is way too big for it. It likes to unload some so a 10x6 or maybe a 11x5 would be the prop to use.
Then it should run good.

1QwkSport2.5r

Yeah, its that Series 5 Fox .40, that your piston and liner went into. Single rear BB front bushing.

Hoping the carb is still okay and not missing any parts. I got this engine a few years ago completely tore apart. I'll "pretty up" my adapter as it could stand to lose some weight. I have to clean the paint off the aluminum and seal it up before I run it. I dont know if I can get the supplied fox screws tight enough, so I'm going to RTV the adapter just in case.

Cougar429

My Feedback: (3)

Earlwb, the 11/7 3-blade Graupner is mounted on the Eagle IV 60.

earlwb

Oops my mistake sorry Cougar429.  For some odd reason I mixed you up with 1QwkSport2.r.

Sport Pilot,  someone PM'd me and stated that they weighed a K&B .61 and a Fox Eagle I and they both weighed about the same within 1 gram of each other at approximately 406 grams.  But you are correct in that the K&B muffler is more quiet than the Fox muffler but it is also more restrictive too.

Sport_Pilot

I recall the Fox being almost an ounce heavier, and about the same power despite the more restrictive K&B muffler. Though Imay have used the K&B with a louder SEMCO muffler back then, But it still was not as loud as the Fox. The Fox carb was also an issue, not bad once set but difficult to get set up. The K&B used a Perry carb that was just the opposite, easy to set up, but you had to play with the idle disk evey time it got hot or cold.

Your weight might be with mufflers. The Fox muffler was very light, and I don't think I was using the stock K&B muffler. In fact I am not sure K&Bhad a muffler available back then. Fox was among the first to provide mufflers, though the first ones were not very effective.

earlwb

Yeah those early Fox mufflers didn't do much except maybe provide some muffler pressure. They did reduce noise a little bit though.
But way back then most RC clubs had a muffler rule, you had to have one. But there were no rules as to whether the muffler did anything to reduce noise though. I used those Dubro tonque mufflers for a while myself too. I still have some of those things along with the Streamline tongue mufflers too.
Those were next to worthless as mufflers but they did reduce the engine's bark a little bit.

earlwb

I found one of my old Fox Quickee 500 engines the other day. I thought I had sold or traded them all away years ago. Anyway, this one had the head modified by Nelson to use the Nelson glow plug. The Nelson Glow plug was a precursor to the Turbo Plugs you see on car engines today. But what makes it interesting is that you do not use a gasket with the plug, it seals via the tip of the glow plug, and thus isolates the space between the threads to improve compression a little more. The glow plug socket in the head is made special for that purpose. The Nelson plug is also larger than a regular glow plug too. I might have to fire this engine back up and see how it does today. Maybe make a video clip of it running or something like that. I think I still have some pylon racing props I custom tuned that I made years ago. I need to go and dig them up too. The engine also has the special made firewall backplate mount for the Fox engines too. This plate I bought, but the plate is more or less a flat piece of metal so one could make up up easily enough using a drill press and some hand files, etc. The engine also has the "big bore" Fox carb on it as well as the special Fox Quickee racing tuned muffler.

I used to tune the engine to run around 16,000 RPms on the ground, it would unload faster in the air of course. The trick though was to find a prop/engine/plane combination that worked Ok together. If the prop was too small, you would slow down too much in the turns and accelerate too slowly down the straights. If the prop was too big, you would go fast in the turns but everyone would pass you down the straights.

This is after cleaning it up some as it was gunky from all the old castor oil, fuel etc. I used some Dawn Power Dissolver on it. It leaves a little rust residue on the ferrous screw parts, etc. But a little oil takes care of that.




It is hard to compare the big bore carb from the standard carb, but it sort of looks like someone took a drill bit and drilled it out larger. Nothing fancy to to how they made it. But with that big bore carb you really have to keep the RPMs up high to get any fuel draw through the carb.


Before I cleaned it up.





Fox used a ABC cylinder piston setup in the engine, but the ports were really huge in comparison to other engines. As shown in this pic.


These drawing show how the huge ports were used to increase the air/fuel flow into the combustion chamber
Conventional engine porting flow


Fox Quickee engine porting flow


The Fox Quickee crankshaft had some modifications done to it as well.

earlwb

If you missed it here is the RCM MAr 1989 Magazine Review that was done for the Quickee 500 engine years ago;

1QwkSport2.5r

I finally got a nice day to run this 1983 Fox .40 small case engine. With the help of a new piston and liner courtesy of EarlWB, it's alive!

It will not stay running with a Fox idle bar plug, but it runs on it. I swapped to a McCoy MC59 and it runs without glow. First 3 minute run was with a 9x6 APC and 5%nitro 25% castor. I got a tach reading of 6800rpm.

earlwb

I hope it is just you are still running it rich, but usually they turn a 10x6 prop at around 11,000 rpms or so.
You did have the tach on two blade versus 3 blade too.