hsukaria

Well, an update on my Fox 74 Eagle IV that I bought used. I decided to just replace the head button. I put the new head button in it and test flew it this weekend. I was using 5% nitro, I built baffles inside the cowl, I was using an MVVS Quiet Muffler. The plane flew great with no engine stalls until last flight yesterday. I noticed that the muffler pressure tap had come loose along with the aft part of the muffler. I took out the aft part of the muffler, cleaned it out, and re-installed it with High temp RTV. Today, the engine was running well for the first 5 minutes, but then quit in the air. I richened it some more, but it still stalled after about 5 minutes of flight. I noticed that the muffler had come loose again, so I removed the aft part and re-installed the pressure tap. I was still having trouble, even on the ground. Suddenly, the glow plug fell out. It had come loose, possibly because of the lean run I had earlier?

I put the glow plug back on, the engine tuned for 10,000 rpm WOT (peak is around 10,500 to 11,000). The engine ran perfectly after that. Great power, great throttle response, and no stalling. Finally, I can say that this case is closed.[8D][8D][8D]

So, what I did was:
Replaced the head button with the newer design.
5% nitro instead of 15%.
Added baffling in the cowl.
Modified the muffler to reduce backpressure and tighten loose pressure tap.
Tuned the engine according to Konrad's suggestion of noting maximum rpms with a tachometer, opening the HS needle to very rich, and then gradually closing the needle until reaching approximately 500 rpms below peak. Except I had to go a bit richer than that at first.

Thanks to everybody who gave suggestions and advice to help me through this learning experience.

hsukaria

Put it in a Hangar 9 Sundowner 36. Perfect setup for it. The engine installs inverted. With the rear exhaust, you don't have to cut out the beautiful cowl and ruin the sleek looks with a side muffler sticking out. Exhaust downwards right behind the cylinder head.[8D]

50+AirYears

Well, I've been tied up with other things for a while, and haven't been on RCUnivers much for most of the time. I did spend some time not too long ago, kind of updating some of my Fox engines. Found out Dawn Power Dissolver cleans them up quite well, with little work. Even cleaned the crud of a 1960s vintage .15X RC that hasn't been run since around 1977. Getting a little concerned about my older .45s, because they had the older muffler,the new one engine has a different stack and mount, so I replaced the crankcasses on about half the .45s I have. That also gives me spares of the older style. Also changed a couple to the .46 head buttons. Did the same with some of my .35s. New crankcase, now I can mount mufflers on them. First time I ran one, noticed a major difference. I seem to remember starting with the needles opened about 3 1/2 turns, but now I had to open it almost 6.

Hobbsy

My Feedback: (102)

I mounted up my ringed Fox .74 Diesel conversion on Thursday, I sold the Saito 1.00 I had mounted on this plane, the Fox just sat right in its place. The prop you see is a Graupner 12x8 three blade that turns 9,500, I looked for a suitable 14x6 but don't seem to have one.

earlwb

50+AirYears, Nice going on refurbishing your engines. I never thought about replacing the crankcases on my old .45's. I made bridge adapters instead, so I could run other mufflers as needed. Such as like I did with the old Fox .45 with a K&B muffler on a Spad 3D plane. I used twp pieces of aluminum screwed together with the screw holes spaced for engine and muffler.




Huskaria, that Fox .74 diesel engine looks like it belongs there on your plane. The 12x8 prop is fine, I don't know if you have enough ground clearance for a 14x6 though.

Hobbsy

My Feedback: (102)

Earl, I'm going to be tied up today and Sunday doin motorcycle stuff even though I won't be riding, we're expecting 300 plus riders at our Church tomorrow to raise money for a little girl with brain cancer. I may post a picture of all the big V-twin Saitos that will show up tomorrow.

PS, I have a graupner 14x7, (two blade) I will try on the .74, I'll show you the clearance whether good or bad.

earlwb

Good luck and I wish you all the best too.

hsukaria

earlwb, thanks for the hint on the diesel. Even though my 74 has been running well with great performance, I have been considering it as a candidate for diesel conversion. My 74 is the only engine I own that requires 5% nitro or less. So, I have been having to buy and carry a unique fuel just for it. I also have been wishing I could run a bigger 14 inch prop or 12 inch 3-blade for my application. Going to a diesel conversion for it would be a good use of the diesel benefits. I will keep an eye out for Hobbsy's results of his 74 testing.

Meanwhile, does anybody have a diesel conversion head that they want to get rid of? Otherwise, I will purchase a new one from Davis Diesel Developments.

earlwb

I run all of my engines off of 5% nitro glow fuel. They all run fine like that. I only ran across a very few number of engines that liked and needed more nitro in the fuel to run OK.

Sorry I keep mixing you two up, Hobbsy and Huskaria. My apologies.

50+AirYears

I think I'm going to have to try some 5% fuel on the Eagle IV I have on a Tower Super Sportster 60. Been flying it about 12 years, just getting to the point where I can start it first flight of the day with an electric starter without stalling the starter. Still won't run out a full tank, gets a bit hot as well. Might try a head shim or two.
I remember starting my .59 and my K&B .61 with bare handed flipping. Still do on most of my engines. Won't even think of trying it with this Eagle. Not sure right now if I'd even try hand flipping with a thick leather glove.
I usually run 10%, and sometimes 15% on .40 and smaller, and have a couple pints of 20% for 1/2A. When I get a new gallon, I'll pour a little fuel into the old bottle and add 4 to 8 ounces of castor to the new fuel. I wrecked that .59, and almost ruined my first running McCoy .35 RH by using all synthetic, 18% oil, 10% Nitro fuel. Sometimes experts shouldn't be listened to.

hsukaria

Earl, that's ok about confusing names. At least you confused me with somebody like Hobbsy.[8D][8D] What you said also made sense to my plane. But I see now that what you said was for Hobbsy.

I think most of my engines can run on 5% nitro, except the smaller 4-strokes and a couple my 2-strokes.

Does Fox sell head shims for a .74? I don't think I saw it in their catalog/website. I may have to call them just in case I need them.

paul246

My Feedback: (9)

Did my little bit to support an American company, ordered a new Fox .45, whoohoo! Actually, I've always liked Fox engines, have had good luck with them and still run a few .40's. Anyway, willl be interested to see how the new carb design works out.

hsukaria

Keep us posted on your findings.

earlwb

No problem it works good for your plane too.
I don't remember needing shims on the heads before. So I don't know, you would have to ask Fox if they do or don't.

I have very few engines that need more nitro in the glow fuel. Most all of mine do run quite well off of 5% nitro glow fuel. Many of those engines run well off of FAI or no nitro glow fuel too.

hsukaria

I only used 0% nitro on my old Irvine for the first gallon, never had any trouble. My Fox, Irvine, Supertigre, and possibly Norvel 40 work ok on 5%. But I had a little trouble with the OS 55AX with 5% nitro, but maybe I didn't tune it good enough. I also had my 1.8 Saito on 5% nitro with no trouble, but I had some trouble with my Magnum .52RFS with lower nitro.

I am about out of the 5% nitro fuel, I might try the 0% just to say that I tried. The 0% nitro is $2 cheaper than the 5% nitro, $4 cheaper than the 10% nitro, and $6 cheaper than the 15% nitro, per gallon at the LHS

Cougar429

My Feedback: (3)

hsukaria, do you ever make it to the Toledo Show each April? We try to grab enough fuel for the upcoming season there as the price for 10% Rich's Brew is $13/Gal and 15% not much more. I've been running his fuel for quite a while with great success. With our weather it's always a crap shoot as to the amount to buy as the van can be crammed to overflowing by the time we head home. Last year I burned less than a gallon all season and as of a few weeks ago that has already gone out the pipe for 2012.

I fired up the Eagle IV for break in on 15% and did not notice any negative behavior. That may not be a good indication as I did not hear knocking with the 50BB until airborne. Perhaps too close to the direct exhaust hides that sound.

hsukaria

Hi Cougar, I buy most of my fuel like you, from Rich's Brew in the Toledo show. I usually buy the 15% blend and a case lasts me 2+ years due to the crappy flying seasons as you say (and smaller engines). This year I also bought Rich's Brew 20% nitro with all synthetic oil for some of my 4-strokes (it was cheap at Toledo). I did not buy 5% nitro at Toledo because at the time, I thought the Fox 74 could run on 15% nitro. But I was just testing it on the ground. Later on, when I got the plane finished, I flew it with 15% nitro and it stalled from overheating all the time (about 1-2 minutes into the flight). So, for the rest of the year until next Toledo Show, I have to buy the 5% nitro fuel from the LHS.

I might start testing my other engines one by one on 5% nitro to see how they work. I might eventually replace the 15% nitro with 5% on all or most of my 2-strokes. But I will keep the 4-strokes on 20% nitro/all synthetic (I only have three 4-strokes, so no big cost).

Darwood-again

Anybody know the prop nut thread size for a Fox Hawk 60RC?

Cougar429

My Feedback: (3)

From the Harry Higley web site:

Fox All Models .19 - .50 1/4-28

Fox All Models .60 - 1.20 5/16-24

Darwood-again

Thank you Sir.

rrengineer

My Feedback: (3)

I just got my NIB Fox .29RC for an Ebay auction I won with very little opposition. I am trying to re-create a Little Stick (I have a laser cut short kit) that I had back in 1974. I was stationed in Thailand with the Air Force at Korat AB. They had a Model Airplane club with a Quonset hut for building the models and a large model airplane flying field some distance from the runway. All I remember was the bleak selection of kits and engines, but the Midwest Little Stik and the Fox .29RC seemed to be a perfect match to me and it turned out I was right! That thing flew great! The problem I have is this "new" engine has apparently sat for a LONG time. The piston is stuck solid. It looks like the oil that had been in it ran out the exhaust port while it was in storage and left the piston dry. Rust? Maybe a little Marvel Mystery oil and a short bake in the oven? The oven part is OK, I don't have a wife to complain.
Mike MacLean

Cougar429

My Feedback: (3)

No way to know the condition of the liner and other ferrous bits, but try soaking it in a mix of alcohol and ATF fluid. If you can find a crock pot to warm things up for a day or so it would also work to free things up and penetrate everything with lube. Obviously, pull the glow plug.

earlwb

It is congealed castor oil that has gummed it up. We ran all castor oil in the fuel back then.
The .29 was sort of a hop up performance mod for .20 to .25 size planes. You can run a 9x4, 9x5, or maybe a 9x6 on the engine.
Fox test ran all their engines before boxing and shipping. So it is simply stuck from the old castor oil drying out. No rust.
Some heat and soaking in raw fuel or liberal use of WD-40 and heat will have it loosened up good.
The engines do take some time to break them in good. You can break it in quicker, if you heat cycle it. That is where you run the engine for a few minutes to heat it up good. Then stop it and let it cool off. Then repeat. The alternate hot and cold will break in the engine faster, than just hooking up a fuel jug to it and letting it run the gallon down.

rrengineer

My Feedback: (3)

I am aware of heat cycling and will break it in this way. I used Dawn Power Dissolver to loosen it up just now. I sprayed some down on the piston and inside on the con rod crank pin. After opening the back, I could see it was just old castor oil. After sitting for 15 minutes or so, I washed it out with hot water, then baked it for a while in the oven to dry it out. I put after run oil all through it and the crank is turning fine now. This engine has an idle bar glow plug from the factory. Will it run OK with any modern plugs? What kind of mufflers will fit this engine?
Mike MacLean

earlwb

The engine will work fine with a idle bar glow plug. The idle bar helps prevent the intake fuel charge from quenching out the coil element in the glow plug. But in a pinch a non-idle bar plug will work Ok most of the time, it depends on how much you need to have it idle and how slow to idle. I forget if it is really a problem or not at this time.
The standard medium range glow plugs work fine. Fox uses a RC long idle bar plug in the engines.

I am trying to remember which MAC's one piece muffler fits, but it literally bolts right on without any hassle.
Fox used the same Fox muffler on the .19, .25, .29, .35, and .36 engines (baffled piston types). Fox made the mufflers in a small rather crummy muffler up to a more modern looking teardrop shape muffler. They still sell the newer muffler design for the Fox .35 stunt engines too.

I just measured the muffler screw hole spacing and went to the LHS with my ruler and picked a Mac's muffler off the wall.
It is the 6200, 6300 or 6340 muffler I just forget which one. You can measure the hole spacing (center to center) and you'll see which one fits. Since several other engine's mufflers match up OK too, those become candidates for useage too.

Here is a couple of my planes with Fox engines using the Mac's one piece muffler on them.