rrengineer

My Feedback: (3)

Wow! They just line right up with the holes in the cankcase. I'll have to file down the two little raised bosses above and below the exhaust port for a flush fit. With an exhaust diverter like the one in your first picture you can keep the airplane pretty clean from the looks of it. Thanks for the info! Maybe I should read the owner's manual that came with it in any case. You can tell it's old, the paper is yellowed on one side I'm guessing where it was exposed to the light at one time. The box it came in is an off white and only has "FOX 29RC" with "22900" stamped on it. Makes me wonder when this was made.
Mike MacLean

earlwb

Sorry about that, I forgot that they miht have two raised center bosses on some of the engines. Yeah you have to carefully file them down a little.
But yeah the mufflers just bolt right on with little or no effort.

The original mufflers had a flange that wrapped around the engine exhaust outlet. There was also the earlier engines that had a rotating exhaust baffle coupled to the carburetor. The first type had no flange and used the center holes to mount the muffler and allowed the exhaust baffle to stay in place. Later they used the center two holes for those engines and a flange wrapped around covering the holes that was left over after you removed the baffle. Then they had just the flange and the two center holes. Later they made the engines with the outer two mounting tabs and no exhaust baffle and you could use either the center or the outer tabs to mount the mufflers.

The .29's were made almost from the beginning of the first stunt .35 engines back circa 1948 or so. The RC versions came out in the 1970's. They still made and sold the engines up until the early 1980's. Nowadays only the stunt .35 survives in a lapped piston and a ceramic cylinder version.

The .29X RC with a guillotine exhaust baffle couple to the throttle first appeared in 1970. The .29 RC with the rotating exhaust baffle coupled to the throttle and two screw holes in the center for the muffler first came out in 1972. If I remember right around 75 or so, Fox came out with the side mounting tabs and dispensed with the exhaust baffle. The Fox .36RC came out then and they still had some .29RC versions too. I forget when but Fox started bead blasting the crankcases to give them the dull gray color look instead of the shiny polished aluminum color look.

rrengineer

My Feedback: (3)

Well, aren't you the wealth of Fox information! ;^) Mine is the bead blasted crankcase, it's the carb and backplate that is shiny. I went digging through my parts boxes and found a brand new Mac's muffler that looks to be a perfect fit! I just need to ream the two through holes in the crankcase tabs for the slightly larger mounting screws on the muffler. Now that the engine is loose and lubed well, it really pops when you turn over the prop. Great compression! This should be fun! Thanks Earl.
Mike MacLean

SRQFlyer

My Feedback: (17)

Need some advice from the Fox experts. I have a .25 BB Schnuerle that appears to have a slightly bent (don't ask) crankshaft stud. An email to Fox on how to remove it got no answer so, please help! Are the threads right handed? (I would guess so). Is some heat in order? Any help would be appreciated.

Jim

earlwb

They just unscrew like normal, they aren't reverse threaded. You might have to double nut it to get off, but if it is bent, just latch onto it with a pair of vice-grips and unscrew it. of course you need to hold the crank still somehow so it'll unscrew. The stud is not normally in there all that tight, it should come out without a lot of effort. They can't use a reverse thread on it as it'll loosen up on you when the engine is running.

SRQFlyer

My Feedback: (17)

Thanks -
It's late I realized (after posting) that it MUST be RH threads. I'll try vise-grips with the crank in vise with padded jaws, but not until tomorrow when I'm awake.
Thanks again,
Jim

Cougar429

My Feedback: (3)

Along with Rare Bear I maidened the F-15 today. Both times the Eagle IV died in flight and I had to set it down in the beans alongside the field. Both times the glow plug had failed. There were hints of black on the leading edge of the wing, but I would have thought by now the motor would have worn in enough to get past that.

Plane survived and only needs control surface tweaking. Seems more tankfuls will need to be run before trusting it in flight again.

The muffler mod does a fine job of taming the noise.

hsukaria

Cougar, we (I) lost track of what you have on that F-15. Are you running the old head button, how much nitro, prop size, muffler, etc.? I went through in-flight engine stalls for a few months until changing head buttons and lowered the nitro to 5%.

Cougar429

My Feedback: (3)

The Eagle IV 60 is stock except for the muffler and Perry pump and carb, (required since the tank was moved aft approx 12" to the CofG). It was NIB and only a couple of years old when I grabbed it and the head has never come off, so not sure which button it has. Both were idle bar style plugs.

I was running 15% with a Graupner 11/7 3 blade.

Here is a pic with the new muffler and stock carb. Perhaps that can tell what gen it is. Second pic is installed in the aircraft.

earlwb

Cougar429, that is a pretty awesome setup there with that engine, you might want to study those glow plugs more closely. You may be running the engine a touch too lean or have a odd vibration problem or a little detonation going on too. You might even need to run a little colder heat range glow plug too.

Here is Duke Fox's article on glow plugs.

hsukaria

Cougar, I agree with earlwb, that is an awesome setup.

Your pictures show the older style carb and crankcase. So, it may be possible that the head button is the older high compression version. That means that the engine has to be run with lower nitro (0-5%), extra rich, and with a medium plug, like the OS #8 or Fox #8 (from my limited experience). In any case, I found out that a lot of fuel has to be run through it for breakin, I had to go through at least 2 gallons. At least with your setup, you don't have a full cowl over the engine with baffling requirements.

By the way, how much rpms are you getting with that Graupner?

Sport_Pilot

I think the Fox #8 plug is a colder plug that Fox suggests for the 60 and 74 engines that have detonation problems.

hsukaria

That's what I use on all my 2-strokes. I use the Miracle plug on my 4-strokes.

Cougar429

My Feedback: (3)

If I get a chance I'll pull the head and take a pic of the button. Worst case I can try the same mod I made to the 50BB button to reduce the squish. Before I made the mode on the 50 detonation was audible in flight, but not on the ground, (?????). Did not hear anything like that yesterday.

I think I posted the RPM from the breakin runs. Cannot remember what it is now.

Cougar429

My Feedback: (3)

I pulled the head and button yesterday and was found the screws not very tight. That may not have helped, but the behavior Monday follows almost directly that described in the Flightline Solutions for Fox column.

I found the head button to be identical to the second from the right in the Flightline pic, the exact same style I found in my 80's gen 50BB. Sorry for the focus on mine, still figuring out the new camera and macro was impossible to find in the time I had before work.

Can't tell how long this motor was stored NIB, but I suspect a bit longer than I originally thought. I did some of the modding suggested by Flightline, bevelling the squish band and radiusing the inner edge. This made a huge difference on the 50. However, I only took .015 off the top. I will try it first that way and tweak it again if necessary. I'll bring both the head and button back to work today and see about the cleaning up of the inner head surfaces for better heat transfer. I'm sure that, the rather loose head screws and the 96F environment would have helped add to the heat load.

Cougar429

My Feedback: (3)

I found what killed the plugs. There is nothing left of the back of the piston above the ring groove, It is totally busted off approx half way round. I strongly suspect detonation caused this.

Anyone have a spare piston?

earlwb

Aww man, major bummer. Fortunately they sell the pistons separate. So it shouldn't be a problem to get it from Fox.

Cougar429

My Feedback: (3)

Waiting for a reply from Fox as to price and availability. Also asked for the cost of a ring as I don't know what kind of pounding it took.

I pulled the sleeve and it is unmarked. Phew! As the head button was also unmarked the piston must have burned or broken away in microscopic bits. I took a look at the glow wire as best as I could, but will remove the idle bar to have a better view. From initial inspection the wire is not deformed.

hsukaria

Hi Cougar,
You might want to consider a new-style head button from Fox while at it. Not very expensive and known to help with overheating, as I experienced.

Cougar429

My Feedback: (3)

Do you know if the new head button incorporates the changes suggested from Flightline? Already made them to the stock button.

Got a reply from Fox and will look into replacement parts. Never had this sort of behavior in a brand new engine. Drats!

earlwb

Since cougar429 has a Eagle IV engine it very likely has the current head button in it. Unless someone had done some parts mixing and matching in the past. Such as setup the engine to run zero nitro glow fuel like they do in Europe, for example. Normally I don't consider the Perry carb a problem, as I never needed to use one on a Fox engine, but I know others did though.

My first thought was that the engine needed more running in. With Fox engines you need to run them in real good before you really try to dial them in for performance. Sometimes it takes a lot of patience if the cumulative tolerances of the assembled engine leaves it extra tight.  Next it is the fuel. I normally run 5% nitro content glow fuel in my engines, I rarely need 15%. Normally I don't expect the fuel to be a problem, but it might be with the Fox engine running on a tuned pipe setup. So the higher nitro content fuel can aggravate the situation and help cause detonation. Then running a tuned pipe like setup causes the engine to step up in power as it comes onto the pipe. This leads to detonation as the tuned effect pushes more fuel back into the cylinder that would have otherwise gone on out of the exhaust. Also when the engine comes up on the pipe, the compression ratio increases and can lead to detonation too. Usually you need to run a more cold heat range glow plug when using tuned pipes in order to handle the added heat and stresses from the combustion cycle going on inside of the engine. Worst case was maybe possibly running the engine too lean which can lead to detonation as the engine heats up a lot more. Now this is not lean where the engine would sieze but on the razor edge, so to speak.

So I would try some 5% nitro glow fuel and run the engine for a while longer to help run it in. Use that with the tuned muffler setup. Then try a colder plug to see what happens.  If the engine acts like the plug is too cold (engine drops in RPM a lot with glow ignitor off or doesn't idle too well) then  try your 15% fuel and see what happens.

Cougar429

My Feedback: (3)

Earlwb, thanks for the input. I have run tuned pipes in the past and from what I could tell that muffler did not exhibit any tuning effects. Transition was smooth all the way through the throttle range. The Perry carb and pump were installed since the tank was moved aft, (this plane is notoriously nose heavy) and again, the mixture seemed fine with no bogging in flight. Until the plugs died it was rather well behaved.

NOTE: The pic shows a shaker pump and was taken much earlier. I sent pics of that installation to Gary Conley and was advised they do not work well on 2-strokes nor is vertical mounting a good orientation. Due to that I picked up a VP-30 pulse pump from him with the matched pump carb from him at Toledo. Due to the size I had to build a compartment aft of the firewall and route the pulse line directly from the back plate.

I sent another message to Fox asking for some information regarding the failure and if there is a newer style head button than the one in the pic. I also wondered about the type of failure due to the fact there was absolutely no indication of bits banging around in the combustion chamber. I took an additional pic, (with my newer camera that seems to work better for macro and low light) and included that with the pic of the head button.

hsukaria

earlwb, cougar,
My 74 head button looked different than the new one I ordered from Fox, even though my engine is newer vintage than Cougar's.

earlwb

That is interesting. Then they could have changed the head button a short time ago.
So it might be worth checking it out. Of course Cougar459 knows how to modify the head button too. So he could do the mod himself, if need be.
So then it could very likely be that the engine still has a little too much compression in it, at least for 15% nitro glow fuel.

hsukaria

He probably doesn't need it since he did mention that he modified it himself per the Flight Line Solutions suggested design. I thought it would be educational for everybody to see the difference between the Flight Line Solutions design and the newest Fox design. I had to get a new head button anyway because the glow plug threads had stripped, and because I don't know jack about machining.

My engine ran ok on the ground with 15% nitro, but when in the air, it overheated badly and finally would stall after 1-2 minutes in flight. With the new head button and 5% nitro, no problems. I have some 0% nitro that I plan on trying pretty soon. If no bad effects, I will go to 0% even.