Broken Wings

My Feedback: (20)

I think you'll find they are not as common as you think...Enya uses some odd screw thread pitch(s) in some of their engine fasteners. 3x 0.6
3x 0.5...

1QwkSport2.5r

It makes the most sense to use socket head cap screws since that's what nearly all engines come with these days. Every engine sitting on display at the hobby shops have cap screws. I much prefer to swap out OEM screws if they're chewed up.

Hobbsy

My Feedback: (102)

I've been doing that since I got my first Fox .74 ABC from Morris' Hobbies a long time ago.

1QwkSport2.5r

I ran my Fox .50 today, put about 1/2 gallon through it. It's not totally loosened up yet, but it does run pretty nice. Lowest idle with a 10x6 prop was about 2,600rpm but I didn't spend any time fine tuning the idle. I was pretty surprised to only see 13,400rpm peak on a 10x6 APC after 1/2 gallon. Granted, that is on 5% nitro fuel and a modified head for set up for 10-15% nitro. These things must have significantly smaller port passages than say a ST G51. My G51 turns the same prop at 14,500+ on the same 5% fuel.

Being I wasn't sure how much time this engine had on it before I got it (looked like it was barely new) I treated it to my typical ringed break-in. 12 tanks 6oz each; about 5min/tank or so. Enya 3 plug, MA 10x6 (K) for the first 10 tanks. Peak 10x6 MA was 13,550, APC 13,400, APC 13x4W 10k flat. My G51 runs 10,800 on the 13x4W. Stock mufflers.

hsukaria

Do you run all your engine tests with tubing attached to the muffler outlet? Doesn't that hurt performance some?

1QwkSport2.5r

It ran the same with or without. I just try to divert some of the oil mess. I've found if the ID is bigger than the muffler ID and keep the length to less than a foot it doesn't cause any problems/major performance loss using stock mufflers. If anything it should help performance slightly since the overall exhaust system length is longer.

1QwkSport2.5r

I forgot to mention; when the engine is running in a clean 2-stroke, the exhaust gas temperature is hot enough to break down the vinyl tubing. Once it starts cracking it pretty much falls apart right at the back of the muffler pretty quickly.

Sport_Pilot

My .50 does more RPM than that, (about 13,700 or so) on an 11x5 and unloads pretty well using 5% nitro. It seems more powerful than a TT .46 with 15% nitro. But the TT pulls more RPM on the ground. I think maybe the Fox unloads more in the air.

1QwkSport2.5r

I suppose it may unload more, but pitting a .50 against a .46 on the ground and being a 1,000rpm difference if not more is pretty significant. The TT .46 and ST G51 (Italy) are about equal in power, My small case lapped piston Fox .40bbrc runs faster on the ground than the .50 does on the same prop and fuel.

Sport_Pilot

I don't think I have ever run the .50 on a 10x6. But it does more RPM than that on a larger prop. It's a bit low on compression with a noticeable ridge at the top of the cylinder. Maybe yours needs more running in?

earlwb

The .50 tends to be flow restricted due to it being overbored. If you took apart a .45 and a .50 you could then see how little of the port passages there is left to flow the air fuel mixture into the combustion chamber. As they bore out the engine, the passages become more narrow and cannot flow the air fuel mixture as well as a smaller .40 or .45 can. Thus the .50 will not turn higher RPMs like one might think it would in comparison to the .45's. But the .50 will turn larger propellers much better than a .45 can though. 11x6 and 11x7 props work well with the engine.

It also takes a while to break them in good before you can really wring them out too.

1QwkSport2.5r

That's part of the reason I'm gonna put a diesel head on it. I do not know how much time this engine has, it felt pretty tight; similar to my Fox Twin. That was and still is a pretty tight engine.

Hobbsy

My Feedback: (102)

Earl, is the outside diameter of the .45 liner the same as the .50, a .50 liner will slip right into the .46 crankcase. In fact both of my .50s are .46's with .50 liners in them. I busted the only real .50 crankcase.I had.

earlwb

I never tried to see if the liners would fit one or the other engine. So I can't say if it works or not.
But if it did in your case, that is quite fascinating. I'll have to think about it. I never wore out a cylinder liner in one yet.

hsukaria

That brings up the point you made of restricted flow in the bored out 50 (or any other engine that is an overbore): Even if the liner fits in the same cylinder (bigger inner diameter, but same outer diameter), the port size doesn't get reduced, but the same size ports are feeding a bigger swept volume. (I hope that is clear)

Sport_Pilot

True, but the difference is only .,05 cubic inches. So not really a factor. I think it more a matter of break in in this case. But the 50 is supposed to be timed for lower RPM, but should turn a 10x6 better than 1QwkSports engine. If not the break in, could the cylinder be turned partially blocking the ports? Also Fox has changed port timing and combustion chamber design on engines without telling anyone. I believe there may be a lower compression version out there, but I don't know if there were any changes to timing.

1QwkSport2.5r

The liner is straight, I checked it. The timing has not been measured yet, and the head button has been modified for higher nitro. 10-15% I'd guess. BUT, it should still turn faster I would think. I dug out my billy club props, so I'll test some heavier loads and see what happens. The piston rings were shiny silver and not black so it had been run enough to wear the black off the rings prior to me getting the engine.

The .60's use the same head buttons (same bore) and I happen to have a pair of high compression buttons for low nitro my buddy and I made up for my Twin 1.20. I have to clearance the button to clamp clearance a little and I'll try one out. What my objective here is to get some baseline power figures before I convert it to Diesel. If things work out, it'll be burning diesel fuel on Monday.

Sport_Pilot

What plug are you using? With that head you may be serverly retarded, (the timing LOL). So a hotter plug may pick up some revs.

1QwkSport2.5r

It came with an Enya 3 in it and I just left it in there; it worked. The Enya plug is a good 2 threads short of the edge of the combustion chamber so a longer plug should do better.

Sport_Pilot

That is a good plug, but I am not sure that is hot enough for low nitro with a high nitro head. Did you check the stamping on the side to be sure it is a #3?

1QwkSport2.5r

Absolutely. It is a good hot plug but having the end of the plug recessed further away from the chamber can cause minor issues.

1QwkSport2.5r

Thought I'd post pics of a 'small' flaw I found on the needles of my Fox twin. Idle needles that is. The reason I pulled them out is due to the fact the mixture didn't change on the rear cylinder when adjusting the needle. I checked for obstructions but found none.

hsukaria

Ok, I see a couple of needles, but where's the flaw? Is it the upper one a little bent?

BTW, you always use just nice wood in the background. My scrap wood is a lot "scrapier".

1QwkSport2.5r

It's hard to see it in the photo I posted (I took 4 total) of the right needles damage, but if you look at the tapered end closely you'll see the end is all boogered up. The left needle is worse than the other, but they are clearly damaged. Noting the end isn't all shiny, the damage isn't from being over tightened against the seat. Moreover, hardened steel will likely damage the aluminum before the aluminum damages the steel. I'm going to attempt to file them smooth on my buddy's lathe. I just hope the carb bodies aren't damaged (the seats).

Im trying to to get the engine tuned using the low compression heads to get a power baseline before I run it with my custom high compression head buttons.

The test stand I made for the Fox twin is made of Hickory. I got a bunch of it from work (scraps). One of the perks of my job. I have some Brazilian Teak and Brazilian Walnut in the garage that's beautiful as well.

earlwb

Usually the needles use the middle portion of the taper for controlling the fuel flow and mixture. So filing a little off of the buggered tips should not be a problem. You could probably gently chuck the needle up in a drill press or drill and then carefully use a file on it.

But since the needles tend to use the middle part of the taper and not the tips, the buggered tip would normally not be a problem. But that one needle with the badly buggered up tip does look like it needs some help though. It is surprising it got thought quality control that day, but maybe that day was a day just before the holiday started. But then the buggered tips may have been missed as the engine would still run OK for their test run at the factory as they aren't trying to fine tune it or anything.