Fox .35 vs. OS .25LA

[dirty dan]

I will say this one more time the FP- 20 is not stronger than the 25 LA!

I have flown ARF Flite Streaks back-to-back, one fitted with a 20FP (BB T-U, of course), the other with a stocker 25LA. The 20 was used with an APC 9-4; we tried the 25 with both APC 9-4s and 10-4s.

The 20 was the stronger engine, although not by a lot. And the 20 delivered a better run; much like a piped engine.

I have not done any static testing, measuring the revs each will deliver with the above props. Mostly because I have found ground testing with various props better at determining how a test stand might fly than how the actual model will fly.

Dan

[Brett Buck]

I have flown ARF Flite Streaks back-to-back, one fitted with a 20FP (BB T-U, of course), the other with a stocker 25LA. The 20 was used with an APC 9-4; we tried the 25 with both APC 9-4s and 10-4s.

The 20 was the stronger engine, although not by a lot. And the 20 delivered a better run; much like a piped engine.

     It's closer with a 10-4 than with a 9-4. The limitation I found with the 25LA was that at flight revs on a 9-4, it didn't have as much breathing room left for the maneuvers. It needed to be much closer to "gutted out" than the 20. I thought the 25LA worked best with 5" of pitch to reduce the revs so it has something left in level flight. But it was less effective overall because the pitch went up.

   The 25FP is significantly stronger than both of them, but for whatever reason, it doesn't seem to draw fuel as well a the 20 with the same venturi. Frequently you have to choke it down with a fine air filter, a ST spraybar, or something like that, at which point most of the power advantage goes away. It also doesn't regulate as well as the 20, even with the same muffler. It's like it has enough more power that it overcomes the rather weak tuning effect.

   The 25LA does have one significant advantage  - you can still buy one!

     Brett

[Andrew Hathaway]

The 25LA does have one significant advantage  - you can still buy one!

For now... But who can tell when OS will discontinue a product? 

Dennis, We go through the long break in and even longer wear in process, to reach the Fox experience.  The Fox still does what not many other engines can.  It's a different experience, that's worth the trouble to some of us.  If you want an engine that meets modern standards, then buy a modern engine.  The Fox is an antique design, and to be brought up to the same standards it'd probably have to be redesigned.  Assuming they could pull it off, they'd defeat the purpose of the engine to begin with.  The Fox niche is that it's a currently produced antique, without that it's just not the same.  Consider it a reproduction engine, with a few tweaks to make it more user friendly in a modern world.  It works as well now as it ever did, and is likely built to the same or better quality control standards.  That expectations have changed isn't really to say that Fox has suddenly developed a quality control problem.  The world has changed, Fox has stayed the same. 

Back to the "new Fox control line engines", I was talking about upgrades that have been made available for the Fox 35.  The point being that Fox has continually updated an antique, supporting C/L.  No one else has done this.  But I'm glad you brought up the new 60 since it's an even better example of how Fox has made efforts to produce new C/L products.  Granted it seems they were a bit misguided.  Developing an engine for a market that doesn't exist, and then trying to sell it by telling us it ripped the wings off the flying test stand, pricing it too high, etc... It's still more then most other manufacturers have done.  I don't see OS re-releasing the 40VF for C/L stunt.   

[Dennis Moritz]

De Hill and Andrew,

I just got off the phone with Dan Banjok. Checking information against what I remember. Actually I'm wrong about the specifics of the 2 new 60th anniversary engines. One was fine. Jack Weston broke his in a bit. Since then it's been running well on an Old Time plane. Dan's engine needed the rework that I described. That engine was sent back to Fox when Dan discovered that the bushing/crank fit was too loose (leaking fuel), the cylinder clearance too tight, etc. Fox sent the engine back without rectifying anything, at least that's how it appeared to Dan. Dan then went to work, machining a new bushing, lapping the piston, grooving the back plate, installing an o-ring and so forth. The back plate was acceptable as is, a typical Fox piece, Dan just figured it would be neat to have plate the fit perfectly. The machining also let him set the crankpin to back plate at a distance he thought optimum. The cylinder was out of round, but was o.k. (not replaced) after the piston was lapped in to fit. Dennis Truxal had 2 engines, at least as far as I remember, Dan only remembers one. See above.

The problem with cylinder/piston fit seems to date back to the 40th anniversary engines, when Fox introduced a cylinder taper, pinching the piston at the top of the stroke. Dan says that problems occur when the taper is a tad too steep, causing piston bind right above the exhaust port. Running in takes a long time, if that happens. Causing excessive wear to the rod. Dan discovered this issue when running in a new 40th that would not top 9000 revs with 9x6 after a half hour break in on the bench. After careful lapping the engine came into it's own. Running with a lot of power. Dan's new 60th is a very strong runner now, with a strong break, lots of power. The pre-40th engines are made with a straight cylinder wall. Those engines break in without much issue, but are poor at hot starting. Tapered sleeve engines probably make a bit more maximum power.

Yep, Foxes have their fascination.

FPs and LAs can be adopted to our needs and made to work well. Longevity is rarely an issue. Easy enough for those of us past 60, to lay in a lifetime supply. Comparatively cheap, too.  Beyond that, of course, are the dedicated stunt engines. Amazing products. Durable, tunable and manageable, etc. Great, great products. Dan's PA61 was in steady use for five seasons. Still runs great. I doubt that the Fox 60 would compare. At nearly $300, if you can get one, well, that's near PA/Ro-jett territory.

[De Hill]

Uhh Dennis,

Does this mean you were wrong about Fox .35 reliability?

De Hill

[Dennis Moritz]

It's not reliability De Hill. It's quality control. Dan's engine was a mess. Sending it back to Momma Fox didn't help.  Dennis' needed to be lapped. Period. Running an engine in for a season. No. Not good. Actually, the Foxes can be amazingly durable when the parts are harmonized. I'm sure you know that. I've seen many run year after year. Abused and run hard. We in Philly can make them scream. Amusing old buggers. Like the folks who cherish their eccentric ways. (And history.) Lots of Philly Fliers are into them. It's taken me years to get my FPs and LAs to behave. Even with the wise generous council of the knowledgeable and skilled. On to Foxes? Mebbe. I have a few. There's a Ringmaster somewhere in my future, I'm sure. Nearly everyone in the club has one. Usually ugly beasts, crashed and crashed again. Contest winners nevertheless. I'd like to build a purty and light Ringer. Probably a bad idea for aFox 35 paint shaker. So what. Boldness. Boldness counts.

Best,
Dennis Moritz

[Jim Kraft]

One thing I do when I get a new Fox 35 is remove the plug, and turn the engine over to feel the tightness in the cyl. I then loosen and tighten the head bolts till I get the least amount of drag when turning the engine over. Sometimes it only takes a 1/16 of a turn on one bolt to really reduce the tightness in the cyl. This really speeds up the breakin and only takes a few minutes. I do this on FP40's also as it is very easy to warp the cyl on them also. I did have one 50th anniversary model that did have a wet nose, even thou the bushing was not loose. After a call to Marvin Denny I removed the shaft and finished cleaning out the groove in the bushing that was slightly plugged at the rear. That took care of that and it never leaked out the front after that. I have some Fox 35's that have very loose front bearings, ( the best running ones btw ) that still don't leak out the front as long as the groove is clean.

[De Hill]

My Fox, and my Ringmaster; they comfort me.       

[Dennis Moritz]

De Hill, that is a funny line!  Thanx.

[Andrew Hathaway]

You can't really go wrong with a Ringmaster and a Fox 35.  Mine is scratch built.  I cloned the original kit with decent wood, a spruce spar, and real plywood.  At 26oz it does the job.  It'd probably fly better with a OS 15FP, but then all the ambiance would go right out the window. 

[Clayton Berry]

I hear all of the defense lines about the Fox units - but I've never had to speak to Japan or China.

Keep hanging on to it, but guy in the mini van next to you ahs a six disc CD, a navigation system, adjustable brake and throttle, heated seats, and more cub holders than even grandma would need.

Doesn't have any Fox logos anywhere.

[De Hill]

Clayton,

I don't care if anyone else runs Foxes.

I enjoy them.

(and pacific rim engines also)

[Andrew Hathaway]

According to my handy engine inventory list, I currently have 10 more OS engines then I do Fox engines.  Added together those two brands make up 2/3rds of my available engine stockpile.  Both brands have their place.  It's like having the fully loaded, luxury car to drive everyday, and an impractical, uncomfortable, classic car to drive on weekends.  Sure a person could take that minivan to work or the grocery store, but the guy that takes his vintage muscle car is probably going to have more fun. 

[john e. holliday]

I am afraid to count how many engines I have.  I know of one that is still brand new in the box.  When I started it was with an OK Cub .049A.  Then Cox Babe Bee.  From there it has grown to McCoy's, Fox's, Johnson's, K&B's, Super Tigre,  OS and O&R ignition that I need to get running.  I know almost all the planes have engines on them, I think about 30 planes.  Have fun,  DOC Holliday