Fox 15 Bashing

Ever since I found Isky's two years ago I have read the continued criticisms of old Fox 15's. There has been a lot of ranting but little quantitative explanation of the negativity. I realize that many of you think the little Foxes are OK, but can I get a technical explanation of the reasons for disliking or liking them? Does anyone have hard data? Is it a metallurgical or quality problem?

I have several. They seem fairly light, and start and run reliably. And there seems a steady supply of them on eBay.

By the way, Currell, since I know you will read this, I for one would love it if you would one day summarize your knowledge of Foxes. If you ever do that I will, with your permission, make it a credited page on my web site.

I have also happily used the old Fox 15, and am currently putting one on a Shark 15 for Classic.

I think that the "problem" is that it isn't a 2-4-2 type of engine. Also, it is really loud, and eats fuel.

But, the power to weight is great! Mine turns an 8-4 Rev-up at 14K on 10%/28% stunt fuel. It does, however, go through as much fuel in a flight as my Saito 30.

With the correct choice of a lowe pitch prop, and forget about the break, run it flat out, it is a very nice engine.

Hi Bill,
I am using a Fox 15X on my Flying Clown because its light and reasonably powerful. It stock except for drilling an oil hole in the connecting rod and polishing the ends of the wrist pin so they don't wear into the sleeve. I also filed the spray bar to open up the venturi some.
I would recommend using lots of castor, just like with the Fox 35. I also use 15% to 20% nitro.
If any of you guys are going to through them away, send them to me!
John Wright

Larry, where are you getting you're 10%/28% fuel from? I looked on the Fox sight and there 10% is only 20 % oil, so you must be using sumptin else. I've read in the other thread about Fox 15's that 15 to 20 % nitro is preferable in these engines, but that would be a special mix of fuel too. Red Max?

Fox Missile Mist was the favorite fuel of all my Fox .15s. I'm having pretty good success running them on Powermaster 29 castor and 10 nitro now.

I agree that a lot of the older flyers think that because it dosn't 4-2-4 it's somehow not a proper stunt motor. That said I happen to love these little suckers, why not, light and powerful and cheap to own easy starting and long lived
I use 15% nitro and 25% oil with an 8/4 prop being the usual fare, but I have used 7/5's and 35% nitro on some of the old 15 size combat planes I used to run.
I'm also running one on a flying clown and find it to be an ideal match for it. Granted if you need something really slow this isn't it but, it's surely a managable combination and does the old time pattern well.
Red Max and S&W will make fuel for you in any configuration that you want and there are probably others that will do the same.

>Fox Missile Mist was the favorite fuel of all my Fox
>.15s. I'm having pretty good success running them on
>Powermaster 29 castor and 10 nitro now.

I liked the purple stuff, when I could afford it, but have learned since that it had only 18% castor in those days, so no wonder my GH 35's and some others, like Fox 15's, wore out quite rapidly! I was unaware for many years that the fuel I used more of than any other branded fuel, K&B 100, was only 20% castor, but I didn't "burn" much up with that - no shaft runs and few squeaky- lean cookups using it.

Kiwi

John, I have an idea. Hold a Fox .15 heaving contest over soft grass, and require every contestant to bring their own motor!

Going on a trip, but will have to get with you on getting my .15X running. Going to put the baffle .15 on my son's Flying Clown as it should be ready to go at 10 to 11 oz, vs the 14 oz mine is.

Had troubles completing the old time pattern on 2oz of fuel at VSC with the baffle .15. Is this normal? Is the .15X more efficient or should I go ahead and refit a larger tank?

Thanks,

LAST EDITED ON Jun-06-02 AT 09:59 PM (CST)

Never having attempted entire pattern of any sort with a Fox 15 engine, baffle, or Schneurle, I never noticed if they were less efficient than some other smaller engines.

I don't think we ever put a tank bigger than 1 1/2 ounces on any plane flown with any 09/10/15, but since most of the flying of those was done by my sons and their friends, I wasn't conscious of fuel economy problems. The planes flew 5-6 minutes on that size tank, so I'd have expected 7-8 or more from two ounces!

Hmmm? That doesn't help with the question, so what comment did I want to add? Geez! Don't grow older! Too many drawbacks!

. . OK, recaptured that escaped thought! In the last message, "baffle piston" is used as if it helped to separate one of the steel fin 15's from the 15X's. But both had the same type and design (baffle, sintered iron) piston. Probably exactly the same, if I know Duke, and I did, to some extent, at least.

I wouldn't have owned one of the older ones, had J.A.K. not been generous with a spare. Those were off the market long before my kids were old enough to start flying (ages five and six), and the older Fox 15 had come out after I had already considered myself "graduated" to bigger and more powerful engines.

K.

>By the way, Currell, since I
>know you will read this,
>I for one would love
>it if you would one
>day summarize your knowledge of
>Foxes. If you ever
>do that I will, with
>your permission, make it a
>credited page on my web
>site.
>
>Bill Groman

Bill: I will do this. Currell

>
>Had troubles completing the old time
>pattern on 2oz of fuel
>at VSC with the baffle
>.15. Is this normal?
> Is the .15X more
>efficient or should I go
>ahead and refit a larger
>tank?
>

Tools: Surprised to hear this. Two ounces should be more than enough. That is a big tank for a Fox .15.

Are you asking if the .15X one piece case Fox is more efficient vs. the earlier Steel Fin? As K. says, they both are baffle. I would say that fuel economy is very similar. Peter Chinn's Engine Review articles show somewhat more power for the .15X, which is of course the one piece case model, although I notice the variation is more between motors of same type, than between different models. In other words, a " pretty good" Steel Fin has more power than an "average" .15X.

Re: the fuel I use, it is L&J's fuel for Fox's, and available from RSM Distribution.

www.rsmdistribution.com

Currell,

If you get the data together, I will photo as many Foxes as I can find to illustrate the info. It would be very cool if we could manage to get photos of most of the .35's. This would be a fun and useful project.

That would be a cool project.

Very cool!
catdaddy

...I will photo as many Foxes as I can find to illustrate the info...

Bill,
If you have trouble with the .15's perhaps I can help. I have Steelfins, X's, and Schnuerle's.

Also, about the steelfins: I looked mine over and found that the one I bought from the first run back in the 50's has an offset plug. The other one (bought used) has the plug NEAR center but is offset about 1/16" to the exhaust side. Is this what is being referred to as the one with the center plug? Another difference is that the headfins are a little more rounded than the first ones. Everything below the head appears to be similar externally.

My "X" .15's have slight differences in that the first one had no provisions for a muffler. The next (I think) had the muffler attached above and below the stack. The next had fore and aft mounting. One of the mufflers for the X is a flow through and one is not. Also, one muffler has provisions for both methods of mounting.

My first Schnuerles (or Schneurle) are plain bearing, the rest are BB.

In other sizes I have, .049(FAI), .07, .19 (3 and 4 bolt backplate), .25 (4 bolt and schnuerles), .29 (3 bold backplate), .35 (Brodak version).

Let me know if you need pictures of any of these. I have a CHEAP digital camera so I might have to go with regular photos and scan them.

Hi George,

Thanks for the offer, and yes, photos of as many versions as possible will be a great help. Why don't we try a sample one with your digital camera first. Take as high a resolution photo as your camera permits, and email it to me as a JPEG. I will use my own editing program to adjust it if necessary to see how it looks on the web site. While Currell is working on the text material I will assemble as many photos as I can get.

Don't forget that the first 15X didn't have cooling fins on the crankcase and the needle valve was different then later models

denlip,

Good catch! The first slant plug version has a pressed-in nv assembly and no lower fins. Additionally, I noticed that later models have the crankcase filled in between the two top fins, probably to better hold the head screws, and the finish on the newer ones is shiney where the first version is not.
Also, I noticed that my version with the fore/aft muffler mounting also still has the over/under holes.
I guess as with any other company, some will be mix and match as manufacturing changes were made.
Question: When Fox came out with the schnuerle .15's they had both plain and BB versions and later switched to only BB. Are there any external changes to tell "versions" on the BB models? The only change that I'm aware of is the internal groove on the crankshaft bearing to provide more lube to the front bearing. I have had no reason to remove the shaft and check it so I'll just trust others that it's there.
George

>
> Also, about the steelfins: I
>looked mine over and found
>that the one I bought
>from the first run back
>in the 50's has an
>offset plug. The other one
>(bought used) has the plug
>NEAR center but is offset
>about 1/16" to the exhaust
>side.

George, you've got me really confused on this one. The offset plug ones are a full 1/8" offset, to the bypass side. You have a factory error, I guess (McCoy Redheads can have plug hole pretty much drilled at random, so these things happen. Want to sell or swap it? Pretty please

Is this what is
>being referred to as the
>one with the center plug?
>Another difference is that the
>headfins are a little more
>rounded than the first ones.
>Everything below the head appears
>to be similar externally.

Again, you have the advantage on me. I see no fin difference between the offset and center heads.
>
> My "X" .15's have slight
>differences in that the first
>one had no provisions for
>a muffler. The next (I
>think) had the muffler attached
>above and below the stack.
>The next had fore and
>aft mounting. One of the
>mufflers for the X is
>a flow through and one
>is not. Also, one muffler
>has provisions for both methods
>of mounting.

Agreement/understanding here! These muffler changes pretty much mirrored what was going on with the bigger Fox engines.
>
> My first Schnuerles (or Schneurle)
>are plain bearing, the rest
>are BB.
>
> In other sizes I have,
>.049(FAI), .07, .19 (3 and
>4 bolt backplate), .25 (4
>bolt and schnuerles), .29 (3
>bold backplate), .35 (Brodak version).
>
>
> Let me know if you
>need pictures of any of
>these. I have a CHEAP
>digital camera so I might
>have to go with regular
>photos and scan them.
>
>George

...George, you've got me really confused on this one. The offset plug ones are a full 1/8" offset, to the bypass side. You have a factory error...

Currell, now you have ME confused. I pulled the head on the offset one (first time in over 40 years). The flat combustion chamber has a slot for the baffle on the bypass side and the baffle extends above the cylinder into the slot. If the plug was on the bypass side it would hit the baffle. Perhaps they redesigned the head. I got this engine when they were first released so it may be first run. BTW, I ran it a few days ago on the bench and it runs fine.

I exaggerated with the 1/16". Looking at the "centered" one at eye level, I can see four fins on the exhaust side and five fins on the bypass side of the plug. It is offset "half a fin" to the exhaust side. Perhaps because of the baffle slot (I didn't check). The fin positions on this version is different from the first. The spacing size is the same but the positioning adds a little meat to the first (side) fins. The outside edge of the fins also have a little larger radius than the first ones.

I hope this clears things up a bit.

>...George, you've got me really confused
>on this one. The offset
>plug ones are a full
>1/8" offset, to the bypass
>side. You have a factory
>error...
>
> Currell, now you have ME
>confused. I pulled the head
>on the offset one (first
>time in over 40 years).
>The flat combustion chamber has
>a slot for the baffle
>on the bypass side and
>the baffle extends above the
>cylinder into the slot. If
>the plug was on the
>bypass side it would hit
>the baffle. Perhaps they redesigned
>the head. I got this
>engine when they were first
>released so it may be
>first run. BTW, I ran
>it a few days ago
>on the bench and it
>runs fine.
>
> I exaggerated with the 1/16".
>Looking at the "centered" one
>at eye level, I can
>see four fins on the
>exhaust side and five fins
>on the bypass side of
>the plug. It is offset
>"half a fin" to the
>exhaust side. Perhaps because of
>the baffle slot (I didn't
>check). The fin positions on
>this version is different from
>the first. The spacing size
>is the same but the
>positioning adds a little meat
>to the first (side) fins.
>The outside edge of the
>fins also have a little
>larger radius than the first
>ones.
>
> I hope this clears things
>up a bit.
>
>George

George: You;ve got me completely confused now...

The second generation, 1/8" offset to the intake bypass side, vertical plug Steel Fin version (please be specific when you talk about these engines, George) is a reality. Take it to the bank. I'm counting 14 fins. They are kind of machined off (flat) at the top.

Now, compare it to a first generation, center vertical plug Steel Fin engine. I'm counting 13 fins, and the tips come to more of a peak, not machined off, compared to the 14 fin offset plug head. The two side fins on this center plug head are "fatter" than those of the offset head, too.

Sorry for my mistake earlier, saying that these heads were the same. (If you will excuse a personal reference, I just had some retinal surgery Saturday, and I am looking at the world with one eye right now).

I still don't understand what you have with your ever-so-slightly-offset-to-the-exhaust side .15. The center plug version is 3 fins on each side, with 7 fins being "interfered with" by the plug.

And I still covet it!

Currell (jealous in Shelby Twp MI)

Ok, now I REALLY have no idea what I have! One is the steel fin version, the other is the one piece case version. The first has a plug roughly centered, the other is slanted.

I agree that 2 oz should do it, sounds like something else is wrong. If you think 2 oz is too much, you should see what a 2.5 oz tank looks like on the nose of my Clown! I'll experiment with the two engines more carefully and see what's up.

I for one could really learn something from an illustrated "article" on the various versions of these and .35's.

Thanks for all the help for now, I'll go start gathering some more useful data so I can ask more pointed questions and get these things running. The little steelfin really starts nice and runs consistently, just kind of underpowered for now. Used some .15% at VSC and that really helped. May up the ante a bit and start from there. Didn't have time to really troubleshoot the newer .15, was having problems with it either being too rich or leaning out during maneuvers. I guess it's just being too sensitive on the needle. However, it seemed to have a lot more power. Didn't try anything other than the 10% I run in my .35's.

Later,

...The second generation, 1/8" offset to the intake bypass side, vertical plug Steel Fin version (please be specific when you talk about these engines, George) is a reality. Take it to the bank. I'm counting 14 fins. They are kind of machined off (flat) at the top...
---Mine has fourteen fins machined in the head but the plug is on the exhaust side. The combustion area is flat with a machined groove for the baffle. I bought this one when they first came out so I refer to it as first generation. I think they came in a tan box at that time.

...Now, compare it to a first generation, center vertical plug Steel Fin engine. I'm counting 13 fins, and the tips come to more of a peak, not machined off, compared to the 14 fin offset plug head. The two side fins on this center plug head are "fatter" than those of the offset head, too...
---This is the one that is very slightly offset on my engine. Perhaps it is a manufacturing defect. I was thinking of side profile when I referred to the fins as more rounded. I removed the head today and this one has a formed combustion chamber. It is curved on the bypass side and slanted on the exhaust side with the peak height at the baffle position. I bought this one used so I do not know where it falls in the Fox chronology. I ASSUMED it came after my other one so I referred to it as second generation.

...Sorry for my mistake earlier, saying that these heads were the same. (If you will excuse a personal reference, I just had some retinal surgery Saturday, and I am looking at the world with one eye right now).
---I hope your surgery went well. I can relate to using one eye. Had a cataract removed a couple of months ago. Used my best "pirate" voice when talking with my grandkids

I will try to take some decent pictures of them and put them up.

Thanks, George. I really look forward to seeing the Fox with the plug slightly to the exhaust!