Author Topic: Fox .15s not for hurling (Read 5984 times)

Larry Renger · « **on:** December 11, 2015, 08:03:15 AM »

I ran two early steel fin Fox .15s yesterday. They were donated to the Knights of the Round Circle, and needed extensive cleaning - Crock pot, scrub brush, etc.

I "tweaked" one of them with a bit of bypass and crankshaft flow clean-up (no timing changes) and polished the crankshaft and crankpin bearing surfaces, the other is stock. The cleaned up one ran 13,800 the stock one 13,500 both on 15-25-3 fuel and a Rev-up 8x4 prop. Pretty good for an ancient design like that!

The tweaked one has much better compression, and will hold rpm within about +/- 25 rpm in a rich 2-cycle, and can hold near peak indefinitely. It actually did a 2-flip start ..... once.

The other one is much harder to start, but also runs stably. It is clearly pretty worn out as it "bleeds" a bit of fuel out the nose of the crankcase and compression is noticeably "leakier".

The tweaked one's crankshaft runs very slightly warm, so it is probably still too tight. The other one runs cool as it should, but I guess the leakage is the price you pay for that.

Neither one hot restarts worth a hoot, total lack of hot compression.

I plan to dig out a Cox Medallion .15 for some comparison running. (Guess what I am putting my money on!

)

We got a Flying Clown with one of the engines (Thanks Barry Baxter!), so that is the "goat" I plan to do flight testing on. Eventually, the "winner" will go in a Jr. Nobler.

Brett Buck · « **Reply #1 on:** December 11, 2015, 12:38:27 PM »

Quote from: Larry Renger on December 11, 2015, 08:03:15 AM

I ran two early steel fin Fox .15s yesterday.

OK for casual backyard hurling or training, but not permitted for official Hurl Competition. Rule 4a, b, c.

Brett

Ken Burdick · « **Reply #2 on:** December 11, 2015, 03:19:21 PM »

ditto that Bret.
I had a new steelie Fox .15 last year. Built a Flight Streak Jr. for it.......looked nostalgic as heck. It ran for about 3 min as it progressively blew the head gasket........
sent it to a friend for hurling

K

Larry Renger · « **Reply #3 on:** December 12, 2015, 07:27:13 AM »

Actually, the head on the tweaked one did come loose after the first run, but I tightened the heck out of it (new, hex bolts!) and it seems fine now. I found I have 2-1/2 Medallion .15s and one Tee Dee. Fun to come!

BillP · « **Reply #4 on:** December 12, 2015, 09:24:06 AM »

Is that 15 nitro/25 castor/3 synthetic?

Brett Buck · « **Reply #5 on:** December 12, 2015, 11:58:34 AM »

Quote from: Larry Renger on December 12, 2015, 07:27:13 AM

Actually, the head on the tweaked one did come loose after the first run, but I tightened the heck out of it (new, hex bolts!) and it seems fine now. I found I have 2-1/2 Medallion .15s and one Tee Dee. Fun to come!

Does the Medallion 15 run as perfectly as the .049? Because the .049 is far and away the smoothest and steadiest running small engine I have ever seen.

Brett

Larry Renger · « **Reply #6 on:** December 13, 2015, 09:44:21 AM »

Quote from: BillP on December 12, 2015, 09:24:06 AM

Is that 15 nitro/25 castor/3 synthetic?

Yup

Larry Renger · « **Reply #7 on:** December 13, 2015, 09:48:10 AM »

Quote from: Brett Buck on December 12, 2015, 11:58:34 AM

Does the Medallion 15 run as perfectly as the .049? Because the .049 is far and away the smoothest and steadiest running small engine I have ever seen.

Brett

We'll see. I had one complete engine and put together a second one from parts. I need a few bits to finish a third one. The Tee Dee looks good as is.

Larry Renger · « **Reply #8 on:** December 17, 2015, 08:02:32 AM »

I ran the two Medallion .15s yesterday. What a difference! (no surprise, really). The better one was 1000 rpm better than the best of the Foxes, and started WAY easier. The other one was "only" 500 rpm better than the Fox and somewhat harder to start than the better Medallion, but still easier than the Foxes. I think the less good engine has too tight a piston/cylinder fit, as it will not run very steadily, and will "run away" lean. The crankshafts run cool on both engines, and don't bleed fuel out the front, so they seem to have a perfect fit.

More after I do a teardown and possible lapping on the second engine. It could be varnishing, rather than fit.

I was amazed to see that the running setting on the needles was about 7 turns open! The small Cox engines usually are half that.

I think that Bill Atwood designed these engines, but possibly Dale Kirn adapted Bill's basic Tee Dee design. I was not at the company when these engines were developed, and I suspect there is nobody left who was.

kenneth cook · « **Reply #9 on:** December 18, 2015, 03:22:29 AM »

As much as I like the Medallion engines, the fifteen size has been very problematic for myself. I'm not the only one who's experienced the piston seizing in the bore. The engines were running on all castor fuels 10% nitro and had hardly any run time on them. The piston crown would catch in the exhaust port causing a very abrupt stop rendering the engine useless. I was fortunate prior to Henry Werner retiring from Virginia Hobbysports to obtain several new cylinders and pistons. Of the 2 I owned that suffered the same fate, these were the thinner wall cylinders. Henry's replacements were the thicker walled and I never experienced any issues with these. I would say if you've been running them without issue, I would have no worries. I've discussed this with others that also had similar issues and without seeing the damages of my engine, they explained exactly what happened to their engines and it was similar. I don't know if this was caused by poor fits or the metal growing prior to breaking in, but it was upsetting nonetheless. I like these engines although they're really loud. Another factor that I discovered was that they like to catch fire easily. Priming should only consist of a drop or two and all spillage cleaned up prior.

Frank Imbriaco · « **Reply #10 on:** December 18, 2015, 08:47:37 AM »

I've got a Fox 15 that I bought new as a kid in the mid- sixties. Bench run only back then. I've always resisted selling it because I'm now a softy for the old days and memories. Sob. A Medallion, no doubt, would have to be much better.
At Brodaks in 2011, Bill Hadden ( spelling ?) from Colorado had a little clown with a Fox 15 in OTS. I launched it and read him the pattern .Damn, if that thing didn't perform great and it made me want to do something with mine- but .36 size vintage (silk & dope) combat ships, electric powered stunters, , R/C pattern birds and vintage tether cars keep me too busy to get something together for it. Hearing all of this is a bit disconcerting.
It'll probably remain in the box.

tom hampshire · « **Reply #11 on:** December 18, 2015, 10:02:17 AM »

Frank, I have Lil Dynamite plans.... Free!

Larry Renger · « **Reply #12 on:** December 18, 2015, 11:15:53 AM »

The Flying Clown would be my choice (that is what one of the engines was mounted on). John Wright has a number of trophies he has won with a Clown. As it is a standard race plane, it shouldn't be hard to get plans! Solid LE and TE, Profile fuselage, simple elevator control; makes for an easy, quick build.

C.T. Schaefer · « **Reply #13 on:** December 19, 2015, 06:48:29 AM »

Frank, Don't believe everything you read on the interweb. We have been flying a .15X on a Jr. Ring for a couple of years and it works great. It likes to rev so a Master 7x5 works well. A light ( 16oz or less) Clown would be good. Or, maybe, the TH suggested Lil' Dynamite. I assume that's an LS. He would love it, eh?

Frank Imbriaco · « **Reply #14 on:** December 20, 2015, 05:54:30 AM »

Toms:
I think its gonna find a home in something speedy. Maybe my first clown ?
Thanks

proparc · « **Reply #15 on:** December 21, 2015, 10:53:26 PM »

Quote from: Frank Imbriaco on December 18, 2015, 08:47:37 AM

I've got a Fox 15 that I bought new as a kid in the mid- sixties. I launched it and read him the pattern . R/C pattern birds and vintage tether cars keep me too busy to get something together for it.

You can always fly pattern with the .15.

Larry Renger · « **Reply #16 on:** December 22, 2015, 08:18:30 AM »

Quote from: proparc on December 21, 2015, 10:53:26 PM

You can always fly pattern with the .15.

Hey, Milton, I turned in a 509 at the Golden State Championships with a .15 size profile model. In decent weather they are as good as anything! Oh, BTW, the judges were Dave Fitzgerald and Bob Whitely.

Frank Imbriaco · « **Reply #17 on:** December 23, 2015, 11:06:40 AM »

Quote from: proparc on December 21, 2015, 10:53:26 PM

You can always fly pattern with the .15.

Proparc :

Just in case you are confused about my post , read on.
Years ago, we started calling it the "stunt pattern" and still do . Now a days , "Pattern" on it's own is a term most often associated with R/C aerobatics.
The maneuver groups( Novice, Intermediate, Advanced, Masters and FAI) in R/C pattern are referred to as "sequences".

When I commented that I read the OTS "pattern" to Bill who obviously was flying ukie , that is the current day norm.

proparc · « **Reply #18 on:** December 23, 2015, 11:16:10 PM »

Quote from: Frank Imbriaco on December 23, 2015, 11:06:40 AM

Proparc :

Just in case you are confused about my post , read on.
Years ago, we started calling it the "stunt pattern" and still do . Now a days , "Pattern" on it's own is a term most often associated with R/C aerobatics.
The maneuver groups( Novice, Intermediate, Advanced, Masters and FAI) in R/C pattern are referred to as "sequences".

When I commented that I read the OTS "pattern" to Bill who obviously was flying ukie , that is the current day norm.

I meant RC pattern!!

Bill Adair · « **Reply #19 on:** December 24, 2015, 01:27:56 PM »

I have a couple of very nice Fox 15X engines, and plan to run them on the bench (as soon as it quits raining, and warms up here in Portland)! Both are apparently in good condition, with snappy compression and no visible damage.

Out of curiosity I Pulled the plugs to test them, and found both are long plugs of unknown manufacturer.

The engine reviews I've read indicate that these engines were delivered with short plugs.

Before I pull the heads to check the plug reach, does anyone know for sure what is recommended by Fox, or what users prefer?

Thanks for any info, and Merry Christmas to all.

Bill

dennis lipsett · « **Reply #20 on:** December 24, 2015, 01:50:48 PM »

The Fox steel fin and 15X were both designed to use a short plug. we use to use 2 gaskets if we didn't have a short. They are not generally available anymore with Fox, Fireball and K&B being the only 3 brands that I have in my pile.
Turn the engine over slowly with your long plugs and see if you feel a light tap at top dead center if so the piston is hitting the plug. An idle bar plug is definitely not going to work either.

Dennis

Bill Adair · « **Reply #21 on:** December 24, 2015, 04:12:15 PM »

Dennis,

Thanks for your very informative reply.

Both engines turn freely, with no indication of the pistons hitting the plugs.

I have a few K&B 1S short plugs, but I wonder if the plugs already in these engines are Enyas, OS, or other Japanese intermediate length plugs? There is only one plug gasket on each, so I'm going to compare them to the Enya and OS long plugs that I have.

Merlin also lists short plugs, but I don't have any of those.

Bill

Richard Logston · « **Reply #22 on:** February 18, 2016, 08:55:10 PM »

Back in the sixties I had a Tri-Squire powered with a Fox 15 RC. It ran very well, good idle and transition. Easy starting. Must have got a good one. Of course RC made different demands on the engine. It had the old Royal three position servo's, anyone remember them? They were an improvement over the rubber powered escapements! Richard