Muffler for Fox 25 baffle

Several years ago I snatched up a NIB looking Fox 25, model 12500. This is the plain bearing loop scavenged motor with a very shiny silver case, four bolt backplate and bolt on upright venturi.

First, is this a desireable motor for sport/stunt flying? I was thinking the Flite Streak or Ringmaster types or an OTS El Diablo (a hint for Walter U?).

Our club field has a muffler rule so I can't fly it without an effective muffler. I've had little success lately getting Fox to answer questions about parts availability for their discontinued engines.

Obviously a high castor only content fuel and perhaps a 9-4 prop?

Muffler recommendations?

>Several years ago I snatched up a NIB looking Fox 25, model
>12500. This is the plain bearing loop scavenged motor with
>a very shiny silver case, four bolt backplate and bolt on
>upright venturi.
>
>First, is this a desireable motor for sport/stunt flying? I
>was thinking the Flite Streak or Ringmaster types or an OTS
>El Diablo (a hint for Walter U?).
>
>Our club field has a muffler rule so I can't fly it without
>an effective muffler. I've had little success lately
>getting Fox to answer questions about parts availability for
>their discontinued engines.
>
>Obviously a high castor only content fuel and perhaps a 9-4
>prop?
>
>Muffler recommendations?

I have a few of these, they work OK on a skyray sized airplane.
if they have muffler lugs, a muffler for a fox 35, or an OS 40 FP (with a little work) will fit. I have used old dubro strap on toung mufflers.

I like a 9x4 on my motors. They do shake, and don't like 4 2 4 running. Also make sure the venturi does not leak. last time I needed them, I could get gaskets etc for this motor.

Dave

I had pretty good luck with those engines for sport flying. I used an early Fox 35 muffler. They went by letter back then, such as a Fox B muffler. But I can't remember if it was an A, B or C. I gutted the muffler, took out that aluminium insert. And put end caps on it. It took about 4 or 5 1/8" holes in the back to let out the exhaust.
I made a new intake which was longer and slanted forward, mostly so I could choke it. I ran a 10-4 zinger and 15% nitro on a Dumas Tomahawk. Just a fun plane, not a contest winner.
Happy landings

I picked up one of these years ago new. Broke it in but never used it. It came with a muffler. Doesn't FOX have a muffler available? Andy

LAST EDITED ON Jan-13-04 AT 05:40 PM (CDT)
 
>an effective muffler. I've had little success lately
>getting Fox to answer questions about parts availability for
>their discontinued engines.
>
>Obviously a high castor only content fuel and perhaps a 9-4
>prop?

I've owned a number of these over the years. This engine will pull 400-425 sqi fairly well. If my CAD program is right, the El Diablo is 430 sqi. So, in theory, it should pull it sufficiently on a wet 2 cycle with a 9-5 or 9-4 prop.

The weak link in these engines is the small, cast conrod. Apparently cast conrods worked well enough on the 15 that Duke put them in the 19 and 25 - with less than stellar results. This translates to problems if you are using other than all castor lube fuel or you have a couple of lean runs. Ask me how I know.... The con rod will hold up, though, if you are careful. The first one I bought back around 1973 or 1974 is still tight. Many that I see from RC flyers have clicking conrods. I can only surmise it is the fuel that is causing this.

BTW - the El Diablo plans are done and in Walter's hands. The parts file is also done and, when he gets back from King Orange, should be ready to send to the laser cutter. When I started on this project, I had the good fortune of running into Ward van Duzer at the Perry, GA show. Ward related that as a kid he flew with Red Reinhardt and Larry Scarinzi, and built a number of ships at their respective houses. He has some templates that he has kept all these years that are supposed to be very accurate in regards to the original, especially in terms of the trailing edges. He has graciously donated his time to reviewing the plans and correcting discrepencies with the MAN plans as well as making sure I don't make any mistakes. The construction of the wing and fuse are updated to facilitate building and the kitting process.

As usual with Walt's kits, the workmanship and wood selection will be exceptional.

Regards - Bob Kruger

Updated later: Just got off the telephone with Walt Umland. The laser cutter is making a test run tonight and will try to have the parts in Walt's hands before he leaves for KOI on Saturday. We did find two minor problems that are now being corrected, plus we will add some tabs on the ribs to facilitate building the wing flat on a board.

BK