hsukaria

The crazy things people do, like lead in the backplate... I bet some people have said that about me too.

If the thermal expansion rate of aluminum is greater than the thermal expansion of lead, by heating the backplate some would cause the lead to break loose from the aluminum backplate way before melting begins. That's the theory anyway. That may explain the presence of glue at the seam. Maybe it broke loose and the previous owner glued it back in. That would make it easier to remove. I will try it tonight. I am also looking forwards to running it this weekend. It worked out that I can get by with only a one-piece adapter since the OS muffler bolts are so much wider than the Fox's.

hsukaria

Ok, I got the lead out. I had to drill half of it off, and the rest came out by hitting the backplate facedown against the workbench. I have borrowed the TN carb from the 74 for testing until the MKx gets repaired. I built an adaptor to use an OS muffler. I still have to cut open the adapter to match the muffler/engine opening. Now if I can get it to run....The final weight with muffler comes to 16 oz.

Zor

Good man hsukaria.

hsukaria

I did try to heat cycle the backplate by using a heat gun (for heat shrink covering) and then dropping the backplate in a bucket of water. It did not help before I drilled out part of the lead. It might have helped loosen it after removing at least half the lead with a drill gun. Unfortunately, I did scrape some of the aluminum in the backplate with the drill gun, but not too bad compared to the rest of the engine. Also, the gasket for the backplate got all chewed up. Maybe I should use some high temp RTV for sealing?

1QwkSport2.5r

Use an index card or something like that and cut your own. The crankpin might rub the backplate.

hsukaria

good idea, I didn't think about the crankpin rubbing the backplate.


The one misgiving I have about using that muffler/adapter combo is that I will have to carve the exhaust opening slightly smaller than the engine exhaust opening because the muffler opening height is shorter than the engine opening, even though the width is much greater. It might mean having to remove the baffle in the muffler to compensate.

1QwkSport2.5r

I would contour your adapter to flow as cleanly as possible and not worry about the outlet of the engine size versus the muffler opening. My Jettstream .46 pipe I have for my TT .46 has a smaller port than the engines exhaust port by probably 20%. Dub assured me there wouldn't be a difference in performance due to the smaller port in the muffler. I'd run the engine open faced to get a baseline reading and install the muffler and do another run and note the rpm. You would likely see a bigger difference in open exhaust rpm versus a stock muffler than you will with the stock muffler versus the OS muffler if the overall shape and volume is similar. I have pictures of my muffler adapter I made for my Fox .40 to use a TT .46 stock muffler somewhere in this thread, I'll see if I can find them and link to them so you can see what I did. I had to offset the muffler aft by a 1/4" which moved the port of the muffler back quite a bit. I just ground the adapter to flow as smooth and cleanly as I could and it worked quite well.

hsukaria

The adapter I made up (it shows a bit in the above pictures) is all set up except the exhaust opening. The bolt holes are all drilled and functional.

1QwkSport2.5r

Looks fine to me.

earlwb

It looks good to me too. Do let us know how it goes. I think you have it.

The small case .40 engines were pretty neat actually. They were slightly larger than the .25 engines but smaller than other .40 size engines. So it was possible to use them as a performance upgrade for many .25 size planes. But when you wanted to use them in a .40 size plane, then with the engine being smaller and more light in weight you had to add lead to the nose of the plane to get the CG to come out OK. But seeing someone fill the backplate up with lead is new to me. It isn't a bad idea, kinda different or strange, I never thought about trying it myself.

1QwkSport2.5r

Off Hsukaria's subject briefly... If any of you Fox gurus want to own a piece of Duke Fox memorabilia, my Fox twin is going for sale. It has unbelievably good compression and does run. Has the butterfly carburetors, Y fuel line fitting, and engine mount. It came with low compression high-nitro heads from the factory and I made a matched set of high compression low-nitro heads for it. If anyone has any interest, please PM me. If I don't get any bites on it here, it's going up on eBay.

And now back to our regularily scheduled programming...

p.s. I will be making a muffler adapter for my Fox .19RC soon. Anyone got a picture or guesstimate on size of the muffler that's supposed to go with the .19RC?

hsukaria

Regarding a muffler for the 19, if not a Fox, you could probably find a bunch of old OS mufflers at swap meets. That is how I got the one mounted on the Fox 45.

I bench ran the 45 this evening and at first it was hard to start. But after a while, it was easy to start and had decent performance. I could not use the tach because it got dark. I worked on the throttle response last and it still seems rich because of a slight delay on throttle up. I was using a 10x6 wood prop, Fox Miracle plug, and 0% nitro with a bit extra castor oil (approximately 20% oil synth/castor). Overall I think the engine is pretty good.

I will try an 11x6 prop tomorrow with 5% nitro and hopefully tach it too. That OS muffler wasn't too loud either.

Here's a video (I think) : http://youtu.be/l2JBb5rrjGQ

Update:
I ran the fox 45 with a Master Airscrew 11x6 plastic prop, 5% nitro, with the same glowplug and muffler as before. The maximum sustainable rpms I could get was 11K rpms. Sometimes I could tune it a little higher, but it would not maintain that speed. I suspect this engine needs a new piston ring. The bearings are not as smooth as my other engines either, not gritty or scratchy, but not smooth. The little nitro helped with the throttle response considerably, it is now excellent.

carddfann

This might be old news to some, but I saw on a CL post from earlier in the year that Fox is going out of the engine business. There was a brief letter supposedly from Sharon that said basically in tuff lean times, chinese imports, and so on that they need to refocus their smaller staff on other business that's more profitable. I know their engine business can't be that profitable in a lean hobby industry but anybody here heard this too and is it true? If so, I hope things turn around and they start making engines again. I think I need drink
If there's truth to this, I hope they keep making their other hardware and plugs.

1QwkSport2.5r

Sharon told another guy I talk to more recently that they are not getting out of model engines altogether, they just aren't making any engines for a period of time likely longer than shorter. So don't expect anything from them for awhile.

1QwkSport2.5r

My Fox .50 has been through 2 different sized Bowman piston rings. The ring seal was OK to start with (Fox ring) and got worse the more I ran it. New Fox .50 ring from Bowman was too thin. Installed thicker Bowman ring and the ring seal got worse. Initial cylinder wear was minimal, though the liner wore more causing the ring seal to diminish more to have nearly zero compression. Today my buddy Todd and I pulled a crashed MDS .40 apart and measured the parts to see if they'd fit the Fox. They do and it runs!

Parts list:
a 10gal MDS .40 ABC piston/liner set; wristpin bore in piston bored to fit Fox .50 wristpin
MDS .40 cylinder head sans head shim
Fox .50 conrod
custom wristpin & retainer
custom liner shim (Guinness beer can)

As assembled, it has a .828" bore and .790" stroke which equates roughly to .425 ci.

Very first run, taken at midnight, of the FDX .43 hybrid conversion engine. http://youtu.be/U65jE-Ycy3Y

74SEVEN7

Can anyone help me out ? I bought a near new 1972 FOX FALCON 60 (that's the last of the plain bearing 59's with the shiny case) but a small, cast metal piece on the carb is broken. It's the idle stop arm, which has an adjustable screw on the end. I bought one of the later flange mounted throttles, but of course, the arm on it is different. The FALCON carb has a spigot and is held in place by two grubscrews. Perhaps you bought a FALCON in the early '70's and replaced the FOX throttle with a Perry ? If so, I'd like to hear from you. Thanks, BOB

earlwb

Well, maybe someone will happen to have one. I don't think that they made too many of the old .59 RC engines, so there may not be a lot of them around. But you could use sand casting and make a new part. You could even make the part by machining a new one too. Although using a milling machine and or a lathe would work best, you could make it the hard way with hand tools and lots of patient hand filing.

hsukaria

I hope that as a minimum, they get to producing the Miracle plug. That is useful on most engines.

hsukaria

were you able to tach the FDX (a.k.a. FrankenFox)?

1QwkSport2.5r

No, not yet. Too busy at work, and the weather has been really windy. Hoping in the next couple days I'll get "Frankie" out and wring it out. If the forum behaves, I will add some pictures.

We were very surprised to see the MDS head fit the Fox without modification but the fins are clocked slightly. When we get time, we will mill the block down to drop the liner which will get the piston stopping at the original "top" of the liner. Right now due to the slightly different wristpin height and longer stroke, the piston is .036" short of the head and the piston goes below the bottom of the exhaust port in the liner by at least .035" or more at BDC. But time will tell as we run it and modify it as we see fit.

hsukaria

maybe all that won't be so critical if you end up converting it to a diesel anyway. By the way, if you think gasoline engines smell bad, wait till you try the diesel!!!

1QwkSport2.5r

I won't modify the diesel head to fit any other liner, the MDS liner is about .070" smaller in the bore than the original Fox liner (.827" vs. .906"), so it will likely run like this for awhile until we get the new piston cut for the Fox .50 liner. I think we are gonna convert the .50 setup to a homemade custom lapped meehanite ringless piston in a steel liner. Should make for a stout diesel bark.

Diesel exhaust does stink, but the fuel itself isn't too horrible. I find it less annoying than gas personally. It is something different though.

hsukaria

I have some newbie question regarding machining for these engines: Did the outside diameter of the MDS liner match up exactly to the O.D. of the Fox liner? I am dealing with a similar issue with another engine (not Fox brand) that has a peeled liner and replacement cost is quite high. So, I am looking at ASP brand piston/liner set that is true ABC and is dirt cheap. I would also consider a ringed piston/liner set as well if there are any available. But I don't know if it will work unless I buy the p/l set and start hacking.

So, what I am getting at is: There are cheap p/l sets out there and it would make more sense to me to machine the crankcase and head (non-diesel) rather than fabricating my own piston and liner, provided that the generic p/l fits at the crankpin also.

1QwkSport2.5r

The MDS liner was .005" smaller in O.D. than the Fox .50 liner. That's where the Guinness beer can comes in. The beer can was .005" thick, so I cut a piece the length of the liner and wrapped it around the liner without the ends overlapping. I used a hobby knife to cut the ports into the beer can shim. To use a different P/L set, you need to find a liner with close to the same O.D. as the original liner. I wouldn't bore the case to fit a larger O.D liner as that will shrink the port channels in the case. If the junk engine's for is good, plan to use it. Hopefully the wristpin is the same size in the ASP piston - if the wristpin is smaller in the ASP, then you just bore out the wristpin bore to fit the larger wristpin. Keep in mind you would either need to cut new circlip grooves in the piston or find an alternate means of retaining the wristpin. If I were to hazard a guess, I'm sure the wristpin will be able to catch in the transfer port if it came loose.

So essentially, you need to know the O.D of the new liner, wristpin size comparison, wristpin retainers, and if you have to modify the piston skirt to clear the crankshaft counterweight. The cylinder head may need to be modified to fit the bore if an ASP head won't line up with the junker's screw holes.

aspeed

I am assuming that you are talking about an OS with the peeling liner. The older FX is similar to the ASP/Magnum liners and is reported to be an easy swap. You need the correct model to fit right. M or whatever letter is right. Not sure about the AX motors. http://www.rcgroups.com/forums/showthread.php?t=1862693 Different forum, hope that is ok.