Corehouse Models

Godsey are you a brass player?

Wow. I ad no clue this engine could spin that fast. What would have been desired to cut out the slot in the back? The slot is completely round and natural looking. I would have guessed it came from the factory like that.

I am a brass player. Trumpet and French Horn are my prefered instruments. I was in a hurry to take the pick so I placed it on my Trumpet case. I am actually first chair trumpet right now. I only play French Horn as a hobby I guess. Never really played it in band.

Rolla

Oh fine me too. I saw that Yamaha-Case

I've got an Olds Ambassador Trumpet and playing for fun.

Do you have a picture of your instrument? I have only seen two Olds instruments. One was a Trombone and I cannot recall the other. I have been told that they were good instruments in their day. Along with Conn.

Rolla

Rolla, ideally for combat, you want the back of the engine to be right up against the leading edge or even sunken into the leading edge. Having the twin horns, placed the hot exhaust over the top and bottom of the wing. Even rear exhaust engines like the VA engine can burn up the airframe or melt the foam and a needed piece of aluminum foil is typically used to prevent this. That cutout may have been stock, I just never seen one. If you had to prime the cylinder which is typically only a drop and that's with the piston above the exhaust port, it's difficult to do through the horns. That cutout is a direct shot. Ken

Finally managed to maiden the Hacker. It flew very nicely. I was a little worried flying it because it has been some two months since I have flown. But apparently flying ability does not fade that quick. I had not issues with it. I am going to now start working on the second one to fly with the Stels.

Rolla

Yikes! Did Phil have ANOTHER flood?? I thought he had one last year (i.e. late 2011/early 2012). Hope it's dried up by now.

A few notes - Slow Combat was actually flown using the same engines as Fast Combat - early on, Fox Combat Specials of various sorts and in the end, Nelson .36s. It got faster and faster and faster (just like Fast), in the end reaching speeds of 90mph or so with the Nelsons. By then it had gotten ridiculous - the models were big (rules said 24" overall length, 5" nose moment), fragile and required a hard tank (expensive - a GRW 5 ounce chicken hopper would set you back $25 and didn't last very long - people would bring generators and soldering guns to the field for tank repairs between rounds). The suction rule did mean the planes were slower than in Fast Combat but it really was Fast Combat Part 2, and had long outlived it's purpose as a beginner's event.

Remote needles - yes, the OS needles worked nice with bladders, but one really good reason to use them is that you won't break a needle in a crash. Mount them so that they're out of harm's way, i.e. they don't stick up where they can get knocked off.

A 550 sq. incher will fly nicely with a .25, just not as fast as a 450 sq. incher. Which is fine for sport flying.

Iskandar

A couple of other things. Be careful with that Stels, don't know why someone would take a chunk out between the exhaust stacks like that. Priming these things was easy - you squirt fuel down one exhaust, it drips out the other, and you don't end up with a flooded engine and just about enough prime for starting. The problem now is that the exhaust will blow straight back. What's there? Your wing's leading edge. Back when I was flying VAs we'd put a piece of aluminum flashing on the leading edge right behind the exhaust. One day, the aluminum came loose. The exhaust melted its way into the model, and actually burned off all the epoxy on the front of the tail boom, leaving the fibers. When I landed, the front block was still attached to the boom, but by a bunch of glass fibers. Kinda flopped around.

Fox .35s - believe it or not, they run nicely on pressure. Use the OS .15 remote needle valve as you would on a Combat Special. I set one up like this because there were one or two Fox .35 Stunt combat meets I attended. You could get them to go fairly fast, about 70-75 mph - the trick was to use a much smaller prop than people tell you to use - a 8x6 worked OK. There are various racing classes around the country that uses the Fox .35 Stunt - these guys can get them up to 100 mph using 8x8 props and some major tweaking and careful lapping and break-in. They also get them to restart well, too, how, I don't know. If you've ever had a look inside a .35 Stunt, they kind of look "wrong" compared to more modern engines - that what happens when you have an engine designed back in the 50s or 60s.

Iskandar

Ken Cook wrote:            Rolla, you have a somewhat extinct twin horn there. Absolutely beautiful piece. Someone however modified the back of the case probably so they could quickly prime the cylinder. That cutout, looks like it was done very professionally but it doesn't exist on the stock configurations that I own and have seen.  That engine  is capable of 30k+ all day long. The previous owner also was aware of the consequences if the stock screws holding on the cylinder does if left on. I see they've been replaced with small socket heads. The cylinder will break the heads off of the stock slotted steel screws. These didn't come with plugs to later so they were originally offered without plugs but the 1702 Cox was the plug of choice. A Nelson Galbreath setup will gain many more rpm's with duration. Doug Galbreath suggested breaking these engines in using 40% nitro for a few minutes and then you were pretty well unlimited on what to run. The engine favors at least 17% oil. These engines don't require a lot of castor like a Cox. Yes, that engine will not run on anything but a pressure bladder. I do have the instruction sheet for that engine if interested. Engines in that condition I've seen on Ebay bring a pretty good price ranging from $60-$80= dollars. I would say at $20 you have a nice piece. Keep in mind however, parts are not going to happen as there just isn't any available aside from needle valves spray bars and plugs. Stels did make inserts for some of their side exhausts which would fit that bathtub opening. These were made in grey, black and a white nylon. I believe all were the same I.D. for the venturi throat. Supposedly, this would allow the engine to be run on suction but I feel it was waaaay too large as well even with the insert. It also appears to be a later model as the base of the cylinder has a thick wall to it. The earlier models had a thinner area there and this would also distort and fail allowing the cylinder to blow off of the top. I would certainly run it. Amazing power and a great sound. Ken

Thanks, you provided a lot of useful information about the stels. I purchased a new one not long ago. It is very nice. It is identical to the one pictured above, with a few notable exceptions. Mine has a glow button attached with a clamp; I have a different needle valve and spray bar. My needle is round and made out of a bronze colored metal. The spray bar is very thick and covers almost half of the Venturi entrance. Finally, the cylinder is a smaller diameter. The base of the cylinder is the same thickness, however, when I put a cox glow head on the cylinder, the cooling fins hang over the edge. I have the same socket head screws holding the cylinder. Do you know if this is the older version that is prone to loose the cylinder? Thanks for any information. Andy

Hello Andy, you have a real runner there. These are excellent engines. My advice is run them until they no longer run and then make it a shelf queen. The needles do lack sensitivity in adjustment. My advice is to run it on a low pressure bladder tubing (Latex) and go fly. The Cox high comp head is what was recommended for the engine. Back in the early 90's these engines didn't come with any glo head. Doug Galbreath would perform a bit of massaging on these engines and he would equip the engine with a Nelson plug and adapter in which he would automatically swap out the screws. Stels did indeed provide a glow button for these engines on their later models which did indeed work quite well. They're hard to locate nowdays and the Nelson Galbreath is readily available. The screws that hold the cylinder onto the case are slotted steel screws. If you still have the slot head straight screws I would change them. Socket head cap screws can be purchased at any hobby shop that deals in r/c car use. Dubro sells the screws in packs of 4 . I believe the diam. is  2.5 mm but I would bring the screw to check the length.

Currently, there's no source of spraybar needle valve assemblies. The needle assembly on Rolla's engine in the pic above is not the stock needle that came with that engine. It in fact looks like a Rossi or even a early Cyclon variant that Doug Galbreath use to sell.  Larry Driskill sold out and even his assembly wasn't a retro fit due to the case needing to be drilled a few thou wider. A Kustom Kraftmanship needle could be made to work if you have access to a lathe or have a friendly neighborhood machine shop that could provide you with a bushing that fit the case and the needle assembly itself. Recently, I've been toying with some ideas and I will post some pics of how I make an adapter to fit these cases that can utilize a stock TD venturi needle valve assembly. It will undoubtedly cut a bit of power down due to the fact the maximum hole in a Cox venturi without breaking out of the stack area and into the sprinklers is 5/32". As you can see the stock hole in the Stels case is almost twice that. This however would improve needling and fuel draw and still should be an excellent runner. The quality of the Stels far exceeds the other variants and I found the Stels to run in the 30K. The Stels and the VA MKII are the only .049's that are bushed that I found to break into the 30k area.


Please post your plane and success if you pursue building and using one of these engine. I do have a letter from Doug in regards to how to break this engine in. From memory it starts off, break in engine with 40% nitro and run for 2 minutes. Do this for a total of 10 minutes or until the black oil ceases. After some more ground runs the engine can easily switch to even higher nitro if desired. These engines don't need the castor oil that the Cox engines require and I've run these engines with oil contents 18%. I would suggest a quality fuel like Sig in the 20% oil content range. Ken