Snowplane, radio gear

Hey Lieven,

I don't know if you can get these over there, but I have used the smallest Sullivan cables for throttles on all sizes of engines.  You can easily put a Z bend in the cable itself, hook it through the snap ring hole, and CA one of the threaded tubes on the servo end for adjustment.  It has enough flex to follow the throttle ring around the cylinder without stressing anything. The shroud may need a little support arm on the engine mount to help aim the cable at the ring.

I really like them because they easily flex around and through the crowded fuel tank area in the noses of planes.

Thanks guys for your contributions. Kim gave me an idea I'd like to try. I'm thinking of taking a bit of electrical cable, strip of the insulation and wind the strands nice and evenly. Then bend it 90°, poke it through the circlip hole from below and bend it again between the circlip and the muffler with a knife blade or something similar to get a Z shape. To strenghten it, I'm thinking of heating the cable with a soldering iron and let it impregnate with solder. The other straight end of the cable will then be soldered to a piece of music wire.

The problem with using the pliers is that you cannot use them again to fit the circlips. And to force that back over the aluminium taper into the groove might be a bit delicate.

The prop in the pictures is a Cox 6x3 prop. I just screwed it on backward. I don't know if it's the best choice.

Although we haven't got snow, I tried the engine today and made some trials to see if it would proceed at all. I tried it first on the lawn. After starting the Dagonfly, it moved only a little. The grass gives too much resistance. After a few runs, black goo was coming out of the crankcase behind the drive washer. When turning the engine by hand, There was play on the crank and at each down stroke bubbles were abundantly present. I decided to do an engine change and put the the snow plane on the drive way. The little stones would give less resistance. A bit of downhill helps as well!!

The engine started well and initially, the snow plane did go well. However, it suffers from the engine torque and turns automatically to the left. After a while , revs seem to be decreasing a little.



https://www.youtube.com/watch?v=KooNlBoS64M

Another video:



https://www.youtube.com/watch?v=me8tERTazpo

Thanks guys, for your comments and support.

I ordered a replacement crankcase assembly to rebuild the Dragonfly. I will glue keels on the bottom of the skis so the model resists better against the engine torque; I think Roddie mentioned that already before. The Call Air snowcar with the .35 engine has got them as well

http://www.rcgroups.com/forums/showpost.php?p=18221066&postcount=3894

Also I better fit a cable to the front ski to prevent it from going nose down and digging into the snow. I'm going to do that on the rear skis as well because the support is in fact glued too much to the rear of the skis: when you lift the whole thing up, the front of the skis go down. I also could glue a coin or washer to the skis' rear for balance instead. I only need about 8g.

Roddie, The prop in the video is an 6x4. I broke the old Cox 6x3 when stopping the engine with a rag.

The Leyat is an interesting vehicle and much info and documentation was preserved over the years, Not because many were made of but because it's such a unique vehicle. I saw one once in real life. It was during one of the Air cooled Days at Brooklands in april 2000 or 2001. If I remember well, it was a replica. They steer with the rear wheels, that's a bit dodgy and olso, in turns they lift one rear wheel. It would be a nice and interesting project Bob. I hope you'll start soon!!



Lieven

Roddie,

The Dragonfly was bought 2nd hand. I didn't know his condition. It's something you cannot tell from looking at the outside. It might have been started by an electric starter during its previous life or maybe run on fuel with synthetic oïl only. I don't know. As the word 1/2A is extiguished over here, I mix my fuel myself. I have Dyna Glo with 25% nitro, 8% synthetic oïl and 2% castor. With that I add 10% extra castor.

In one way or another, I have to make sure to front of the ski's don't go down too much when the surface is uneven. The points would easily dig into the snow that way. So, I need to come up with something like a linkage cable or a spring or a combination of both or a rubber band as Kari mentioned. Concerning the, keels, A depth of 3 to 4 mm would be OK indeed. I'll follow the kind of keels mentioned  on the Call Air plan. For the roof, I still need to make a lock for the hatch. The hole for the throttle connection will be behind the hatch, also still to make.

RknRusty wrote:I love it. I might have to copy it in case we get some snow. I could play with it maybe once a year, or even run the sprinkler on a freezing night to ice up the yard.

I have a question for you guys that run pushers. I noticed when one of my Bees started backwards, and I somehow didn't notice(I'm a little slow on the uptake sometimes), it began to bog and I had to turn it much richer after it first peakd to regain a full 2-stroke; I assume because the piston and cylinder begin to tighten from the heat. Do engines used like this have a significantly shorter life due to higher heat induced friction?
Rusty

Rusty, As mentioned in my post with the video's, I noticed that the revs went down after some running and I also had to play with the needle. I don't think the piston and cylinder tighten from heat. With the given clearances Cox made their cylinders, you would soon have metal to metal contact and seizing of both parts: the engine would immediately stop and cylinder/piston assy would be ready for the bin.

Because there is not such a forced air stream as with a tractor prop,  I think the cylinder expands by the heat and the compression will become less. You have maybe more blow-by and the efficiency of the engine goes down. Also, and I had this twice, after I had emptied a tank, the cylinder head could be unscrewed by hand, although it was done up before with a spanner. This might also indicate that the cylinder expands by the heat and this due to the exhaust gasses in the cylinder and the evacuation of exhaust gasses through the exhaust port.

By the way, and just to compare, on the Enya .09 and .19 marine engines, only the cylinder between the head and the exhaust port is watercooled and not the head itself. in this way, certain expansion of the cylinder is avoided:



On a Cox pusher, and definitely in my case with the snow plane, where there is a very reduced air stream, a heat sink will be necessary,  but more one that is clamped to the cylinder fins and not to the head. I'm going to try to make a heat sink and do a test.

Rod, I ordered a crankcas and crank with a hex drive washer in brass from Matt. I hope that this will restist enough.




Lieven

Here's a small update about the rear ski's. I managed to make something to lift the front of the ski's when they should leave the surface. It takes actually longer to think about it than to make it. It's done with  bolts an nuts and 2 rubber bands "borrowed" from my daughter's Rainbow Loom kit.

Good news. I received my parts today



I rebuilt the engine with a new crankcase and crankshaft assembly, a new tank gasket and I added a new snap starter. I left the 6x4 behind and mounted a 6x3 3 bladed pusher prop





I did some trials this afternoon. The difference is remarkable. It suddenly became a very fast machine. I hope I still can try it on snow this winter

This is with reduced throttle:



https://www.youtube.com/watch?v=bbuqstoPoQA

And this is full throttle (Birkin style) but not for long!!



https://www.youtube.com/watch?v=6PXTNaLRJAA&feature=youtu.be

Lieven