I am starting this to see if this can pool some knoledge on anything useful for 1/2as. First, I am adding the following hint for The Cox TD, or Medallion engines.

If you have a TD or Medallion, before fueling for flight, rotate the engine clockwise till the piston closes the port. Now , keep it there, and fuel away. This prevents flooding the engine even if fuel goes into the carb, it will only overflow the venturi. I often do this, then use the fuel in the carb to prime the engine. Works good, and stops flooding the crankase.

Remby

Here is another, a bit more involved.


This is a description on how to get sub induction from a Cox, "slit exzaust" type of cylinder. These cylinders normally did away with induction for Muffler, & throttle adapters. However, a loss of 20-30% in power is a large cost, so if you have the need for more power, perhaps this will give some aid. This has been tested and works well, however I am sure this is not the only, or even the best method.

This requires a couple of hand tools, and a small nylon twist tie, and about 1/2 hour of time.. I have done this engine mod. on a few of mine, and it works very well. One engine with the mod has been in use now for over 20 hours and works fine. I first did this on a older, worn cylinder to see if it worked, and it gave that one new life and added that old style power. A couple words of caution to the young (or young at heart) are in order. First, if you have doubts, get some help, and/or try it on a older, used slit type cylinder to see what is the work involved. You could make the cylinder unusable if you damage the bore, or even injure yourself. So, if you are unsure, don't try it without help. The mod can not be undone, and will probally make mufflers/throttle sleaves run a bit less reliable, so should be done on engines that will run (Full tilt) until the fuel is gone. So, if this sounds good , give it a try.

First, the tools needed are...

(2) Hacksaw blades (both used without handle).
(1) Regular screwdriver, about 3/16" wide blade tip.
(1) Nylon twist tie.
(1) Cox slit type of cylinder.
Small amount of alchol for cleanup
Fine steel wool
light machine oil
couple of paper towls
black permament magic marker (optional)

1.- Test fit your Cylinder with it's piston, this gives a reference for how it should feel after the mod is completed. Now, working with the cylinder. The small cut is done to widen ONE of the lower slits (closest to crankcase). First, attach the nylon twist tie around the cylinder below the slits. Insert one hacksaw blade in one of the lower slits, only insert it upside down. This first blade is used as a guide. The second blade is placed on the cylinder, right against the other blade that is in the lower slit. Slide the nylon twist tie against the blades as a lower guide ,this helps prevent the blade from sliding around marking up the lower part of the cylinder. The cut is made right beside the lower slit, the idea is to widen the slit. Start cutting, holding the upside-down blade in the slit, let the cutting blade ride right against the upside down one in the lower slit. just let the blade do the work, and check often as it usally goes quite fast, even by hand. Wear eye protection , and gloves to help prevent cuts. Keep cutting until the new cut is as deep as the stock slit on both sides of this one slit. After you get this far, don't go any deeper as this step is now complete. Remove both blades, and the nylon tie.

2.- Next, take the flat screwdriver, and remove any extra steel from the enlarged slit. This must be done CARFULLY from the inside of the bore, go around the edges the new cut to clean off any extra bits of metal. Make sure NOT to hit/scrape the driver on the bore itself, just the slit's edges that must have thin hanging steel bits, they must be removed for. After this is done, drop the cylinder in a plastic cup of alachol. Swirl it around to remove the debris. Remove it and dry it with the towels.

3.- After it is checked and confirmed clean, carfully test fit the piston. If it stops, of you feel any grit, carfully remove it and check for burrs, or bits of metal. Repeat step 2 , then recheck the piston fit, it should feel the same as it did prior to the mod. Keep doing this until it is no different than before you started.

4.- Now use the steel wool and go over the inside of the bore, this will find and remove any minor bits of metal, and is easy to do. Reclean in fresh alachol, then dry the cylinder. .

5.- The magic marker can be used now to cover any unwanted scratches on the cylinder, this is optional, but covers any scratches well.

6.- Now light oil, the reassemble the engine.

This mod is great for those without machine tools, being all hand tools are used just aboue anybody can do this , Work slowly and make sure to clean the cut area well . If done as described, you will get that older Cox cylinder power, a noticable bit of improvment to your favorite model. Again, this mod works and is relible, but perhaps it's simple method is not the best for those interested in speed or racing, Then again ...

The picture shows the cut area on the one slit.

Hope others may find this as useful as I have...

Remby

Remby,

Good show!!!! If this mod is done on a newer twin flute twin bypass cylinder it will end up just like that of the Killer Bee. The twin flute bypass is pretty good porting. I trim .010-.015 off the skirt of the piston myself.

Later,
Tim

OK Guys here is one on dope finishes on the balsa models that I use. On the smaller models the thin balsa 1/6 tail surfaces tend to warp because of the shrinkage when using butyrate (Fuel Proof) dope and also will blemish/come off with the 35% fuel. I use the nitrate dope that does not shrink but is not fuel proof. After I do all of my painting, sealing and trimming I put on 2 coats of the Monocote Lustracoat. It is fuel proof and has limited shrinkage and goes over the nitrate quite well. After sealing the wood with the Nitrated dope and sealing it with the Lustracoat I have experienced no warpage on any of my small models and no fuel damage to the finish. Try it you will like it!!

Bob Harris
Early RC Models
www.earlyrcmodels.com

Cheaper than Lustercoat, I suspect, is Minwax "Helmsman" Spar varnish. Fantastic gloss, fuelproof, spray can application! UV coated too!

Regarding the sub-piston induction, a simpler alternative is to drill out the venturi to the next size. The whole point is to get extra air into the engine.

What if you do both-
Drill the venturi and saw the exaust?

DesignMan,
__________

I have done both, and the cylinder mod gives more power. Drilling out the venturi will add a bit of power ,too. But the cylinder mod wins on the power output . It really is not that hard to do, and is Almost the same work as the venturi drilling. One more item, if you drill the venturi too large it can cause flooding and needle set problems.

Tim Wiltse-RCU
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The way you mention geting induction is a way to go, I just don't have much work using the machine tooling stuff. The method I gave is just for those like me with little shop equiptment., and have limited options...

Remby