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.020" TEE-DEE Port Specs and durations

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.020" TEE-DEE Port Specs and durations

Old 08-29-2006, 07:45 PM
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D Bronk
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Default .020" TEE-DEE Port Specs and durations

I need to know them .Can you, tell me what they are please.
Old 09-01-2006, 07:12 PM
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Default RE: .020" TEE-DEE Port Specs and durations

SKALLIWAG of Select Hobbies, is Sending me a TEE DEE 0.020 to measure up. I`ll post the Specs. for those that are intrested ..Since this topic is on my mind, I`m wondering if any of the other members,have checked in to this topic ,with any of their other Cox, or, Norvel engines.It would be intresting to see what the real differances between ,Say,a KillerBee, BabeBee, BlackWidow, etc..A type of, Data Base to refer too with hard facts.[sm=49_49.gif].Or, am I the only Guy, intrested in this kind of thing ?.[sm=50_50.gif]..Dave
Old 09-01-2006, 07:36 PM
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Default RE: .020" TEE-DEE Port Specs and durations

I think this is a really interesting subject, Dave. Although I have a green thumb when it comes to getting engines to run, I know next to nothing about their internal workings. I used to read all of Clarence Lee's reviews in RCM and one of the first things he seemed to check was the timing. It seems that this data really tells the true story about a given engine, more so than the metalurgy, ie., ABC, ringed, etc. But, like I said, I don't know much about engine design.
Old 09-01-2006, 08:07 PM
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Default RE: .020" TEE-DEE Port Specs and durations

Maybe, we need, a bit of a "How To",In regards to this type of thing.Like, how to determine, what your engine has, in regards to timing..Interperting, what to do with the info,in regards to, changing things, from its stock form ,is another story.But!!! Once a person Knows, how to find out what his/her engine has,for timing to start with ,a person can easily copy another Succesfully modified engine,without quessing.Does that make sense?Example: I`ve modified my engine,and I list what my New Specs are .You`ve got a stock engine ,and would like it to run ,similarily to mine..You take my modified specs,and now replicate them on your engine..You` should end up with an engine, that will run similarily to mine.The Best thing is,You don`t have to go through, all the, Hit and Misses ,that I`ve had to go through.You can go directly to the end result.

..I`m not trying to come across, as, a Know it All..But ,I do have a pretty good Grasp on the subject,and am always trying to learn more..Maybe we can take a few GREEN thumbs, and make them in to Surgical fingers(porting)..[sm=tongue_smile.gif] ..LOL
Old 09-01-2006, 09:07 PM
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Default RE: .020" TEE-DEE Port Specs and durations


Dave, with engines this small, it is really hard to come up with accurate timing numbers. Having an engine sent to you to check for yourself is the best thing that could have happened. I could try to check the same engine and come up with figures that are contrary to what you get. The factory has the advantage of having dozens of blanks that they can port in different ways to see which one has the best running traits. Once they get a runner, they don't need to know what the timing numbers are, just dimensions of where the cuts are done. I think the important thing here is to use the TD as a bench mark. As accurate as Cox was, I'll bet TD .020 performance figures are all over the place.
Old 09-01-2006, 09:11 PM
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Default RE: .020" TEE-DEE Port Specs and durations

Taking a Dremel to a Cox cylinder, for example, is also a lot more accessible than milling and lathe work is to the average r/c flyer. So, it's something most pepole would be able to experiment with.

Now, is there somewhere to find published general rules about timing that apply to the typical 2-stroke glow engine? Such as: easy to start, sport engines have intake port timing in a range of X to X; High performance, screaming engines are usually somewhere between Y and Y. And, what is actually happening? What does changing the opening degree do? What does changing the closing degree do? Which is more important, opening or closing timing? And so on.

In many ways my old spark ignition engines are more simple. You just advance the point in the cycle at which the spark plug sparks with a little lever on the front of the engine.
Old 09-01-2006, 10:01 PM
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Default RE: .020" TEE-DEE Port Specs and durations

HI CP.. You know, Your Right about things changing, as the production is run.1`st cylinder of the run can be finished with Such and such dimensions ,100`th cylinder,coming off the same machine ,2 hours later, can be different measurements just from ,the Tools wearing as the day goes on .They always have tolerances +,or- ,so many thousandths of an inch, lots of variables come in to play..It happens to all the Manufactures of large(GM), or small engines (Cox).. Some of the CNC Machines, have programs, that adjust for tool wear.But You can have a cutting tool, that`s harder, or softer, than the Standard ,that the program was set up for,and have, actual different wear rates.So that`s not a perfect world either. I would find it, kind of intresting ,to see what kind of differences, could be found, on the same model type engine.(5-6 of the same thing) Just to see, what their tolerences are, from 1, to the next.

RainD ,I don`t know of such a Chart,or Rule of Thumb,but, if Someone does ,I would like to see it..There very well could be though.That, changing the point timing Thing,has worked for a long time.There was those Real Old cars where you pulled the lever on the steering column,Farm tractors the same thing.Sort of worked like a throttle ..
Old 09-01-2006, 10:26 PM
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Default RE: .020" TEE-DEE Port Specs and durations

In a way, the same rules apply to hopping up a 4 stroke. Lengthen the time the valves stay open and you will hurt low rpm torque but increase low load rpm potential. Before any timing work can be done, you have to have the most friction free specimen to start with. When you flip the prop, the prop should bounce back and forth wildly between flips and the piston / liner seal should stay pumped for a long time when you slowly force the piston to TDC. Starting any engine work before you have a qualified specimen is a waste of time. I have never done any meaningful timing work on anything under a SuperTigre .15. Forget about using a dremel freehand on a .049 liner, that would be like doing brain surgery with a chainsaw, about the only place where a dremel and fine tooth carbide cutter could be used is on the closing side of the intake window [of the crankshaft]. Cuts in the liner ports should be done with jewelers' files if you don't have a mill with the proper holding fixtures. I always wanted to know how much trial and error it took COX to develope the TD, and how many parts went into the trash after attempts to modify. This is where the hobbyist is at a huge disadvantage. The areas where the hobbyist can out do the mass producer is with friction proofing and with decreasing reciprocating mass.
Old 09-01-2006, 10:30 PM
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Default RE: .020" TEE-DEE Port Specs and durations

CP, I know you must know what the ballpark ranges are for easy starting vs high performance. I imagine most production engines seek a compromise bewteen the two extremes, though leaning more towards friendliness. But is it possible to take a docile Cox cylinder and bump up the performance with a Dremel?
Old 09-01-2006, 10:53 PM
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Default RE: .020" TEE-DEE Port Specs and durations

RD, I suppose you could use a KillerBee liner as a guide and try to copy it..
Old 09-01-2006, 10:54 PM
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Default RE: .020" TEE-DEE Port Specs and durations

CP. the Fora was very impressive in the prop Bouncing department.I wouldn`t attempt useing a Carbide on these little Cylinders though .I have, a Daimond point set for that.Much easier to free hand with them, they don`t bounce like a Carbide might.The cutting edge ,is a full 360 degrees..I bought a set of 30 pieces ,for under 10 dollars.It`s a great investment, for the Dremmel tool.You can ,Cut Everything+Anything, with these little Buggers.
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