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- From: earl@trsvax.tandy.com
- Newsgroups: rec.models.rc
- Subject: Webra t4-80 solutions
- Message-ID: <1195667332@trsvax>
- Date: 15 Dec 92 19:44:00 GMT
- Lines: 75
- Nf-ID: #N:trsvax:1195667332:000:4007
- Nf-From: trsvax.tandy.com!earl Dec 15 13:44:00 1992
-
-
-
- Webra T4-80 notes...
-
- Well...after perservering, I discovered that the little 3/8" long piece
- of silicone tubing on the main needle valve was loose and allowed the engine
- to leak air and fuel out of this area. I took a 1/2" long piece of standard
- Bru-Line blue tubing and replaced the offending item. The engine then had
- a much better ability to run right, and I could adjust idle mixture to a more
- suitable setting.
- It still needs 15% nitro in the fuel due to it's lower compression ratio.
- I am still waiting for a couple of "hot" heat range plugs to come in, as I had
- to special order them, as none of the hobby shops stock them.
- It still won't idle below 3,000 to 3,200 RPM. With 3,300 to 3,500 being
- quite reliable. MAybe after a few gallons of fuel it will idle better.
-
- Unofficial prop speed timings....
- Master Airscrew 12-8" prop 10,200 RPM
- Master Airscrew 13-6" prop 9,500 RPM
- APC 11-8" prop 11,500 RPM
- APC 12-8" prop 10,500 RPM
-
- The 13-6 will have to do as with the higher idle speed, I'll need a lower
- pitch prop to help keep the air speed down on landings.
-
- Webra didn't make it easy to set up their engine. I had to special order
- this engine, as none of the hobby shops have any demand for stocking them
- in the first place. According to the instructions that came with the
- engine...they said to leave the needle valves alone as they had preset
- them at the factory. Well after unpacking a obviously factory packed engine
- box, and bench mounting the engine, I discovered that the both needles were
- screwed in all the way, plus the idle stop was screwed in too far, and the
- barrel stop screw was screwed in far enough to tighten up and jam the
- throttle barrel. Anyway it took quite a while to get it running well enough
- to start figuring out what all the problems were. Then after getting side
- tracked, I discovered that the main needle was leaking air around a loose
- fitting piece of silicon tubing. After correcting that problem the engine
- now runs pretty good. Now I can wait for the weather out here to improve
- so I can go fly the plane it is in. But if your a beginner to model engines
- I highly recommend that you go with a OS Surpass, Saito, or Enya 4 cycle
- engine before getting one of these Webra engines. As you'l have to
- tinker with it and use up a lot of fuel and patience to get it to work
- right. Once you do figure it all out, it does work pretty good though.
- Now it's time to find out how long it'll last before that overhead rotary
- valve or toothed belt drive wears out.
-
- I also tried out a new item a "one-way" valve on the muffler pressure tap.
- This worked quite well, but it' keeps the tank pressurized after you kill
- the engine. Thus you could easily flood out your engine if you aren't
- careful and pinch off the fuel inlet line to the carburator. On the Webra's
- 4 cycle muffler, you can build up several PSI in the tank which could be
- risky as the fuel tank bulges out a lot from the internal pressure and might
- split open in the future. With all that pressure in the tank, you could
- put the tank pretty much anyplace you want, it sort of acts like a
- replacement for a fuel pump. Since I didn't want to risk a split tank I
- opted to quit using the "one way" valve and go back to using standard
- medical hemostats when I fuel the model, on both the fuel inlet to the carb
- and on the muffler.
-
-
- ***********************************************************************
-
-
- <This information is provided by an individual and is not nor should be
- construed as being provided by Radio Shack or Tandy Corp. Radio
- Shack/Tandy Corp has no obligation to support the information provided
- in any way. >
-
- Earl W. Bollinger
- @ <earl@trsvax>
-
-
- "You were in the Clone Wars!", said Luke excitedly.
- "Yes", replied Obi Wan, "I was a DOS programmer. But that was before the dark
- times, before OS2."
-