Put on a show! Tapping an engine for smoke

Apr 17, 2013 7 Comments by

Rick Michelena shared a technique he recently used to add a smoke tap to a HobbyKing 52cc Turnigy engine. As he notes, why not try something new this weekend? This project can be accomplished by anyone with reasonable mechanical skills. I crawled into the shop today after receiving a new engine from UPS. Below is a picture of my Swordfish. I originally used an old Quadra 50CC engine that was lying in my shop. The last time I flew the Swordfish, I was not impressed with the engine’s performance. I was only able to achieve 6200rpm using a balanced Top Flite 20×10 Power-Point propeller. I believe the 30-year-old Quadra is a bit tired. Capture

Only certain engine configurations will fit this aircraft.

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I found this Turnigy 52 CC electronic ignition engine on-line, and I purchased it from Hobby King. It was so inexpensive that I decided to gamble on it. However, since my old Quadra was tapped for SMOKE, I needed to install a SMOKE tap on this new engine. The following photos and instructions should give confidence to anyone who desires to tap any RC gas engine for SMOKE.

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First, the engine must be disassembled as seen above. The reason for this will be clear in the following photos.

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I have chosen to tap the engine in this location, but any location is fine. I used a drill press to bore a hole for thread tapping.

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Once the hole was drilled, I used a 1/4-28 tap for my SMOKE fitting. These fittings come with the B&B Specialties SMOKE System.

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Notice that the SMOKE tap treads extend into the crank journal. This is not desirable. Therefore, a Dremel tool will make short work of the problem.

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With the threads ground flush, it was time to blow out all the metal filings and re-assemble the engine.

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I used Loctite 515 flange sealer on all engine mating surfaces.

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With the case together, I seated the head to the crankcase. I was surprised to see two piston rings on this engine’s piston. To re-assemble, always look for the piston ring pin locators and squeeze the piston rings together at those points. I fully lubricated the cylinder walls and the piston rings with 3-1 oil to make assembly easier.

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I also removed the factory prop bolt and re-tapped the propeller hub using a “Heli-Coil” for thread size 5/16-24. This happens to be the standard Quadra propeller bolt size for the 35-52CC engine series. Capture

This photo shows the standard Q-52 bolt that is already tapped for a spinner. I used the Q-52 drive washer as well. This way, I did not have to drill special propellers for this particular engine. The engine is now assembled with the SMOKE tap clearly visible on the left. I discovered that a G-62 muffler will fit this engine perfectly. I will now order a SMOKE muffler from B&B Specialties.

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I built this test stand and will secure it to one of the starting tables at our club field. The SMOKE system is from B&B Specialties. I have used these very reliable systems without fail for the past 24 years.

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Since I do not have a SMOKE muffler at this time, I will test the SMOKE system by manually pulling the SMOKE valve open about 1/2 inch. If all goes well, smoke fluid should begin to collect in the small jar positioned between the tank and firewall.

TEST RESULTS: I mounted the engine to one of our starter tables, filled the tanks with gas, and turned the ignition on. The engine came alive within a second of using a Sullivan Megatron starter. The engine ran perfectly throughout the entire range. I only made a small carburetor adjustment at the end of the day in order to “tweak” the high side. When testing the SMOKE system, my collection bottle quickly filled with SMOKE oil. Therefore, both the engine and SMOKE system functioned flawlessly. I settled for 7000 rpm on a 20×10 propeller. I will expect even more as the propeller unloads in the air. This should give me the performance I am seeking for my Swordfish. This hobby is always about trying something new. Do not be afraid to attempt this process. I still remember when I completed my first engine tapping very successfully. Remember to take your time and not leave any metal particles in your engine. You will see that your engine will run great, and you will now join that group of modelers who have taken up “SMOKING” on the weekends!

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7 Responses to “Put on a show! Tapping an engine for smoke”

  1. Eddie says:

    Rick nice job! did yo get a chance to record a video wile testing the engine? Would love to hear it.

    • Rick Michelena says:

      Eddie, I did not record any video. There were about 10 modelers around who witnessed the performance. The engine required no carb adjustment to run. I did a couple of tanks at different RPM levels. I then tweaked the high end and got 7,000 RPM on a 20 X 10..that’s about right for 50CCs.

  2. Martin says:

    How to connect the oil pump to mufler?, interesting smoking system, in another engines from hk, have a fiting to carburator pump, i’ll like use this with an t connector, do you think is ok?

    • Rick Michelena says:

      Martin, I noticed that this engine does use crankcase pressure for the carb. However, I do not know if that small tap can provide the volume of air needed to run the carb and smoke pump. My method works. The lines to the smoke are large. You will need to make a reducer. As far as hooking the muffler up, B&B has instructions that are simple: a line comes off the smoke valve and “t’s” off with equal lenght lines to the muffler smoke taps. Give it a shot and see how it works.

  3. John Elkin says:

    Hi Rick,
    What material is used on the prop driver [photo 10] as a friction disk?.
    Great job on the article, clear and concise.
    /

    • Rick Michelena says:

      Dear John,

      Believe it or not, there is no material on the prop hub. What you see is deep grooved, machined aluminium. Thanks for the comment.

  4. Robert Cramer says:

    I enjoyed the article on tapping an engine for smoke. I am new to the flying hobby after a 30 year hiatus and I am catching-up quickly by reading your publication. I would personally like to see some articles on the motor spec’s and what they mean for the motors that run the fans on the new-to-me electric planes. I have not flown a plane since the early 1980′s and boy have a lot of things changed in the last 30 years. Bob C.

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