3MM TOC-53 Gas Engine

REVIEW

Specifications:

Bore/Stroke:
Displacement
Weight (bare engine):
Props:
RPM baseline:
Bearings:

44mm/35mm
53cc
58 oz
22x8-24x8
22x8 @ 6700-6800
3 ball & 2 needle

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         In my quest to find a suitable engine for my newly purchased 27.5% CRISTEN EAGLE II, I looked at a lot of engines. I settled on a 3MM TOC-53 gasser. Having never owned one, I thought this would be a great opportunity to review this engine. 

        The package includes the basic engine, a highly polished muffler, and RCEXL type Ignition. It also has a sparkplug wrench and an assortment of gaskets.The engine ready to fly weighs a little over 3.5 pounds. That's not too bad considering the weight of other engines of similar size. I generally do a visual inspection of my engines first, to determine the fit & finish of the castings. This is a very nicely fitted engine having good quality castings and machining.

         I mounted the 53 in a typical inverted position on my test stand.  The engine was a little difficult to start the first time taking about 30 flips to get it wet enough to run. Once it fired up, I let it run for about 10 to 15 minutes before putting it through its paces. My first prop was a 22x8 Chip Hyde Brazilian wood prop. The 53 performed well having an idle of 1700 RPM and a top RPM of 7160. Throttle transition was excellent.   Next, I switched to a Menz Ultra 20x12 Three Blade prop. This prop was a little tougher to handle. It idled at 1490 RPM and peaked out at a solid 6300 RPM. I cut off the engine and let it cool completely down so I could try a cold start. It took about 7 flips with choke, then 5 flips to start. That's pretty good for a brand new engine only having about 25 minutes run-time. I then switched to a Zinger 22x8 prop and tried it from a cold start as well. This time, it took only 5 flips with choke and 5 flips to fire up. The Zinger idled at 1690 and peaked at 6920 RPM. That's a little better than the advertised ratings.

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           The 3MM TOC-53 is a very clean engine. It does take a lot of run-time to break it in, since it has a two-ring piston. The prop hub bolt pattern is 3W and DA-100 pattern. 6-bolt prop mounting is totally un-necessary but at least the shaft is drilled and tapped so you can mount a spinner.

           Basically, this engine is a semi-clone of the 3W-50 with the exception of carb location and bore diameter. I really like the side-mounted carb but I wished it had V-reeds instead of twin flat reed valves. The engine would have made a lot more topend power. I also like the fact that it has 3 ballbearings supporting the crankshaft. This prevents un-due stress on the crankshaft especially if you happen to have an un-balanced prop. The engine does have more vibration as compared to a DA-50, but its not by any means the worst I've seen. From a performance perspective, the 3MM is equal to a DA-50, BME 50 and greatly superior over 3W-50 and Fuji 50.

          You get a lot of bang for the buck with the 3MM engine, and I'm looking forward to flying my Cristen Eagle with it. However, if I were to make any changes in this engine, I would make the prop hub a single bolt with the option to use 6-bolt, and I would use a V-reed intake similar to the DA-50 setup. Lastly, I'd look into getting a better internal balance out of it.

          The 3MM TOC-53 is a worthy investment. You will find that it's compact in size and will virtually fit into any aircraft you desire. The power is excellent and it's capable of spinning large 3D props. I would highly recommend that you stay with 32:1 petrolium based lubricant for at least the first 5 gallons to insure complete break-in.

This engine is available from:.Wild Hare RC  and BCMA Engines  

Here is a side by side photo of the 3W vs. 3MM

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           As you can see there's a striking similarity between these two engines, with the major difference being the carb location and the backplate. Another major difference that's not obvious is, the 3W uses a Walbro HDA carb whereas the 3MM uses a Walbro WT carb. The HDA is a much bigger carb. .

This review will continue as soon as my Eagle is ready to fly...

          The 3MM was installed in a 27.5% Christen Eagle II, and weighed in at 16.0 pounds Ready To Fly. The aircraft accomodated the engine perfectly. My prop selection was a CHP 22x8 and it flew the Eagle with extreme authority. I did have to be careful on the throttle during take-off as the Eagle was eager to left-hook from all the torque. The 53 was reliable, easy starting, and a real power house for this 16 pound bird. It would hover at about 1/3 throttle and pull-out at 1/2 throttle.

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         I'm sure there's a better prop for this engine/aircraft combo but I used what I had available and it did spin up to a solid 7100 RPM. The engine ran perfectly every flight and never needed fine-tuning. I was a little concerned about the engine getting hot in the cowling but it never did. The factory muffler works very well but it is a little on the loud side. I like the 3MM TOC-53 engine.    

 

Copyright 2007 M. B. Fuess