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Cermark 3MM 50cc TOC Gas Engine Review

Join Dr. Dave as he burns some fuel, turns some props and makes some noise reviewing this extensive line-up of gas/oil two-stroke motors.

Splash

Introduction to Testing

I was fortunate to have access to four different engines all at the same time for testing and comparison. To say the least it was a task of some duration, but one that gave me special insight and understanding of not only gas engines but also propeller selection.

Method

My approach for all the engines was to first break them in using a 24:1 mix of gas and oil: rich with oil (Polaris Premium Synthetic Blend), but plenty of lubricant for the break-in. I ran 87 octane (blended with ethanol) as that is what is available in this area. Each engine had one gallon of fuel run through it with the designated break-in prop. For the first three quarters of the gallon the engines were run no more than 10 minutes and then allowed to fully cool. During each 10-minute cycle the throttle was manipulated to make sure a variable RPM was achieved. Cylinder head temps were taken with an infrared temp sensor during the runs to make sure nothing was overheating. All starts were by hand.

Towards the end of the each gallon I would advance the throttle from stop to stop periodically. With the exception of the SPE-43cc engine I never touched the needle valves, but it was just too rich in the 100 degree air and 60% humidity to run well so I leaned that engine back very slightly to improve the run. All the engines were run with a 6 volt NiMH battery with a capacity of 1200 or greater mAh: the 3mm 50cc TOC was run with a 4.8 volt battery.

My tank was about 18 ounces and three runs consumed the full tank for all the engines typically. The throttle was varied within each ten minute run multiple times. Starting was easy, and once I established a routine for choking, the process became very predictable. I found it necessary to choke all the engines before each start. I also found they started better if I cracked open the throttle just a bit to allow some air. After starting, I moved immediately to idle to allow for warm up.

I set the props to load compression at about 12:00 and to break-over at about 10:00 to 11:00. It is easier and safer if your flip is away from the engine and down. Periodically I would re-torque the prop to the hub. Early runs typically were full of vibration that settled out after a gallon or so and after I backed off the oil and adjusted the carburetor.

Master Airscrew Propellers

All the props for this project were provided by Master Airscrew . Started in 1977 by Fred Jamieson, the Master Airscrew brand is well known among flyers worldwide. The fine people from Master Airscrew provided me some information I want to share with you regarding their line of propellers.

In their shop they produce all their injection molded props starting first from CAD designs. Props between 6" and 20" are produced and then tested for strength continuously throughout the production process and checked for balance, warping and appearance. The nine professionals working at Master Airscrew ensure, through their combined total of almost 100 years of service, that each and every prop leaving the shop is perfect, and I can confirm that claim. Their wooden props are imported from Italy.

Over the last thirty years they have been innovators by paying close attention to the needs of modelers. They offer a high quality prop at a good price and great customer service. Be on the lookout for their new line of Formula One Series propellers: they are sure to be a wonderful addition to an already excellent lineup.

About the Props

All props required their center hole to be drilled out and at least two smaller prop bolts to be drilled. I used a drill press and set up a jig so I could make sure I centered the hub bolt. The prop washer helped me align the two secondary bolts. The props were then checked for balance.

Balancing of the composite props typically was not a problem; My method was to sand off or scrape off the heavier end until I felt comfortable that no more should be removed. If needed, I sprayed clear acrylic paint to the light tip in layers to add weight. The Master Airscrew line of props was exceptional throughout the testing process.

All props bolts had torque applied using PB Swissís torque drivers, ensuring uniform compression of the prop hub. Wooden props require re-tightening after each run until the prop settles into the hub. Torque settings were approximately 3.0 ft lbs / 36 in lbs.

Test stand

I constructed a test stand using lite-ply and fiber-glassed the front, sides and all corners. This is important to make sure the stand does not rattle, vibrate or come apart. The fiberglass also keeps the fuel from softening the lite-ply. Surprisingly, you get very little fuel on the firewall with gassers. I mounted the stand to a large picnic table so that there was no chance of any movement.

Thrust

The test stand was hinged so it could tilt forward. The stand was tall so a cable was connected to the stand and the picnic table with a fish scale in the middle. A second cable was attached to the stand to make sure nothing could move forward beyond the movement of the scale which proved very effective.

Comparing Engines During Break-in

I want to be clear that I am not making any comparisons of the engines through their break-in. The rich mixture and higher oil content just do not make the comparisons worth much. The break-in process is a necessity though.

I began the break-in of the four engines with the SPE-26 and followed with the MLD-28. Both engines share the same firewall bolt pattern and the SPE 26, SPE 43 and MLD-28 share the same three-bolt prop hub pattern.

Spark Plugs

I used the original equipment and then replaced it when the prop testing was done. I found no problems with any of the plugs.

Engine Prototypes

The MLD-28 and SPE-43 engines were early prototypes. At press time the MLD-28 is being sold with a different CDI ignition and velocity stack as the MLD-28S. The SPE-46 was upgraded from the SPE-40. The SPE-43 is being shipped with a different timing setup and some slight internal modifications from the engine I tested.

3mm 50cc TOC


Displacement:3.24ci / 53cc
Bore:1.732 in. / 44mm
Stroke:1.377 in. / 35mm
Horsepower:5.5 @ 8000 rpm
Operational Range:1200 to 8000 rpm
Props:22 x 8, 22 x 10 and 23 x 8 for two-bladed and 20 x 8, 20 x 10 and 22 x 8 for three-bladed
Configuration:Single Cylinder Head Cooled
Carburetor:Walbro Pump
Number of Bearings:
Ignition:CDI Electronic Ignition with Auto Timing Advance
Spark Plug:NGK CM-6
Power Supply:4.8v - 6.0 volt
Weight with Muffler:3.6 lbs / 1880g
Muffler Type and Weight:Polished Single Exhaust 5.6oz
Oil:2-Cycle High Performance Synthetic
Break-in Mix:24-30:1
Normal Mix:45-50:1
Manufacturer:3mm Engines
SPE 26 Engine Cermark Link:Cermark SPE 26
Cermark Homepage:Cermark Homepage
Email Cermark:sales@cermark.com
MSRP:$399.99

3MM TOC 53 includes:

  • Engine and polished muffler
  • Spark Plug
  • 6 prop hub bolts and lock washers
  • 2 muffler bolts and gasket
  • Spark plug wrench with Allen head handle
  • CDI Ignition
  • Plastic throttle arm
  • Wire protectors

The 3mm is a beast, let there be no doubt about that. It is a blend of rough edged power and polished beauty. From the minute you open the box you can see this big brute is all about hauling a plane around wherever it wants to go. I enjoyed this one as much as the MLD-28.

Downloads

At just over four pounds, the 3MM TOC 53cc engine produces 5.5 horsepower. It is capable of swinging up to 23 inch props and does so with a smooth 44mm stroke of the 53cc bore. Of the four engines this is the first to pull fuel up through the crankcase and into the cylinder. The hub mount is also significantly different with no center bolt and six propeller bolts. The center of the prop shaft is drilled and tapped for a spinner.

Startup and Break-in

The mounting of the 3MM was completely different from that of the previous three engines. It required moving the throttle linkage, and there are no standoffs provided with this engine.

Be sure you mount to a flat firewall that is glued and, if possible, fiber glassed. You will need to provide either an engine box or standoffs to allow for air circulation. When I did the bench tests I did not stand off the engine but never got over 170 degrees of head temp with crankcase temperatures right at 100 degrees. The smaller NGK CM-6 spark plug is very different from the Champion plugs. Unlike the others, this engines runs on a 4.8 battery pack (the voltage range is 4.8 volts to 6 volts). It may be possible to use a 6 volt battery, but I did not.

The voice of the 3MM is beautiful. It is a thumper with a nice low idle exhaust note that transitions to a smooth powerful purr. Starting was easy even on the first start of the day. I flipped it though a few times with the choke and then removed the choke and turned on the ignition, and it would start the first flip.

I also want to be sure to note the third bearing on the crankshaft: It is absolutely noticeable, and the smoothness is a big positive!

For some reason the mounts on the 3MMís CDI broke. I had insulated the module from vibration, but the case is plastic. One might err on the side of caution and use zip-ties to secure the module.

Prop Torque

Wooden props require you to re-torque them after every few runs. You can haphazardly do this by feel, but the correct method is to use a torque gauge. I used PB Swissís Torque handle to make sure I got the exact torque on all six bolts. This is especially important since there is no center 10mm bolt to tighten. I applied torque to each bolt in a sequence to 3.02 ft lbs/36.29 in lbs. I tightened the bolts in sequence because head bolts on motors have tightening patterns to spread the load across the head.

Downloads

Hub Torque Video  11.45 MB

3mm 50cc TOC Prop Tests

This engine was a joy to run. It was easy to start and required no carburetor adjustments for most of the break-in and through the prop testing. It is powerful, and I cannot wait to get it into a plane.




PropLow RPM High RPM
22 x 8 1770 6000 16lbs
22 x 10 18005610 14lb 9oz

Test Summary

I highly recommend the 3MM TOC 53 engine to any serious flyer. It is well built and engineered, and with a third bearing, it is smooth at all RPMs. I found no problems that would keep me from using this engine. I wish they included the standoffs; that would provide some consistency.

Conclusion

Properly treated, these Cermark engines are well worth the money and will last a very long time. Product support from Cermark for my testing has been excellent; whatever I needed I was provided and they responded quickly to my needs with a phone call.

Last edited by Angela H; Nov 17, 2008 at 06:55 PM..

Discussion

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Old Nov 18, 2008, 10:54 AM
In NY's beautifull hills
staggerwing's Avatar
Binghamton Broome Cty, New York, United States
Joined Jun 2004
1,126 Posts
Nice to see reviews on these new gassers--I've sure been curious.
By "a third bearing" I assume your adding it on the PTO end.
Although having CDI & a tad lighter, & maybe more compact, pricewise for me I might choose the bullet proof G62---it keeps on tickin--forever.
I tried to get dimensions from a couple of these new on the market gasser sellers (I think the SPE) but never got a reply--forgot the distributor here in RCG.
That made up my mind on a purchase.
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Last edited by staggerwing; Nov 18, 2008 at 01:58 PM.
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Old Nov 18, 2008, 12:00 PM
www.ReaperBrushless.com
The Reaper's Avatar
Joined Jul 2007
1,868 Posts
little under powered

hey guys

i think its under powered with the average 50cc plane weighing in at 16 lbs and the motor only puts out 16lbs of thrust it would be good for sport flying but wouldnt be enough thrust for a 3d plane requiring 1.5 to 1 or 2 to 1 thrust ratios if said plane weighed 16 lbs.

scott
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Old Nov 18, 2008, 12:20 PM
Dr. Dave
USA
Joined Nov 2005
1,316 Posts
Scott, that's static thrust. Plenty of 3D birds flying the 3mm
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Old Nov 18, 2008, 12:26 PM
Grumpa Tom
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United States, CA, Los Angeles
Joined Sep 2003
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Quote:
Originally Posted by staggerwing
Nice to see reviews on these new gassers--I've sure been curious.
What he said!
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Old Nov 18, 2008, 10:01 PM View Post
daddysard
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Old Nov 20, 2008, 04:32 AM
Team 3DHS
BoneDoc's Avatar
San Antonio, TX
Joined Sep 2004
15,632 Posts
6000 rpm on a 50cc and 22x8. Is that number a bit low?

Great review BTW. You've got a neat setup.
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Old Nov 20, 2008, 05:26 AM
Dr. Dave
USA
Joined Nov 2005
1,316 Posts
BoneDoc, not sure if 6000 is low or not. I did struggle with the tach as I was getting reflections outdoors off the props. I retook readings often, but finally settled here. The RPM range is to 7800.
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Old Nov 21, 2008, 02:26 AM
Kenny- Really!
exciter900rr's Avatar
USA, CA, Cathedral City
Joined Jul 2007
809 Posts
Quote:
Originally Posted by The Reaper
hey guys

i think its under powered with the average 50cc plane weighing in at 16 lbs and the motor only puts out 16lbs of thrust it would be good for sport flying but wouldnt be enough thrust for a 3d plane requiring 1.5 to 1 or 2 to 1 thrust ratios if said plane weighed 16 lbs.

scott
I'm sorry.... What prop are you running with the 3mm toc 53?
a 11/6 zinger? your 16 pounds of thrust is ridiculous!

I have close to 27 pounds of thrust with a 22/8.

BTW, my WH extra weighs 18+ pounds due to a few fixes and mods over the past year, and hovers at just over half throttle- Where did you get those numbers?
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Old Nov 22, 2008, 07:30 PM
Scott Stoops
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United States, CO, Longmont
Joined Mar 2002
8,411 Posts
Quote:
Originally Posted by 78dave
BoneDoc, not sure if 6000 is low or not. I did struggle with the tach as I was getting reflections outdoors off the props. I retook readings often, but finally settled here. The RPM range is to 7800.
6000 RPM is exceptionally low for a 50cc engine on a 22x8 prop. 6700-7000 would be more in line for most 50's on a muffler. FWIW.

Scott
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Old Nov 22, 2008, 08:12 PM
blucor basher's Avatar
United States, PA, Lancaster
Joined Jun 2003
24,141 Posts
From the Cermark 50CC Yak review by SteveH, using the same engine:

I noticed the power was lacking in any kind of hovering or 3D so I landed to check out what could be the problem. I tached the 22x10 at 5800RPM on the ground, which is not enough RPMs to get the thrust the Yak needed, and from reading other posts on the Internet was lower than others with the same engine. I switched out the prop for a Vess 23A which is a good match to other 50cc class engines. I also removed the spinner. which yielded a increase to 6200 RPM, so I went for a few more flights. The Yak would now hover but not really pull out of one. I switched to a Vess 22A, and the 3MM turned it at 6800RPM which is closer to where it should be. I have also read that Wildhare sells a Hop Up kit for these engines that is supposed to increase RPMs by a couple hundred, but I have not tried one.
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Old Nov 23, 2008, 01:13 AM
Registered User
Zebulon, NC
Joined Aug 2000
5,086 Posts
It should be higher with the 22x8, more like 6800-7K. My Yak is a little over 18 pounds and its not enough power to pull out of a hover very well and thats with 6800 rpm on the 22A.

Your RPM on the 22x10 is close to what I got with that same prop as well though.
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Old Nov 23, 2008, 06:15 AM
Dr. Dave
USA
Joined Nov 2005
1,316 Posts
My numbers again were static and the mount was cantilevered over a hinge. So the numbers can not be absolute. It was my method and those numbers might differ. Not at all "ridiculous". Each and every method is going to differ.
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Old Nov 23, 2008, 09:51 AM
Registered User
Zebulon, NC
Joined Aug 2000
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Any idea why the RPM's are so low?
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Old Nov 23, 2008, 12:14 PM
Kenny- Really!
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USA, CA, Cathedral City
Joined Jul 2007
809 Posts
If you notice, The exhaust has the "small" down pipe. Apparently, there were two different ones shipped with the engines. this is part the culprit- you still should have over 6400 rpms give or take. I noticed the difference when I had a deadstick and pancaked the gear, and yeah.. also the muffler. Tom at Wild hare was temporarily out of the mufflers, so I got one from cermark. the muffler I finally received was MUCH larger than the stock one, and once on the engine, I knew I had the wrong one at first. The small muffler will choke up the engine a bit.

Sorry Dave for using the word "ridiculous", bit eleven pounds of thrust difference? It's like saying "I'm getting a peak Rpm of 9500 on my TT pro .40" Anyone who hears that would be curious "why".....
I dunno- I'm sure it has a lot to do with still being a fresh engine, and the way it was broken in/being broken in, but I'm sorry- I know I am not the only one with one of these engines that makes GREAT power, I just want to let others who might be reading this review know that for this engine, this is not typical output.....

If Ya'll want more power from that engine, give Tom (WH) a call and get the hop up kit- once you have it in your hands, it will become quite apparent why it makes more power.
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