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 both propeller selection.
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.
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.
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 Swiss’s 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.
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.
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.
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.
I used the original equipment and then replaced it when the prop testing was done. I found no problems with any of the plugs.
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.
|Configuration:||2C single Cylinder Head Cooled|
|Number of Bearings:||2|
|Ignition:||CDI Electronic Ignition with Auto Timing Advance|
|Spark Plug:||Champion RDJ7Y|
|Power Supply:||4.8v - 18.0 volt|
|Weight with Muffler:||2.3 lbs|
|Muffler Type and Weight:||Single Exhaust|
|Maximum Output:||2.3 BHP|
|RPM Range:||1,500 - 9,000|
|Oil:||2-Cycle High Performance Polaris Synthetic|
|Prop Selection:||16 x 8 to 18 x 10|
|SPE 26 Engine Cermark Link:||Cermark SPE 26|
|Cermark Homepage:||Cermark Homepage|
The SPE-26 engine is 1.6 cubic inch 2.3 brake horsepower engine with two ball bearings supporting the crankshaft. A side mount muffler is included, but a Pitts style is available. The ignition module is waterproof and vibration proof. The voltage required for running the SPE-26 is any 6 volt to 7.4 volt of at least 700 mAh. The spark plug is a Champion RDJ8J. The cylinder head features a curved head and an angled spark plug. Using 30mm standoffs the engine mounts to the firewall along the crankcase.
Based on manufacturer recommendations I used a 16 x 8 Master Airscrew prop for the break-in. I applied the choke and turned over the engine several times to draw fuel into the carburetor. I then switched on the ignition, and after about 15 -20 flips, the engine came to life. I allowed the engine to run at idle for several minutes to warm up the crankcase and cylinder head. Crankcase temps were about 110 degrees, and the cylinder heads rose to 140 degrees with peaks at 150 degrees on advanced throttle settings. RPMs were between 3,000 and 7,000, but typically through the first three-quarters of the gallon I kept them below 4,500 RPM.
The SPE 26cc was not too loud, and it really acted like it was ready to go within the first few tanks. As the gallon was consumed I tested the throttle response, and there was never any hesitation.
Before I began the prop test I mixed new fuel at 40:1 and I replaced the spark plugs. For the SPE – 26 the first gallon did not show any signs for concern on the spark plug. I also installed a velocity stack onto the carburetor.
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 Swiss’s 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.
|Prop||Low RPM||High RPM||Thrust|
|16 x 8||1890||5lb 2oz|
|16 x 10||1800||7830||5lb 1oz|
|18 x 6||1710||7350||6lb 15oz|
|18 x 10||1680||6720||6lb 8oz|
The SPE – 26 ran great from the beginning of the test to the end. I did notice after the break-in and then after the prop tests that the front bearing on the crankshaft had some play. Throughout the runs I measured head temps in the mid 100s and crankcase temps near 100. The engine was easy to start and required very little in the way of carburetor adjustment. I recommend a velocity stack for the SPE – 26. Without the stack you will lose fuel from the carburetor because the prop forces air over the carburetor and creates a negative pressure just outside the throttle body.
With the exception of the bearing looseness, I would recommend the SPE-26 as an easy to start, easy on fuel, smooth running and excellent acceleration engine.
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 06:53 PM..
|Dec 19, 2008, 04:54 PM|
Wow, just 6lbs thrust from a 26cc engine that weighs 2.3lbs. It looks as if glow-engines will rule the roost for 3D flying for the foreseeable future with that kind of performance.
But for warbirds and sport-models where the extra weight may come in handy, these engines produce nearly as much thrust as a .90-sized 4-stroke glow engine.
|Feb 26, 2009, 07:42 PM|
SUPER Thanks for the reveiw, on the gasser, the problem I see is the mounts are weak, and they crack real easy.????????????????????????????????????????????? ???????????????
|Feb 27, 2009, 08:43 PM|
We have not had any SPE-26 nor MLD-28 that had crack in the mounts. They are plenty strong.
There had been cases on the SPE-40. However, we have since resolved those issue with new internal parts. We have since moved to North American SPE-43. We have not had any crack on the 40+ sizes except one. The customer claimed that he did not crash, but our service dept found dirt in both the muffler and carb. Hmmmm...
|Feb 28, 2009, 09:07 AM|
moreno valley california
Joined Jun 2008
glow does pretty much rules the roost if the user is looking for maximum (ie 3D or IMAC performance) in the 20cc or so size. otherwise, these engines present a good alternative for warbirds or other scale jobs. i would like to comment that in terms of performance, MA props are pretty much at the bottom, along with Zinger. APC or the better wood props, such as NX or Menz will get significantly better numbers on the ground, and more bite in the air. Also, it takes about 3 to 4 gallons to completely break in a gas engine, and during that time the engine will continue to get stronger. So it's tough to base a conclusion on preliminary numbers. last rpm numbers can be deceptive with cheap props because the blade distort at full throttle allowing higher rpm with no performance gaini. so i would look at the numbers as minimums.....and with a better prop and more time things will only get better!
|Mar 02, 2009, 01:56 PM|
Agree KoppterX, but we still can't afford too many Menz even at a discount from our bud Dave, of DA. Besides, it can definitely skew the data!!!!! Imagine us listing rpm as 9,000+.
|Mar 14, 2009, 03:54 AM|
Joined Jan 2009
Thanks for the revew of the spe26.
I'm curious to know if you can post what props were used to gain your results. I'm currently running a spe26 and cannot get any good results out of a 18 prop. 17 and 16 seem to be the best diameter. So far a 17 x 6 or 17 x 8 work well as well as a 17 x 10N. These were all APC props. I would have to agree that this engine is not a power house in my 11.5lbs Edge. I may have to put it in my Monocoupe for scale flight. I would like to see tests on the MLD 28 !
|Mar 25, 2009, 11:51 PM|
Flyer888, here is a review that Dave did on MLD-28S. You can also email/pm Dave directly, because he has a ton of projects going on at the same time.
|Jun 12, 2009, 07:59 PM|
Press Release: MLD & SPE Engines - June 12, 2009
Currently all 3 gas engines, SPE-26 (v-4), SPE-43 (v-4) and MLD-28 (v-5) are completing their updates and modifications. The process has taken much more time than we have anticipated. The final round of testing and approvals should finish after the week of July 4th, 2009. Because of required quality assurance process, we can only ship out the back-ordered engines after all inspections and tests are done. The corresponding manuals will become available after July 17th.
The areas of improvements are the electronic ignition systems (CDI), the vibration, the low-to-mid range throttle response curve, the carburetor, and other non-disclosed areas. As result of the updates and upgrades, you will have a better SPE or MLD North American engine. For those of you who may be concern with the North American SPE and MLD engines that you already own. Please do not be alarmed. The engines simply undergo improvements. We have simply executed the update process poorly, hence the gap in their availabilities.
Please contact us, if you have any question.
|Jul 28, 2009, 06:19 PM|
SPE-43 Engines update - July 28, 2009
North American SPE-43 are being shipped to dealers and customers as we speak. They have gone through all of the required quality assurance process. The areas of improvements are the electronic ignition systems (CDI), the vibration, the low-to-mid range throttle response curve, and other non-disclosed areas. Please contact us, if you have any question.
|Aug 01, 2009, 04:26 PM|
For those of us with the SPE-40 v1 and v2 are there recommendations as to how to best handle the engines. I.E. without the updates of the newer engines what can I do to protect my investment in these engines?
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