It seems as though there's a lot of competition in the gas engine market these days, and there are a few names that everyone is familiar with. Some of the big ones are DA, DLE, and 3W - just to name a few. There's more to the gas engine game than just them! Over the past decade, several smaller companies have sprung up - some have stayed, and some have gone away. But, just because these smaller companies may not be as well known, doesn't mean they don't have good products at good prices!
RCGF, a Chinese manufacturer of gasoline engines, designs and manufactures engines specifically for 'the RC aircraft market. They have a line of gas engines as small as 10cc, all the way up to 120cc! With twin cylinder engines ranging from 21cc to 120cc, they're bound to have an engine to fill your need.
In this review, we'll be taking a look at the RCGF 21cc twin cylinder engine - let's get the box on the table and see what's inside!
Engine Type: 2 Stroke Gasoline Engine Cylinder Displacement: 21cc (1.28 ci) Weight with Ignition and Mufflers: 2.02 lbs (920g) Weight w/o Ignition and Mufflers: 1.54 lbs (700g) Bore x Stroke: 27.6mm x 17mm (1.08 in x .67 in) Carburetor: Walbro-type designed by RCGF
The RCGF 21cc twin cylinder gas engine arrived in the company's signature blue box, packed in dense foam. A sheet of decals is included to adorn your favorite model! The 21cc engine comes with everything needed for installation in nearly any aircraft.
The casting and machining looked really nice, without evidence of pitting in the casting, and a single piston ring seals the piston to the cylinder wall. Though not necessary, I would have liked to see the exhaust port face machined.
I like the fact that RCGF has situated the carburetor to provide a straight throttle pushrod connection - this will make installation much simpler. RCGF has also included a long throttle arm on the carburetor, which will help during setup of the throttle servo. Though the carb is of the company's own design, it shares many similarities with a pump-type Walbro carburetor.
The aluminum expansion mufflers looked nice and look like they'll fit well. RCGF has included their new twin cylinder ignition module, which is capable of handling up to 8.4 Volts input. This is a nice feature for modelers that like to use LiPo and LiFe batteries - now this can be done without the need for a Voltage regulator! Aluminum standoffs and mounting hardware is also included with the 21cc engine.
Because of the relatively small size of the engine's cylinders, RCGF has down-sized the spark plugs to the 1/4-32 plugs. A metric nut and knurled prop washer should hold the propeller securely. With the carburetor and reed block removed, I inspected the lower end of the connecting rods and needle bearings. Everything appeared to be in good shape!
The reed block supports two reeds, and both reeds were seated well against the block. As I do with any new engine, I disassembled the carburetor to look for any debris. As usual, the RCGF designed carburetor was clean!
Though the manual is not engine specific, it does a great job of covering all the basics - from which oil to use and how to perform the 'break-in' procedure to helpful tips on troubleshooting and safety. The manual I received was in full color as well!
Assembly began with removing the radial mount from the engine. I traced the radial mount onto a piece of card stock (tag board) to make a drill template.
The template was taped to the firewall of my Seagull Models Classic Ugly Stick - I chose this airplane because it was the correct size and had no cowl. With the template in place, I drilled the four mounting holes.
I reattached the radial mount to the engine and slid the standoffs onto the metric machine screws. The four machine screws went through the firewall easily - I did add a large washer (not included) before securing the nuts with a drop of ZAP Z-42 blue thread locker.
I connected the pushrod to the throttle arm on the carburetor and slid the Tygon fuel tubing onto the barbed nipple on the carburetor. The 1/4-32 spark plugs were then installed and sparingly tightened and the spark plug caps were snapped on the plugs. The plug wires were long enough that I had to loop them around the top engine standoffs, even after installing the ignition module next to the fuel tank!
That's it! Engine installation was complete, and it was time to head for the field.
Reviewer's Note: I had previously flown the Seagull Models Classic Ugly Stick with an RCGF 15cc gas engine. There is a 5 ounce difference between the 15cc and the 21cc twin, but the Ugly Stick balanced easily by shifting the ignition and receiver batteries aft in the fuselage.
Propellers and Bob's Hobby Center at Steve's Hangar
Bob's Hobby Center at Steve's Hangar is the US distributor for Falcon Propellers. They offer a full product range - i.e. gas wood props,electric wood props, carbon spinners for gas and electric applications, and carbon fiber props for both gas and electric. At the 2014 Extreme Flight Challenge, 13 out of the 15 competitors flew Falcon Props!
As well as being the US distributor for Falcon and Xoar, Bob's Hobby Center is a great, full-line hobby store with knowledgeable, helpful employees. If you're in Orlando, Florida, stop in at Bob's - you'll be glad you did! You can also find Bob's Hobby Center on the web. If you're looking for a full line of high quality propellers, look no further than FALCON PROPS!
The break-in procedure is relatively basic, and simply recommends running the engine for the first 20 minutes on the ground. With a full tank of fresh gas/oil mix (I use 91 Octane Non-Ethanol gas with an ashless 2-stroke oil at a 30:1 ration), I closed the choke, advanced the throttle to slightly above idle, and tried starting the engine. I have a cordless electric starter that I use on all my gas engines 30cc and smaller - while they can be hand started, the electric starter turns the engine over much quicker and draws fuel in just a few seconds. This was the case with the 21cc twin as well, and it was easy to see the fuel moving through the line. The engine started and quickly died with the choke closed. I then opened the choke and started the 21cc twin again. This time, the engine stayed running, and settled into a nice high idle.
I let the twin cylinder engine run for a few minutes just above idle to warm up before advancing the throttle at all. When the engine had reached normal operating temperature, I opened the throttle a little more. The engine stumbled slightly and a thick stream of smoke came from both mufflers. After a few seconds, the engine's RPM came up and it was running very nicely. Using my digital tachometer (connected to the ignition module) I adjusted the throttle so the engine ran at approximately 2,500 RPM.
After running the engine at 2,500 RPM for approximately 10 minutes, I started advancing the throttle again - the engine responded well! I ran the throttle up and down a few more times before setting it back to 2,500 RPM to run through the rest of the fuel tank. All-in-all, it took just over 20 minutes to get through the first tank of fuel. With the break-in run done, it was time to head to the flying field!
As luck would have it, I didn't have to wait but a few days for the weather to cooperate, so I loaded the Ugly Stick into my truck and headed for the field. After assembling the plane, I set it on a starting stand and filled the fuel tank. All my last minute checks were performed, and the RCGF 21cc gasser was started using my cordless starter. The engine came to life quickly and settled into a nice idle - I let it warm up for a few minutes on the stand, while I got my camera equipment ready. At this point, I handed the transmitter off to my great friend and video pilot, Jim Buzzeo. Jim put the Ugly Stick and RCGF 21cc engine in the air so I could shoot some video for the review.
The Classic Ugly Stick was taxied out to the grass strip and readied for take-off. The throttle was advanced, and the engine responded nicely, even still running rich! The airplane gained speed quickly and took off easily - it was clear that the RCGF 21cc gasser and Falcon 15x8 prop were a great combination for the Ugly Stick! Jim ran the engine at nearly every throttle setting imaginable and the 21cc twin performed well throughout the test. Still set rich on the needle, the engine did 'garble' a little in the mid-range, but that was to be expected. I would suspect that it will clear out as the needle get leaned out. Check out the video to see how well the engine ran!
When it was time to bring the Ugly Stick in for a landing, Jim brought the throttle back to idle and brought the plane down. The Ugly Stick came in a little hot, so a 'go-around' was needed. The throttle was advanced quickly and the RCGF 21cc twin responded without hesitation. On the next attempt, the throttle was brought back before making the final two turns to the runway. This made all the difference, and the Ugly Stick settle in nicely, and touched down with just a slight bounce! Not once during this first flight with the engine did the little twin miss a beat - I was very impressed by the power and reliability of the engine!
I really like the new 21cc twin cylinder gas engine from RCGF. It installed easily, had an aggressive sound, and it ran very reliably! The machining and casting work are well done, and make for not only a good running engine, but a good looking engine as well! RCGF knocked this one out of the park, and I suspect there will be PLENTY of these small twin cylinder engines at flying fields everywhere!
4029 E. Golden Acres Drive,
Sierra Vista, AZ. 85650
The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.