I received an email from Jake Ruddy recently. He is in the process of writing a review of the Aeroworks Extra 35 , for RCU. And additionally he is also looking for an engine for the review.
He is considering the Evolution 35 or their new 40cc engine. That said.... he is also looking at the RCGF 45cc engine.
He asked me, what my thoughts were about the our 45cc engine. It took me a couple of hours to compose an answer that was unbiased. It is interesting to talk about an engine one knows though.
Here is what I wrote to Jake...
Hey Jake!!
Thanks for writing... The Aeroworks Extra 35 is an awesome plane. I saw a couple of them flying this summer. The pilots had nothing but good things to say about the kit. The RCGF 45cc is an excellent choice for the plane. Now for the details.
The current RCGF 45cc is our current and newest release. The big difference is the rear induction. The original 45cc had a side induction system. I have and use the older engine in my ACE Big Bingo. It has an all up weight of 19 pounds - yeah it is heavy. However, that is how Ace designed this bomb shelter back then.
You know Jake, you can read all the engine specs you want. They really don't mean anything outside of the size of the engine and cost. Here is why... Most manufactures state their HP ratings. However, instead of HP, they are actually stating Brake horse power. The difference is that Brake Horse power is what the engine will produce when there is no load on it. Few manufacturers will put out the true HP because there are so many circumstances that will affect their readings.
Also, along the same lines.. many of the gas 2 strokers are converted industrial engines. Industrial 2 strokers are designed to produce their max hp at high rpms. In our hobby that is not necessary a good thing. Our props and the physics behind them produce their maximum thrust when the propellers reach from between 70-80% speed of sound. After that, there is no gain in thrust, no matter how fast that prop is spinning.So what I am saying is that though hp and rpm are interesting indicators they have no real value in determining what an engine can do. The only way to compare apples to apples is with a dynometer.
That is expensive... (we are actually building one though... once done we are giving it to an independent tester who is well known in the RC world, and he will conduct the tests for our engines and all others that want to be tested. No bias, which is what is wanted).
Ok... so no dynometer, but there is another way. And a lot cheaper... Simply go into Walmart and or any other discount store and by a digital fish scale...
Carefully put cord around the wings of your airplane, then attach the scale. Take the reading. Will it be precise? It will be close enough. In the air the engine will unload further and provide more thrust, but this will give you a great indicator. Plus you can use this for ANY aircraft.
Pounds of thrust reading. Simple and straight forward.
Ok...Prior to the becoming the distributor of RCGF Engines, I bought a whack of them for trials. Many I gave away to friends for their opinions, some I sold at cost to customers, and some I kept. I kept three engines the 45cc 50cc and the 65cc...
I did the above thrust test to them. In fact...I did not believe my initial results... I threw away the scale and bought a new one immediately (on sale at Walmart - $14.69). I did the test again. Hmm results were the same. I called a friend and he brought his scale over. Similar.
The old 45cc was pulling 22 pound - 23 pounds of thrust. It was turning a 21/8 TZB at 7400 rpm. The old style 50cc was pulling 25 pounds, and the 65cc was pulling 34 pounds of thrust. I became the RCGF distributor right after these tests.
OK that was the older style.. Enough history.. lets talk about the new ones. The new models were introduced with little fanfare in May/June of this year and we got quantities of all of them shortly thereafter.The 45cc had the new rear induction system. With a more consistent fuel delivery system from the carb to the cylinder, the expectation was for at least the same amount of hp.The fish scale testing showed a 24-25 thrust now. Same propeller used. In fact, I believe that if I went to the 22/8 or 22/10 the thrust would be higher.
To give you perspective - the new 50cc gained - it is showing 28 pounds of thrust. We are just getting quantities of the new 62cc. Though not tested here, the factory is stating 37 pounds of thrust.
Perspectives about the RCGF 45cc engine.
1. Thrust output is the highest of any 45cc size engine I have seen.
2. The crankshaft has bearing not bushings
3. Rear induction - this provides more options for mounting the engine without cutting the sides of a cowling for access to the carb etc.
3a. Rear inductions also have the advantage of minimizing any gas spitting. Side induction and front inductions do have this problem of gas spitting out the carb.
4. The RCGF 45cc was designed for aero applications. It is not a converted design of an industrial engine.
5. Crankshaft - hardened steel. Ralph Cunningham of RC Ignition calls the RCGF cranks among the best he has ever seen.
6. The entire RCGF line up uses the RCEXL ignition system. Bulletproof and proven design.
7. The engine is light weight and powerful. It is actually lighter than the Evolution 40 (51.2 oz) and RCGF 45cc - (48.5 oz).
8. Mounting is by rear engine lugs. It allows for customized mounting, using standoffs or whatever the modeler feels comfortable doing.
9. Easy starting.
10. Walbro Carb
11. Cost is 269.99 - The Evolution cost is $500... You could almost by two.
12. Parts cost is much lower - RCEXL ignition cost is about $70. Evolution is almost $200.
13. Engine break in is simple - 20 minutes on the plane to familiarize yourself with the engine. Use 32:1 oil/gas for several hours or gallons. Then switch to a high quality synthetic. I recommend BelRay at 50:1. It will give you another couple hundred rpm once the break in process is done.
It is not my intent to compare the two engines in a side to side, outside of costs or weights. The Evolution is an good engine with a decent design. In my mind it is just WAY too expensive.
We have been flying the RCGF Engines for a couple of months now and the reliability and consistency of the motor is excellent. Reviews have been excellent on the entire engine lineup.
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