Oh yea, I have noticed that fuel makes a big difference in a break. If you run say 10% cool power you may get no break but put 10/29 all castor fuel in her and at times the motor will break. I tend to run 10/22 half and half most of the time and get good results but for say a Fox 35, you need the high castor fuel to get the right run.

Originally Posted by GallopingGhostlr

Here's my 4-2-4 engine, a Testors Series 21 McCoy .40 Black Head. Been testing it by retrofitting a lightweight YS muffler to cut the bark for in-city flying. Today's runs proved it runs fine without overheating.

I learned to fly well on a Voodoo with a black head 40 on a surge tank. Listening to that sucker break was like listening to fine music.

I've got some building to do, tigreflyer. Already have a Sterling 42 in (1067 mm) wingspan Profile Grumman F6F Hellcat reserved for it. Shooting for early summer first flight.

If all goes well, I'll see about videoing it.

While I have no first hand knowledge of this, I have been told that the McCoy engines were based on Fox designs so they should run very similar. With that said and assuming there is some truth behind I bet I know exactly how sweet that 40 black head sounds

Yes the timing dictates the break from 4 to 2 and back to 4. Some have softer break run faster rpm lower pitch props while other break harder run lower rpm and use a higher pitch.
And yes the fuel plays part in it too. The Castor help with keeping the motor cool and motors run away because they get hot and cannot cool down. They can also run away because poor installation improper cooling weak mounts (that turn fuel to foam).
The critical point is again what to do in order to achieve the proper response. And above all you cannot make an LA40 behave like a Fox35. They are completely different animals timed differently and behave different. But they both bolt on a Twister or a Cardinal or a Smoothie. Some planes have more wing area some thicker airfoil some are profile or built up fuses and guess what you can make either motor run fine. The challenge is to find the proper receipt for you particular slice of cake and the receipt calls for a proper prop, for proper cooling, for rigidity, for proper fuel delivery, for proper fuel, for proper needle and venutri, and the search is to find a user friendly set that is not picky and so narrow that it runs completely different with the slightest change in temperature and pressure.

100% agree

Welll said. Agree wholeheartedly with the "user friendly set that is not picky and so narrow that it runs completely different with the slightest change in temperature and pressure."

Here's my Brodak .40, 2 hole spraybar. I think it does pretty good!

Bill Davenport
AMA 28141

Brodak .40 Four Stroke Break (0 min 13 sec)

I'm hearing it friend! Your fuel system is obviously correct and your engine picks up, I'd guess maybe 800 -1000 RPM when it goes vertical. But I don't hear a classic break like one would expect from a McCoy, a Fox 35 or an OS Max S 35. Those engines clearly break from a 4 cycle to a 2 cycle. Nice plane BTW, were I to build a stunter it'd end up looking much like yours.

Hey Bill,

Nice looking plane, Vector right? The Brodak 40 sounds good. With that said, that isn't what I call a classic 4-2-4 break but I bet it does it in the air. The break has something to do with the engine loading and unloading, not going lean due to pointing the nose up I think. The "break" happens much quicker than your video. Does the plane take off in a 2 cycle and then go into a 4 cycle in level flight? This is what a classic break does and then breaks into a 2 when you do turn and the plane slows. I think this is when the prop loads up a bit more and makes it break.

Pretty much agree with all above, except that I should have clarified- The video shows what I tune for to get the break in the air. You are never going to hear the true break without a load on the prop. I also have a Stuka Stunt OS 35 with an awesome break. The plane is the Vector ARF, flies real nice.

Bill Davenport
AMA 28141

Originally Posted by badbill

Pretty much agree with all above, except that I should have clarified- The video shows what I tune for to get the break in the air. You are never going to hear the true break without a load on the prop. I also have a Stuka Stunt OS 35 with an awesome break. The plane is the Vector ARF, flies real nice.

Bill Davenport
AMA 28141

Bill it sounds a little rich still. It should sing when you get the nose up and transition a bit faster. Try to hold with the nose up and lean till it maxes out then put the model level and you should notice the drop. That will be the happy place for that motor. When you get it with the nose up it struggles to get from 4 to 2. By the time it gets to 2 you already finished the loop or you are in trouble on the wing over due to lack of response.
The question is what does it do in the air.

You will always have to fly it a couple times to get it perfect. I have about a dozen flights on the motor / plane, the video was done after I had to dissassemble and tune again after getting some crap in the fuel tank and motor- An older hypo got pieces of rubber in it. As a side note, my son and I had a blast doing this in the yard.

Bill Davenport
AMA 28141

Add a fuel filter on the intake line or clean the tank thoroughly and filter the fuel when fueling. Ceramic car fuel filters work great to filter the fuel that goes in the tank. One lean run on a motor can kill it.

Originally Posted by badbill

You will always have to fly it a couple times to get it perfect. I have about a dozen flights on the motor / plane, the video was done after I had to dissassemble and tune again after getting some crap in the fuel tank and motor- An older hypo got pieces of rubber in it. As a side note, my son and I had a blast doing this in the yard.

Bill Davenport
AMA 28141

Yep that is what I kind of figured Very nice looking Vector. My Vector is a wonderful plane.