what is the most powerful cox .049

This is one of my pet peeve topics because I understand the Torque vs HP relationship. Too many people falsly think HP the one and only definition on the power of a motor and make their decisions about the goodness or worth based on HP only.

Dinsdale is correctly making analogies to explain the USEFULL POWER Band (a measureable not calculated chariteristic called torque)

If peak torque is at 12,000RPM with a spread from 10,000 to drop off at 15,000 on the .049 then the fact that peak HP at 18,700RPM has little comparitive value as by then the tourque has dropped to half its peak

Of course for non throttled engines most of this is just good to know information. But if comparing throttable engines, the better comparison is always torque. The peak is important, but more important is how broad the power band is below peak and until it again falls below peak

Sophisticated modelers are starting to use variable pitch propellers to keep their motors producing peak effeciency providing more thrust while saving fuel and engine wear from max RPM WOT runs

Surfer_kris wrote:I run my .049 engines "in the real world" all the time...

I have heard of road trains, even though we don't have them here locally. I just don't think that they have anything to do with our CL engines. You should at least compare two engines of the same cylinder volume for a comparison...

I only used the truck/Ferrari juxtaposition to illustrate the point, and the point wasn't to become such a literalist. Bringing it back to .049 Cox engines, when you do the diesel mod you usually sacrifice some revs, but the increase in torque allows you to spin a larger prop, and iirc, with more pitch too. That gives a Cox .049 a whole different character. Fewer revs, more torque and, I suspect, more power.

Any'ow, everyone else understood what I what trying to say. It's all yours now - I'm outa here.

EDIT: A couple of you posted whilst I was composing all this. This my last post (no pun intended) on the topic.

fredvon4 wrote:
Of course for non throttled engines most of this is just good to know information.

No argument there...

fredvon4 wrote:
But if comparing throttable engines, the better comparison is always torque. The peak is important, but more important is how broad the power band is below peak and until it again falls below peak

In a car yes the torque is important, but not so much in airplanes. You will use a prop that takes you into the powerband of the engine, and you are then getting the most power out of you engine. Just take a look at the engines used in pylon competitions, if you're not around the 30000 rpm mark with your engine you are left in the dust. You measure the power by taching the engine for a known prop-load. Just like what was done here in the Tach-race a few weeks ago.

Who wants to see a "torque-race" with Babe Bee engines?

Ah now you add an anology of pylon racing and running a engine at WOT max RPM. IIRC most of those guys use a tuned pipe....hummm I wonder how many here know what one is, how it is developed, and what it does to the TORQUE band? Anyone ever ride a 2 stroke dirt bike "on the Pipe"?...real fun to go from 42 to 69 HP in a micro second

Not entirely related to what is most powerfull 049 but a signigificant factor is propeller weight as well as diameter and pitch as well as thin vs thick or profile shape

I bet if I had the stuff to measure with, I could run a 049 with same diameter and pitch props to near the same peak RPM but measure different toruque curves and HP calculations
just by changing propeller weight and profile

Pylon, FF, Q500 etc, with or without tuned pipes, are a lot closer closer to CL than trucks and dirt bikes, as I see it. A tuned pipe will also increase the torque if that's what you are after...

fredvon4 wrote:
I bet if I had the stuff to measure with, I could run a 049 with same diameter and pitch props to near the same peak RPM but measure different toruque curves and HP calculations
just by changing propeller weight and profile

The prop is an external load, it will not do anything to the torque and power curve of the engine.

gcb wrote:Re: the Tee Dee .049 vs the .051...if I remember correctly, the .051 was intended to have the same power so engines could be switched in FF models and compete in both 1/2A and A with the same plane without making trim adjustments.

George

You remember correctly. Looking back, it appears that the FF market was the big driving force in Cox development of PERFORMANCE engines. More then CL & RC it seems.... at least in my circles (pun not intended) 1/2A CL was not a big thing in contest flying.

Surfer Chris said "The prop is an external load, it will not do anything to the torque and power curve of the engine."

This is not true from a measuring HP point of view. ( the statment is very true about torque and indirectly makes my point)

I assure you given all 6 inch by 3 pitch propellers I can make any given 049 calculate out to differing Peak HP due to the fact some prop designes will spin to max RPM faster or slower than other profile/design

However this more or less proves the point about HP not being a very reliable comparison number. On a engine dyno, generally speaking, all the 6 inch 3 pitch props will have a MEASURED torque band very similar

All this is interesting but still the fact remains no matter how we may agree or disagree on the method or test or the factor we choose to compare, the 049 TD series is torque or HP king over the reed design simply because all IC motors are air pumps and the TD design passes more air per unit of time than any reedy can. This allows a much broader selection of propellers

Specs are one thing... each engine is different however.

fredvon4 wrote:Sophisticated modelers are starting to use variable pitch propellers to keep their motors producing peak efficiency providing more thrust while saving fuel and engine wear from max RPM WOT runs

Just like a CVT on a car.

well I hope I didn't spark all this, oops if I did but it is interesting, I have to disagree about this statement
"dinsdale wrote: With respect to reciprocating engines, horsepower (power) is simply a calculated number. Quite meaningless in the real world actually. Power = torque x rpm x K (a constant). maybe not HP so much as prop pitch which is a must know for LC,
So from a LC point of veiw, I guess the other factor is speed, if the engine type, TEE DEE .049 will say, and performance ... and plane model were constant as well as conditions, then the only thing we can change is our gears(the Prop)so it is very important to know what speed a 5x3 turning at 21,000RPM(according to the chart) or a 6x3 turning at 18,500RPM will create.

Hmm no one has any thoughts, TEE DEE with a 5x3 prop at 21,000 or a 6x3 @18,000RPM, which will give fastest actual air speed,

I know according to the charts Tee Dee makes most power at 21,000 RPM, but what about speed?

So is the answer to maintain sweet spot of max power band of that engine to maintain max speed, so in this case use a 5x3 prop on A TEE DEE ?

And on that note what is sweet spot on the regular Bee's

The fastest speed will depend on the plane it is in. The 5x3 spinning at a higher rpm will travel faster before you reach the pitch-speed (i.e. the speed at which the prop is not pulling anymore). So on a sleek plane the 5x3 is faster, while on a draggy plane the 6x3 might be faster as it pull stronger at slow forward speed.

On a really sleek plane you would use a 4" pitch though. It's all part of the fun testing for each plane...

I was running TEE DEE on 5-1/4x4 Top Flite Nylon Prop, slim curved tip blade, and had it on the a LiL-Satan on standard length line for regular Bee's and found it was just way to fast to even control it safely.
But the regular 5x3 safe tip prop from cox was running even higher PM then the nylon above.