Ecalc for warmliners

[austin]

I've become lost in the Ecalc sauce.

When looking at props on Ecalc for a warmliner/hotliner what values do you focus on? Some say they look pitch speed, some say est. vertical speed, thrust-weight, etc. What do you guys find best?
I try to keep efficiency around 70%+, should I? I also look at temps even though its a 3 second burst of throttle rather than traditional throttle application but what do I know.

Much appreciated!

 

[Yotaman1985]

Im sorry I dont have an answer to your question but Im interested in hearing the answers as well. Starting to dabble with Ecalc a little...

 

[Wayne]

Heck - I'm curious too.

I know for "glider thermal" stuff it is common practice to push a motor well into the hair dryer simulation levels knowing you are only going to run the motor for about 15-20 seconds. Just short enough to avoid total heat absorption into the mass of the motor. An aggressive hotliner setup seems to be on this same logic, but a much shorter period. But honestly do not know what the "goals" are going to look like in ecalc. To some extent you are going to push up against the amp limits of the windings themselves.. You don't want to melt the insulation on the motor windings. The other issue is making sure the magnets don't get hot enough to damage them, for most motors this is around 80c, for motors with better magnets this can be pushed up to about 95c.

I would assume the motor winding limit it going to be a hard and instant fail when you find that limit. The magnet limit is going to be a slower death where the motor kv will slowly rise as the magnets fail and this rise will speed up the magnet death. Jarron had a Mega motor he managed to completely kill the magnets in, they had nothing left at the end. Mega fixed it up!

The other issue is keeping a speed control happy with some of these crazy setups. I know the German guys doing the speed cup with some insane setups had major issues keeping the ESCs running. I'm not that savvy on all of that, but as I recall it had to do with the inrush of power into the esc blowing things to bits.

Curious to see what Jarron can teach us.

 

[markspark]

Since warmliner/hotliners are essentially vertical dragsters, I focus on vertical speed and thrust/weight.
I use warm/hotliner power setups in flat-land E-gliders for max vertical climbs back to altitude between unpowered aerobatic sequences.
Since my goal is to do as many unpowered maneuvers as possible in a given time period, quick powered climbs are crucial.

 

[austin]

Thank you Mark! Do you look at other parameters like, Amps for ESC limits, Efficiency %, or Wattmeter Power? Do you have an example of something? that would be really helpful too.

I've been told not to go over ESC wattage but motor watts should be no more than double the manufacturers stated limits. I don't know if that is any good either.

 

[markspark]

Yes, I keep an eye on amps and use a wattmeter to double check the actual setup.
Since warm/hot liners use very short bursts at full power it's actually easier on the ESC than running longer at half throttle.
I exceed the mfg ESC limits, but only by what the temps allow.
Motor temps are important too, and hard for Ecalc to accurately predict due to variations in cooling vent setups.
I haven't paid much attention to efficiency, although that does have an effect on temps.
I also check in with Jarron here at Aloft for power advice. He's been super helpful, especially with cooling ideas.

 

[smirkracing2024]

I find Ecalc a little overwhelming. My cheat code is simple: there are setups which are basically 'known good' for a number of different airframes. Here's one example:

(overview) https://www.f5b.cz/en/Backfire-2-F5F-3/
(motor setups) https://www.f5b.cz/en/Mounting-4/

They even publish climb rates. So, I use those as a starting point. You obviously have to take into account your airframe vs the one for which the setups were created, and think through weight differences, etc. But all of that can be done in a spreadsheet or even via AI.

That can get you into a reasonable ballpark, and then you can use a wattmeter + very conservative testing to further dial-in your setup.

What airplane are you building? In the "high performance" section on RCGroups or elsewhere, there might even be known good setups for your specific plane.

 

[markspark]

That's a great point about starting with 'known good' setups for a given plane.
I usually have to start from scratch as the gliders I use for unpowered aerobatics rarely use high power setups.
But, they do have larger fuselages allowing me to use big outrunner motors instead of the typical warm/hotliner setups.
That helps with managing heat so I can push them a little harder.

 

[Wayne]

Not sure I mentioned it, but total events per minute to be watched also. Ecalc is good about warning you when you are getting up there. Basically this is when the ESC is in danger of losing sync with the motor.

I was running some "interesting" combos the other day and hit this wall a couple of times. This is usually high kv motor on a bunch of voltage. gear drive or not this is an ESC limit.

 

[Jarron]

I like to look out for thrust to weight and climb rate. You can look at speed too but you're going to need to know your aircraft wingspan, wing area and play with the drag coefficient. For that I usually just set it to the coefficient setting and add another zero (0.006 instead of 0.06)

 

[austin]

I like to look out for thrust to weight and climb rate. You can look at speed too but you're going to need to know your aircraft wingspan, wing area and play with the drag coefficient. For that I usually just set it to the coefficient setting and add another zero (0.006 instead of 0.06)

Thank you Jarron. Can you tell me more about adjusting the drag coefficient please?

 

[Wayne]

Change the setting to "coefficient" It defaults to something like "simplified", then change the number down to .006. This will get you down to a more realistic amount of drag for very clean gliders. We don't have things like fat fuselages, landing gear, etc.