Jazz 55-32-10 question

[panomaniac]

Today I have made first flights with my Maxi Joker 2 cameraship, but i still don't understand electrics enough, so I would appreciate your help guys:
I have set desired head speed with throttle curve to around 65% and got 1340 RPM with fully charged 10s4p TP packs. After several short flights (setting up gyro, blade tracking, dual rates etc..) I have noticed that RPM is much smaller. Took tachometer and measured 1260 RPM. SO, is it normal for Jazz (or for ESC generally) that after voltage in battery drops a little that RPM on second-third flight drops too. If that is the case, what is my target? To set throttle % to fully charged battery, (4.2V/cell)? If I make only one long flight to about 80% capacity of TP8000 pack, will RPM be the same entire flight or that drop in RPM is just noticeable in more that one flights on same battery pack.
I hope I didn't complicated question too much. I can barely repeat that on my mother language

[flyingrhino]

It's perfectly normal to lose head speed as voltage in the pack drops. However you need to make sure you are not taking too much out of the battery. I try to end my flight before I notice a drop in head speed as not to damage my batteries.

[panomaniac]

Thanks, but that it not what i have asked. I know that at HS will drop at the end of battery capacity, but does HS drop proportional as voltage is dropping during flight, or this happen only at the end of the (too) long flight? Next, I just wanna know if you make several short flights (1-2min) will HS be that same at lets say third flight as it was at the first flight?

[Tonystott]

Everything I have read suggests that ESCs should not be set to run at less than about 80%, so if running a higher throttle curve gives too much headspeed, it is best to go for a smaller pinion. This will make motor, battery and ESC work better, generating less heat. I know this isn't directly answering your question either, but you should get a longer duration overall with a smaller pinion. Maybe this will make your question unnecessary?

[GGoodrum]

The pack voltage will drop within about 20-30 seconds to a "nominal" voltage that is around 3.7V per cell. Fresh off the charger, however, it will be higher, which is what you are seeing.

I also agree with Tony, that your system will be much happier if you use a smaller pinion and set the governor up around 80-85%.

-- Gary

[jlr]

Everything I have read suggests that ESCs should not be set to run at less than about 80%From what I've read, it is okay to run the Jazz ESCs at less than 80% in heli mode. (Other ESCs may overheat if you're not at 80 or above)

As far as the headspeed loss, I suspect it is due to the way the Jazz works. Each time you spool up* the Jazz attempts to establish a headspeed based on the battery voltage etc. Once it is "locked in" it will hold that headspeed. That is why every time you spool up a Jazz you're supposed to move the throttle to the desired setting with the pitch at 0deg until the headspeed stabilizes (about 8-10 seconds) before flying. If you don't do that then your headspeed will vary, because the Jazz is trying to determine how much headroom to allow for the current battery.

*If you were "resetting" the ESC between each short flight (with the same pack) then it may be this headroom determination that caused the variation. Or, I'm not sure that the Jazz does this, but it might do the headroom determination each time you spool up from 0% even if the ESC wasn't reset? :dontknow

Some people have complained that they wish the Jazz would always produce the same headspeed for a given throttle % instead of working the way it does, which can cause a different headspeed for different packs.

--Jeff

[AZ ChopperCam]

keep in mind that the percentage value on your radio is not the percentage that your esc is running. On my 9C I am at about 70% on the throttle curve but the esc is at 100%.

Dial down yoru radio until the esc is just below 100%. Usually most esc have an LED that is illuminated at 100%. Drop the radio values until that light just barely extinguishes and that is your 100% value for your particular radio setting. You can then interpolate the true values from there.

did that makes sense??

[Menno]

I don't know about the Jazz ESC but you could check the following 2 things:

1. 100% throttle on you Tx is not alway 100% throttle on your ESC. Start with a high throttle value and dial it down on your Tx till you hear the RPM drop. That way you are certain that you are not flying at max headspeed. You will expirience a drop in rpm's much sooner when you start out with the ESC at full throttle.

2. Some ESC (don't know about the Jazz) have an 'automatic' full throttle function, so 65% of a full battery is not the same as 65% of a battery which already has some flights on it.

Hope this helps.

Menno

[Menno]

Wow, by the time I got my message typed Jeff and DJ typed about the same things. I guess that would count for double posting :roll:

[panomaniac]

There are few good info I didn't know, like tis one from Gary:
"...The pack voltage will drop within about 20-30 seconds to a "nominal" voltage that is around 3.7V per cell. Fresh off the charger, however, it will be higher, which is what you are seeing..."

That is what probably confused me. I checked RPM in first seconds of the first flight, because I thought that Jazz is determinating HS then and it remains the same all the flight. Ok, I will do more tests tomorrow, measure HS in 'nominal' voltage, and if it is to high at 85% throttle range, i will dial it down with smaller pinion. Also, as DJ and Menno sugested I will try to find 'real' ESC %.

Today I have made few short flights with mount under Maxi, and I thought it will came apart. There are one resonant point in spooling up (and down), and as far as I can see by now it is related to pitch input. I remember that it was discused in early topics. There is some trick with throttle hold on spool down. Must check that too. Phew... so much more stuff to learn :arggg: