Lack of head...

[jimbob]

...speed.

I'm having trouble getting my head up - on my T-Rex450 that is.

I can only manage 2400rpm with the following setup and I want to get it up higher.

Aon 3500KV motor with an 11T pinion.
10c 2000mAh 3S1P LiPo
Jazz 40-6-18 ESC
Align 325 Pro Carbon mains

The throttle curve doesnt make any difference over 86%...

Anyone got some Viagra for my bird?

[gazza]

Pinion maybe mate?

Try this http://www.readyheli.com/Online_Head...lator_s/81.htm

[moyesboy]

11T should be OK with a 3500kv I think
10C is a bit weak for a trex and swinging 325 blades (though probably 315 from bolt hole to tip?)
with 325 carbons my "trex" bitsa pulls 17A in the hover and 25A on full pitch so you are probably close to the discharge rating in the hover.
Even if it is not the battery that is limiting the power after 86% the battery isn't goung to last many flights...
How hot is the battery getting?
The jazz and that motor will be trying to pull lots of amps I think

[jimbob]

Looks like I need a 13T pinion - thanks for that Gazza - good website

[jimbob]

11T should be OK with a 3500kv I think
10C is a bit weak for a trex and swinging 325 blades (though probably 315 from bolt hole to tip?)
with 325 carbons my "trex" bitsa pulls 17A in the hover and 25A on full pitch so you are probably close to the discharge rating in the hover.
Even if it is not the battery that is limiting the power after 86% the battery isn't goung to last many flights...
How hot is the battery getting?
The jazz and that motor will be trying to pull lots of amps I think

I dont know what amps I'm drawing - i'm pretty new to this electric nonsense - i still try and put 30% in the T-Rex

Gazzas calculator says I need 13T for 3000rpm, and the 11T i have will allow for 2500rpm.

I am thinking of going 4S soon, but what battery do you recommend instead? (Its true that mine's a cheapo JP/Deans battery too)

[gazza]

Looks like I need a 13T pinion - thanks for that Gazza - good website

Pleasure mate

Regarding Lipo purchase dont rush into anything, as you've probably read Mike @ aurorra has a new range out in a couple of weeks.
I cant say any more at this stage but I would definitely wait

[Smoothound]

13T pinion will kill those packs. Should give close to 3000rpm up top

11T with losses should give you around 2500 head speed, as its less than this I'd say your packs are certainly sagging. Stick a 13T on without proper 15/20C packs and those ones will die...

Sorry

[jimbob]

Don't be sorry smoothie - its what I needed to know
I only bought the Rex for a bit of fun - I've got 4 nitros too - but its more fun than I thought
I shouldnt have bought such a cheapo battery it seems!
I'll wait and see what Aurora come up with then - cheers Gazza

[Smoothound]

Mate has one and settled on 12T because on 13T on various cells the batts got a bit too hot

[gazza]

Mate has one and settled on 12T because on 13T on various cells the batts got a bit too hot

I should be okay with the 13T with my 2170 25C Flightpowers tho shouldnt I mate?

[moyesboy]

yes, you should get 3 or 4 cycles out of those flightpowers at 20C, maybe one loud one at 25...

[Cralis]

I have 13 teeth on my little 'gold' cog. That's the pinion? I then have the brushless Align 430L, and will be using Kokam 2000 11.1 15c packs. Is that 13 teeth thing OK?

The more the teeth, the faster the blades, right? So wy would you not want more teeth so that you have that exta bit if you need it? Maybe harder to tunr the motor with more teeth?

Surely a better way to increase headspeed is to decrease the size of the main gear?

[Cralis]

That calculator you sent gives me the following:

Battery Pack: 3S-11.1v
Main Gear: 150 teeth
Motor: 13teeth
Kv: 3550 (Align 430L)
Drag: .90% (What's that!? Blades related? Pitch?)
Head Speed: 3074

So, does that mean that at 0 pitch, 100% power, my blades would spin at 3074 rpm? As a novice, doing hover/scale flying, surely that's pretty quick. What sort of headspeed should I be trying to get? Around 2,500? If so, would I simply not ever set my throttle curve to hit 100%, but rather 2,500 / 3,074 * 100 = 81% ?

[jimbob]

Yeah - the 'little gold cog' is the pinion

The gearing gives you the headspeed vs the current basically.

Imagine you want to ride up a hill on your bike? If you want an easy life choose a low gear but you;ll get there slowly.
If you want to get there fast, choose a higher gear, for the same pedalling speed, but you need to put more effort in.

If you have a motor that can run with more power (you're lance armstrong on his bike) (and a battery and ESC) you can get a more powerful heli with a higher headspeed.
Higher headspeed gives you more power and stability.

You will be ok at 2500 if your learning.

(long post... sorry)

[Cralis]

So is setting throttle on the curve on point 5 of the throttle curve to 81% correct to achieve ~2500rpm?