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Old 05-07-2012, 10:19 PM   #1 (permalink)
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Default Replace pinion - increase flight time?

Hi
My heli is a 450 FBL V2 with 3GX with:
stock motor 3400kv, stock 15T pinion and stock blades.

I reach 10 min with 2200mah, only hovering and FF, scale flight.

If I replace the 15T pinion for a 13T pinion. So the HS will decrease. Could I increase the flight time? Maybe 12 min?

Thanks
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Old 05-08-2012, 08:09 AM   #2 (permalink)
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Unless you are throttling back a lot on the throttle curve, your headspeed will be high;

3400 x 11.1 x 0.9 x 15T / 150T = 3400rpm at 100%

At this headspeed (or even close to this) for 10 minutes you may be running the 2200mAh lipos very flat, and if so, you may be damaging them badly.

I run 2500rpm, and get 8 minutes on about 1500mAh, so if I ran for 10 minutes, I would be exceeding the 80% of capacity.

Rather get more lipos than kill yours by over-discharging. But yes, a lower headspeed would certainly allow longer flights.

Colin
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Old 05-09-2012, 08:02 AM   #3 (permalink)
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Colin, thanks for your reply.

So with 13T...
3400 x 11.1 x 0.9 x 13T / 150T = ~2950rpm at 100% = less HS = less power?

no longer flights?

And how do you run with 2500rpm?

Thanks,
Marco
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Old 05-09-2012, 12:55 PM   #4 (permalink)
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Default same setup but FB

just recently I replace my 450M with 450MX. My old 450M fused with 14T and now my new 450MX with 15T. I hvnt took it 4 flying yet but on the bench it felt powerfull compare to 450M + 14T and I afraid that the stock ESC cant coup with it. I was thinking of just make do for a while with 450MX + 14T.......hovering and just into FF........
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Old 05-09-2012, 04:18 PM   #5 (permalink)
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Quote:
Originally Posted by MVheli View Post
Colin, thanks for your reply.

So with 13T...
3400 x 11.1 x 0.9 x 13T / 150T = ~2950rpm at 100% = less HS = less power?

no longer flights?

And how do you run with 2500rpm?

Thanks,
Marco
Use a smaller pinion. I use a 12T and Scorpion 2221-8 (3595kV) on my 450, and govern to 2500rpm with my Ice 50. You probably don't want to use the ESC to lower the headspeed below 70-75% of the 100% value - it can run run, especially if it does not have a decent heatsink.

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Old 05-09-2012, 05:12 PM   #6 (permalink)
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Quote:
Originally Posted by MVheli View Post
Hi
My heli is a 450 FBL V2 with 3GX with:
stock motor 3400kv, stock 15T pinion and stock blades.

I reach 10 min with 2200mah, only hovering and FF, scale flight.

If I replace the 15T pinion for a 13T pinion. So the HS will decrease. Could I increase the flight time? Maybe 12 min?

Thanks
If you flying for 10min on a 2200mah , you are probably killing your lipo. even if its just hovering. What's the resting voltage on the lipo after landing?
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Old 05-10-2012, 04:53 AM   #7 (permalink)
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Quote:
Originally Posted by Spork01 View Post
If you flying for 10min on a 2200mah , you are probably killing your lipo. even if its just hovering. What's the resting voltage on the lipo after landing?
You are probably correct in this instance, but it is not a given.

I typically put back about 180mAh per minute, so 10 minutes would be 1800mAh (just checked my logs), which is 81.8%, so if I dropped from 2500rpm to 2450rpm, I would probably be below 80%.

My guess is that with the headspeed the OP was likely to be running, he would be getting close to 100% though, which certainly would be killing the lipos (as said in post #2)

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