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Home✈️Aircraft🚁Helicoptere-AlignOther › What kind of headspeed can I expect out of my Trex 450?
08-02-2007 02:20 AM  13 years ago
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Prophet

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What kind of headspeed can I expect out of my Trex 450?
430xl motor, 13 tooth pinion, 3 cell lipo, 100% throttle curve.
How fast should the blades be spinning?
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08-02-2007 02:29 AM  13 years ago
ckoelliker

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3200 rpm. You need a good lipo. I personally like the FP. If you are using the align pack you need to baby it. Eventually it is going to start puffing.
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08-02-2007 02:46 AM  13 years ago
Jason Chow

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i agree with the above post. currently running that setup and love it.
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08-02-2007 03:42 AM  13 years ago
drdot

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fwiw...

Works fine on 12t also, and is easier on the batts...

JOhn.
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08-02-2007 04:03 AM  13 years ago
bigdog714

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Actualy a 13t is 2970rpm, you will need to go 14t, that will give you 3200rpm, the rpm of a 430xl with 11.1v is 34280.MD 800
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08-02-2007 04:17 AM  13 years ago
psamm

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stl mo

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another 'actually'...
Actually, 13t pinion on a 430XL motor (3700kv) is 3203rpm headspeed - 12t would be 2957rpm - these calculations are per:

http://www.readyheli.com/Online_Hea...ulator_s/81.htm

I'm running 12t for awhile - the head's pretty responsive at this rpm and batt life is good - taking out ~1400ma avg. out of my 2200mah packs in a 6 minute flight (80% soft 3d and remainder hovering manoeuvres.)
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08-02-2007 05:39 AM  13 years ago
The Daz

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Australia

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calculations are only a guide.. have you actually tacho'd your heli?

i tacho'd mine in a hover and it was about 3000rpm with 13tooth pinion. flightpower packs and 100% throttle curve with XL motor.

12tooth pinion definitly won't get you 3000rpm in a hover.

anyone that does get a headspeed like that must be measuring it without any load on it.
Feed it some nitro!, try not to get bitten..
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08-02-2007 05:56 AM  13 years ago
drdot

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fwiw..

3000 isn't a magic number..The overall flyability of the heli is important too, and the 12 gives a littel more forgiveness to the management of the collective..With good batts the hs is plenty high, and can pull +/- 12 degrees with ease, even in prolonged climbs...

John.
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08-02-2007 06:21 AM  13 years ago
The Daz

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Australia

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3000 definitly isn't a magic number, but anything over 2800 is going to fly nice with a rock solid holding tail.Feed it some nitro!, try not to get bitten..
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08-02-2007 02:55 PM  13 years ago
SSN Pru

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Taxachusetts

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I run a medusa (3400 kv) motor and a 12t pinion. I get 2950 rpm at 0 degrees pitch. I assume it drops a hundred or so rpm once in a hover and under load but I dont have any means to measure that.

I used to use a 13t pinino but switched to a 12t to try it out and haent noticed any performance decrease.
Stupidity can be cured. Ignorance is for life!
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08-04-2007 08:39 PM  13 years ago
psamm

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stl mo

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"calculations are only a guide.."

Thanks for that brilliant bit of wisdom - I'll make sure to tell the nuclear physicists and space shuttle guys that 'calculations are only a guide'!

What part of cell count, main gear teeth count, pinion teeth and KV ratings are just a guide? Are any of the actually tach'ed headspeeds really that different from the calculated speeds? NO! Maybe a couple of percentage points off at the most...

I love forums - if you can say something with enough conviction it might look like you actually know what you're talking about...
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08-04-2007 11:39 PM  13 years ago
SSN Pru

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psamm,

He was talking about the fact that the figures you use are ideal. in reality, the rpm you calculate IS going to be different if you dont use a much more indepth analysis on the rpm under LOAD...

the simplest form of rpm calculator circulating usually only account for the ideal situation and some fudging of numbers based upon experience is used to get the actuall number

RC helis and aerospace vehicles dont require the same amount of engineering. Im sure if NASA was interested in doign an RC heli on mars, they would definitely carry out the most complex, expensive and thorough analysis there is.

For our purposes, fudging the ideal numbers a bit gets the job done.
Stupidity can be cured. Ignorance is for life!
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08-05-2007 01:21 AM  13 years ago
The Daz

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Australia

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Are any of the actually tach'ed headspeeds really that different from the calculated speeds? NO! Maybe a couple of percentage points off at the most...
you would be surprised.. that particular formula as umdpru has pointed out is not accounting for resistance and also load.. it's basically just a formula us knuckle heads use the actual rpm will vary considerable. anywhere from 200 - 500 rpm in some cases, maybe more.
Feed it some nitro!, try not to get bitten..
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08-05-2007 01:59 AM  13 years ago
SSN Pru

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Taxachusetts

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I love forums - if you can say something with enough conviction it might look like you actually know what you're talking about...
This trait of yours is pretty apparent, that disclaimer wasnt required.

Before you come around telling people the way it is, make sure its the right way
Stupidity can be cured. Ignorance is for life!
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