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HomeAircraftHelicopterMain Discussion › Excel Chart for head speed.
01-21-2015 06:44 PM  3 years agoPost 1
rotoryrob

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Auburn WA

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Does anyone have a good chart for figuring out head speed based on KV and gear ratio's. They used to be all over the place I am having difficulties finding one online.

Rotoryrob

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01-21-2015 06:47 PM  3 years agoPost 2
MattJen

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UK

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http://www.modelhelicopters.co.uk/s...speedcalculator

there is one, there are many others...

All The Best

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01-21-2015 06:53 PM  3 years agoPost 3
rotoryrob

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Auburn WA

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Thanks
wow that was fast and exactly what I was looking for.

Rotoryrob

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01-21-2015 07:02 PM  3 years agoPost 4
MattJen

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UK

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Your welcome Rob.

It can be frustrating finding info sometimes.

I will say the guys in the Electric forum were very helpful when fact finding gear ratios etc and motors..

They gave me this formula which helped..

RPM = kV x (3.7V x # of cells) x 0.9 (efficiency) x pinion teeth / main gear teeth

So, for 10s, 520kV, 10T and 114T;

RPM = 520 x 37 x 0.9 x 10T / 114T = 1519rpm at 100% towards the end of a flight. Aim to govern between 90 and 95%, so between 1367rpm and 1443rpm.

All The Best

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01-22-2015 01:01 AM  3 years agoPost 5
EEngineer

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TX

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Doesn't main rotor diameter enter in?

Especially with a little pitch applied?

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01-22-2015 01:17 AM  3 years agoPost 6
dela

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Stillwater Oklahoma

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EEngineer,

The 0.9 (efficiency) number in the equation is a really "fudge factor" to account for all kinds of misc effects. That number is reasonable for reasonable configurations, and would be absurd for absurd configurations (absurd blade diameters for example)

Ron D.

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01-22-2015 01:26 AM  3 years agoPost 7
EEngineer

rrProfessor

TX

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Thanks

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01-22-2015 02:19 PM  3 years agoPost 8
cudaboy_71

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sacramento, ca, u.s.

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googling mr. mel's headspeed calc always pulls up Fredrik's for me.

if it ain't broke, break it.

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01-22-2015 05:44 PM  3 years agoPost 9
jason46

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MI

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I started using this one.

dhrc.rchomepage.com/calcAdvanced.htm

Actually, I've been using the mobile version..

dhrc.rchomepage.com/calcMobile.htm

We made up some rules can we have your moneys now.

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