700/90 size heli headspeed ........

[jgeorgic]

What are some of the headspeeds that you are running on your 700/90 size helis for both normal and idle up ?
This would be checked with a optical tach
690 V's
:fly

[Gscott]

Alot of factors to consider. I don't know the gear ratio of the 700 but my guess is around 8.27. That would give you a safe max of around 1950 for an OS and 1850 for the YS SR. The 90 engines don't like to spin as fast as a 50 so you need to keep the engine RPM less than 16k. For the SR I seem to recall between 15,200 and 15,500 was the optimal range.

[DavidH]

http://www.osengines.com/engines/osmg1983.html

http://www.yspartsandservice.com/pdf/YS91SR.pdf

For headspeed, divide RPM of engine by gear ratio of heli. If it is 8.27
Then Engine RPM/ 8.27 = rotor head speed


David

[Mercuriell]

The gear ratio of the T700 is 8.2:1 - HS depends whether you go for the 690 or 710 blades also - on the Stratus 90 with 710 blades 1750 is sedate - 1850 is sport and 1950 it's a live wire so I would guess for the T700 with 690 blades ~1900 is a good starting point for a performance configuration and would give an engine speed of 15580

[Finless]

Well a warning here guys... Dont go too much over 2000! You don't need that on a 90 and you want to run your engine in the proper RPM band... Oh and the Align tail grips don't like it either (starts kicking)! This is not an electric.......

Bob

[OTA]

So on electric.......there`s no absolute maximum, just up to the gearing/motor choise ?
Assume the blades have a "guaranteed" maximum. However, with approx 25% more blade area than a 600 length blade, i would assume around 2000 would be plenty power, or ?