Originally Posted by Koala2
@Chap2012 : nice site but still no answer ...
It doesn't seem to be something a lot of people really know in detail.
OK, the bigger the figure the bigger the heli, except when we come tot the really big guys.
From the NE site it seems that 100 series stops at 33 cm rotor diameter and the 150 series at 49 cm. and then ... nothing anymore ...
It's just that it's been posted dozens of times, on RCG and elsewhere. Helis were referred to by blade length- 700, 600, 550, 500, all by blade length in millimeters. Then there were by engine size for glow helis-- .30 engines meant 500 to 550 mm blades; .50 or .60 were 600 to 640 mm blades; and .90s go for 640 to 700 mm or more. When the electrics came along, they were advertised based on the motors they ran, 400s, 450s, and so on, and then Align decided to promulgate "500" helicopters with 425mm blades and no 500 motors in sight for years, either to help advertise their products or to confuse generations of new helicopter fliers (you choose).
Anything below a "450" (a 325mm heli) is pretty much arbitrary, and companies can pick what they want, but it really doesn't matter when they're that small; anything above that, unless it's the BS Align "500," is the length of the blades in millimeters. It's easiest to talk about blade length or all-up weight. For me, among others, I have two 425s (what Align would call a 500), one upgraded to a 480, and I have a 520 that I've stretched to a 600. And a 600 that I'm thinking of bumping to 680. It's much simpler if you talk about them by the blade length and not a marketing term.