450 Understanding Heli Tail Ratio

namaspilot

namaspilot

Member
Hello Tony,

It's been so long since I got back into the game, I seem to have forgotten many things in this heli hobby. Either that or I'm getting really old.

I was wondering if you could help me out, on how to work out heli tail ratio. For example: the following helis has these tail ratios:

Gaui X3 (belt): 4.71:1
Protos 380: 4.47:1
Blade Fusion 360: 4.59:1
KDS Chase 360: 4.73:1
MSH Protos Mini: 4.29:1
JR Forza 450: 4.29:1
Goblin 380 3.6:1
Trex 470LM 3.7:1(Stock). With KC3d Speed up tail pulley upgrade: 4.46:1
Oxy 4 Max 3.66:1

My question is, what is the formula to work out those tail ratios please?

Thank you
 
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Tony

Tony

Staff member
You divide the number of teeth on the auto gear by the number on the tail. Just like doing the final drive ratio of the head, just take the main gear and divide it by the pinion. Sounds simple, but counting all of those teeth is a PITA lol. However it should be in the manual on how many teeth are on the gears.
 
murankar

murankar

Staff member
The tail ratio directly reflects what head speeds you can run. I think higher tail ratios means lower head speeds. It will also play into tail blade size.
 
namaspilot

namaspilot

Member
IMO 3000HS is the sweet spot for most 450 helis. But I understand, there are pilots out there that would like it to run lower than that. 2500-2800HS. I take it they are mainly sport fliers looking for a longer flight time? Hence they would need a high tail ratio heli like the X3, Protos, or Forza 450, may be even the Chase. There is the exception to the Align 470L with the added KC3d speed up tail pulley. Which I never tried that tail pulley.
 
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murankar

murankar

Staff member
I ran as low as 2700. The original x3 is a heavy kit. My oxy 3 I am running at 3000 and the oxy 2 is somewhere around 4000.

In had the oxy 2 lower but it seems to fly way better at 4000.
 
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