Which pinion for my Swift 16?

[slopecat]

I just started my first helicopter build - a Swift 16 kit. I need some advice on which pinion to use. I purchased the kit from the Century booth at the expo in Toledo last month. I explained what kind of flying I will be doing and that I would be using FlightPower 4S 3700mAh packs. With that knowlege they swapped the standard 9 tooth pinion for a 14 tooth pinion.

Now that I am putting this together and learned how to estimate headspeed, I have my doubts as to whether the 14 tooth pinion is right for me.

Background:
I am a new pilot that has been hovering for a couple of months. I am now ready for forward flight. I have no plans for any kind of flying even close to what would be called '3D'. Just the basics for quite a while.

Calculations:
Motor: Century Lightning 600+, 1110 RPM/V
Blades: Standard wood blades with standard head

1110 RPM/V * 14.8V (4S pack) / (96T/14T) (gear ratio) * .9 (efficiency) = 2,156RPM headspeed

Does that sound right for me? I am thinking that is much too high. I thought you would never want to turn the standard wood blades that fast for one thing.

I am thinking a 12T @ 1,848RPM or a 11T @ 1,694RPM should have been what I ended up with. Opinions?

Thanks,
Mike

[ddheli]

you're right, but i'd like to add: rpm's is really depended of pich, battery type and etc.- for exact numbers you can use online calc here http://dhrc.rchomepage.com/calcAdvanced.htm
for hovering-normal flight 1700-1800 rpm is enought. for aerobatics and light 3-d must be 2000-2200 (at 515-520mm blades).

[Greybird]

I fly my set-up which is like yours on 11 tooth. Head speed is 1750 or so. Plenty for flying around. I fly circles, figure 8's and back and forth only. Higher head speed will eat your battery even faster.

[Greybird]

I use 2 4S 4000 packs in parallel for 15 minute flights. Flys better than you might think with that brick of a battery. In my opinion, any flight less than 10 minutes is pointless.

[JustPlaneChris]

Greybird, what kind of flying do you do with that configuration? I'm still undecided between a 4S or 6S setup. I'm beyond the basic flying around skill level, and am venturing into "sport aerobatics". I too am spoiled to long flights with my T-Rex setup, where I get easy 10 minute flights without stressing the battery. Here's an example of the kind of flying I do:

http://www.justplanechris.com/videos/trex042807.wmv

I don't really want to saddle myself with a poor performer, but then again I don't want to go nuts! :dontknow

-Chris

[Greybird]

Chris, the battery weighs 763 gms. I cannot fly upside down. I guess my flying is scale like only. One 4s 4000 is able to perform aerobatics. Watch the Adam Turner video. Flight time would be 6-7 minutes factoring in higher head speed. Someone calculated his flights at 4 minutes. I truly do not understand the 3D thing. To me, it looks silly.

[JustPlaneChris]

I truly do not understand the 3D thing. To me, it looks silly.I don't really understand it either, Greybird! I do like graceful "warbird style" aerobatics though. But to me the hard 3D looks like the pilot's ankles are being chewed on by a rabid wild animal. Or, as I saw in another post, the heli resembles a gnat with an itchy butt. :lol:

-Chris

[Greybird]

JPC. I am ranting over on RCG about the Trex 600 and it's 5 minute flights. Yesterday, I was at my LHS looking at one. Nice, looks well built, VERY heavy. This thing should weigh 1/2 of what it does. 6S packs that cost 400 dollars are recommended, but it really needs 8-10S packs. I walked out disappointed. For now, my Eco 8, (flys for 20 minutes on 3S 6000 pack or 20 minutes on 4S 4000 pack), my SE(10 minute flights), and my Swift (15minute flights)will do. I will wait for battery prices to come down, and flight times to increase. (Both will happen in the not too distant future) 5 minute flights would do nothing but tick me off on a 1500 dollar heli. I am actually looking at some 350mm blades at Century for the SE. It would allow rotor speed to be decreased, increasing flight times.

[RAV50]

A 2100+ head speed is what one would want for extreme 3D which would also result in rather short flights on 3700mah packs (maybe only 4 1/2 minutes).

For your type of flying I would recommend the 11T pinion that Greybird recommended.

A 1750 head speed will give you more run time of about 5 1/2 minutes of FFF and lower "pop" 3D and even longer for just hover & sport fling training with only rolls and loops.