Hello I am finishing putting togeathr my new mini titan an I am trying to select the best pinion for my needs. I will be running a 3000kv outrunner on a 4s setup.
I know ho to figure my headspeed but I dont know what headspeed is ideal for my flying. The manual says to use 2600-2800 rpm headspeed. Others seems to be running theirs closer to 3000.
I am no 3d stick banger. I do hovering, fff, agressive fff, some rolls, loops, and learning inverted flying and hovering. How low of a headspeed can I run? I am looking for longer flight times.

Thank You, Noah

Hi noguy,

I would consider going with 2600-2800, or more, as higher head speeds often improve stability. Also be aware that higher cap (heavier) battery packs do not always give longer flight times. This is something that I've learned the hard way with fixed wing electrics. The trick is to find the right balance of head speed, pitch, battery power/cap, and model weight, that best suits your heli and your flying style. Glow powered helicopters sound pretty good right about now huh? Just my .02 worth.

Good luck and good flying!

P.S. Check out "dhrc.rchomepage.com" as this site has a section on this topic, IIRC.

yeah, I agree. Basically you want to figure out what is the ideal running speed and amp draw on your motor so that it is in it's peak efficiency and put that right in the center of where you fly your stick most of the time. You can fine tune it later with pitch adjustments, or pitch curves. Check out this link for a good calc =)
http://dhrc.rchomepage.com/calcAdvan...tem=MRthrust3&

Fmb42, Thanks for the input! Yea I dont know about a glow still though. I ususally dont fly where there is room & I like all of my limbs being attached....lol maybe oneday.

Mrasmm, That link ROCKS! thanks a ton. I am not totally sure I understand how to figure out the peak efficency rpm yet but I am playing around with the calc. cool stuff.

Thank you again. Noah

MRASMM, can I ask you for a little extra help. I have everything input except all of the blade info. I just clicked the trex button and then changed the main rotor and tail rotor diameters to the stock specs of my mini titan. I dont know what all of the rotor parameters should be so left them as the trex specs. (figured it should be close)
As far as the rest of the fields: I have the batt, esc and motor all input correct. I also dont understand what the "tweaked, NoFudge, Vonmises, & Von+" buttons are supposed to represent. The page doesnt give any explanation.

Anyways,
I'm a little confused about how to figure that out??? sorry if I'm being dense here but can you help. Thanks again, Noah

here is what I have: [link]http://dhrc.rchomepage.com/calcAdvanced.htm?kv=3000&voltage=14.8&pinion=10&ge arTeeth=140&drag=.85&MRdia2=711&mAh=2200&AUW=800&p ackV2=14.80&MRdia=711&TRdia=156&MRchord=30&TRchord =15&boomlength=420&TRratio=4.24&The_modtype=1&prof iledrage=0.0035&sliderThrottle=73.45&sliderPitch=3 .88&motortype=369&outKv=3000&outRm=0.023&MaxIo=25& outMotoroz=55&outIo=1.4&esctype=40&Resc=0.0045&Amp =35&metric_escWt=25.5&celltype=0&outCellCap=2200&n umofcells=4¶llel=1&Vcell=3.70&packV=14.80&outCell Res=0.009&outCellWt=&PackWt=239&metric_temper=12.1 5&metric_altit=1&metric_pressure=1013&AirDensity=1 .236909&temper=53.9&altit=3&pressure=29.9&govRPM=2 700&MRrpm=2700&Thr_P5=100&Thr_P4=85&Thr_P3=80&Pit_ P5=100&Pit_P4=75&Pit_P3=50&PitchRangeHigh=12&Pitch RangeLow=0&checkbox_mix=false&checkbox_gov=1&redBu tton=B-Save1&checkbox_bal_thrust=0&checkbox_bal_power=0&L astItem=MRthrust3&]Calculator prototype setup link 1[/link]

I really don't know what those are either, but they really change things up alot.

here is also a simpler version of the calculator, maybe that would help a bit too
http://dhrc.rchomepage.com/calc.htm

I'd be glad to help you figure something out, but I guess I'm not really sure what you are asking. I don't really know that much, but I do know what #'s I am running on my bcpp, so I could plug those in and see how accurate it is and send you back the info. I'll go ahead and do that, it might not be a bad idea to send me a PM reminding me to do it, I've been quite busy and forgetful lately =)

I was basically wondering about what you said about the motor How exactly do I know what the motors ideal running speed is? and amp draw?
Is this info in the kv rating; or is it a value that must be found out in real world monitoring?

If you get time to plug in your blade figures thats cool, but dont go out of your way. I know what its like being busy (self employed here - ie. no life). Lately, I have just been online a lot myself due to being home with some med issues.

here's what I came up with. This is pretty true to form except maybe the main rotor rpm's, but I had to bump the heli weight up. My heli weighs about 320g, but for this thing to read correctly I had to bump it up to 400g as well as change a bunch of other stuff. Honestly I'm not sure that it's real word accurate enough to be useful =(

http://dhrc.rchomepage.com/calcAdvan...m=sliderPitch&

well usually the mfg should supply that info, but basically what you do is have the heli there and figure out how many grams of thrust it provides, and how many amps the just the motor draws and what voltage (watts basically) is drawing, and then you can calculate how much power is going into the motor vs how much lift it is making which equals its efficiency. It's really on the complicated side for hobbyists to be calculating. The mfg's almsot always supply that info for prop motors, but I guess it might be harder to find for heli's.

I'm not really sure which way you would want to do it for the longest flight times possible. High headspeed and low pitch, or high pitch and low headspeed. I guess it would really depend on where the motor is efficient. Usually higher rpm's on the motor with less loading results in better efficiency, so basically run a smaller pinion or less pitch.

on a 4s lipo your motor is gona be spinning around 44,400 rpms, if your main gear has 140 teeth, a 9T pinion will get you right in the 2600 to 2800 range, probably closer to the lower end, where the manual says.

I guess that's all a bunch of BS =P I don't really know what to tell you to get the best running time with the kind of flights you want to be doing, and what kind of headspeed you are going to want to use. I guess get some pinions that are removable, like maybe a set screw or something, and just do some trial and error with a watt meter or a timer or something. Work with it until you get the performance and flight times you are looking for. It sounds like you already have your motor, which is gona be the biggest factor, and then the pitch and the pinions can be adjusted after that =)

Maybe someone more familiar with this heli could help you out some more. The other thing you could do of course is as around and see what kind of flight times people are getting on their setups and what exactly is their setup. That's gona be hard to judge performance though because it is all subjective. I mean you see some guys flying beautifully and they say they are just getting the controls, and then you see other guys that say they have mastered the heli, and then you see a vid of them flying and the heli is all over the place, and ends up going out of control and crashing =P I saw a post like this recently over on another forum, and in the post the guy said that he had mastered the heli to the point where he needed upgrades to go further =P Anyways my point is that some will say that something has good power and handling, while another guy that flies the same thing will say that he can hardley keep it in the air. If everyone had a way to measure thrust somehow, then we could compare actual readings =)

Anyways, after that long post I feel like I've said alot about nothing =P Lemme know if I can help in some way though

in looking for that pinion I came across this,
http://www.trextuning.com/hv.php

that is basically what you want, except for your heli instead of the Trex

mrasmm,

Yeah I think I am comming to the same conclusion about the info I find online. Not reality. However, trextuning seems to have some real great info.
Most people seems to be reporting real short flight times with the stock mini titan setup. 5-6min. The best I have heard from someone doing hovering and mild FF is 8-9min (not too bad).
I decided on 4s since I really would like to break into the 10+ min range. Aside from recent weeks (medical issues) I dont get a lot of time to go fly and when I do I just want to fly and fly and fly.
Also I realized I was figureing everything on a 140t main....whoops MT has a 150t main. So that brings things down a bit but I still would like a 9t to experiment with. I dont think I want to run this heli in the 3000rpm range. For one it doesnt suit my flying style and for two its all plastic setup may not like it. I have already heard reports of tracking issues when really pushing this bird. (supposedly AL mixing arms are the fix)

Based on all of my internet probing I finally decided to get an eagle tree (& rpm sensor). I ordered it with my 4s packs so hopefully all of my goodies will be here soon. I was also trying to think of a way to measure lift/thrust. As you were saying that would be some very informative data. If I come up with a practical Idea on how to do it I'll be sure to post about it.
I am not used to flying a heli that has balistic capabilities so I was really hoping to start out with the 9t and work my way up if I feel comfortable with the power. If I cant get one I think I'll follow your advice and just limit my max pitch to start. I know headspeed creates stability so maybe I'm just being a scardy cat????

Thanks again mrasmm! if there is ever anything I can do for ya just pm me. I really appriciate all of your help. (my lhs's stink)

Noah

hehe, yeah, you're welcome =) one of my lhs's is ok but fairly opinionated for the amount they know, but the other one never knows anything.

I do have one question about float chargers. I'm gona post it over in the battery section, so if you know something about that, wonder on over there and see if you know what I need =)

about the headspeed, as long as your past the crashing stange, and it sounds like you are, the higher headspeed isn't really a problem. Just take it slow and get used to it, and stand far enough away from it so that no matter what happens it's not gona hit you =) probably about 15' or so. You could also mess with your throttle curve and run it a bit slower for a while, and just check the motor temps because brushless over heat more easily under lower rpms.

good save on the 150t main gear =)

I fly pretty well for about a year of off and on flying. imo.. I am very comfy with ff & various turns, my orientation (right side up) is pretty solid. I can do loops & rolls no prob. fly/hover a little invert.
I dont know why Im so nervious about my HS. I am almost done with my setup and am hoping for first hover this weekend. Maybe its all of the vids I see online where the heli just takes off like a rocket and goes waaaayyy faster than what I am used to flying.

I think maybe I just need to grow a pair.

> dont understand what the "tweaked, NoFudge, Vonmises, & Von+" buttons are supposed to represent.
Thanks, I've added a little info to the page today. The prototype isn't finished and there are four different simplified static math models, some of which are more accurate in some situations for some values but not all. As you can imagine, modelling rotor dynamics of everyone's heli is an almost impossible task but with some experience you can draw some useful conclusions from the estimates although sadly limited.


Just a few mm on the blade chord can make a noticeable RPM change.
Longer flight times are gained with lower head speeds by reducing the 200 to 300mph tip speed drag, then gearing the motor for it's peak efficiency range, normally ~80% of full throttle.

Mini Titan 10T calculator estimate (Tweaked static modelling), change the main rotor's Blade profile drag from 0.0035 (for micro's) to 0.005 or 0.01 (for mini's) and the numbers might be even closer... who knows the actual profile drag of a MTitan blade anyway?
Edit: increased blade chord from 30mm to 33mm
Mini Titan 10T calculator estimate revised with Von+ static modelling which seems closer to reality for ~700mm rotor mini class belt tail electrics.



By swapping across 9T,10T and 11T, and hitting the hover button estimates that in this case, each extra tooth adds around 1 Amp to hover current and looses 1 min flight time of hovering from a 2100mAh 4s pack. Of course there are a lot of variable and data not accounted for, even a slightly over tight belt will trash all the best estimates in the world.
Running a low head speed will impact the heli's handling, slowing your flip and roll rates. How low is to low for your flying? I don't know. 10T looks to give the 2600-2800 rpm recommended. Try the 9T for an extra min or two in the air at ~2400rpm (depending on throttle curve and pack voltage in the flight) but the slower roll rate may be too slow for you at the end of a pack. I'd be surprised if you can get 15mins on such a belt setup but you never know. Have a play .

DarkHorse, [sm=spinnyeyes.gif] You are awsome! My PC is filled with crude looking unformatted excell spred sheets for heli, 2-stroke motor tuning, $ budgets, and whatever else that needs some math in there. Your calculator is simple and beautifully written. Thank You for your time and effort that we all get to take advantage of!!!!!!!!! In fact I just dropped you a $5 donation through paypal link on calc. As for now I cannot speak for the accuracy of the figures but when my eagle tree arrives I'll do some Mtitan comparisions.
I will definatly post all of my 4s finding once I have my 1st pack. I started ouit with one of those cheepo hextronixs packs @ first for experimenting.

Thanks Again DH.....You and your calculator rule!

Noah

Hey thanks man, much appreciated .

> when my eagle tree arrives I'll do some Mtitan comparisions.
That data would be useful, I'll try to add some preset buttons for MTitan setups soon .

Also, I've collected links to other calcs, spread sheets and resources at the bottom of the page that may be more useful under certain circumstances. Though real life measured in flight data is best.

No Problem, it the least I could do. I would buy you a new car but I still cant find that money tree my daughter is certian that I have here somewhere.