B Trimble

Hello all,new here and kinda new to heli's. Been toying w/a Fun Piccolo for a few months,managed to modify w/a little inginuity,but as I have been searching for a better,more equipped machine I cant help but wonder if fly bar placement has much to do with performance?For instance,I just ordered a Belt CP,and couldn't help but notice that the Belt has the flybar above the blades,as the Fun has it "even" w/the blades and most nitros are below.Whats the reasoning? Just curious. By the way,this forum has been very helpfull with my purchase of the Belt and I hope to learn a lot more from you folks. Keep up the good work and keep those birds in the air!

kenhiraihnl

first of all, welcome to this forum...i've flown helis with top-mounted, under-slung, and flybarless...there's always a tradeoff between stability, durability, ease of maintenance, performance, etc. (like the difference between a belt-driven tail rotor versus a gear/torque-tube tail rotor)...i think you'll be a better pilot because of your interest in the mechanics...here's something i grabbed from another forum, which explains some of the differences pretty well (technical though)...ken

The main purpose of the flybar is stability. Whether it has paddles or not, the flybar acts as a rate damper for the pitch and roll axes. Most full size helis have more than two blades for tip speed reasons. It would be difficult to have flybars for anything but a 2 blade head. I think the Cheyenne had a 4 blade head with Bell mixing.

Bell Mixing:

The flybar without paddles is Bell mixing (Huey, Bell 47, etc.). Like Doug said, It requires a physical damping of the flybar teetering. Without any damping the flybar would want to stay in its own plane of rotation. With Bell mixing the blade pitch is a composite of both swashplate input and flybar teeter input. Bell mixing does for cyclic what a rate gyro does for your tail. It works as a rate damper. Cyclic is a little sluggish because the flybar is working against the cyclic input.

Hiller Mixing:

With Hiller mixing the flybar has paddles (Hiller Raven). With Hiller mixing there is no physical damping of the flybar. It is free to teeter just like on our models. The damping in the Hiller system is aerodynamic damping from the paddles. With Hiller mixing, the blade cyclic pitch comes from the flybar teeter only, not the swashplate. With paddles you get the gyroscopic stability of the flybar without having to work against the stability when giving a cyclic input. This makes cyclic more responsive than the Bell system but you still have to wait for the flybar to tip before cyclic is fed into the blades. With paddles you essentially move or vector the center of the gain so that it's not working against the cyclic input. This is a little like before HH gyros when gyro gain was p-mixed to rudder to drop the gain when rudder input was given.

Bell/Hiller Mixing:

Bell/Hiller mixing is what most of our models use. Like the name implies Bell/Hiller mixing is the combination of the two. You get both the flybar/paddle input from Hiller mixing plus the cyclic pitch from the swashplate. This is the fastest responding of the three mixing methods because cyclic is instantly fed to the blades unlike Hiller mixing and your not working against the flybar's stability unlike Bell mixing.

An interesting side effect of paddles is trim in forward flight. The natural tendancy of the rotor is to pitch up in forward flight because of precession. Because of the inflow through the rotor, the paddles lift down so precession causes the flybar to pitch down. With any luck the forward cyclic the pitched down flybar feeds to the blades will exactly cancel the pitch up tendancy of the rotor. When this happens you have a machine that flies like it's on rails.

Chris

flyinsolo11

Awesome fine, kenhiraihnl- however it doesn't really answer his question. What does the placement of the flybar affect?

Seriously, that as a real good find- I have been trying to find somehting that goes into a little more detail about the flybar and its designs. I hope you don't think I am bashing you- just trying to point out that the question still remains.

Thanks for sharing!

kenhiraihnl

aha! you're right! but b. trimble said he was 'just curious'...so i did a quick and dirty search and hoped his curiosity would be satisfied...lol...

btw, take a look at this link (and the 'walkaround pics' at the bottom)...great pics of various kinds of rotorheads that should generate a lot of curiosity...lol...ken

http://oh1ninja.la.coocan.jp/details...ell214ST_e.htm

blk822

I read somewhere that a flybar under the main blades is more stable, but don't know why. I have moded my HBK2 with a head from a copterx 450( which is a clone of the TRex 450) and the fly bar is on the bottom. But the thing that realy helped me get to hover , was that the flybar should have almost no resistance. It should be able to flop up and down by blowing on it lightly. So I couldn't control my HBK2 befor trying to hover and a guy I met said my links were to tight and I needed to size them and make them alittle loose. So I did and now I can hover and do some forward flight and reverse flight. So I know the flybar needs to be very free in its motion. But as for the top or bottom ,I don't really know. But I can hover full packs now and am having a great time. I juts wish the weather was better.

kenhiraihnl

hey blk822...you're exactly right...most guys worry about how tight the blades should be in the grips...hardly anyone asks about how tight or loose the feather bearings/spindles should be...when they're floppy loose, like you described, you can hover like a hummingbird...if they're too tight, you'll be chasing the bird all over the place...lol...btw, i don't know anything about high or low flybars either...ken

B Trimble

Nice Ken,very informative,I guess there is really no "bad" design then. I ordered a Belt CP from HeliHobby a day ago,and have the jitters already. Like I mentioned,the Fun Piccolo was my first and only heli till now,and that damn thing was shelved for a year. It was like trying to fly a cinder block! A few months ago my interest was re-ignited so I blew the dust off the little turd,did a little research,and low and behold I can hover it.Mind you it cost me two bare bones kits and some parts off a cheap Hover Lite,but hey,with a little persistance and inginuity.........Anyhow heres a pic. Check out the 5.5mm knitting needle boom,the HoverLite blades and skids and the homemade head stiffener!LOL. Believe it or not,it flys!

xodarap1

Hello B Trimble and a warm RCU welcome to you. I'm originally from Palmerton, Pa. Spent my younger years in Clearwater, FL and most of my non service years were spent in northern NY right on the Canadian border.

As for flybars, performance wise, the flybar does the exact same job whether it is above the blades or below it as it rotates around the same axis. I guess personal preference is most of the issue unless you fly inverted cutting grass lol.

The only snag I've run into was when I was test fitting my custom case design. A 450 over slung flybar (when the blades are in the holder hits the top of my dual case and makes fitting the king2 in there with it impossible. With the under slung flybar, I can get both heli's in there along with the tx, batteries, tools etc so everything is all in one case. Guess it wouldn't be a big deal to have two $60 cases if I drove to the field, but I only spent $20 for my butt ugly elcheapo one and I walk to the field most days. My flying field is large but it's all 2' to 3' tall grass.. so it's 36"x36" helipad in one hand and the dual heli case in the other.

kenhiraihnl

hi b. trimble...it's very satisfying when one can mod a heli like you did, and make it fly...with your ingenuity and stick-to-it-tiveness, you have the potential to go far in this hobby...ken

B Trimble

xodarap1,thanx for the post. Hey I hear ya. You shoulda seen the field I flew my first(and only) trainer plane at. Looked like a jungle but I managed 3 good landings before a trip to the LHS.

Ken,thanx for the props,but I've learned alot of what I know from fellow flyers like yourself. You cant rely on the industry to make your learning experience a joyfull one,maybe a costly one,but you learn from hands on and fellow flyers who arent afraid to expand their abilities and ingenuity.

kenhiraihnl

b. trimble...happy to pass-on what little knowledge is left in my head...btw, i was thinking about the over versus underslung flybar...the high flybar is normally flying in clean air -- except during autorotation and inverted flight, where air flows through the rotor system from the other direction...any rotor blade/paddle will be more efficient in clean air...however, it's more complicated and costly to get the linkages to an upper flybar system...the opposite applies to an underslung flybar...ok -- that's my take on it -- until someone talks me out of it...ken

B Trimble

Makes sense,can't imagine why the Belt is so reasonably priced. Seems to have it all.Brushless power,belt driven tail,top mounted fly bar,Li-po,decent size/weight,seperate electrics,etc,etc,etc....... And to think,I almost ended up with an Axe cp! WHEW!

B Trimble

Well fellas,my Belt arrived today,WOW! What a machine. The complexity of the mechanics is mind boggling to say the least. I can't wait to give her a go,but first I want to perform all the recommended checks,loose screws and so on.So far so good.I have two questions though(kinda stupid ones but never the less).1.Should the tail blades be loose in their grips?I'm assuming yes,being as they have to self center, 2.What is the sticky sided velcro for?(Battery). Remember,the closest thing I have that even resembles a heli is the Fun Piccolo,so go easy!
thanks in advance

zachmccool

Ok, I have had the Belt cp for just over 2 weeks now and am loving it. I have had to rebuild the head once (b/c of my first crash) and have had to adjust the main blades many times. The tail blades should be loose as they spin they will straighten (just like the main blades). I never did figure out what the stick velcro was for. If you crash and rebuild the head like I did be sure the double check the tracking of the blades and the pitch of the main blades and flybar if these are off by just a little the bird will not fly as stable as it dose right out of the box.

B Trimble

Just received my Belt today.Awsome is all I can say,based on appearance any way.After all the pre flight lingo and the battery charged I decided to give her a go. The thing wanted to go (aileron) to the right.Adjusted the trim all the way left and to no avail.After closer inspection,even after checking everything,the right(passenger side of a car,in US any way)servo horn was way off 90 degree at center stick. Removed horn leveled swash,replaced horn,and here the servo does not respond to any input,even plugged into a diff. channel and nothing.You think its just a lemon servo? Anyone have this problem before? Do you think HeliHobby will stand behind their product and replace it? Or should I eat it and up grade?
Thanks


Glad to here you like it,I kinda figured they should be loose,common sense told me so,never hurts to ask.But unfortunately I have issues with this bird now,and I wasnt even able to crash it yet. Oh well,soon I will get the opertunity to stuff it into the dirt!
Happy flying

ArrowNaughtic

Answered in your other thread you started..... stick with that one and you will get more results.


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