What is considered super light for a 385 bladed heli

[Heli Mod Man]

Hey Guys,

I hang out in the electric heli forum. I am not a 3D pilot. However, I make manufacture my own exotic helis. I am basically a very agressive non-3D pilot.

I am building a new heli right now and I am pushing to make it as light as possible. All my helis run 385s. I have had one heli down at 1189 grams AUW. This new heli will be under 1000 grams. It looks like it should fall right at 980 grams if I have my calculations correct (most parts are machined already).

At any rate, I will be running an Orbit 10-18 on 6S in this heli. It should be capable of serious power.

My helis are roughly comparable to the Eolo or Spirit Pro in size.

So, what is considered light for a 385 bladed 3D heli?

Matt

Oh, for those of you who have never seen my helis, here are a few pics of my 1189 gram heli.

[Heli Mod Man]

Anyone?

I am curious to know how much weight is considered light for a 3D heli swinging 385s.

Matt

[Kai_Shiden]

Hehe Matt,

I think you've hit an interesting conundrum, there are very few mass production 3D helis in the 385mm blade range, and none of them are considered lightweight by any stretch of the imagination.

I think the Robbe Eolo/Spirit Pro, and MScomposit Stinger 6/Ikarus Viper90 are the only 3D helis that I know of that specifically run 385mm blades. I believe that the spec flying weight for the Stinger 6 is 1000 to 1150gr AUW (but the Stinger/Viper series is known to not have a very rigid airframe).

You could PM buzzsaw 46 to find out what his Eolo weighs (he's quite weight conscious of his 3D helis), but I believe that the Eolo's are typically in the >1300gr range.

Nearby in that size range would be the Quick EP8 series, which runs 400mm blades, those typically come in between 1400 to 1600gr from the examples I've seen online.

-Kai

P.S. If the parameters are expanded to 425mm bladed helis all of the Lepton size helis come into play, but I have yet to see one of them come in under 1600gr.

[aaronredbaron]

Why not plot it out? You should be able to get some good figures for 450, 500, and 600 sized helis, and then if you plot out the weights and blade sizes, you should be able to see a trend showing you where you need to be for models with any given blade size. This may not work so well if you want to extrapolate the info, ie this may not work as well for trying to figure out what a bigger heli should weigh. but for this case were there are accepted figures for models larger and smaller, I think its within reason. You could also plot out the blade speeds to get an idea.

[Heli Mod Man]

Thanks Guys.

This heli could swing 420s. But, I have found the mainshaft flex (resonation) along with the weight of those blades can cause resonant shaking. But, 385s are perfect. I am stretching the blade grips to give about an inch of extra rotor diameter (I have done this before) without adding blade weight. That will also reduce the effective disc loading even further.

Kia,

I spoke with Dave the other day. I may want to talk to you on the phone about this sometime. :)

Matt

[Heli Mod Man]

Oh, I have the airframe built and weighed. The frame, nose cage, landing skids, tail boom, tail case with fin, and boom brace weigh in at 168 grams.

Here are some pic of the heli so far. As mentioned, it weighs in at 168 grams is it sits. I have done ALOT to get the weight down. There are at least 10 grams I can remove from the center keel with some judicious Dremel crafting along with a few other grams I can take off here and there.

Wait till you guys see the rest of the heli. ;)

Matt

[Kai_Shiden]

Thanks Guys.

This heli could swing 420s. But, I have found the mainshaft flex (resonation) along with the weight of those blades can cause resonant shaking. But, 385s are perfect. I am stretching the blade grips to give about an inch of extra rotor diameter (I have done this before) without adding blade weight. That will also reduce the effective disc loading even further.

Kia,

I spoke with Dave the other day. I may want to talk to you on the phone about this sometime. :)

MattI bet that by stretching the grips, it adds some damping that tames away the resonation because of your modular grip design.

Funny you mention disc loading, I ran some numbers for disc loading comparisons of different size helis a while back trying to figure out a good ratio to use for scaleing (ie, a corrective factor to run against rotor diameter vs disc loading vs headspeed), here are the disc loading numbers I've revised recently:

"Stock" MiniZoom 6.5oz/ft² (340mm rotor dia, 180gr, 4000rpm)
"Stock" BCP 4.8oz/ft² (527mm rotor dia, 325gr, 2000rpm)
My Maxir SE 3s 3.7oz/ft² (620mm rotor dia, 340gr, 2600rpm on 3s910)
My Maxir SE 4s 4.0oz/ft² (620mm rotor dia, 362gr, 3100rpm on 4s800)
"Stock" Trex SE 5.9oz/ft² (700mm rotor dia, 690gr, 3000rpm)
"Stock" Stinger6 5.9oz/ft² (900mm rotor dia, 1150gr, 2300rpm
"Estimated" Bzerker Extreme ;) 4.8oz/ft² (925mm rotor dia, 980gr, ????rpm :D)
"Stock" Lepton EX 7.3oz/ft² (955mm rotor dia, 1600gr, 2600rpm)
My Sniper 5.8oz/ft² (1060mm rotor dia, 1560gr, 2200rpm)
"Stock" Trex600 6.9oz/ft² (1350mm rotor dia, 3000gr, 2100rpm)

What the raw numbers don't show us is that different size helis can't be compared for hang time feel in the air by disc loading alone. RPM and size percentage work into how a 3D heli feels in the air (ie a heli can be made to "feel" lighter by cranking up the headspeed, but at the same time just going larger by itself doesn't require as much headspeed or as low of disc loading to feel much lighter in the air).

I used to run my Maxir SE on 4s, but realized that I was only handicapping my collective management learning by running such an overpowered setup, so I recently went back to 3s and in doing so dropped the disc loading and headspeed, but honestly it feels lighter in the air (and the less power allows me to hear the headspeed fluctuations better which is really helping me work on my power management).

IMHO Trex 450's are overweight for their size (partially because they run 3s 2100 to 2200). A Trex450 is only 3" larger rotor diameter than my Maxir and yet weighs 2x as much. I firmly believe that a heli could be made in the same size as a Trex450 and weight more like 550gr running 4s1320 (that's roughly watt/h equivalent to 3s1800), and make excellent power without having to sacrifice frame rigidity/durability.

Also IMHO, I think many of us electric heli flyers are losing touch with our roots, we're going to rediculously high C rated packs and draining them rediculously fast on overweight helis spinning hellaciously high headspeeds. The very low disc loading of my Maxir allows me to have great 3D authority at reasonable headspeeds for a micro heli and have excellent duration (I spin 2600rpm, have 1 roll per second cyclic, and can 3D for 8 minutes on a 3s910, or 12 minutes on a 3s1320).

-Kai

P.S. Looks to me that your new proto will be in an extremely nice low disc loading weight range (for scaleing factor, my Maxir at 620mm, 3.7oz/ft² feels much like my Sniper at 1060mm, 5.8oz/ft²). I would think that with around 2300 to 2600, it should have great to excellent punch and response.

P.P.S. All the above "stock" numbers are the manufacturer's rated AUW, all the real examples of those helis that I have touched weighed significantly more (but since I didn't build them, I didn't want to make them comparitively look worse because of lack of wire shortening or component choices).

[Heli Mod Man]

Thanks for the info.

I will be running an Orbit 10-18 on 6S 1340 Flight Power cells geared 8 to 1. The pack weight will be 140 grams. Head speed could be up as high as 2700 RPM if I feel the urge. Odds are I will run it at 2400 to 2500.

Did you calculate my disc loading based on the 1 inch over diameter (stretched grips)? I want the disc loading as low as it can possibly get.

I have run this setup on another heli at 2700 RPM (without stretched grips) wayyyy up at 1550 grams with HUGE performance. I had better than 1 second roll rate with extemely stable hover characteristics. This thing should be stupid responsive.

What I am trying to accomplish with this heli is acceptable flight time (maybe 8 to 9 minutes at high head speed or 10 to 12 minutes at moderate head speed) with no chance of over loading the disc. I am a very aggressive pilot. I am not a 3D pilot by any means. But, I like to fly very hard. I also LOVE flying in high winds and fast in tight spaces. I am sick of overloading the disc or requiring huge head speed to get decent performance.

So, again, are your numbers taking into account the stretched grips?

Matt

[Kai_Shiden]

Cool power setup, that will keep the costs of running it way down (especially if you achieve the flight durations you mentioned).

In a way, yes I did "sort of" take the additional inch into account ;). But, I don't know the exact rotor diameter (ie 385x2 + blade bolt to blade bolt distance), so I based the 925mm rotor diameter on the Stinger6/Viper90, adding on 25mm (I cheated and just rounded up).

I forgot to mention in my previous post, that ultra light disc loadings do have their downside, air drag in lateral moves becomes a dominant factor and lateral "throwing" manuevers can lose velocity if we aren't driving the momentum with additional pitch.

The following is for those who are casually reading this thread and to put my own opinions into perspective.

The upsides to low disc loading are:
Increased runtime and battery cycle life (of course, if too small of battery packs are used, then the batteries could be pushed to higher C ratings to save weight, if they aren't up to the task these benefits go away)
Lower load on the power system (pitch loads are more transient, ie the heli moves where the controls point it faster and head unloads quickly)
Lower load on the head components and drivetrain (takes less energy for the cyclic to rotate the mass of the heli, yaw also benefits but this depends upon mass distribution)
Less impact momentum in crashes (this may or may not lead to lower crash damage depending upon where the structural sacrifices were made)
More hangtime in autos
Faster response in maneuvers


The upsides to higher disc loadings are:
Increased momentum (dampens out wind gusts and is easier to stay smooth in general because it resists changes to momentum vectors more)
Slower descent speed in autos (downside is that maintaining the perfect pitch is much more difficult as disc loading goes up, there is an upper limit to a heli's weight before it cannot auto, this is dictated by the drag of the blades, ie. you can only store so much energy in the rotor disc before the advancing blade hits a terminal "glide" velocity and the retreating blade cannot overcome the advancing blade's drag) -> wow that was long
Increased component strength (the additional material must be distributed properly or the randomness of crash damage simply increases though, unless so much material is added that flight characteristics severely suffer there is no such thing as a fully indestructable 3D heli)
Increased resistance to vibration (of course, if you have to turn up headspeed to carry the extra weight the way you want, then you have a different potential level of vibration to fight)


As far as I'm aware, the only single way to improve 3D flight on a heavy disc loaded heli is to increase headspeed, BUT, for every 10% increase in headspeed 21% more energy is required to maintain that headspeed (drag increases at the square of velocity, this is a hard rule of subsonic aerodynamics).

-Kai

[ifoguy]

Kai:

That was a very informative exposition. Thanks for taking the time to write it up.

[Heli Mod Man]

Kai,

I was looking at a Neu 1902. I could save a few grams and increase efficiency. However, I already have my 10-18 in another heli. What are your thoughts? Also, I chose the Flight Power 1340 cells because of their super high power desity. They are very light for there capacity. I looked at TP Lite packs as well. However, the Flight Powers were still far higher density.

Oh, I am also going to run a 6mm wide belt rather than my normal 9mm belts (motor belt). That will shave a few grams and increase power system efficiency. 6mm is still plenty wide enough to handle this setup.

Any other thoughts on it?

Matt

[Swash McHover]

Kai:

That was a very informative exposition. Thanks for taking the time to write it up.

Ditto

Thanks

[DarkHorse]

I've included oz/ft² to this calculator (http://dhrc.rchomepage.com/calc.htm), to more easily calc disk loading in imperial units, for the old school numbers gang ;).

I'd be intersted in these FP 6x1340s. Have anyone got a link please?

[Heli Mod Man]

They are not available in 6S unfortunately. I will be running two 3S packs in series.

Actually it looks like I may have a bit of power reserve with these cells. However, they do not make a slightly smaller pack (maybe 1200) in there Lite series.

I do not have the numbers in front of me, but when I chose those cells, I calculated the MAH of a bunch of cells and their weight to get an accurate number of available energy versus weight. The FP 1340 Lite cells have a huge advantage over any other cells I have found even compared to TP Prolites.

I do not have my cells yet. But, I will definately let you know my impression of them.

I have run ALOT of lithium cells over the years. I am tough to impress. :)

Matt

[buzzsaw 46]

My ears are ringing did some one mention my name, LOL.

My Eolo is at 1344g RTF right now. Aveox 27/26/2 with heat sink, 3x S3150's, S9254, CSM Sl720, P-80, 770 RX, U-BEC, 5s FP 2500s, and probably 90% of the alloy options available. Yes I'm a sucker for shiny bits:D

I'm planning some changes but I'm not sure if they will reduce or increase my AUW yet, it wont be much either way reguardless.

Matt, this Bzerker is going to be nuts if you can hit your 980g target. Cant wait to hear more about it!

[Heli Mod Man]

Hey Buzzsaw! Man, I remember one of my early threads, "Who has actually trimmed a tree ON PURPOSE with their heli?" And you chimed in merely saying that is why you are called Buzzsaw. :D How's it going?

The B-Zerk should be fantastic when it is finished. However, I did get a couple calculations wrong. I was weighing the 6S FP EVO 700 high C cells and applying that weight to the 1345 Lite cells. What that means is, the heli will be good for no more than 7 minute (probably 6 minutes) flights in the 700 cells or will fly over 10 minutes on the 1345s but gain 60 grams. So, I will probably pick up both packs, one for normal flying and one for pushing the limits. Hmm, my flying is not the greatest earobatically, but I can push the heli pretty hard as long as most of the flying is sharp side up.

Anyway, I also figured out a few ways to take off some more weight from the airframe. One major thing is the elimination of the front cyclic servo mounts (if you look at my early B-Zerk and Freestyle). The front cyclic servos will now be mounted by way of small extension tabs coming off the nose cage near the mainshaft. That will drop 10 grams off the heli, make it alot easier to service, move weight up and forward (needed to run a much lighter pack) and make it look alot more integrated. I am now looking for ways to eliminate more parts. Making one part do the work of two is always a good way to save weight.

At any rate, my early B-Zerk weighed 1189 grams with a 270 gram pack. The new pack will weigh 140 grams. That brings the weight down to about 1070 grams without making any other changes. The single boom support takes off 16 grams, the lighter nose cage and skids take off 10 grams, the new servo positioning takes off 10 grams, etc, etc, etc. I haven't even begun shortening wires yet. So, my 980 gram weight projection should be accurate. I am beginning to wonder if I can even push the heli hard enough to see the 700 watts the power system is capable of due to the lowe weight. It was easy to pull 700+ watts from m y 1550 gram Freestyle.

At any rate, I hope the flight time is above 5 minutes. I can live with 4 to 5 minutes of hard flying and 6 to 7 minute of casual flying. Otherwise I will definately go to the 1345s.

Matt

[Kai_Shiden]

Hehe, the weight you listed is why DarkHorse's ears perked up ;) (I couldn't find a webpage with a listed weight spec for the FP evolite 1345 packs though so I didn't contradict it).

A friend of mine has suggested I try the FP evolite 1345 packs in my Maxir because they weigh almost identical to prolites, but hold voltage under load better (rated to 18/28C compared to 13/20C, personally I never count on much more than the continuous rating as I find most manufacturer's burst rating tapers off voltage extremely fast).

I'm pretty sure you won't see 700W out of 6s 700mah, by the time that it's getting near that draw either the heli has already moved and unloaded the rotor some, or the headspeed drop would be very severe (the exception to the unloading is high angle large diameter funnels and hurricanes, those keep the rotor loaded up continuously).

As an example, I went from TP1320 to TP910 on my Maxir, both are continuous rated past what my Maxir requests of them for peaks (13A). While TP1320's are manufacturer rated for 17A continous, and TP910's are rated for 15.5A continous, there is a significant difference in voltage holding under high steady state loads. In high angle funnels and other continous loadup moves the power doesn't rebound back up near as fast with TP910's as it does with TP1320's. I have to be absolutely perfect on collective to pull off more than 5 consecutive rolls on 910s, where I can stationary roll indefinetly on 1320s (I can go continously with 910s if I add a half second pause at inverted and upright, pointing to the voltage not rebounding back up as fast).

-Kai

[DarkHorse]

Ahhh you read me too well :D LOL

OK I'll come clean, I got a very cheap deal blinged Stinger6 (AUW 1000g 860mm CF, mini Eco8 like) + Axi + Spin66, working through the configurations and future mods. What an awkward heli it is...

I could bore you with the numbers and the specifics but don't want to pollute this thread ;).

[Heli Mod Man]

Sounds cool! Feel free to post specs on my thread. :)

Kai,

I agree totally. I have had alot of experience over loading lipo packs with my top speed car. I was pulling 3600 watts off my 12S TP 2070 pack in that car. I could pull it down to 27 volts for 1/2 second when I hit the throttle hard.

My guess is that my Eagle Tree may log one quick spike when the collective is smacked, but I doubt it would sustain more than 500 watts continuous (a couple seconds or more). Heck, my 1550 gram Freestyle could barely cope with 700 watts. This thing will probably be so fast in transitions that it won't pull much wattage off the pack.

I may go to 1345 cells for general flying. Those packs are 100 grams for 3S. So, 200 grams total. The 700s are 140 grams for 6S. The added 60 grams will be nothing to worry about in casual flying. But, I do want to get the 700s to see how light I can make this thing. :D

Matt

[Heli Mod Man]

Oh, I just came back from the shop with a nice shiney newly machined TR belt pulley (mainshaft pulley for the TR belt). It is a 40 tooth MXL aluminum pulley. I got it machined down to 5 grams! And it still seems plenty strong. That is cool because I was able to pull 6 grams off the main pulley (120 tooth 2mm pulley). So, now both pulleys are lighter than the one pulley started! COOL!

I will post pics as I machine more parts and continue the build.

Matt

[buzzsaw 46]

Nice work Matt!! Attack every last bit;)

I was thinking at work tonight, what do you guys think the minimum servo torque would be for this size heli? I cant help but wonder if some of the smaller 12-14g servos could cope with the loads. The Kopropo PDS3014 has 28oz/in of torque for a 12g servo thats pretty good it would save about 18g just on the head servos. I'm also running one on the tail of my SJM-500 with a 2100t gyro, that would save another ~28g over the 401/9650 combo.

Just putting some thoughts out there;)

BTW the SJM-500 also runs 385mm blades AUW lightly loaded is ~1550g.

[Heli Mod Man]

Hm, not a bad idea! I may have to look into them. For my flying, those servos may be fine. But, I am not sure about true hard 3D. Of course I may never be to that point in my flying anyway. :D

Oh, I am also shortening the mainshaft 1/4 inch. That will pull of some weight and raise the CG a bit. Every little bit helps!

Man, I am finding so many ways to lighten this thing. But, I am running into the law of diminishing returns. There is only so much weight that can be removed without weakening the heli. I want to make sure I get creative and not sacrificial when I lighten it.

Kai,

Any thoughts on those servos?

Matt

[Kai_Shiden]

I think 28oz/in is marginal, but probably workable with medium to short servo arm positions or hiller ratio dominant head mixing. I run HS81MG's on my 470mm bladed 1560gr Sniper and they only have 36oz/in, I don't think that is going to be enough torque when I go flybarless, but I also don't know of any tried and true method for calculating required servo torque.

I tend to try to go overkill on cyclic servo torque, the tail on most helis loads up the BEC enough without worrying about the cyclic servos stalling (when I go flybarless I plan on using S9650's on my Sniper).

-Kai

[Heli Mod Man]

Cool.

There are also the HS65MGs. They are listed as 26 ounces at 4.8 volts and 30 ounces at 6 volts. I do not know how accurate they are, though. Also, yes, my head is hiller dominant (long mixing arms similar to the Logo 10 3D layout.

So, that leads into my next question; Would me Berg reciever and 401 gyro be OK on 6 volts? I have a CC adjustable 10 amp BEC. So, I can tailor my voltage to my liking in .1 volt intervals.

Do you think HS65s would be decent? They are alot less expensive than the KO servos.

Matt

[Kai_Shiden]

In all honesty, I have to bow out when it comes to making recommendations as to what servos would be adequate. As I mentioned, I have no way to calculate the required torque.

From my perspective I will never recommend anything to someone else that I consider borderline. Whether it be servos, batteries, ESC's, etc., the end result of any of those parts not being up to the task is a failure potential that IMHO outweighs the benefits (I've had a cyclic servo die in flight and total an Eco8, the only parts that were usable after were the RX, motor and gyro).

That doesn't mean that I won't try out items that I consider to be borderline, but I do so fully accepting the potential risks to my own aircraft. If someone else decides that they want to use the same "borderline" components as I have used, I try to make clear that the item stood up to my usage but may not stand up to someone elses. In the case of ESC's, power management alone can make one being run outside it's limits survive.

For example, on my Sniper after spending time practicing based upon watching videos of my own piloting with eagletree gauges overlaid, I went from >900W peaks down to 700W peaks while doing the same "visual" flying and having far less headspeed drop. I could still purposely slam the sticks around and generate the original >900W peaks, but found there was no benefit to the visual "pop" of the flight.

-Kai

[Heli Mod Man]

Fair enough. I totally understand. :)

I do appreciate your input.

I shortened the titanium mainshaft a bit today and machined the bearing blocks. I will be making the servo mounts soon (as soon as I decide what servos I will use).

This is getting fun! Oh, I will be running an aftermarket canopy designed for the T-Rex 450. It weighs in at 18 grams.

Anyway, I will keep pushing to see how far I can take the weight down on every part I can.

I think I will try the HS65s. My LHS has them in stock. Also it will be very easy to make simple mounting plates for them and change them back if I decide to move back to 81s. Running the 65s will save me over 30 grams total versus the 4 servos I was previously running.

Oh, I may be able to run 420s on this thing too. But, that will not be right away. I think it will be insane with the stretched head swinging 385s. ;)

Again, thanks for the input. I appreciate it.

Matt

[buzzsaw 46]

I hope they work out ok Matt. I would feel guilty if they end up causing an injury, I have thought of trying smaller servos myself but haven't had the chance yet.

The HS65's are the most recomended for T-rex size helis so they should be pretty good. But as Kai says could be marginal torque wise. I was hopeing someone would know how to calculate needed torque. I guess at this point if you go outside the norm you are on your own. That said, I know HS81's have been used on Logo10's(marginaly for 3D) so they are probably more suited to hard flying on 385-420 bladed helis.

Just be careful Matt, I dont want anyone getting hurt over a 30g weight reduction. maybe try the 81's first so you know how it should feel then move to the 65's, that way you'll know if they feel too soft.

[Heli Mod Man]

That is not a bad idea.

The servo arrangement is such that I can move from one to the other very easily. Also, the load on the servos should be light considering the high Hiller rate I am running. Heck, 65s are cheap enough that it is worth a try. Do you know of the 401 gyro and my Berg reciever will take 6 volts well? If so, that alone would give me plenty of torqe.

Also, I have run 81s on my 1550 gram Freestyle at 2700 RPM hs without any problem at all. The light weight alone will reduce the load on the servos.

Then again, I may be sorry I blew a hundred bucks on something that didn't work. :)

Should be worth a try, though.

I will try most anything once! ;)

Matt

[wazzer]

Subscribed

Very Intersting Thread

[buzzsaw 46]

RX and gyro are fine with 6v.

I wasn't sure if the lighter weight would reduce the required torque, but I kind thought it might.

[Heli Mod Man]

Excellent.

Yes, light weight reduces servo torque required. Lighter weight blades help reduce servo stress as well.

I will probably lighten the flybar paddles too. That will reduce servo load a touch also. That way I can reduce servo travel for the same roll rate. My head design is inherantly very stable because of the wafer dampening and a neutral Delta 3 layout. So, I think lighter paddles with less servo throw (shortening servo horns to gain a bit of torque) should yeild very good cyclic response without sacrificing hover stability------theoretically. :)

So, Buzzsaw, where is Spring Valley? I will be in Dassle (near Hutchinson) over Christmas. Maybe I could bring the heli and we could hook up. Even if it is too cold to fly, we could hang out.

Matt

[Heli Mod Man]

Oops, double post.

[Heli Mod Man]

I have a bunch of machining and assembly done today.

I have the pulleys done and installed. The mainshaft is 7mm diameter (6mm at the top) grade 5 titanium. The shaft weighs 24 grams.

The heli as it sits weighs 272 grams.

Here is the build thread I am running in the E-Heli forum;

http://www.rcgroups.com/forums/showthread.php?t=773454

I am giving more pics there. I decided to go without thrust bearings to save weight. So I CNC machined 1/8 inch thick Delrin washers. We will see how well they survive. :)

Anyway, for those who are not faimilar with my stuff, I am sure this looks unorthodox. But, this heli design is pretty well proven. I am just altering everything to save as much weight and maximize performance as far as I possibly can.

Matt

[buzzsaw 46]

Matt, Spring Valley is about 30 min south of Rochester, or about 1.5-1.75hours south of Minneapolis.

It would be cool to hook up and check out your handy work. We'll have to try and make plans for a meal or something. How long are you going to be in Hutch.?

[Heli Mod Man]

We normally go up to visit my wife's family through Christmas. Our anniversary is the 26th too. So we make it a long extended weekend normally.

I will let you know when I have a better handle on when we are arriving and returning.

Matt

[Heli Mod Man]

I am seriously considering going to a Neu 1902/4Y on 8S for this thing. That would put it over 1000 grams. But, the available power would go way up. 6S on my Orbit 10-18 would be enough I think. But, the Neu on 8S would be stupid powerful. It would also run alot more efficient and give far longer flight time.

I would need a new ESC, different pack, the Neu motor, and a HV BEC (I already have that). So, I am looking at $500 for required componentry to do this. But, I have some stuff for sale right now. If it sells, I will go with the 8S/1902 setup. If not, I will stick with the Orbit 10-18/6S setup.

Any thoughts?

Matt

[Kai_Shiden]

If you do go 8s, you could shave some weight by running the new PHX-HV30 (1oz, up to 50V): http://www.castlecreations.com/products/phoenix_hv_series.html

-Kai

[Heli Mod Man]

Yup, that is my plan. ;)

I am planning on running it in on 4S Flight Power 2170 cells through a 1902/2Y that I have here (nice having parts laying around). It should fly wonderfully with that setup. But, ultimately, I want to go to 8S.

Matt

[Heli Mod Man]

I got the servos and motor mounted.

It is coming along!

Matt

[DarkHorse]

Looks like an agressive insect :cool:.



MS Stinger6 data:
Rotor: 860mm CF (40mm chord, 42.5g each)
4s2500mAh Evo25 (63A continuous, 268g, 130x39x28mm)
Motor: Axi 2820/8 1500Kv (151g)
ESC: Spin66 (~65g)
15T pinion (on equivilant 120T main gear ratio)
3x HS-82MG (19g each)
HS-50 on tail (seems fine, very free)
Gyro: MS-044 (13g)
Rx: Schules Alpha (9g?)

Estimate max 35A 14v ~500w punchout, ~12mins cruising.
@ ~2500rpm (405kmph/250mph tips), ~6.2oz/ft² disk load in hover
Good CofG with 268g pack slop front mounted,
ESC mounted below the frame, rx and gyro top boom area.
AUW = 1100g

4s Stinger6 Calculator estimates (http://dhrc.rchomepage.com/calcAdvanced.htm?kv=1500&voltage=14.8&pinion=15&gearTeeth=120&drag=.90&MRdia2=860&mAh=2500&AUW=1100&packV2=14.80&MRdia=860&TRdia=160&MRchord=40&TRchord=22&MRblades=2&TRblades=2&boomlength=500&TRratio=4&The_modtype=1&profiledrage=0.0035&sliderThrottle=82.32&sliderPitch=2.78&motortype=0&outKv=1500&outRm=0.026&MaxIo=42&outMotoroz=151.1&outIo=3.3&esctype=42&Resc=0.0012&Amp=60&metric_escWt=56.7&celltype=124&outCellCap=2500&numofcells=4&parallel=1&Vcell=3.70&packV=14.80&outCellRes=0.0065&outCellWt=71.2&PackWt=284.8&metric_temper=12.15&metric_altit=1&metric_pressure=1013&AirDensity=1.236909&temper=53.9&altit=3&pressure=29.9&govRPM=2000&MRrpm=2453&Thr_P5=100&Thr_P4=85&Thr_P3=80&Pit_P5=100&Pit_P4=75&Pit_P3=50&PitchRangeHigh=12&PitchRangeLow=0&checkbox_mix=true&checkbox_gov=0&redButton=B-Restore2&checkbox_bal_thrust=0&checkbox_bal_power=0&LastItem=MRthrust3&)

I've added a bit of frame reinforcement to reduce resonance that can occur near the end of spool down with ali solid head damping. If this heli holds up I think it should be even more attractive if stretched to take longer blades. An Eco8 boom can be cut down, if anyone knows about the Stinger6/Viper90 belt (s3m 1119mm by ~4mm with a 480mm boom) and where to get a longer one with the correct tooth pitch then please post or PM me. ;)

[Heli Mod Man]

SDP/SI carries nearly every belt pitch you could want. I would check there first. :)

Those are good specs. Do you have any pictures of the setup without the canopy?

Oh, this heli can run 420s. I have run them on roughly similar layouts in the past. But, I found no benefit over the 385s. It just gained weight. That is why I am running CF 385s with stretched lade grips for a larger rotor diameter.

Anyway, I only have few more parts to make. Then I can begin final assembly. The big issue right now is tooling. I am short a couple tools to complete the machining. So, those will be ordered this week.

Matt

[Heli Mod Man]

[QUOTE=DarkHorse]Looks like an agressive insect :cool:.



[QUOTE]

The Praying Mantis was one of my design inspirations. :)

Maty

[DarkHorse]

Thanks for the SDP/SI (http://www.sdp-si.com/Cd/default.htm) tip. Once I figure out tooth pitch requirements I should be in luck.

Looking forward to seeing your heli come together and take flight :cool:. Interested to see the grip extensions.


Given the relative fragility of the S6 design, I'm thinking that it would have been better to use lighter components for an 860mm 900g heli than a 1100g with larger rotor... :rolleyes: we'll see.

Here's some pics of the S6 taken before I fitted HS82MG servo and had to more the ESC for inside the frame to the outside. Demonstrates the slope battery frame mod. For extra frame rigidity in the roll direction I might fit double CF frame laminate layers (pretty light weight anyway). So far all power peaks and duration times are still only estimates (bad weather, dark).

[Heli Mod Man]

Looks good!

The grip extensions are easy for my head design. I use aluminum hubs for the grip with CF wafers that grab the blades. The look is similar to the Lipoly. All blade dampening is done with the CF wafers. I will merely make longer CF wafers. That, of course, will affect dampening. But, I will work it out.

Kai has flown one of my heli's (a heli I built with this design). It works well, at least for my sloppy, though agressive, flying. :D

Matt

[DarkHorse]

Just a quick update: My 1100g 860mm 4s 2500mAh Stinger6 setup (as above) is way more greedy that I expected.
10A spooled up around 2300rpm at zero pitch.
14A spooled up around 2700rpm at zero pitch.
~9.5mins mostly at lower 2300rpm, hovering out a pack (still breaking in).
Although the Spin66 measurements are not that accurate is did measure a peak of 37.3A at 14.13v (527w) somewhere but I can't remember any memorable punchouts :confused:.

EDIT: Got some pretty reasonable performance.
12º punchout from hover Spin66 logged 44.3A x 13.88v = 615w

AUW 1100g (hover disk loading 1.89kg/m², 6.21oz/ft²)
Small 160mm tail rotor is holding so far.

Hows the project coming on?

[Heli Mod Man]

I am out of town for the Hollidays.

I have the servos mounted and the motor. It is coming along. I am not rushing it, though. I am making sure to cover all my bases. :)

I will post more pics in a week or so.

Matt

[Heli Mod Man]

Here are pics from another thread.

http://www.rcgroups.com/forums/showthread.php?t=773454&page=3

Matt