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Old Jan 27, 2011, 07:14 PM
Hobby Enthusiast
New Mexico
Joined Jan 2011
143 Posts
Finality!!!

Gents,

Today was the best day in my short helicopter life! I finally finished (if finished truly holds) my Brushless CX3 conversion today.

Background:
I received the BCX3 from my girl for xmas. We're both mechanical engineers and love gadgets. So after the battery was charged, I took her for a spin (the heli, not my girl ). Of course, having never flown one before, I crashed into some chairs in the kitchen and broke the blades, lower head, etc... This is where my story turned south.

I went to my LHS and picked up the parts that I needed, got her running again, and decided to fly across the street at the soccer field. Yes, I conveniently have a soccer field 20 ft from my front door. Well, not knowing much about the heli yet, I forgot to re-tighten everything from the previous crash that I hadn't changed out. BAD NEWS. I took her up in the air with plenty of room and the wind caught her, took her 3 houses down and dropped her into the tree (35ft drop). DEAD!!!

...sad...

Then I found FLYRCRIVESUD.COM. "OOOH look how this will fix all my problems", I thought. Bought their combo for $85. After I pulled the stuff from the package, I noticed the outter shaft was well under tolerances for a proper slip fit with the bearing. Next, I noticed the weakness of the inner shaft as compared to stock. Then, I saw the blue delrin gear was not flat or concentric with the outter shaft. I was so frustrated...then I found RCGROUPS! Tons of bad reviews about Flyrc, etc.. (most of you know all this).

So I bought Eflite blue machined parts to replace just about everything (since I demolished this little dude from my crash). Well, after tons of money spent trying various parts, I got a setup that worked well enough. EXCEPT 1 thing, the flybar. I went through 3-4 different flybars and 3 bearing cups, e.g. Xtreme, Boomtown, Stock, Stock-Modified trying to find the best combo. All were crap. Too flimsy or tons of sideways slop, etc. That's when Sven saved the day. He got me a line of the Skytec rotor head and bearing cup. Best investment for the heli IMHO.

Next, while reading I got the brushless craze. I ordered everything and spent the last days working through a ton of configurations/wiring/throttle point settings, etc until today...

Today my heli flew. The 3rd time in a month. The 1st time for a full battery and I even flew it indoors!

Here's my electrical setup:
2 x C-10 motors (Wow hobbies)
2 x Turnigy 10 A Plush (HK)
1 x Mpi (MX 9310) V-tail mixer (LHS)
1 x G110 Eflite Gyro (Fleabay)
Tenergy 900 mAh 25c pack (all-batteries.com)

Mech Setup:
Skytec Upper Rotor Head/Flybar (Best thing you can put on a BCX#) (Sven)
Skytec Upper Bearing Cup (2nd Best thing...) (Sven)
Xtreme Blade Holders (Some website that went out of biz)
Xtreme 55deg Blades (Beautiful compliment to the heli) (Boomtown)
Eflite lower everything (LHS)
Micro Heli Silver Chassis (Amazon)
FLYRCJUNK battery holder/tail boom (works well enough)

After several doses of "Don't smash this to smithereens" & patience, I got her flying. Now, I didn't get it right the first, second, third, ... try, but eventually I did get it right. In the end, the cost to pleasure ratio is irrelevant because you can't factor in the cost-to-benefit ratio of learning. If I had to do this again, I could do it on the cheap. But all my stress disappeared when my girl came home and said, "What is that? Did you buy another heli?" I smiled and told her it was the same one she bought me...well at least the receiver still was. Hahaha.

THANKS FOR ALL THE HELP GENTS!
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Old Jan 27, 2011, 08:35 PM
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United States, WA, Spokane
Joined Oct 2010
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Whoooohooooo! Good ta see you rolling big guy!
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Old Jan 27, 2011, 08:49 PM
Professional heli wrecker
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United States, WA, Spokane
Joined Oct 2010
4,209 Posts
Here is a teaser for my next dual swash vtail in progress. Well, actually my first redone one using new parts. I am waiting on some stuff to finalize the second generation Helo using some of the same stuff you did Tim2go. By the way please post up some pics and progress on your heli on the vtail thread. It is there to help other guys doing the same thing along, now that you have mastered it we want to document the details!




Notice any new things on here Sven??
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Old Jan 27, 2011, 09:35 PM
Hobby Enthusiast
New Mexico
Joined Jan 2011
143 Posts
...the details (V-Tail/Gyro Setup)

Details, details, details:

So I want to expand on my VTail/Gyro setup:

Firstly, I need to state the main problems:
Combo 1:

Turnigy V-Tail Mixer 1:1
HK401 Normal/HH Mode Gyro

All from hobby king

This combo is BAD. The V-tail and 401 do not work together on anything other than a true servo'd tail rotor. The speed controls flip out and the gyro cannot settle. The problem I had is that this heli just spun out of control and I had to grab it before it blew itself apart. I strongly recommend against this combo

Combo 2:

Turnigy V-Tail Mixer 1:1
Eflite G110 Gyro (Fleabay)

This combo worked greatly better than Combo 1. However, without a programmable Tx, the endpoints become a problem. I was able to set the endpoints of the Esc through the mixer but without the gyro hooked up. If I flew it without the gyro, it had loads of power and flew great, except of course it could not keep a bearing.

So after I got the throttle points set without the gyro hooked up, I reconnected the gyro. The heli started fine, but as soon as I went "throttle up", the thing wouldn't even lift off the ground. I spent 3 days playing with the endpoints to no success. Then I found that this combo for some reason does not work without a programmable Tx. This is because once the endpoints are set using 100% throttle on the Tx, the gyro installation causes the endpoints to reduce to around 50% throttle. So with a proper Tx, you can then set your Tx endpoint to 150% to get 100% throttle on the heli.

I know this is confusing but then so was I for days, no weeks, no wait- a whole month!

Combo 3 (Correct Combo For Me):

Mpi V-Tail Mixer 1:1
Eflite G110 Gyro (Fleabay)

This setup works wonders! I can even set the throttle endpoints with all the electronics hooked up. I just turn my gyro gain to 0 on my LP5DSM Tx (stock) while setting. It's so sweet to just plug in the battery and put the throttle at full off, hear my ESC's beep it up, and lift off!!!


For the eye candy:

*Note the massive amounts of BCX# parts I have accumulated in a month. Amazing! I even dedicated a new tool box to her. My HPI savage was happy to have his tool box cleaned of heli parts. Hahaha
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Old Jan 27, 2011, 11:01 PM
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kodak_jack's Avatar
Hilton (Rochester), NY
Joined Mar 2008
9,749 Posts
Quote:
Originally Posted by Tim2Go View Post
Gents,

Today was the best day in my short helicopter life! I finally finished (if finished truly holds) my Brushless CX3 conversion today.

Background:
I received the BCX3 from my girl for xmas. We're both mechanical engineers and love gadgets. So after the battery was charged, I took her for a spin (the heli, not my girl ). Of course, having never flown one before, I crashed into some chairs in the kitchen and broke the blades, lower head, etc... This is where my story turned south.

I went to my LHS and picked up the parts that I needed, got her running again, and decided to fly across the street at the soccer field. Yes, I conveniently have a soccer field 20 ft from my front door. Well, not knowing much about the heli yet, I forgot to re-tighten everything from the previous crash that I hadn't changed out. BAD NEWS. I took her up in the air with plenty of room and the wind caught her, took her 3 houses down and dropped her into the tree (35ft drop). DEAD!!!

...sad...

Then I found FLYRCRIVESUD.COM. "OOOH look how this will fix all my problems", I thought. Bought their combo for $85. After I pulled the stuff from the package, I noticed the outter shaft was well under tolerances for a proper slip fit with the bearing. Next, I noticed the weakness of the inner shaft as compared to stock. Then, I saw the blue delrin gear was not flat or concentric with the outter shaft. I was so frustrated...then I found RCGROUPS! Tons of bad reviews about Flyrc, etc.. (most of you know all this).

So I bought Eflite blue machined parts to replace just about everything (since I demolished this little dude from my crash). Well, after tons of money spent trying various parts, I got a setup that worked well enough. EXCEPT 1 thing, the flybar. I went through 3-4 different flybars and 3 bearing cups, e.g. Xtreme, Boomtown, Stock, Stock-Modified trying to find the best combo. All were crap. Too flimsy or tons of sideways slop, etc. That's when Sven saved the day. He got me a line of the Skytec rotor head and bearing cup. Best investment for the heli IMHO.

Next, while reading I got the brushless craze. I ordered everything and spent the last days working through a ton of configurations/wiring/throttle point settings, etc until today...

Today my heli flew. The 3rd time in a month. The 1st time for a full battery and I even flew it indoors!

Here's my electrical setup:
2 x C-10 motors (Wow hobbies)
2 x Turnigy 10 A Plush (HK)
1 x Mpi (MX 9310) V-tail mixer (LHS)
1 x G110 Eflite Gyro (Fleabay)
Tenergy 900 mAh 25c pack (all-batteries.com)

Mech Setup:
Skytec Upper Rotor Head/Flybar (Best thing you can put on a BCX#) (Sven)
Skytec Upper Bearing Cup (2nd Best thing...) (Sven)
Xtreme Blade Holders (Some website that went out of biz)
Xtreme 55deg Blades (Beautiful compliment to the heli) (Boomtown)
Eflite lower everything (LHS)
Micro Heli Silver Chassis (Amazon)
FLYRCJUNK battery holder/tail boom (works well enough)

After several doses of "Don't smash this to smithereens" & patience, I got her flying. Now, I didn't get it right the first, second, third, ... try, but eventually I did get it right. In the end, the cost to pleasure ratio is irrelevant because you can't factor in the cost-to-benefit ratio of learning. If I had to do this again, I could do it on the cheap. But all my stress disappeared when my girl came home and said, "What is that? Did you buy another heli?" I smiled and told her it was the same one she bought me...well at least the receiver still was. Hahaha.

THANKS FOR ALL THE HELP GENTS!
Since we've given away all of our manufacturing in this country, you and your girl friend are lucky to have found jobs!! Hopefully, they don't count on government contracts. At the point where you just about totaled your heli, I might have bought a used one off Ebay that was already modded and/ or was good enough for parts. It needs pivoting blades and YOU need to keep it under 20 feet if at all possible. The wind just loves to mess with your head and the heli pays for it in the end. I hope you enjoy it, but remember, the goal is not to see how much you can spend on repairs.
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Old Jan 27, 2011, 11:13 PM
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Hilton (Rochester), NY
Joined Mar 2008
9,749 Posts
Tim, you need to replace the servo horns/ arms with the longer ones that have more holes. They help with forward/ outdoor flying.
Xtreme 55 Degree blades?
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Old Jan 27, 2011, 11:38 PM
Hobby Enthusiast
New Mexico
Joined Jan 2011
143 Posts
Quote:
Originally Posted by kodak_jack View Post
...the goal is not to see how much you can spend on repairs.
Of course it's not. But once you're an engineer, a bad flying bird will drive you mad. I don't like bad vibations...

55deg blades are sweet. I've had one successful flight so far. I will report on their effectiveness vs others after I get chance to really tune this bird.

My next phase is to find a suitable canopy. Flying a bunch of wires and metal parts around takes the "heli" feel away.
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Old Jan 27, 2011, 11:54 PM
Suspended Account
Prescott, AZ
Joined Jan 2011
2,380 Posts
Quote:
Originally Posted by Tim2Go View Post
Of course it's not. But once you're an engineer, a bad flying bird will drive you mad. I don't like bad vibations...
Or a real helicopter pilot... ANY bird out of whack bugs the hell out of me, too.
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Old Jan 28, 2011, 12:21 AM
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United States, WA, Spokane
Joined Oct 2010
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LOL, I for one can commiserate with your desire for perfection! Nice job my friend! Nice job.
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Old Jan 28, 2011, 12:20 PM
Hobby Enthusiast
New Mexico
Joined Jan 2011
143 Posts
Gents,

So I am getting TBE that is very slight but sometimes becomes dramatic and causes crazy flying. I have balanced the flybar very well. I have the Skytec upper head so this is easy. Just use two similar height blocks and a fine pin inside the center of the flybar hub. Adjust weights until the thing sits level. However, should I compensate for the link or not? I balance with out it on and then install it post balancing. It is very light and close to the axis of revolutions so the imbalance caused by this would be minimal as compared to the rotating mass of the blades and flybar.

I also need some help with leveling the heli. I hold it by the flybar close to the rotor head. When I look at the heli from the side against a known vertical line (door jam or plug bob), it sits forward a degree or two. I have moved the battery as far back as it will sit inside the battery tray without falling out. I am tempted to add a small piece of steel rod to the inside of the boom to compensate, but adding weight makes me shudder.

Any ideas will help. I need to weigh this thing on my scale to see where I sit anyways.
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Old Jan 28, 2011, 12:32 PM
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Winder Ga
Joined Sep 2008
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You might could move your v-tail mixer back a little on top of your rx. But, you have it set up right now pretty good for FFF. What blades are you using? Lee
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Old Jan 28, 2011, 01:12 PM
Hobby Enthusiast
New Mexico
Joined Jan 2011
143 Posts
I'm using the Xtreme 55 deg blades from Boomtown. They are so good looking, but I think they make the heli way more agile than I want it while flying in a small room. My reaction time is good, but my heli skills are BAD! But my philosophy is that if you can learn on a harder-to-fly machine, you can always fly an easier-to-fly machine.

I just ordered the Skytec extended shafts, with the A/B machined gears, from Sven today. My gears are causing a lot of vibration due to their horrible flatness (or lack thereof).

Once I get those installed, the C.G. from the rotor head will be lower and that should make up a little for the front imbalance. The moment will reduce:

Torque = Force * distance

If the distance to the upper rotor head is increased, while maintaining the same Force (weight up forward), the induced moment (Torque) should drop because the C.G. moment is increased.. This will at least give me a more stable heli.

Also, my heli tends to yaw right (nose right) and the gyro seems to lack the capability to compensate in HH mode. I don't mind too much, but I want to clean this up a little. The trim seems to compensate with a few clicks to the left. However, I believe this is due to the high rotating inertia of the upper rotor. The bottom rotor has quite a bit of rotating mass but it is located near the axis, so the induced moment is less. With the flybar weights, the inertia is greatly increased, which provides the heli with stability, but also puts more drag on the motor.

-Tim
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Old Jan 28, 2011, 02:37 PM
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United States, MA, Malden
Joined Mar 2008
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Tim, I fly the Skytek upper bearing holder but I'm not familiar with the top rotor head in your pics. I see the bottom of the top rotor head is very close to the outside of the bearing holder. It looks like it's not even touching the race of the upper bearing. I can't really see it good but, you mentioned having TBE. Maybe you do have the correct amount of play and it's just the way the heli sits. Just an observation. Nice heli BTW. Great job !!

Mike.
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Old Jan 28, 2011, 05:28 PM
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Since I have ran systems almost identical to yours I have a thought. Kudos on the Skytec parts, I have a complete comparison on the engineering specs the parts provide on the vtail thread. I will not double post here. All tbe issues come back to the flybar assembly itself. The flybar must be so loose it bounces up to 3 or 4 times with the finger tap. The links themselves must be so loose they swing freely under their own weight. The blades you are running were stolen from the thought processes of another posting member here by the way!
Here is an issue with the specifics of the blade profile itself. Again...already done on the vtail forum thread.
The arch of the blade is thinner than an xtreme hardblade for instance, but not much different from the chinese import white blades selling for 1/10th the price without the fancy colors. In mechanical engineering studies done on helicopter blade profiles I will try to keep this simple, not for your sake but for others reading this. In essence if we look at a blade with more arch it not only produces more lift at a lower rpm but it also creates a face against horizontal movement that carries force. A blade that has a full 1/2 curvature (xtreme white/blue) will have that curvature on the end of the blade profile looking at it from the end or side of the heli while in motion. As the spinning of the blade produces lift it also encounters air mass due to its rotational energy while the heli is sliding forward or in any horizontal motion. It will resist this mass in motion much the same way a piece of flat paper does trying to push it through the air against the full flat face of itself. Now take the paper and turn it sideways, it slides through the air. This same process occurs with thinner blade profiles that not only produce less lift but also increase headpeed at the same lift ratio. This is why CP helis always use thinner blade profiles to achieve maneuverability (although the blade profiles and applications are different) the engineering aspects in this vein are the same. What it comes down to in practical applications is that the heli wants to slide from side to side when using this profile since horizontal resistance to motion due to the lack of blade resistance to mass has been reduced. In essence it is much like trying to balance a helicopter on top of a soccer ball. The fatter blades reduce this tendency. I am trying to keep this real simple. Now, on top of this we encounter the issue of the air washing back through the center of the blade grips up along the center shaft when you run out of what the avionics community calls clean air. The thinner blades at the highest point of blade curvature usually peak at this curvature (5/16) roughly 1 3/4 inches from the grip pin hole. The higher curvature blades such as the hardblades hit this index at 1 3/8 of an inch. This effectively reduces the backwash of air that destabilizes the heli from this same effect by as much as 50 to 60%. Now if you follow this line of thought in blade dynamics in relation to fluid air mechanics it quickly becomes apparent that for inside flying on coax helis the fatter curvature blades are inherently more stable in controlled hovering or lifting performance.
But in even more simple terms the thinner profile blades become much more efficient with fresh moving air in horizontal movement. The fatter blades become inefficient in this environment since the design is for greater lift and more resistance to side to side motion. The thinner blades are made to create less resistance to side to side motion but destabilize in a hover. If you couple this tendency along with a slightly stiff or flybar that reacts slowly it will amplify the TBE.
Does this make sense?
Also in HH mode what is your gain set at? Mine is at 80. But the physical gyro settings may be different.
I fly with batteries forward weight bias outside and neutral inside. Holding it by the flybar my weight bias is exactly neutral w/o batts. But the B4 tail assembly weighs more than my modded Xtreme. I had to modify my B4 on the 2nd build to compensate for this, along with centering my modded skids.
Now that you are this far have you tried the HK 401 knockoff gyro?
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Old Jan 28, 2011, 07:10 PM
Hobby Enthusiast
New Mexico
Joined Jan 2011
143 Posts
LMH,

Thanks for overview. My Xtreme blades are definitely harder than anything that I have tried (Stocker, Flyrc). The 55deg angle indicates these should be stable for hover, according to what you were saying, due to their horizontal x-section being larger than the "thin" blades. My curiousity comes into play when I compare these blades, in length, to stockers.

They are significantly wider than stock, but only slightly shorter. I would say visually they have a LARGER x-section in both the overhead view and horizontal view. As far as surface area, definitely larger. To me these should force more downward air and cause higher rotating drag, thus, becoming more resistance to minute movement.

The backwash up the blade grips and shaft is interesting. I would be interested to see the flow profile around there.

Questions:
1) Do the blade grips greatly affect flow characteristics, seeing as they have the lowest linear speed?

2) Having the battery out, for stable indoor flight for my bad heli skills, should the heli sit level-maybe slightly forward?

3) Is there an easy way to get these blades tracking properly. I don't mean by balance, I mean the horizontal track of each blade on their respective rotor head slicing the same line.
I feel that if the one blade tracks slightly higher/lower than its counterpart, the TBE (perturbation) will be induced

Helis are fun! But small helis are significantly more susceptible to imbalance and misalignment issues due to their light construction and the use of plastic. Injection molds, especially Chinese manufactured, are of lower quality and cheap materials. That's why we have these forums anyways! Without manufacturing defects, we would all have A+ helis out of the box!


Second:
They are si
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