HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Oct 31, 2010, 05:55 PM
Professional heli wrecker
Luvmyhelis's Avatar
United States, WA, Spokane
Joined Oct 2010
4,012 Posts
Discussion
Brushless Coaxial Heli builds Using Vtail mixers

OK, after some serious prompting from more than a few members here I have decided to post up a new thread concerning brushless setups for Coax helis that are not using stock factory electronics using gyro setups or mixers. The reason for this is that the factory setups have limitations that limit and sometimes even hinder the flight charictoristics that most people are looking for in Coax technology. Not only will this thread address eliminating or supplimenting the factory controller as we understand them, but the other inherant weaknesses that all coax helis face in their origional design features. This will cover every mod that will enhance the coax design, from skid assemblies all the way through aftermarket platforms, motors, shafts, gears, and head assembles including blade mods. We will even address canopy features and how to fit and modify existing and aftermarket canopies and lighting systems. Even down to painting them. The only prerequisite is that it is understood from the get go that we are not talking about any brushed motor upgrade, nor are we addressing how to fix or modify existing electronic controls beyond the addition of external ESC"s and Gryros in application of brushless motors.
What this means is that we do not want to talk about existing fixes for stock problems being discussed on the two other complete threads in this forum.
There is no limitation in size, or brand preferance. There is already talk of building a 450 size variable pitch coax here on this forum using existing parts available from any and every soarce, but doing it for roughly a third of the price of the two kits that are currently being sold. We may already be looking at two differant versions of this thought process that may hopefully evolve into affordable versions that the common hobbyist can build without bankrupting themselves.
At the start of this thread my goal is to produce a reasonably priced flyable CX3/2 coax heli platform using readily available parts, a vtail mixer, and brushless motors. If you are building a Lama this is ok also. Since looks are subjective, any and everything can be changed to suit whatever look the builder has in mind that suits their personal agenda.
Since all of my 5 coax"s have evolved through multiple builds, and wrecks, I am aware that with all the bits, parts, and pieces available we can make these look a hundred differant ways. I have 3 current coax's that are each going to recieve a brushless upgrade. Each will be based on a much differant body style. For this first build since I fly this outside and my younger son wanted the shiny terminator look here we go.
I have basically already prepped 2 differant versions, one is using the Microheli CX2 Carbonfibre platform. The other is using the stock plastic platform in the intrest of saving some money and seeing if the skid upgrade would work on it. I paid $26.00 for mine on an Ebay auction, but I have noticed everyone is raising their prices on these and now it seems everywhere I look they are closer to $30.00. They either come in the silver finish, which is what I bought, and the Blue anodized look.
http://cgi.ebay.com/MICROHELI-CX001B...item5adbf26d3d
There are multiple vendors of these and I just chose this one to show the concept. The only benefit outside of the extra bling when you use these is the fact that it eliminates virtually all the vibrations that affect coax's as a whole. Keep in mind that this one upgrade will add some weight to the heli! In fact every aluminum upgrade will cost you in this department. The other thing I sprung for on all my helis was also a microheli swash listed on the same auction site for $9.99. We all know that stock swashes tend to wear out and separate at quite possibly the worst time, not only that they are renowned for how sloppy they are. The other swash available is one made by eflite. However since it is a press fit with no internal bearings and cost more than twice as much I passed this choice by. Although I would like to note here that it is a much tighter swash and has much more precise blade control than the Micro swash.
I already have quite a few spare Rcrivid and boomtown skid and battery trays that are tough and somewhat indistructable. But due to the small landing skid surface on them they proved to be hard to land and fly on thick shag carpets and outside in grass. Since I have a contact in china working for a company called OK-fly that sells heli parts I discovered some titanium skids being produced for a 450 size heli that are tough as nails and unbelievably light. And with some deft bargaining I picked these up for a mere $3.60 and they showed up within a week.
http://cgi.ebay.com/Durable-Metal-La...item3cabbc7865
I have also seen quite a few superskid upgrades that I like and more than one person has upgraded to Trex 250 skids. Both these mods bolt on to the stock battery cradle. My only problem with this thought is that it is quite easy to break the stock trays! They might look tough but under stress will always find the weakest link. So in both cases I started with the indestructable battery trays being produced by RVcrivid and also being sold through Boomtown.
http://cgi.ebay.com/MANUFACTURE-efli...item439dbcda04
http://cgi.ebay.com/UPGRADE-eflite-B...item45f166ac70
The black one will go on my stock bodied CX2, The white one is on the Microheli carbonfibre platform. The reason I chose white is because my son likes the clear canopy look on the Xtreme body kit that I chose to use, it also shows off the brushless motors this way, especially at night with the lighting system. Well over a year ago I experimented with this body kit in a quest to raise my battery power from 900ma to the 1200 ma battery. The battery tray on this kit worked for this by just cutting out the battery tabs and sliding in the battery! Here is the kit, and I will include a pic of the basic skid with 1250ma battery installed with stock motors.
http://www.boomtownhobbies.com/Xtrem...ks_p/xc001.htm

With the vastly reduced weight of brushless motors this extra weight was hardly noticed and I had well over 20min brisk flight times!
Again, if you shop around this can be purchased for cheaper in auctions if you are in no particular hurry.
Almost any canopy design will now work as the Vtail coax mixer eliminates all of the controller electronic bulk that the coax helis have had to have. If you stick with the 3in1 and buy for instance the WowHobbies brushless upgrade kit, you now have to fit the new controller/Esc package alongside your 3in1 and receiver and it looks like this. But this kit cost me a whopping $89.99 plus shipping.
The only way this fits is to have an aftermarket canopy of some kind. Here is where a 250 trex style would work well. None of the stock style canopies will fit. And I have half a dozen of them. The Xtreme was over an inch longer and allowed some room for the components to fit. Most guys paint theirs. What I am going to do now is eliminate the 3in1, Use a Coax v-tail mixer instead, and put in a set of turnigy Esc's with 2 of their brushless motors for half the cost of the Wowhobbies kit. If you are using an LP5DSM Tx or any other Tx than the Spektrum DX6i this system shown above will work just fine. However, if you are using the DX6i, no matter how many ways that I tried to program it and after 3 new 3in1s I just could not get any performance out of this mod due to the interfacing problems common with this upgrade. And after repeated attempts dealing with Wow I decided to just replace the 3in1 and used a CX2 4in1 that I grafted in but was not real happy with the performance. Especially the gyro. The danger the system has with the LP5DSM is more range oriented than anything. It flew wonderfully! But when I was outside doing performance flying it suddenly lost contact about 80ft in the air, over concrete of coarse, and I ended up replacing almost everything!
Just so you know, at this time I did extensive research on upgrading the TX and using different receivers. But at this time I am keeping the DX6i and doing the build this way. I have many pics and info to follow. If any of you have ideas along the way, please post up! This is just one guy doing a build with the thoughts he has today. Many of you know of a host of variables that may improve this process for me and others to follow!
Luvmyhelis is offline Find More Posts by Luvmyhelis
Last edited by Luvmyhelis; Dec 28, 2010 at 04:25 PM. Reason: spelling change
Reply With Quote
Sign up now
to remove ads between posts
Old Oct 31, 2010, 08:29 PM
Professional heli wrecker
Luvmyhelis's Avatar
United States, WA, Spokane
Joined Oct 2010
4,012 Posts
The very first piece that I started with, and what the entire heli body is built around is believe it or not, the battery tray. I picked a black one to go on the black plastic bodied Cx2 that I am using a blue eflite canopy on. This particular tray not only has a flexible section that pushes on the battery to hold it in, but the material is stronger and it makes a large differance in the rigidity of the plastic body. I chose a white one on my Microheli CF platform because my son likes the Xtreme body look and clear canopy, but it makes no differance in how strong the structure is on this one. I use this body primarily for outside hard sport flying and regularly take it up a hundred yards or more. So due to this I wanted brighter colors and more exaggerated parts to help with orientation. Keeping in mind that no matter how well or fast this can fly, and I have had it up to 30 or 40 mph, that it will never rival even the cheapest Vp heli on its worst day. I will never argue that it even comes close to my highly modded B400. (Only one part of it is stock). The plastic Cx is mainly used in the house and for some outside flying also, but one of my friends and my son fly it so it is designed to be very balanced and stable. Hopefully I get this right, I spent an hour and a half just to have the whole post dissappear earlier. LOL.
The motors came from Hobbyking, along with the ESc"s.
http://www.hobbyking.com/hobbyking/s...idproduct=6584
http://www.hobbyking.com/hobbyking/s...idproduct=4318
and also the coax vtail mixer can be purchased here that replaces the 3in1 along with whatever gyro that you prefer.
My understanding is that this GWS mixer is the cheapest one that works well, however the one I am using is from dionysus design and cost about 3 times as much. http://www.dionysusdesign.com/produc...roducts_id/185
http://www.hobbyking.com/hobbyking/s...idproduct=4170
When looking at the total sum of these parts it is still far less than the $89.99 plus shipping wowhobbies charged me for my 1st brushless build. Roughly $41.00 compared to 90.00. But we have yet to buy a decent gyro. I purchased an Eflite 110 which is the same one used on a stock B400 from Tony (Barrack1001) for dirt cheap so in this build it is not a large contributing econonmic issue. Many thanks for the good deal here Tony! However earlier I was planning on using a KDS900 avcs gyro due to how tiny it is when I pulled it off of my B400 build and went with a stock Flymentor setup for now. It acually may not work as the 1520uh speed it operates at may be incompatable. The other option is a Hobbyking knockoff gyro that is really cheap, functions well but has a hefty weight penalty. http://www.hobbyking.com/hobbyking/s...dProduct=10113
But, this puts me in the roughly $50.00 catagory for a complete brushless upgrade using a superior gyro, I loose substantial weight, and double my flight times while having more power that I can possibly use! I am currently waiting on a package carrying clear shrink wrap and other various bits for my wiring harness to show up so I can shorten all the wiring, solder it up, and position everything in a presentable package. Especially considering the clear canopy that may be on here for a while. So for now I am putting together 2 differant bodies and here are the pics,

I am waiting for a Boomtown B4 tail assembly to complete this one.
Luvmyhelis is offline Find More Posts by Luvmyhelis
Last edited by Luvmyhelis; Nov 01, 2010 at 01:03 AM.
Reply With Quote
Old Oct 31, 2010, 09:30 PM
It flies!!! ... so who cares ?
erdnuckel2's Avatar
Joined Mar 2009
8,625 Posts
Quote:
Originally Posted by Luvmyhelis View Post
...
My understanding is that this GWS mixer is the cheapest one that works well, however the one I am using is from dionysus design and cost about 3 times as much.
...
Well, that is exactly the point, the DD mixer costs about 3times as much as the GWS V-tail mixer, because it is a mixer specifically designed for coaxials, which the GWS mixer is not ...

Edit:
Also, can you get a little more specific on the weights, like for example how much does your landing skid weigh there ??
erdnuckel2 is offline Find More Posts by erdnuckel2
RCG Plus Member
Latest blog entry: 2014
Reply With Quote
Old Oct 31, 2010, 09:57 PM
Professional heli wrecker
Luvmyhelis's Avatar
United States, WA, Spokane
Joined Oct 2010
4,012 Posts
Just scroll through the pics and read the descriptions.
So the question remains, what do you guys think so far? What would you change?
Luvmyhelis is offline Find More Posts by Luvmyhelis
Reply With Quote
Old Oct 31, 2010, 10:03 PM
Professional heli wrecker
Luvmyhelis's Avatar
United States, WA, Spokane
Joined Oct 2010
4,012 Posts
Quote:
Originally Posted by erdnuckel2 View Post
Well, that is exactly the point, the DD mixer costs about 3times as much as the GWS V-tail mixer, because it is a mixer specifically designed for coaxials, which the GWS mixer is not ...

Edit:
Also, can you get a little more specific on the weights, like for example how much does your landing skid weigh there ??
I have ordered a (cheap chinese) digital scale to do just that. This is a good point on the mixer! and I am glad that you pointed it out. However earlier I was lead to believe it would work. I would be glad to know if this was not correct. There was also a discussion of the turnigy mixer which is priced under $3.00 but did not allow for complete mixing.
One thing for sure, the titanium skid set is much lighter than the Xtreme battery tray and skid set when compared side by side. Compared to stock however it is going to add weight for sure. I will know more when I can scale this out.
The skids scaled out at 27 grams on a digital scale.
Luvmyhelis is offline Find More Posts by Luvmyhelis
Last edited by Luvmyhelis; Dec 28, 2010 at 04:31 PM. Reason: additional information
Reply With Quote
Old Oct 31, 2010, 10:16 PM
It flies!!! ... so who cares ?
erdnuckel2's Avatar
Joined Mar 2009
8,625 Posts
Quote:
Originally Posted by Luvmyhelis View Post
I have ordered a digital scale to do just that. This is a good point on the mixer! and I am glad that you pointed it out. However earlier I was lead to believe it would work. I would be glad to know if this was not correct. There was also a discussion of the turnigy mixer which is priced under $3.00 but did not allow for complete mixing.
One thing for sure, the titanium skid set is much lighter than the Xtreme battery tray and skid set when compared side by side. Compared to stock however it is going to add weight for sure. I will know more when I can scale this out.
The DD mixer is a piece of work (you can find a lot about that topic in the BigLama thread) but the guys at DD have always been rather pleasant to deal with for anyone I know who got into this situation ... (and they were pretty good at correcting things if there was a problem - kinda BECAUSE of them ...
Anyway, the GWS mixer was used a lot in the early conversions here on RCG (but Tony is surely more competent to tell you something about this than I am, as he was among the first on here to do a LamaV4 conversion that I read about ... I would say easily more than two years ago)
As far as the turnigy mixer for 2.95$ is concerned, a few guys on a forum in Germany tried to figure that one out ... turns out there are only specific gyros that the Turnigy one will work with without a problem ... unfortunately I don't remember from the top of my head which ones those were ... but I do remember they were expensive

Bottom line: if you do a COAX conversion to brushless/boardless, the DD mixers seems to be the better idea compared to the V-tail mixers, if I interpret right what I have been reading over the years ...
erdnuckel2 is offline Find More Posts by erdnuckel2
RCG Plus Member
Latest blog entry: 2014
Reply With Quote
Old Oct 31, 2010, 10:40 PM
Resident Skeptican
Barak1001's Avatar
USA, AL, Hanceville
Joined May 2008
4,323 Posts
Vtail mixers are fine as long as they are a 1:1 mix. It doesn't matter if the mixer is designed to work with a coaxial or not. A pipe wrench isn't designed to be used as a hammer, but I've definitely used one as such on more than one occasion.

If we were to go by labels none of these coaxials are designed to be brushless, so we shouldn't put brushless motors in them right?

As far as the Turnigy mixer, it's what I used in my Lama V4. It worked fine once you work around the 0.5:1 mix. I never had any issues with it initializing with my gyro, but my gyro was one of the expensive ones (Telebee GR201). In the long run I was glad I spent $2.95 on the mixer and $50 on the gyro, rather than spending $25 on the mixer and $20 on the gyro. Of course they didn't have $14 clone 401 gyros around back when I did my chopper.

The only minimal advantage that a DD mixer has is the adjustment screw. If you've got a programmable transmitter you don't need that screw. All it does is adjust your yaw rate. On the other hand you can do like I did with my V4, learn to fly it with the fast yaw rate.
Barak1001 is offline Find More Posts by Barak1001
Reply With Quote
Old Oct 31, 2010, 11:04 PM
Professional heli wrecker
Luvmyhelis's Avatar
United States, WA, Spokane
Joined Oct 2010
4,012 Posts
Quote:
Originally Posted by Barak1001 View Post
Vtail mixers are fine as long as they are a 1:1 mix. It doesn't matter if the mixer is designed to work with a coaxial or not. A pipe wrench isn't designed to be used as a hammer, but I've definitely used one as such on more than one occasion.

If we were to go by labels none of these coaxials are designed to be brushless, so we shouldn't put brushless motors in them right?

As far as the Turnigy mixer, it's what I used in my Lama V4. It worked fine once you work around the 0.5:1 mix. I never had any issues with it initializing with my gyro, but my gyro was one of the expensive ones (Telebee GR201). In the long run I was glad I spent $2.95 on the mixer and $50 on the gyro, rather than spending $25 on the mixer and $20 on the gyro. Of course they didn't have $14 clone 401 gyros around back when I did my chopper.

The only minimal advantage that a DD mixer has is the adjustment screw. If you've got a programmable transmitter you don't need that screw. All it does is adjust your yaw rate. On the other hand you can do like I did with my V4, learn to fly it with the fast yaw rate.
LOL, that is brutal. Definitely not a boring way to fly a coax. Maybe that is why you like your 450 build so much you adrenaline junkie! So let me get this right, by me spending $25 on the mixer and cheaping out on the gyro I bought from you I am doing this back asswords.
I am still going to try it and if it does not work I am using my KDS900 which is a $120.00 gyro, but my fear is that this is overkill.
***The avcs gyros will not work in a coax when using the avcs function***
none of the mms gyros seemed to initialize correctly using this system either after some serious attempts. Simple piezo gyros seem to work best.
Luvmyhelis is offline Find More Posts by Luvmyhelis
Last edited by Luvmyhelis; Dec 28, 2010 at 04:35 PM. Reason: additional info
Reply With Quote
Old Oct 31, 2010, 11:13 PM
Professional heli wrecker
Luvmyhelis's Avatar
United States, WA, Spokane
Joined Oct 2010
4,012 Posts
P.S. I hate the fact that this program cut all the descriptions off. Bummer.
By the way Tony, thanks for the call this am! This new 450 coax build we were talking about has got me pretty excited! I spent a pretty much sleepless night thinking about the shaft internals and gearing. I also noticed on the Helibaby that the upper head is operated off the top when you look at the vid's closely. That is how he solved the linkage issue, but I am not quite sure how he is doing it. But it does explain why the outer shaft is so large if he is running in essance 3 shafts in one tube.
Luvmyhelis is offline Find More Posts by Luvmyhelis
Reply With Quote
Old Oct 31, 2010, 11:16 PM
It flies!!! ... so who cares ?
erdnuckel2's Avatar
Joined Mar 2009
8,625 Posts
Quote:
Originally Posted by Luvmyhelis View Post
LOL, that is brutal. Definitely not a boring way to fly a coax. Maybe that is why you like your 450 build so much you adrenaline junkie! So let me get this right, by me spending $25 on the mixer and cheaping out on the gyro I bought from you I am doing this back asswords.
I am still going to try it and if it does not work I am using my KDS900 which is a $120.00 gyro, but my fear is that this is overkill.
Not to be taken too seriously ...

... THIS ... would be overkill ...
http://www.rchelimag.com/pages/scope...cope=17&page=2

... or this ... maybe ...
http://www.futaba-rc.com/radioaccys/futm0807.html

good night ...


PS:
Did the same type of tail as on your microheli CX2 a long time ago (sometime around feb or march i's say) on the green machine (or was that even last year ... man, time really flies - and the faster the older I get )
- just I took a 5mm carbon tube (that fits fine as well)
erdnuckel2 is offline Find More Posts by erdnuckel2
RCG Plus Member
Last edited by erdnuckel2; Oct 31, 2010 at 11:23 PM.
Reply With Quote
Old Oct 31, 2010, 11:24 PM
Professional heli wrecker
Luvmyhelis's Avatar
United States, WA, Spokane
Joined Oct 2010
4,012 Posts
The 520 is very close to the size of my KDS900. But my Kds does the same thing as the spartan as far as function. Not quite sure that a coax of this size can actually utilize the tech for these 3 servos. LOL
This is a link to the gyro kit I bought about 6 months ago.
http://cgi.ebay.com/KDS-900-kds900-H...item3cb1777d2a I have since stripped the servo in a crash. Obviously this servo is not quite up to par when looking at the quark you posted. That gyro alone probably costs more than this whole build.
Luvmyhelis is offline Find More Posts by Luvmyhelis
Last edited by Luvmyhelis; Nov 01, 2010 at 12:15 AM.
Reply With Quote
Old Nov 01, 2010, 12:19 AM
Professional heli wrecker
Luvmyhelis's Avatar
United States, WA, Spokane
Joined Oct 2010
4,012 Posts
Quote:
Originally Posted by erdnuckel2 View Post
Not to be taken too seriously ...

... THIS ... would be overkill ...
http://www.rchelimag.com/pages/scope...cope=17&page=2

... or this ... maybe ...
http://www.futaba-rc.com/radioaccys/futm0807.html

good night ...


PS:
Did the same type of tail as on your microheli CX2 a long time ago (sometime around feb or march i's say) on the green machine (or was that even last year ... man, time really flies - and the faster the older I get )
- just I took a 5mm carbon tube (that fits fine as well)
I like it! My only beef with the outer tube method is that even with the tape provided or even C.A. glue it tended to tear loose under small wrecks. And I used to wreck alot! I actually was looking at a titanium superskid mod using the 5mm tube at one point.
http://www.super-skids.com/superboom.htm
I like what you did with the colors! Very cool. The canopy is perfect!
Luvmyhelis is offline Find More Posts by Luvmyhelis
Last edited by Luvmyhelis; Nov 01, 2010 at 12:48 AM.
Reply With Quote
Old Nov 01, 2010, 12:25 AM
I am the 53%
Bullitt3309's Avatar
San Antonio TX
Joined Mar 2008
184 Posts
Good writeup! I have aquired the parts to convert my CX2 and Walkera LAMA 400D to brushless. Looking at going to seperates with a 2801 reciever for the Walkera, so your thread will guide me along. Will you show the wiring schematics as well for the CX conversion?
Bullitt3309 is offline Find More Posts by Bullitt3309
Reply With Quote
Old Nov 01, 2010, 12:53 AM
Professional heli wrecker
Luvmyhelis's Avatar
United States, WA, Spokane
Joined Oct 2010
4,012 Posts
Quote:
Originally Posted by Bullitt3309 View Post
Good writeup! I have aquired the parts to convert my CX2 and Walkera LAMA 400D to brushless. Looking at going to seperates with a 2801 reciever for the Walkera, so your thread will guide me along. Will you show the wiring schematics as well for the CX conversion?
Yes, this was covered at one point quite a while back in the Lama thread. So really what is happening here is nothing new. But what we do have is alot more experience and options. Here is the wiring.
Also while you are at it will you post up your Walkera pics along the way?
Luvmyhelis is offline Find More Posts by Luvmyhelis
Reply With Quote
Old Nov 01, 2010, 06:57 AM
It flies!!! ... so who cares ?
erdnuckel2's Avatar
Joined Mar 2009
8,625 Posts
Quote:
Originally Posted by Luvmyhelis View Post
I like it! My only beef with the outer tube method is that even with the tape provided or even C.A. glue it tended to tear loose under small wrecks. And I used to wreck alot! I actually was looking at a titanium superskid mod using the 5mm tube at one point.
http://www.super-skids.com/superboom.htm
I like what you did with the colors! Very cool. The canopy is perfect!
The Canopy is a custom made - unfortunately not by me ... I only provided the [design] idea, but I am not enough of an artist to carry out my idea(s).
So anyone who is interested in canopies like that one, here is the place to go:

www.djkhobby.com

erdnuckel2 is offline Find More Posts by erdnuckel2
RCG Plus Member
Latest blog entry: 2014
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion VTail mixers and gyros Uttam1 Electric Plane Talk 3 Jan 13, 2008 12:09 PM
FS: 2 GWS Vtail Mixers tomi Aircraft - Electric - Airplanes (FS/W) 3 Feb 11, 2005 09:57 PM
chinook - vtail mixers & gyros shooshoo Micro Helis 31 Feb 09, 2004 03:34 PM
question about gws vtail mixers unsped Parkflyers 0 Jan 04, 2004 05:23 PM
On board vtail/elevon mixers...your experience AMTJIM Electric Plane Talk 2 Sep 13, 2003 07:36 AM