Clone Build (EXI 250)

[jthompson]

Some of you already know that I’m fairly new to the hobby and I like challenges. I originally wanted to build a 500 size heli, but ended up deciding that it was out of my budget at this time.

SO, I decided that I would try building an inexpensive 250 size clone.

Not going for a 3d killer here. The whole idea of this project is to build from scratch inexpensively and get the heli airborne. Out of the project I will gain better understanding of how to setup helis and working with pitch/throttle curves, head speeds.

Yep, I know, working with larger heli probably would be better, but I did say I wanted a challenge. And why a clone? Simply cheaper to dive into!

I am quite excited and the parts should start arriving to my door by the end of the week. I am expecting this to be a very slow process, but I will be using this thread to keep everyone posted to how I'm doing.

I'm not going to list off the parts I purchased until everything arrives. I will take some pics and then list them. I just don't want to hear everyone start chattering, "Why would you get that?":eek:

I will say that I did get the EXI 250 and @ $55.00 on black Friday sale, I couldn't say no.

So, hope you guys follow along and help me with my build!

Jim:D

[BrokenRotor]

Can't wait to see what you come up with. Good luck Jim.

[jthompson]

So, I am still waiting for all my parts and the past three days I have been studying and studying. I find heli hobby so interesting because of all the variables involved to achieving your flying style and heli performance. There is so much information out there and point of views; I really had to take everything with a grain of salt and stick with mathematical facts. Even at that I am hoping the best because I don’t have the experience to back up on. Yet.

It was kinda funny how I ended up getting more concerned about everything. I was researching pitch/throttle curves and not trying to master it, just getting the general idea and understanding. Then for some reason, and I don’t know why, but it snowballed all the way down to the motor then working the way back up. (Motor > ESC > Battery > head speeds > throttle/pitch curves > gyro, Est.) Don’t know if it was that exact order, it’s just a map representation. Honestly, at this time, I don’t know why throttle/pitch curves triggered this.

I can’t wait to start putting all these variables together. I am definitely a hand on person, and this is the only way I am going to get a good understanding. Success and failure is a win, win, for me.
I could have asked everyone what I exactly need and it would work great, but I wouldn’t know why or how.

In the mean time, I can hover my 450 around in the basement to keep me happy. Lol.

[MikeB]

Larger heli's are better learning machines. It's easier to make setup changes and your more likely to notice the difference. You'll be supprised how fast the 250 is and how hard orientation can be with it. Time to react is short with a 450 but it's almost nonexistant with a 250. The 250 hardware is very small, it's a pain to work on and easy to break while doing so. It's an intimidating lil beast at 4000rpm and it'll bite your leg off. I really like the 250 but I don't see it as a learning tool. It's more like a toy for pro 3d pilots.

Good luck!

[Jake]

MikeB may be right, however don't let that discourage you. You have a larger heli to compare to, so you'll know if you're in over your head. You'd be a lot more frustrated had you completely started on a 250.

Keep us posted!

[jthompson]

No, I’m not discouraged at all. In fact it motivates me. Not trying to prove anything or anyone wrong neither. I took a lot of time understanding what I was getting into for that size. I know that I perform better and have a higher success rate when I have a challenge or am under pressure. I also use that trait in my job careers. There’s nothing that I can’t do when I put 100% into it and there is so many people out there that think they can’t. Everyone can!

Just think what the Wright Brothers had to use for a learning tool! I have it easy compared to them! I have tones of resources and the great people of this forum!

“A failure in rc heli is far less stressful than a failure in life. I can always go back to the drawing board. “

I do appreciate everyone’s 2 cents though.
And, yes, when I have failures, you guys can get a laugh or give a hard time about it! I don’t get offended to easily!

CHEERS!

[jthompson]

Heli arrived yesterday! First impression, "Awesome".

I open the box and found it to be already assembled. Kinda cool, but also wished it wasn't so I don't have to take it apart to place electronics and what not. This heli looks great. Carbon fiber and all metal with a glass canopy. I spent a lot of time just looking it over to find any defects since it is a clone. I only found one; it was a ball link end that is chipped. Doesn’t look safe to use, so I will be getting more to replace and have on hand.

I don't think much of the blades. They feel like plastic and are really flexible.

I pulled up the T-rex manual because you don't get one with this and it is dam near identical except it doesn’t say Align. Overall, I don't think you could beat it for $55.

I also received my inexpensive programmable radio. Started to play with that.

Tomorrow and next week I will be receiving everything else. Can't wait, I want to start laying everything out and try packing everything into this small frame.



http://www.3drcmn.com/forum/picture.php?albumid=24&pictureid=230http://www.3drcmn.com/forum/picture.php?albumid=24&pictureid=231


http://www.3drcmn.com/forum/picture.php?albumid=24&pictureid=235http://www.3drcmn.com/forum/picture.php?albumid=24&pictureid=234

[MikeB]

The block between the canopy posts looks interesting. Kinda like the idea. Can you get a pic of it a bit closer?

[jthompson]

Mikeb, it is interesting. Its like 3 functions in one. Canopy posts, frame brace and Swash guide. The posts and block are metal and swash guide is carbon fiber.

I would guess its really strong, but wonder if a right crash could do more damage because the canopy posts screw into that block and they may not break loose easily?

http://www.3drcmn.com/forum/picture.php?albumid=24&pictureid=236

http://www.3drcmn.com/forum/picture.php?albumid=24&pictureid=237

[MikeB]

Very cool & thanks for sharing. I think it would survive a crash as well as any other. Looks like you got a great deal. Looking forward to your flight reports :D


Now if only I could deflect these laser beams with my blast helmet on & finish my training, I might be able to fly one.

[jthompson]

Well, I'm still waiting for a couple more small items to arrive, the battery and motor connections. Once I have those in had, I can start testing and post setting up the electronics before fitting into the frame.

I decided I would get the servos fitted and semi installed on the frame. The servos I have actually have a larger casing than the frame holes. I had to sand down three sides on the aileron, pitch, and elevator servos. After a couple tries, they slid right into the holes.

At that point I realized that I would have to take the frame apart so I could install the tabs of the servo on the inside of the frame so the push rods would not be pushing at an angle.

I didn't have to do any modifications to the tail servo. I just put that in place.

Now I will just wait to get the battery and motor connections to do some soldering.

I also decided to install new servos and CF blades on my 450. After going thru a complete setup from servo to head, I dashed down to the basement to see how the new servos and blades felt.

AWSOME! The CF blades added a complete control feeling. From the stock to CF was night and day. I really didn't realize how much difference there would be. The servos had a much better response feel to them too. With the stock servos, it seemed like I had to compensate for my over stick movement because they felt like they responded behind my stick movement. If that makes any sense, it does to me. The new servos feel like the servo horn is moving in sync to my stick movement.

http://www.3drcmn.com/forum/picture.php?albumid=24&pictureid=239


http://www.3drcmn.com/forum/picture.php?albumid=24&pictureid=238

[MikeB]

Sounds like your having fun with it all. The 250's looking good and its great to hear your 450 turned out so well. Can't go wrong with nice servo's and carbon fiber blades.

I've been looking at the improvements Align's done to their 250SE compared the first run of 250's. I was quite impressed with all the stuff they changed. Most of all the change to a larger hex on the majority of the hardware.

[Heli Fragmentus]

I've been looking at the improvements Align's done to their 250SE compared the first run of 250's. I was quite impressed with all the stuff they changed. Most of all the change to a larger hex on the majority of the hardware.
I've heard from talking to several people who have the original version of the 250 is that it is not as durable as the later ones; particularly the landing skids. (Don't know if it matters if the kit was produced on a Friday or Monday vs other days of the week :rolleyes:)

[jthompson]

Today I received my connections for the ESC and Motor. YA!

I put a movie in and busted out the soldering tools. This took me a little while and I definitely got something out of this little task.

First, I HATE JST CONNECTIONS. Yep, I don't think I will use them anymore if i don't have to. Those little bastards are a pain. It could be lack of experience too, and maybe I could have reduced the ESC wire down, but I was determining to make it work. In the end it turned out.

Second, I had over looked putting the male and female ends on the correct device. ya, I ended up putting the female on the motor and the male on the ESC. Stupid, but its going to have to do. I will just have to make sure to cover up the ESC wires if I have the motor unplugged and the battery plugged in. I didn't even notice until I was going to test.

The last thing I did tonight was just do a quick test to make sure it worked and the TX was bound to the receiver. Everything worked out just fine.

So, besides soldering the connections backwards, I am happy.

http://www.3drcmn.com/forum/picture.php?albumid=24&pictureid=240

[MikeB]

I've been soldering since 6th grade and it's deffinately an art. The JST's are easy once you've done several and get it down. A good soldering iron/pen helps alot. I have the same one your using and it's not the best but it works.

I usually solder the deans on "then" remember I forgot to put the heat shring tubing on first. Hard to get the tubing over the wire at that point. :doh:

Sounds like you'll have it in the air soon! Good luck with the maiden.

[Hendo67]

I have been getting a little soldier iron from Lowes that works great.
http://www.action-electronics.com/grc/wetb100pth.jpg
I think they cost around $10.00. The pistol shape works well and it is a nice balance between power and size, and has worked on every connector I have used so far.

[jthompson]

I usually solder the deans on "then" remember I forgot to put the heat shring tubing on first. Hard to get the tubing over the wire at that point. :doh:


Actually, I did forget to put the shrink tubing on, but since they were bullets, it wasn't a problem. :D

I like that pen pistol iron idea. I will have to check it out. I need a new iron anyways. Notin fancy, just functional.

I think if I have time tonight, I will start laying out where I want the electronics on the heli and get an idea on routing all the wires.

Still waiting for some pinions, so I will wait to put the motor in. Although, after ordering them, I think they are not going to work. I ordered .5mod and I think I should have gotten .4mod. Hopefully they work, if not, then I will have extra pinions!

[MikeB]

I'm about to mod the battery tray on mine by removing some CF and lowering the front 2 holes for the battery plate. Tired of having canopy issues and this will resolve it all. Should be no issues with the battery not wanting to stay put and the balance with a larger pack is probably better. Will make it look more like a 600e but not quite as vertical.

Will post pics when I'm done.

[MikeB]

Horrible pic but it turned out well. Canopy fits much better and balance is perfect. Hopefully it doesnt have off flight characteristics because of it. Always wants to fly upside down or something. Left is modified.

[jthompson]

Interesting, I will have to keep that in mind. Thanks for posting that on this thread. Any tips or mods to help out on 250's is awsome.

I notice that so many people use a 3cell over a 2cell. Have you used a 2cell on your setup?

Last night I put on my ESC to the frame and hooked all the electronics up for some more testing and to see how much I will have to pack into the frame. I havn't mounted the Receiver, gyro, motor, (FYI: The pinions I ordered are to large, need to order up a nother batch).

There is so much yet to do, not sure exactly yet how I want everything installed and where to start with the setup.

[MikeB]

I've only seen pictures of people at Align flying 2S before the original 250 release. Need a steep pinion for headspeed on 2S and you can really only do forward flight and hovering with it. I think they abandoned the 2S idea because it did not work well.

My battery issue was odd. The packs would fit in the old 250 without the mod but the new canopy required the SE to be modded in this case. I wouldn't recommend it unless you have a need to do it. I worked out some braces so I can run the plate at either angle should I need to go back to the original.

Sorry to hear about the pinions. I hate mounting the electronics so it's always neat to see where other people stick things. On the new 250 I put the gyro on the gyro platform, reciever on the bottom of the platform but further tword the shaft so It does not stick out the back much. Esc went on the bottom of the heli between the skids.

Don't quote me on this but I think this is what I read.
15t Pinion = 3s about 3500 @ Hover
16t Pinion = Your insane or your name is Bert K, 3s
17t Pinion = 2s (low head speed)
18t Pinion = Not sure this exists but but it would be for 2s & a higher headspeed at the expense of amperage.

[jthompson]

Hope everyone had a safe and fun holiday! I sure did, 7 days straight off and I did plenty.

During one of the days off, I decided to get the electronics installed. What a task with this size of heli. I ended up having to split the top and bottom apart to get everything into place. After a few hours, I finally finished. Then only thing now is to install the motor and pinion.

I have already started to setup the radio and setup the heli. Getting closer!

One more check of electronics before installing:
http://www.3drcmn.com/forum/picture.php?albumid=24&pictureid=243

Side one, finished install:
http://www.3drcmn.com/forum/picture.php?albumid=24&pictureid=244

Side Two, Finished install:
http://www.3drcmn.com/forum/picture.php?albumid=24&pictureid=245

[MikeB]

Your rudder servo arm looks to be way to long. The ball should be around 3.5mm from the center of the servo output shaft. If it's that long you don't get enough travel out of the servo and performance suffers greatly.

I see some 2s packs. Are you going to run 2s? If so I'd recommend you don't try any 3d unless your really high in the air.

Usually takes me a couple days to run and mount the electronics. I'm too damn picky and I always hate it in the end either way :doh:

I also see you have a different length arm on the elevator than the aileron and pitch as far as ball placement. I know you did this to make the rods 90 probably but it won't work out right in the end.

All in all the heli looks great. Good job!

Edit
- If your motor's an outrunner you may have problems with it rubbing those servo wires in the front and the zip tie under the motor may need to be tighter so it does not rub the bottom.
- On the align models the gyro plate can bu moved up to a higher mounting location which would raise your gyro to where it's mostly shielded by the tail brace bars.
- Zip ties on a gyro never work well. The pad should hold it and if in doubt use a soft velcro strap. Worst case put some padding between the zip tie and the gyro.
-with a 2s pack I think your going to be tail heavy with the current mounting locations. Can get some lead weights for the front or move the reciever or esc under the Bat tray.

Not being a critic. Just trying to help with some suggestions.

[jthompson]

Nice suggestions, and appreciated, that is why I am putting up pics!.

Ok, I will be running a 3 cell eventually; don’t believe everything in the pic. Those are just some 2 cells laying around that I use for testing.

I will work on the rudder servo arm. I will have to put the servo at an angle I would guess so that I can get the pushrod as close as I can to the center of the boom.

As for the ball placement on the elevator, I did as you speculated. Position to make a 90 and realistically I should have it placed in the same position as the aileron and pitch? Makes sense, and it could explain why I thought I wasn’t getting the movement I expected in the swash when I was testing.

Motor will be an out runner and it would have worked just fine with the current motor I have. However, I thought the same thing because I decided to get a different motor.

The zip tie that is on the gyro is not for the gyro its self, it is banding down the wires that are on top. Will the performance be affected by the zip tie?

Good stuff and greatly appreciate all the advice!

[MikeB]

I will work on the rudder servo arm. I will have to put the servo at an angle I would guess so that I can get the pushrod as close as I can to the center of the boom.

Correct, you will need to tilt the servo down till the ball is as close to the bottom of the boom as possible. Trim the extra length off the servo arm. The rod does not need to follow the centerline of the boom exactly and can be angled slightly.

As for the ball placement on the elevator, I did as you speculated. Position to make a 90 and realistically I should have it placed in the same position as the aileron and pitch? Makes sense, and it could explain why I thought I wasn’t getting the movement I expected in the swash when I was testing.

They should all be the same. It's impossible to mechanically fix the elevator issue on a 120degree swash. It's always corrected in the radio programming. If your not getting enough movement in the swash, increase your swash mix numbers. Increasing PITCH will give you more travel up and down. AILERON & ELEVATOR mixes control the amount of tilt you get side to side and forward to back. Always go with the manuals rod lengths to start and then level the swash at 0 pitch by adjusting the three rod lenghts. Once the swash is level then adjust the blades to 0 pitch with the two adjustment rods on the head. At this point set your swash PITCH mix to get the amount of possitive and negative pitch you want. Check your swash is level at min and max pitch. If it's not level you need to adjust your servo travel limits (ATV's) in the radio to make it level at both extremes. At this point you'll notice the back of the swash will not stay perfectly level while you move it from min to max pitch and back. Thats normal and can only be corrected by higher end radio programming. Most people just live with it.


Will the performance be affected by the zip tie?

If the tie touches the gyro it will transfer all your vibrations from the frame to the gyro and negate the dampening from the pad. In effect it would be almost as bad as glueing the gyro to the frame.

Worried when we didn't hear from you for a while on this. Anxious for the first flight report!

[jthompson]

MikeB, I will have to take some new pics for you, but I had done all of what you suggested. I ended up taking the entire thing apart again just so I could move things around.

The same day, my new motor arrived just in time! So I spent the next 4 hours routing wires, applying what you suggested, setting up the rotor head and rudder, and setting up the radio. Basically the whole dam thing again. I ended up realizing I didn’t set the head up properly.

The only thing I need now is new 3cell lipos. I don’t have them yet, but soon.

However, I couldn’t take it no more and I just had to do my first test flight. So for the test, I just used 2cell batteries. I intended to see how it would hover in normal mode and see if the tail would hold. I decided to just keep it low and easy.

I have to say, for my very first heli build and setup, I was really, really happy! It was such a cool feeling building and then being able to get it into the air without any huge issues.

I was also surprised how well the tail held. I was able to hover without any rudder input. Just cyclic input. That was really cool.

I did notice that there are some more adjustments needed to the gyro. I have some wag after left or right input. Just when it holds its position witch I thing I can workout. But I will not do anymore adjustments until I get my 3cell lipo and see how everything holds.

For my very first build and test flight, I made sure to get it on my camera.

Here is a link to my video: http://www.youtube.com/watch?v=2KglzbzxBFg

Thanks for you advice MikeB!

[MikeB]

Your welcome. Just like the internet, I'm wrong alot of the time so take it all with a grain of salt and some tequila.

Great job :D

I've been busy working on several of my heli's and I've not maidened my 250SE yet. I copied Eric and put the gy520 and 9257 servo on it. Still have to install the 16t pinion and go over the head and radio settings the final time. My normal 250's getting the new weighted tail blade holders and the stock gp750 gyro and a 15t pinion. My 450 that I stole the 9257.gy520 from is getting the mini-g and a 3400G servo. My nitro 600 went thru a overhaul, went from flybarless to the old flybar setup to break in the new motor. I've got it converted back to flybarless and now I'm waiting to buy a new flybarless controller. The 600 was a fun breakin, I turned down the blade pitch & headspeed to keep the load down on the motor durring the process. Obvioulsy I did not have almost any pop but it was pretty unboggable even rich and at a low headspeed. Made for some nice tick-tocs. I'm slowly going crazy waiting for warm weather.

[jthompson]

Oh my! you have many projects going on. I think I will just keep 1 to 2 at a time lol. I don't want to hurt my brain. Putting togeather a 250 was a lot of work. There is no room. It helps to do things in sequence so you don't have to tear the dam thing apart 4 times so you can make more adjustments.

Do you do any blade balancing or tracking? I didn't do nothing of such and spoolingit up, I didn't see any tracking issues.

[MikeB]

I usually try to balance the blades, not so much on the 250's but I've had to do it alot on the larger blades. Blade tracking is important for several reasons but in general it will tear up your head dampeners and cause alot of vibrations when it's off.

If it looks good in the air then your prolly ok.