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Old 01-13-2015, 09:10 PM   #1 (permalink)
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Default 700n DFC Helibug build thread

I decided to do a build thread for my gas heli because surprisingly, to me anyway, there doesn’t seem to be much interest, compared to electric helis, in recip gasoline engine helicopters. My main interest in building a gas heli is the longer flight time. I am perfectly happy with the way my 450 flies but I don’t see changing the battery 7 times just to fly for half an hour. I get real tired of pulling the fussy canopy off, changing the battery, and putting it back on. So the real motive of this whole gas heli project is to have at least a 20 minute uninterrupted flight. With just a couple relatively small flight batteries I’ll be able to fly for at least 40 minutes, maybe more (I’ll have to see). As of right now my heli has made one 5 minute flight. Winter is interfering with my fun.

This isn’t an A-Z build thread but rather I’m just going to touch on anything I think may be unique and interesting on my heli. Before anything else I want to thank all the good people at helifreak that have posted information that was extremely useful for this project. Most of what I’ve done here is based on sage advice of the experienced builders here at helifreak. Thanks to everybody!

I started planning this heli the end of September, first of October. My original plan was to build a .30 size nitro heli with a .50 size gas recip in it. The budget I thought would be $500 to $1,000. I was thinking closer to $500. I saw the small Horizon Hobby Evolution gas engines and thought, “why not put that in a heli?” Long story short, I was convinced by jharkin that it would be throwing good money after bad trying to build a gas recip with anything smaller than a Zenoah engine. That meant a .90/700 size helicopter. My $500 budget just got blown to bits. I was not deterred because at this point I was committed to my 20 minute recip heli.

An interesting story; I found a used Century G30 with a Century PUH290 engine for sale on another forum at $800. It was advertised as barely used mint condition. I emailed the owner and sight unseen told him I would take it. Another long story short, the guy refused to sell it to me! He just ignored me like I was trying to sell him diet pills! I could only get about 2 emails out of him. It of course made me mad but then I later realized he had in fact done me a huge favor. The gas tank on a G30, I found out, only holds about 10 minutes (at best) of fuel with that engine. I would have been even more mad had he sold it to me.

I ended up deciding on the Helibug front engine conversion for the 700n DFC. I thought it looked to have the best chance of keeping the center of gravity of the model near the main shaft. Other designs either had small gas tanks or looked tail heavy. I haven’t checked the final CG of my heli but without canopy, gas or battery it’s about a half inch behind the main shaft. I’m happy with that.

Originally I ordered a G270RC engine. I was worried about a 290 having too much vibration and the “instructions/illustrations” on the Helibug web site show a 270. Then I noticed the 270 and the 290 weighed exactly the same and the 290 was actually cheaper to buy because it was on sale. Darn! I coulda’ had a V8! (you youngsters might not get that) So I thought about it for a day or so. It was really bothering me. Finally I realized just because the piston is 2mm larger in diameter doesn’t necessarily mean it weighs more than the 270 piston. And besides, the Zenoah engines don’t have a balance shaft to counter the sideways momentum of the crankshaft counter balance when it is halfway between TDC and BDC anyway. What the heck I just ordered the 290 and sent the 270 back. I want all the power to weight I can get.

The first part I ordered; even before I had decided on which heli to buy; was a Fromeco Kiwi dual voltage regulator. It was on sale for $20. I figured I saved at least $60 because it’s out of production. I pat my back on that one. I was going to use the 4 Align 5V servos that come with the super combo 700n kit and buy an HV servo for the throttle. It took about a week or two after I got the Kiwi before I realized that wasn’t going to work. The 5V output was iffy at best and it only had 4 five volt outputs. Duh, I need 5 (4 servos plus the gyro; I forgot about the gyro). When I was bench testing the Kiwi I was lazy and instead of making some test leads that fit the pins I put the meter probes directly on the pins and for about a tenth of a second I must have shorted 2 pins. That was all it took to kill a channel. I thought all of the 5V outputs would be on a common bus? Apparently not. So revision 1 was to find a better dual voltage regulator and for good measure buy some HV servos for the cyclic so the 5V output would only have to carry the gyro, the receiver remotes and the tail servo. I sold the Align 5V cyclic servos on ebay. I decided on 3 ProModeler 420 in-oz HV brushless servos for the cyclic. The regulator I liked is the Turnigy sold by HobbyKing.

My original plan always included the Spirit Systems FBL gyro with Rescue Mode. It was that or BD at $500. I was never going to fly a $2,500 helicopter without Rescue Mode. I decided on the Spirit because people were raving about them and it is the newest, and presumably, most modern hardware available. I planned on connecting 2 Spektrum DSMX remotes to it. Turns out, If I understand this correctly, DSMX remotes only work on the Spirit if you bind them to a Spektrum transmitter that can work at 11ms frame rate. My Walkera TX apparently doesn’t bother with 11ms frame rate and as such I ordered a Spektrum DSMX full receiver. Revision 2.

Also part of revision 2 was the realization that if the throttle servo stopped working during flight, how was I going to slow down the engine? Hmmmmm. I originally was going to keep the remote satellites connected to the Spirit gyro using DSM2 (and wait for a firmware update for DSMX) but when I realized I also needed a remote control ignition kill switch that committed me to a full RX. I also ordered a RC-100X kill switch. The normally closed relay is perfect for grounding the mag. I set up failsafe so if I shut off the TX (or lose signal or flip aux4 switch) it kills the engine.

In a somewhat unusual manner I’ve decided to post pictures of the final model first. As I get time I’ll go into some of the details of my model with some new posts and pictures. These are large 5MB high res files from my good camera so you can see detail. It looks like after you click a link it opens in a Google viewer (on my computer it does). To see full resolution you will have to click download in the Google viewer and then choose open to get it into your default image viewer. Please be aware of the bandwidth if you’re using a cell phone.

Pictures:

https://drive.google.com/file/d/0B3P...ew?usp=sharing

https://drive.google.com/file/d/0B3P...ew?usp=sharing

https://drive.google.com/file/d/0B3P...ew?usp=sharing

https://drive.google.com/file/d/0B3P...ew?usp=sharing

https://drive.google.com/file/d/0B3P...ew?usp=sharing

https://drive.google.com/file/d/0B3P...ew?usp=sharing

edit: Following Rototerrier's advice here are the pictures downsized for convenience












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Old 01-14-2015, 07:48 AM   #2 (permalink)
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There's plenty of interest. There just isn't much "New" interest. It's a small circle and those of us that are in it have been in it for a long time now. We've already seen and done it all. Anything else is just more of that same.

Beautifully built heli though. Love the clean wiring. You should upload the photos to helifreak so folks don't have to click out of helifreak to see them.
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Old 01-14-2015, 02:29 PM   #3 (permalink)
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Thanks for the compliment. I added downsized pictures that appear in the post. Still pretty big though.
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Old 01-14-2015, 02:48 PM   #4 (permalink)
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Default Congrats George!

Very nice, clean build there! Im jealous of you guys with such neat wiring


Any flight reports?
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Old 01-14-2015, 03:38 PM   #5 (permalink)
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Thanks for the compliment Jeremy. I do have a partial video of the first and only flight. I got shut down by winter. The heli flies as good as I'd hoped but of course one five minute flight flying like grandma isn't an acid test. We'll see when I get more brave.

https://www.helifreak.com/showthread.php?t=673865
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Old 01-14-2015, 03:59 PM   #6 (permalink)
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Looks great George, I dont know how I missed that thread. Dont feel like grandma... my first gasser flight ever (only a year ago!!) I didn't do much more than hover and fly up and down the runway at 10ft altitude... my knees where rubber!


Next we have to teach you the secret of heated radio gloves
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Old 01-20-2015, 01:45 PM   #7 (permalink)
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Continuing with the build theme of this thread. I started with prepping the engine. The first thing I figured out was there isnít any handles on the engine. Unlike working on an engine mounted to a lawn mower or string trimmer or something, I first needed to fabricate a fixture to hold the engine so I could wrench on it. I just took a piece of metal I found in the basement and did some cutting and drilling on it so I could mount the engine to the bench vise. I bought some bolts from the hardware store to use with the mount.




I took out the spark plug and found the gap in spec. The cylinder was a little dry so I put a few drops of gas/oil mix in the cylinder and then the piston moved a lot smoother. Then I used a standard issue piston stopper from Daveís Discount Motors where I bought the engine to remove the flywheel nut so I could Loctite it. Iíve had this nut come loose on a 2 stroke before and I wanted to set proper torque anyway; just to make sure. BTW I used a torque wrench for all the fasteners on the engine and the spark plug. I thought about taking each cylinder mount bolt out one at a time and doing the same as the flywheel nut but decided not to tamper with them. Iíve heard of them coming loose too but Zenoah put lock washers on the bolts (an improvement) so I didnít want to disturb the assembly. Iíll just watch it close.

In the picture of the vise you can see a really nice fan cover I bought on ebay to replace the recoil starter. I installed that cover but it only saved me 14 grams (vs the recoil) because the aluminum on this new cover is really thick. It fit and looked great but was not to be as I will explain. You can also see a 6mm starter shaft I made from a T-handle wrench. I made the starter shaft to use in my cordless drill.

One of the reasons I chose this Helibug kit is because it uses the original Align 700n clutch. While not nearly as powerful as the Zenoah clutch used in other kits it does have a starter shaft that runs through the whole clutch assembly to maintain coaxial alignment of the disk and the bell. The Zenoah clutch relies on external structure to maintain alignment of the clutch disk and the clutch bell. A possible source of extreme vibration in the event of a misalignment I think. I was planning on using the starter shaft from the top for starting the engine but was at the same time a little skeptical that such a small diameter starter shaft and correspondingly small sprag clutch (one-way bearing) could withstand the spikes in torque that such a large displacement gas engine would create. A gas engine the clutch and starter shaft were never designed for. But I really didnít want a recoil starter that would require putting a foot on the landing skid like I was starting a Lawn Boy and the recoil starter makes the heli look like a string trimmer. Although now that I think about it some people, not me, can use their heli as a string trimmer! So I guess itís more appropriate than I thought.

Anyway, Iím getting ahead of my engine build but after about 10 engine starts the sprag clutch started slipping and the pull starter went back on the engine. Maybe Lynx put too much grease on the sprag clutch, maybe not. Iíve given up on using the starter shaft for starting the engine in any case. Anybody want an engine cover? Ten bucks, free shipping. At least I didnít buy an Align electric starter for $150.

Iíve read threads about people having cooling fan heat problems with their Helibug conversions. That is heat from the engine causing everything under the canopy to get too hot. I took that warning to heart and made 2 modifications to prevent any trouble.



As seen in the picture the first mod I made was an extension for the fan shroud. A picture before putting the heli together wouldíve been better but you can see whatís important. For whatever reason Zenoah makes a big curved cutout in the plastic fan shroud on the side of the cylinder away from the fan. I used .070Ē sheet aluminum and made an extension plate big enough to cover the curved cutout. There are 2 mounting holes in the Zenoah shroud; one for the bolt that threads into the side of the cylinder and another that is unused (presumably for a different application). I used new corrosion resistant steal (CRS) cap screws. The mounting screw had to be longer than original because of the thickness of the extension plate and I added another shorter screw to protrude into the unused hole in the plastic shroud to keep the plate from turning. I threaded the hole for the shorter cap screw in the extension plate and secured it with Loctite.





The other mod I did was to add a 19mm spacer I bought from Daveís Discount Motors that moves the muffler away from the engine cylinder. It comes with 2 new exhaust gaskets but I bought 2 new stock Zenoah gaskets to use instead. The stock gaskets are metal reinforced and look like good quality. I also had to add a spacer to the rear muffler mount bracket; also of 19mm (3/4Ē) length. The muffler mount bolts had to be replaced with 19mm longer ones. This proved to be rather difficult. As usual I wanted bolts made out of CRS if possible but couldnít find any. I settled on carbon steel bolts from a hardware supplier on the Internet. I drilled the heads of the long bolts .040Ē for .032Ē CRS safety wire and used anti-seize on the threads. Steal and aluminum donít like each other especially at high temp. Someday, if I need to take them out again, I might be able to get them out without taking the aluminum threads with them. For the rear muffler bracket bolt I was able to find a longer CRS cap screw at the hardware store. Weíll see next summer on a hot day when I fly for 20 minutes how successful my mods are. So far, without much load on the engine in the cool weather of winter, the engine runs real cool. Surprisingly cool in fact.

It was finally time to start assembly. The first piece to go on is the Helibug clutch mount. It fit the engine shaft perfect and I cleaned the engine shaft and the mating surface of the clutch mount and left them dry. I debated about whether to use oil, anti-seize or Loctite and decided dry would probably be best. Even though there is a keyway in the clutch mount there isnít a Woodruff key slot in the crankshaft so it is a friction fit. I decided not to use Loctite because in the unlikely event of a blade strike (howís that for optimism) the clutch mount may be able to absorb some energy by rotating on the engine shaft. Loctite would have made that harder; oil would have made that easier; I wasnít sure so I picked what I thought would be something in the middle. I hope I never have to test my theory.

Next was the Lynx clutch disk included with the Helibug kit. As I understand it Align used a clutch liner in the clutch bell that was 1mm thick (if I remember right). Lynx made their clutch disk .2mm larger to compensate for too much gap between disk and liner. Then Align changed to a new blue liner that is now 1.5mm thick (again if I remember right) but Lynx still makes the gas clutch disk .2mm oversize. That means the clutch disk now binds with the clutch bell. So I made a tool using the align clutch disk on a clutch mount with sandpaper and sanded away some of the brand new clutch liner to create a proper clearance. Not quite enough it turns out as my clutch still drags a bit but itís usable and will break in; soon I hope. If I had it to do over I would have taken the time and turned the Lynx gas clutch disk down .2mm on a lathe. But like I say, it works; I just have to hold the rotor head after startup until I step away from the heli.

When I went to install the Lynx clutch disk on the Helibug clutch mount it rocked a bit. I chamfered the inside edge of the bore of the clutch mount to correct that. I decided to use longer screws than came with the Helibug kit as the hole depth allowed that. I used CRS cap screws with lock washers from the hardware store. I checked the runout of the clutch disk on the engine and it measured .004Ē with a dial indicator. I was hoping for better but I consider this serviceable. Ended up looking like this.



The holes in the Helibug engine mounts were just rough cut and I was able to easily ream them with a drill bit. I used a 4Ē round file to finish out the slots for the Align engine mount bolts. I mounted the Helibug mounts to the engine using longer CRS bolts from the hardware store than the bolts that were included in the Helibug kit. The hole depth allowed it and I also used lock washers and Loctite here too. For a solid metal to metal assembly like this I like the idea of having the compressibility of lock washers if they can be used. Ended up looking like this.



The lever on the throttle valve of the carb gets rotated 90 degrees in this installation. I added a touch of dielectric grease to the terminal on the spark plug to reduce ignition noise. To be continued.
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Old 01-20-2015, 11:06 PM   #8 (permalink)
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Safety wiring the exhaust bolts, why didn't I think of that

Beautiful heli
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Old 01-21-2015, 06:20 AM   #9 (permalink)
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Interesting ... anti-sieze and safety wire on the exhaust bolts..

Most of us have more of a problem wit the exhaust bolts loosening from vibration than staying in there long enough to seize from dissimilar metal corrosion. Typical thing to do is coat the bolt threads with red RTV as a kind of high temp thread lock. I do this as do a lot of others. Thinking about it, the film probably provides an anti-sieze property as well.

FWIW, I have never had a bolt in a model engine long enough to seize. Last summer I had to pull the muffler off my DA-50 for maintenance - those bolts had been in for 5 or 6 years and came out with no trouble. black oxide M5s threaded into aluminum, same as a Zenoah. Nothing on the threads either.

Now the car is another story... I always use AS liberally for threading sparkplugs into the aluminum head Especially on the Iridiums that wont get touched for 100k.
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Old 01-21-2015, 03:56 PM   #10 (permalink)
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Thanks mitsudriver for the compliment!
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Old 02-04-2015, 09:55 AM   #11 (permalink)
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Starting on the airframe I realized this heli was different. With the 450 and 250 electric helis you assemble the frame and at the appropriate time bolt in the motor. With the 700n Helibug you start with the engine and build a helicopter around it. Kinda’ funny; an engine with rotor blades more or less.

The Helibug side frames and bottom plate are real nice. The cuts were all clean and in the right place. I only had to make one little adjustment to the side frames that I’ll get to. I noticed right off that the 4.5 lb Zenoah bowed the bottom plate with the weight of the engine on the landing skids. Therefore I set the bottom of the engine on a small box so its weight wouldn’t be on the frame while I assembled it. Everything lined up great but I did have a .020” gap between the Helibug engine mounts on the engine and the Align engine mounts that attach to the side frames. A washer on each bolt was about the right thickness; you can see them in the pictures of my previous post. The Lynx clutch disk centered very well with the clutch lining in the Align clutch bell. You can see that in the picture of the Lynx clutch disk in my previous post as well.



Here is a better picture of the fan air deflector mentioned in the previous post.





The Helibug instructions/illustrations on the web site suggest that adding a 3rd main shaft bearing is an option. To me it looks pretty much mandatory and I’m very glad the Helibug designer made that possible. Without the 3rd bearing it doesn’t look strong enough to me. The only bad part is the bearing is only sold in pairs so I ended up with a spare I probably will never need. The bearings fit perfect by the way.

Getting the gas tank into the main frame was a bit of a puzzle because of the vent fitting molded into the tank and sticking out of the top of the tank on the right side. The solution I used was to put the tank into the right frame first and then insert the edge molding while lubricating it with rubbing alcohol. A brass o-ring tool worked well for this. If you install the protective edge molding first the tank won’t fit in the cutout of the right side frame. The tank I received with the kit didn’t have a large hole in the center that requires plugging. The plug for the fuel delivery line didn’t fit very well as the tank wall was too thick for it. I was sure it was going to leak but so far it hasn’t. I fit the inside tank line using the guide from Mr. Shurley; thanks! The engine had an available threaded hole so I used that to attach a couple of clamps for the fuel lines.



I ran the vent line from the top of the tank down through a hole I drilled with a grommet in the lower right frame below the tank. Then I ran it up the inside of the right frame above the tank and clamped it. From there it goes across to a clamp on the left side frame above the tank were it then runs down to the bottom of the left side frame and is clamped where it exits the bottom of the airframe. That big W pattern made more sense to me than trying to find a place to make coils. The black tubing outside of the tank is all neoprene. The tube in the tank is the original Zenoah tubing with a Stens fuel filter.

Vent line outlet below bottom plate. I used an o-ring to keep tube from slipping out.




The arrows show clamps on left side frame viewed from right side.



That reminds me of a thought I had while building. For such a large helicopter the 700n doesn’t have very many places to “attach things.” By the time you subtract the area taken up by the large fuel tank, the main drive gears and all the servo linkages there’s not much left for accessories. I think my 450 has more places to stick things to the side frames. It wasn’t a problem as I found a place for everything but I thought it was an interesting situation.

The plastic molding Align calls the receiver mount required quite a bit of customizing to suit me. Of course the servo mount for the throttle is on the wrong side for the gas engine and since it’s not going to have the Align 2 in 1 voltage regulator the receiver mount isn’t really the right shape for other more appropriate accessories. The first thing I noticed was the molded shelf for the gyro was curved instead of flat. It also was slightly slanted down towards the nose. I thought I just got a bum part ‘til I noticed on the Helibug web site pictures that their receiver mount had the same defect.



I fabricated a new gyro mount out of .070” aluminum sheet metal and bonded it with black RTV. I made a cover, also out of aluminum sheet metal, for the unused left side servo mount. There were ribs around that mount as well that I cut away so the surfaces would be flat for attaching the dual voltage regulator I wanted to mount there. I mounted the regulator so the dip switches on its back would be accessible.



On the right side the Helibug throttle servo mount plate needed a support bracket at the front. I made one out of aluminum sheet metal with a 90 degree bend in it.



The ProModeler HV servo I used for the throttle was too deep for the available space so I had to do some cutting behind it. You can see that a little in this picture as well.

You can also see in the various pictures that all the servos, except for the center cyclic servo which mounts with original equipment machine screws, were mounted with CRS round head machine screws and plain nuts fixed with Loctite. The tail servo mount holes in the receiver mount had bosses intended for sheet metal screws to self-tap into. I cut those away and opened the hole for the same 2mm machine screws and plain nuts used on the other servos. It was a bit of a pain getting in there with a wrench to hold the nuts but I like the security of the machine screws vs “wood screws.”

I cut and terminated all the wires to length. I installed the Futaba type terminal pins with some nice crimpers from servocity.com. For the very thin remote receiver wires I found JST-ZH 1.5mm terminal pins at digikey.com and crimped them with small needle nose pliers. I couldn’t find the correct crimpers for those tiny connectors for less than $400. The needle nose pliers work fine but they take some practice and patience for sure. I used very small cable clamps to secure the wiring harness as required. I like them a lot better than trying to find something to strap to and I think they’re worth the extra effort to install. I put one inside the left side frame to hold the harness that runs under the cyclic servos to the rear of the frame.





To be continued.
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Old 02-09-2015, 08:33 PM   #12 (permalink)
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When I installed the tail boom I found the gear mesh was a little tight. This was the only place I had to do any fitting to the Helibug frame pieces. I used a 4Ē round file to elongate the mounting holes in the side frames for the tail boom forward tail case mounting screws and alignment lugs. It only needed about .010 to .020Ē. I didnít like having to do that but it seems it hasnít adversely affected the security of the tail case mount. As they say it is what it is and the gear mesh is real nice now.

The various control rods included in the Align kit were a challenge. Part of the problem is the mount for the tail servo in the receiver mount and the ďseesawĒ linkage on the back of the frame are 9.5mm farther apart with the Helibug conversion than with the stock Align kit. The various control rods come in three sizes; 2, 2.5, and 3mm.

The 2mm push-pull rods and rod ends that go between the servo horns for the 3 cyclic servos and ďthe contraptionĒ (as I affectionately call the three swashplate bellcrank assemblies) were no problem. Everything there fit perfect. Problems started with the left and right 3mm linkages (DFC linkage rod B) that connect the bellcranks to the swashplate. The rods were too short to adequately engage with the rod ends. There was only a 4 thread engagement. The center bellcrank linkage is fixed length and it was fine as the rod end is held on with a nice long screw.

Considering the energy in a 5 foot rotor turned by a 3.5HP engine; 4 threads in a plastic rod end sounded pretty scary to me. Amazingly Align has chosen to counter bore the plastic rod end so the threads of the metal rod donít hardly bite into the plastic until itís threaded in about 1 to 1.5mm. By that time itís only about 4 more turns until you reach the proper adjustment length of the rod assembly.

My solution for those two linkages was easy. I found a different set of linkage rods intended for a different 700 kit that were 56mm long instead of the 47mm rods that came with my kit. With those rods completely bottomed out into the plastic rod ends the linkage assembly length was just right. I didnít have to shorten the new rods at all.

The rods that thread into the DFC linkages (linkage rod A) that go between the swashplate and the blade grips were also too short. It finally occurred to me the linkage rods (B) that I wasnít going to use were perfect substitutions for the DFC rods; I just had to cut down the fillet radius on the sides of the middle nut to zero using a drill motor as a lathe, cut threads all the way to the nut using a M3x.5 die and then cut the rod to the right length. In the following pictures bear in mind the counter bore inside the plastic rod end is almost as deep as the metal collar on the outside. The result was very good. The second picture shows how short the original rod was.






Next I moved on to the two tail rods. Because of the 9.5mm stretch of the side frames I mentioned earlier the forward 2mm diameter shorter control rod (tail rod A) was too short. The longer graphite rod (tail rod B) on the tail boom which has 2.5mm diameter rods (tail rods C) glued into the ends was also too short but that didnít have anything to do with the stretched side frames; it was just too short to start with.

Remember I mentioned the control rods on the 700n were 2, 2.5 and 3mm. I ordered dies of M3x.5mm, M2.5x.45mm and M2x.4mm at the tune of about $40. But that was a mistake. The 3mm die worked fine but after I threaded a 2.5mm rod with the 2.5mm die I found out the hole molded into the plastic rod end for that control rod was too big. The threads of the metal rod barely cut into the plastic. In other words Align doesnít use an M2.5x.45 die for their 2.5mm control rods. They use something larger. There is a rare metric thread size M2.6x.45mm which probably would be the right size but I just used a 2mm rod end on the 2.5mm rod by reaming the hole in the 2mm rod end a little. That worked good too.

This is a picture of the long tail rod with a longer 2.5mm diameter rod glued in. I used a soldering iron to get the original 2.5mm rod out of the graphite rod. You would think that Align would have tapped the aluminum collar on the end of the graphite tail rod so the 2.5mm rod would screw into it and the large interior surface area of the collar would bind the assembly to the graphite rod. You would think that but youíd be wrong. Align just has a hole in the collar and the 2.5mm rod just glues into the center of the graphite rod. But it works I guess.



I ordered a 300mm length of 2mm control rod to cut down and thread for a longer forward tail rod (A) and intended to thread it with the M2x.4mm die I had bought. As with the 2.5mm die the 2mm die was too small. In fact it wouldnít even thread onto the 2mm rod at all since it was so small. A 2-64 NF die on the other hand was a perfect fit. Who would have thought Align would use an SAE size thread. The graphite sleeve that fits over the forward rod was still too short but I filled the extra space with a short piece of fuel tubing. The stock 700n kit control rod for the throttle was the perfect length and didnít require any modifications. After all that fooling around with control rods, that probably took three weeks with shipping times, everything rigged up very nice.

I hadnít thought of installing a remote control kill switch when I had the engine out on the work bench so I had to remove the bottom plate and engine fan cover to install one. I used an RCATS RC-100X switch and piggy backed the wires to the connectors that plug into the Zenoah push button kill switch on the fan case. Those connectors have a divot on the back where the crimping dies used at the factory had made a nice spot to scrap clean and solder to. The original plastic connector covers were easy to slip off and back on again so it was an easy modification. Zenoah even left a hole in the spark plug wire fan case grommet for the remote control kill switch wires to pass through out of the fan case.



The only other surprise I had building the 700n was the canopy. When I pulled it from the box I found the canopy had been squished at some point in time hard enough to pop one side inside out which put a crack in it. This surprised me since the canopy was in a box that was in perfect condition which was in the big box which was also in perfect condition. I was able to pop the dent out and repair with a scab patch on the inside of the canopy. Looking at the outside you canít see the damage, it didnít flake any paint, unless you know where to look and get the light just right. I had to put washers for spacers on the rear canopy mounts. Otherwise it rubbed on the main shaft drive gear.

People ask me, ďwhy didnít you send it (the canopy) back and make them give you a new one?Ē They donít realize it would have to go back to China. Took me 30 minutes to fix the old one.



A really strong towel bar from Ikea seemed to be the right price for a storage rack. This is the 700 in its new home.

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Last edited by TheBum; 01-10-2018 at 10:23 PM.. Reason: Fixed broken link
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Old 03-13-2015, 08:42 PM   #13 (permalink)
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I got my second chance to fly Monday, mostly good news. Sadly no video, I didnít have a cameraman. Started with a full tank of gas and a full charge on the battery; after a 5 minute warmup and 20 minutes of just flying around finished with about 3/4 of an inch of fuel left in the tank. The 2200mah Turnigy battery took 513mah to recharge so I figure it would have lasted at least 40 minutes so it looks like Iíve easily met my goal of having a 20 minute endurance. Yeah.

The heli flew nice with the Spirit FBL; about the same as my 450 with the 3GX FBL gyro which is also good. The only real problem was when I tested the ďrescueĒ function of the Spirit shortly after takeoff the heli significantly rolled and pitched away from level meaning the vibration during the 5 minute warmup caused it to drift.

I have a couple of chances to fix the rescue drift problem. First I havenít updated to the latest firmware which is reported to improve vibration resistance. Second I think if I reboot the electronics after warming up the engine and just before taking off it will help.

Unlike the maiden flight this time I forgot all about putting in ear plugs until I opened up the engine to lift off. Some excitement there as the heli was starting to tip a bit as I was running up the engine speed and about to switch to idle up. I had to quick jump to idle up 1 and do an emergency departure with nearly full collective; and it was very loud and exciting. I need to do some tweaking to my ďnormalĒ throttle and pitch curves. I think the gyro drift may have had an effect on the helis tendency to tip on the first takeoff.

One thing I noticed while flying around was this sound I could hear. It sounded like a tractor or something running nearby. Then I realized it was a choppa choppa sound from the rotor blades on the 700n. Just like a real helicopter! The 700n definitely has much more presence without the ear plugs!

One thing I forgot to mention was my choice of a 17 tooth pinion gear for a ratio of about 6.5 to 1. I read in a thread somewhere the author liked that ratio the best so that is why I chose it. Until I get more flight time, and some courage, to do some aggressive flying I wonít be able to tell how that is going to work out with a heavy load. So far it seems just fine.

Friday 3-13
I wasnít able to post until today because of the site maintenance but since last Monday I was watching a video of Bruce Jenner fly his 700 (wow is he a good pilot) and realized that deep blade sound is there in the video. After hearing a 700 fly in person I guess it was there all along I just never noticed it.
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Old 03-14-2015, 06:12 AM   #14 (permalink)
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Great thread I enjoyed the read, love the attention to detail, you've deinitely finished that model off to a high standard.

Have you considered fitting a different exhaust system? The standard zenoah can is supposed to one of the worst offenders on the ears, it's loud and raspy, there are some pipes out there which are quieter so you will be able to hear those 700 blades more
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Old 03-16-2015, 12:20 PM   #15 (permalink)
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Thank you very much for the compliment Varelco. I actually like the look of the stock exhaust and it's really not to loud for me. It is pointed down at the ground. On takeoff and landing you can really hear it though! Part of the fun. I feel like the Harley dudes that put straight pipes on although it's not nearly that loud.
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Old 03-16-2015, 01:39 PM   #16 (permalink)
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I didn't read the hole post . But make sure there is no slop in your main grips. This is very inporten when using the DFC head. If there is a lot of slop in the blade grips the vibration will brake the link. I found this out the hard way.
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Old 03-16-2015, 01:41 PM   #17 (permalink)
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Check out this post

https://www.helifreak.com/showthread.php?t=673036
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Old 03-16-2015, 02:46 PM   #18 (permalink)
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OK thanks. I'll keep an eye on the dampers. I've never seen as much play as we saw in the video.
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Old 03-16-2015, 04:10 PM   #19 (permalink)
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I had that much play in my head. After putting in the shims I have not had anymore problems with braking links.
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Old 03-17-2015, 10:10 AM   #20 (permalink)
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Quote:
Originally Posted by The Mechanic View Post
Thank you very much for the compliment Varelco. I actually like the look of the stock exhaust and it's really not to loud for me. It is pointed down at the ground. On takeoff and landing you can really hear it though! Part of the fun. I feel like the Harley dudes that put straight pipes on although it's not nearly that loud.
No problem, fair comment if you like it thats all that matters I have to admit its alot more discreet and lighter than other set ups.

What fuel tubing have you used? The black looks better than the yellow Tygon thats normally used.
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