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Heli-Log 4:13:2015

Posted 04-13-2015 at 04:01 PM by rcnut

April! Ah yes, the smell of spring and the birds chirping once again!

After the B-Ham fun fly, I went through some of my helis to prepare them for the next time out to the flying field. The Synergy, I removed the main needle valve and regulator. I disassembled both and used alcohol to thoroughly clean everything. I may have found some tiny bits of junk in the regulator sitting on the clean paper towel I was using.

The second Goblin gasser, I removed the factory tape and used the 3M gray tape. Hope this helps! The Rave just needs a test flight. Goblin gasser #1 needs a new blade link; it is slightly bent from that last auto. I would straighten it, but it is one of those specially made turn buckle links. I’m afraid if I do manage to straighten it, it would snap. So I placed an order for a couple of sets.

The Mostro build

I my last post, I mentioned I bought the Avant Mostro nitro heli. This was one of helis I was looking to try. I’ve seen the electric version fly and it looked awesome! I started the build the day before I left for the B-Ham fun fly…March 18th. I had the mono-plate assembled in no time what so ever. Mounting of the gears to the plate is straight forward. The top plate, that holds the servos, became the item of focus. You are given the servo pillars to install along with blocks that have brass bushings installed intended to hold the servo output shaft in place. This means the servo screw is replaced by a threaded pin.

The servo tab pillars are adjustable, on a slide, to accommodate any type of servo size. This is a novel idea, however, the two servos (pitch & aileron) closest to the mainshaft, don’t quite fit the hole spacing on the BK servos I bought at the B-Ham fun fly! And I couldn’t use the alignment pins (the new servo screw) they didn’t line-up to the brass bushings and bottom out up against the bushing.

Well, I continued on until I needed to install the servos, then I will tackle that problem. In the meantime…I sanded all the edges on the carbon fiber parts, and then proceeded to assemble the frame. This went fairly fast and then it was time to install the mono-plate to the frame. The fuel tank assembled like normal, and then it was time to build up the motor. Nothing special here…I needed to trim the fan shroud to fit the carb velocity stack and RPM pickup.

I mounted the landing gear, and then installed the motor, and fastened the fan shroud in place. Now it is time to build up the tail section. There really isn’t anything different, most of the assembly is done, except for greasing the thrust bearings. The instructions say to install the boom, but this is where I deviate from the manual. I wait until very last to install the boom. This way I’m not knocking everything off of my workbench, and it getting in the way…potential for unnecessary hanger rash.

So now it’s time to tackle those servos! The first thing I noticed is the mounting holes are drilled wider than the servo tab holes. And the center “V” block pulls the servos just enough off center to cause drag on the servo screw/pin. So I didn’t use those 2 pins, I did on the elevator however. The second problem I ran into, was the servo screw spacing from that brass bushing (for the pin)…it jammed the screw head into the bushing. So I needed to space the servo away from the bushing. And to make matters worse, with the servo being that close to the mainshaft, the geometry was noticeably off.

I started with the supplied spacers and found I needed 2 spacers per servo tab, or 4 spacers per servo. So I made some out of spare carbon fiber I have from my broken parts of other crashed helis. I try to recycle as much as I can. 2 mils is what “I” needed to make the servos work. The spacing was almost perfect and no contact with the brass bushings.

Now it’s time to route wires and mount the Spartan Vortex VX1n! The instructions state using heat shrink tubing, to help with chafing…well, I like to use the fuzzy side of Velcro. This works very well. I routed the wires towards the back and mounted the VX1n on the bottom plate of the mono-plate. I had to make two extension wires for the throttle and governor pickup sensor.

The LiPo sits up front, so I needed to make a long power wire to run from the front, to the back. I used 12 gauge wire. Now this is over kill, but I won’t have any voltage/power drops due to the length of wire. The frame has small holes for wire tying the servo wires along the length of the frame, this is a nice touch.

After all the electronics are mounted and the wires run and secured, it was time to make up the swashplate linkages and start the programming. This Mostro heli doesn’t sit flat like most helis, it sits crouched forward? I’m not sure as to why, but it made leveling the mainshaft a treat. I had to shim the front skids quite a bit! A couple of inches worth!

Once the mainshaft was leveled, the rest of the programming was normal. Now it was time to install the boom assembly. It went fairly quick and straight forward. But it was unusual to install the boom without the fuel tank installed. The boom mount clamps are directly under the tank. This will be interesting if I need to adjust the belt tension, will I need to remove the fuel tank? Or can I sneak around the tank? I haven’t looked into this just yet.

Back into the VX1n programming to setup the tail…easy and fast. The mounting the canopy; I’m not a big fan of thumb screws, so I chose to use the RCBooya pins…particularly the short Goblin style pins. I was going to remove the long screw for the thumb screw and use a much shorter screw, but the loctite was holding the screw in pretty well and I didn’t have a straight shot to the head…so I just cut the threads off where I needed it.

The canopy fit perfectly, as if it was pre-fitted at the factory. The tail end of the canopy is held to the boom by Velcro. Well, after the first flight, the Velcro lets go of one or both sides, so I made a long Velcro strap to hold the ends on. It works and doesn’t look too gaudy. So now it’s time for the maiden flight.

It took a bit to get the new O.S.105HZ to start, but it was purring like a kitten. I set it down on the ground and said to Mark, “Well this is it!” The Mostro lifted off the ground straight and true. The head speed was a bit low and I was happy with that. The whole flight was great, no surprises, and no bad habit/issues, just some programming adjustments as the motor gets closer to being broke in. However, and for some unknown reason, the Spartan Vortex decided to loose its programming as I powered it up for the second flight. That was the end of breaking/flying the Mostro, well, until I get the controller reprogrammed.

Once home, it was an easy task of reprogramming the controller, but I wrote down all the settings so if it should happen again, I will have a copy while I’m at the flying field. I did transfer my “chicken scratch” into an EXCEL spread sheet that looked much better and easier to follow.

The next outing (this last weekend, Saturday) time would tell if this controller will reset the settings back to the default settings. Well, it didn’t do that, instead I was able to get in 4 flights before I did a dumb thing! Yea…I make mistakes like everyone else, and boy it almost cost me a heli!

For flight #5, I used the “data pod” (an interface just for the Spartan Vortex) to make some tail gain adjustments, cyclic response adjustments, and some expo adjustments. Normally, this is no problem, however… When I unplugged the data pod and plugged the second LiPo supply in its place…I missed the top pin. On the Spartan Vortex, the servo, power pin, and data pod input pins are vertical. And there is 2 connectors (pins going horizontal) on the bottom of the controller.

So… I plugged the power wire/connector one pin off in which shorted the plus to the minus pin. And when I was ready to plug the LiPo into the controller, poof! The wires going to the controller started smoking and the insolation was melting. The two shorted pins started melting. And that’s when my brain kicked in and reached in to disconnect the “Deans” connector. But instead, I just yanked the burning wires and tossed away from me.

I didn’t get burnt, but quickly saved my heli from further disaster. At the time, I couldn’t figure out what happened and I was getting bummed with the thoughts of sending in a defective controller for repairs. It wasn’t until I was getting ready for bed when the little light bulb came on. I shorted the LiPo through the controller!!! I felt stupid once I figured it out. But life happens and we learn from it and move on.

Now to repair the damages! I opened the controller and discovered nothing happened inside! Cool!!! I cleaned/removed the “bad solder”, found some replacement pins (they are the standard header pins for printed circuit boards. You can buy them by the dozen), inserted the new pins, and soldered them in place. And for good measure…I measured the new pins for continuity, and to make sure the power pins were not solder shorted…by me!

I made a new two connector power cable (Spektrum/JR connector to Deans) and tried it out. The controller powered up like nothing ever happened. And to the controller, it didn’t know anything bad happened to it as it never powered up when the power was shorted. But I was making sure the unit worked without any other issues.

As for how this heli feels, there’s nothing special that “jumps” out at me. Of course I need to do some adjusting in the Vortex controller to make it more alive, but for now its tame while I work on breaking in the motor. It is weird not seeing the boom supports, but it disappears quickly. The big diameter boom somewhat looks like a Goblin boom, big and standing out. So far all of the five flights have been in sunny skies.

More to come as the motor breaks-in!
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