HDX500se Up

The Blade 300 bearings I needed for the tail on the HDX came in today, and just as I expected, the new design is two closed ball bearings (the Blade 300 4x8x3) and a thrust bearing from a 450 main grip, on each side, just like a main grip. Went together fine, tight on with free rotation. I doubt this 4 mm shaft will ever bend.

 

I spun everything up without blades and things looked good. Put the tail blades on and still sweet, minimal vibration. Put the main blades on, and took her to 90%. Noticed that a servo twitched, the one I didn't replace before, the aileron servo. So I replaced it, and things look pretty good now. Perfect tracking.

 

I learned how to use the continuity mode on my multimeter and checked the continuity on my tail boom to motor mount static buster and the continuity is great (thanks psylence519 for the suggestion). For good measure I lubed the tube again.

 

So... now I just need some nice weather and a chance to fly!

 

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HDX500: Yeah... its always something

On isolating vibrations troubleshooting the brown out and jittery servo problem, I found out the tail blade hub had a bent feathering shaft.

 

Parts for the HDX500se/Lepton are hard to come by. CNChelicopter carries many of the parts, so I went there and bought the last tail hub, and for good measure a couple of tail shafts (mine remains unbent).

 

Well, its not quite the same. The original (bottom smaller one) has a one stage 3mm shaft and is shorter. It uses 2-3x8x3 ball bearings on each side.

 

The new one is on top. It has a first stage that's 4mm for the ball bearings, then steps down to 3mm for thrust bearings. This arrangement is usually seen on the main rotor, I've not seen in on the tail, but the bigger the heli it makes sense. I will need 2-4x8x3 bearings on each side, and thrust bearings. I have the latter on hand, for a 450 main rotor crash stock. This will be assembled like a mini main rotor.

 

I checked with my usual bearing provider (Avid) and they are out, so I Googled and found another of my favorite sellers has them (WOWHobbies), for the Blade 300 I think. Correct bearing, comes 3 to a pack, of course, so I had to order two packs, about $6 a pop.

 

Now I wait. I expect this to go together just fine. At least that's what I tell myself. Still waiting for the HURC programming card and the back up Hobbywing ESC/BEC if that doesn't work.

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Zapping static gremlins

In discussing my recent travails with the electrical gremlins in my HDX500 on Helifreak, Slyster offered up the notion of static discharges being responsible. This makes sense and I had given it some thought the first time I dealt with this a couple of years ago. That's when I started spraying the tail tube with lube. Random electrical parts getting zapped, and often affecting the servos, for the most part this seemed in retrospect to solve the problem. But it still happened though rarely, and as I noted zapped a servo recently. Maybe routinely spraying the tube with silicone is not enough; others have describe sparks despite the lube.

 

So I decided to up the game. I don't want to spend $50 on two G-force static wicks. So I grounded the tail boom, which acts like a van de graaf generator, hence the static problem, to the motor block using descriptions others posted on the web. Now the boom is essentially grounded to the battery (truly grounding it directly to the battery would require another wire to the neg lead of the battery, but for all intents and purposes its grounded).

 

Here you can see the entire grounding run from the screw in the tail boom peeking out on the right to where it snakes under the gyro platform and out the forward side to a bolt, then over to the top bearing block, and then down to the motor block where it ends on the aft motor bolt.

 

The metal boom is painted blocking conduction, and the block on the tail is aluminum, which is conductive. I drilled a small hole in the boom and set a screw just into the metal (avoiding the belt inside). The copper wire is wound around the screw and a dot of solder secures it. The wire runs under the gyro platform.

 

and comes up the other side. The first segment ends here, where I sanded the frame (so it also grounds to the frame) and attached the wire, the screw set into the aluminum head block. If I had planned this better I might have run one wire with spots of insulation removed to expose the wire, but, meh. So I start another wire there and ran another segment under the top bearing block...

 

and down inside the frame to come out and end attached to a motor block bolt, grounding the tail to the motor.

 

 

Hopefully this will cage the gremlins and I won't have to revist the magicla electrical mystery tour with random electrical failures!

 

UPDATE (3/13/13): I realized that I had put the screw on the boom in a place where the belt has made its turn and is in danger of rubbing. Psylence on Helifreak also pointed this out, and it convinced me to move it, so today I moved the tap to the top and out of the way of the belt. Cut a steel servo screw very short.

 

 

 

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It always starts small...

And by the time you are done you've nearly disassembled the whole thing and spent hours solving a problem you didn't know you had when you started.

 

I took the HDX 500 down from the wall to see if the failsafe was set properly, after reading a couple of posts on HeliFreak. I noticed that the throttle stuttered just before mid-throttle. I am not sure, but think I have seen this before with this heli. I decided to change the ESC out for a HURC 60A opto ESC I have. I remember this HURC ESC because it works fine on my planks, but I wasn't able to program it with my Hobbywing programming card, like I can other HURC ESCs. I also am not sure I didn't recently fry my Hobbywing card... So I ordered a HURC card and its in the mail.

 

I set up the heli as it was, knowing that not having a soft start without blades wasn't a big issue, and the stutter step was gone. And then I noticed the twitching servos... I have had this problem before on the HDX and have never really sorted it out. I would change a part of the electrical harness and it would go away. This time it was the pitch servo. It was somehow shorting out the entire system, causing the other servos to twitch and browning out the receiver. It took me a day to isolate it this time. Needless to say I also have a 60A ESC-SBEC and a new receiver coming because I wasn't sure if they were the problem as I troubleshot it. I am now waiting for the HURC programming card, and if I can't program the HURC 60A I will swap the ESC and BEC out for the one coming in the mail and hope I didn't burn out the Hobbywing card.

 

Along the way I found out the tail rotor had a bent feathering "shaft" and needed to be replaced. It was subtle in flight but very obvious on examination. I was isolating any vibrations I could find. So those parts are coming.

 

As for the extra receiver... maybe I will build that HK600 or Winrc 600 after all. Wouldn't want a perfectly good receiver go to waste, now would I?

 

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Rolling Gear and Nacelles Back In Business

I finished up the nacelles, and they look so much better further forward. As I described, I lengthened the wheelbase.

 

Initial installation

 

Current Installation

 

 

 

Sweet!

 

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EXI 450 FBL Repaired

Yesterday I had some issues with the EXI 450 FBL that resulted in a fractured swash follower arm and a displaced aileron ball link.

 

Today I replaced both swash arms (they have to be the same size and aren't exactly standard, so to keep them the same I had to salvage two spares and replace them). I fixed the displaced ball link, and removed the blades. I test spun the system and found that the main shaft was bent. I replaced it. I also checked the feathering shaft, since a bent main often means a bent feathering shaft, but it was fine. So I cleaned up the bearings and re-greased them, put everything back together. New balanced blades put on, re-zeroed the pitch (whenever I do anything to the rotor head I always recheck the swash. I find that when I make sure both blades are zero at zero pitch I never have to fuss with the blades being off in tracking). Set her up for test spin, everything sweet, tracking fine, balanced and vibration free.

 

I still don't know for sure if the follower arm failed first or I crashed it through pilot error (I am still a beginner heli pilot, after all), but things were going just fine until they weren't.

 

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At least I flew something...

30 degrees today, but a light breeze and crystal clear skies. There was no way I wasn't going to fly something. I was a little worried about plastic brittleness in the cold, as I had seen others run into these problems. I was right to be worried, but at least it didn't hurt much.

 

Wingmasters has changed their keys at the first of the year, but since I am only going to be here for a couple of months I didn't want to go to the trouble to get a key or pay for a year. I had found a place to fly behind Kettering Junior High School in Kettering, Ohio. School is out this being a Saturday, so I knew it would be safe. As I drove up, I saw A guy named Joe who was flying a couple of micro foamies (and doing a pretty good job too!).

 

I took the EXI450 FBL up first. hovered her for a few seconds, and the tail kicked over a couple of times uncommanded, but she settled down and I walked and hovered out to the field from the parking lot and took her around for a few circuits and figure eights. I began a turn in and she suddenly stopped flying and dropped as I hit Hold. inspection revealed one of the swash follower arms snapped off at its weak point where it Y's onto the swash arm of the FBL head. The aileron ball link on the servo also popped off. One blade delaminated when it hit the ground. I haven't checked the servos yet, tomorrow's project.

 

 

The upper line points to the swash arm, and the lower one to the ball link.

 

 

 

 

Video of the flight. Sorry the heli is so far away...

 

 

I put her away and brought out the HK500cmt. This would be her first flight since I put the rolling gear on, and I was curious how that would go. On setting her up I found that despite having rebound her when I reset up the servos and the BeastX when I updated the Airware on my DX8 (in the update you have to rebind and reset all the servos...). So I rebound her, and then had to reset the throttle limits. Spun her up, and she spun herself down. No power... These are all fresh batteries. When I got home I found the cells were all down to 3.84v. Put a fresh set on and she powered up fine. The BeastX was doing some odd things, but they seemed manageable. On flipping into flight mode from normal she pulled hard right and I had to put in and hold a bit of left aileron. When I brought her down, set her down and flipped out of flight mode, she pushed over to the right and then left, a blade struck, and the tail blades touched. The plastic tail blades snapped off clean at the hubs... cold had made them brittle so instead of chipping they snapped clean off.

 

 

 

 

One of the things I noticed was that the gear were leveraging and twisting against the frame, and it had come loose, making the frame dip down in front. I decided to remove the gear, and thought about putting the skids back on, but opted instead to rotate them forward increasing the wheelbase, and set them up with another wood block this time attaching the gear so that the attachment point is behind the nylon gear, and a second wood bar is in front absorbing the forward leverage forces. I attached a wire tie to this to further stabilize it. I had replaced the base of the frame since the previously repaired landing gear supports had worn and broken and were not repairable. This time I bolted the gear to the frame instead of using wood servo screws I had used previously. This is solid.

 

 

 

 

 

 

 

I have to rework the nacelles, and this work isn't done. I have to refinish them having refit them to the now forward sweeping struts. I hope this works out as I rather like them.

 

Joe, if you read this, it was a pleasure to meet you and I should have given you my email address. Hope you grow into the hobby!

 

Addendum 2/23/13: I read up, and the BeastX, and likely any MEMS based gyro, can operate at cold temps. The key is giving it plenty of time to acclimate. I took the HK500cmt out this afternoon and I think did not give it enough time. It turned on lift off, the tail jerked a couple time, then turn in a slow roll and pirouette out of control. Hit hold, only lost the main blades. Stupid is as stupid does. Tomorrow I may try again, but allow it to sit for half an hour.

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