Category Archives: Helicopters

Helicopters, Radio Control

HobbyKing HK-T500 First Look

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Part of my latest toy delivery was a slightly larger heli than I’ve worked on before. Not wanting to get too far into this before I learned something about the 500’s, I purchases a basic intro kit.

The current plan is to build this kit, screws up, put together a full parts list and get a good estimate of what a real flying 500 will cost to build, with common spares, electronics, batteries etc.

So, onto the kit.

First, this kit arrived in a box smaller than my EXI-450 did. The way the packed the stuff in there was really something else. Here is what the array of parts look like once unpacked:

Hobby King HK-T500 Helicopter Kit

So, just exactly how large is the main frame? Pretty big.

Closer look at the 500 class alloy frame

Comparison to a fully assembled 450 behind it.

Alloy frame and once piece landing skids. 450 Heli sits in background.

Landing gear is a one piece plastic affair. Checking the parts list on the higher-end HK-500GT shows that it uses a multi-piece gear assembly, more in line with 450 kit I have. A detraction, but one that can be solved with the purchase of a 500GT landing gear set (about $5.00).

Once piece plastic skids in T500 kit.

Main rotor bearing block is plastic. I had a small issue on the plastic bearing block in my 450, and ended up replacing them with alloy. Checking parts I see that HobbyKing does sell an alloy block for the GT version, however it very clearly states that it DOES NOT fit the T500 model! That could be a major issue ongoing. When they say that it does not fit, I don’t know if that refers to locating pins only, or if the overall dimensions are different enough to prevent use.

T500's plastic main bearing block.

The kit does arrive with a set of fiberglass main rotor blades (black / yellow). As you can see, these are not just a little larger than those of a 450 (middle) and more than twice the size of a 250 (bottom, shown for effect). These blades are not only big, but they are heavy! Fiberglass 450 blades I’m using come in at 18.5g each. These bruisers weighed in at 68.6g!

Rotor blades, 500, 450 and 250 class.

Main gear set seems serviceable. Operation seems fairly smooth. The trail drive gear is a little wobbly, but that’s been the case on every gearset I’ve seen so far, including a factory Align unit. I’ll take it apart and re-oil the one-way bearing. I did notice that it has not ‘fan blade’ properties to move air like some of the other 450 gearsets I’ve purchased.

Main gear set.

Tail boom, servo link, boom support rods and flybar are all in the next package. The tail boom support struts appear to be plastic with plastic ends. Tail boom is typical aluminum alloy. Flybar appears to be stainless steel and quite rugged.

Tail boom parts package.

Servo link ends are plastic, but it does not look quite like the quality ball end links typically found in kits. Maybe it’s just the size of them.

Closer inspection of boom parts.

Boom holder and tail gear set is a festival of plastic, right down to the cross tube/spacers that screws anchor into. Even on the cheapest of kits I’ve seen so far, that was metal (talking about the 4 bars near photo center). Is it ‘bad’, I don’t know, but I’d prefer to have seen some more metal in there, that’s for sure!

Tail drive gear box.

Assembly looks pretty straight forward. Which is good, since they clone kits do not come with any sort of instructions. All the parts fit snug, and turn freely. The screws in the tail kit are allen-drive, but they are on the soft side. While test fitting the parts, without even torquing them down, one of the heads stripped out, requiring the application of a small vice-grip pliers to remove it. If it had been snugged down, it would have been a much more difficult task. I’m considering a trip to Tacoma Screw for a set of torx-drive replacements

Tail drive gear box with gears and bearings test fitted.

The tail and tail boom fastening components are all in the next bag:

Tail drive and boom fastening parts.

Tail gearbox, blade holders and pitch actuator arms are plastic. Bearbox is nearly completely enclosed, so I’m not able to see the tail drive pully gear, but it also appears to by a white nylon/plastic.

Tail rotor drive and gearbox detail.

Knight head, tail rotor fin and tail servo holder are made of metal alloy. Tail boom yoke and servo boom holders are black plastic material.

A lot of stamped alloy parts in this bag.

Probably the most important part of all, the main rotor head. One word comes to mind; PLASTIC!. Lots of it. First the overall shot:

Main rotor head assembly.

Main head, it’s a beast. 132mm across (grip to grip) it’s 33% larger than the same part of a 450. And, aside from the feathering shaft and bearings, it’s all plastic. Having broken a plastic blade grip on a 450 recently, a similar crash might crack the entire fly head on this bad boy.

Main rotor blade grip and feathering assembly.

Swash plate on this is part composite, part alloy. Linkages seems appropriately constructed on the head and swash. Pictures can be worth a few hundred words, so here is the picture.

Main rotor head, swash plate detail.

Another of the links, washout arms and tracking links.

Main rotor head details.

Flybar paddles. Plastic. I’m not sure what the deal is with the vents, and the pack of decals. Based on what I’ve seen on other photos, the decals are applied to the blades to cover the ‘vents’. Perhaps those are simply there to lighten the paddles, and the decals cover the holes to make the paddles work. I’ll have to look into this further.

Flybar paddles and decals.

Anti-rotation bracket and canopy stays. Also….. (wait for it….. waaiiiiiiiiit). Plastic.
[PIC 20]

One last package of stuff. Hardware, blade holders and two different sized pairs of hook-and-loop straps. Also in the bag are two sizes of velcro adhesive pads, two bags of extra fastening hardware, servo horn accessories, balls and a pair of monster motor pinions. Of note in this bag, is also a bottle of purple 222 thread lock. I already have a monster bottle that I have used on all my kits. I just find it interesting because just about everyone is using the heavier duty blue which I’m certain is the WRONG type. Having more than a passing background in auto and motorcycle repair, you need to use the right locker for the right size fasteners. Blue (242) is really for much larger hardware. Purple (222) is the right stuff for small fasteners. Now I have a little validation (beyond what the TRex assembly manuals show) with the inclusion of 222 Purple in the kit. Good to know!

Last general hardware parts bag, revealed.

Last is the canopy. And it’s BIG. The canopy stay holes also need to be enlarged to work with the supplied (white this time) rubber bushings. That is one of the first things I’m going to do, since I want to design at moderately nice looking canopy design for this monster.

It would be harder to send a cheaper canopy! It’s simple resin, like EXI-450 kit supplies, but in this case it does not have even have the ‘cockpit’ canopy detail on it. It’s just… all white. I put a spare 450 canopy in front, and my coffee mug in the photo to give some scale.

T500 and 450 canopy scale comparison.

So, there you have it. Unpacking the HobbyKing HK-T500 electric R/C helicopter kit.

Helicopters, Radio Control

Building new micro helicopter – N250HKA

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Just arrived!!!

HobbyKing 250 GT Helicopter Kit

My latest toy box (or box of toys) arrived during the conference this week. I’ve had a lot of time to work on building this machine, but I did manage to get some HXT-900 cyclic servers and a general test/fix mockup completed. ! I still have to order several parts before it will fly.

  • 250 / 300 class ourunner motor (400 won’t fit.. bummer)
  • Micro head locking gyro
  • Digital tail servo
  • DSM2 compatible receiver.
Helicopters, Radio Control

N450V2A – post crash repairs underway

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Bent tail boom after crash
Repairs are underway, following my flight yesterday, where I ran out of altitude. Breaking things is seldom enjoyable.

But it’s the risk you have to take if you’re going to fly these things, especially when there are gusty winds. There are plenty of YouTube videos showing real helicopters having trouble with wind, sometimes with tragic results. I

In the grand scheme of things, a little bit of bent aluminum is hardly much to worry about. Being grounded with a busted helicopter is still not the ideal situation.

I noted yesterday that the Blade 400 tail tube turns out to be remarkably similar in dimension to the one used on the 450. I really would have thought that the ‘smaller’ 400 class model would have a shorter tail boom, but it turns out to be about 15mm longer.

Comparison of Blade 400 tube (top) and EXI-450 tube (bent)

Easy enough to rectify. A little cutting, sanding and filing is all it took.

The new tail boom, and new Sport alloy tail case are now installed on the helicopter. One of the advantages of the new Sport tail case, is an alignment pin (the original did not have, it uses the hole seen in the blade 400 tube) that keeps the tail case from rotating. An issue I had a couple of times with the original part.

New tail boom installed.

A closer look at the alloy tail case, new tail rotor blades also installed:

New alloy sport tail case.

During lunch I’ll be able to finish mounting the tail servo, knight head and support bars.

UPDATE:
I just checked on the status of the replacement parts and some other fun stuff I ordered from China, using the ‘slow-boat 7-45 day shipping’ option. I regretted not spending the extra $20 for faster EMS 3-5 day shipping, until I checked the shipping status this morning!

For a slow boat from China (OK, it’s air post but the website said expect 7-45 days transit), it’s already here in the states. I just needs to clear customs. Not sure who long that will take but, you know I’m going to post here when it does!

Slow boat from China my ***! 🙂

Helicopters, Radio Control, travel

Bummer day, turns good, then great.

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Some days are just not meant to be. That’s the conclusion I had at noon today.

The day started out innocent enough. The 4:30 AM sun woke me up, I only managed to make it to 6:00AM before I was ‘awake’.

Work day started at 6:30AM. At this point things were pretty good. No overnight issues (there really area, I have a great IT team working for me!), fired up my data modeling software and continued laying out some concepts for our IT off-site next week. It should be good and productive.

Weather was warm, a little gusty, but so warm, I just had to go fly the helicopter. Fresh from a makeover, and confident after 2 full flying sessions with no issues and crashes, I set out for the Sheridan Airpark at 10:00AM.

With the opportunity to practice some flying with perpendicular and quartering side winds, I set to flying (sadly the on board video camera was accidentally set to audio only.. on well).

The flying was going very well. Had full control, heli was still climbing and settling at odd frequencies.. maybe the motor was OK, ESC was OK, it’s just got this tendency to drop from time to time. Better throttle management required by me.

After doing some fast forward runs, then backing up, and running again, my confidence was building. Had a few gusts push the bird around a bit but I was having a blast. Then.. I got cocky.

Pulling pitch hard a couple of times, it was accelerating up nicely. Up down.. fast. I was starting to really fly it around, then I got behind the curve and started to get close to a fence than I wanted. Cutting back the throttle, also reduced pitch, and the bird started to roll left. Applied hard right cyclic, pulled out some more pitch and tried to flare for a landing when, it happened. Tail Strike. Drove the tail into the ground, stalling the tail rotor. This immediately whipped the heli around hard into a ball in the grass. I thought for certain by the sound, I’d shunted the main blades.

Must to my surprise, and happiness they were completely in tact! So was the very frigile, but very critical flybar. “Sweet.”, I thought, “Flip it upright and fly again. Hm.. uh.. wow.. that looks funny… OH NO!”.

Of all the spare parts I have, a tail boom is not one of them. Now, mine looked like this:

That tail boom doesn't look right.
. I had blocked out and hour from work to fly, the sun was shining, I was ahead of my personal work schedule, but.. I’d also personally put my bird out of commission for an undetermined amount of time.

Suddenly this pretty darn good day is looking less rosy. Ugh.. I just wanted a little fun flying time and my exuberance got the best of me, and the helicopter. Having been to my local hobby shop SO MANY times in the last month, I knew they did not carry the TRex 450 tail booms in stock. I’d had the forethought to order a spare boom with some other parts direct from a plant in China. But that shipment is 2-3 weeks out!! No way am I going to be happy not flying for 2 or more weeks. 🙁

Back to work, I’d got take care of that and another errand at lunch time. This damage has to wait.

Bent boom, broken bracket, twisted boom support.

Around 12:30PM I took lunch. One of the errands I wanted to dispatch today was to sell off my HK-45 Tactical pistol. It was stolen when I left California in 2000. Recovered from a drug dealer in Sacramento a couple of years later. It was found under the front seat of his car when they searched it. There it sat in evidence for another 3 years during his trial. Once it was done, the Sheriff’s department shipped it to the S.O. here in Kitsap (Washington) were I went to pick it up. It’s been mostly untouched since that time. I’ve always had a bad feeling that it was involved in some very unsavory/evil activity. I’ve never shot it. It’s been stored for years. Taking up valuable space in the safe, collecting dust, and as it turns out, rust too. 🙁

So, today I decided to sell it, and took it to a firearms dealer I’ve worked with before to see what they would offer. When I got there, the ‘head guy’ was out. A couple of his workers, enthusiastic, but not knowledgeable about the H&K made an offer that was just way too low. They did suggest I come back later, as the ‘head guy’ might be personally interested in the H&K. Now double disheartened, headed home to complete my work day, looking out the windows at the great day slowly passing by me.

Around 4:30PM, I’d put in a solid day of work, and I needed to go do *something* positive to cheer me up. Weather was so nice, I didn’t care what it would be. So the first order of business was to wash the SUV. I’d washed the car the weekend prior, but the SUV has been dirty since my last trip to CA. Filthy! So.. today it got some TLC and I felt a little better after that.

I’m one of those hope springs eternal type guys, so I packed up the gun again, went to the shop to see if the head-honcho was there, and in fact he was. After some examination he made me an offer 50% higher than his employees did, and I took the deal. It was more than I’d actually expected, so I was happy with that. Suddenly the day was starting to look a heck of a lot better!

A pile of cash in hand, I thought I’d now try my luck at the hobby shop. Worst case, I enjoy a nice drive around the water and back. As it turns out, they do not have the Trex 450 tail boom I needed. No matter, I know that I can drive the 70 miles to Olympia to a big helicopter parts shop and get anything I need.

It was at this point the day improve a bit more. I noticed that another brand of helicopter (EFlight Blade 400) had a nearly identical tail boom for their Blade 400. A smaller helicopter, but.. the boom looked so close, I might be able to use it. And after some measuring, it turns out the diameter is identical, the it’s not only long enough, but TOO long. But that I can fix with a hack saw! Best part, is they sell them in a pack of two for $6.00. 🙂 Ah… I might be flying again today yet! After digging around a little more I found some factory TRex tail boom support parts (also damaged in crash), so I was just about 100% whole, with the exception of a tiny plastic saddle part that the booms attach too. Eventually I found those as well, but only as part of a knight head and tail kit. Parts that I have PLENTY off, and these are white (gag). OH well.. I know how many days it will take to get just the part I want, and drive 70 miles for a part I can get now for $5.00 is just not really practical. So.. I have some more fugly parts for the tail, but I *can* fly! Provided I do the work to replace the parts that is!

High from my great encounter with a Glock specialist at the gun shop, and now the parts I needed for the helicopter, I started the journey home. On the way I looked for a new patio chair. Something to sit out front, read, enjoy a cocktail.. just take in the summer. But I didn’t find exactly what I’m looking for. Close, but I’m going to hold out for the ‘right’ thing. That quest continues.

Without the ‘perfect’ chair to sit outside on, I opted instead to go home, pick up my book about Bob Hoover, and head to the waterfront for a German sausage and a 9lb. Porter. It had cooled to just 90F at this point, so sitting in the shade by the fountain, drinking a great beer, reading a great book and having a great sausage, it REALLY made the rest of the day just about perfect!

Once I finished up, handed the plate and glass back to Amber, I decided to walk further down the boardwalk, find a table and keep reading. And that’s what I did until 10:00PM, when it was starting to get too dark to read.

It really was a MOST enjoyable day in the PNW. If only to have a couple of old friends to have been able to share it with. Well, friends, this is the best I can offer, until next we break bread.

Helicopters, Radio Control

N450V2A – new motor and new POV camera installed

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Big box of spare parts!
.
It has been a busy couple of days for the little bird. A big box of spares arrived this week, and along with those spares came a new mini DVR for on-board footage, and an upgraded motor.

In the upper left is a full CNC allow sport rotor assembly.

On it’s right is a new CNC allow tail rotor case and grips.

Far right in the photo are three sets of main shafts. It’s important that the main shaft be as true as possible.

Below the sport head are two different styles of flybar paddles. EIX factory paddles and TRex clone paddles.

Just to the right of those are two pairs of tail rotor blades.

The four allow bits just above the blades and paddles are new main bearings and carriers. The main bearings in the kit are housed in plastic. They are also the source of my head wobble issues, that I recently solved.

Heading right again are variety of pinions, 11T, 12T and 13T. These are important to establishing the proper head speed for a given gearset, motor and battery combination.

The large blue blob near the center is the new motor (another photo of that follows).

Right of the motor is a full spare plastic TRex factory head and grip set.

Below those are a set of Version 1 feathering shafts, and 2 sets of V2 shafts.

New motor installed (right).

You can see the physical size of the two motors differs quite a bit. The new one also has a built in air circulation van on the base of the body. After flying 3 packs I found that it was cool to the touch. Big change from the Alpha 400 (on the left) that it replaced. This new one includes an addition set of windings, and a higher power output.
One little caveat I did not know about the original Alpha400 motor, was that it’s spindle shaft is more in line with an aircraft (3.0mm) and not a 450-class helicopter (3.17mm). The new pinions I have actually fit the new motor properly. I think this will help with some of the odd modulation in the flybar and cyclic harmonic it’s been suffering from since I put it together.

Modified POV 18gram camera

New parts are all well and good, but new toys are even better. This one is a light (18grams) self-contained mini DVR (digital video recorder). It will record up to 2 hours of video on a 4GB micro-SD card. This thing is pretty tiny.

It does have one drawback though, the form factor is a major pain the butt to afix to a helicopter, or an airplane for that matter. The normal location of the CCD is on the ‘back’ (or front, you decide) of the case. What would have been nice is if the CCD was at the ‘top’ or, if lying flat, on its’ front.

So, I cut the case on a spare, tilted the CCD forward and secured it with the same type of foam taped used at the factor to secure it in the position I didn’t link.

Modified camera mounted on Helicopter.
Having made that modification, it allowed me mount the camera ‘flat’ and still provide a forward view.

It’s mounted inside the bottom of the main canopy. There was a blister already in the canopy that appeared to be perfectly suited to this installation. I simply had to cut an opening at the front of the canopy, use some hook-and-loop tape on the bottom and it was a go.


Here is a video clip I shot today, with the camera mounted in that position:

Helicopters, Radio Control, YouTube

N450V2A – Hover Testing

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Finally, it was time to see if this thing would fly. And, if I can fly it!

This outing was my best yet! 3 full packs flown, no crashes, no rotor strikes, and only 1 really hard landing! I (of course) shot some video and uploaded it to my YouTube bucket.

Not never exciting to watch, it was pretty exciting to get it off the ground without flying back into it out of control! This is pretty fun stuff! Plus the gear-head part of me really loves all the micro-mechanical parts and seeing how they function together and make it fly!

Helicopters, Radio Control

N450V2A Overhaul – Completed

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Tonight, I’m picking up where I left off yesterday [LINK], while I listen to some awesome local High School Radio (KNHC).

Sunday nights from 6PM -> Midnight is Industrial and Alt music show called ‘On the Edge‘. Reminds me of a similar show that used too broadcast on KFJC out of Foothill College in the Bay Area. Most of my good German Industrial music collection was the direct result of hearing it on that show.

Back to the Overhaul
I’ve been doing some research today on blade balancing. Picked up a couple of new tricks, talked to a few of the local experts and I’ve come up with what I feel is a comprehensive, but not exhaustive (aka anal retentive) balancing strategy. Here is my take on this VERY IMPORTANT task:

First off, getting some good tracking tape has proven to be a major challenge for me. Today I solved that problem, thanks to advice of a local flyer. He’s been using Monokote (I’m quite familiar with the heat-shrink version of it, having first used it almost 30 years ago). I picked up a high-vis red and contrasting orange in the adhesive backed variety.

Preparing to balance blades.

I don’t plan to balance the other 4 sets of blades I have tonight, just the set I’ll be using for the final run-ups once I have the bird back together.

The first step in balancing, is to find the COG (Center of Gravity) on each blade. I did this by rolling each blade on top of a spare flybar rod (it’s about 3mm in diameter) until I found the balance point. Once I did that I marked it with a permanent marker. This is done for both blades. The purpose of this is to determine how much balance weight you need to add to get the blades balanced our along each blade itself. Ideally you take the lighter of the two blades (if you have a scale that’s easier to determine, otherwise your normal blade balancing fixture will tell this tail), apply weight in the right locations to get both blades to have the exact same COG. I’ve done this already, the top blade has a little clear plastic tape used to weight it on the right side. Here the COG’s are in the same location on both blades.

Locating the center of gravity on each blade

Next I’m going to take equal pieces of the adhesive backed monokote, and apply a different color to the tips of each blade. Make sure the size of the monokote you apply to each is identical. They must also be applied in identical locations. Here is what it should look like *before* performing the final balance.

Adding contrasting blade tip colors. Critical to setting blade tracking

Next, set up the balancing rig and dynamically balance out the blades. Any weight, if required should be added to the light blade at it’s COG (which is why it’s marked across the pitch). Even though these blades are very close in overall balance, one blade does need a little bit more, to fully balance it out.

Blades on jig for balancing.

Once balanced, I moved back to the process of rebuilding the head. I had a lot of experience with the V2 head, but not the older Version 1 head that I had to buy parts for (no V2 parts available locally or online from the plethora of vendors, odd really). Interwebs to the rescue! I found an original ALIGN 450SE (v1) build manual with the exploded view of the V1 head!

ALIGN 450SE (version 1) exploded head view. (click image to enlarge)

Somewhere in the box of parts is the main head, and all it’s associated bearings.

Box of 450 class helicopter parts

The most important bag today, the main rotor head and blade grip components

There are a lot of parts that go into the grips alone! That’s 6 bearings, 2 spacers, 2 washers and 2 bolts, not to mention the 4 o-rings (dampners) and the feathering shaft itself (already installed in head).
Layout of all the parts required to assemble the upper rotor head. Look at all those bearings!

Having the instructions made assembly straight forward and quick. It took longer to write this pragraph and take the photo, than it did to put together, install, locktite and tighten the grips. They seem very firm and turn very smoothly. A HUGE improvement over what I was attempting with the hybrid V2 guts and V1 components. I knew better, but I wanted to see how close I could get. Not close enough. At any rate, here it is, assembled.

Blade grips installed. This is a partially assembled main rotor head top-end.

The next step is to attach the rest of the upper head’s running gear. The flybar seesaw holder was a little problematic. Gunk in the bushings had it binding up. Finally resorting to application of some firearms cleaning techniques (and fluids) cleared up the gunk. Re-application of all locktites was of course required after being exposed to solvents. Added a little CLP to the bushings to keep the running smooth. Pitch arms were next and those when back together without drama. This is what I have now;

This is a fully assembled main rotor head top-end.

It was finally time to bolt the head to main shaft, insert flybar, line up the washout shafts and block, hook up swash coupling links and get ready to finish the top-end rebuild of this bird.

Upper, middle and lower sections of main rotor head assembled and installed. Swash Plate is that beast of link buttons on the bottom.

While upgrading parts, I decided to swap out the temporary Blade 300 flybar paddles (smaller, top) for the larger genuine ALIGN 450 parts. They are basically twice as thick, have actual airfoils and weight 8.8g, compared to the Blade 400 units which are 2.7g. The orginal EXI flybar blades come in at 4.7g. I tossed them out. One was not factory drilled for the flybar, so I just sorta hogged it out during original construction. Turns out that alignment of that bore is really important to the overall flight characteristics of the bird! They are gone, just in case I forget why they are no longer in use, and put them on something. I’m better off with the flimsy B400 paddles than one that is not drilled properly. Many lessons in these little things.

Temporary parts (top) vs. the right parts (bottom). Flybar paddles are critical to all Bell-Hiller head aircraft.

Installed, centered, measured, re-measured, checked for square, re-measured down to .001″ inch. with dial calipers. I’m sure how to get it any more accurately constructed than this! With the blades installed, it’s time to perform the first run-up and blade tracking test. Really, about 9 hours of work comes down to the this moment of truth. Fixed, same or (gulp) worse?

Assembled and ready for ground tests. Stand by for....

This video contains the first run-up, before blade tracking was adjusted. Next was post-tracking adjustment. Overall vibration has been reduced significantly! With the replaced bearings and slightly slower head speed the entire things sounds healthier too. Another view in the video displays the blade tracking, and finally a fully assembled bird is run up to 3/4 throttle. A test of the throttle cut and auto-rotation flare action is also examined for function.

Everything looks great and ready for another test flight! Local time on the Pacific Coast here is 23:07. A little too late for test flights. The plan is to give it some air time after work tomorrow.

One other thing I noticed, was that flybar action is much smoother since I completely tore down the head and rebuilt it.

The upside of all this, is that I’m 100% confident I can repair any damage done during a crash, including a full frame up-reconstruction. At some point this fall I’ll probably swap out the metal frame for a V2 carbon fiber setup (about $30). That will drop quite a bit of weight off, and going to a CF tail boom will also shed some weight. The less the entire thing weighs, the less power it will use to remain aloft, which equates to lower operating temperatures for bearings, and longer flight times with the same batteries.

Now, I rest.

Helicopters, Radio Control, Uncategorized

Model Helicopter Blade Balancing – preliminary research

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Since I was not 100% certain of the proper method of blade balancing, I’ve started up this page. You see, until 9:00AM this morning I was certain how to properly balance blades. However, after reading the ALIGN Trex450SE instructions, which contain this diagram, I’m not at all certain.

Blade Balancing instructions from the ALIGN Trex Instructions.

Up until now, I had placed the blades trailing edges flat on a table, then tightened the balancing tool, and placed it on the jig. The objective was to have the trailing edges of the blades perfectly level. Here is what it looks like:

My orginal blade balancing method.

I hope you can see the difference in how I placed the blades together, compared to to what the Align manual suggests. Here is a closeup to help illustrate how I used to do this:
Closeup of my balancing method.

Compare this to using the ALIGN documented method:

Using the ALIGN balancing method.

As you can see here, not only does it appear quite different, so is the result! Using this method, my blades are out of balance. Or, are they?

ALIGN balancing method

Now, I’ve gone out and searched and consulted with the great oracles on this subject (the R/C discussion groups) and found the following:

On one of the most helpful sites I’ve found on the web, Mikey demonstrates the blade balancing using the same method, that seemed intuitive to me. Here is a screen shot from the video:

One balance method seen online.

Checking another forum, I found the following this post that discusses first locating the COG (Center of Gravity) on the blades and marking them. Or balancing the COG on the blades so they are the same blade-to-blade, THEN getting them in dynamic balance:
http://www.rcgroups.com/forums/showthread.php?t=878885&highlight=blade+balancing

Hm. there seems to be MUCH more to getting a really great balance on your blades than meets the eye! With the vibration issues I’ve been happening, I’m going to do everything I can to provide as stable a main blade balance as possible.

What is most clear at the point, is that I have A LOT more reading to do. PART 2 will follow once I decide on exactly how I will be balancing my blades. The question of the afix orientation of the blades perists, even after I find the COG of the blades.

This link here looks to be the most concise explaination of a balancing method. [LINK]

Helicopters, Radio Control, Uncategorized

N450V2A Overhaul – Day 1

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I’ve had a few good flights, and few bad flights with the N450V2A. After locating a nasty wobble and some incorrectly manufactured parts, I’ve torn the bird down to just about the bare bones and have started a re-construction.

Starting here with this picture, I have already performed the following.

Replaced the Main bearings in the main bearing blocks. One of the old bearings had a bit of a ‘notchiness’ to it so I tracked down some replacement parts, including two pairs of original Align factory main bearings (5x11x5mm). $6.49.

Old EXI main bearings (red) and new Align main bearings (nude)

They are installed at the top of the frame, and in middle, just above the main gearset (in blue). The main gearset has already been replaced with at genuine factory Align part AGNH1218 $22.99

Mainshaft and main gearset.

The original Pentium 30A ESC (Electronic Speed Control) was showing signs of overloading and causing in-flight resets! In defense of HobbyWing, it looks like I was running too steep a pinion on the main motor (I’ll get to that later). Regardless, I wanted to make SURE I did not have to learn auto-rotation landing in my first few weeks of flying. So I purchased a new genuine Align 35A ESC with Governor, PN 35ABLESC GOVMD5VBEC RCE-BL $53.99. It’s installed high on the frame now, where the battery would normally be located. I did this to help ensure good air flow along it’s heat sink.

New ALIGN 35ABLESC GOVMd5vBEC RCE-BL Speed Controller

As mentioned, it turns out the that original 13T pinon which came with the EXceedRC Alpha 400 63N18 motor is not an appropriate selection. It was suggest that I run either an 11T or 12T pinion by several people online. The local hobby shop had a pretty knowledgeable flyer behind the counter, and suggest a 12T would make a big difference. It’s also the suggested pinion for the factory Align Trec450 V2 (of which mine is a clone). Having already ordered an 11T pinion, I purchased the 12T. Original 13T is on the right, new 12T Align part on the left:

Main drive pinions. New 12T ALIGN part (left) and original ExceedRC 13T part I'm replacing, on the right.

The motor itself might be OK. I’m going to re-use it for now. Another is on the way from Hobbypartz.com price about $20.00. The pinion is only firmly mounted on the shaft, since it will have to be precisely adjusted for main gear engagement once I re-install the motor in the frame.

Motor re-mounted and gear mesh very carefully set.

Next I went about trying to get the main bearings and main shaft running as true and consistent as possible. The bottom bearing has some manufactured in lateral play, nothing I can do about that. But I did manage to snug up the shaft to bearing interface with some very light knurling of the main shaft where it contacts the lower bearing. Additional play looks like it will come out with a slight ‘cocking’ of the upper bearing. Just enough to produce a natural tendancy to run straight. I have plenty of bearings now. One of my next objectives will be to take the extra bearings I have to an expert bearing distributor and see if a higher-quality bearing is available in the same dimensions.

Mainshaft re-installed for the umteenth time.

After all that work, the main shaft finally looks like it’s running true. The dial indicator is still picking up some movement, but it’s about 1/2 or perhaps less than it was originally. I think I managed to take at least a little play out of the main drive system, and that makes very hopeful for some major flight improvements.

Rechecking main shaft runout.

Taking all these parts off, I think it wise to re-check the swash plate level, just in case it something got bent, twisted or otherwise tweaked. Placed the 450 swash leveling took on the plate, and it was dead on! I ordered the tool from XHeli.com (it’s an EXI too) for around $3.50. Well worth the investment. When I checked my ‘by eye’ leveling with the tool I found I was pretty far out. Sure it’s a fair bit more labor to tear down the head to use the tool, but having such a core component as close to perfect spec as humanly possible seems like a wise use of one’s time. Maybe it’s not, but I did it.

Carefully re-checking swash plate angle with swash fixure.

Having conquered my fears of the main shaft, time to rebuild the rotor head from the swash pate up. First thing I want to tackle is the top of the head, sort of going in reverse order. It turns out my latest blade grip purchase, to replace the broken grip, wss of the WRONG PART. My model is a Version 2, and the parts I got, unbeknown to me, were Version 1. Barely close, certainly not the cigar. Now today I did pick up a full compliment of Version 1 parts. Combined with the plastic Version 1 head ($7.99) and 2 pairs of grips($13.99) from the other day, I should be able to assemble a very tight and very functional main rotor head. My ideal scenario would be to re-use the original allow EXI head (left) instead of the new Align plastic Version 1 head (right).

Main Rotor head types. EXI Version 2 (left) and ALIGN Version 1 (right).

It turns out the the V1 head (right) and the alloy V2 original head (left) are identical in width, and the ID of the feathering shaft ($7.99 for three) holes are also identical. The only difference (beyond material) is a more pronounced shoulder in the V1 head. Fit wise though, they tested out (to the best of my abilities) the same! This is very encouraging! All I need to do now is figure out how the V1 head systems is supposed to go together!

Confirmation of compatibility. Rebuild is a GO!

It’s about 1:00AM now. No need to work all night on this thing. I’ll pick this another day, maybe tomorrow, maybe I’ll go ride a motorcycle instead.

Helicopters, Radio Control, Uncategorized, Video Gaming

POV Camera mounted on EXI-450A

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Wednesday was a pretty good day. It marked the arrival of a mini-DVR camera I’ve wanted to buy for quite some time. It went on sale for Fathers day at nearly 1/2 price. I just could not pass up the deal!

Mini DVR Camera

The location of the aperture is not perfect, but I can work with it. In fact I have a new canopy on the way from Hong Kong, that will be cut so I can mount the camera forward of main rotor head, and a little lower to make sure it’s not at risk of a blade strike. In the mean time I have a mount position rear of the main rotor that works OK. I like to have a little bit of the helicopter in view to give some perspective.

Here is an in-door run-up test of the camera.

Having found a suitable location, and even though I’ve still not sorted out the mystery vibration in the main drive train, I wanted to take it out for a flight, and shoot some POV video off the helicopter.

Here is the POV video:

Unfortunately, this was the aftermath of the crash. Broken main blade grip. That really annoying part is that this one of those 2% of the parts that is NOT directly ALIGHN TRex 450 compatible.

EXI-450A V2 main blade grip failure. Good grip (top) broken (middle). Also in photo are the various bearings used by main grips.

I’m able to source ALIGN 450 parts at the LHS (local hobby shop), but these design of these are so different that I don’t think I can use them. The bearings are the same size but they mount in different locations, and I think it’s allowing the blade grips to shift a few thousandths of an inch off-center, making what I know to already to be a nasty run-out on the main shaft, even worse. I’m fairly certain that it’s not an issue with the shaft itself, since I have 4 of them now (1 original and 3 replacements) and they are all showing the same runout when mounted in the drive system (video below shows the problem I am having).

You may notice wobble in the in-flight POV video. That’s not the camera. That’s actually the helicopter when it gets into this harmonic resonance with the main shaft vibration. It can be pretty nasty, and it certaily didn’t help me when I lost control and crashed.

I’m doing some research, consulting with the great oracles, and just trying to sort out the possible cause of the strange shaft run-out. So far, I’ve come across the solution, or solved this problem myself. Here is a video of the some testing I’ve done to quantify the issue: