| Crashes and broken parts |
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.:Crashes and Broken Parts:.
We thought it might be fun to show some of the crashes and component failures we've had since starting on this adventure. We'll put them into groups just to keep any one page from getting too long.
.:Crashes and Broken Parts:. These are the things that happen when we don't pay attention to the details, or we have one of those moments! Select a section in the drop down at the right to see that results of "good intentions". {styleboxop width=400px,float=left,color=maroon,textcolor=white,echo=no}Every time I fly, The Earth makes this big sucking sound... {/styleboxop} {mospagebreak_scroll heading=Introduction&title=Crashes} Crashes: 2006-07-10: I was given a Predator Max 90 for my birthday ( thanks honey!) in May of 2006. By early June I had secured all the radio gear, blades and other items to make if flyable. All ready to go, just waiting for some radio gear
We got the eCCPM setup pretty much finalized within a couple of weeks, and we were flying in a soccer field at the local park. The park is immediately behind our house, so its a very good place to go for testing.
A little side in practice at the park, now that I think about it, probably not the best place to fly a 90! We were wringing out some pitch and throttle curves when we had the first ISSUE
Wrapped up in the tree, waaaaaayy up there
I will never forget the noise it made as it hit the tree. It completely sheared off a branch almost 3" thick and trimmed through many other smaller branches like a weed eater. Aeryk did not think to hit the throttle hold or kill switches because at that time he thought the radio was in lock-out. It was only later we discovered the servo arm had popped off. As we got closer, we could tell that the engine was still running, so at that time Aeryk killed it using the kill switch on the transmitter. {styleboxop float=right,color=green,textcolor=black,echo=no}I will never forget the noise it made as it hit the tree. It completely sheared off a branch almost 3" thick and trimmed through many other smaller branches like a weed eater. ... {/styleboxop}
Cut this in just one whack! I can still remember the noise it made
Luckily a good friend had access to a bucket truck with a 55 foot reach. After getting permission to get the truck on the grass at the city park, the truck operator was able to retrieve the bent up Predator.
Heres the bucket truck, it's great to have friends !
The blades, head, mainshaft, spindle, tail boom torque tube, and radio tray were all destroyed. There were also several holes in the canopy from the impact with the tree branches. Closer inspection revealed the true cause, as well as some additional damage to one collective servo gear set.
Heres Aeryk with the broken heli and the branch it lopped off
After some $350 in parts, some excellent fiberglass work by my dad, and a fresh paint scheme, here is the Predator ready to fly again. oh, BTW the servo arm screws are loctited now, (and checked after each flight). Ready to fly again {mospagebreak_scroll title=Broken Stuff} Broken Parts: During our time building and flying RC planes and helicopters we have had many parts fail in various ways, so we thought it might be interesting and helpful to others to see the things that given up for one reason or the other. Feel free to email your own crashes and or broken parts and I will include them in the articles.
During the early days of flying the Predator, we had been working on getting things back to normal after the tree incident , and were flying at the local field. After one landing we noticed the tail fin was vibrating at a high frequency. since we had flown a couple of tanks through it that evening, and we were about finished for the day anyway we decided not to fly any more. I decided that I should check the tail over closely to try to locate the source of the vibration. When I disassembled the tail box, and removed the boom from the frames, I discovered that the boom had cracked in the front where the front transmission block attaches to the boom. Also the bearings that support the torque tube had slid out of the nylon holders and were rattling around on the torque tube. Cracked front boom mount due to vibration
I quickly checked the torque tube holders in the boom and found that they did not fit tight in the boom. I did a little research on RunRyder's Century forum and found that there are two sizes of booms, standard and heavy duty. They are the same OD but the heavy duty boom is thicker giving it a smaller ID. I also discovered that Century is now supplying the smaller mounts with all torque tubes and two different thicknesses of O-rings to fit whichever boom you had.
Check the fit of your torque tube nylon supports during assembly. Because the boom I had received in my crash kit (which came a a package including the boom and the torque tube) was a standard boom and was now damaged, I decided to order the heavy duty boom. Once the boom had arrived, I was able to use the smalled mounts and have them fit properly. Two things to pay attention to, use a tiny drop of CA to hold the center nylon sleeve in place on the torque tube, and install the whole torque tube into the boom using liquid dish soap. The soap will dry up in a few hours and hold the supports in place, but let them slide out when you need to service the bearings. Further inspection revealed that the tail rotor blades were probably too tight, which wouldn't allow them to center properly, causing the vibration. All the shaking more than likely caused the boom breakage. The support bearing mounts being too small, and all the extra vibration made the bearings come loose and float around in the boom.
2006-09-22: Recently, we had a tail gear box crack and almost separate from the helicopter. Look at the pictures below. One side had completely broken and the other was almost in two pieces. This happened at the IRCHA southwest fun fly after a 3D test flight. Luckily we caught it in a preflight check or it surely would have caused a crash.
 This is the standard tail box as supplied by Century
Very possibly the cause of this failure was the fact that only 3 tanks before we had replaced the tail rotor gear set with the speed up gear set. This has one additional tooth on the drive gear, which causes the tail rotors to turn about 9% faster that stock. The gears were quite a bit tighter than the stock set, but I had read that the notchy gears would wear in after a couple of flights, so I left them in that way and ran it . After a couple of tanks, the gears were noticeably better, but still to tight. I disassembled the tail box and decides that the only way to loosen the gear mesh was to remove a little material on the back of the driven gear where it butted up to the bearing on the rear side. By doing this I got the gears meshing very well. I cleaned the tail box halves, and installed them and the now happy gears, repacking the box with lithium grease. I didn't notice any cracks at this time but I wasn't looking specifically for anything like that, so they could have been there at this point from the tight runs on the gear. We did a single tank test flight to check things out, and packed up headed for IRCHA. One flight later was when we noticed the cracks. {styleboxop width=400px,float=left,color=green,textcolor=black,echo=no}Very possibly the cause of this failure was the fact that only 3 tanks before we had replaced the tail rotor gear set with the speed up gear set... The gears were quite a bit tighter than the stock set. {/styleboxop} We replaced the standard tail box with what Century calls an "Enhanced Tail Gear Box" part number HI6078S. It is only a couple of dollars more than the standard duty one, and it seems quite a bit stronger with three ribs in the area that flexes from the left-right load from the tail rotor forces. Were keeping a close watch on the problem area, and if it shows any signs of cracking we'll bite the bullet and buy the all metal tail gear box.
Heres the standard and the "Enhanced" tail box compared,
2006-10-15: We had a strange combination of problems this Sunday, Friday the 13th has got nothing on Sunday the 15th. Aeryk was flying the 2nd tank of the day doing some pretty aggressive 3D getting lower and lower, getting more and more confident. We have been working on getting the Predator to be more responsive and he has been flying it more extremely, with lots of flips, tic-tocs, funnels, and a lot of tail stop piros . He really likes the new tail gears. Between the gear change and the tail rotor servo that Futaba replaced, it has cured the tail falling out on hurricanes and fast backward flight. Well about half way through the second tank of fuel, during a flip we heard a WHACK, like a blade had hit something. Aeryk quickly flipped back over to normal attitude, the engine was sounding kinda strange, but seemed to still be running more or less ok. He quickly landed and throttled back. As we looked things over, we noticed a large nick in the leading edge of one blade. Whatever had hit the blade and made the nick had also split the leading edge of the blade for about 2 inches. DAMN another nice set of CY Radix 710s damaged.  Leading edge of Radix 710 damaged by a broken 3mm bolt As we looked things over we discovered that one of the bolts that hold the boom supports to the rear fin was missing. Turing the nicked blade to a spot directly over the boom we found that the nick was in perfect alignment with the missing bolt. 
Broken boom support bolt, fell out and hit the blade of course I had checked tightness on both boom bolts earlier that morning before heading out to the field. Apparently the stress on those bolts, and the forces flexing the boom itself are MUCH larger than I realized. The faster tail gears along with the more radical flips and tail stop maneuvers really stress those bolts I guess. With one bold missing and the clamp loose to slide on the boom, I can easily flex the boom quite a bit. I guess we'll have to upgrade to a larger bolt size here, and really keep an eye on it. I came across this Predator flown by John Parker at the 3DM with two sets of boom supports,  Dual boom supports, the only set I've seen but looks like a good idea so it seems like someone has experienced this problem before and corrected it by doubling the number of supports. (I'll look into that soon). Black Sunday ??? So... carrying the heli back, I noticed that the swashplate had separated. The top bushing surrounding the ball had come up and out. There was a tiny super thin ring of aluminum that had separated from the upper (rotating) portion of the swashplate allowing the ball to push the top bushing upward. I had also looked this over quite carefully, and lubricated the bearing and ball the night before flying.
This too had come apart in flight. and again, luckily it had not caused a crash. Aeryk said that he had noticed the lower ring on the swash wobbling around last time it was on the ground, but didn't think anything of it. I'll have to impress upon him the need for paying attention to those things ! Century Customer service replaced the seperated swashplate with one of a different design. It does not have the outer ring. Supposedly is has be re-designed to eliminate the problem. Heres the new design, Century replaced the one above No-Charge,
During the initial flight of My Hawk-Pro we had a loss of tail control and quickly set the heli down:. With about ½ tank remaining, and at about 5 feet of altitude, the tail started a slow pirouette to the left. Aeryk gave a little right rudder to correct and the heli spun even harder to the left, so he quickly set it down. When we checked we discovered the tail was no longer being driven. I suspected a setscrew had come loose, but further inspection showed that all the setscrews were still tight. I removed the tail boom from the frame, and then disassembled the tail box. Once I slipped the torque tube out of the boom I found the problem. The front drive end had come loose and was just spinning on the tube.
This end was loose and slipping, When I looked closely, it looked like there was just a tiny amount of adhesive used to join the two, and there was no cross pin through both pieces like there is on the predators. I decided I would cross pin the drive end of the torque tube for a more positive attachment. I happened to have a broken torque tube with the cross drilled end from a unfortunate crash last summer with my Predator. So I decided to use that end and the small pin that was with it . I pressed the pin out of the broken end off the Predator, and heated it up. The end easily slipped free from the 2" remnant of the tube from the Predator. After roughing up the inside of the end and the outer surface of the tube, I cleaned both pieces thoroughly with lacquer thinner. Mixed up some JB-Weld, applied it to both pieces, and slipped them together, making sure they were seated all the way in. Then I headed off to the drill press and cross drilled the complete assembly with a 2mm bit using the existing holes in the drive end as a guide. I tapped the small steel pin into the hole making sure it was seated evenly . I'm pretty sure that the JB-Weld alone would have been enough to hold things together, it pretty amazing stuff, but I happened to have the other end and a pin, so I installed it just to be sure. I can't remember seeing any posts online about Hawks Pros torque tube ends failing, so I guess I just got a poorly assembled one. Luckily it didn't cause a crash!
More to come I'm sure...
{mospagebreak_scroll title=Just More Pictures}
Here are some pictures, no crashes, or other difficulties. This is how things work most of the time!
Click to enlarge the images...
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with the heli. In my profound wisdom I had forgotten to loctite the screws that attach the servo arms. I'm used to nylon gears and nylon arms, so the thought of needing to use loctite on the servo arms never occurred to me. Well Aeryk was in a nice tight right hand roll when the collective servo arm on the right had side popped off its splines. This left the heli in a continuous corkscrew heading away from us at about 40 mph. Aeryk was screaming I don't have it, I don't have it, as it flew away for about 100 feet. Luckily it hit near the top of a tall tree right behind our house.
