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Gasser Helicopters Gasser Specific Discussion |
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07-14-2014, 01:23 AM | #1 (permalink) |
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Trex 700N DFC Helibug Gasser completed
I have completed and maidened a new gasser. I started with a brand new Align 700N kit and a Helibug front mount conversion. The engine, a Hanson 290 3D max, the RX (an AR9020 with two Sats), BD3SX, and the GV-1 came from stripping down Whiplash.
I used the four servos in the kit for the cyclics and tail. I used one of my MKS BLS950's from my Whiplash for the throttle servo, maybe a little overkill. As has become my practice with the gassers, I mounted all the electronics in the rear to keep them away from the engine heat. The T700 does not really have a nice flat mounting area in the back for an FBL controller. I used two layers of 3M 4011 on either side of the center ridge to get a flat mounting surface. The kit came with two tail booms: a CF one and an aluminum one. I used the cf one. I used RC Booya quick release canopy mounts on the rear. These also came from my Whiplash. They stand out a little further than the stock mounts which turned out to be a good thing. With the stock mounts, the canopy was too narrow at the back for the RX and GV-1 mounted on the left rear side. The Booya mounts spread the canopy a little wider. I used some magnetic mounts on the front. Issues: I really only had two issues during assembly and both had to do with the clutch. The Helibug kit comes with the Lynx gasser clutch. This clutch is bigger in diameter than the Align clutch (I think by .2mm) and basically does not fit in the stock Align clutch bell. This has come up a few times in various threads. I had numerous emails with Helibug about this. They claim you can "just run the clutch in". I claim you can't. I put significant effort into working the clutch and bell together before assembly and then again after assembly. This included running the bell on the clutch mounted to the engine with a drill motor. After assembly I ran the engine and drove the main shaft with a drill motor to further "run in the clutch". In the end, I took the bell out and sanded it down like I did last year when I re-did the clutch on my T700N V2 gasser. I would have saved myself a lot of effort and wear and tear on the drive train, if I has just sanded the liner in the first place. In my opinion, Lynx should either make the clutch the same diameter as Align, or offer a thinner liner. This business of having to sand the liner should be corrected. Anyone who says they can just run in the clutch without sanding, I would like to see them do it. It actually poses a hazard to have such a tight clutch/liner combo. One could easily hurt themselves starting the engine without enough clutch/liner gap if the blades are mounted or even just the head. The other issue was the clutch and bell relative vertical positioning. On my initial assembly, the top of the clutch hit the inside bottom of the bell. There was no vertical clearance. I created the required clearance with 1mm washers between the engine and engine mounts. This photo shows the clutch and bell with enough clearance. Helibug claims there should be enough clearance inside the clutch without any washers. In my case, this was not true. There are a lot of parts that come into play in that stack-up: the engine height, the Helibug engine mounts, the clutch adapter, and/or the frame hole positions. Anyway, it is something to watch out for. I modified the canopy in several areas: on the left side near the heat deflector to let the hot air blow out better, near the throttle linkage, one spot neat the tail control rod, and a little on the left rear so I can see the Gv-1 display. The power on/off is just the EC3 connectors shown in the photos above. Power is supplied by a 2100mAh LiFe battery mounted in the front. I used a stock GV1 sensor operating off the flywheel magnet to produce the required RPM signal. It looks a little messy having glued the sensor to the frame with thick CA and then over coated with Black Ultra Permatex. I used this method on my older T700 gasser and it held up for a while now. Setup went smoothly. I copied my TX file and BD3SX file from my other T700 gasser and then went through the 3SX setup wizard just to check everything. I had to reverse the Throttle and I think one or two other servos. I ended up with good numbers on the servo limits. The maiden flight also went smoothly. I flew it twice for about 10 minutes each. After the second flight, I took the canopy off to see if the servos were hot from the engine. Everything seemed just barely warm so I think the heat issue is ok. Now that it has flown from 20 minutes, I will recheck all the screws to make sure all the Loctite worked or that I didn't miss putting Loctite somewhere (yes it has happened). Hopefully I will get lots of trouble free flights from this new gasser heli.
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This is your brain on helicopters! Trex 700L, Trex 700N DFC HB gasser,Trex 700N V2 HB gasser, Trex 550X. Spirit or BD3SX Last edited by rhodesengr; 07-15-2014 at 10:47 PM.. |
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07-14-2014, 10:57 AM | #2 (permalink) |
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frame brace pieces and throttle plate
Just one added note:
The Align DFC kit comes with frame stiffeners pieces that are supposed go in the lower frame corners. They are sold separately as: H7NB004XX These do not seem to be compatible with the Helibug conversion. Not sure if this is one of those Align version upgrades and HB is one step behind or HB just doesn't think they are necessary. The switch plate would probably interfere with the throttle servo plate but it would have been nice if the other three pieces has been useable. Speaking of the throttle servo plate, it is held to the frame by just one frame screw and one of the canopy mounts at only the back edge. The rest of the plate is just hanging in space. I noticed on both my 700N V2 conversion and this new one, that this cantilevered throttle plate tends to vibrate harshly at certain engine RPMs. To eliminate this vibration, I added a bead of black Ultra Permatex between the top edge of the throttle plate and the RX mounting piece. I am also considering dabbing some thin CA along the back and bottom edges. The throttle plate is designed to be adjustable but once you have it in a place that allows good throttle adjustment, you don't ever want it to move, or worse come loose. I have found that the front canopy mounts are subject to a beating in any sort of hard landing. Also the stock mounting screw is a 16mm set screw. It has to go through two frame sections so the amount of thread left is just barely enough to engage the canopy mount and the threaded rod inside frame. I made a 20mm long screw by cutting the head off a 3mmx20mm cap head screw,
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This is your brain on helicopters! Trex 700L, Trex 700N DFC HB gasser,Trex 700N V2 HB gasser, Trex 550X. Spirit or BD3SX |
07-15-2014, 01:03 PM | #3 (permalink) |
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That's looks terrific. Glad your maiden went well. I hope to re-maiden mine on Friday or over the weekend.
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07-17-2014, 10:42 AM | #4 (permalink) |
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Join Date: Nov 2010
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Nice work. Does it make any difference exactly where you mount the tachometer pickup around the flywheel housing? Are some areas thinner than others? Looks like the magnets are running down around the area of the black painted pull-starter housing? Or up more around the aluminum fan housing?
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07-17-2014, 10:56 AM | #5 (permalink) | |
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Quote:
I encourage you to simply remove the black plastic fan cover. It will be obvious why we use the particular location. There is really only one magnet and it is imbedded in a laminated core that is itself imbedded in the flywheel. What you see looking at the edge of the flywheel are the laminated core faces. To the sensor, core faces look like a North and South pole placed close together. If one was willing to do some machining, there are places inside the fan cover where you could mount the sensor. There is a big gap on the carb side and you could make a special bracket and mount the sensor very close to the flywheel and inside the fan cover.
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This is your brain on helicopters! Trex 700L, Trex 700N DFC HB gasser,Trex 700N V2 HB gasser, Trex 550X. Spirit or BD3SX |
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07-17-2014, 07:50 PM | #6 (permalink) |
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Looks terrific!!!
Great job!!! Good to see gassers moving forward after the demise of MA. Good Luck!!! Pete <:-}
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Blade: MSR, MSRX ,NANO, MCPX, 120SR, Compass Warp 360, Mikado Logo 500, 2 Whiplash Gassers, DX8 WARNING: Flying an RC Helicopter is addictive and may become hazardous to your Wealth! |
07-19-2014, 12:03 PM | #7 (permalink) |
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Nice I would love to see some flying videos
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07-19-2014, 12:21 PM | #8 (permalink) |
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Well maybe in a few weeks. My shiny new gasser is not so shiny anymore. I was flying it yesterday and the tail failed. I killed the engine and tried to auto down but it came down pretty hard and did a fair amount of damage. One of the landing struts broke so the bottom plate hit the ground. This jammed the engine upwards which bent the clutch bell and broke the side frame. I think the engine fan cover also was pushed up because it was hitting the flywheel.
Turns out the tail failed because the rear tail control rod pulled out of the ball link which is a pretty disappointing failure. With the tail servo and middle arm at 90 degrees, it seemed that rear rod was a little short so there was not enough ball link thread engagement. It has been suggested that I use Quick UK links which are longer so will have more thread engagement. Align kits seem hit or miss on where links end up on control rods. The rods on the elevator servo are completely turned in. It was difficult to get those rods short enough. Both tail rods seem to end up with the links only about half-way down. They seem too short so its hard to get them long enough and still have good thread engagement. The manual seems to indicate the CF rear control rod has an adjustable threaded end but the actual part in the kit does not seem to match the manual. It seems to be fixed length.
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This is your brain on helicopters! Trex 700L, Trex 700N DFC HB gasser,Trex 700N V2 HB gasser, Trex 550X. Spirit or BD3SX |
07-19-2014, 12:59 PM | #9 (permalink) |
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Starter?
Hi!
Thank´s for all your info, i´m building a 700n DFC gasser and i need useful hints in my build. I´m just about to mount my engine to the baseplate but i´ll have zero clearence to the ground. How did you solve this issue? Harri Suhonen |
07-19-2014, 01:11 PM | #10 (permalink) |
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Hi!
What starter method are you using? I´m having zero clearence to th ground with stock Zenoah recoil starter on my 700 dfc. Harri Suhonen |
07-19-2014, 05:40 PM | #12 (permalink) |
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Sorry to hear that.
I wonder if it is an Align issue or did HB change the servo location.
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07-19-2014, 06:50 PM | #13 (permalink) | |
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Quote:
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This is your brain on helicopters! Trex 700L, Trex 700N DFC HB gasser,Trex 700N V2 HB gasser, Trex 550X. Spirit or BD3SX |
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07-19-2014, 09:05 PM | #14 (permalink) |
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I suspected something like that, two friends build DFC 700 E's with no tail rod issues.
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Tom TRM Power CAUTION - my posts are based on my experiences, yours may be different. |
07-19-2014, 09:25 PM | #15 (permalink) |
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Sorry to hear about the tail issue and hard landing
I lost a tail blade today on my 300x im just so glad it was on the ground when flew apart and not in the air.
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07-20-2014, 02:01 AM | #16 (permalink) |
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Help me out, shall i forget about my recoil starter or what?
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07-20-2014, 10:15 AM | #17 (permalink) | |
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Quote:
Some people like the simplicity and purity of pull starting Others like the ease of electric starting. You might consider this: use electric start at first with a new engine until you get things tuned up and starting easy. Then go back to pull start. Starting is much easier once you get your idle speed and needles set.
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This is your brain on helicopters! Trex 700L, Trex 700N DFC HB gasser,Trex 700N V2 HB gasser, Trex 550X. Spirit or BD3SX |
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08-02-2014, 09:15 PM | #18 (permalink) |
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my engine shrunk
Well at least things are always interesting with gassers. In the previous episode, the tail control rod pulled out of the ball link which led to an emergency auto which led to assorted damage. Damage included deforming the lower crankcase on the engine. So it went off to Al C. who was fantastic as always. I put it all back together today and now I now longer need the 1mm washers as described above to create clearance in the clutch. The engine is a little shorter after repair than it was when I first built the DFC conversion. The engine was in a hard landing when it was in the Whip but I'd have thought that would make the clutch lower if anything. Anyway, now I get good clearance with no extra washers. Weird, huh?
I made both tail control rods effectively longer by using one Quick UK link on each. Using QUK links on both ends would have been too much. So now I have a lot more thread engagement on both tail control rod links. Hopefully we'll have no more pull-outs. I just have to check the swash level and pitch zero and should re-maiden n the morning.
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This is your brain on helicopters! Trex 700L, Trex 700N DFC HB gasser,Trex 700N V2 HB gasser, Trex 550X. Spirit or BD3SX |
08-04-2014, 08:13 AM | #19 (permalink) |
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if your having tail control rod issues after this, consider looking at synergy tail control rods and ends. you can cut the control rod to length, and JB weld the ends on. when putting the ends on, you can gain a little length there if you still need it too......cheap, easy, and extremely strong. no need for a dang rod to be pushed up in the center of the carbon control rod that will likely crack it and cause a failure itself.....
http://mattbotos.com/store/index.php...oducts_id=1741 http://mattbotos.com/store/index.php...oducts_id=1894
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08-04-2014, 10:54 AM | #20 (permalink) |
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Thanks for those ideas. That looks like it would certainly work. The Quick UK links gave me the extra length I needed.
I did re-maiden yesterday. After the flight, the tail gears seemed really noisy and it sounded like I had a bad bearing in the tail boom so I went home to examine. The only thing I found was the tail boom was a little bent from the previous hard landing. I put a new boom on but the gears still seem noisy. We've posted about this in other threads, the black gears being noisy. I guess I should just fly it some more and see how it goes.
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This is your brain on helicopters! Trex 700L, Trex 700N DFC HB gasser,Trex 700N V2 HB gasser, Trex 550X. Spirit or BD3SX |
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