Rototerrier's TREX 700 Helibug RC Gasser Conversion Build

[Rototerrier]

I normally don't do build threads Because this kit is fairly new, I think any interested in or current assembling this kit, will benefit from it.




The kit arrived and the frames looked perfect.

• Just like with the normal 700 kit, I started by sanding the side frames to take off those extremely sharp edges.
• I mounted the align frame supports to the helibug engine mounting plate
• Assemble the stack. The final product is perfect, but there are a few points to mention here.
  • The threads on the bell side of the pinion were not 100% to the end. The threads themselves were fine, they just didn't go all the way to the end. This caused me to have to force it onto the bell which shaved off a micro thin hair of aluminum all the way down. We are talking micro micro thin and nothing to be concerned about. But, I would have liked the threads to be perfect. The other side was perfect and would thread on just fine. I even tested that side on the bell and it threaded as well. So my bell was fine, it was definitely the threads that were off.
  • The first of the 2 main bearings was an extremely tight fit. I had to pull out a deep well socket that just fit around the shaft and sat directly on the inner race, and hammer it down. I fear when it's time to replace that bearing I will probably be buying a new pinion. There is not really enough clearance to get a bearing puller behind the bearing.
  • Finally, when installing the hex head onto the top of the starter shaft, I was unable to set it all the way down where is wants to be. There are 2 intentions on the shaft for the hex set screws to settle in to. I made mine sit up about 1 mm higher. When all the way down it would cause just a little too much pressure on the bearings and make things a little bound up. I only installed it for support. I won't be using it for starting so I don't think this is a major issue.

• Install the Align bearings into the side frames. I used a little bit of CA glue to secure them in place.
  • This was not a perfect drop in. The pre cut holes were not nearly big enough to accept the bearing. I used a tapered grind stone bit from my dremel kit to open the holes up. You can see the required depth from the fiber build up on the stone. Also, do not attempt this with the Dremel itself, the speed is way too fast. Use a drill.

• Install the nose and new helibug throttle servo bracket

• At this point I went ahead and installed the main bearings, clutch stack, main gear and head assembly. I did all of this just to see if everything was going to mate up. PERFECT! The mesh as spot on!

• I lengthened the tail servo push rod. Because I had previously used the new quickuk / rocket city links, I have plenty of room to expand. These links were pretty much bottomed out to work with the stock frame. This helibug frame is just a tad longer and requires a slightly longer rod. You can see the length difference here in these photos.
  • I used some high quality heat shrink to take up the gaps between the links and carbon rod. This makes a very tight fit and should work. I didn't want to hunt down a new carbon rod, but might do so in the future. For now, this makes a solid connection and should continue to ward off vibrations.

• Modify the frames to accomodate the Align Governor Sensor and my JR switch. I used the stock frame as a template to line up my holes and slots.

[Rototerrier]

Here is my first video...EVER. We got a little Canon compact camera for christmas and decided to give it a whirl this morning. We did 1 video zoomed way out and my wife was able to get everything in the frame but it was small. Then we did one zoomed in, which is what I am posting. I am flying my my culdesac and it is very tight. I am not a stick banging 3d flyer but I can throw it around a bit and sport fly pretty good. In this tight area I couldn't really do much. I will try to get some better videos in some open fields.

Point is, most videos I see of gassers are of people just hovering around and just tooling around. I can fly much much harder than this. Just wanted to give everyone a taste of what I am going to try to accomplish with this gasser, and video it of course.

[cbergen]

Quite a bit of smoke for a gasser....

[satsuma]

Wow, smokey, how much oil in the gas are you using

[Rototerrier]

• Installing all of the servos is a little tricky. The stock frame has 2 scews going into the plastic nose and 2 more going into a plastic back plate. Well, this frame does not accomodate any of that. I did a little dremal work to make the existing triangular back plates lay flat and I used some old trex 500 plates cut in half for the rest. I needed a total of 4 extra back plates to mount all the servos. If you don't have any extra parts laying around, this could stop your build cold.

• I now moved on to installing the engine to the motor mount. The holes are way to small for the supplied mounting screws. I was able to very easily open them up with a 3/16 rat tail file. Once I was able to force the file through the holes, that was sufficient to get the mounting screws through.

• Install the hub and clutch. Yet another hickup. The Hanson engine did not come with a M6 x 22L bolt for mounting the hub. I had to make a quick run to Ace Hardware to get one. No biggie, I have one about 3 miles from home.
  • This hub is not the same as the one shown on the helibug website. Notice the shaft on the zenoah engine is tapered. Sticking with how most everyone is now doing hubs, this is a no fuss install. No dial indicating. I have to say I prefer this new design and I am sure everyone else will also.

• I put everything else together. But, I got hung up on the throttle. The arm is keyed and will only lock into 2 positions, both of which were completly unusable by the throttle servo. I had to take the dremel to it and open it up on 2 sides so that I could move the arm where it would work better. This was a pain but worked out well once complete.

• Finally just wrapped up with everything else. I will post more photos of the complete heli with Century V2 Slim Torpedo tomorrow. I am also going to redo the fuel lines.

• A few notes about mounting the canopy. I had to move the rear mount holes forward about 3mm. The stock position puts a lot of pressure on the canopy.
• With the Century V2 Torpedo Slim, there is not enough room for the front canopy mount. Installed, it sat about 1 hair from touching the pipe. I shaved off about 3mm from the base of the mount to get it close to the frame and then cut off the tip. This allows the canopy to slip over, and since it is so close to the pipe, once all the other mounts are hooked it cannot come loose. This worked very well for me.

[Rototerrier]

Preliminary Conclusion and initial flight report

In its current form, this is not a completely drop in conversion. With just a few minor tweaks, it could be. Everything will go together perfectly, but you have to accomodate for a few things along the way.

For me, this kit would be 100% perfect if:
1) Include a back plates for mounting all the servos
2) Include the 2 stock holes for the align governor.
3) Include the stock slots for power switches like the stock frames.
4) Engine mount and frame bearing holes were the perfect sizes.
5) And I don't know if the M6X22L bolt is supposed to come with the engine or not. I would think it should have, but If not, maybe including one of these just in case. It cost me a quarter.

It is very important to keep in mind that even with these very minor issues, I was able to fully complete this project, AND FLY IT, in a day. Not too bad.

Flight Report

Perfect, absolutely Perfect! No vibrations, no weird noises, and the main gear was silky smooth. The clutch and bell lines up perfectly.

I will fly it a LOT tomorrow and will report back. It was starting to get late when I finally got it in the air and was only able to run about a half tank through it.

Simply wonderful in the air! I am very impressed.

[Rototerrier]

Flew a bit this morning and was finally able to get the engine tuned with the new century v2 slim pipe. Getting the canopy to fit was a chore. I will post more on that later.

I am not sure the Align governor is going to work. I am using a X9303 utilizing the governor channel. I set the governor to 2% and it had a decent low headspeed. Set it to 3% and HS increases A LOT. Too much actually. The HS would not even be safe to fly with. I immedately switched back to normal. Tried a couple times and had same results. I have set the governor up correctly, being sure to use a 0-100 linear curve to set the endpoints. The difference of 1% is crazy! And my v curve on Idle 1 is good. I flew that curve with the governor off and did some flips and rolls and they are good.

If anyone has any suggestions on how to make it work, I am listening. Apparently the GV1 seems to be the popular governor for gassers. Unless someone has any suggestions, I will have to be on the lookout for a new gov...Maybe. The curves actually flew pretty well. Will just have to see how it goes as I start banging it a little harder.

[Rototerrier]

I flew a lot today and have to say it flies great. I finally started to run up the headspeed and throw it around a little. On my last flight of the day I started to hear some ticking. At first I thought it was just the engine crackling a little since it is still on the rich side. After coming out of a loop, losing all power, and having to do a really quick nose in auto..I discover the gear has stripped. Look familiar?




I was able to get in some nice pyro flips, funnels, and walls. It was a blast.

Not sure what the solution to this is going to be.

[gramey]

It's nice that it flies so well but just a couple of quick questions, one for you and one for Ali if he reads this, how much back lash did you have in the main gear and secondly what is Ali's recommendation on how much there should be?
One more quick point for anyone reading this, with regard to mounting the servo's I found this to be a pain as well but I did mine slightly differently, I ordered the T Rex 600 servo mounts, carbon front plate and plastic rear lugs. I'm just lazy and couldn't be bothered with cutting bits to fit here and there.

[Rototerrier]

The mesh can't really be adjusted. Personally, I thought the mesh and backlash was perfect. After speaking with Ali, I am going to order the KDE gear. And good idea on the 600 mounting back plates.

Also, Ali doesn't recommend it...but after just spending $37 on a KDE gear, I am going to try one of the Align mod1 gears as well. They are 16 bucks for 2. It think it's worth a try.

[Ace2Be]

Rototerrier: Nice write up!

[Rototerrier]

I updated the last portion to include the final notes about the canopy and century slim pipe.

[pgkevet]

Originally Posted by Rototerrier

If anyone has any suggestions on how to make it work,

..depends how the align sensor works. Does it just use one magnet pole and the other magnet to balance or need both N & S?... If just needs one pole then fit both magnets the needed pole up and try working the gov sensing double the true RPM?.. Option would be to mount a second pair of magnets if both N&S needed.

Whether it'll work like that would be experiment ..but gassers run around just a tad more than half a nitro engine rpm

[Rototerrier]

Since I currently run that gov on my YS91SR at around 75 (x9303 gov menu), I would think anywhere in the 20-30 range would work for this engine. A buddy of mine suggested I might try aligning the sensor to the engine case to pick up on its magnets. Is it possible that the engine magnets are strong enough to be interfering wth the align bell magnets? I am going to experiment with this just to see. Oh, and to answer your question, yes it is just a single pole that makes it work. You have to be very careful to get them flipped when installing. I have always followed the finless described technique of sticking them together and marking the outsides with a sharpie and then just pointing both colors up to ensure I get it right.

Edit: My curiosity got the best of me. I just went out and removed the sensor and placed it against the case and sure enough, it registers properly on the engine magnet through the case. I am not sure the results will be any different, but at least I know the sensor will pick up.

[pgkevet]

it registers properly on the engine magnet through the case. I am not sure the results will be any different, but at least I know the sensor will pick up.

It won't help you.. same rpm there as on the clutch bell (unless its slipping :-)).. I'd be interested if you try my idea of two magnets with the same correct pole to see if that works though..

[Rototerrier]

I just pulled out the setup manual on the governor. It says an engine speed of 12400 is 50% gain. The sensor is monitoring engine RPM only. The bell is turning at the same speed as the engine and therefor there should be nothing more needed to make this work. The gain settings in the governor manual clearly states that it can go as far down as 10500 rpm. I still think it's interference between the align magnets and the engine. There is just nothing to support the fact that this won't work properly.

I think what I am first going to test is putting the sensor back over the bell and with the engine running, I will slowly engage the clutch and see if the light cycles as it should. When I move it by hand with everything off, it does cycle as the magnet passes under. But, if when the engine is running, I do not get the cycle then I might get somewhere.

[pgkevet]

Just a thought but I recall when I setup my 600N with the align gov that there were different settings for different tx's..mine wasn't listed and I had to play around the guesstimate numbers wuith a tach to get it right. You sure you don't have any of the silly things we all do like d/r or expo set on the gain channel or negative figures?

[Rototerrier]

Positive. In fact, right out of the gate I didn't touch a thing but lower the gain. This was converted from my Nitro 700 which was working flawlessly. That's why I was able to convert so quickly. Everything was already set up and working. I had to make very few adjustments. I reset several times and even went as far as turning off the built in governor menu and using the ATV endpoints of the gear channel directly. Same results.

Edit: Just went out and tested the sensor in both positions. Both positions made the light flash. And I slowly spooled the clutch up and the light did flash. Took it up above 30% throttle and hit the governor and it would just go wide open. Sense against the case or over the bell magnets. Makes no sense. Unless someone with experience getting this align gov working on a gasser comments, I am going to say it won't work. I officially give up on it.

[pgkevet]

Yet another thought...many folk use the 'malorie' linkage on gassers since gasser curves are different.. the malorie linkage where servo arm is 90deg to closed throttle and vice versa suposedly gives a more linear curve in the tx...perhaps that would help the align gov cope when hunting to adjust stuff?

[Rototerrier]

So, from a quick search I was get a pretty good idea of what the "malorie" linkage is doing.

The basic idea is to offset the servo arm position so that it spends more time in the lower position. Essentially emulating an exponential curve, but mechanically. I am also assuming that doing this would allow you to pretty much run a 0-100 linear curve in the radio. I will mess around with this and see what I come up with. Thanks