ODIN FBL with 7HV Head and KBDD EE 112mm Tail Blades

[Ah Clem]

More old geezer flying:

[ame]http://youtu.be/b7LnWhOlshY[/ame]

Sorry it is up so high for much of the flight.

Thank you to my friends TailBender, who shot the video and Danny Mattox, who spotted for me.
(how both managed to stay awake while I flew out an entire tank of fuel is beyond me-I was sure I heard snoring at one point).

The 7HV head with TracX Delrin drive tubes works great on the Odin. I would still like a bit more main blade to tail boom clearance, but it is better than the way some machines come from the factory.

The Odin is very locked in and quick with the BeastX on it (even with Radix "Stick Banger FB blades on it). The tail control with the KBDD EE Tail Blades is superb!

[pete best]

I am getting ready to do this conversion myself. After a couple of months, do you have any suggestions on things you would do or not do for someone doing the conversion? Are you using the Odin main shaft or the 7hv?

Thanks,
Greg

[Ah Clem]

The shaft is a cut down 7HV shaft. It is only slightly longer than the Odin main shaft.

The determining factor for the shaft length was the distance of the main blade tips to the tail boom. That is also why I used TracX 600 sized Delrin Drive Tubes, as they are the longest ones that Compass makes.

This is an outstanding flying helicopter, by the way.

[skunkworx]

Haha...you should let me have a crack at it next time I'll trade you a flight on my newest edition

[Ah Clem]

Mr. Worx,

That can be arranged, sir!

[ronstancil]

I have put the RJX 700 head on my Odin, and it works great with the stock main shaft - it is a bit lower to the boom (3/8 inch) than the stock FB head, but I have no boom strikes since the conversion - Mikado Blue Fullsize Vbar

it is my Favorite Nitro Heli. Folks have marveled at the power.

Does anyone have a Clutch bell and bolts they are willing to part with?

http://www.rjxhobby.com/en/pro_detail.asp?id=1424

[pete best]

So I got a few test flights today with this upgrade. I am using the stock odin main shaft. I got insane ground resonance when landing. It almost ate itself alive. I raised the head up using the lower bolt hole, lengthened my delrin rods out, and tried it again. Same result. More broken links and bent twisted metal. I gave up and went home.

Anyone have any thoughts?

[Ah Clem]

How high is the head from the helicopter frame? I know you raised it, but I wonder how close our two machines, are..

Mine had the ground resonance issue when it was flybarred.

I have not experienced it since the conversion to FBL.

From the past difficulties with the ground resonance, when I touch down, I leave the pitch at neutral, hit throttle hold and let it spool down. If it should start and form of oscillation, I increase the collective slightly (learned this from Dave K).

If you pull negative collective, at least when it was flybarred, it would make the oscillation worse. As a matter of course, I never put in any negative after touching down.

Not sure if you did or not Gregg, but just something I thought I would mention.

Which blades are you running? I am using Radix flybarred Stick Bangers on mine. These are fairly light, so it might lower the overall vertical CG a bit.

[ronstancil]

I'm using the RJX head, the blades are 150mm above the boom. I too had Ground Res, but now I land auto style. Come into a hover above the pad and hit throttle hold. As she spins down, raise the pitch until it wont fly any more and it settles onto the pad with no resonance. This technique basically lowers the the Headspeed before touchdown.

[pete best]

I'm using compass blades, I have some vblades too but I'm afraid to try them now.
I always auto when I land, but I don't really know if I applied negative collective when it happened. Fear took over and I could have done anything as my heli was dismantling itself on the landing pad. I need to get out to my shop to measure the head height but have a bad case of the lazy-bones today

[pete best]

OK, so from the top of the upper bearing block to centerline on the spindle I have 110 cm. A little over 150cm from the top of the tailboom to the blades. I'm going to start tearing things apart and see if I find something weird.

Is that about the same height as yours Ah Chlem?

[Ah Clem]

Pete,

I will get mine out and measure it.

As I recall, the head is only a few mm higher than with a stock main shaft.

I don't know if this is enough to make a difference in the tap-dancing on landing.

That, plus the very light blades, might be what makes the difference between our two ships.

You can see may landing bounces a bit at the end of the video (my bad landing) but does not enter into ground resonance. so I am thinking something is a bit different.

UPDATE: I found another thread, from when I first finished the Odin with the 7HV head-in that thread, I had measured the distance from the blade tip to the boom at 6.25" (158.75mm). My boom is pulled up slightly at the rear.

Can you measure the distance from the blade tip to the boom, sir?

[pete best]

I left it in a hover several inches off the ground yesterday, thinking I would hold it off the ground as long as possible to see if I could prevent the shakes and it did it in the air bad enough that it still popped the links off the swash. Very strange. I checked the main shaft and feathering shaft, both are perfect. Lubed up my dampners, tried another set of blades, but I'm afraid to try my v=blades because I don't want to lose them.

I need to try a 7hv main shaft I guess. My blades are only 148mm from the boom at the tip of them.

[pete best]

Crap, just pulled my 7hv main shaft out and realized it's drilled wrong. I will have to wait to try drilling a new hole at work for the main gear bolt.

[Ah Clem]

Gregg,

I re-read one of your previous posts. It looks like my head may be about 8mm higher than yours sir (measuring from the top of the boom to the blade tip).

As 5mm makes a difference on the 6HV, I am wondering if 8mm makes enough of a difference on the Odin (the difference in the oscillation tendencies of our machines would tend to support this, I think).

I cut a 7HV shaft to length to fit properly with the TracX Drive Tubes (i.e. get zero pitch without changing my swashplate height, then drilled a new hole in the shaft in the appropriate location. The goal was to get the 7HV head as high as possible-my concern at the time being the potential for boom strikes (there were rampant threads about DFC boom strikes at the time I was modifying my Odin, and I did not want to make the same mistake as one manufacturer in getting the main shaft to short). It may have worked in my favor with regard to the oscillations as well.

Please continue to keep us posted on your progress, sir.

[pete best]

New main shaft installed today adding 10mm of height to the head. Absolutely perfect!! Landed it twice to make sure. Not so much as a wobble. I never would have believed it, especially since it did it in the air as well as on the ground. Delrin rods are stretched to the max, and swash links are stretched pretty good too. I added a 5mm spacer to the anti-rotation link and a longer bolt so I could bring them all up. I'm tempted to try an anti-rotation bracket off my 3d plus so I can use regular links and rods on all 3 swash links so I can bring the swash plate up more. I'm very happy with the conversion now, I'm just nervous with everything stretched so far. I have a set of the tracx delrin rods for the 600 head ordered hoping they are a little longer than the 6hv/3d plus ones. Thanks for the help Mr. Chlem

[Ah Clem]

Greg,

" Thanks for the help Mr. Chlem"

You are most welcome, but please thank Mr. Ketelhut-he was the one that first commented on the relationship of head height/vertical CG and the role it plays in defeating the tendency towards oscillation on the 6HV and Odin.

Sounds like your ship it flying about like mine now, and I could not be more pleased with mine!

By the way, the TracX Drive tubes are 5mm longer than the 6HV ones.

[Ah Clem]

The Odin has been sitting since my friend Mike took the video (since the HF Fun Fly last October).

I don't fly it very often, due to concern over parts (although I have stockpiled quite a few.

I took it out yesterday and flew it. Other than the fact that the engine was a it balky, it flew just fine, so it is ready for the San Diego Fun Fly next week!