More Bergen Turbine 4 Blade Video

[wolfdad]

Well, albeit not the best flying I have ever done, the link below is another video of the Bergen turbine with the 4 blade head. Some notable changes were moving the head gyro's on to a platform on the tail boom and using the 670mm blades. This was also the first time I had completely filled both saddle tanks (32 ounces each vice the stock tanks with 22 ounces each). The added weight and performance makes me think the 670mm blades are marginal as far as lift goes, so I am going to move up another notch to the 710mm Vblades. The 130mm tail rotor blades worked fine, however you will note an extreme tail wag in the video which came as the result of a failing tail rotor servo. I think you will also see that I performed a notable power-settling/turbine lag demo about mid-flight when I stared descending faster that I had power to arrest and turbine lag also was a factor. Bottom line was that I got into a fast descent and waited too long to cob the power back on. Also, about 75% of the way through the vid, you will also see a flame-out, also self-induced, I do believe either because of the violent tail wagging or because of engine settings or both (still tweaking the throttle curve). Anyway, I share the good with the bad, so although this was not my best flying effort, I still think there is a lot of potential for this machine as a multi-blade, turbine trainer.

http://www.navyspecialoperations.com/Bergen/bergen_turbine_fourblade_tailwag_042506.wmv

Doc

[cbergen]

Forgive me if this has been answered before, but what headspeed are you turning?

[wolfdad]

Chris,
Not answered before and, during this video, right at 1000. Also, flights today (2) exhibited same tail wagging. I think the culprit is the gyro mounting pad. Still had some of the good old "blue stuff" and have replaced the stock Futaba mounting pad with the "blue stuff."
Doc

[Gary Travis]

Congrats Doc it looks good to me even withthe wag. Must be pretty heart wrenching
Gary

[fitenfyr]

Wow...
That was some pretty scarey looking stuff....

I would have shut that thing down until I found the source of the wag, but that is just me.

Are you having some V-blades made for that or how are you going to balance all 4 close to the same weight?
I thought it was pretty critical to have all four blades close on those heads hence the reason OF sells the blades in sets.
Any reason you don't want to use the OF 700/710's?

[chopper jockey]

Doc, is your tail wagging because you fitted longer tail blades ?

[wolfdad]

Jason,
Concur...however, some trouble-shooting is required. You will note that I stayed fairly close to the ground with only a couple of excusions into forward flight. I am not inclined to "tease the tigers" and I think Chris has probably hit on the tailwag reason. Will share with all if it works. Also, Vblades came out of my spares locker. I have had several sets collecting dust for awhile and it just so happens that I was able to find two sets that were extremely close in weight. BTW, so everyone knows, I am completely satisfied with the OF blades...just that OF makes them in 670mm, then the jump to 800's and I want to try something in between. Vblades will come closer to being correctly weighted for multi-blade operation than anything else I have seen, so will give them a try and let you know. I think Vic and Jack might find themselves "on the spot" to start making some multi-blade sets. Right now, in my opinion, there is no competition for the OF blades or head....about as good as it gets and Al and Tim are super to do business with (unabashed plug for Starwood Scale :D ).

CJ, no, I don't think so, but it is worth considering. Bigger tail blades make the head stop sequence easier to see on video anyway :wink:. Enjoy your holiday today....looks like we may be getting another national holiday on 1 May...National Sit On Your Ass Day (a bit sarcastic because my back is killing me this morning).

Gary, thanks. I think Chris is on to something along these lines....something we have both seen before....dohhhhh! :arggg:
Doc