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HomeAircraftHelicopterBergen R/C Helicopters › Clutch slipping?
05-07-2005 07:29 PM  13 years agoPost 1
iflybyu77

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Fort Wayne, IN

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Ok, here's the deal. I have an Intrepid EB that is solely used as an AP ship. I'm running into a very concerning issue with it right now though. When I'm in descents, or under high load / high blade angle climb-outs, the tail is kicking and the nose swings left - sometimes hard. On a fairly moderate descent yesterday, with AP rig beneath, the engine bogged hard on initial flare, and then the heli rotated left hard only inches above the ground. Today, I adjusted the carb to where I *THINK* it's not running so rich (the high needle was maybe open a bit more than 1 1/2) and leaned the low a bit too. I did a few climbouts, and still the nose kicked around to the left (no mount). Well, then I was doing a demo for a client today and on a very mild descent in semi windy conditions it did the same thing again.. except I was kind of ready for it and kept the heli from fully rotating by backing off the pitch/throttle a bit.

So, there's the problem, and here's a few things I think it might be. Too low of headspeed, too small of tail rotor blades, badly tuned engine, or a slipping clutch. Or maybe a combination of all four? I also do NOT have a driven tail, fyi.

I don't know my headspeed right now (did some tweaks and don't have a tach available as I'm out of town) and I'm running the stock plastic blades since a nice little rock took out my NHP tail blades (they were 105mm). The clutch has always been babied, no hot starts, easy spool ups. The carb has been turned in to maybe 1 1/4 on the low and probably about the same on the high. I wish I knew if it was right or not - that must be the million dollar question with gassers.. I'm still running 6 oz to 1 gallon camper (on last of my second gallon before switching to 5 oz to 1 gallon synthetic (using lawnboy now) - which I'm guessing is the right setup?? Also, I have NHP Razor 800's .. which might be good to note.

Lastly, I'm really not impressed with the stability this thing has been exhibiting. Seems to need a lot of babying, unless it's really light winds (is this a low headspeed issue too?) I'm using 95mm v-paddles - no flybar weights (yet). Any suggestions on this? I'm tail heavy right now (only have a sub-c and one aa pack up front, plus receiver and battery backer) and have a zimmerman rear mount muffler - would any of the tail heavy issues be causing the stability issues? How much weight should I expect to have to put up front to get the cg at the mast, and what type of weights (lead stick on stuff?)

Dang, that's a lot of typing. Hope someone reads the whole thing

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05-08-2005 12:44 AM  13 years agoPost 2
Disciple4123

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USA

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I will say that I first built it with the original white tailblades, and a low headspeed and experienced a frequent loss of tailrotor effectiveness during operation past 2/3 throttle-collective, or when the wind/conditions caused a loss of yaw control. I also experienced the unstability you described. I installed the V-blades longest tail blades, governed the headspeed to 1300-1400, and it was corrected. Around the same time discovered the front pinion to shaft setscrews to be loose (1/8 turn of play but no complete turnover slipping, something to check). I red loctited the shaft & screws. I found that a lack of headspeed was the greatest contributor to yaw stability, followed by TR blade length. Mine is set up solely for AP as well. As far as flybar weights, I run some old JR ones out all the way on a set of fairly conservative plastic JR paddles.

You also mention it being rear heavy, although I got mine slightly rear heavy, but not too bad, with a front end alternator and other equipment. I agree that you may want to get the weight balanced for good measure eventually. Can you move-redesign your camera rig to weigh more upfront?

Hope this helps,
Eric

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05-08-2005 03:30 AM  13 years agoPost 3
Chris Bergen

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cassopolis, MI USA

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Low headspeed will definitely cause the conditions you noted, including slipping the clutch.

The EB is geared to run a lower headspeed (1400-1500) while keeping the engine in it's power band. If you try to run a lower headspeed by keeping the throttle down, you will notice a lack of power, slipping, and all the other tendencies you mentioned.

Don't be afraid to spool it up, especially is you have V-Blades installed. We routinely spool up the Twins with 800 V-Blades to 1650-1700, The head and Blades will take it.

Your EB is geared differently, so you won't get it this high, but 1500 is no problem.

Chris D. Bergen

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05-08-2005 02:58 PM  13 years agoPost 4
wolfdad

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Southern Maryland

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BergenRC is giving you the correct solution. Head speed in the 1450-1500 range should smooth out a number of your problems. Also, double-check your tooth count on the pinion. I believe the EB kits are coming with the 11T pinion.

wolfdad sends...

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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05-08-2005 08:47 PM  13 years agoPost 5
iflybyu77

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Fort Wayne, IN

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hmm
Do you think the stability issues in every other axis are a direct result of headspeed?

As I sped it up yesterday, I noticed a lot more fuel foaming issues, and the tail push rod was going into resonance (don't have a strap holding it right now..) I still have no way to check headspeed, but as I'm increasing it, I'm noticing vibrations that weren't there before. Can anyone tell me about how much actual throttle input is around 1400-1500? 40%, 50%?

Disciple, which size tail rotor blades were you running? I thought that my NHP's had less of an issue holding it (which is why I got them in the first place.) Maybe the new EB's need to come with longer tail blades. Also, I wondered about tail rotor tracking - I checked the links and they are dead on identical, but I'm wondering if any of my vibes are coming from them being out of track (they sometimes look like they are).

I know the issue has been pounded into the ground, but as far as tuning goes, I'm really struggling to hit spot on what I'm supposed to be at. I know you suggested Chris that you start both the high and low at 1 1/2.. did that, and started tweaking the low first.. noted that on spool down after a bit of turning (probably too much) that the engine wouldn't drop completely into idle (guessing it was too lean) I didn't run it long enough to damage anything, but I'm guessing that I need to go a little richer. Not sure to verify the high end though.. should I just do punch outs and see how the engine responds?

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05-08-2005 09:40 PM  13 years agoPost 6
Sar

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Saugeties, NY

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Just on a side note, make sure that your TT isn't slipping. This caused similar issued for me.

--
Jon

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05-08-2005 10:48 PM  13 years agoPost 7
iflybyu77

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Fort Wayne, IN

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a good suggestion..
I talked to Larry when I first built it and he suggested slightly dimpling the aluminum shafts and putting the grubs through the tube so that this very issue wouldn't happen. I'm almost 100% with that fix there will be no slipping.

On a side note, does anyone know if Craftsman's 2 cycle synthetic would be an acceptable alternative in a pinch?

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05-09-2005 12:03 AM  13 years agoPost 8
iflybyu77

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Fort Wayne, IN

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Greg..
Why.. I believe I did actually.. ??

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05-09-2005 04:05 AM  13 years agoPost 9
Disciple4123

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USA

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"Iflybyu77" I use 110mm V blades. As far as tailrotor integrity, one thing to check for is to try and twist the tail gearset against the TT. The two retaining bolts, if loosened or too long, will rock in the TT. I fixed mine up by Loctite dipping the outer TT to gearbox contact area, as well as all junctions inside the arrow shaft. If dissasembly is needed later I might have to sacrifice the arrow shaft by dissasembling with heat, but I rather do that and have the piece of mind that slippage or movement will not occur.

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05-09-2005 04:21 AM  13 years agoPost 10
Sar

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Saugeties, NY

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Mine were dimpled as well, but I guess the hole in the TT was not big enough. I enlarged the holes a bit and re-assembled everything with a bit more torque. I hate torquing down on aluminum collets though :P

--
Jon

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05-09-2005 05:55 AM  13 years agoPost 11
iflybyu77

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Fort Wayne, IN

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Greg..
I think you misunderstood me.. I did all three set screws in each collet. I'm guessing you may say something about the integrity of the arrow shafts? I thought about that but I think I'm safe after considering it for a while. Was there something else I didn't consider while doing this?

Terre Haute is about 3 to 3-1/2 hours from me.. I'm going to be driving back through there in a few days (in Oklahoma right now - Tulsa to be specific). Why you ask?

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05-09-2005 02:22 PM  13 years agoPost 12
wolfdad

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Southern Maryland

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Greg,
My feeling is that your explanation is a good one. By drilling/dimpling all three, the arrow shaft is now free to "do it's thing" and will eventually enlarge the holes and continue to work the holes larger. By drilling/dimpling all three, you have essentially eliminated any surface contact between shaft and input/output quill. I may be incorrect on my thought process, however one hole locks the shaft in position and the other two provide a clamping action between the arrow shaft and input/output quills.

wolfdad sends....

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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05-09-2005 04:15 PM  13 years agoPost 13
iflybyu77

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Fort Wayne, IN

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wolfdad..
Now that sounds more likely.. I can imagine that might occur, however, I would expect it more if this were a 3d ship with ultra high loads being exerted when transitioning the pitch of the t/r. I would now, considering this, also follow this recommendation. I think in my case however that I'm probably safe.

No one said anything about my thought to use Craftsman synthetic.. ??

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05-09-2005 04:46 PM  13 years agoPost 14
wolfdad

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Southern Maryland

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Dave,
A couple of thoughts for you...the G26 is capable of producing some pretty awesome torque and most of that is transmitted through that arrow shaft to the tail. If you have drilled all three holes in the shaft, I would recommend you consider calling Larry and ordering a new shaft. Ultimately, I think you will probably spin that shaft through those holes and, a new arrow shaft pales in comparison to trying to auto that beast with no tail....believe me I know...did it down at Blacksheep a few weeks ago for an unrelated problem (collar slipped...crown gear got eaten and I had NO tail rotor).

Initially, I ran the Honda synthetic oil for the first few tanks in my Hanson and this was recommended as an alternative to the Blue Marble. When the Blue Marble arrived, I promptly switched over to that and I am an evangelist when it comes to the Blue Marble and the 6 ounces to the gallon mix. I think Greg is probably running 5 ounces, which I think is fine as well....me, I run the 6 ounces out of fear after frying my stock G26...paranoia set in if you know what I mean. I suspect the Craftsman is probably a similiar blend to the Honda oil...may even be the same stuff with a different wrapper. I would verify that, though and check viscosity, etc.

Also, I just spoke to Greg by phone and we were both telling you the same thing...just saying it in a little different way.

Good Luck and keep us posted

wolfdad sends.....

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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05-09-2005 06:10 PM  13 years agoPost 15
wolfdad

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Southern Maryland

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Greg,
Glad to hear it....just my paranoia after roasting that first G26 with the "other" stuff. Hope all is well with you out in the "heartland." Finally, got some really nice flying weather back here as well.

Doc

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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05-09-2005 08:45 PM  13 years agoPost 16
Chris Bergen

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cassopolis, MI USA

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While dimpling all three probably won't hurt, it's not at all necessary. The theory on the clamping action is a good one, just as we only use 1 setscrew in the tail hub!!

Occasionally inspect your TT for cracks in the end where you have drilled the 3 holes, other than that, go fly it.

Chris D. Bergen

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05-10-2005 04:45 AM  13 years agoPost 17
Zach Sparks

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Norton Shores, MI

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wolfdad
Could you please PM me with the brand of oil you specify as the "other." I am about 1/3 of a gallon into my two gallon break-in using Lawnboy and Ozark Camper fuel and I will be switching to 5oz per gallon synthetic with the Ozarks but I am still out to lunch on what kind I will be using. I am getting about 30 minutes to a tank right now so I suspect by July I will be ready for synthetic. HEHE.

Thanks.

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05-10-2005 05:23 PM  13 years agoPost 18
iflybyu77

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Fort Wayne, IN

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well..
I did a few adjustments..

Cranked up the headspeed a bit, tried out some needle settings that Larry suggested for a baseline, tweaked a few things in the head, and it sounds better. I'm still thinking it's working pretty hard - seems to bog still a bit (you can hear it in the onboard video d/l feed - which is an excellent tuning tool fyi.. )

Worst of all was that I noticed the choke was wanting to close IN FLIGHT.. just wiggling closed. Well, after doing a shoot out here over a water park where I saw probably 200-300 foot altitudes AGL, I started a decent back to landing, where at about 20-25 foot up the choke closed, and the engine died. After reviewing the tape, it took *2 seconds* before the heli was on the ground.. from 20 foot! I'm mortified at how horrible it autoed. I'm wondering if it's these NHP Razors????(800's) It bounced decently hard but did no damage to my camera mount or the heli. Absolutely stunned when it happened, and I'm supremely gun-shy of shooting autos with it now. I've done low level ones before with just the heli, and those weren't really pretty either, but this was awful. I wasn't in FF of course, as I was simply descending. Post flight inspection revealed the issue with the choke was just a wearing of the bushing in the carb - fixed that with a rubber band around the air box housing.

Finished shooting the day without further incident, but I've come to expect the worst lately it seems. Even had the camera mounts skids catch in the grass and the whole heli tipped over backwards almost onto the tail (was moving backwards faster than I thought). Full forward cyclic recovered it - which was lucky as I had almost just cut the throttle and wouldn't have had the headspeed to tilt it upright. Yikes. I'm wondering after all these "incidents" if anyone would even be brave enough to fly near me..

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05-10-2005 06:03 PM  13 years agoPost 19
iflybyu77

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Fort Wayne, IN

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nice..
absolutely! That's pretty close to me.. less than an hour I think (used to fly full scale out of there from my instructors grass field..)

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05-10-2005 06:13 PM  13 years agoPost 20
mfendley

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Saint Marys, GA

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To be a submarine sailer means that you had to have seen a sub in the last five years . . . . .

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