250 300X blade balance issues

[pvolcko]

I just did a repair on my 300X after having what I can only assume was a minor brain seizure at the bottom of a loop. I swear, why would I have gone full negative collective at that moment? Something is seriously wrong with my noggin.

Anywho...

I've had pretty good luck with the stock wooden blades so far, but this time I spun it up and it very nearly wrecked itself it was vibrating so bad. I spun the head by hand to see if it looked like a bent mainshaft and saw nothing wrong. Took the blades off and spun it up and no vibration issues (except in the tail, that's a separate, higher frequency vibe though).

So I put the blades on the scale. Wow. They were nearly 50 grains off from each other. I've never gotten a set this far out of balance before. In fact I haven't had a need to balance stock pairs of blades until this point.

Checked spanwise CG and they were within a mm of each other that way. Can only figure someone at the factory grabbed the wrong one when packing them up.

I balanced an unmatched pair of blades last week using scotch tape, since they were only 10-15 grains or so off from each other. But 50 grains, that's a lot of scotch tape. So I ended up using electrical tape this time. Ended up practically reskinning the light blade, as seen in this pic.



The central pieces are duplicated below the blade. The one piece off to the right was an attempt to adjust the COG. Too small a piece vs the weight of other tape. So I ended up with the cog moved a mm or so inward toward the root. Should be fine.

Will be spinning it up today.

 

[xokia]

A couple things on this 300x. You can get wobbles so bad you will snap the main shaft in flight. Make sure the belt is tight and not slipping. Check the hub that attaches to the main gear it can get bent if you bent a main shaft on a crash. People easily overlook the hub but is also can get bent slightly. Finally toss out the woodies they are junk. I had a set that I balanced and when I spun it up they still caused it to wobble.

 

[pvolcko]

I go through too many to go with CF blades. At least until today. Found a source for the CF's that is only a couple bux more than the wood blades.

Belt is snugged down good. No issue there.

I did notice the the jesus bolt hole in the hub had been elongated. I didn't have another handy so I put it back in and just put a bit more torque on the bolt. The gear is wobbling a bit more than I like, but I don't think it is the source of the vibes I'm still seeing. I think my tail hub got bent or maybe the bearings in the tial blade holders are shot. There is too much play in the blade holders and I think the tail blades are vibrating under load now. Got parts on order for the tail hub and holders, also the main gear hub.

Maybe it is the main gear hub putting things out of whack. Will see.

Going to try getting tracking on one more time. Seems like I've had to put a lot of turns into one blade and only getting marginal improvements.

I was just amazed at how mismatched the blades in this pack were. 50 grains difference, or about 3.2grams. Doesn't seem like a lot, but on these small blades that's like a 15% difference.

 

[xokia]

Belt must be tight slipping belt will cause vibes. Double check it, and the main gear hub is also the source of many vibes. It gets bent and its not easy to see. I had a set of wooden blades that did the same thing I spun them up and the entire helicopter shook like heck so much that the main shaft snapped. I tried balancing them which still never solved it. I tossed them in the trash and stuck CF blades on there and everything worked perfectly. I no longer use woodies.

The 300x is a cheap piece of junk heli you shouldn't expect anything to work right. It can be purchased for $220 new and the majority of that cost is the AR7200BX. I'd recommend purchasing the lynx dampeners as well as the lynx frame stiffener.

 

[pvolcko]

I'm looking into the frame stiffener. I've had a number of them crack right in front of the mast head on the right side. Hoping this will help keep that from happening.

I'm not expecting much from it, trust me. But I've rebuilt it twice now after big crashes and have gotten it back to perfect running order each time without much trouble. This time, minor crash, and I'm running into vibe issues.

Hopefully the hub and/or tail parts replacement will do it. I've never replaced the tail hub and blade holders so I suspect they're due. And there is damage on that main hub so it is likely the source of some issues.

I'll get it back up. I just love the thing. Relatively cheap to repair, enough power to do beginning 3D stuff, not so much power that I learn bad collective management. And the size is perfect for throwing around my back lot or doing stationary stuff closer up to the house. Also good for taking on the road to camp and whatnot where the size of the 550 or 700 is prohibitive.

 

[xokia]

Yes I agree the 300x isn't bad perfect for learning 3D. I'd recommend doing the bearing mod on the stock motor or but the wicked motor from asteroid design.

 

[murankar]

Xheli or hobbypartz.com have carbon fiber blades for $9 US. Not the best blades but they will get you in the air. I have used them myself when I was flying my EXI.

 

[pvolcko]

Ugh. I finally got the tail vibration fixed. Ended up having to loosen the tail case and tail fin screws a little bit.

Got half a battery of flight out of it and buried it. another frame, blade set, main shaft, main gear, feathering shaft, main blade grip or two, servo gears, servo horns, link arm or two, and who knows what else. I am sooooo pissed right now. Never have been this pissed after a crash before. I damn near want to throw the thing in a fire after shooting it with a shotgun after stomping on it after breaking it clean in half with my bare hands.

 

[xokia]

Bummer I know the frustration. You can buy a 300x shipped to your door for $235 from ultimatehobbies.com remove the beastx and sell for $150 it will sell quickly.

Either that or sell your current beastx and pick up a ready to fly heli. On the 300x sometimes it's not worth fixing. Use your old heli for spare parts.

 

[pvolcko]

I have a ton of spare parts for this thing at this point. I think this will be rebuild 4 on this thing. I have to get a set of frame stiffeners. I can deal with shafts breaking and spindles bending and blade grips cracking, it is the frame replacements that are annoying as hell. They don't cost much, but it is such an ordeal having to strip the thing down, remount esc and 7200bx, zip tie it all up again, etc.

It isn't even the repair that's pissing me off. I have the parts, I think. It's that I got less than 5 minutes of enjoyment out of the thing before wrecking it again. Came out of a beautiful loop with a half piro at the top, so I came down nose in right side up and I don't know what my brain was thinking but I kept feeding in forward elevator after I'd already completed the loop and had it hovering nose in. It's like my brain seized motor control of my thumb. I was screaming in my head, "pull back"... but the thumb just wouldn't do it.

I need to get some sim time in. So much rain lately, crazy work hours, and dorking around trying to fix the tail vibe, I haven't had enough flight practice recently.

 

[xokia]

The lynx frame stiffener is really good. I wouldn't wast your time with the asteroid design one it doesn't work so well. I smashed my 300x into the ground today at a pretty good rate of speed. Surprisingly destroyed the canopy, damaged a battery, snapped the main shaft, bent feathering shaft, snapped a CF blade in half, snapped a blade holder. Frame came out undamaged

 

[pvolcko]

Wow. Will grab one then. sounds like just what I need.

 

[pvolcko]

Got it rebuilt. Again.

Will order up the frame stiffener tomorrow along with some other items. Also hopefully flight test it. Tried a different leveling technique this time. Will see how it works out.

Final parts list. One servo killed, two sets of gears, main shaft, frame, canopy, blade grip and ball. Amazingly the main shaft sheered so quick that the main gear survived. Same on feathering shaft. Blades survived. Ground was wet enough that they dug in instead of cracking and splintering. Still took 5 hours to rebuild and redo the bx setup, but at least it didn't end up killing my parts stockpile.

 

[xokia]

You should not have to redo the entire beastx setup. Even though you swapped servos most of it should be pretty dang close to the same. You should be able to just go to the menu selection for the servo adjustments and make the minor tweaks.

The lynx frame stiffener is a nice piece and highly recommended. I purchased the astroid design frame stiffeners when I purchased my wicked motor. The damn things popped right off on impact and I still split the frame. Now the lynx stiffener I stuffed into the ground pretty hard and it held up well and kept the frame from cracking.

My wicked motor after 2 months I had to take out. It developed the same problem the stock motor develops except on the wicked motor it's the front bearing that goes out. It was the source of my insanely high vibes. I stuck the stock motor in and thing runs great again. I'm going to try a Scorpion 2213-14 just need to find a source for one in the states.

 

[pvolcko]

Not the whole thing. Just the time consuming ones: servo horn centering, swash leveling, blade leveling, 6 deg cyclic, 12 deg collective. I check the rest of the settings as I go through, just to be safe.

I did a quick test flight this morning before the rain hit. Blade tracking is good. Holds hover well. I think I need to adjust my 0 deg pitch and set the cyclic and collective angles again. I didn't have enough time to do some inverted hovering, but it felt like I was having to hold too much positive pitch to hold upright hover. Think things are skewed a little.

Tail vibe is under control still. May try another quarter turn looser on the tail case to see if that eliminates the little bit of vibe I'm still seeing.