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HomeAircraftHelicopterHIROBOOther › Eagle3 EP SSZ-V Mast Bumping Problem
04-26-2013 04:37 AM  5 years agoPost 1
Bugcatcher

rrApprentice

Perth, Australia

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Hi guys,

Just chasing some ideas from possible solutions from anyone that may have had some experience with mast bump problems on the SSZ-V head.

Firstly, I have 2 idential Eagle3 EP's. First was built about 6 months ago apart from fitting the new white dampners and Funtech paddles, everything else is out of the box. Never had any problems running 1450rpm HS. Sometimes if it's a bit brezzy it may bump slightly but raising the HS to 1480rpm usually fixes it.

My second Eagle 3 EP I maidened over the weekend is identical except for a different motor I'm trying out (Actro vs Hacker) Again white dampners and Funtech paddles, same flybar.

Now the new machine has a bad mast bump at 1450rpm. 1400rpm is fine and mast bump starts showing up around 1420rpm HS.

At our club we have 4 Eagles with SSZ-V(3 EP, 1 Nitro), 3 D3's(SSZ-IV) and a Freya (SSZ-V) and of those atleast 4 have had mast bump issues. A D3 that never had a mast bump problem has now developed one with changing anything. The Eagle 3 EP Nitro has had itermittent MP problems with the head even going back to factory to be rebuilt.

Again my Eagles, idential as you can be, one is super smooth but the other has the Mast Bump problem.

Things we have tried:
- blade grip tension. Little or no change
- HS anywhere between 1400-1700
- balanced the flybar assembly
- de-burred the centre pin in the head, this can scratch and gouge the spindle if any sharp edges. Spindle moves and rotates very free without binding, grub screw is removed.
- tuning of the motor on the Nitro Eagle, (did make a bit of difference but didn't remove the mast bump completely.
- all head settings are as per manual
- dampners have been well greased

One thing i'm going to try tonight is mount one of my Vbars on a gyro plate and use the Spectrum Anaylzer to monitor vibration levels through the rpm range to see if I can track it down to a source. Other thing to try is do a straight swap of the heads to see if the mast problem follows the head or the rest of the mechanics.

Any ideas from anyone would be great because there's been a few very smart people trying to track down possible causes. Can't say it's specifically a Nitro/EP issue either because the problem shows up on both and even an SSZ-IV head.

Thanks.

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04-26-2013 06:22 AM  5 years agoPost 2
Flyinhelis

rrApprentice

USA - So. Cal. the OC

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Try different length flybar.

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04-26-2013 07:30 AM  5 years agoPost 3
Bugcatcher

rrApprentice

Perth, Australia

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I agree trying a flybar is worth a try but shouldn't be a necessity. Choice of flybar length should be dependant on an individuals preference to the feel of the head.

Again still worth a try.

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04-26-2013 11:17 AM  5 years agoPost 4
fastrc1

rrKey Veteran

Planet Brooklyn, NY-USA

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Try removing the center pin and pivot bearings.

Eaton

RIP Roman Pirozek Jr.
Team Futaba USA
Team Kontronik USA
http://flysrw.com

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04-26-2013 11:58 AM  5 years agoPost 5
rapidity

rrVeteran

ohio

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It seemed to be fairly common on the IV head at the lower headspeeds. First I've heard of it with the V. I had 2 IV heads and they drove me nuts, after switching to the V never had any problem. Know its not any help, but could never figure it out on the IV's.

We used to run the black SDX dampers. This was before the new white ones came out, they're slightly stiffer. Might be worth a shot.

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04-26-2013 12:27 PM  5 years agoPost 6
Bugcatcher

rrApprentice

Perth, Australia

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Yeah it's pretty frustrating.

The SSZ-iV and SSZ-V are nearly the same head. Main differences are the SSZ-V has wider blade grips, and the pitch/mixing arms are different. More delta on the SSZ-V arm.

The head block/dampening system is all the same. Of note the SDX and D3/E3 dampners use the same rubber, the difference is the D3/E3 has a metal sleeve. The new whie dampners are softer rubber with the metal sleeve and was made to fix the mast bumping issues at low rpm.

My confusion is that I have 2 identical heads, put together the same way yet display 2 completely different characteristics.

I'm about to compare vibs on the vbar spectrum analyser now out of curiosity and try a couple things. I've heard about removing the centre pin but was reluctant as it pretty much takes away the tettering effect of the head. I will try it though, again out of curiosity.

Thanks for everyones input.

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04-26-2013 02:54 PM  5 years agoPost 7
richardf

rrVeteran

San Diego, CA USA

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I worked quite a bit with Dr Ben on my SSZ-V trying to get rid of the mast bump issue. In the end, the white dampers helped, but not until I removed the center pin did it settle down.

-Richard

Team JR Americas - AMA 4628

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04-26-2013 07:43 PM  5 years agoPost 8
2kwik2c

rrVeteran

Chino Hills, USA

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Since you've taken out the center grub screw, disassemble the head unit down to where the dampners and spindle are exposed. Take out the spindle and dampeners. Lube the part of the center hub where the dampners sits. Lube the dampener's holes where the spindle goes through it. Then lube the exposed spindle before putting back the balde holders. Then assemble everything back. Check your settings again and then hover it at your desired head speed.

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04-26-2013 07:57 PM  5 years agoPost 9
Santiago P

rrProfessor

South West, Ohio

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Im running two SSZ-iV configured for FAI. Both have the SDX dampener, both the center pivot removed. None show mast bumping issues unless I get below 1400.

Santiago

Team Minicopter - PeakAircraft.com
bavarianDEMON- Team Kontronik - Scorpion Motors-

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04-28-2013 03:20 PM  5 years agoPost 10
Bugcatcher

rrApprentice

Perth, Australia

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Just an update.

Both myself and Brian Simpson of PerthRC have tried everything possible with my B machine. Only thing not done was remove the centre pin which is the last resort.

Completely rebuild the head again and greased/lubed everything.

Hirobo factory also suggested oiling the blade spacers and drag bolts, we did that.

I even swapped the whole head to a my SSZ-IV that has working fine at 1450rpm previously without any mast bump. Still a problem, rock solid up to 1410rpm, then mast bumps till about 1510rpm.

Tried different flybar today, no change.

Next step is try another SSZ-V head working and hovering fine at 1450rpm off a Freya. Freya was flown 2 days ago and is smooth as.

If that doesn't work, last option is to remove the centre pin.

I am starting to lead more to the fact that it could be resonance going through the frame at that rpm causing the mast bump and not actually the head.

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04-28-2013 03:37 PM  5 years agoPost 11
fastrc1

rrKey Veteran

Planet Brooklyn, NY-USA

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All machines have a resonant frequency/harmonic generally in multiples of two's. If it occurs @ 1410 the next approximate is 2820 and I don't think you're going to be spinning that fast.

RIP Roman Pirozek Jr.
Team Futaba USA
Team Kontronik USA
http://flysrw.com

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04-29-2013 03:26 AM  5 years agoPost 12
Dr.Ben

rrMaster

Richmond, VA, USA

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Let the axle fully float and use the SDX dampers well lubed. The chances of it mast bumping will then be minimal.

Ben Minor

Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA

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04-29-2013 03:45 AM  5 years agoPost 13
Bugcatcher

rrApprentice

Perth, Australia

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Not sure how the spindle can float any more than it is already. Using the white dampners which are softer than the SDX ones, no grub screw and spindle takes very little effort to turn/spin with the head assembled. Last option is to remove the centre pin.

Going to try a different main shaft and couple of other things tonight.

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04-29-2013 01:21 PM  5 years agoPost 14
Dr.Ben

rrMaster

Richmond, VA, USA

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Not the same.

Free floating means unrestrained teeter and lead/lag.The axle being able to spin has no bearing on this problem. The only time that would be a player is if there were obvious vibration caused by the axle being restrained off center coupled with misbalanced blades.

Ben Minor

Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA

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05-01-2013 04:52 AM  5 years agoPost 15
Bugcatcher

rrApprentice

Perth, Australia

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Okay good news, whatever I did last night seemed to be the answer.

Overall I did alot of things so TBH I can't really track the fix to one thing or could have been a combination.

Firstly, re-built the head again. Purchased a 8mm reamer and used it on the white dampners and centre pin until the spindle moved silky smooth. Reassembled dampners and centrepin using a Magnalube after which I used the 8mm reamer again to make sure nothing binded in the assembly. I did take take with the centre pin when tighening the bolts on the bearings as it can pull or push the centre pin sideways.

Also installed new thrust bearings even though the one in there looked and felt fine. Should be only a few flights old.

Replaced the main shaft. Re-checked the main shaft bearings and alignment. Bottom bearing was slightly out sideways, managed to bring it in line by slightly sanding an end of the 2 collars to one side that join to the lower frames. Basically pulled the bearing to one side 0.1mm and main shaft dropped straight in.

Last thing was I re-checked all the rod-ends and reamed any that were even slightly tight.

After that the Eagle hovered rock solid from 1400rpm up to 1510rpm with out the slightest mast bump. Planned to test higher head speeeds but the ESC decided to reset itself after the first flight so that was that.

TBH i think most of was in the metal sleeve of the dampners and the grease I used. What I did notice was the lastest white dampners I got were alot tighter on the spindle that the very first ones i used in my first Eagle EP. Going to be going through my whole fleet now and doing the same including FBL D3's and think I might even get rid a weird head bobble at low HS as i'm fairing on my auto's.

Something for people to maybe check if they have similar problems.

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05-01-2013 07:48 AM  5 years agoPost 16
Santiago P

rrProfessor

South West, Ohio

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congrats on the new silky smooth head
including FBL D3's and think I might even get rid a weird head bobble at low HS as i'm fairing on my auto's.
Dont get crazy looking for mystery wobbles. What u described is pretty normal once the head speed starts decaying during an auto with FBL, the blades may lag a bit and sit "out of phase" inducing the wobble.

santiago

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