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HelicopterScale Model RC Helicopters › Vario EC 135 Jetcat PHt3
02-17-2014 06:02 PM  3 years agoPost 81
Peter Wales

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Orlando Fl

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That was not caused buy the tail melting. It was resonance in the heli probably caused by not securing the mechanics fully to the fuselage and I thought I saw a measure of out of track in the blades on spool up, but you cant always tell from a video.

The resonance then proceeded to rip the mechanics off the fuselage floor and flail things around inside, one blade hit the tail boom and did the damage.

But at least the pilot seems to have got out safely

Peter Wales
http://scalehelicopters.org

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02-17-2014 06:51 PM  3 years agoPost 82
NickC

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Leicestershire UK

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Alan

I agree with Peter, it could be just the camera/shutter effect but if you look at the 4sec mark the blade nearest the tail appears to be already out of balance and starting to resonate.

Its a while since I had an EC135 but is that the correct mainshaft ? It looks quite long.

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02-17-2014 07:36 PM  3 years agoPost 83
TaylorDrain

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California

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Sorry to see this Alan. I saw in a previous post of yours where there are braces on the top of the mechanics front and rear. What type of glue did you use to attach formers to the fuselage? Can you post pictures of how it was braced? The best part of using double wall pipes is that there is minimal heat transferred inside the fuselage.

Taylor

A.K.A TayloMadeUAS.Inc

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02-17-2014 07:38 PM  3 years agoPost 84
Double Decks

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Poole Dorset

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Hi Peter, I've just removed mechanics, not one bolt was loose I used locktite and lock nuts. They were so tight I had to use a solder iron to heat up the heads so to melt the locktite. The mounting frames for turbine are still bolted to landing skids as well. Top mounting frames are still in one piece , I will upload photos tomorrow

Alan matthews

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02-17-2014 08:10 PM  3 years agoPost 85
modtron

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Oxford. UK

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At 28 seconds, there is a forward / rear movement on the body - presumably induced by pilot operation, that appears to create a sideways shimmy just before hell breaks loose.

I personally think this is a mixture of a restrained machine fighting the head gyro but my biggest question is ...was the head gyro set up 100% correct for gyro output movements ?

The main shaft does appear to be much longer than original.

I would also take a good close look at the OF head and check the balls mounted onto each of the blade arms.

modtron
Oxford UK

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02-18-2014 12:37 AM  3 years agoPost 86
Mojave

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Palos Verdes, Ca. USA

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I watched the vid 20 times and all I saw was resonance. You actually see the point at which the fuse wrinkles at the base of the tail. It appears that once the vert stab started the high frequency vibe, it was all over. I did notice cyclic inputs being given during the spool up, but don't think that they had much to do with the resonance (unless the blades were loose). All FBL systems typically don't like big cyclic inputs when the heli is on the ground, but this one didn't act like that was the problem. Usually the heli will just roll over if the cyclic input was too much for the gyro to compensate for (with skids on the ground).

I agree with the other posts, I would check the head, also the main shaft length. If there is too much unsupported main shaft above the top bearing of the mechs, it can cause fairly bad resonance during spool up and spool down. My smaller R22 and my bigger huey have a lot of main shaft above the bearing, so I have set the helis up with a couple degrees of positive collective during spool up, as it calms the head down a lot. I also feed collective into the head while spooling down and this takes the resonance away.
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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02-18-2014 06:09 AM  3 years agoPost 87
Double Decks

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Poole Dorset

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Hi Nigel OF head is good, V-bar set up file was sent to Rainer who checked and recommended a couple of adjustments. If you could be here and look into the fuse you still can smell the resin and see the melted glass.

Alan matthews

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02-18-2014 07:24 AM  3 years agoPost 88
Double Decks

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Poole Dorset

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ec 135

Hi Peter Wales here are the photos of upper frames and lower turbine mounting frames as you can see all in one piece and landing skids still bolted through.

Alan matthews

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02-18-2014 07:51 AM  3 years agoPost 89
mookie

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UK

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It might well have been a mix of ground resonance and a weakened fuselage by the heat of the exhausts, however it happened I'm sorry to see it go like that.

Malcolm

valve boy!

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02-18-2014 11:56 AM  3 years agoPost 90
Peter Wales

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Orlando Fl

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You know how well your helicopter was built, I cant tell from pictures. I still say that was simply resonance which caused its destruction and OF heads have a reputation for being involved in that. This is the voice of experience talking

I have been there and done that and had exactly the same result you have had very reently. Total destruction of the heli just after lift off. The question is why did it happen and it is very difficult to analyse. Lack of fixing to the fuse is the usual culprit but if you are happy you fixed it properly, you have to look elsewhere.

As Barry says, a touch of positive pitch helps, but i have got into the habit of giving it hover pitch during the late stages of spool up so the heli slowly rises off the ground as the turbine approaches full speed. You have to be wary of doing this and overheating the turbine with the load if you add pitch too early, so it is not something I actively promote, but I have got the hang of it and thats what I do, but I didn't do it on the one which exploded recently

Peter Wales
http://scalehelicopters.org

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02-18-2014 04:47 PM  3 years agoPost 91
PETER ROB

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Devon UK

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Some answers

I have seen Alans work, it was not pretty, but strong, I asked him to check every joint and fixing, all are still secure, woodwork still attached to fuselage
The OF head came from me It had new damper rubbers, and I sent Alan a full set of new bearing, and I think he replaced all the old bearings
He also said he has +2degrees at bottom end, so I would not think he was loading the engine
I do not think the longer shaft, (needed for tail clearance) was the cause as I regularly fly with very long unsupported shafts
XLV photo
Peter R

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02-18-2014 07:51 PM  3 years agoPost 92
Peter Wales

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Orlando Fl

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Then you pose more questions than provide answers Peter. Something caused resonance to set in. OF heads with soft damping and heavy blades have a bad rep for this but I had 2 EC135s with this setup and they were just fine.

Maybe a Gremlin was jumping up and down on a blade causing bad vibes

Peter Wales
http://scalehelicopters.org

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02-18-2014 08:05 PM  3 years agoPost 93
PETER ROB

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Devon UK

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Peter that head came off an EC135, the new owner wanted Vario,
One thing we did not do was check the blades
Alan had run the set up a few times without blades to check things out, no problems then
I have had resonance a few times but usually off hard ground or concrete, the concrete being the worst
But applied pitch has usually been enough to cure it
I do not think we will ever get to the bottom of it,
One good thing only one blade is damaged, so still 4 left,
I may try the blades on a CAD-Jung head that I have
Peter R

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02-27-2014 07:59 PM  3 years agoPost 94
paul999

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ilford essex

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just seen this and made me sick to the core nothing worse than that happening after all the hard work and money,looking at the vid the tailboom does seem to flex and looks to be getting soft mind you im no expert like the others here who has watched it,did you check what the temp was on your ground ecu what was the max and min temps.
once again so sorry this has happend iv got my ec145 to set up and test fly and now im worried myself lol.
best regards paul

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02-27-2014 10:54 PM  3 years agoPost 95
heliVoY

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NJ

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Wow, im so sorry to see this ...

Tell you what though, my ec135 with same head crashed the same way on its last spool up. I was able to bring rpm down before it got really wild, but still resulted in cracked fuse and smashed tail. Its very repairable, but still a PITA...

I thought maybe i had a slipped link, but the more i hear of OF head problems, the more i think they just are problematic. The OF blades are heavy, and i think maybe they heads bendix just gives out..

on another hand, a FBL system might induce oscillations as well, and i have considered this as a suspect culprit as well.

Voy

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02-28-2014 07:05 AM  3 years agoPost 96
Double Decks

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Poole Dorset

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Vario ec 135

Hi Paul, Max temp was in the 70`s so not that hot, The fuse is still in my workshop and is still soft. dont know what to do with her at mo.
Helivoy, sorry to hear you have had problems as well, your EC is a lovely scale bird, hope you get her sorted, Im working on my next project so will post photos later.

Alan matthews

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02-28-2014 06:37 PM  3 years agoPost 97
heliVoY

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NJ

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here is a thread where i brought up some possible issues. I dont know the actual cause of my failure, and unfortunately have no video to analyze. In my case i had quite a few flights beforehand, so i'm not sure what went wrong . In fact i had a few good flights that very day . ( why its possible it was a popped link )

on a different topic, i have had 2 airwolfs oscilate apart in the air with electric Trex 600 mechs inside ... Both were braced up very very ridged too .. go figure :\

big helis, bigger problems :\ lol ... however there is nothing like the bigger turbine birds!

https://rc.runryder.com(that scale rc heli website )/phpBB2/viewtopic.php?f=20&t=16040

~V~

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03-02-2014 01:03 PM  3 years agoPost 98
Turbinator

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Nanticoke, PA

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That video looks excactly the same as what happen to my PHT3 EC135 twice and about a dozen times just the mechs on a simulation test stand. One time I was holding on to the heli by the tail on spool up and BANG took the tail right out of my hands and came God awful close to eating me also as it flipped up and spun 180 and landed where I was kneeling, barely escaped, I'll NEVER be that cloes to a heli again.

Some where I have a video of the mechs doing this over and over and over. Bend a main shaft every time. Peter you remember me, the guy you had send you his head and blades and you proved on one of your helies it was not the OF stuff but some thing else (remember the RH LH rotation mix up? I won't talk about that) You and the late AL Wert bent over backwards trying to get me in the air.

What are you using for servos and what are you using for a power system for the servos? How long are the control rods from the swash to the blade grips? How long is the main shaft from top of top bearing to the Jesus bolt hole?

I'm pretty sure is not the blades, the dampers in the head, the grips, main shaft material, as in trying to nail down my problem all these parts where changed 2-3 times some more. A couple differnt blade sets, 3 different heads, dial indicated and checked run out on the head, grip bolts, dynamially balanced the fenestron, had the turbine rebuilt and replaced every bearing in the mechs, reinforced teh fuse and it would still do it. Went to a VArio 2 blade 1680 setup and it would be fine (but hated the flying characteristics), go back to the OF and BANG on the third flight landing. Problem was I had 3 succesful flights on the OF at one point and after flying the Vario even with stab system LOVED the way the OF system flew with NO stab system, until on one landing the rear of one skid banged on touch down and set in again a resonance almost destruction, I was quick on flipping HOLD and nailed the collective progressivly and luckily it only bent the main shaft, losened up the mechs in the fuse but did not tail strike. The Vario 2 bolt was not as pleasant to fly so I was dead set on making the OF work, took almost 2 summers before I figured out what my "Gremlin" was. My 135 now has about 150 succesful flights on it with the 800 mm OF system, every spool up still concerns me as I think about resonance as one can NEVER forget such carnage and NEVER EVER forget almost getting eaten by that 800mm setup and being sprayed with parts in scurrying away.

Let me know on questions above and I'll reveal what cured my system and how I found it.

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03-02-2014 03:05 PM  3 years agoPost 99
Turbinator

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Nanticoke, PA

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Does this look familiar? Looks MUCH worse in the helicopter especially when the blades decide to contact that big tail fin on the 135 OUCH.

Watch at YouTube

The culprit? A battery backer that could not pass the current needed when servos would load up, found by hooking up a 4 channel O scope to each servo power lead and monitoring the voltage to each servo real time. Voltage would lull enough (3.6-4 volts at the servo, at rcvr voltage stayed above 4.2 volts) to greatly reduce servo holding power but not enough to reset or lock out the rcvr. Took out battery backer, hooked both Nicads directly to the receiver one at each end of the rail and it never happened again, on test stand or in helie. That was back in 2006, the helie still has the OF system on it and about 150 flights since then.

Even though it became known in the end the head and blades where not the culprits Al would not accept payment for the 3 sets of blades he sent me, 2 sets of dampers for the head, rebuilt the head once N/C, and replaced the head with a whole new one once. Al was a GREAT man and a loss to our hobby, I hope were he is he gets to fly all day every day and there is never any crashes. MUCH thanks also to Peter Wales for all the time, expense, and thought he put in in trying to help me also, another GREAT man in our hobby.

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03-02-2014 10:03 PM  3 years agoPost 100
Carey Shurley

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Orlando, FL - USA

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interesting, what servos were you running when you were having this problem and what servos are on the OP's model?

If you're not flying a gasoline helicopter
You're paying 10 times too much for fuel!!

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