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MTA Hobbies . Model Rectifier Corp . Heli-Max

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HIROBO Turbulence - SDX - Freya - Sceadu > Evo 90 stock dampner problems
 
 
Charley Stephens
Senior Heliman
Location: North Port ,FL

Today on my 4th flight on this new machine I started to do some Tic Tocs after about 5 th one I notice the Heli had become well lets just say Very bad in Cyclic response well kinda real mushy and very easy to over control.
Well I do get it on the ground safe only to look and Find Both dampner screws to be sheered off flush at the head hub "note" this machine is totally stock right out of the box, No upgrades.

later I find out this has happened to others. What is the fix for this. is Hirobo doing anything Etc...... Is there Replacement parts

I own an Evo 50 which has been flawless from day one and has so many gallons of fuel through it I lost count.... So I know they make a great product. That Said I want to fix this and let this machine Carry own with the Same reputation

Input please

Charley
05-28-2006 Over year old.
 
 
mudbogger2
Key Veteran
Location: Hoschton,Ga.

Contact Jeff Green and let him know what happend. MRC-Hirobo is his username here on runryder.

When you install the dampners did you use red locktite? Usually the bolts working loose is a big cause of this problem.

Jon Jennings
05-28-2006 Over year old.
 
 
shlm
Veteran
Location: West Chester, PA

As Jon asked, did you use red locktite on the head bolts? If you do not, my experience is that they will work themselves loose. Once they become loose I would imagine that they can shear very easily.
05-28-2006 Over year old.
 
 
Charley Stephens
Senior Heliman
Location: North Port ,FL

Yes, used Red lock tight Ok I will contact jeff

Charley
05-28-2006 Over year old.
 
 
WreckRman2
Key Veteran
Location: Indianapolis, IN

I'm just glad to hear you saved the heli! Do you have any pictures of it? The bolts and the dampners.

I will say that I have about 5 gallons through my Evo 90 now and I'm not a bit worried about this happening to me. I have that much confidence in this design. Yes, it's happened to some others but it's so few it must suck to be one of those guys.

________________
David Smith
317.777.3230
Align Trex 700, YS91SR, SB19, GY611
05-29-2006 Over year old.
 
 
Charley Stephens
Senior Heliman
Location: North Port ,FL

I agree I still have confidence in this design, also I'm sure it is something that is fluke and I just happen to be the lucky contender

Here is some pics
first pic shows that the Screws are still stuck in the dampners with lock tight.

second pic shows the sheered portions left in the head




Charley
05-29-2006 Over year old.
 
 
WreckRman2
Key Veteran
Location: Indianapolis, IN

Have you tried taking the bolts out yet? Pay close attention to see if they are loose or still real tight from the locktite. Do they appear to be wearing from a side to side action?

________________
David Smith
317.777.3230
Align Trex 700, YS91SR, SB19, GY611
05-29-2006 Over year old.
 
 
Charley Stephens
Senior Heliman
Location: North Port ,FL

no side to side clean breaks also they are still tight will have to disassemble the head and add a little heat to get them out maybe a left handed drill with possible easy outs

Charley
05-29-2006 Over year old.
 
 
Agilefalcon
Veteran
Location: Fort Worth, Texas

If the bolts loosen up, they will fatigue and fracture. You must use red threadlocker to secure them. To remove, use the heat from a hairdryer and they'll come out easily enough.

Chris.

Chris Berardi
MRC/Hirobo Representative
MAH Blades
05-29-2006 Over year old.
HOMEPAGE  
 
 
white chocolate
Key Veteran
Location: Baltimore, Md.

Also if you use too much red loctite it will get gunked up in there. If you have unscrewed the bolts a couple times it could also weaken the bolts from torqueing down on them to get them out.
05-29-2006 Over year old.
HOMEPAGE  
 
 
Charley Stephens
Senior Heliman
Location: North Port ,FL

If you read the earlier post it had 4 flights and was assembled uing RED LOCK tight, If you look at the picture they were clean breaks more like sheered off. The screws WERE NOT Loose and required more that a hairdryer to remove them it was more like a torch a drill and a small easy out
05-29-2006 Over year old.
 
 
Havoc
Key Veteran
Location: Ky.

Even with red loctite I've had mine back out a little on occasion. I check them every flight. I use the 80 duros and they do not have the countersinked hole so you do not get as much thread engagement. I ordered 14mm length bolts from McMaster-Carr and haven't had them loosen since. Ideally you would have about 1.5 x thread diameter of engagement.
05-29-2006 Over year old.
 
 
shlm
Veteran
Location: West Chester, PA

battlercon,

When installing the screws did they spin very freely in the dampners? I've seen it where the head of the bolt has been a bit too large and when screwing in the bolt the dampner would also spin. The net effect of this was that the bolt would not be fully seated. A little bit of sandpaper on the outside of the bolt head resolved it. Just an additional thought.
05-29-2006 Over year old.
 
 
Donkey
Senior Heliman
Location: Punta Gorda, FL

The 80 dampners that are made for the EVO have countersunk holes just like the 60s that come in the kit. If your's do not have a hole then they were designed for the Freya not the EVO.

Quote 
Also if you use too much red loctite it will get gunked up in there. If you have unscrewed the bolts a couple times it could also weaken the bolts from torqueing down on them to get them out.


What would a buildup of red loctite do that would break a 4mm bolt?

THe ship was brand new so he has not taken it appart and put it back together.

Donkey you have the right to remain silent what you lack is the capability
05-30-2006 Over year old.
 
 
Havoc
Key Veteran
Location: Ky.

Maybe. All I know is that I ordered the "harder dampners for the evo" at the same time I ordered the evo and this is what I got.
05-30-2006 Over year old.
 
 
white chocolate
Key Veteran
Location: Baltimore, Md.

So you saying that if you put too much red loctite in that it wouldnt over torque the bolt trying to get it out?? Especially after a few times of taking it out and putting it back in and it getting gooked up. Dont ask me how I know but it can happen!!
05-30-2006 Over year old.
HOMEPAGE  
 
 
TMoore
rrProfessor
Location: Cookeville, TN

Quote 
What would a buildup of red loctite do that would break a 4mm bolt?


It's not the build up of red loctite in the tapped hole. What happens is that when you use red loctite and then remove the bolts, a little of the tapped hole is abraded away when you remove the bolt. Don't believe me? Then ask yourself what application you would want to use permanent anerobic sealant like red loctite on? Most of the time it's steel to steel, steel to cast iron, steel to titanium or CRES to CRES (corrosion resisting steel or stainless steel). Steel to aluminum is not an application that is normally associated with red loctite. Every time you remove and then reapply the loctite and bolt, part of the thread is eaten away. The only way to combat this is to use a Helicoil or a through bolt.

I'm running mine with purple loctite on the screws.

The best way to fix this is to just drill out the mast and replace the individual bolts with through bolts and nuts a la CX.

The failure in the photo looks like the bolt was sheared away.

TM
05-30-2006 Over year old.
HOMEPAGE  
 
 
Donkey
Senior Heliman
Location: Punta Gorda, FL

White Chocolate
I was not saying I did not believe you...I did not understand what you were implying. Now that you have explained it I will say I don't believe you. TMoore is right (it pains me to say that) but the AL will suffer more from repeated uses of red locktite then the hardened steel bolt. THere is only four explinations for what happened.
The bolts loosened up allowing the dampner insert to act like a giliteen (sp)
The bolts were overtightened and prestressed beyound thier design. (I believe this is what White Chocolate was saying.)
The bolts were not of sufficient strengh to do the job (I doubt this)

Or
The bolts were defective.
I think it is a design flaw. The Freya has been out for years and this has not happened to the degree it has with the evo. I THINK that as the dampeners rotate in flight with the head of the bolt countersunk into the dampeners it loosens the bolt. The more red loctite you have around the head of the bolt the more "grab" it has in the dampener. No add in the fact like TMoore said you remove some AL each time you unscrew the bolt (leaving less for the loctite to grab) the quicker it will come loose.

Donkey you have the right to remain silent what you lack is the capability
05-30-2006 Over year old.
 
 
pwood
Key Veteran
Location: Dubai - UAE

Hi guys

The other cause could be that one or both the bolts were too long and the ends of the bolts were touching.

What would happen is the first one would get tightened down and then the second one would "bottom out" without pulling the damper up against the ali mast hub. The rubber damper could move out in flight and change the shear force on the bolt to a bending moment and suprise suprise it will fail...

The big thing to watch out for is the dampers with the recess for the bolt head (ie Evo) use shorter bolts.

I am not saying this happened, just somthing to watch out for...

Paul
05-30-2006 Over year old.
 
 
white chocolate
Key Veteran
Location: Baltimore, Md.

Well it has happened to me. Didnt really care if you didnt beleive me. I was just sharing that this could happen too. I also was not implying that this is the case for battlercon. Just felt like adding to the post. Wont happen again!
05-30-2006 Over year old.
HOMEPAGE  
 
 
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HIROBO Turbulence - SDX - Freya - Sceadu > Evo 90 stock dampner problems
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