RunRyder RC
 38  Topic Subscribe
WATCH
 20 pages [ <<    <     9      10     ( 11 )     12      13     NEXT    >> ] 22941 views TOPIC CLOSED
HomeAircraftHelicopterAlignT-REX 700N › 700 Exploded today/POLL how many have had this happen??
01-19-2010 01:39 AM  8 years agoPost 201
PC12DRVR

rrKey Veteran

USA

My Posts: All  Forum  Topic

I could not agree more ^^

PM  EMAIL  GALLERY  Attn:RR
01-19-2010 08:09 AM  8 years agoPost 202
Fernando

rrApprentice

Madrid

My Posts: All  Forum  Topic

At this stage I am probably going to machine up a shouldered bush
insert it into the end of the shaft and then use a M6x16 Unbrako Cap screw 12.9
It seems that the problem has been well identified: looks like the non threaded portion of the spindle or shoulder plus a low quality bolt are making the bolt to bear radial forces that should only be taken by the spindle.
The bolt issue seems to be easily addressed by buying a better quality one but the question now becomes how to address the spindle shoulder issue until Align comes up with a non defective one??.

I still think the best compromise solution at this moment should be the good quality bolt alone without spacers or shims.

PM  EMAIL  GALLERY  Attn:RR
01-19-2010 01:25 PM  8 years agoPost 203
PC12DRVR

rrKey Veteran

USA

My Posts: All  Forum  Topic

Fernando, you're probably right but I am going to fill the gap with a brass spacer anyway just to be on the safer side. JB weld the appropriate size tubing onto the bolt as a shoulder screw it in and let cure. if there is a slight misalignment in the spindle opening the spacer will conform and not transfer a preload to the bolt. The washer at the end of the bolt is also better for not tranfering radial loads to the head of the screw, it allows for a little "play
" so forces are not directly transferred to the bolt head. Most other heli feathering spindles use this combination, bolt and washer,two pieces, and we don't see them failing.

I think the Align bolt head is too rigid. Now add the runout on the face of the bolt head that seats on the radial bearing inner race unevenly, and you are now tranfering radial loads to a rigid poor quality bolt that is only supposed to bear axial load. A fraction of an inch of movement over and over, on poor quality steel, and POP here you are.

I also don't think the shoulder on the Align screw is seating in the spindle, there seems to be a slight gap, this would allow for movement, actually defeating the whole purpose of having the shoulder.

PM  EMAIL  GALLERY  Attn:RR
01-19-2010 02:22 PM  8 years agoPost 204
jschenck

rrProfessor

La Vista, NE.

My Posts: All  Forum  Topic

Most other heli feathering spindles use this combination, bolt and washer,two pieces, and we don't see them failing.
I wonder if the fix could be just that simple - put a washer on the bolt. Unfortunately setting up a test scenario is not simple.

PM  EMAIL  GALLERY  Attn:RR
01-19-2010 02:23 PM  8 years agoPost 205
Fernando

rrApprentice

Madrid

My Posts: All  Forum  Topic

I will not use the spacer myself, only the bolt. But what I do think is that everyone with one of both solutions need to report their findings/issues back to this post.

I think in the absence of a good quality support by the Brand we need to address this very, very dangerous issue.

PM  EMAIL  GALLERY  Attn:RR
01-19-2010 02:26 PM  8 years agoPost 206
jschenck

rrProfessor

La Vista, NE.

My Posts: All  Forum  Topic

I think in the absence of a good quality support by the Brand we need to address this very, very dangerous issue.
+1 !!

PM  EMAIL  GALLERY  Attn:RR
01-19-2010 07:01 PM  8 years agoPost 207
CoronaL

rrKey Veteran

Winnebago IL

My Posts: All  Forum  Topic

Damm
I have 2 700's and haven't had this happen---Yet.

One of my 700's has a Kasama head on it, and until we get some more feedback on the cause of failure, I'm going to run my Kasama head 700 only , as it uses it's own spindle and bolt, of much higher quality and NOT the shouldered design like Aligns

Randy!!! I am the liquor

PM  EMAIL  GALLERY  Attn:RR
01-20-2010 07:10 AM  8 years agoPost 208
Lplate

rrNovice

Singapore

My Posts: All  Forum  Topic

Is it possible that while tightening the bolt, the shouldered part stops going in further because of the 'cup' on the spindle and further screwing causes the bolt to be stretched and thus weakened? If that is the case,would not over tightening but using better/more locktite, like red one, be better?

PM  EMAIL  Attn:RR
01-20-2010 11:56 AM  8 years agoPost 209
hanzuki

rrApprentice

London, Ontario-canada

My Posts: All  Forum  Topic

I was talking about this with a coworker yesterday and he suggested that maybe the shoulder was bottoming out in the spindle before the head of the bolt placing all the stress on the weakest part and providing clearance enough for the head to rock a bit. I have looked at an extra spindle I have here and can't tell. I'm going to visit a place here locally that analyzes fasteners and show them the bolt and spindle. See if they can test it and come up with a solution.

PM  EMAIL  GALLERY  Attn:RR
01-20-2010 12:07 PM  8 years agoPost 210
stuartmp74

rrApprentice

Gold Coast, Australia

My Posts: All  Forum  Topic

Good on you hanzuki.

what you said is quite right and worth investigating maybe a small hardened washer under the head could do the job as well.

I do not have my 700 LE kit yet but I am thinking I might try and buy a M6 x 35 Unbrako socket cap screw this has a grip length or 11mm (distance from the the head to the first complete thread.)

It also has a a body length of 6mm which is the length of the unthreaded cylindrical portion of the shank.

Then I would cut the length down to 16mm
Once this is done all you need to do is make a flanged bush.

On end of the bush would suit the inside diameter of the spindle shaft and the other end would have flange that would match the Outside diameter of the current screw.

the Id of the flanged bush would match the unthreaded cylindrical portion of the shank of the M6 screw.

I may have to run a tap through the bush so I can get it on to the unthreaded cylindrical portion of the shank of the M6 screw as the diameter of the shank is usually smaller than the tips of the thread.

Can someone measure the length and the diameter of the Collared Portion of the Align Bolt and post it so I can see if my idea will work?

Don't forget the Red loctite

PM  EMAIL  GALLERY  Attn:RR
01-20-2010 12:55 PM  8 years agoPost 211
jschenck

rrProfessor

La Vista, NE.

My Posts: All  Forum  Topic

s it possible that while tightening the bolt, the shouldered part stops going in further because of the 'cup' on the spindle and further screwing causes the bolt to be stretched and thus weakened?
I hadn't thought about that, sure would cause problems. If the shouldered part bottoms out before the head of the bolt is firm against the spindle end that would cause the bolt end to rock and fatigue. Simple fix would be a washer.
Good on you hanzuki.
+1 !!

PM  EMAIL  GALLERY  Attn:RR
01-20-2010 01:11 PM  8 years agoPost 212
Fernando

rrApprentice

Madrid

My Posts: All  Forum  Topic

Is it possible that while tightening the bolt, the shouldered part stops going in further because of the 'cup' on the spindle and further screwing causes the bolt to be stretched and thus weakened?
very good point indeed!!!

PM  EMAIL  GALLERY  Attn:RR
01-20-2010 02:15 PM  8 years agoPost 213
PC12DRVR

rrKey Veteran

USA

My Posts: All  Forum  Topic

I agree that is a possibility as well, and again, it goes back to the tolerances on the bolt and spindle, which falls back in Aligns lap, poor quality.

Putting a washer in would help eliminate this particular possibility, but if the head is not true you are still loading the bolt unevenly creating a radial pre-load, not ideal at all. I still think moving away from the single bolt design to the more traditional bolt/washer is going to be more desireable here.

Its funny how the align reps or rep here on RR can post something about the new 3G FBL to help sell it but reading this they have nothing to say, reps are supposed to help the consumers with issues like this, but not a word yet, just getting ignored. Its BS I don't care how good they fly it doesn't really impress me, what would is for someone from Align jumping in and trying to help stop this from happening again.

PM  EMAIL  GALLERY  Attn:RR
01-20-2010 02:32 PM  8 years agoPost 214
rudyy

rrElite Veteran

E. Amherst, NY

My Posts: All  Forum  Topic

Its funny how the align reps or rep here on RR can post something about the new 3G FBL to help sell it but reading this they have nothing to say, reps are supposed to help the consumers with issues like this, but not a word yet, just getting ignored. Its BS I don't care how good they fly it doesn't really impress me, what would is for someone from Align jumping in and trying to help stop this from happening again.
+1. Very disappointed.

PM  EMAIL  GALLERY  Attn:RR
01-20-2010 03:20 PM  8 years agoPost 215
Thumpernator

rrKey Veteran

Senoia, Georgia, USA

My Posts: All  Forum  Topic

Problem Using a Spacer
Ok. I made a spacer and found another problem. The recess for the shoulder is not centered to the center of the threaded hole. In other words, the spacer would have to be thicker in some areas. So, if you were to bond the spacer to the screw, the spacer would not go into the recess as it turned with the tightening of the bolt. Hope I explained it clear enough.

Anyway, here is another idea that I want to run across you guys before I do it.

Lightly coat a longer bolt with wax (so the JB weld won't stick to it) and run it down into the shaft, but leaving the head away from the shaft. Then take some JB weld and fill in the gap (where the shoulder would go) between the screw and the shaft. Let it cure and then remove the screw. It should make a perfect fit, taking up all the gap, when installing the permanent screw. The JB weld would even have threads in it using this method and there would be zero play for the bolt.

Well, what do you guys think about doing it this way?

Dave
I keep on thinking, but nothing's happening. Knuk, Knuk, Knuk

PM  EMAIL  GALLERY  Attn:RR
01-20-2010 03:37 PM  8 years agoPost 216
CoronaL

rrKey Veteran

Winnebago IL

My Posts: All  Forum  Topic

I think a better idea would be custom spindle shafts that would "carry" out longer and maybe have a machined end or something to neck down, or in place of that, revise the thrust bearings/radial bearings to allow just a straight neck, I dunno what would be better. Then you could use just a standard screw on the end with a washer. Like my Kasama head/grips use. Then you get rid of this necked bolt/screw and possibly these failures.

Randy!!! I am the liquor

PM  EMAIL  GALLERY  Attn:RR
01-20-2010 03:42 PM  8 years agoPost 217
basmntdweller

rrKey Veteran

Indianapolis IN

My Posts: All  Forum  Topic

I have followed this thread from the beginning, read all the theories and discussed them with a couple of the engineers I work with. We all agree that it is just a poor quality bolt. One suggested rigging up a test to check the failure point. Testing 20 or so bolts to failure may give an idea as to the consistancy of the bolts and their actual tensile strength.
In my case, the next time I pull my spindle, I'll replace them with standard SHCS's and a suitable washer. The shoulder on the stock bolt and the mating recess in the spindle serves virtually no purpose. There are no lateral loads on these bolts so the shoulder couldn't possibly add anything structurally. As mentioned before, M5 bolts have proven to be more than sufficient on MA stuff for years so a good M6 SHCS is overkill here.

Matt


Stupid people have no idea how stupid they are!!!

PM  EMAIL  GALLERY  Attn:RR
01-20-2010 03:54 PM  8 years agoPost 218
CoronaL

rrKey Veteran

Winnebago IL

My Posts: All  Forum  Topic

now that would be very interesting.

Taking a sample lot, and putting them in that machine that "stretches" them to failure. Great idea as you would then have data to show the break points and consistency, which I agree would probably be frightening. Some might hold 1000lbs, some might break at 300lbs, some at about 850lbs etc... Those figures are just guesses, but I think you can see the point of some being WAY lower than other's and how that could impact a situation like this.

Randy!!! I am the liquor

PM  EMAIL  GALLERY  Attn:RR
01-20-2010 04:09 PM  8 years agoPost 219
jschenck

rrProfessor

La Vista, NE.

My Posts: All  Forum  Topic

There are no lateral loads on these bolts so the shoulder couldn't possibly add anything structurally.
I am not an engineer by any stretch (bad pun intended) but seems to me there must be some radial/lateral load on these bolts. When we pitch or cyclic on these machines that produces a perpendicular load on the blade grips which must translate to the face of the spindle bolts.

If we are indeed seeing a case where the shouldered part of the bolt bottoms out before the face of the bolts is firmly seated against the spindle then this radial load would cause a bit of flexing on the bolt head which would lead to fatigue and failure.

PM  EMAIL  GALLERY  Attn:RR
01-20-2010 07:25 PM  8 years agoPost 220
PC12DRVR

rrKey Veteran

USA

My Posts: All  Forum  Topic

The radial bearing should be taking all he radial load, the head bolts should only be loaded under tension. Here is my theory.

The Align bolt issue seems to me to be caused by 3 definite factors and one possible, being the shoulder bottoming out before the head seats.

1 The bolts themselves have runout in the head of the bolt, so when
tightened to the inner race of the radial bearing are not seating
evenly so therefore are not distributing the load evenly, creating a
radial load on a bolt that should only be bearing axial/tensional
loads, combine that with poor quality steel the repeated loading
/unloading of the bolt created a small movement (thousandths of an
inch) resulting in fatigue failure. They also have a wobble/off center
movement, to the head when veiwed from overhead.

2. The Align design is too rigid, the bolt/washer combo most commonly
used is better because it allows for less or no trasfer of radial loads tothe bolt head, due to the washer being able to seat more evenly because it is free to move.

3. The Align design of a shouldered bolt was intended to help prevent
radial loads from being tranferred to the bolt head by allowing the
shoulder to support the bolt at the end of the spindle. The poor
tolerances of the spindle cut/ bolt shoulder are not allowing for full
contact insed the spindle wall, this gap is allowing a slight flexing
of the bolt material further accelerating the fatigue propogation.
Additionally if the spindle and bolt mate unevenly this could preload
the bolt with a radial load. In addition the shoulder could be bottoming out in the spindle before the head seats completely.

Thats my opinion and I'm sticking to it

PM  EMAIL  GALLERY  Attn:RR
WATCH
 20 pages [ <<    <     9      10     ( 11 )     12      13     NEXT    >> ] 22941 views TOPIC CLOSED
HomeAircraftHelicopterAlignT-REX 700N › 700 Exploded today/POLL how many have had this happen??
 Print TOPIC  Make Suggestion 

 38  Topic Subscribe

Monday, June 25 - 1:11 pm - Copyright © 2000-2018 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online