RunRyder RC
WATCH
 6 pages [ <<    <    ( 1 )     2      3     NEXT    >> ] 5638 views POST REPLY
HomeAircraftHelicopterHelicopter Main Discussion › This is why Align 700N clutch fails
09-20-2013 02:55 AM  5 years agoPost 1
red_z06

rrProfessor

Dumont, NJ

My Posts: All  Forum  Topic

If you have owned and flown Align 700N, you would have experienced the cluch wing fractures. Stock clutch and the stock clutch liner has 0.015 gap between them. I decided to look into the mechanism behind the failure by doing FEA analysis on the Align clutch.

The pictures below show exaggerated deflection to show what parts are bending. The pictures on the left are the stress levels and the pictures on the right show how much the wings are defroming when spun. Normal structural steel has typical tensile stress limit of 75,000psi and some high carbon steel can get to 150,000psi after heat treatment.

These values are when the part fails under a one time load. But, steel has fatique stress limits that are far below these values and are typically around 1/2 of the one time load. Fatigue stress comes into play when the part is subjected to loads that vary or cyclic in nature. Internal combustion engines in general go through acceleration and deceleration during a single revolution which contributes to the cyclic load or vibrational load on the clutch. The other component that causes cyclic load is due to the fact that the engine axis and the clutch bell housing axis typically are not perfectly aligned.

Typically, fatigue limit is when the part under goes the cyclic load of 100,000 cycles and survive. If a hardened steel has a tensile strength of 100,000psi then that metal will typically have fatigue limit of 50,000psi. So, if the part is subjected to 100,000psi, it will fail within few cycles and if it is subjected to 75,000psi then it will fail after some time. If it is subjected to 50,000psi or lower, it would not fail at all.

The colors on the pictures have coresponding numbers. For the 0.015 gap between the parts, the clutch will have to contact last 1/3 of the wing before it stops slipping and grip tight. At this state, the tip will see about 0.020inch deflection and stress of 75,000psi. Without knowing the carbon content of the Align clutch and heat treatment, I will assume about 100,000psi for the part.

Clearly, the part will fail because it is somewhere in the middle between one time limit and fatigue limit.

For this part to survive long use, the tip of the wing show not be deflected more than 0.010 or the 1/3 point at 0.007 or so. At this point, it sees 38,000 psi at the bending location and any type of heat treated steel would fair well and have long service life.

So, if you can replace the liner to have 0.007inch gap between the clutch and the liner, and the engine exis and the bell housing axis line up well, the clutch should last long time. This of course assumes that the bell housing is thick enough to resist deformation when the clutch pushes againt it and the liner wear does not cause additional deflection of the clutch wing.

Later, I will look at options to make the Align clutch last much longer than it has, by reducing the stress under the same deflection.

Below is the stock clutch gap of 0.015

https://fbcdn-sphotos-e-a.akamaihd....653375230_o.jpg

Below is the clutch gap of 0.007

https://fbcdn-sphotos-c-a.akamaihd...._75356755_o.jpg

Only way to reduce stress is the thin the area pointed by the two arrows. But, if you reduce this area alone, the sectional MOI that resists bending is reduced causing the wings to spread too early.

Ideally, you want to restore the MOI by increaing the height of the clutch. But, this will require redesign of the clutch. So, I'll look at reducing the mass of the wing to reduce the deflection to be the same before the pivot point thickness reduction and at the same rpm.

https://fbcdn-sphotos-f-a.akamaihd....398874638_o.jpg

www.JustinJee.com

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
09-20-2013 03:02 AM  5 years agoPost 2
Carey Shurley

rrElite Veteran

Orlando, FL - USA

My Posts: All  Forum  Topic

how about this one:

http://www.lynxheli.com/product_inf...oducts_id=22165

it should fit any 700n setup

Proprietor - Gas Powered Helicopters

PM  EMAIL  GALLERY  Attn:RR  Quote
09-20-2013 03:04 AM  5 years agoPost 3
TMoore

rrMaster

Cookeville, TN

My Posts: All  Forum  Topic

Every T700/600 that I've built has had a relined clutch bell that I machine myself.

Delayed Response Operator Not Engaged
AMA SECTION 336 = Good
Drones = EVIL

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
09-20-2013 03:07 AM  5 years agoPost 4
red_z06

rrProfessor

Dumont, NJ

My Posts: All  Forum  Topic

Carey,

That failed also. Which is why I started the investigation. On that one, it did not fail at the pivot point but at the base due to the spot face done to clear the screw head.

www.JustinJee.com

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
09-20-2013 03:08 AM  5 years agoPost 5
red_z06

rrProfessor

Dumont, NJ

My Posts: All  Forum  Topic

Every T700/600 that I've built has had a relined clutch bell that I machine myself.
I have not owned a single 600N. Does this one fail too?

Even with the machined liner, the clutch design does not allow much wear on the liner. A good design should allow at least 1/2 the thickness of the liner to be used up without failing.

www.JustinJee.com

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
09-20-2013 03:09 AM  5 years agoPost 6
Doublah

rrKey Veteran

USA

My Posts: All  Forum  Topic

red z06

Very well done!!

PM  EMAIL  GALLERY  Attn:RR  Quote
09-20-2013 03:12 AM  5 years agoPost 7
Carey Shurley

rrElite Veteran

Orlando, FL - USA

My Posts: All  Forum  Topic

really? very interesting

Proprietor - Gas Powered Helicopters

PM  EMAIL  GALLERY  Attn:RR  Quote
09-20-2013 03:14 AM  5 years agoPost 8
TMoore

rrMaster

Cookeville, TN

My Posts: All  Forum  Topic

The clutch clearance is wrong on both the 600 & 700.

Delayed Response Operator Not Engaged
AMA SECTION 336 = Good
Drones = EVIL

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
09-20-2013 03:18 AM  5 years agoPost 9
red_z06

rrProfessor

Dumont, NJ

My Posts: All  Forum  Topic

The clutch clearance is wrong on both the 600 & 700.
I would modify this and say "for the stock clutch design".

You can make the clutch to work with 0.015 start and possibly to more than 0.025 by reducing the stress at the pivot point.

www.JustinJee.com

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
09-20-2013 03:20 AM  5 years agoPost 10
Tyler

rrElite Veteran

Chicagoland area

My Posts: All  Forum  Topic

My original T700N clutch is five years old and has never broken. I bought two spares just because of all the complaints. They are still in inventory.

Enjoy things that money can buy IF you don't lose the things money can't buy.

PM  EMAIL  GALLERY  Attn:RR  Quote
09-20-2013 03:23 AM  5 years agoPost 11
red_z06

rrProfessor

Dumont, NJ

My Posts: All  Forum  Topic

My original T700N clutch is five years old and has never broken. I bought two spares just because of all the complaints. They are still in inventory.
That is great.

How many flights? One of them seem to go around 50-70 flights and the other around 150-200 flights between failures.

www.JustinJee.com

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
09-20-2013 03:27 AM  5 years agoPost 12
TMoore

rrMaster

Cookeville, TN

My Posts: All  Forum  Topic

This is an old clutch design. Clearance has always been a critical issue to longevity.

Delayed Response Operator Not Engaged
AMA SECTION 336 = Good
Drones = EVIL

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
09-20-2013 03:29 AM  5 years agoPost 13
red_z06

rrProfessor

Dumont, NJ

My Posts: All  Forum  Topic

This is an old clutch design. Clearance has always been a critical issue to longevity.
Do you mean the model above? This was ordered and received two days ago.

www.JustinJee.com

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
09-20-2013 03:33 AM  5 years agoPost 14
TMoore

rrMaster

Cookeville, TN

My Posts: All  Forum  Topic

What I'm saying is that in general the T700 clutch is an old design.

Delayed Response Operator Not Engaged
AMA SECTION 336 = Good
Drones = EVIL

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
09-20-2013 03:36 AM  5 years agoPost 15
Tyler

rrElite Veteran

Chicagoland area

My Posts: All  Forum  Topic

Mine has hundreds of flights, but I admit that I don't spool up aggressively.

Enjoy things that money can buy IF you don't lose the things money can't buy.

PM  EMAIL  GALLERY  Attn:RR  Quote
09-20-2013 03:40 AM  5 years agoPost 16
Glenn Goodlett

rrApprentice

California

My Posts: All  Forum  Topic

Your findings seem to support the idea I have stated previously, which was all of the Trex 700 clutches have a finite life no matter how they are treated. A good one seems to last 6 months regardless of brand. I have had them last less than 20 flights also. They always break in the same place. Also check the Quick UK brand, they are a little different and seem to last slightly longer.

PM  EMAIL  GALLERY  Attn:RR  Quote
09-20-2013 03:42 AM  5 years agoPost 17
Glenn Goodlett

rrApprentice

California

My Posts: All  Forum  Topic

Also I've always wished that someone would come out with an aftermarket clutch with hinged shoes and springs. They always break at the worst of times.

PM  EMAIL  GALLERY  Attn:RR  Quote
09-20-2013 03:58 AM  5 years agoPost 18
red_z06

rrProfessor

Dumont, NJ

My Posts: All  Forum  Topic

Also I've always wished that someone would come out with an aftermarket clutch with hinged shoes and springs. They always break at the worst of times.
Stay tuned.

I will have a design mod that will reduce the stress enough to make it last much longer.

www.JustinJee.com

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
09-20-2013 04:02 AM  5 years agoPost 19
red_z06

rrProfessor

Dumont, NJ

My Posts: All  Forum  Topic

Mine has hundreds of flights, but I admit that I don't spool up aggressively.
If the clutch bell was rigid that does not become oblong when the clutch wings spread, it will not depend on RPM.

But, higher RPM will cause the clutch bell to become out of round causing the wings to spread further. So, if you were flying at lower RPM, less stress would be seen by the clutch.

I have not analyzed the clutch bell so this is only a guesstimate.

www.JustinJee.com

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
09-20-2013 04:06 AM  5 years agoPost 20
TMoore

rrMaster

Cookeville, TN

My Posts: All  Forum  Topic

Benny makes a good point about bell distortion because the first Schluter clutch bells were stamped steel.

Delayed Response Operator Not Engaged
AMA SECTION 336 = Good
Drones = EVIL

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
WATCH
 6 pages [ <<    <    ( 1 )     2      3     NEXT    >> ] 5638 views POST REPLY
HomeAircraftHelicopterHelicopter Main Discussion › This is why Align 700N clutch fails
 Print TOPIC  Make Suggestion 

 16  Topic Subscribe

Sunday, November 18 - 3:29 am - Copyright © 2000-2018 RunRyder   EMAILEnable Cookies

The RC discussion world needs to consolidate. RR is now one choice for that. Its software is cutting edge. It hosts on-topic advertising. Help RR increase traffic buy making suggestions, posting in RR's new areas (sites) and by spreading the word.

The RunRyder Difference

• Category system to allow Rep/Vendor postings.
• Classifieds with sold (hidden) category.
• Classifieds with separate view new.
• Answer PMs offsite via email reply.
• Member gallery photos with advanced scripting.
• Gallery photo viewer integrated into postings.
• Highly refined search with advanced back end.
• Hosts its own high end fast response servers.
• Hosts thousands of HD event coverage videos.
• Rewrote entire code base with latest technology.
• No off-topic (annoying) click bait advertising.
Login Here
 New Subscriptions 
 Buddies Online