Secondary Drive Assembly

This section has turned out to be of chronicle of the secondary drive
and our intention is for it to contain a past to present day format. It's pretty intense and we'll keep adding to it as we find more and more about its history.

If you have any pertinant data to add please send it to us.

It's going to take us some time to get all this information posted this way but once it's finished we'll be able to see just how this unit has performed from as far back as we can find information on it until the present day.

 
Exec 90
A-13

-3

1993?

Exec 90

30

3 Bearing

-

-

-

Chain

N5251B

100

Wiley

NO NTSB

Idaho

It was believed at this time that improper installation was the problem

Exec 90, 162F M-11

Exec, Exec 90,162F
A-26

-1	92 Exec	145	30	3 Bearing	-	-	-	Chain	N71RF	169 hours	Ronald Froberg	NO NTSB	-
1	before 1997	-	30	Double	-	-	-	Chain	-	-	Tom Smith	NO NTSB	Tom told Hans
2	before 1997	-	30	Double	-	-	-	Chain	-	-	Tom Smith	NO NTSB	Tom told Hans

It was believed at this time that improper installation was the problem

3

07/97

-

30

3 Bearing

-

-

-

Chain

C-FMAP

70

Hans Svendsen

NO NTSB

-

It was believed at this time that improper installation was the problem

4

10/98

162

30

Double

-

-

-

Chain

-

-

verbal

-

EPI SITE NO RECORD

5

11/99

162

30

Spherical

-

-

-

Chain

-

-

Steig

NO NTSB

Factory Ship

Not reported to NTSB and no cause listed for this one

Feb 14th 2000

Exec 162F
A-34

The first secondary Drive Shaft break with a Pro Drive Unit installed on a ship belonging to Joe Martain of West Virigina

7	4/6/00	162	30	Double	-	-	-	Chain	N21901	-	NTSB	LAX00LA173	Factory Ship
8	08/00	162	30	Double	-	-	-	Belt	-	-	Verbal	-	EPI SITE NO RECORD
9	09/00	162	30	Spherical	-	-	-	Chain	-	-	Mark Wolf	-	Factory Ship
10	11/00	162	30	Spherical	-	-	-	Belt	-	-	Joe Martin	-	In WV
11	before 1/01	90	30	3 Bearing	Above upper bearing	-	-	Chain	-	-	Craig Hook	-	-

This is a setup or two that someone came up with in an effort to keep the shaft from breaking.

I'm not sure but I think these are fixs either done by Joe Martin or Craig Hook around 2000.

-2	2001	162F	30	Double	-	-	Chain	N864KP	250	Barry Pinnix	NO NTSB	-
12	03/01	90	30	Double	-	-	Belt	-	-----	Craig Hook	-	Terrys Exec 90
13	03/01	?	30	Spherical	-	-	Chain	-	-----	Email	-	Robbin Burrows - Tasmania?
14	03/01	162	30	Double	-	-	Chain	-	51	Rotorheads	-	Duane Grummett/Canada
15	03/01	?	30	Double	Didn't break	Spun upper Bearing	Belt	N124CF	-----	Rotorheads	Scott n Brett Newhart	EPI Showed Break
16	5/16/01	162	?	?	Didn't break	Loose lower bearing	Belt	N311RM	-----	NTSB	CHI01LA141	EPI and Rotorheads Showed Break

On May 2, 2002  Rotorway sent out a bulletin, (A-38) recommending that everyone change over to the New Style 35mm setup they're offering.

On September 27, 2002,
at 45 hours on a new design 35mm shaft there was a failure
the first one known to the public anyway.

17

09/02

162

35

Spherical

Belt

45

Rotorheads

-

McLaughlin

You can check out an engineering report written by Matthew Dock,P.E. on it in the January 2003 addition of RotorHeads Newsletter.
From what I gather RotorWay had an engineering report made which came to the conclusion it was from stress and pointed fingers at the cog belt drive.  Its said there has been at least three 30 mm shafts breaking at the RotorWay factory with chain drives and a few more we've heard of and I think that makes 7 at last count I think.

18	10/1/01	162	30	Double	-	Between  bearings	-	Belt	N8270U	113	Jerry & Linda	NO NTSB	-
19	10/07/02	162	30	Double	Inside the upper bearing race	-	-	Belt	N1955Z	153	Owner	CHI03LA006	Mark Wolf
20	10/19/02	162	30	Double	-	-	-	Belt	N162AZ	-	NTSB	LAX03LA011	Jimmy Johnson Tuscon, AZ

Exec 90, 162F
M-21

21	1/1/03	162	30	Double	1/4 below upper bearing	-	-	Belt	N140GW	16	MSN Site	NO NTSB Pics in File	Tom Uppman
22	2/5/03	90	35	Spherical	Midspan	-	-	Chain	N9876D	561	Bill Cobb	LAX03LA084	Factory Ship
23	07/03	162	35	Spherical	-	-	-	Belt	-	55	Jim Liss	-	-

John had a meeting about the shaft issue

and from what I gathered from it it's now thought that the upper bearing race squeezes the shaft causing it to be larger above and below it. There is also foreign matter falling into the joint where the race meets the shaft helping the race to put an etching so to speak around the shaft. Upon rotation of the shaft, the shaft itself bends a bit thus compressing the foreign debris into the shaft causing it to fatigue to a point where it simply snaps.

This is just a rough way of putting it and everyone concerned needs to put in a call to John Spurling or his engineer to get it correct.

John is proposing that if we send him a new 35mm secondary setup
he will make the necessary fix's and return it better than new and if all goes as planned there won't be any more broken shafts to worry about.

A fellow named Al Behuncik has a cog drive system
that has different sprockets and also uses a different kind of belt.

It's my understanding that Al believes the shaft breakage problem is caused by the tension put on the shaft from the chain/cog drive and that using his system will eliminate shaft breakages providing you use his system.

 Al's setup also uses a tensioner on the left side of the cog belt which maintains a constant 10lbs of pressure on the belt "I think" under what ever power setting you have on the ship at the time.   I got to see one at Homer's in July 2004 in Al's personal helicopter but I didn't get any pictures of it.  It's very hard to obtain any information or pictures of this system because Al doesn't have an Internet site and about all you can do is read tidbits about it here and there.

To Donna and I's knowledge to date there has never been a reported shaft breakage related to Al's system.
That may sound good BUT no one has any idea about exactly how many units Al actually has flying around out there so only time will tell.

This is the way most people are mounting their bearing temperature sensor.

24

07/04

162

30

Double

just below top of lower bearing

-

-

Belt

N162FA

97

Owner

NO

Clell and Donnas Ship

John Spurling of Pro-Drive has something going on now
with a new improved Secondary unit. 

You can learn more about it and get updated information
plus learn about a new product announcement on John's Pro-Drive's site at
http://www.pro-drive.ws/

Pro Drive holds a seminar at Homers July 04 Fly In.

It looks like there's a new kid on the block regarding the secondary shaft breakages

His name is Jack Kane of Epi-eng.  It appears he's come to much the same solutions as John Spurling of Pro-Drive with the exception he's using a different type of metal for the shaft.   Donna and I missed most of his seminar he held at Homer's July 04 Fly-In and that's the jist of the information I received from folks who got to witness the whole thing.  I've looked his site over and read his explanations about it all, but truthfully speaking not being an engineer, most of it goes way over my head so here too, just like you, we're on our own.  Once I get all this information decoded down to my level of thinking I'll post our opinion.

www.epi-eng.com

Page 1

Page 2

A fellow named Bob Carter has a new gizmo
he feels will solve the secondary shaft breakage problem.

Bob was one of the 3 people/companys
that gave a seminar at Homers 2004 Fly-in.

These are Photo's from Pro-Drive's web site of the new Secondary Shaft they have in production now.

At this point there are several of these units out in the world now
and according to John Spurling at Pro-Drive he's sure this new setup has once and for all solved the issue of the secondary shaft breakage issue.

Pro-Drive's new design secondary shaft with 85 hours on it.
You can't even tell it was ever installed.

Pro-Drive 40 mm bearing after 85 Hours       Vs.     RotorWay 35mm bearing after 35 Hours

33 Hours, 35 mm

280 Hours, 30 mm

25 Hours, 35 mm

100 Hours, 35 mm

         photos of unbroken shafts that were disassembled for new secondary upgrades

Jack's been working pretty hard on a new shaft

and it's definitely different than I had imagined from the little I got out of it at the seminar at Homer's.  He's not only using a different type of metal he's also designed all kinds of other ridges and bumps into it.

It's supposed to have something like 3 times the life span of the original RotorWay shaft and two times the life of the Pro-Drive shaft according to the data he has posted on his site.

I couldn't even begin to touch on everything Jack has on his site here so be sure to take some time and check it.

Make sure you have plenty of time to do it to because his site is pretty intense and if your serious about it your going to be at it a long long time lol.  It's worth the time spent because when your finished you'll come away with a much better understanding of what it is that's really going on in our little ships.

As far as the figures Jack has posted in his charts and things you'll just have to trust that they are right unless your already an engineer or you've got time to go to engineering school, it's pretty difficult for the typical layman to comprehend it all, the reason I brought that up is because Jack and John have a different way of arriving at the final figures and If you look at John's Pro-Drive site it all adds up and at the same time you'll see that Jacks figures on his site all add up to.

There's an old joke that says
If you put 5 engineers in the same room, all working on the same project at the same time, they will come up with 5 different answers.
From what we're all witnessing here it's no joke, it's very much the real deal lol.

The only down side about Jack's site is the constant bashing of the Pro-Drive system.

If he follows suit, Al Behuncik's drive system will be the next thing he trashes out all though up to now he seems to give it credit here and there on the site.  To date as far as I know there has never been a shaft of any size on one of Al's setups break so it will be interesting to see what happens.

If I didn't know better I'd say John must have stolen Jack's wife or something, it won't take you long to figure that out on your own.Jack may have a very workable solution going on with his new unit and it's obvious he's no dummy but if he doesn't find a nicer way of getting his message across to people " just like his predecessors in the past" he isn't going to get very far, at least that's the view Donna and I have.

Jack is claiming to have 2 or 3 of these units out in the world

someplace at this time but
for some reason he's keeping it secret as to whos ships they are installed on
not to mention how many hours they have put on them.

www.epi-eng.com

last updated
Nov 2004

Donna's and I's Analysis at this point

To date, according to Jack's site in a table he has posted on shaft breakages, there have been

5 chains
8 belts

plus 4 breakages with unknown drive types
and 2 broken Pro-Drive belts

Adding our ship to the list, what I see in this data is that out of the 13 confirmed broken shafts 8 of them had Pro-Drive units.  Jack has come to the conclusion and is trying to convince us with the aid of a few others like John Rahn from Rotorheads Newsletter that the entire fault has come to rest upon the shoulders of Pro-Drive despite that there were 5 broken chain drive secondary shafts.

I threw that tidbit in there about John Rahn "editor of Rotorheads" because he's had or perhaps is still having a battle with John Spurling going on over some patent rights.  In the November issue of Rotorheads he printed an article of some 8 pages or more in length from Jack Kane about his new secondary shaft design.  It does mention Jack's new design but the majority of the article does nothing more than bash Pro-Drive in every way this fellow could think of.

Now I can see Jack's article being printed "once the bashing was edited out" in Rotorheads but what I can't see is why John Rahn didn't give Pro-Drive a chance to defend itself in the same printing of the newsletter, two months lag time between printings is just way too long to leave people in the dark thinking bad things.

He just flat out used the power of the press to sucker punch Pro-Drive and no matter how you look it, no matter whether it was John Rahn's intent or not, it's nothing but poor journalism any way you look at it and that was the end result of it.

John Rahn in his own defense made a post on the Rotorwayfun.msn site:

Rotorheads invites all points of view from all parties.  We take no "sides" on any issue.  If you don't send us your opinions or articles, we can't print them.  The only information I have received from Pro-Drive was published.  We welcome their opinions as well as all others.  We can't print what we don't have!

I guess John Spurling should have had his crystal ball turned on that day

so he could see the article as it laid on John Rahn's desk.  Maybe if he had he could have responded with his side of the issue but alas he was probably working in his shop or on the phone trying to help someone and missed out on it.

What a bunch of bull!

Anyways on with the subject at hand!

I can't verify it any more than we can seem to verify all these shaft breaks but there is supposed to be in theory somewhere around 500 RotorWays out there "actually flying" around the world.

From what I understand from Pro-Drive they have well over 300 units out there.  If the numbers are correct that means that for every 5 RotorWays out there 3 out of 5 of them are sporting a Pro-Drive unit under their dog house right?

Now we all know that Al Behuncik has units out there too so lets take those out of the factory equation.  Just for chits and giggles since we really have no idea lets say Al has 50 of his units out there running around someplace.

  Let's see 500 - 350 = 150 right?  In simple math and as you can see that leaves us with fewer than 150 factory Chain Drive setups out there

 I'd say with that thought train in your mind you could just throw the other 4 unknown drive type shaft breaks on Ole Pro-Drives back and it wouldn't do anything more than substantiate the fact that there are just as many shafts that break on chains out there as there is belts, at least that's the way I'll see it until someone shows me my figures aren't correct.

Here's another tidbit of thought about Al's system and keep in mind it's just that THOUGHT.  The majority of Al's setups, however many there are, are buzzing around up in Canada somewhere right?  How many good flying days do people have up there compared to the the ships in the lower 48 "below the Canadian southern border"  You can bet if that's true that it's going to take alot more time for those guys to get as many hours on Al's system as there has been on Pro-Drives Systems.  It may not be true but if it is, it's going to be some time before we have any high time stats to work with.

If we look at it in black and white

like that it doesn't take a genius to figure out that
the factory shafts weren't up to par in the first place as far as the two 30mm shaft designs were concerned and we didn't need anyone to tell us that.

Rotorway itself coming out with a new 30mm spherical bearing design was proof in itself that there was trouble but it was blamed on builders not getting the angle on the piller block correct and causing the problem themselves and even more so on the Pro Drive Cog Belt System.

According to RotorWay back in 1999 they changed it to make the builders life easier, not because they were having shaft issues at the factory as well.

Personally I think the communications on the internet is what blew the whistle on them because up until then there just wasn't ever any news of things breaking at the factory.  If you think about it all the information we get on problems is through the net.  I can't personally think of one shaft break or anything else for that matter that was reported to anyone that wasn't either found on or reported on the internet.  Take the stats you have heard about how many people have computers and how many still don't, that will give you some idea as to how much information we don't get and never will until the rest of the world becomes Internet savvy.

Rotorway Via Bill Orth made a post back on November 1st 04 on the Rotorwayfun.msn site saying that they haven't had a 35 mm secondary breakage since "2001" when they came out with their 35mm shaft upgrade and that they feel if you build your ship to factory specs you won't have a problem.  They did have one of the new units fail in April, 2003, but Rotorway attributed it to a tail rotor strike or two and according to them it did in fact break at the bottom end and that is in a totaly different place than all the other breakages they have had at the factory.  If this is in fact true RotorWay has indeed whipped the issue as far as producing a secondary unit that will run in their chain driven 35mm spherical bearing shaft but won't sustain the addition of adding a Pro-Drive unit to your ship.

If you don't mind running the chain drive and putting up with all the issues it creates your all set but if your like Donna and I and you don't want the problems that come along with the chain drive your putting your butt in the same boat as the rest of us and you don't have a choice other than to take your best shot at an aftermarket setup.

What we needed was for someone to make a shaft that was robust enough to work for the Pro-Drive Cog Belt design as well as the Factory Chain Drive for us chickens who think the sky may fall and want that extra edge and that's just what John Spurling at Pro-Drive says he's done.

Shafts were already breaking at the time when John Aka Pro-Drive, came along with an idea in 1997

that got rid of 50 others problems that everyone had in common running the factory chain drive system. Since then he's been getting the shaft on the cog belt system he put out from some folks for trying to help improve our little helicopters.

From what I see Jack aka EPI, just may make a good shaft in the end.

In looking at his new design with all the different machining he building into the shaft plus the fact he's using a different type of steel it is in fact taking the shaft on a diffferent road.  Past shaft breakege history has indicated no issues in the shaft below the pillow block aside from the one that happened at the Rotorway factory back in 2003 that was said to be most likely caused by 2 tail rotor strikes by Rotorway and Fretting corosion by the NTSB Lab in Washington DC.

If the shaft metal is changed were all in a new world as far as the sprag clutch goes and everything else below it right down to the cooling fan.

To me, that puts us all back into the test phase and its possible it could have some future unknown issues.

 
I don't know how everyone does things but I'm a follower of the change one thing at a time rule and see how it goes
and if that doesn't work out try something else but never ever change several things at once or you may never know what caused what to happen to what and most likely well have to back up and start over again.

I think we owe our support to Pro-Drive

not only because of all the R&D time and money he's invested in this project but also for all the flack he's absorbed from the RotorWay Community.  Personally I think John is going about it in the right way, one step at a time and if he's going to be able to keep up with it he's going to need all of us because the market place out there just isn't big enough to support 4 suppliers.

Let's face it folks, John's been in the for front of every issue we've had so far
and while Jack was taking pokes at Pro Drive in the hanger at Homers in July of 2004 there was a ship
right outside the door on the flight line flying on a new 40mm shaft with 85 hours all ready on it at the time. 

Is it going to work? Only time will tell!

-----------------------------------------------------------

I took some heat for having the above statement on here from a fellow with a competitors drive system so I thought I'd elaborate on this statement so it doesn't get taken out of context by anyone else.

  You'll also notice that the figures on how many Pro Drive units that are out there have changed.

The reason for that is since November when I posted the above information I've learned from John spurling that Pro Drive has over 600 Drive Systems out there. That makes the figures above change alot and it's in Pro Drive's favor because it makes there system look even better then it did before.

 
----------------------------------------------------------------
Question:              You ask that everyone support one supplier
----------------------------------------------------------------

My Answer:

I never asked folks to support one supplier.  I said I think we owe our support to Pro-Drive because of all the R&D time and money he's invested in this project not to mention all the flack he's absorbed from the RotorWay Community.
John has put his heart and soul not to mention his reputation and wallet into this issue just like he does with everything else he’s been involved in.

My first thoughts on the subject is there is always room for more competition in the world which in itself promotes advancement of  ideas and products

but lets face it there is a very small market out there and this is a very important issue were into.

EPI has a few drives out there, 2 that we know of.
Al has several drives out there around the world, 46 in fact, he told me in December 2004. 
John Spurling claims to have over 600 units out there around the world.  

Looking at the numbers, which one do you think were going to get the most data, good or bad, from first?

I didn’t put RotorWay themselve's into the equation at all because we not taking about chain drives here but if we were they are the only ones that have the high numbers out in the real world to compare to the cog belts.

As far as Cog belts go, Pro-Drive has 92.5% of the Cog belt market out there
Al has 7.2% and
EPI is ringing in with a whopping 0.3 % at the moment and still riding on Pro-Drives Belt System.

Hummm!............here's a good question!

As bad as Jack at EPI trashed out the Pro-Drive system I wonder why he choose to prototype his new shaft on 2 ships with Pro-Drives Belt systems as opposed to installing them with Behuncik's Belt system???

Heres something else we have to consider you sure ain't gonna like.

Pro Drive came out with their cog belt system in October of 97 right?

 
Looking at the shaft break data charts we made
it shows that the first broken secondary shaft on Pro Drive's system happened some 3 years (37 months) after the first one was sold, right?.

In November of 2000 when that first shaft broke with a Pro-Drive Cog belt system on it, Pro Drive had sold over 200 units out in the world.

200 drives over a period of 37 months 10/97 to 11/2000 = 1st broken shaft that was running a Pro Drive

1 Cog belt driven shaft broke in 2000

2 Cog belt driven shafts broke in 2001

3 Cog belt driven shafts broke in 2002

3 Cog belt driven shafts broke in 2003

1 Cog belt driven shafts broke in 2004

Behuncik only has 46 of his drives out in the world.

Al Says he sold 46 drives over a period of 12 months (january 04 to Jan 05)  =  so far No reported breaks running his system.

Looking back at our chart again

It may take several years to find out if the first ones make it
and with a less then 1/4 of what Pro Drive had out there at the time it maybe even longer
before we actualy see any breakeges on this system.

Thinking about this thing in the big picture,

it's my belief

that if each of these aftermarket guys gets 1/3 of the market on this limited sale item there won't be enough profit left over for any of them to continue R&D,  not to mention with 4 different systems out there the compairing apples to apples concept will be out the window. I don't know about the rest of you but Donna and I want to start flying our ship again with a cog belt and with confidence and we want to do it as soon as possible and thats going to take numbers and so far the quickest place were going to get them is from the Pro Drive system because not only do they hold the biggest share of the market but they seem to be the only ones who seem to be up front with information and aren't hiding there data like the EPI folks have done so far.  Pro Drive also came up with this fix back in late summer of 2003 so they are well over a year ahead of the rest of the pack.

Rotorway says they are confident that if the ship is flying with there new 35mm shaft with a chain
there won't be any more secondary shafts breaks

but at the same time it’s obvious that RotorWay isn’t going to get in any hurry to help these guys out by producing a better shaft and put themselves out of the money making chain drive business, heck I probably wouldn’t either if was my bank account but then again even with all that money I couldn’t handle it being on my conscience but that’s just me.

october 2004

Broken_Secondary_Data_FIle

This above link will take you to our data page which is where we obtained this information

#	Date	Ship Type	Shaft Size	Bearing Type	Break Location	Bearing Failure	Bearing Seal Failure	Drive	Reg#	Shaft Hours	Source	NTSB	Comments
-5	2000 ?		30	-	-	Bearings failed	-	Chain	N728PC	300	James Karmy	MSN Site 1/18/05	Stock Ship in Oregon
-4	2000 ?		30	3 Bearing		Bearing failure		Chain	OY-HJS	120	Jorgen Skov Nielsen	MSN Site 1/18/05	Stock Rotorway ship in Denmark
-3	1993?	Exec 90	30	3 Bearing	-	-	-	Chain	N5251B	100	Wiley	NO NTSB	Idaho
-2	2001	162F	30	Double	-	-	-	Chain	N864KP	250	Barry Pinnix	NO NTSB	-
-1	92 Exec	145	30	3 Bearing	-	-	-	Chain	N71RF	169	Ronald Froberg	NO NTSB	-
0	3/30/94	145	30	3 Bearing	-	-	-	Chain	N71RF	41	Ronald Froberg	NO NTSB	-
1	before 1997	-	30	Double	-	-	-	Chain	-	-	Tom Smith	NO NTSB	Tom told Hans
2	before 1997	-	30	Double	-	-	-	Chain	-	-	Tom Smith	NO NTSB	Tom told Hans
3	07/97	-	30	3 Bearing	-	-	-	Chain	C-FMAP	70	Hans Svendsen	NO NTSB	-
4	10/98	162	30	Double	-	-	-	Chain	-	-	verbal	-	EPI SITE NO RECORD
5	11/99	162	30	Spherical	-	-	-	Chain	-	-	Steig	NO NTSB	Factory Ship
6	1/4/00	90	30	Spherical	Immed. below the upper bearing race at the shoulder that is machined into the shaft	-	-	Chain	N89678	-	NTSB & Ron Curry	LAX00LA071	Factory Ship
7	4/6/00	162	30	Double	-	-	-	Chain	N21901	-	NTSB	LAX00LA173	Factory Ship
8	08/00	162	30	Double	-	-	-	Belt	-	-	Verbal	-	EPI SITE NO RECORD
9	09/00	162	30	Spherical	-	-	-	Chain	-	-	Mark Wolf	-	Factory Ship
10	11/00	162	30	Spherical	-	-	-	Belt	-	-	Joe Martin	-	In WV
11	before 1/01	90	30	3 Bearing	Above upper bearing	-	-	Chain	-	-	Craig Hook	-	-
12	03/01	90	30	Double	-	-	-	Belt	-	-----	Craig Hook	-	Terrys Exec 90
13	03/01	?	30	Spherical	-	-	-	Chain	-	-----	Email	-	Robbin Burrows - Tasmania?
14	03/01	162	30	Double	-	-	-	Chain	-	51	Rotorheads	-	Duane Grummett/Canada
15	03/01	?	30	Double	Didn't break	Spun upper Bearing	-	Belt	N124CF	-----	Rotorheads	Scott n Brett Newhart	EPI Showed Break
16	5/16/01	162	?	?	Didn't break	Loose lower bearing	-	Belt	N311RM	-----	NTSB	CHI01LA141	EPI and Rotorheads Showed Break
17	09/02	162	35	Spherical	-	-	-	Belt	-	45	Rotorheads	-	McLaughlin
18	10/1/01	162	30	Double	-	Between  bearings	-	Belt	N8270U	113	Jerry & Linda	NO NTSB	-
19	10/07/02	162	30	Double	Inside the upper bearing race	-	-	Belt	N1955Z	153	Owner	CHI03LA006	Mark Wolf
20	10/19/02	162	30	Double	-	-	-	Belt	N162AZ	-	NTSB	LAX03LA011	Jimmy Johnson Tuscon, AZ
21	1/1/03	162	30	Double	1/4 below upper bearing	-	-	Belt	N140GW	16	MSN Site	NO NTSB Pics in File	Tom Uppman
22	2/5/03	90	35	Spherical	Midspan	-	-	Chain	N9876D	561	Bill Cobb	LAX03LA084	Factory Ship
23	07/03	162	35	Spherical	-	-	-	Belt	-	55	Jim Liss	-	-
24	07/04	162	30	Double	just below top of lower bearing	-	-	Belt	N162FA	97	Owner	NO	Clell and Donnas Ship
25	5/15/05	162	35	Single	Just above pillow block	-	-	Chain & Belt		65 on chain 72 on Pro Drive belt TT=137 on factory 35mm shaft	Owner	NO	Owner of ship Jack Elvin reported this on RotorwayFun.MSN site

Total Number of Broken Shafts including Shafts with Spun Bearings

Broken Shafts on Chain Drives Total	16
Broken Shafts on Cog Belt Drives	10
Spun Bearings	4
Total of broken shafts and shafts with spun bearings	30

Broken Shafts Not including Spun Bearings

Drive Type	Total Chain	Total  Belt
30mm 3 Bearing Units	5	0
30mm Double Bearing Units	6	7
30mm Spherical Units	4	1
35mm Spherical Units	1	2

 
Unless we have some of our data screwed up it would appear that the
30mm double bearing once thought to be the safer shaft setup is definitely the most likely to break,
but then again during that era it was everyones belief that it was safer and more people choose to ride on that setup
not to mention the fact that the 30mm 3 bearing and the 30mm double bearing happened to be the majority of units running around out there so that may be what the numbers are reflecting.

Total Combined Number of breaks with Chains and Pro-drive Cog Belts

30mm 3 Bearing Units totals	5
30mm Double Bearing Units Totals	13
30mm Spherical Totals	5
35mm Spherical Units Totals	3

Things are either getting better or folks have their ship in dry dock

because of a fear there seconday will break and there just aren't as many ships out there flying.  We'll just have to wait and see what happens now with the new 40mm system Pro Drives has put out on the market.

It's also a possibilty that with all the attention the secondary shafts have gotten that people are paying much more attention while installing their secondarys.

So Far out here in the real world

On chain and belt systems we have seen shaft breaks in a range of 16 to 250 hours.  I know of a few ships that are in the 300 to 600 hours range and are still riding on there 30mm doubles so there isn't much to go on as far as making any sense out of it all other then these numbers were coming up with.

 
Rotorway claims to have put a total of 561 hours in shaft break number 22's report
and compairing it to what shaft hour data we have collected so far that's pretty hard to believe but at the same time assuming those hours are on the newer 35mm spherical shaft its looking alot better for the guys running chain drives,
well maybe it is, but then again, maybe it's not.

 
This NTSB Report on this break really bothers me but doesn't seem to concern anyone else.
Keep in mind it's implied that the break is blamed on two tail rotor strikes that were written up in the ships log

The Safety Board Materials Laboratory, Washington, DC, examined the secondary drive shaft, and prepared a factual report. The secondary drive shaft fractured between the lock collar (located just above the tail rotor drive belt pulley) and the inner race of the lower bearing. The lock collar was held onto the shaft by a set screw, and the lower bearing had been assembled with Locktite between the inner race and the secondary shaft. Examination of the shaft in the area contacted by the lock collar (on the lower portion of the shaft) revealed fretting and corrosion that was primarily concentrated in two circumferential bands. One was associated with the upper edge of the lock collar, and one was associated with the lower edge of the lock collar. Examination of the mating faces of the shaft fracture revealed that almost the entire fracture surface was on a flat plane. It intersected the exterior surface of the shaft at a 90-degree angle, and most of the fracture contained crack arrest positions, indicative of fatigue cracking. The origin area was at the lower edge of the fretting and corrosion area on the inner race of the lower bearing. The way I read it the description of the break it sounds exactly like the breaks that have been happening in every other instance of shaft failures we know about EXCEPT that it broke in a different place. Unless we did the math wrong it states the ship flew 126 hours after the 1st tail rotor strike It then flew another 133 hours after the 2nd tail rotor strike which is a total time of 259 hours with a cracked shaft?. Heres what I got from it all 259 hours after the first tail rotor strike and 133 hours after the 2nd tail rotor strike the 35mm spherical shaft was most likely the result of tail rotor strikes. 133 hours is a long time to fly with a cracked shaft isn't it? The break its self looks just like all the rest.  The report says it's a 90 degrees flat angel break and that it was smooth which suggests a large fatigue zone. All we need to do now is read the last part of the report which says The origin area was at the lower edge of the fretting and corrosion area on the inner race of the lower bearing. Its that freating and corision part that has me hung up since thats what a few folks are pointing there fingers at, is it just a  coincidence?. It's also my understanding that there is hardly any load at all on the bottom of that shaft so once again I can't point my finger at load being an issue and with that ship flying that many hours I can't go with the tail rotor strike idea either. Take a good look here because that report didn't come from Gate's, Pro Drive, EPI or Rotorway, it came straight from The Safety Board Materials Laboratory in Washington, DC and in the end of the final report there is no mention what so ever of a tail rotor strike being the cause. They don't have a dog in this secondary battle and they have all the money in the world not to mention the top dogs in their field as far as investigators and parts examiners go, well at least we think they do lol

January 5th 2005