Matronics Email Lists :: View topic

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

CKT exhaust cracks

Matronics Email Lists Forum Index -> Europa-List

View previous topic :: View next topic

Author Message

JonathanMilbank

Joined: 14 Apr 2012
Posts: 384
Location: Aberdeen area

Posted: Mon Aug 22, 2022 10:53 am Post subject: CKT exhaust cracks

After less than 50 hours since buying a replacement exhaust header tube from CKT for #3 cylinder, it has cracked almost completely around at the level where the loop attachments for the springs are welded on. Considering that this is the second time that such cracking occurs in the same location on both old and replacement tubes, it's reasonable to assume that it will happen repeatedly.



This time I'll get the crack welded, but I anticipate that the crack will just appear sooner than before, due to added welding stresses in the metal.



The carburettors are electronically balanced, the Airmaster propeller is well balanced and the engine supporting rubber dampers show no sign of sagging due to age. The whole assembly flies as smoothly as ever.



So who has similar problems with CKT exhaust systems and what has anybody done previously to prevent cracking?

fireflier

Joined: 24 Jun 2012
Posts: 58

Posted: Mon Aug 22, 2022 11:21 am Post subject: CKT exhaust cracks

Hi Jonathan



I hope your well?   I have had many similar problems with the exhausts pipes cracking, around the area where the loops Are welded For the exhaust springs. 



CKT have been very good and replaced some of my down pipes,  with some conversation with Tim Piper at CKT about the problems  he suggested having the down lipes with the new spigot inserts attached, therefore the newest down pipes I received have got these spigots attached to the ends which fit inside the exhaust outlets on the heads, this is on the 2 rear down pipes. In my opinion with the new spigots attached the downpipes sit better and i feel it helps removes some strain and stress on the down pipes and hopefully reduces the possibility of failure.  



So far so good with mine now,  although I haven’t done many flying hrs since installing them along with a new silencer which i had fail around the welds. 



Kind regards

Donald

G-PUPY 



Sent from my iPhone



 	  Quote: 	
		   On 22 Aug 2022, at 19:54, JonathanMilbank <jdmilbank(at)yahoo.co.uk> wrote:

 

 

 After less than 50 hours since buying a replacement exhaust header tube from CKT for #3 cylinder, it has cracked almost completely around at the level where the loop attachments for the springs are welded on. Considering that this is second time that such cracking occurs in the same location on both old and replacement tubes, it's reasonable to assume that it will happen repeatedly.

 

 This time I'll get the crack welded, but I anticipate that the crack will just appear sooner than before, due to added welding stresses in the metal.

 

 The carburettors are electronically balanced, the Airmaster propeller is well balanced and the engine supporting rubber dampers show no sign of sagging due to age. The whole assembly flies as smoothly as ever.

 

 So who has similar problems with CKT exhaust systems and what has anybody done previously to prevent cracking?

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=507747#507747

_________________
Fireflier

JonathanMilbank

Joined: 14 Apr 2012
Posts: 384
Location: Aberdeen area

Posted: Mon Aug 22, 2022 11:37 am Post subject: Re: CKT exhaust cracks

Hi Donald,



Sadly it's the replacement down pipe with the new spigot insert which cracked again in the same location, after less than 50 hours of operation.



Thanks for the quick reply.



Jonathan

fireflier

Joined: 24 Jun 2012
Posts: 58

Posted: Mon Aug 22, 2022 12:04 pm Post subject: CKT exhaust cracks

Hi Jonathan



Sorry to hear that it was a down pipe with the spigot, I honestly thought the spigot would help solve the problems. I will inspect my aircraft downpipes again soon and watch for any signs of failure then.  Thanks for the heads up. 



I wonder if the downpipes are dip cooled once the loops are welded on?  Or are they left to naturally cool? 



Regards

Donald



Sent from my iPhone



 	  Quote: 	
		   On 22 Aug 2022, at 20:38, JonathanMilbank <jdmilbank(at)yahoo.co.uk> wrote:

 

 

 

 Hi Donald,

 

 Sadly it's the replacement down pipe with the new spigot insert which cracked again in the same location, after less than 50 hours of operation.

 

 Thanks for the quick reply.

 

 Jonathan

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=507749#507749

_________________
Fireflier

JonathanMilbank

Joined: 14 Apr 2012
Posts: 384
Location: Aberdeen area

Posted: Mon Aug 22, 2022 1:13 pm Post subject: Re: CKT exhaust cracks

Someone who shares my aircraft and has another hobby, racing small "super go-karts" with 180 hp motorcycle engines, tells me that the car racers de-stress their axles by getting them professionally heated to "ridiculous" centigrade and then let them cool under computer controlled conditions, a few degrees at a time over several days.



I'm tempted to do this when I have to weld my tube again after it cracks, but the cost might be "ridiculous" £££s.

Area-51

Joined: 03 May 2021
Posts: 377

Posted: Mon Aug 22, 2022 5:24 pm Post subject: Re: CKT exhaust cracks

You may want to review your bolt-up method as the result is repeating... the rear headers should be attached loosely prior to fitting muffler then front headers; give it all a jiggle and wiggle when loosely attached and tighten all the headers gradually after fitting springs giving an occasional jiggle and wiggle as the headers are tightened; this de-stresses the exhaust system and prevents symptomatic cracking and leaking seats at the cones; a very thin smear of copperseal anti-seize on the sealing face of each cone can aid alignment and will burn off fairly quickly on startup (not always required), copperseal each header stud and nut too (it is a high temperature paste and will remain intact to aid periodic service removal)(the stud nuts are reusable and require a lite re-crush in a vice applied to the lock ring)(studs should have a thread die run over them before refitting nuts). A thin smear of Maniseal or similar exhaust sealer in the muffler union pipes can aid gas sealing and will provide enough lead time to position exhaust system before setting; dags can be brushed off after drying. Grinding off the spring loop and TIG welding a strap over the crack repair area before welding the loop back on should add sufficient material strength to prevent further cracking.



Occasionally a stud will screw out of the head leaving nut attached; fit a new stud or secure stud in a large vice between copper sandwich and carefully work seized nut off the stud with Wurth Rostoff. Clean the stud with a thread die and refit and re-torque into the cylinder head. Run an intermediate thread tap through the nut and re-crush locking ring before refitting.... Sometimes the nut just won't budge; put a flame on it until its blood red then unscrew while hot and keep it hot as its being unscrewed.



That's the whole gamut of working with and servicing exhaust systems.

JonathanMilbank

Joined: 14 Apr 2012
Posts: 384
Location: Aberdeen area

Posted: Tue Aug 23, 2022 3:07 pm Post subject: Re: CKT exhaust cracks

The exhaust tube/header/pipe/whatever was welded and has been refitted with utmost care to ensure that there are no undue stresses imposed by misalignment or "struggles" with the rest of the CKT exhaust system. CKT considerately includes a sliding telescopic joint on #1 tube, which should be loosened and free to slide while securing everything, then clamped up last.



The fracture was circumferential on #3 tube, at the level of the spring loop welds and I guess that is where the next fracture will occur. This is exactly where the original fracture appeared and so I believe that two tubes doing the same thing is a good basis for supposition. I've made a "containment device" by using a jubilee clamp with a 1 cm wide strap, notching the strap halfway across in two places to accommodate the tops of the spring loops and tightening it to cover over most of the welded crack. This can be loosened periodically to inspect for further cracking and hopefully will keep the fractured ends aligned if the weld should fail.



Jubilee clamps can be really useful with exhaust tubes and I used a couple with my original Europa exhaust to securely clamp short strips of steel with suitable holes as replacement for welded loops which broke off.



My ruse for preventing springs from breaking is to cut a length of metal brake tube to fit inside each spring, fold an 18" piece of locking wire in half and pass the folded end twice through the brake tube, leaving enough length to fit over a spring anchor point, install the spring fully and then secure the two cut ends of the locking wire through the spring loop.



Now take another 18" or so of locking wire and wrap it twice around the middles of both springs either side of the exhaust tube, squeeze the springs in towards the tube and twist together the ends of the wire to keep the springs curving in somewhat towards the tube.



Finally run a bead of red high temperature silicone down the lengths of both springs on the sides furthest away from the exhaust tube. Leave to cure for about 3 days before starting the engine. More than 100 hours for me so far without repetition of broken springs. My theory is that wrapping wire completely around the middles of both springs changes their resonance into something less destructive and the silicone helps to dampen vibrations.

Last edited by JonathanMilbank on Wed Aug 24, 2022 2:20 am; edited 1 time in total

Area-51

Joined: 03 May 2021
Posts: 377

Posted: Tue Aug 23, 2022 5:25 pm Post subject: Re: CKT exhaust cracks

Lockwire on the exhaust springs sounds like a good idea!



181's 912 has a CKT system fitted; 300hrs no issues...

hanaperrod

Joined: 21 Oct 2013
Posts: 11
Location: Isle of wight

Posted: Wed Aug 24, 2022 1:55 am Post subject: Re: CKT exhaust cracks

I too have had the same problems with my CKT exhaust system. #3and4 stubs badly cracked, #4 replaced #3 welded 100hrs + still ok. as for the springs!!

I seem to be forever replacing them. I'll try Johnathan's idea with the hope it works on my A/C. Worth mentioning that all for stubs have different lengths

between the mounting loops. #1 being longest .Surely there should be an optimum distance for all the stub loops/box?

Burrilla

Joined: 25 Apr 2015
Posts: 182

Posted: Wed Aug 24, 2022 2:45 am Post subject: CKT exhaust cracks

I don’t have a CKT exhaust however the springs on mine are commonly called Trailer Springs and work in compression rather than tension.



I note a lot of spring issues appear to be with the tension type.



Alan



Sent from my iPad



 	  Quote: 	
		   On 24 Aug 2022, at 10:56, hanaperrod <gilrod(at)tiscali.co.uk> wrote:

 

 

 

 I too have had the same problems with my CKT exhaust system. #3and4 stubs badly cracked, #4 replaced #3 welded 100hrs + still ok. as for the springs!!

 I seem to be forever replacing them. I'll try Johnathan's idea with the hope it works on my A/C. Worth mentioning that all for stubs have different lengths

 between the mounting loops. #1 being longest .Surely there should be an optimum distance for all the stub loops/box?

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=507761#507761

JonathanMilbank

Joined: 14 Apr 2012
Posts: 384
Location: Aberdeen area

Posted: Wed Aug 24, 2022 4:06 am Post subject: Re: CKT exhaust cracks

I just LOVE those compression springs and never had one break on a previous exhaust system. The problem with CKT headers/tubes is that the attachment loops welded to them are closed i.e. they don't allow the compression spring loops to be hooked on. I wonder if there are compression springs with open hooks? Or maybe link the end of the spring and the closed loop with something?

Area-51

Joined: 03 May 2021
Posts: 377

Posted: Wed Aug 24, 2022 6:38 am Post subject: Re: CKT exhaust cracks

This is fascinating... outside the box; why even use springs? Why not just try lockwire instead? 🤷🏼‍♂️ And is it the expansion contraction of the loop itself that is possibly causing the fatigue crack?? If the loops have no set distance apart then spring tensions will be all over the place; so are the higher or lower tensioned spring loops cracking? Additionally there is no support fixing on many of these rotax 912 muffler boxes; all the modal energy generated is transfered directly through the header pipes; this is just nuts 🤷🏼‍♂️

wdaniell.longport(at)gmai
Guest

Posted: Wed Aug 24, 2022 7:21 am Post subject: CKT exhaust cracks

i dont have anything on my Colombian homemade stainless exhaust joints....



no leaks



William Daniell

+1 786 878 0246



On Wed, Aug 24, 2022, 09:44 Area-51 <goldsteinindustrial(at)gmail.com (goldsteinindustrial(at)gmail.com)> wrote:



 	  Quote: 	
		  --> Europa-List message posted by: "Area-51" <goldsteinindustrial(at)gmail.com (goldsteinindustrial(at)gmail.com)>

 

 This is fascinating... outside the box; why even use springs? Why not just try lockwire instead? 🤷🏼‍♂️ And is it the expansion contraction of the loop itself that is possibly causing the fatigue crack?? If the loops have no set distance apart then spring tensions will be all over the place; so are the higher or lower tensioned spring loops cracking? Additionally there is no support fixing on many of these rotax 912 muffler boxes; all the modal energy generated is transfered directly through the header pipes; this is just nuts 🤷🏼‍♂️

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=507767#507767

 

 

 

 

 

 

 ===========

 pa-List" rel="noreferrer noreferrer" target="_blank">http://www.matronics.com/Navigator?Europa-List

 ===========

  FORUMS -

 eferrer noreferrer" target="_blank">http://forums.matronics.com

 ===========

 WIKI -

 errer noreferrer" target="_blank">http://wiki.matronics.com

 ===========

 b Site -

           -Matt Dralle, List Admin.

 ="noreferrer noreferrer" target="_blank">https://matronics.com/contribution

 ===========

JonathanMilbank

Joined: 14 Apr 2012
Posts: 384
Location: Aberdeen area

Posted: Wed Aug 31, 2022 1:53 am Post subject: Re: CKT exhaust cracks

Attached is a photo of strengthening done after the tube was TIG welded. A strip of 2mm thick 16mm wide mild steel is secured with jubilee clamps.

CKT #3 exhaust tube repair.doc

Description:

Download

Filename:

CKT #3 exhaust tube repair.doc

Filesize:

252.5 KB

Downloaded:

97 Time(s)

CKT #3 exhaust tube repair.doc

Description:

Download

Filename:

CKT #3 exhaust tube repair.doc

Filesize:

252.5 KB

Downloaded:

82 Time(s)

Display posts from previous:

	Matronics Email Lists Forum Index -> Europa-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum