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Exhaust for ULS

  • Eugene
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2 months 2 weeks ago #21022 by Eugene
Exhaust for ULS was created by Eugene
Working on relocating muffler from top to behind the engine.

Found some cracks, hope you can see them on pictures below.

Trying to do better job at new location.

Looking for good installation practices - how many spring joins we need to have minimum 4 or 8?

Muffler needs to have Lord mounts or not.

Can I install flex joins right next to engine heads 2-3 inches away from outlets?

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2 months 2 weeks ago #21025 by Bill Hertzel
Replied by Bill Hertzel on topic Exhaust for ULS
The final photo looks like someone already welded over a previous crack.
The more flex you can build into the installation the better.
It looks like the current mounting had no give at all.

Keep in mind that if you ever want to install Exhaust Gas Temp Sensors you will need a few inches of solid pipe right near the head.
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2 months 2 weeks ago #21026 by garrett
Replied by garrett on topic Exhaust for ULS
Here is a picture of Evectors exhaust pipe upgrade that allows flex.
midwestsportplanes.com/wp-content/upload...t-Tubes-With-EGT.jpg
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2 months 2 weeks ago #21031 by Eugene
Replied by Eugene on topic Exhaust for ULS
Thank you!

I didn't know that flex piping is available.

Learned something important today. I was told that muffler needs to be installed on engine as rigid as possible. No rubber mounts or springs! We want engine and muffler to vibrate as one unit together.

I was told Rotax 914 is done this way. Hope this is correct.

`

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2 months 2 weeks ago #21034 by garrett
Replied by garrett on topic Exhaust for ULS
The 914 is a low compression engine, a UL with a a turbo charger. Like Roger said part of the vibration problem is due to the ULS's high compression. Some have installed a spacer between the block and cylinders to drop compression a bit to help with the vibration. I had tried a stronger springs and ended up with a cracked up exhaust up system like yours. While helping a friend with a Evector airplane I noticed the flex on the down pipes, his whole system had fallen off in flight and they offered the upgrade pipe flex kit to deal with the vibration as shown in my last post.
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2 months 2 weeks ago #21035 by Bill Hertzel
Replied by Bill Hertzel on topic Exhaust for ULS
I am surprised that you have fractures directly next to a flex joint.
That joint requires that it have Anti-Seize compound reapplied occasionally/as needed.
The Copper Based Lubes are for higher temperatures than the Aluminum Based products.

See LMM Section 05-20-00, Page 5.
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2 months 2 weeks ago - 2 months 2 weeks ago #21055 by Eugene
Replied by Eugene on topic Exhaust for ULS
So far for every question about my airplane I usually get 3 different answers. And I need with my Russian brain to decide which one is best. So question about exhaust system was not any different.

I talked to Lockwood this morning and looks like they don't support their mufflers at all. Muffler is hanging down on 4 pipes only. They think it's the best way and they have very good results with it.

So, I have three different options: support muffler with rubber lord mounts, make it rigid, or don't support at all!

Maybe I should go ask my wife which option to choose. Maybe she knows....
Ok, she thinks that install muffler on top of the engine was mistake on Interplane part. Very big vertical distance from engine mounts make big movements side-to-side on engine start/stop.

Mistake #2 was to mount oil cooler on to this muffler. So, this relatively heavy combination is sitting on rubber mounts on very top and trying to brake loose!

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2 months 2 weeks ago #21067 by garrett
Replied by garrett on topic Exhaust for ULS
You are on the right track, Eugene, with your attention on the vibration and perfecting the exhaust system. A friend of mine has a similar aircraft and has struggled with parts and pieces coming off the motor due to vibration which caused a lot of expensive propellor damage and down time. I also had a tail pipe come off my Remos GX which uses CKT's exhaust. The tail pipe fell off at a weld and burned the fire wall and side of fuselage that led to a year of down time. Due to Remos having financial problems I had to try and find exhaust muffler springs and went with a slightly stronger springs (which were continually breaking) immediately led to muffler cracks and probably led to the tail pipe falling off. After getting the exact replacement springs from Remos including a new muffler the exhaust problems are gone for now. I was was amazed at how even springs and tension is so critical to the performance of the exhaust.
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2 months 2 weeks ago #21099 by Eugene
Replied by Eugene on topic Exhaust for ULS
In order to fabricate engine cowling I need to relocate muffler and oil cooler. I listen to different people and made the conclusion that muffler position behind the engine, just like on this picture, is the best compromise.

I was told this:

#1 - muffler on top of the engine with oil cooler present a lot of drag. It is sitting in clean the air stream and disturbing airflow into propeller.

#2 - muffler with oil cooler on top is relatively heavy combination and sitting on 4 long pipes above the engine = creates a lot of stress on joints and overtime lead to some cracks.

#3 - I talked to propeller manufacturer and they don't see any issues with hot exhaust to be even 2 inches away from propeller. I was told that over time I will see maybe some discoloration on propeller blades, but it will not effect Life expectancy at all.

#4 - muffler behind the engine Will be sitting inside of aerodynamic shade. It will not create additional drag and it will not reduce propeller efficiency, because air behind engine Is very much disturbed already, very much like airflow behind fuselage of this airplane.

#5 - with a lot of effort muffler can be possibly installed in front of engine and right behind the oil tank. Muffler will need to be insulated in that case and that will cut dramatically life expectancy of this unit. If you choose not to insulate muffler, then diverter needs to be made to redirect hot airflow away from engine. On pushers where engine is seating much higher - there is possibility to divert air right down below. But on this airplane I have a baggage compartment below.

#6 - I agree that BRS box is big and bulky. But it is already installed directly on to airframe and cannot get any lower. Maybe I can convert this unit in to soft pack and this way it will get much more compact. I have to do my homework about that.

#7 - oil cooler will be installed right behind water cooler and I was told that this is best location for it.

So, this is what I know so far

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2 months 2 weeks ago #21105 by Eugene
Replied by Eugene on topic Exhaust for ULS

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2 months 2 weeks ago #21106 by garrett
Replied by garrett on topic Exhaust for ULS
Eugene, have you thought about just using straight pipes into a collector? Watch this.
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1 month 3 weeks ago #21288 by Eugene
Replied by Eugene on topic Exhaust for ULS
Wondering if we know general recommendation for my situation:

- is it OK for hot muffler to be only one inch away from oil filter?

- what distance should be hot uninsulated exhaust pipes be away from water hoses, oil hoses and wing fabric?

note: engine will have cowling when I am all done

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1 month 3 weeks ago - 1 month 3 weeks ago #21290 by Roger Lee
Replied by Roger Lee on topic Exhaust for ULS
You just need enough room to unscrew and take the oil filter off otherwise you'll always have to remove the exhaust pipe to remove the oil filter. Hoses that are close should all have some heat shielding. There are a few easy ways to do this. All fuel and oil should be in fire sleeve. If you have things that are close or want to reduce some heat radiation on hoses and wires you can wrap the exhaust in header wrap cloth. The header wrap cloth folks say up to a 70% heat reduction, but some MFG's tend to stretch numbers at times and then there are different installations, but even if it's 50% that's a lot of heat not being radiated on hoses and wire insulation and a big reduction in convected heat.

Just food for thought. There are a ton of folks in my area and around the US that have wrapped exhaust pipes. I've always had my pipes wrapped.

p.s.
If you do use header wrap cloth DO NOT over wrap any EGT probes. The cloth will cause fluctuations on your readings.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
Last edit: 1 month 3 weeks ago by Roger Lee.
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1 month 3 weeks ago #21293 by garrett
Replied by garrett on topic Exhaust for ULS
Eugene, My Remos uses silicon high temp coolant hose for the lower half of the motor. In the Remos installation there is less than 1/4" clearance between exhaust down pipes and the hose and has performed perfectly for the last 9 years. It bends without kinking, does not break down like rubber and withstood the heat when my exhaust pipe broke while every other piece of plastic burned/melted. If you're interested Mac at SkyBound Aviation 579-450-5196 stocks this hose.
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1 month 3 weeks ago #21300 by Eugene
Replied by Eugene on topic Exhaust for ULS
I was told that wrapping exhaust pipes will cut life expectancy by 50%. Not sure if this is correct statement or not.

Were do I find needed wrapping material?

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1 month 3 weeks ago #21302 by Roger Lee
Replied by Roger Lee on topic Exhaust for ULS
Not True. Many have wraps and have never had any issue. If you over wrap it then you may cause an issue, but you should read the instructions which many men have a hard time doing (according to our wive's) before you wrap the pipe. My last plane had about 1500 hrs. before I sold it with wrap. People that make this comment usually don't know the metallurgy of the stainless steel.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
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1 month 3 weeks ago - 1 month 3 weeks ago #21306 by garrett
Replied by garrett on topic Exhaust for ULS
Eugene's exhaust pipes have a history of cracking. If they are covered you can't inspect and in his case if a piece of the exhaust system goes thru the prop it could result in a forced landing or would the wrap hold everything together long enough to find a problem?
Last edit: 1 month 3 weeks ago by garrett. Reason: rewording
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1 month 3 weeks ago #21308 by Gyrochook.
Replied by Gyrochook. on topic Exhaust for ULS
WE have just had an in flight failure of a Turbo (with the associated loss of power) in a gyrocopter where the wrapped exhaust pipes fractured due to heat and vibration. The dislodged part of the pipe then found its way straight into the turbo which only had 40 hours on it.
The less covering the easier for inspection.

Regards..........Chook.
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1 month 3 weeks ago - 1 month 3 weeks ago #21309 by Roger Lee
Replied by Roger Lee on topic Exhaust for ULS
Vibration, stress and poor welds cause pipe breaks. I have never seen a confirmed case of just the wrap causing a break. If you can show me this where vibration, stress and a poor weld did not cause it please do. There are thousands of Rotax wrapped pipes with no issues and some are well over 1000-2000 hours. The stainless steel with its chrome and nickel content is not like regular steel where it has too much carbon. There are 18 types of stainless and ours is designed for high heat. We used a lot of stainless steel when I worked at Arco Chemicals back in the mid 1970's because of its ability to handle heat and cold. Some temps up to 3000F degrees and some as low as -180F.
There is no inspection issue with wrap.
As far as an inspection or a pipe break they don't get a tiny hole or a tiny crack. They snap all the way across and you can hear it. It's a split or shear across the pipe. If you have a break it will shred the wrap at that spot and the wrap will help keep that extremely hot exhaust from ruining nearby items with the hot blast. The wrap is very fragile after it has been heated in place. You won't have any doubt because of the noise, offset in the pipe and trashed wrap. The pipe should never come off if it breaks which does happen and far more times than with wrap.A pipe should never be in danger of leaving the plane. It is attached at the cylinder head and secured below by the springs and you should have safety wire applied in the correct manner.

You can cause an over heat situation by improperly installing the wrap cloth. 2" wrap should only be over wrapped on the edges by 3/8". If you over wrap the cloth by 1/2 the width (1") then you are the one responsible for causing an over heat issue.

Here are a couple of pictures of two broken pipes and one repaired one plus a couple of wrapped pipes.
These never had wrap and in my 20 years have never had a pilot come in with a broken pipe that had wrap although I'm sure there are some out there.

Most people cause their own problems because of not reading before doing maint. or researching before hand.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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Last edit: 1 month 3 weeks ago by Roger Lee.
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1 month 3 weeks ago #21311 by Eugene
Replied by Eugene on topic Exhaust for ULS
Thank you!

So, I should get 2" tape from Aircraft Spruce? Is one brand better than another?

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