Exhaust tail pipe question

[jamesm]

Hi,

I have a torque / clamping force question. So I had to replace tail pipe Exhaust hanger spring.

My last IA who installed  who installed the Tail pipe hanger spring  ( the one below in picture)  lasted  20 years  plus, I hoping to get another 20 years out of the spring that I have just replaced. 

Prior to the last IA install I have had to replace them more frequently  than 20 years if memory serves me correctly.

My question is should there be  some movement in the clamp that goes over tail pipe portion ?

 

Thanks,

James '67C

[Hank]

The one on my C was hand cut from the sidewall of an old tire. Never seen one of them fancy springs before . . . .

[carusoam]

As for adding additional movement... 

The spring does a lot of the movement...

The original tire bits did a fair amount of movement...

What type of movement are you looking to allow for?

Is the engine sliding forwards and backwards? That would be bad... and require lots of dynamic change in your flight’s WnB details...

Is the exhaust pipe expanding with temp so much, extra distance needs to be accounted for?
 

There may be a proper set-up that works better... see if there is an installation procedure to go with that spring...

There is a thread around here about cutting a proper AW piece of rubber out of a tire sidewall including proper graphics  like a winged foot from a Goodyear tire... 

PP thoughts only, not a mechanic...

Best regards,

-a-

[MikeOH]

Plus one to finding a depiction of "proper setup."

At first glance the spring in the foreground looks like it might be rotated 180 degrees. It looks like there is very little clearance between the vertical portion of the spring and the pipe. Rotating the spring would put that part of the spring clear of rubbing on the pipe.

[jamesm]

23 minutes ago, carusoam said:

What type of movement are you looking to allow for?

I wasn't too sure,  I thought that there might be  a little a bit fore and aft movement but I guess once the Engine heats up the exhaust that probably take up any expansion that I could  give it by leaving  the nuts a little less snug.  My last IA put rubber grommets in spring portion that mounts to the swivel on the firewall and that lasted 15 years or so.  Before that I seems to me I had replace the  tail pipe exhaust springs  at least twice that I remember. 

Stating the obvious  there is definite movement in the exhaust system other wise there wouldn't be any slip joints and ball joints.

The picture depicted in the broken state for illustration purposes to contrast good spring is outboard and bad  "broken" spring is the inboard.  I had move the spring a bit to show up in the picture.   The weird thing of it was is that I had just change my oil  and I was doing my post flight check and I was doing Touch and Goes  one last circuits in the  pattern. I was downwind and it was like someone had shove the prop control forward all at once. The whole  down  bodged  down for a brief second  almost like uncommanded  deployment of speed brakes which I don't have.  I suspect that may have been when the spring may have broke. The last circuit around the pattern seemed normal as I recall.

I have replace spring but someone/something has set pretty much the  whole west coast a blaze  and have been waiting for all this stupid smoke to clear.

I was seeking advise from the wisdom of MooneySpacers .

James '67C

[carusoam]

Let’s see if the smoke hasn’t gotten to the east side of Canada yet... 

@M20Doc (insight On exhaust pipe supports... broken spring mount/pipe hanger)

Best regards,

-a-

[EricJ]

If the band can move it'll take a little stress off the springs, which might make them last a bit longer.   Since they're springs, though, they can flex pretty well anyway.

Even if the band were loose, it might only be loose when cold and tighten up when the pipe gets hot, so it may not make much difference.

Exhaust stuff is supposed to be a little loose, so that it can move around a bit and expand into things when it gets hot.

[Greg Ellis]

On 9/12/2020 at 7:37 PM, Hank said:

The one on my C was hand cut from the sidewall of an old tire. Never seen one of them fancy springs before . . . .

The one on my 63 C model is also a hand cut piece of rubber as well.

[47U]

I’ve replaced one spring in the 12 years I’ve owned my ‘63C, about 6 or 7 years ago.  No idea how long it had been in service.  When I called Dan to order the spring, I asked him if I should convert to the rubber hanger per SBM 20-144, he said, “No.”

I found any guidance on the spring hangar in SBM 20-86 (22 Dec 1961) which provides for installation of the Hanlon & Wilson exhaust on the M20B.  The clamp on the tailpipe is snug and there are no standoffs between the clamp and the spring (pn 6226).  I think standoffs would only push the tailpipe down further into the slip stream exerting more force on the springs and creating drag.  The AN3 bolt that goes through the eyebolt holding the top loops of the springs is not tight, so the springs can move around a bit.  And (I had forgotten this) the tailpipe outlet should be rotated 10 +- 2 degrees outboard to direct exhaust away from the nose gear door and perhaps not send as much CO directly under the fuselage where it might work its way into the cabin.  When putting all this together, I try to get the springs and tailpipe clamp lined up loosely and directly underneath the eyebolt so there’s as little preload on the springs as possible.  I use a longer AN3 bolt at the top and put a couple AN960 washers as spacers to minimize the preload on the spring at the eyebolt.

Tom

 

Edited September 15, 2020 by 47U
Clarification.

[jamesm]

Thanks.

I don't recall seeing the picture in the maintenance manuals  or part catalog they must taken it out in later models.

Good detail.

James '67C