Author Topic: Excavating the Pit of Doom  (Read 404 times)

Hugh Conway

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Excavating the Pit of Doom
« on: September 27, 2023, 05:55:32 PM »
A short while back, another member mentioned cleaning out carbon from their exhaust system. I had not done this for 11 years, so decided to give it a go.

Our exhaust system is a baffled underground chamber constructed of concrete blocks in a way that allows the engine exhaust to follow a convoluted maze before exiting via a 4" PVC stack. It does a pretty good job of silencing the exhaust note. The 6/1 is located in an open shed, so there is still the mechanical noise to be heard.

On removing the 2" steel pipe from the cylinder head , I noted no carbon build-up at that end. The total pipe length before entering the Pit is about 8 feet. Inspection of the pit entry end also showed no carbon build-up. I  snaked a brush through the pipe and came up with very little soot build up.

On to the Pit of Doom then......shovelled off the foot or so of soil on top and opened the concrete lids of the chamber. It was another story in there. Some of the passageways (roughly 8" wide by 16" high) were nearly clogged with carbon powder. I dug it all out and put it into some empty hog feed bags (they're quite sturdy) In the end I scooped out around 50 pounds of carbon powder! Amazing at how much got trapped in there! There must be a good use for that stuff, but I could not think of any that would be wife approved, so it went to the local dump.

The actual block structure was completely intact, so after the cleaning, it was easily all buttoned up and recovered with soil. Ready for another 3000+ hours. A messy but necessary job, it was easily completed in a couple of hours.........about the same amount of time that it took to clean up the tools and myself!

I am now wondering what happens to all the soot that might go into a standard type of muffler. Does it burn out due to heat? Does it just get blown out into the air? Does it also collect in the muffler, and how do es one remove it?

At any rate, good to go for another while.

Cheers
Hugh
JKson 6/1  (Utterpower PMG ) Off-grid
Lister 6/1 Start-O-Matic engine......running with PMG
1978 Royal Enfield (glutton for punishment by Indian iron)
1963 BMW R-27 project

Powdermonkey

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Re: Excavating the Pit of Doom
« Reply #1 on: September 28, 2023, 03:42:49 AM »
Hello Hugh- Yep, that was me.  I'm hoping you took pictures of your pit of doom?  I'd like to make one for my twins....

Hugh Conway

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Re: Excavating the Pit of Doom
« Reply #2 on: September 28, 2023, 05:40:15 PM »
Powdermonkey:
Sorry, no photos. I never seem to take photos when in the process of doing. The camera would be oily, dirty, sooty, etc.

Roughly the pit is about 3ft X 6ft with a maze assembled from the usual concrete building blocks stacked two high.  The cover is made of 4 cast in place concrete slabs (not as heavy as one piece) with the in and out at opposite ends  of the covering . The exhaust path enters into the pit  through steel pipe cast into the slab at one end., then  zig-zags from one end to the other of the maze. Exhaust exits via a short length of 2" pipe cast into the cover at the other end. The 4" PVC stack is simple placed over the pipe.

It had slipped my mind entirely that I have actually cleaned this out 7 years ago, and noted that in a post back then!!!
https://listerengine.com/smf/index.php?topic=7773.0

I have searched through all of my bookmarks for the site that originally posted the Pit-of-Doom layout with drawings and photos. It is one of those that no longer exists. I did find a youtube of a 6/1 in action inside a sound insulated shed with a Pit style silencer. This set-up is far better done than mine, which is rather crude.
https://www.youtube.com/watch?v=B2682AwYJ7w&ab_channel=MichaelBarkley

Anyway, not rocket science, just sketch one out using standard block measurements and get a shovel......!
Cheers
Hugh
JKson 6/1  (Utterpower PMG ) Off-grid
Lister 6/1 Start-O-Matic engine......running with PMG
1978 Royal Enfield (glutton for punishment by Indian iron)
1963 BMW R-27 project

Hugh Conway

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Re: Excavating the Pit of Doom
« Reply #3 on: September 28, 2023, 05:46:09 PM »
Powdermonkey
Here' more: https://listerengine.com/smf/index.php?topic=8819.0
This link has an actual drawing....more involved than what I used. Apparently there is a Lister specification for underground silencer. some more searching might locate it .
Cheers
Hugh
JKson 6/1  (Utterpower PMG ) Off-grid
Lister 6/1 Start-O-Matic engine......running with PMG
1978 Royal Enfield (glutton for punishment by Indian iron)
1963 BMW R-27 project

veggie

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Re: Excavating the Pit of Doom
« Reply #4 on: September 30, 2023, 03:05:35 PM »
50 pounds of carbon powder ??   :o
Wow, I had better check my dual tank muffler more often than planned.
My guess is that the powder would have gone into the atmosphere otherwise, eventually settling in the soil and becoming part of the natural carbon storage system.
And you estimate that this was after ~3000 hours ?

Just wondering, what type of cooling system do you use?
Is the engine coolant getting up to 190f during use? If running too cool, maybe a lot of soot production.

veggie
« Last Edit: September 30, 2023, 03:59:21 PM by veggie »
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Hugh Conway

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Re: Excavating the Pit of Doom
« Reply #5 on: September 30, 2023, 09:22:42 PM »
@ Veggie
I was in error re 3000 + hours on the pit to gather 50+ pounds of carbon. Looking over past posts, I see that I cleaned it out once before, in 2016. So run time since has probably been 1700 to 2000 hours or so.

Cooling is thermosiphon via a repurposed  cast iron domestic water heat radiator with a small expansion tank. It heats up pretty quickly. No thermostat. I normally run for 2 to 2 1/2 hours at a time for battery charging, so running temp, I would think, is hot and fairly stable.

Some of the fuel has been domestic oil heater stuff, I was given a couple of hundred gallons. Maybe that?

Cheers
Hugh
JKson 6/1  (Utterpower PMG ) Off-grid
Lister 6/1 Start-O-Matic engine......running with PMG
1978 Royal Enfield (glutton for punishment by Indian iron)
1963 BMW R-27 project

BruceM

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Re: Excavating the Pit of Doom
« Reply #6 on: October 12, 2023, 04:12:43 AM »
Hugh's high soot quantity in his pit type muffler points out the need for an exhaust viewing capability with pit or earth (leach field) type mufflers.

On my neighbor's 8/1 conversion to propane,  we put in a T in the 2 inch pipe leading to the leachfield muffler and put the stock Pot type CS muffler on that  (knee height) while we were working out the bugs on the conversion (which is still running well).  The pot muffler is still useful whenever there is some cocern about engine health.  Normally the Tee is plugged and normal flow is straight through with no restriction or turn.

Bruce






Powdermonkey

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Re: Excavating the Pit of Doom
« Reply #7 on: October 12, 2023, 12:56:58 PM »
Hmmmm.....a muffler uses the same principle as a silencer.  Surface area and COOLING are the critical elements to success.  So....what if we simply used existing technology/parts to do the same? 

Have a look at this link.  I think this may work.....

https://www.infiltratorwater.com/products/chambers/

Powdermonkey

BruceM

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Re: Excavating the Pit of Doom
« Reply #8 on: October 12, 2023, 03:07:52 PM »
Plastic concerns me for the area near the hot exhaust inlet.  Also, by price I think Hugh's setup with concrete blocks is likely much cheaper.  I'm just surprised at the amount of carbon black he has collected.  Makes me concerned for the 3 inch  leach field rock approach though it will hold a large amount before being choked off. We  perforated a pipe section about 8 feet long at the inlet.   There is not much coming out of the 4 inch PVC perforated section (standard for leach fields) with riser at the end of the trench- no sound, no pulses of air, and just the smell of earth.

Hugh's pit fuffler has the advantage of being readily serviceable.  We may have to dig up the trench near the inlet perforated pipe at some point for my neighbor's setup, but since its propane, it may be a long time before that is needed.