Author Topic: Vibration analysis  (Read 1074 times)

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Offline RedneckInTraining

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Vibration analysis
« on: May 3, 2020, 08:59:38 pm »
So I have a 96 dodge ram 1500 2wd swb truck that I use for gambler 500 events.It is driven pretty hard on rough roads.For the most part everything holds together EXCEPT for my exhaust.After each gambler 500 event which contains 4-500 miles of back road driving in 2 days my exhaust is usually broken.The first event the factory exhaust broke in 3 separate places.I repaired it then ran another event and it broke again.So I decided to radially change the exhaust and shorten it up as much as possible to take some of the strain off it.So my exhaust comes out of the factory y pipe which ends at the transmission crossmember with a 2 bolt flange I welded in. The Y pipe is supported at the manifolds and at the factory hanger at the end of the transmission.After the crossmember there is a piece of 4" mesh flex pipe that immediately dumps into a short muffler, after the muffler there is a short length of exhaust tubing, that goes into 2 90* bends to go up and over the frame and punch out the right front corner of the bed before the tire.The exhaust is supported by the factory hanger before it goes up and over the frame.The exhaust lasted longer but it still broke, this time, it cracked out the rear of the muffler.Where should I add another exhaust hanger so the exhaust after the tailpipe won't crack out again?
1994 Dodge Ram 2500 CTD
1987 Dodge Dakota 3.9 V6

                      RON PAUL- 2012
Governments control people. Who CONTROLS the GOVERNMENTS of the people?

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    Offline Chilly

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    Re: Vibration analysis
    « Reply #1 on: May 4, 2020, 05:56:02 pm »
    How about incorporating a flexible section or two, then let the pipes float with the body?  A small amount of engine movement translated down the length of the exhaust system results in a LOT of movement at tail pipe.  Or more accurately it wants to move but can only bend.  Then break.

    I'd put a flex section after each down pipe and see what happens.   I'm not sure adding more hangers will do anything except hold the pipe even more rigidly while the engine is still needing to shift about.
    92 Ramcharger
    360 TBI, auto, 241 t-case
    44F, 9.25R posi, 3.54 gears (yeah, I know)
    Skyjacker 4", 33x12.5

    Offline RedneckInTraining

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    Re: Vibration analysis
    « Reply #2 on: May 4, 2020, 07:22:31 pm »
    There is a 4" long section stainless steel mesh at the front of the tailpipe section to isolate the engine vibrations from the rest of the system.
    1994 Dodge Ram 2500 CTD
    1987 Dodge Dakota 3.9 V6

                          RON PAUL- 2012
    Governments control people. Who CONTROLS the GOVERNMENTS of the people?

    Offline Chilly

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    Re: Vibration analysis
    « Reply #3 on: May 4, 2020, 07:26:10 pm »
    I was suggesting its not vibration so much as bending.  When the engine/tranny moves about on the mounts something has to give. 
    92 Ramcharger
    360 TBI, auto, 241 t-case
    44F, 9.25R posi, 3.54 gears (yeah, I know)
    Skyjacker 4", 33x12.5

    Offline RedneckInTraining

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    Re: Vibration analysis
    « Reply #4 on: May 5, 2020, 07:31:34 am »
    I welded up the crack as best as I could which isnt saying much because I couldnt clean some areas.Welding those same areas was a crapshoot because I basically had to weld blind and hope it worked.So I'm gonna reinforce it alittle.Then I'll reinstall the exhaust and see where it has alot of relative movement that would cause it to fatigue.
    1994 Dodge Ram 2500 CTD
    1987 Dodge Dakota 3.9 V6

                          RON PAUL- 2012
    Governments control people. Who CONTROLS the GOVERNMENTS of the people?

    Offline RXT

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    Re: Vibration analysis
    « Reply #5 on: May 5, 2020, 07:51:25 pm »
    Whats the tab looking thing just before the bend??

    Heres what I would do. First, trash that muffler. I would use a straight thru muffler, a glasspck, like a Thrush, or Cherry Bomb whatever, so long as it's a straight thru.

    Next, don't use solid hangers. Go with rubber or flexible hangers

    You could probably do without the flex pipe. While it's supposed to be designed to flex, it isn't designed for constant motion. Those things will wear out and start leaking.

    Check your motor mounts and trans mount. If they are worn out or damaged, your engine could be moving excessively and breaking the exhaust. While you are at it, check the frame for damage like; cracks, bent rails, missing rivets, or anything that could be causing the frame to flex more than normal, and that could be fatiguing the exhaust (with solid hangers)

    Ed
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    Offline RedneckInTraining

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    Re: Vibration analysis
    « Reply #6 on: May 6, 2020, 08:13:30 pm »
    Thats a negative on the straight through muffler.Its loud enough as it is.

    The exhaust isnt solid mounted.The tab before the bend is where it mounts to the factory rubber hanger.

    Motor mounts are good,transmission mount has about 1000 miles on it.The engine and transmission do not thrash around.

    The entire truck flexes more than normal because most of the time I drive it I'm hauling a55 on rough roads,I bounce it over rocks and dips the size of watermelons.

    here is an old picture of the truck before I shortened the exhaust and made a new rear bumper.
    1994 Dodge Ram 2500 CTD
    1987 Dodge Dakota 3.9 V6

                          RON PAUL- 2012
    Governments control people. Who CONTROLS the GOVERNMENTS of the people?

    Offline RXT

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    Re: Vibration analysis
    « Reply #7 on: May 7, 2020, 05:21:39 am »
    Thats a negative on the straight through muffler.Its loud enough as it is.

    Going by the pic you posted, that muffler looks like it has fatigue cracking. A straight thru won't crack like that, especially a Cherry Bomb, because those things are made with a thicker body. Are they loud? Only when you're on the throttle….and you could reduce the noise, with an old Super Trap or add in a resonator.

    Quote
    The exhaust isn't solid mounted.The tab before the bend is where it mounts to the factory rubber hanger.

    Make sure the hangers have enough length to absorb movement.

    Ed


    If we lose freedom here, there is no place to escape to. This is the last stand on Earth.

    Ronald Reagan


    "America will never be a socialist country"

    Donald Trump

    Offline Chilly

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    Re: Vibration analysis
    « Reply #8 on: May 7, 2020, 05:40:01 am »
    Flowmasters are made of pretty stout steel.
    92 Ramcharger
    360 TBI, auto, 241 t-case
    44F, 9.25R posi, 3.54 gears (yeah, I know)
    Skyjacker 4", 33x12.5

    Offline RedneckInTraining

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    Re: Vibration analysis
    « Reply #9 on: May 8, 2020, 02:37:17 am »
    I only have a little V6.About the only time it sounds good is when its revved up over 3.5k.Below that its just bassy without alot of rumble.Although a resonator might help.
    1994 Dodge Ram 2500 CTD
    1987 Dodge Dakota 3.9 V6

                          RON PAUL- 2012
    Governments control people. Who CONTROLS the GOVERNMENTS of the people?

    Offline RXT

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    Re: Vibration analysis
    « Reply #10 on: May 10, 2020, 10:34:02 am »
    So???? You're not gonna install a straight thru muffler, because your 1500 has a V6 and it won't sound good until it's at 3.5K rpm???

    Ed
    If we lose freedom here, there is no place to escape to. This is the last stand on Earth.

    Ronald Reagan


    "America will never be a socialist country"

    Donald Trump

    Offline RedneckInTraining

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    Re: Vibration analysis
    « Reply #11 on: May 10, 2020, 03:57:45 pm »
    I'm not gonna install a straight through muffler because the truck is loud enough as it is.I dont need to advertise that I am doing dumb stuff with it for everyone for miles around.Yes, its eye catching but I would rather have LOS  be the only tool at a cops disposal I dont want them hearing me coming.
    1994 Dodge Ram 2500 CTD
    1987 Dodge Dakota 3.9 V6

                          RON PAUL- 2012
    Governments control people. Who CONTROLS the GOVERNMENTS of the people?

    Offline RedneckInTraining

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    Re: Vibration analysis
    « Reply #12 on: May 15, 2020, 04:22:08 am »
    Took it by a muffler shop and the guy there thought it was well supported, In his opinion it failed simply because of the thin stamped steel construction of the muffler itself.He said he as seen many failures exactly the same way...maybe I need a full welded muffler, but I'm not a fan of the traditional chambered muffler sound especially with a v6.The last thing it needs is more bassy.
    1994 Dodge Ram 2500 CTD
    1987 Dodge Dakota 3.9 V6

                          RON PAUL- 2012
    Governments control people. Who CONTROLS the GOVERNMENTS of the people?

    Offline RXT

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    Re: Vibration analysis
    « Reply #13 on: May 15, 2020, 05:02:53 am »
    You'll never make a V6 sound good unless you muffle it so much you don't really hear the engine. Priority here is make it work and last, then worry about how well it sounds. As mentioned you could always add in a resonator, to help kill any bark.

    Ed
    If we lose freedom here, there is no place to escape to. This is the last stand on Earth.

    Ronald Reagan


    "America will never be a socialist country"

    Donald Trump

    Offline RedneckInTraining

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    Re: Vibration analysis
    « Reply #14 on: May 16, 2020, 10:47:13 am »
    I might go with a straight thru style magnaflow,but I need to see one in person to see if its thick enough.Flowcrappers are bassy and the last thing it needs is more base.
    1994 Dodge Ram 2500 CTD
    1987 Dodge Dakota 3.9 V6

                          RON PAUL- 2012
    Governments control people. Who CONTROLS the GOVERNMENTS of the people?

     

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