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Sympathetic Vibrations


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My Pilothouse has been on the road now for about six weeks. I've put almost 500 miles on it alredy, and man, does she rattle! Thought I had done a good job of nailing things down - new window channels and belt fuzzies, door weatherstripping and all like that. Even put sound deadener and insulation inside the doors and cab everywhere it was possible. But on a pull, when you lug it down, everything inside the cab rattles - the door handles, the cowl vent, even the wiper linkages rattle.

I'm guessing that sixty-plus years of pulling its heart out carrying big and small loads have taken their toll. After all, our truck motor mounts at the back half of the engine do leave something to be desired. That big bell housing that bolts solid inside the frame rails has nairy a rubber insulator anywhere in sight. Sorta' makes you want to redesign things here and there.

Anybody far enough along with their project to have any solutions for any of these annoying rattles? There sure seem to be enough to go around . . . . . . :eek:

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Dave,

The bell housing on my B3B has rubber isolators between it and the frame mounts. The parts catalog lists them as a "Engine Rear Support Insulator" part # 1312-511. There are similar parts listed for the earlier trucks as well.

Can you post a picture or two of your rear engine mounting arrangement?

Brad

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GB-mine sings at about 38mph and then stops as you accellerate. There should be rubber bushings in the motor and cab mounts. Maybe they're collapsed. For the door handles do you have the springs behing the escutheons to hold pressure on them? How are your u joints? I haven't done a lot of sound deadening on mine because all that is gonna do is enable me to hear something I haven't heard before so that I can wonder what that noise is. Think of it that she's just whispering to you-when she's got something serious to say she'll raise her voice and shout it out. Mike

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After all, our truck motor mounts at the back half of the engine do leave something to be desired. That big bell housing that bolts solid inside the frame rails has nairy a rubber insulator anywhere in sight ....

Should be some big fat rubber disc shaped insulators present. Not soild. If you dont have any ( or are really flat ) I just removed a pair off a 48. I'll take a picture for you if it helps.

48D

http://dodgepilothouseclub.org/know/ph_parts/b_9.pdf

page 9-3

part # 9-71-5

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You might also turn your drive shaft 180 degrees on one of the flanges. Alot of harmonic stuff is from the drive shaft not liking the positioin its in, many times flipping it 1/2 turn will cause a lot of these shakes to go away.

But those missing isolators may be the big ticket.

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On my 39 deSoto i had a new clutch a pp put in the car along with rea motot mounts. Then drove the car and then noticed some vibration when driving the car. The mechanic told me that the harmonic damper needed to be replaced. This stopped the vibrations.

This could be your problem. Just a thought.

rich

desoto1939@aol.com

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Dave,

I'm impressed that you can differentiate between a cowl vent rattle and a wiper linkage rattle. You must have good ears for an old timer. :D

Just do what I do and turn the radio up. :D:D Or just sing louder if without a radio. ;)

Rich,

Our trucks don't have a harmonic balancer.

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Gentlemen, let me introduce to you my secret weapon - grandson Lukie, all nine years of him. Built like a snake and tall for his age, he can get his hands on any part of the underdash you can mention - this whilst rumbling down the road. This is how I can discern between cowl vent linkage, wiper linkage and other such noisemakers.

This is all really most noticeable on a hard long pull, where it sorta' shakes its head and says, "You want me to do what?" Mebby it just needs to relearn who'se boss in this relationship. Guess I shoulda' left that first load of compost on a few weeks, and parked it out in the rain. Mighta' softened it up a little, huh?:)

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Merle:

i looked at the attached parts list and refer to the part number 9-13-5. This is listed as the dampner or cracnkshaft vibration dampner or as other people call it a harmonic balancer. This has a rubber mouting which helps balance the engine and also has the flat spot for timing with the timing marks.

This do go and there is a guy inthe WPC Dampner Doc that can repair these.

Look at the printout that was on the first posting. All engines have the vibration dampner.

rich hartung

desoto1939@aol.com

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Hey Ed,

There is no rubber in the front, but in the 48-53's there are 4 rubber discs in the back between the 2 motormounts.

48D

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Harmonic damper

From Wikipedia, the free encyclopedia

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A harmonic damper is a device fitted the free (accessory drive) end of the crankshaft of an internal combustion engine. It is essential in engines with long crankshafts (such as straight-8 engines) and is present on most engines as it reduces torsional vibrations that tend to peak at certain speeds.

Contents [hide]

1 Need

2 Construction

3 Identification

4 Maintenance

[edit] Need

Without the presence of a damper a long crankshaft will tend to act as a torsional spring to some extent. Impulses applied to the crankshaft by the connecting rods will tend to "wind" this spring, which will respond (as a spring-mass system) by unwinding and re-winding in the opposite direction. This will usually be damped out naturally, but at certain crankshaft rotational speeds the impulses from the cylinder firing can be in synchronization with the natural resonant frequency. (Some aircraft engines are restricted from continuous operations at specific RPM to avoid the danger of metal fatigue causing a break in the crankshaft.) In an automotive engine there is little control over operation in such specific speed bands and furthermore there may be uncomfortable vibrations as the engine is operated through such speeds, even if not a problem for engine durability.

In rare cases, a portion of the crankshaft system's overall balancing may be provided by an unbalanced damper.

[edit] Construction

The damper consists of an inner hub affixed usually by a key and keyway to the outer end of the crankshaft. An outer circular mass is attached to the hub by an integral rubber or other elastomeric section. This crankshaft and damper together become (in its torsional response) a spring-mass-damper system. By selection of the damping section material and the size of the outer mass the damper may be made to resist and thus quiet the specific torsional vibrations. These vibrations will not be at the same frequency as originally since additional mass has been added to the resonant system, so the damper must be tuned for the resultant circumstances. The overall appearance is that of a thick disk.

[edit] Identification

The damper will be fitted at the front of the engine (opposite the clutch or transmission, just beyond the cover of the timing chain, gears, or belt, and behind the accessory drive pulley (which may carry one or more V-belts or a single serpentine cog-belt. In older vehicles there will usually be an inscribed timing mark, there for purposes of setting the ignition timing.

[edit] Maintenance

There is no need for maintenance of such a simple system since modern synthetic rubbers will be resistant to any oil leaking from the engine's front seal.

Retrieved from "http://en.wikipedia.org/wiki/Harmonic_damper"

In the picture of the truck engine the harmonic balancer or damperner as refer to part 9-13-5 is where the timing mark is onthe engine and this does have a rubber inner that is used to absorb crankshaft vibrations. And if the vibrations are not absorbed then this can be felt when driving. read the verbage from the Wiki that is above.

rich Hartung

Edited by desoto1939
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In the picture of the truck engine the harmonic balancer or damperner as refer to part 9-13-5 is where the timing mark is onthe engine and this does have a rubber inner that is used to absorb crankshaft vibrations. And if the vibrations are not absorbed then this can be felt when driving. read the verbage from the Wiki that is above.

rich Hartung

Rich;

Fact is not all Mopar flathead engines are equipped with a vibration damper. The picture of the truck engine that Young Ed posted is an example of an engine with no vibration damper. I have personally seen several Dodge D-24's with no damper and those with no damper have a "catch" on the front of the engine for a hand crank even though there is not a hole through the radiator to use a hand crank. I suspect the factory had a huge pre war surplus of pulleys with no damper and installed them on new vehicles after the war until the supply dwindled.

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That engine is in a 46 truck and should have a hand crank nut on the front hub. But the engine and I'm 99% sure the pulley are stock 52 plymouth car. So apparently they went back to it. I know my truck has the narrow newer style fan belt.

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This thread has sorta' meandered away from vibrations on a hard pull, but that's fine with me, and is okay, too. It has been interesting, to say the least.

My B1B has no vibration damper on the crank front snout, but as Don mentions, it does have the large bolt with the slotted head with a crank ratchet feature built into it. Front motor mount is conventional rubber biscuit atop the timing cover.

However, my rear mount is simply the bellhousing bolted directly to the frame with no rubber insulation whatsoever, just like all the larger trucks are, to my best understanding. Do any of you have Pilothouse pickups with rubber at the rear mounts? Could this be retrofitted to earlier types like mine? Mebby with another bellhousing.

I see in the parts book that B2B's carry a rubber insulator and some later half tons do so as well. Guess my luck was to buy an early one with no rubber insulation between the block and the frame - sorta coal-shed engineering IMHO for MoPar, who was so advanced in many other important areas. Maybe that's why everything rattles on a pull?

Guess they just figgered trucks were meant to earn their pay - not keep the operator lulled to sleep, 'er whatever. Go figure . . .:o

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I dont think we got off topic. You mentioned serveral possible vibration noises with the hard pull being the most noticable. The picture of the motormount is the rear mount off a 48 1/2 ton. You don't have one? Isn't your truck a 48' ? Maybe the previous owner swapped out the originals for something he had in the "parts box" . Here's another look at the mount attached to the motor/trans braket.

020-1.jpg

022-1.jpg

48D

Edited by 48dodger
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It's hard to imagine that earlier era trucks have the same engine mounts that our Pilot House trucks have, yet they mounted Daves engine solid. If it truely is mounted solid to the frame then it's more likely that a previous owner did it. I can tell you that they aren't much fun to replace. I did mine before I put the engine back into the frame, and it still wasn't much fun. You'll have to pull the whole mount assembly out to get the center bolt out. Then you can seperate the assembly and replace the rubber pieces. As I recall, I got new ones from Roberts.

Here's another picture showing the rear mount. (it's hidden behind the clutch pedal)

P1200199.jpg

And another pic of a truck engine without a damper. It's only a pully on the front of the crank.

P9240506.jpg

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