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Old 20-08-2016, 03:01   #16
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Re: Terminology help: Damper plate, clutch disc, pressure plate, drive damper

Originally Posted by pbmaise View Post
A very frustrating aspect of what should be a simple exercise is I have the complete "Workshop Manual" for my Isuzu Engine and

Zero mention of a damper plate is made and zero dimensions of the flywheel are shown.

The best thing the manual told me is my engine is 5.785 liters.

The manual shows me a drawing of the flywheel and I see 12 bolt holes. Many images I see of damper plates only show 8 bolt holes.

Obviously the triangular version doesn't use all bolt holes available.

One interestingly tidbit I gained was from the website I was directed towards

" Today's marine diesels are designed with lightweight flywheels which do not create the inertia of an older heavy flywheel. The lighter flywheels result in gear chatter or rattle at low RPM's. This rattle translates into gear wear and damage to the drivetrain. Our damper plates eliminate this problem."

In other words the damper plate according to above us nothing more than weight hung onto the flywheel to help reduce chatter at low revs.

Well golly gee! I already have a damper plate on my engine so the weight is currently present and obviously not doing its job well. Pulling its weight. Ha, ha.

This website shows a round one with 12 holes.

-- PYI Inc. Max-Prop PSS Shaft Seal Seaview Radar Mounts R&D --

It introduced two new terms too.

"A "Hammer Head" damper plate is designed for general use where motoring at low Rpm's is common."

It is common for me to be at low revs to conserve fuel.

" A "High Deflection" damper plate is designed for use in vessels where low RPM engine use is the norm as in work boats or where gear noise is being experienced."

Well that is me too. Groan.

This brings me back to the central problem. I am obviously here because of noise at low revs and a worry the transmission guy told me I should replace the disc soon.

A "high deflection" damper plate sounds like the thing for me. I bet it is expensive.

I filled in their form and was given 403Error reply. The form indeed asked for wide range of information that I don't have despite having manuals for both engine and transmission.

# of holes is a guess of 12 based on drawing
Max revs... hmm low
Flywheel diameter unkown
Pitch of holes...don't even know what that is
Hole diameters... unkown
Shaft diameter...unkown

All these questions and people keep telling I have one of most popular engines and transmissions.

This is frustrating fast. Well actually slow I have been carefully reading manuals cover to cover for information not present.

Probably the best place to find the information you're looking for is in the model and serial number specific parts manual from Isuzu. The parts manual should have a list of all the plates supplied with the engine and their part numbers, along with, if you're lucky, dimensions and applications. The manuals are available on line, though I couldn't find a free one.

Usually the drive plate is supplied by the engine manufacturer, though they are often manufactured by another company. Sometimes the engine manufacturer sells the engine to an equipment supplier with the flywheel machined to their spec; Mercruiser and Twin Disc come to mind. If this is the case, then Four Winds discovery that Borg Warner supplies discs is the proper resource.

There are of course aftermarket specialists who provide a multitude of replacement discs, with a wide variety of real and imagined 'improvements'. A reputable aftermarket supplier will be able to cross reference the manufacturers part number with their part number in order to give the closest match.

This of course doesn't mean that it will solve your problem. If there was a specing issue originally, replacing the old plate with the same new plate will just repeat the issue. There are idiosyncratic issues with every installation, a boat is probably one of the most problematic because of, among other things, their somewhat flexible nature and the lack of a large consumer base on which to ferret out problems.

The 'high deflection' disc on the PYI website looks like it might solve your problem, though on the other hand a lot of flexibility might allow the induction of some kind of vibration. A lot of times it really can seem to be a crap shoot. Often a call to the disc manufacturer or their representative makes things a whole lot easier...the aftermarket suppliers have seen a lot more problems of the sort you seem to be describing.

All the information required, except the rpm and maybe the pitch, should be in the parts manual. They probably want maximum rpm, though operating rpm may be asked for also. The bolt pitch is most likely 360 divided by the number of holes, i.e. 360 divided by 4 = 90 degree bolt pitch, 360 divided by 12 = 30, etc.

The gearbox shaft size and spline will come from the box manufacturer, and is also model and serial number specific, but the plate manufacturer will know what they are if you give them that information.

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Old 20-08-2016, 03:47   #17
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Re: Terminology help: Damper plate, clutch disc, pressure plate, drive damper

Engine Mfgrs could care less how you attach to their flywheel for marine & industrial applications.
Borg Warner are the folks that specify using a damper drive plate.
You may be able to buy a damper drive plate from your engine mfgr/dealer,but I assure you,it was not made by the engine mfgr. He got it from the same outside sources that you can.
Find a damper drive supplier & order one to fit your engine's flywheel & the splined input shaft of your BW model.

The term CD used by your mechanic is incorrect if it stands for Clutch Disk.

Hope this helps/ Len

My personal experience & humble opinions-feel free to ignore both
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Old 20-08-2016, 08:46   #18
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Re: Terminology help: Damper plate, clutch disc, pressure plate, drive damper

Info R&D damper-plates without steel springs:
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Old 20-08-2016, 08:51   #19
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Re: Terminology help: Damper plate, clutch disc, pressure plate, drive damper

Many work boats around here replace the damper plate annually Down time can be more costly. Just google damper plate, I particularly like the rubber socket type.More mass as its two cast Al parts with large teeth holding rubber cups Very easy alignment, no gear chatter at idle , it won't spit springs and if the spline finally rusts tight due to salty bilge ,you can still back off the box.Several makers .Spline size and # is the only info needed as bolt patterns are pretty standard. New bolts properly torqued You don't want to easy out the flywheel or hear the parts rattle around in the bell housing. (Izusu marine engines have bigger flywheel than the standard .What's in your bilge?)
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Old 20-08-2016, 10:04   #20
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Re: Terminology help: Damper plate, clutch disc, pressure plate, drive damper

My Borg Warner Velvet Drive is on a Perkins 4.236. Here's what the dampner plate looks like.

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Old 20-08-2016, 23:07   #21
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Re: Terminology help: Damper plate, clutch disc, pressure plate, drive damper

Thanks for helping all.

Using the RandD PDF I was able to see that it seems all 26 tooth transmissions have the exact same size shaft. (34.4mm)

I located a website that told me an exact HP for my engine at a specific RPM (142 HP at 2,800 rpm). RandD provided a formula to calculate Maximum torque.

The thing that absorbs the shock load is called the "element". Torque is needed to size the right element.

The same website I found reporting my engine HP stated it has torque is 289 ft lbs at 1,600 rpm. This is a higher figure than if I used the formula so I will run with it.

Three styles of elements are made by RandD. The Hammer Head sounded like my best fit.

I do indeed run mainly at low revs. The High Deflection element states it only works in one direction. A worrying thing since I don't know which direction my engine turns. I am not exactly keen on starting my engine with the transmission removed to find out. I bet it is the most expensive option so looks like hammer head it is.

Using the sizing table I found I want element U which is rated at 350 ft lbs.

The backing plate attaches the element to the flywheel. This is where finding the right clutch pressure plate would come in handy. The clutch pressure plate is far more common and bolts to the same locations as the damper backing plate.

All I was able to find was an actual photo of a flywheel from my engine.

I was not able to find diameter and pitch diameter. Pitch diameter is the center hole to center hole distance between the 12 o'clock and 6 o'clock position.

I like the fact the RandD design has no springs.

Topmast reports several manufacturers make them this way. Anyone know of other brands? What about using the high deflection plate and should I be concerned about rotation direction?

For now I sent an email to RandD, and PYI Inc asking them what is correct back plate and full model number.

I am not keen on dropping transmission while in the water just to make a measurement. I run my engine at anchor to help hold in squalls.
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Old 21-08-2016, 08:52   #22
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Re: Terminology help: Damper plate, clutch disc, pressure plate, drive damper

It would be really good if you can find the flywheel part number specified by your model and serial number. There is no guaranty that the flywheels for a manual transmission and a marine gear/automatic transmission/generator/hydraulic pump are the same, the only thing that will tell you that (almost) for sure is the serial number.

The one part number I could find is 1-12331176-0, which states that the size is 325 mm (12.795 inches), with a 129 tooth ring gear. Rotation shouldn't matter, but should be stated in the service manual.

Here's a picture comparing a 6BD1 flywheel and a 4BD1 flywheel. The 6BD1 is on the left, you can clearly see the different mounting patterns than those in the 4BD1, on the right, which is drilled for a manual clutch (pressure plate).

It won't hurt the engine to start it (or just kick it over) without the gear attached.

The picture comes from this website:

6BD1 vs 4BD1T Flywheels and Housings


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