Author Topic: Need help selecting vibration isolators (aka motor mounts)  (Read 613 times)

Randybee1

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Need help selecting vibration isolators (aka motor mounts)
« on: August 05, 2017, 03:19:05 PM »
Hey Guys, I have a Perkins 402D engine that drives a 7.7kw ST head. It is mounted on a 2x2 steel frame. I've gone through 2 iterations of different mounts and neither has reduced the vibration. At first I tried something like this:http://karman.com/ks-series-304-stainless-steel-cylindrical-isolators

As I tightened the belt for the 2 pulleys these things just made a 90 bend! It was then that I realized I forgotten about shear so I then went to the Karmen Rubber page and calculated the correct (or so I thought) isolation pad. These did nothing
http://karman.com/products/selection-steps

I know this is not rocket science so if anyone can help I'd greatly appreciate it. I'll post some pics later... after I figure out how.

Thanks
Randy


Randybee1

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Re: Need help selecting vibration isolators (aka motor mounts)
« Reply #2 on: August 05, 2017, 07:18:18 PM »
I'm using an 8 rib flat belt. I'll read up on how to post a pic and try to get something up soon.

xyzer

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Re: Need help selecting vibration isolators (aka motor mounts)
« Reply #3 on: August 06, 2017, 04:14:14 AM »
Is the engine isolated with belt drive to solid mounted gen head?
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Randybee1

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Re: Need help selecting vibration isolators (aka motor mounts)
« Reply #4 on: August 06, 2017, 08:44:41 AM »
Yes

I tried registering on the LEF Gallery site so that I could post a few pics but it said I was banned... :o
Any other ways to post a picture?

AdeV

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Re: Need help selecting vibration isolators (aka motor mounts)
« Reply #5 on: August 06, 2017, 06:36:30 PM »

I tried registering on the LEF Gallery site so that I could post a few pics but it said I was banned... :o


Interesting.... that shouldn't have happened... Mind you, I got my admin password wrong a few times the other week and it banned me!! And I run the damn thing!

I'll have a look into it for you (er, as soon as I remember my admin password), it probably just needs the anti-spam stuff turned off, or loosened a bit.


Meanwhile... re: motor mounts, we used some pneumatic anti-vibration mounts on our motorhome to isolate vibration from an auld Ford diesel with a gen head attached. I have no idea what make/model they are, but I know you could attach a foot pump or compressor to alter the pressure inside to suit the application.  One difference, we mounted the gen head and engine rigidly, and put the whole assembly on AV mounts. I suspect if you leave the gen head rigidly attached, you'll encounter belt slap and excessive wear - not a scientific opinion, just my thinking.
Cheers!
Ade.
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BruceM

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Re: Need help selecting vibration isolators (aka motor mounts)
« Reply #6 on: August 06, 2017, 07:00:06 PM »
+1 for Ade's comment about rubber mounts for the engine alone.  That's going to be a serious bending load on the mounts because of the tension required for ribbed belts, and the belt tension varies with engine movement.  No good.

Engine and generator hard to frame, and isolate the frame is the most widely used approach. 

glort

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Re: Need help selecting vibration isolators (aka motor mounts)
« Reply #7 on: August 06, 2017, 11:00:07 PM »

I tried some Subaru Gearbox Mounts some months ago to mount my Ruggerini 12 Hp engine and they were too soft.
Being from a car I was expecting the opposite but even just with the engine alone, the thing shook and vibrated far more than acceptable.  The gearbox mounts were a good shape and size for mounting but the rubber in them is way too soft. Guess I'll have to try some engine mounts which I'm sure will be too hard but who knows?

Clearly the rubber compound is different as well as the shape and size of it in the mount.

On a Diesel water pump I have the engine and pump are coupled together on a simple rigid steel mount which is then rubber mounted.  Makes sense as with a belt on a rubber and solid mount unit you'd never get fixed tension until the mounts were at max deviation in that direction which I think would cause them to act as solid rather than flexible.

Randybee1

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Re: Need help selecting vibration isolators (aka motor mounts)
« Reply #8 on: August 07, 2017, 05:04:51 PM »
Glort, My setup is similar to yours. I'll try (again ) later today to get registered on the LEF gallery so I can post a few pics.

Randybee1

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Re: Need help selecting vibration isolators (aka motor mounts)
« Reply #9 on: August 08, 2017, 10:37:07 PM »

Here's a close-up of my engine mount. It is a 200# mount. This cuts down the vibration significantly as well as the 100# mounts I tried. Once I hooked the gen head up (belt and tightened) the vibration increased.



Here is a general set up showing the gen head.  I was thinking of adding some isolation pads for the whole thing to set on. Any suggestions? Would adding pads to the feet of the generator do anything?


Randybee1

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Re: Need help selecting vibration isolators (aka motor mounts)
« Reply #10 on: August 08, 2017, 10:38:45 PM »
Not sure why there are 2 pics of the same thing. Here is the close up of the pad