Generator vibration isolator mounts

richard5933 · January 13, 2018, 05:39:42 AM

Anyone have any suggestions for rubber mounts I can use under my generator feet to isolate it from the bus? There are four horizontal mounting feet under the genset which are connected to the slide with mounts. I'd guess that there were springs used under it at one time, but they are just about fully compressed right now. The way it's parked right now I can't get great photos, but here is one of the bay with the genset.

I ran the genset this week when it was warmer to give it a full warm-up under load, and I realized it's not the noise that really bothers me inside the bus as much as it is the amount of vibration that is transmitted to the bus body.

There are two mounting feet under the front portion of the Perkins and another two under the Kohler generator head. Best I can tell is all four mounting feet are flat on the bottom and parallel to the slide on which they sit.

The Perkins probably weighs in at 450-500 lbs. The Kohler adds at least another 300-400 lbs. Whatever I use will need to be robust enough to withstand the load and still reduce vibration as much as possible. Fortunately the exhaust, fuel, and coolant lines are all connected with flex lines so the height can be a bit different without problem. I also have a little head room so I'm not worried about hitting the top of the bay.

Thoughts or suggestions?

Thanks.

oldmansax · January 13, 2018, 05:44:08 AM

I used some I bought from Grainger. Use ones that match the weight of the unit. Too small and they will compress, too large and they will transmit the vibration instead of absorbing it.

TOM

luvrbus · January 13, 2018, 05:45:08 AM

Air bags or gel (silicone) mounts are the quietest you can get those from Dick Wright (Wrico) and others places

chessie4905 · January 13, 2018, 09:11:10 AM

You can also put lead strips between the slide out rails and body in addition to different mounts. Also looks like you need to line compartment with some acoustic foam of some type. Don't forget ceiling of compartment.

richard5933 · January 14, 2018, 08:07:07 AM

Thanks for the replies.

The compartment is already lined with pretty nice foil-backed foam with a metal mesh cover for protection. Looks like it was done recently.

I just went and looked again at the mounted currently in place. They are approximately 1-1/2" high and the bolts that mount it to the slide look to be about 4-1/4" center-to-center.

luvrbus · January 14, 2018, 08:15:06 AM

Those are easy found at marine dealers that is a S type

chessie4905 · January 14, 2018, 10:31:08 AM

I think back when those Koehler 12 kw gen sets were installed, they were referred as marine units

richard5933 · January 15, 2018, 04:18:44 PM

I've not had any luck finding them online. I'll check with one of the bigger boat yards here in Milwaukee tomorrow. Otherwise, I'm open to suggestions for places to get them online. What seems to be hard to find is the 4-1/4" (108mm) spacing on the two bottom holes.

bigred · January 15, 2018, 04:46:10 PM

Quote from: richard5933 on January 15, 2018, 04:18:44 PM
I've not had any luck finding them online. I'll check with one of the bigger boat yards here in Milwaukee tomorrow. Otherwise, I'm open to suggestions for places to get them online. What seems to be hard to find is the 4-1/4" (108mm) spacing on the two bottom holes.

Don't know where you would find them ,but the one in my conversion has four small air bags .Might be worth giving Power-Tech a call to see if they can supply these things.

chessie4905 · January 15, 2018, 04:58:13 PM

They look like you could substitute engine mounts from a foreign 4 wheeler. Looks similar to engine mounts on my 2003 Suzuki Vitara. Might even use ones from a power tech unit. Those are surely age hardened and contributing to noise and vibration.

richard5933 · January 15, 2018, 05:18:33 PM

It will be pretty difficult to drill new bolt holes without pulling the generator. I'm hoping to replace them one at a time while keeping the generator on the slide, perhaps by loosening them all a bit and then leveraging them out one by one.

To do this, I'll need to get replacements with the same bolt patterns. It looks like lots of boats used Perkins (and similar) engines over the years, and it looks like there are literally dozens and dozens of mounts available out there. I just need to find one of the old school boat yards - the kind with the guy behind the counter that has all the parts numbers memorized. Otherwise, I'll keep searching through these sites one by one till I find the part number I need. Got to be out there somewhere.

eagle10 · January 15, 2018, 07:42:34 PM

I have a Perkins that I recently bought 2 new air bags for. Called Perkins and they were about $75 each as I remember. Less vibration and no more air leaks.

scanzel · January 16, 2018, 03:41:21 AM

www.globalindustrial.com look at Vibra Systems part CMSS-2 rated for 700 lbs pretty close to what you have. You may want to remove one temporary to get better look and sizing this may help may help you get a very close replacement.

richard5933 · January 19, 2018, 02:53:46 PM

Found a company called AV Mounts that had something I think will work.

https://www.avproductsinc.com/mobile-marine/ds-mounts.html

Kind of nice, in that they are able to order them with the rubber hardness set for the specific weight being carried. Too hard and vibrations will be excessive, too soft and they will fail from the weight. I think that I've got them dialed in with the softest rubber that was above the necessary weight rating.

I hope to get them installed during our next winter warm-up, if we get one that lasts more than a few minutes. Otherwise it's on the list for spring. Looking forward to not rattling the glass to run the gennie.

richard5933 · March 22, 2018, 03:51:24 PM

Finally got the new generator mounts installed. The hold-up was due to having to wait until I moved the bus, since it was parked on a slight slant that made moving the generator on its slide a bit tricky. In the end I had the bus in the shop this week for some other work and just had them install the mounts. The guys had a bit of trouble since the metric bolts on the new mounts required the mounting holes to be enlarged, and I would have really had trouble doing it given the limited access. They said that the rubber in the old mounts had hardened pretty much all the way, so the new ones should be a drastic improvement.

I went with these: https://www.avproductsinc.com/mobile-marine/ds-mounts.html

The difference in before and after is like night and day. The noise is the same, but the the bus no longer vibrates like crazy when the generator runs. Before, the whole bus shook and it was really hard to even think. Now the bus sort of hums along with the generator - much nicer.