Airbags for genset mounts

[sassriverrat]

Good Evening,

I've tried bolting down with soft motor mounts, welding down, and double motor mounting an MEP-831 generator without much success in reducing noise.....the frame of my 11,000lb (empty weight) trailer is still making a racket. I hoping someone had an idea or access to small airbags (cheap) or a source for them to direct me to!

Thanks

 

[DieselAddict]

Have you tried a horse stall mat?

 

[Ray70]

I'm really surprised a little 831 is giving you that much trouble with vibration. DieselAddict has the right idea, I tell everyone who buys a gen from mr to stick it on a Tractor Supply horse stall mat to keep it quiet and stop it from walking around.
When bolting it down you should also isolate the bolts, don't crank them down tight onto the frame.
Try longer bolts with a rubber shock absorber mount and steel washer under the head and nut.

 

[sassriverrat]

I'm really surprised a little 831 is giving you that much trouble with vibration. DieselAddict has the right idea, I tell everyone who buys a gen from mr to stick it on a Tractor Supply horse stall mat to keep it quiet and stop it from walking around.
When bolting it down you should also isolate the bolts, don't crank them down tight onto the frame.
Try longer bolts with a rubber shock absorber mount and steel washer under the head and nut.

hahaha this is cracking me up! Great minds think alike!

Yes, I actually did try 1" rubber horse stall mat! I'm using that as flexmount for the motorcycle muffler successfully. I also tried mounting soft genset mounts onto horse stall mount and all of that on the trailer. The 831 is great, but the harmonics must be just right because it makes a racket on the near wall (mounted inches in front of a container wall on the trailer.

 

[Chainbreaker]

How is this trailer normally used other than accommodating the -831 generator on it?

 

[sassriverrat]

How is this trailer normally used other than accommodating the -831 generator on it?

So despite everything people about them, I found a great use for a 989A1 Trailer!

The big reveal was going to come this summer, but if you follow "The Eastern Shore Offroad Group" on Facebook, you can see pics of the build now. I took a 20' conex box, cut the floor out, and welded it down to the 989A1 Trailer frame. The front upper deck houses the generator, AC unit, spare tire, and fuel for the generator and hydronic water heater.

 

[Chainbreaker]

Ok, a HEMAT trailer conversion. I don't use Facebook...however if you posted a couple pic's here in this thread of where the generator sits & how it is currently mounted it may stimulate some ideas from members on how to tame the harmonics you are encountering.

You know the saying... A picture is worth a thousand words!

 

[sassriverrat]

Ok, a HEMAT trailer conversion. I don't use Facebook...however if you posted a couple pic's here in this thread of where the generator sits & how it is currently mounted it may stimulate some ideas from members on how to tame the harmonics you are encountering.

You know the saying... A picture is worth a thousand words!

Fair enough!
Here ya go!
I didn’t have pics with the exhaust and all installed but it shouldn’t matter much for that. Currently the two pieces of channel are welded to the top of the platform- but only with a few tacks so they could be removed if necessary.

 

[Chainbreaker]

That picture really helps to see the situation you are dealing with. Here are some initial thoughts I have.

1. Are those 2 forward lifting rings at base of container on trailer perhaps vibrating/chattering? If so, maybe tack weld them up against the container if they will never be used again.

2. What if you placed horse stall mats under the generator all across the front and up against the container wall to go up as far as you can up to the spare tire. Maybe even hang stall mat like a curtain from the cross beam just below the spare.

3. Another option would be to apply a quality bed liner to attenuate sound/vibrations on the complete front end of trailer and vertical container wall. There are some good DIY kits. I used one on a trailer bed that I think was called Raptor (similar to LineX) and it turned out quite nice.

As I said those are just my initial thoughts. I'm sure other members will chime in with suggestions.

"Beast of a trailer" by the way!

 

[sassriverrat]

That picture really helps to see the situation you are dealing with. Here are some initial thoughts I have.

1. Are those 2 forward lifting rings at base of container on trailer perhaps vibrating/chattering? If so, maybe tack weld them up against the container if they will never be used again.

2. What if you placed horse stall mats under the generator all across the front and up against the container wall to go up as far as you can up to the spare tire. Maybe even hang stall mat like a curtain from the cross beam just below the spare.

3. Another option would be to apply a quality bed liner to attenuate sound/vibrations on the complete front end of trailer and vertical container wall. There are some good DIY kits. I used one on a trailer bed that I think was called Raptor (similar to LineX) and it turned out quite nice.

As I said those are just my initial thoughts. I'm sure other members will chime in with suggestions.

"Beast of a trailer" by the way!

Haha thank you very much!

1. Lifting rings- they will likely be used again- however, for noise deadening- I attempted to put rubber under them, the rings around the generator (which used to make a TON of noise), and on a few other places. A little 4000 is removal if need be but secures everything well!

2. I could try all across the front. I had placed real motor mounts under the generator and then additionally used horse stall mats. It was better but still loud inside that box....The inside of the box has 2" of spayed foam, then 1" of foam board (blue stuff) and then a layer of 1/2" ply. It has helped, but I'm still reading 75dBi inside the front wall (other than a "hotspot" 2/3 of the way back, the farther away I get from the front wall the quieter it is inside).

3. I could try the bed liner. Hadn't thought about that. I have rolled it out before and I have a gun for applying Raptor as well. It was good stuff!

 

[Chainbreaker]

Another idea, instead of the two steel extender channels you have the genset mounted on use a couple of wood 4 x 6's. Wood should, in theory, help deaden the vibrations going into the trailer frame.

If all else fails...another thought with a completely different approach. Weld a pivoting type hoist somewhere above the -831 and use it to unload the genset OFF the trailer onto the ground below when needed. That would decouple the genset from the trailer completely and eliminate vibration harmonics in your trailer.

 

[BobbyT]

One suggestion if you haven't tried it yet and if it will work with your front end plans, would be to move the generator location to one side and not in the center and see if that helps. Also as suggested by others, using wood mounting with stall mat isolation along with location change might help.

 

[Ray70]

Instead of bed liner sprayed on, you could use the stick-on sheets of sound deadening material designed to use inside car door, under floors etc. Dynamat is one popular brand, but there are others that are less expensive. Some are rolls and some are 12 x 12 squares.
Warm them up to help conform to the shape and stick on the inside.

 

[Guyfang]

I'm really surprised a little 831 is giving you that much trouble with vibration. DieselAddict has the right idea, I tell everyone who buys a gen from mr to stick it on a Tractor Supply horse stall mat to keep it quiet and stop it from walking around.
When bolting it down you should also isolate the bolts, don't crank them down tight onto the frame.
Try longer bolts with a rubber shock absorber mount and steel washer under the head and nut.

Want to add a note here.

When bolting it down you should also isolate the bolts, don't crank them down tight onto the frame.
Try longer bolts with a rubber shock absorber mount and steel washer under the head and nut

If you do this, and I think its a good idea, but if you do this, there is no longer a proper bond between the trailer, and gen set. About 15 years ago, there was an PU, (Power Unit) application where gen sets were mounted on very special, handmade trailers. The gen sets were mounted with a rubber "Isolater" to stop the vibrations, No one thought about Grounding/Bonding. A soldier died because of this "Non Authorized Modification". He was electrocuted. The potential for "Poor or no Grounding/Bonding is very great", was the kicker line in the AAR, (After Action Report). Two years later, another soldier suffered the same death, for the same reason. Different gen set, different trailer.

We mounted a wire from the gen set ground stud to the trailer, and later simply made a short wire with lugs on both ends and put one side on top, of the top mounting bolt washer, and hooked the other end to the bottom washer. Any way you do it is good. Just do it.

 

[sassriverrat]

Another idea, instead of the two steel extender channels you have the genset mounted on use a couple of wood 4 x 6's. Wood should, in theory, help deaden the vibrations going into the trailer frame.

If all else fails...another thought with a completely different approach. Weld a pivoting type hoist somewhere above the -831 and use it to unload the genset OFF the trailer onto the ground below when needed. That would decouple the genset from the trailer completely and eliminate vibration harmonics in your trailer.

That was basically the fallback idea- and thus I hadn’t welded the Pad eyes down- in case i would use them to secure the genset.

 

[sassriverrat]

One suggestion if you haven't tried it yet and if it will work with your front end plans, would be to move the generator location to one side and not in the center and see if that helps. Also as suggested by others, using wood mounting with stall mat isolation along with location change might help.

Sorry for the delay on this:

I can't stick it to one size or the other.....I wish I could, but the trailer tows incredibly well with the current tongue, but the current tongue is so short that with tight turns, the sides of the platform can actually go under the edges of the bed on the truck. Therefore, anything on the corners of the platform would get crushed unfortunately.

You guys have some really good ideas here, some of which I've already tried and some I hadn't thought about, but I haven't had any success and I figure airbags are the next approach. My current issue is just that I haven't found airbags that seem appropriately small enough.....
My plan with the bags was merely to have two valves and a gauge- one valve filled the bags off trailer air and the other dumped the pressure. The gauge was in between so I could see the pressure in the bags. Simple enough.

 

[Chainbreaker]

Sorry for the delay on this:

I can't stick it to one size or the other.....I wish I could, but the trailer tows incredibly well with the current tongue, but the current tongue is so short that with tight turns, the sides of the platform can actually go under the edges of the bed on the truck. Therefore, anything on the corners of the platform would get crushed unfortunately.

You guys have some really good ideas here, some of which I've already tried and some I hadn't thought about, but I haven't had any success and I figure airbags are the next approach. My current issue is just that I haven't found airbags that seem appropriately small enough.....
My plan with the bags was merely to have two valves and a gauge- one valve filled the bags off trailer air and the other dumped the pressure. The gauge was in between so I could see the pressure in the bags. Simple enough.

Edit: Actually, with my initial response below, I think I misinterpreted your intention when you mentioned using the "trailer air". I guess you are still looking to dampen the generator itself by placing the airbags "under the generator" to help isolate it from the trailer itself. Correct?

My initial reply was: "Since your now moving from the damping/quieting of the "Generator aspect" of this and looking at making modifications to the trailer itself, you should start a new thread in the SS Trailer forums section. You may get more input that way as it relates to air bags and trailer modifications to do what you need to do in order to accomplish your objective."

 

[sassriverrat]

Edit: Actually, with my initial response below, I think I misinterpreted your intention when you mentioned using the "trailer air". I guess you are still looking to dampen the generator itself by placing the airbags "under the generator" to help isolate it from the trailer itself. Correct?

Correct.

So yes, when doing any sort of slow speed maneuvering, the corners of the deck on the trailer overlap with the truck (and some trickier terrain causes rubbing...), so the current center-line location is the only spot, as tested with a cardboard box, that doesn't risk crushing the generator.

So to give you guys some ideas of what I've tried and done:

Noise Dampening
The inside wall of the container is sprayed with closed-cell foam (well over 2") so that 2x4 studs, laid flat, and the voids in between, are completely filled and cut flat. The voids have more than 4" of foam. Then, blue insulating 1" foam has been installed on the flat of the studs, and plywood mounted atop that, fastened through to the studs using screws. The studs are "floating" and encapsulated in the spray foam.

I've fabricated a 1 1/2" exhaust flange to go over top the end of the muffled MEP 831A. The flange, all stainless, makes an immediate 90 degree turn and goes vertical with stainless flexible line. The single "soft mount" to hold the weight of my exhaust is bolted to doubled horse-stall mats, creating a 1 1/2" thick rubber "tab". These tabs (1 per side of the pipe) are then through-bolted to metal tabs welded on the container. There is an Indian motorcycle muffler (OEM) that tops it off. The exhaust is supported by the conex box but is not bolted directly to the trailer- it floats via the horse mat. There's not too much noise audibly on this side. I need to get my meter back out, but if you stand a few feet back from the generator, it was in the neighborhood of 65 decibels and exponentially fell off as you backed away (which makes sense). Up close, the generator was louder through the box then the exhaust.

Vibration
The skids are tacked down to the deck of the trailer. The skids were utilized because the generator has a pair of mounting "skids" and one side would have hung off the front of the trailer and wouldn't have been supported. I originally mounted a pair of marine engine (rubber) heavy duty mounts to the skids and the generator box atop that. The meter reading inside the container was roughly 90 decibels. It changed depending on distance to the front wall with the trailer having a harmonic "hot spot" about 2/3 of the way back.

I then removed the mounts and put in a set of onan-cummins soft generator mounts. They reduced the noise to roughly 80 decibels inside. I attempted doubled-horse mat in addition to the soft generator mounts and had mixed readings between 75-80 decibels.

I don't mind a bit of "white noise" and expect it, but you can't/shouldn't sleep next to 75 or 80 decibels. One thought (just occurred to me) is to take the tractor, and using the skids, hold the generator just above the deck of the trailer (but not touching) and see what the noise does. That alone should decide what vibration is doing with the trailer. I have attempted removing the exhaust mount point from the trailer (so it was totally supported temporarily by the generator) and that didn't produce much difference (1-3 decibels).

 

[uniquify]

What happens if you temporarily put a piece of plywood or foam board vertically between the generator and conex container, preferably not touching either? Just curious if that would absorb/deflect some of the sound away from the container?

If you have a spare tire available for the truck/trailer (without the rim), another quick test would be to lay the tire on the deck below the generator as a single large shock absorber.

No idea if these will make any difference in the long run, just wanted to help you brainstorm. Good luck!

 

[sassriverrat]

@uniquify

I thought about the plywood shield but hadn't tried it. I'll give it a shot to see what happens....

The tire is a heck of an idea....I hadn't thought about that! If that works, what are your thoughts then for mounting the generator?