Air Spring Isolators for Generator and more noise reduction - 2000 Endeavor

[Ted DuPuis]

On my 2000 Endeavor I have always hated the generator. It's really loud, and the vibrations are noticeable. Last year I did 1200W of solar installation on the roof to help alleviate needing the generator, and that's been successful in making the generator unnecessary anytime except for when the HVAC is required (I deleted the propane heater to make room for a residential fridge, so the generator is needed for any heat when the engine is off). I love the solar install and can recommend it, it's not only eliminated the need for the generator during decent temps, but by shading the roof from direct sun, it improves the interior comfort on hot days even with the AC running.

My next projects attacking the generator noise are now more focused on the generator itself.

On my 2000 Endeavor (and I would assume other Monacos of that era) the generator is hard mounted to the frame - at least if you want to call it that. Really they did a very bad job with this. The tubing for the front generator mount is ok and bolted more securely to the frame, but the rear mounts are thin tubes only welded to the frame on one side, with rectangular tubing then mounted in the wrong direction that has bent over the years and I've already had to weld previously. Honestly I'm surprised that the generator hadn't fallen out already, this really is poorly done for something structural, and it's also very difficult to remove the generator for service. It also will transmit all vibrations from the generator to the bus. I believe that there are motor mounts inside the generator (who knows what condition they're in). I talked to one owner of a 2003 Endeavor whose generator was much quieter than mine, and he said they'd added wood mounts in there, so maybe they got enough complaints about this setup that they "fixed" it.

I'm going to take a page from what's done on higher end RVs and add air springs to isolate the generator. After doing some digging, one of the part numbers used is Firestone W01-358-7001. I found some for sale on eBay that are on their way to me, and I'll go from there. There are a lot of other things that they do on those RVs with respect to making things quieter, but this should address some of the noise and most of the vibrations we feel in the RV.

The basic plan is going to be to create a bed that the springs will mount to (ideally as far towards the edges of the generator as possible), mount the springs to it and then to the existing bed that the generator sits on. Grind off the existing generator bed from the frame, and weld the new bed onto the frame. I'll need some air lines and then a controller to set the pressure correctly, and tie into the existing air system. I'm planning to at least start off with the same pressure at all springs, as I don't think there's enough of a weight different front to rear to warrant different pressures. We'll see if I'm right on that or not.

This sounds more complicated than it is really given that it's a pretty simple frame and only basic welding required. The generator is something around 450 lbs so we're not talking really all that much weight no matter how you look at it.

Hopefully I can get this done over the winter before our next trip, and we'll see what kind of difference it makes. I couldn't find a direct thread of anyone else doing this (at least as a DIY project) but I've found some others that indicate that it does help, and I would expect the high end coach makers wouldn't do it if it didn't actually do something.

Any thoughts on things to consider in this project are welcome.

[JNSNWT]

I commend you on your problem solving aptitude.

Did you consider adding “sorta soft” solid rubber mounts before deciding to go the air bag route? I don’t know which genset you have but it might be a good idea to get an exploded diagram and see if there were any vibration dampeners from the factory. If there were factory dampeners you know that 20 year old rubber has left the chat.


Replacing the OEM dampeners can only help your efforts.

[SteveJ.]

We have installed rubber dampers on our much lighter Microlite genny and it has made a significant difference in the vibration and sound level. In combination with an Air Command rooftop unit we can actually hear ourselves think.

I did kick my own butt for not taking before and after sound readings, but it is substantial and worth the effort.

[153stars]

Gas MH owners report less interior noise using Dynamat on the doghouse. My OEM on 95 DP had open diesel genny so there is some egg crate foam a type of fiberglass pads for heat and noise. Old genny was replaced with Generac quiet boxed unit.

[Ted DuPuis]

Originally Posted by JNSNWT

I commend you on your problem solving aptitude.

Thanks. As an engineer, this is what I do.

Did you consider adding “sorta soft” solid rubber mounts before deciding to go the air bag route? I don’t know which genset you have but it might be a good idea to get an exploded diagram and see if there were any vibration dampeners from the factory. If there were factory dampeners you know that 20 year old rubber has left the chat.


Replacing the OEM dampeners can only help your efforts.

I did consider putting on some rubber dampers (and also looked at some automotive liquid-filled dampers. In the end I decided that, given the need to address the factory generator mount falling apart anyway, and the fact that the cost difference wasn't going to be enough to really bug me (I did find some good prices on the springs I wanted on eBay), it made more sense to just shotgun it and do it once with what should be the most effective solution.

I'm sure that any motor mounts internal to the generator are original, and certainly worn out. I'd strongly bet that the generator has never been out of the RV since it was built 23 years ago, and at some point I will pull it and do a more significant service on it (including replacing the factory internal motor mounts). If I design this mount correctly, it should make doing that sort of work easier. Key word being "should".

Originally Posted by SteveJ.

We have installed rubber dampers on our much lighter Microlite genny and it has made a significant difference in the vibration and sound level. In combination with an Air Command rooftop unit we can actually hear ourselves think.

I did kick my own butt for not taking before and after sound readings, but it is substantial and worth the effort.

That's a good data point, thanks. I have a dB meter somewhere that is cheap but has worked well. I don't know where it is now, and hopefully I can find it for this. But if not, I'll go by how much quieter I feel it is and forego the scientific readings.

The rooftop air units we have (Dometic Penguins) are not particularly quiet, and the compressor kicking on and off is especially audible. It's not awful and I don't mind the white noise for sleep. I've got some other thoughts there but nothing immediate.

[Ted DuPuis]

The first of my air spring isolators showed up just now, with the other three supposed to show up before the end of the week. I'll need to go hold it up around the generator in the various locations to see how things fit and plan out exact locations to mount these. I've got ideas already, but always good to hold the things up in their locations to see for sure.

The forward bay on the driver's side (right in front of the front wheel) has an air manifold and I'm planning on using that to provide air to the system.

I found the Firestone air spring spec sheets and from those, it looks like I will probably only be running 10 psi in these air springs. That's low but nothing wrong with that. Firestone specs them at 0-100 psi at operating height (that part is important). From playing around with the spring some, I think it will work as intended.

Now to start planning and fabbing things up...

[Ted DuPuis]

I've gotten some time to play around with this project, including getting the old mount off. If you have a 2000ish era Endeavor like mine, I can't express how disgusted I am with this original "design" if you want to call it that. I can't believe the generator hadn't fallen out of the RV going down the road, and I can say. with certainty that it's never been removed. None of these welds were complete, full, or remotely good. Any intersection between two pieces was welded on a maximum of 2 sides, most of them were welded on 1 side, and only part way across. The resulting "frame" was exceedingly flimsy upon removal.

Even if this does nothing for noise or interior vibration (I'm pretty certain it will), at least my generator will be properly attached to the bus and removable/serviceable.

I'm going to be able to get the air springs pretty close to the 4 corners of the generator, and that's about as optimal as I can get. I've got 1/4" angle iron that I'll weld on all sides at each intersection, and the end result should be something that's sturdy and beefy to hold the generator up.

[jacwjames]

Just another reasons why owners should inspect all aspects of their rigs.



I do most (+95%) of my own maintenance and make sure to look at welds etc. My generator is on a slide and appears to be pretty well built, that doesn't mean that something couldn't fail. If you don't look you won't find problem, I'd rather find a problem before it turns into disaster.

[Ted DuPuis]

I can't speak to other Monaco products of the era, and maybe the Endeavor was considered "lower end" enough to skimp in some areas - obviously the lack of the generator on a slide was one area, as well as the overall mounting "construction". Pretty sure my 10 year old could both come up with and execute a better design.

Unfortunately this is not surprising and I've found other areas of the house "box" to be similarly poorly done. Welds on 1 or 2 sides of the 1/8" square tube or angle iron, just flimsy. The mild steel by itself isn't necessarily a problem and you don't have to go stainless unibody like a Prevost, but at least do complete welds so that you're maximizing the structural rigidity of what you've got. This was just sheer laziness.

After thinking on it some, I think I have a good idea of how I'm going to go about constructing the mount. So over the weekend I can hopefully get the steel cut, drilled appropriately, put in place, and welded together.

[JNSNWT]

Glad to hear you are making progress.

I agree the construction method is not optimal it has done the job for 23 years.

[wamcneil]

Originally Posted by Ted DuPuis

The forward bay on the driver's side (right in front of the front wheel) has an air manifold and I'm planning on using that to provide air to the system.

Following... I'd sure like to quiet mind down...
Is there any reason to connect the mounts to coach air? I can't imagine the rate leakage at 10psi will be much of a factor. Seems like you could put a Schraeder on each one and probably never need to air them up again.
Assuming they're all connected to a manifold, if the load's not perfectly balanced, could it settle on one end and raise on the other?
And what about lateral compliance? Will the air springs prevent the whole genny from moving violently side/side when the bus hits a bump?
Cheers,
Walter

[Ted DuPuis]

Originally Posted by wamcneil

Following... I'd sure like to quiet mind down...
Is there any reason to connect the mounts to coach air? I can't imagine the rate leakage at 10psi will be much of a factor. Seems like you could put a Schraeder on each one and probably never need to air them up again.
Assuming they're all connected to a manifold, if the load's not perfectly balanced, could it settle on one end and raise on the other?
And what about lateral compliance? Will the air springs prevent the whole genny from moving violently side/side when the bus hits a bump?
Cheers,
Walter

All good points, Walter, and I had considered going the shrader valve route. My assumption is that the weights at each corner won't be different enough that each bag will require differing pressure.

My thought on hooking it up to bus air is essentially that I need air, and I have on-board air, so may as well use it. I also like to design systems such that they don't require babysitting while on the road, they should be essentially self-sufficient. There's no reason why one couldn't just do shrader valves, and it definitely would be a simpler setup.

Firestone's instructions say that when using these air springs you should have stops on the equipment in all directions to prevent it from moving too much under load. However, keep in mind that this generator weighs under 450 lbs, and at 100 psi (max rating for these springs) they support around 1,100 lbs, each. I'll play with it some, but I don't believe that the varying G forces the bus will produce in normal driving are enough to overtax the springs. From what I can see, I don't see limiters on these mounts in the larger luxury RVs I'm copying.

I wouldn't be worried about settling, either. If weights are different at each corner then the differences would be in height, it wouldn't settle one direction. The way I'm setting it up all springs will see 10 psi, so then physics will just dictate how far up that 10 psi pushes the spring.

One thing I am going to do, though, is put some bump stops so that if the air leaks out they don't collapse the springs. It said in the documentation it's not good for the springs to be "operated" (in other words actually having motion) below a minimum height. So I found some bump stops on Amazon that will prevent it from bottoming out fully.

[jacwjames]

Not sure what kind of clearances you will have away from other structure but you could consider bump stops on those in case the generator does want to move. Using 4 of the air springs should limit movement.



We used heavy duty & larger springs in the mining industry to support vibrating feeders. Lots of weight but the springs performed. They lasted a long time with thousands of hours of vibrating action, the only thing that would cause them to fail is spillage near the spring and the rock rubbing a hole into it.

So if you have clearance around the base of the air spring you shouldn't have a problem and a periodic inspection would help.

[Ted DuPuis]

Thanks Jim, appreciate the data point.

There's enough clearance around everything that I'm not worried about the generator being able to move enough to touch the body unless I'm having some kind of off-road excursion (read: crash).