Isolation and Noise Reduction:
I’ve written many pages on noise and vibration reduction, and I’m hoping to bring all that material together and publish a more comprehensive article someday, but for now, here’s an overview, and a favorite email from one of the TOP DIYer States.. Texas.
DIYers are naturally interested in this topic, and some study it with intensity. Vibration is not just a source of noise, it can also be the root cause of silence, and of course that silence always arrives when you need your Generator most. One memorable email arrived here telling me of a piece of metal inside of an air cleaner breaking off and being sucked into the intake exhaust seat. The Piston top did not survive the resulting collision, and that old classic comes to mind…Simon and Garfunkel.. “Hello darkness my old Friend”
Dr. David Delapp (an accomplished DIYer) who studied at Vanderbilt,
and also taught classes there may have been the first to share some wisdom
about the topic of ‘soils’ and their ability to communicate. DIYers have a natural understanding that dry sandy soils are less likely to communicate than let’s say a layer of sandstone, but there’s entire books on the topic, and of course there are Professional Engineers that do nothing but the evaluation of soils at construction sites.
At our Easton off grid site, there are two Lister generator plants, one is under a covered end of the pump house, another in a power shed. In both of these installs, I’ve applied
lessons I’ve learned from personal observation and through DIYers around the world.
But as you might have discovered in your life, there is always more lessons to learn, or even re-learn. It’s not good enough to understand the concepts, you must make an application of that knowledge in your work.
The first basic rule is: Anything you can mount off the generator frame will be mounted off the generator frame. Vibration is a killer, electrical panels, exhaust systems, intake systems, when it comes to well designed stationary power, you need make the room to allow this, and you need make room to service every part of the generator. Use a rubber hose between intake and air cleaner, use a flexible isolator as close to the exhaust port or manifold as reasonable, and always build a condensate trap to assure that water doesn’t collect at the exhaust valve.
When you ponder how a loud speaker works, consider that your prime mover is the source of sound power and your shed, concrete slab, generator base, and all things connected could provide the same function as a loud speaker cone.
In the case of the pump house, I have fairly ideal soils. Maybe six inches of top soil with an underlying layer of gravel, it’s in a narrow valley, and likely part of a river bed at some point geological time. This soil is porous enough allow water to travel through it, and a poor communicator. I used two full length Rail Road Ties to mount the engine and generator, and I did not couple them in any way to the concrete pour of the pump house. This helps
to keep the pump house from functioning as a speaker or transmitter of sound.
At the other location, the generator is inside the building, and since I built this shed starting with a clean sheet of paper I applied knowledge of local soils and isolation.
The first step was to pour a rather generous concrete pad with rebar, and having pieces of six inch eye beam with the tops set at a height that would be about an inch below floor joists with a generous amount of the beam locked into the concrete pour.
The floor of the power shed was constructed with a hole in the floor, and a rubber apron around the perimeter of this opening to assure a clean decoupling between generator base and frame and power shed. In conjunction with the effort, your design can include a rubber isolator on top of each pier block that the power shed sits on.
Don’t forget to decouple the exhaust, and intake, and consider using all that fiberglass insulation in the wall between studs as part of your air filter. A connection into
the wall at the bottom, and on the outside, use a hole saw to place a series of
intake holes, and place store-bought breathers, or make your own from screen to
keep bugs and vermin out. Very effective filter, and unless you’re in a bad spot, you’ll likely never need to change the filter.
Remember, motorcycles are a great source of ideas, vibration, metal fatigue, noise are things engineers have had to address in a number of ways for years. Go back to the two strokes and note the use of springs to hold the exhaust pipe into the exhaust flange, look at the different methods used since the 1930s, and then note how poorly it has been done in recent times. I was totally disgusted to by the lack of engineering I found in the Artic Cat 2003 Quad in the exhaust system. Engineers did an impressive job
on suspension, and built what I’d call a first class work horse in other
respects. The Engineer that designed the exhaust system gets an F minus grade, and it’s unfortunate that the exhaust system goes into resonance at slow trail speeds…. right where I like to ride. The exhaust header is hard mounted to the engine, and the exhaust hard mounted to the frame! In 2004, they did it right, they applied the same common sense approach used in motorcycles and ATVs for years and years.
He’s an email I received some years ago and put on my CD…food for thought. I’ve said it about 100 times or more. DIYers are from all walks of life, Professors, Medical Doctors, Engineers, Programmers, Farmers and Ranchers. All of us need remember….NEVER underestimate a FARM Boy and what you can learn from him. Do pay special attention… the Farmer provides Roark an engineering solution, and also provides some insight into
marriage and what you might expect from Women folk as it pertains to generators. They generally appreciate the power during an outage, but don’t expect them to admire your hardware and the thought you put into it. Email from Roark follows…
I’ve been enjoying your webpage(s) for several months now,
and you’ve almost convinced me to play with a Listeroid or Changfa. FWIW, I’m an engineer by training (20 years
of billing myself as “User-Friendly LiveWare” doing embedded code on
Intel and Motorola uP’s) and have some direct exposure to EMP effects, so I’m
looking at the KISS diesels with a very lecherous eye.
Of late I find myself working in the field of law, in a tiny
little town of 1611 folks known as XXXXX, TX.
Power here is so bad I finally bought a monster Baldor genset with a
John Deere 4045TF250 pushing a Stamford 80KW head. It holds 175 gallons of diesel in the
belly-tank and sounds like an F14 Tomcat on nitrous. 🙂 Loud mutha, but it’ll get ‘er done when the
chips are down. I found out the hard way
that federal Judges don’t give a flying flip if aliens abduct your entire
town… they still want you on-time / over-target with maximum ordnance load
and won’t take excuses like “the power was out for 2 days and we all had
to take cold showers”. Mr. Baldor
cured that. Mostly. 🙂
Weird things happen in a country setting, ie, people will
stop and talk to you without trying to sell you something. You meet folks with zero education but a ton
of genuine smarts, too. When I first
installed this creature on a dedicated 26,000 lb concrete slab, it rocked the
china out of the neighbors cabinets. To
fix it, I tossed the “commercial” grade silencer for a
“critical” grade unit ($500) and the acoustics got much better… but
the danged thing still rocked the boat nearly a block away. When it was running, I could FEEL it from my
home two blocks away. Transmitted
vibration was nothing short of intense.
Any 4-year wonder calling himself an “engineer” will tell you that a 26,000 lb concrete slab is absolutely OVERKILL for a 5000 lb live load. And I’m here to tell you
that 16×13 foot slab did nothing more than provide a firm coupling to terra
firma. It had me puzzled, but I figured since I only run a couple of times a week (!!!) it wouldn’t be a huge issue.
Then one day this grizzled old farmer was admiring it, and I fired it up for him. The ground moved (predictable, that), but this guy just looks at it and says “I’ve got this
old Lister that had the same problem. I just put a trailer mat under it. Fixed
it so the wife doesn’t complain near so much. At least about my generator….”.
FWIW, a “Horse Mat” or “Trailer Mat” is just black, textured (pebbled) rubber mat that folks use on the floor of their horse trailers. It gives the horses a good footing and prevents trailer rash when you mash on the brakes because some yuppie in a Beemer couldn’t see you over his latte. This mat is some HEAVY stuff too. A 3 foot by 7 foot sheet that is 1 inch thick must weigh something like 60 lbs. It’s UV stable, waterproof, and isn’t bothered by diesel. Locally “Tractor Supply” has it in stock year-round and will help you load it.
So the next weekend I borrowed a friends trackhoe (15,000 lb
boom capacity… 5000 lb generator weight, you do the math… heheheh) and
pulled the big generator up a few inches while I slid a 1 inch thick rubber mat
under the belly tank. I dropped the genny back down on it, screwed it back down, connected the load bank (homebrew, 16 ea 4500 watt water heater elements connected to a 2 hp pump fed from the koi pond) and fired it up. No more rattling dishes.
In fact, a Dixie cup full of water set on the ground beside the concrete slab doesn’t even ripple. The neighbors loved it. With this critter at full song driving the entire practice on a wartime footing, you can’t even tell it’s running if you’re inside the building.
That mat has sat under my Baldor 80KW for something like 3 years now and it still looks and performs like new. Total cost for the sheet was about $25. I got liked them so much I got a few more and threw them in my horse trailer for their “intended” use. (I suppose the horses tow a bit quieter, but you’d never prove it by me. hehehe)
Oh yeah: The Baldor, with the switchgear, my homebrew loadbank, that 400 amp transfer switch and all the web-based interface stuff cost me around $27,000. I did the install myself and am proud of it. Yet I’m giving serious thought to replacing it with a 2-cylinder Listeroid or similar. Why? You were dead right about the reliability of an AVR embedded in the **ROTOR**. Would you believe the feedback connection between the AVR and the stator output is via optical fiber? Not kidding. It shines a beam of IR light right down the middle of the shaft!. Looks great on paper but doesn’t pass the KISS test. So far I’ve replaced it once (thank God for warranties!). Currently I’ve got a total of 380 hours on the meter, with meticulous care, and bi-weekly 20 minute exercise periods. But I’m still scared to death we’re gonna get a lightning strike (very common) and it’ll be out of
commish when I need it most. As you said, you can’t repair these things. Or at least… I can’t. Or you. Or the guy next door.
Yeah. I think you talked me into a Fugly Listeroid (or similar) with an ST-type head. I can run the whole shootin’ match very comfortably on 12-13 KW peak… or about 8KW sustained. I just ditched my last power-hog copier for something much leaner, and as we mature we’re learning how to monotask both to save energy and to live longer.
I really think you need to tell your readers about the
trailer mat trick. I wouldn’t have believed it if I hadn’t seen it with my own eyes. (Pictures available if you’re interested).
In closing.. Roark, I hope you are doing well, and I still laugh when I read your wonderful account of reality.. too bad it’s not typically part of life in DC…
This rubber matt sold at farm supplies is cheap! buy a similar product elsewhere, and it’ll likely be a lot of money!