Quietening a generator

Since I'm working on a boat in a yard without power, I've splashed out on a generator to power tools etc. It's from Machine Mart's cheaper range - one of these: http://tinyurl.com/ya3f8za .
The generator works fine, but being a cheapish petrol one in an open frame, it's quite noisy. I don't mind myself, but at weekends there can be quite a few people working on their boats, and it feels rather anti-social to be running a noisy generator when everyone else is quietly cleaning and painting things in the sunshine.
Are there any cunning tricks to reduce the noise?
Cheers,
Pete
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Pete Verdon wrote:

mass and padding round it.
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The Natural Philosopher wrote:

I'm wary of just putting the whole thing in a duvet-covered box, as it seems likely to overheat.
Pete
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Pete Verdon wrote:

A blockwork wall around it would probably be more effective anyway. Soft materials stop high frequency noise. Heavy materials stop low frequency noise, which can travel further.
Colin Bignell
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OK - unfortunately it does need to remain somewhat portable, as I have to drive to the boatyard each weekend with generator, tools and materials in the back of my Polo. I could leave a certain amount of low-value stuff (eg a few breeze blocks to construct a silencer) under the boat, but a generator-sized blockwork compound, even dry-fitted, is starting to take the piss.
Cheers,
Pete
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It was a very long time ago but I remember someone who had converted a single decker bus to a mobile home. He had a generator underneath the floor with a series of small exhaust boxes joined with U shaped pipe. As I remember it was quite neat and quiet.
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On 27 Jan, 22:58, Pete Verdon
Turn it off when you're not using the angle grinder.
Swap it for a tenner's worth of 2kW building-site 4-stroke genny, which is much quieter (and yes, a tenner )
Hide it inside or behind a baffle, which could be the boat you're working on, oild drums etc. Just blocking the line-of-sight helps.
Do something drastic to the silencer, probably involving welding, such that you can attach a length of flexible exhaust hose (you're a boatyard, scrounge a knackered old bit off something). Route this into a "pot" silencer, which is your local nearest equivalent to a cast iron bucket (or chimney pot). Stuff a layer of loft insulation on top.
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Andy Dingley wrote:

I don't leave it running unnecessarily, but sometimes it's powering a heater helping some epoxy or fibreglass to cure in the current weather. This of course can look like I'm inconsiderately leaving it running for no reason.

This is a 2-ish KW 4-stroke genny, and I assumed it *was* the kind of thing used on building sites.

I'm intrigued. How?

Last weekend I did put it among some of the less actively worked-upon boats at the end of the yard, which helped a bit. But I don't want to put it too close to someone else's boat - just after I'd packed it away the owner of the boat I'd hid it behind/under turned up and started taking off the covers - I'd thought the boat was basically abandoned. There are also people living aboard at some pontoons just next to that end.

This sounds promising. I haven't looked closely but I suspect the exhaust (don't think it has a real silencer) is too thin for me to weld to, but I could probably clamp something in place. One of my jobs is replacing the knackered exhaust hose in my boat, but annoyingly I've already thrown the old one away. I may have a short offcut from the new one once it's fitted, but I'll probably want to use the genny quite a bit before then. Nobody else seems to be doing engine work, but I wonder if I can find some other kind of hose that won't melt.

Don't quite follow that. Just pipe into open-topped pot, with the top blocked with glass wool?
Cheers,
Pete
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On 27 Jan, 23:28, Pete Verdon

Ah, I hadn't looked at your link. Yes, that's a lot better than one of the Happy Shopper converted lawnmowers.

Plant sale the other week. Three of them went, no-one buying. usually they'll raise 50 easily, these went to the same chap for a tenner each. I'd have had one myself, except that I already have several and no room for more tat.

Can you get a spare bolt on flange, or any flange that matches the studs & bore? Then abuse that, with Jubilees if necessary.
You need a few feet of flexi, which is hard or expensive to find, then it's easy and you can use bits of old Ford escort, or whatever you have. Most silencers have to be lightweight, which means noisy. If yours is fixed, then you're laughing. Anything that combines path length and an internal volume equal to ten or twenty times the cylinder capacity works, so long as it doesn't turn into a drum itself. A perfectly good silencer for a stationary engine can be made from a labyrinth of stacked breezeblocks (the hollow sort), where it uses mass and internal expansion volume to quieten the noise. There's always a bit of high frequency left, so you stop that with a thin wad of rockwool.
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In message

How about PORTABLE STAINLESS EXHAUST . 1.5M LONG , 30MM WIDE
<http://cgi.ebay.co.uk/PORTABLE-STAINLESS-EXHAUST-1-5M-LONG-30MM-WIDE_W0Q QitemZ370324020538QQcmdZViewItemQQptZUK_BOI_Industrial_Tools_Generators_E T?hash=item5639081d3a>
http://tinyurl.com/yaw67qf
Ebay item 370324020538

--
Bill

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On Thu, 28 Jan 2010 00:14:12 +0000, Bill wrote:

I was about to suggest eBay as a sourcec of various diameter flexable exhaust pipe. I don't remember it being particularly expnesive either.
Might be able to get a suitable silencer from the back of Quickfit or similar.
--
Cheers
Dave.




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Andy Dingley wrote:

:-)
As I mentioned, one of its uses is to run a 2KW fan heater to warm up internal spaces enough for fibreglassing. Can't see one of the little 2-stroke fart machines doing that.
Mind you, this 2-stroke claims the same noise level as the 4-stroke I have: http://is.gd/7byM4

Well, I'd gladly have paid 50 myself, but finding such a sale (even knowing they exist) is a lot less convenient than popping over to Machine Mart and being back in the boatyard 20 minutes later.

Doubt there's an official spare, and I haven't seen where the little pipe actually attaches to. In the Machine Mart picture, the left-hand, shiner, black box is the exhaust, presumably a crude silencer. The actual outlet is the round hole in the middle, which if I remember rightly has a small pipe inside it, ie not just an orifice in the sheet steel.

I was thinking in terms of either fitting a small-bore pipe around the little pipe as it exits the black sheet-metal box, or if I could only get wider boat flexi hose, wedge that against the box so that the exhaust is firing down it but not actually sealed to it. Not fantastic.

Why a few feet? Is this for gasses to cool down or something? Anyway, I'm kicking myself for throwing away the perished old hose off the boat - would have done for this job (as long as I could have sealed the input end).

How about I put a 90 bend in a length of 15mm central heating pipe, wedge it into the genny exhaust (looks about the right size) and put the bottom end in a bucket of water? Probably completely futile, right? :-)
Cheers,
Pete
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On 28 Jan, 00:16, Pete Verdon

Farmer's Guardian.

Try unofficial? There are only so many combinations you can make with two studs and a hole. It's often easier to connect to the block that to the silencer outlet.

Good static silencers are big hefty boxes. Your genny is on wheels. You just need something to handle alignment and vibration.

That length of that diameter is going to be very restrictive, especially once the exhaust has passed through one silencer and expanded. It could reduce engine power, make it run over-rich, stop it running altogether, and might even get noisier. The bucket of water is good, but watch out for back siphoning when cooling down - you need some good height between the engine and the water (you're in a boatyard, there will be someone who knows water silencers).
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On Jan 27, 10:58pm, Pete Verdon
If you were to shut it in a box (like a 10ft ISO lined with insulation), make sure it can breathe (and you or anyone else don't die from CO poisoning). Cunning? What about an audio rig that plays inverted sound waves which cancel out some of the noise? The likes of Klark Teknik, Behringer, etc no doubt have solutions to delay and phase the waves for optimum effect.
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Pete Verdon wrote:

connecting a bigger silencer onto the existing one can help enormously. and they are free form any kwickfit type place, its nominally the pipe into a silencer that fails first, so lots of usablesilencers end up in thescrap bin.
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On 27/01/2010 22:58, Pete Verdon wrote:

The usual solution (adopted by the water board who have to run pumps in the street when there's a break in the mains) is to surround the offending item with straw bales. Far enough away not to be a fire hazard, of course.
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My uncle had a one-lunger from which he ran the exhaust into a hole in the ground filled with clinker/stone etc. I don't think he had a muffler/silencer on it all. Seem to remember a much quieter 'wuffling' noise!
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We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Pete Verdon
like:

Build a canopy with vent holes. Essentially that's what the industry does, but you could molish one from ply lined with acoustic material. Of course, a decent silencer is necessary.
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In my experience quietning the exhaust doesn't help much on many open-frame generators, as a lot of the noise is mechanical from the engine and inlet noise. An enclosure round it will help, but it's not very portable then. As a quick test hold an old damp towel over the exhaust outlet while it's running (only for a few seconds, before it chokes itself), to see how much quieter it gets. Althought it will cost you more, a better solution would be to sell the generator you have, and buy one of the 'silent' enclosed digital generators. I have a cheap 'Kipor' 3kw clone of one of the Honda models, and it is *much* quieter than my open-frame honda-powered generator of the same output power. Also the quality of the mains output from the digital one is excellent, a decent sinewave, unlike a traditional generator.
Alan.
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Unless I'm missing something how can the output from an alternator be anything else or less than a sine wave?..
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Tony Sayer




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