# How do you make an ultra-quiet muffler for a lawnmower?



## Rubber Duck

I've decided to re-purpose my old Murray mower, ... again.

Mower deck was made of pop-can metal & I got sick of straightening it & welding reinforcements on it every time I bumped up a slightly thicker blade of grass than usual, ... 

So I took it off & tied the deck lift/lower lever to the foot clutch to convert it to hand-operation for a paralyzed girl I know so she could drive a motorized vehicle for the first time in her life. The first thing she did was crash it into the back of my F-150 and then she was too scared to try it again.

So now I'm thinking about using that vacant blade pulley to spin a car alternator so it has a real electrical system instead of just a lighting coil. This will be a truly unique application. I plan to use it for lights to gather firewood at night, a tow vehicle for towing the raft trailer down to the river where I can't (legally) take my pickup. And for recharging the raft's deep cycle batteries in mid-trip when we're on our party island so in the morning I have full batteries for the 2 mile upstream return.

The mower is just big enough to tow the raft trailer, yet small and light enough I can load it onto the raft myself when it's just me & the girlfriend. 

But it'll have to be quiet. I don't want it's noise to be heard over the stereo. (200 watt Kenwood pushing four car speakers in a plywood box, ventilated by a 12 volt computer case fan)

I've got two ideas. Either make a big clumsy, awkward glass-pack for it, or just park it near the water's edge & run a flex-pipe into the water & weight it down with a brick. I think I'm leaning towards the glass-pack.

Any ideas? 

I ruled out running a pipe down the length of the mower & out the rear unless I can wrap it because I don't want the heat around the drive belt.


----------



## Travis in Louisiana

AT first I was thinking of making a muffler like a GUN SILENCER. Then maybe like a LONG pipe wound into a coil. It would be a big coil. Just thinking here.


----------



## Harry Chickpea

You might find that once you quiet the exhaust the engine itself will be too noisy.


----------



## Rubber Duck

Travis in Louisiana said:


> AT first I was thinking of making a muffler like a GUN SILENCER. Then maybe like a LONG pipe wound into a coil. It would be a big coil. Just thinking here.


In Switzerland, small single engine aircraft are required to have mufflers. I've read about their low restriction, super quiet mufflers before but they're really long. Way too long for a little mower.



Harry Chickpea said:


> You might find that once you quiet the exhaust the engine itself will be too noisy.


Yes it will actually. Especially since the engine is bolted directly to the stamped sheet metal pan frame. It won't be that bad though. I once made a minibike (3.5 HP Briggs) sound just like my Honda CB100 except the centrifugal clutch & chain still made noise. I noticed an immediate reduction in the calls to the cops the neighborhood's meddling seniors would make. They were less likely to notice me going past their house on the street.


What I did on that minibike was simply weld a 10 inch long piece of 1/2" electrical conduit to the end of the "sausage" type muffler. That was it. But I tried the same thing on this 12.5 HP engine, using 1" tubing which is the same size as the outlet hole on it's muffler, but it didn't make a difference at all. And now I've got this goofy looking tube sticking off to the side.


----------

