Suggestions for noise reduction for my Sportsman 1000 4-stroke generator?!

bakaneko

Well-Known Member
Joined
Nov 16, 2015
Messages
1,319
Hey, the 420W charger is on its way from China (mid to end of May) but I am working on just tidying up wires, water proofing, etc. So, this generator is pretty silent like 55dB idle (no load) and like 65dB (charger load) but I still think some noise reduction can be done. I was thinking of lining the two side plastic panels with a sound dampening liner/insulation/styrofoam/???. Anyone got an idea what that might be? I work at a hardware store and they sell 1/4" insulation that I think is fire resistant but its like $35 for a bundle and I need like literally 5% of all of that. I think with even a thin liner I can reduce the sound by ~10dB. Of course, this needs to not dramatically heat up the engine and all vent ports will be opened. I love to have this thing almost impossible to hear unless you are within 20-30 feet of it.
 

Attachments



JerboaJohn

Well-Known Member
Joined
Jul 29, 2018
Messages
1,272
oh any polyethylene foam will deaden sound if it's about 4-5mm thick. the kind that comes in sheets they wrap things in, not the stiff thicker 7+mm sheet that lines boxes. too thick inhibits any air circulation n traps heat. tape or glue to 2 inside panels
untitled.jpg
 

bakaneko

Well-Known Member
Joined
Nov 16, 2015
Messages
1,319
oh any polyethylene foam will deaden sound if it's about 4-5mm thick. the kind that comes in sheets they wrap things in, not the stiff thicker 7+mm sheet that lines boxes. too thick inhibits any air circulation n traps heat. tape or glue to 2 inside panels
Hey, thanks for the tip. I can get that stuff easily for free. I might try two layers once I check inside for clearance and air flow. I really want to make it super stealth. It probably looks like a pannier from far away. Maybe, I should paint it like red/orange or a pannier color too. :sneaky:
 

CrazyDan

Well-Known Member
Joined
Jul 9, 2016
Messages
2,272
If you put it on the outside you can make it much thicker and possibly make it even more stealth by going a step further and gluing leather to the outside of that and make it look like it has a flap with leather tassels dangling from that. Of course cut all vents appropriately. Then make one for the right side that looks the same but is a real saddlebag that can carry stuff.
 
Last edited:

Steve Best

Well-Known Member
Joined
Sep 22, 2012
Messages
1,236
I ran into a similar problem while working with Ground Search and Rescue. We used these very loud old generators that made conversation difficult even 100' away. The answer was similar to what you are proposing. Things we experimented with in order of effectiveness:
  1. plywood sheet about twice the height and width of the generator seemed to redirect the sound
  2. Corplast sheet same size worked just as well and was lighter (for transport)
  3. A 3 sided box (2 sides facing work area and a top) was about twice as effective as a sheet
  4. Full box of plywood or corplast was very effective. Needed strategic venting on far side to rid overheating problems.
  5. The box was lined with 1" of regular open cell styrofoam (~$10 for 4x8 sheet) became super effective
  6. Rolled soft foam (type unknown) "snorkels" on the cooling air inlet @6" diameter brought worksite noise to almost nothing.
The box was light (corplast+styrofoam) but hard to transport due to volume. We eventually bought a very quiet Honda generator that was still noisier than the box but a complete simple unit.
87292
87294


Part of the secret of any foam to silence is to keep the outside rigid (free from vibration). I don't think the polyethylene foam is very good at this. The cheap construction grade white open cell styrofoam sucks up sound and pressure vibrations very well and is available cheap in 1/4"x4'x8' sheets. You can build up layers inside the box to closely fit your generator, leaving air channels aimed at the ground or sky. Use a non-solvent glue or the syrofoam will dissolve. Corplast (about $10 for 4'x4' sheet on the outside gives a strong, light. non-shredding, non-vibrating structure.

I really like the idea of a leather bag or something similar for camouflage. Shopping bags? Picnic basket?
Trash bag that smells of fish? Who would think of stealing that?
87295

Who would even want to look inside it?
 

Attachments

bakaneko

Well-Known Member
Joined
Nov 16, 2015
Messages
1,319
I ran into a similar problem while working with Ground Search and Rescue. We used these very loud old generators that made conversation difficult even 100' away. The answer was similar to what you are proposing. Things we experimented with in order of effectiveness:
  1. plywood sheet about twice the height and width of the generator seemed to redirect the sound
  2. Corplast sheet same size worked just as well and was lighter (for transport)
  3. A 3 sided box (2 sides facing work area and a top) was about twice as effective as a sheet
  4. Full box of plywood or corplast was very effective. Needed strategic venting on far side to rid overheating problems.
  5. The box was lined with 1" of regular open cell styrofoam (~$10 for 4x8 sheet) became super effective
  6. Rolled soft foam (type unknown) "snorkels" on the cooling air inlet @6" diameter brought worksite noise to almost nothing.
The box was light (corplast+styrofoam) but hard to transport due to volume. We eventually bought a very quiet Honda generator that was still noisier than the box but a complete simple unit.

Who would even want to look inside it?
Thanks for thorough answer, Steve. Yeah, it seems I can still do a lot. Even though, this is a relatively quiet 4-stroke generator; I am gonna do a thin inside polysterene or styrofoam liner and then an outside liner with faux leather covering on top. Whatever I can get my hands on for free at work. :sneaky:
 

darwin

Well-Known Member
Joined
May 26, 2008
Messages
3,279
Cardboard egg cartons if there's room. Some how the cone shapes work. Ever have a hearing test done and seen the wall linings? Also when we had wood floors put into our condo we installed 1/8in sound deadening material underneath it because of loud neighbors below us. That stuff works great. Bought it at Lowes, can't remember brand name but if you ask they'll know. It's condo certified to some standard if that helps. Wasn't too expensive.
 
Last edited:

bakaneko

Well-Known Member
Joined
Nov 16, 2015
Messages
1,319
I tried using felt its been real hard trying to get some of that polysterene so I got impatient. It seems the felt did about ~5 dB reduction when I checked my video format software. This is barely noticeable to the human ear. Also, this was done inside the garage so its louder than it is on the road due to echo. I guess I will try foam next which might be easier to get or another layer of felt on the outside. Also, maybe most of the noise is coming from the exhaust which at that point I cant do much about.

 

Steve Best

Well-Known Member
Joined
Sep 22, 2012
Messages
1,236
Hey bakaneko, I did some work on the China Girl engines in that respect. To quiet exhaust I needed:
  • a good tight flange seal
  • heavy wall pipe/muffler construction
  • long rubber hose connected to the stinger and
  • aimed down and back at 45 degrees at the rear of the bike
  • minor detail, a small round exhaust port (at the cylinder) had a softer note than a large square port
A long (16") silicone rubber hose of slightly larger than stinger diameter did not seem restrictive. 4 strokes run hotter than 2 strokes, so a pre-chamber may be needed to cool down the exhaust and will help quiet it further.

Once I got the exhaust noise quieted I started to hear the gear and intake noises. Quiet them and I started to hear the chains.
 
Top