Nigel I will have to check. I normally only use the 21". I know most think the bigger the better but I find even with 8gpm I walk slower with the bigger surface cleaner. I do know that you can only get 300 cfm through that long of 2" Vac Hose. So you know the silencer can be mounted under the trailer. I would say its 30% quieter with the longer silencer.
Thanks Tom D.
I hear what you are saying with the forward walk rate and the bigger surface cleaner.
But I wonder what the numbers look like,
Lets say 5.5 @3500 to the 21" and 8 @3500 to the 30"
The 30" is 1.42 times bigger than the 21"
Interesting that the arc distance length between nozzles on both SC's are almost the same 30" = 31.4" and 21" = 32.97"
The potential impact force to the 30" is 473.28
The potential impact force to the 21" is 325.38
Although the 30" has an extra arm (an app. additional 23" of pipe or 2.14 times the amount of pipe) you should calculate the amount of force distributed per inch of arm length that should give you a good starting point of possible rpm differences :....
21" has ~21" of pipe with 325.38 potential force behind it thus 325.38/21 = 15.49 force per inch
30" has ~45" of pipe with 473.28 potential force behind it thus 473.28/45 = 10.51 force per inch
I really dont think the 30" spins much slower than the 21" and have found that the overall time to completed the same sq.ft with the 30" @ 8gpm 3500psi was faster, but you have to give the surface cleaner the
full true input.
Most run 8 gpm at 3000 psi and have great pressure losses with extreme lengths of smaller hose, that is the big handicap of the 30" SC user.
Tom D do you have a stroboscope at the shop, maybe you can measure different spinner rpms for us, that will be great.
oke: 