|kb8vul wrote: *||Sun Jan 17, 2021 5:03 pm|
You need to be careful with doing this and if you are considering it, you need to be reasonable with the change. Those roots blowers were designed and balanced for a certain RPM range. A blower on a car / truck engine was designed to be run at a varying rate as the engine was sped up and slowed down as well. A blower for use with an electric motor was setup for a single operating RPM. I wouldn't go more than a 10 % overdrive due to this. SO the next question is WHY? Are you trying to make it louder or change the pitch?? More air is more sound. Pitch is the speed of the chopper. So not sure why you would want it louder for a hobby siren.
I don't have a thunderbolt so I can't test it, I'm just wondering if it works. I know a 4M (the common blower) produces 250CFM on it's stock pulley, the 5M (Very rare) 350 and the 6M 300.
If a 4m spun 10% faster it would move 10% more air and since 10% of 250 is 25 it would move 275 CFM in theory, not quite the 6M's 300 but pretty close.
Speaking of, If a 6M spun 10% faster it would move 10% more air, and since 10% of 300 is 30 that would be 330 CFM, not quite a 5M but still more air than stock.
Now I know what you're thinking and I already did the math.10 percent of 350 is 35, so 350+35= 385CFM. So if you wanted to build a killer Thunderbolt a 5M blower with 10% overdrive will throw out 385 CFM.
Compensating for the load (if the stock blower motor won't take it) would be a soft starter (dedicated soft starter or star delta for 3 phase sirens) or a bigger motor. Keep in mind if someone were to do this I'd keep an eye on amps and temps during the first run.
But as to why I posted this, I was wondering if anyone else had done It. I can't since I lack a thunderbolt and the funds to buy one and a space and power hookup for it.
But in theory would this improve performance? I know a 5m is a heavily desired blower and 6m's are pretty popular too. This is all on paper, I haven't factored in real world testing.
Does anyone know the pulley ratio for a thunderbolt's Various blowers?