Thunderbolt Horn Rotation

[Melvin Potts]

Most of the video clips I've seen of Thunderbolts in action show the horn turning clockwise.

However, I recall years ago seeing some of the former Nashville, TN Tbolts being tested; the horns on all of them turned counterclockwise.

Same for a couple I've observed in Cobb County, GA. The 2 I observed(been many years ago) were already there when I moved to Cobb in 1971.

Sometime after I moved back home to Nashville in '89 Cobb County bought the Tbolts which DeKalb County, GA had taken down. I'd seen a couple of these being tested when they were still in DeKalb(haven't seen them work in Cobb)..they also turned counterclockwise.

Just curious..did Federal make the Tbolt horns rotate one direction for a number of years, then change it? Or was it just a matter of chance with each individual siren?

[Jim_Ferer]

The ones I grew up seeing all went counterclockwise.

[JasonC]

For three phase sirens, it just depends on how the three wires were wired up to the rotator motor. Reversing any two wires would spin it the other way. Single phase T-bolts spin counterclockwise (at least the ones I've seen) just due to the fact of how they are wired internally. Per the T-bolt manual, "direction of siren rotation is unimportant".

[Robert Gift]

I am surprised they made the rotation motor three-phase.
Are three-phase motors not more expensive than single-phase motors?
Being gear-reduced, I assume it does not need to be very powerful.

[JasonC]

Are three-phase motors not more expensive than single-phase motors?

Quite the opposite. Three phase motors are much cheaper than single phase.

[Robert Gift]

Are three-phase motors not more expensive than single-phase motors?

Quite the opposite. Three phase motors are much cheaper than single phase.

Oh. Thanks, Jason.
Does this still apply to small three-phase motors?