On 2/28/19 2:19 PM, john@kk9a.com wrote:
What will K7NV do when there are no prop pitch motors? I wonder how he got
so many surplus motors? Yes you should be able to make a killer rotator with
parts from Grainger.
Indeed, that's where I was looking.. Grainger's selection of gearboxes
didn't seem to have "inline" multistage planetary with the 1000-2000:1
reduction you'd like to have.
Inexpensive variable speed drives make a 3 phase AC induction motor nice
to use - they're cheap, common, and rugged. You DO have to run 3 wires
up to the motor or put the VFD up on the tower.. I don't know about that
from a servicing standpoint.
I suspect you could easily interface something like a Green Heron to a
VFD - most of them will take an analog speed input, for instance.
For very skinny fit situations - Franklin Electric does make skinny 3
phase motors (for use in well pumps) - less than 4" OD as I recall. But
if a standard 56C case will fit that would be the way to go.
I guess, you probably wouldn't want a 1/2 HP drive in Rohn 25 for
structural reasons (you'd twist the tower?)
Telrex had an A/C motor and a separate gear box
connected with a chain. Mine held up much better than the many Hy-Gain
rotators that I owned. I thought about building a rotator similar to the
Telrex with a more modern control box but in the end I went with using prop
pitch rotators. They have an impressive gearbox which seems perfect for
antenna rotating and also holding in position, in comparison most ham
rotators are just toys.
An impressive gear box that would cost $10s of K to duplicate today.
And, they were volume and mass constrained - a tower application isn't
as mass constrained. Cast iron is a cheaper housing material than aluminum.
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|