[TowerTalk] Biggest, strongest rotor that fits a Rohn 45 rotor plate?

terry burge ki7m at comcast.net
Thu Feb 28 18:34:53 EST 2019


Jim and the gang,

Is it possible to use a side mounted rotor with a chain drive to give enough reduction to work turning some large beams? Seems like you have three problems...tork (sp), breaking and knowing the direction your beam(s) are pointed. Added to that is wiring/price of a Green Heron or some other controller. And of course just building something that will last and stand up to the weather like we are having now can be a challenge. Don't we just love our challenges?

Perhaps no wonder I've stuck with my Yaesu G-1000DXA's even though I don't think if the go out I can get them repaired or find parts cheap enough not to break the bank.

Terry
KI7M

> 
> 
> On 2/28/19 2:19 PM, john at 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.
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