On 9/6/2011 8:04 PM, john@kk9a.com wrote:
I have seen the gearbox, or at least the ones for the older ProSistel
rotators of various sizes available direct from manufacturers.
Stateside there should be dual worm gearboxes available in the proper
sizes. Most like they would even have adapters for motors.
> I have an old Telrex rotator in storage that uses a 1/3 hp motor connected
> to a gearbox with a chain. It doesn't look like it would be difficult or
> expensive to duplicate with standard parts from Grainger.
*Most* of these systems use off the shelf parts, although there may be
an adapter or two required.
> It is large and
> most towers would require some modification to fit it inside.
I think you can get up to the PST-71 into a 45G without having to cut a cross
brace. I know the PST-61 will fit although you have to turn the motor 90
degrees. That is a whole lot easier since they started packing the gear box
with grease instead of filling it with 90 weight gear lube.
> One could
> also install a sprocket on the mast and use a chain connected to a gearbox
> outside the tower. I know some of the EME guys make their own rotators and
> so did K4JA, but it's really not that common.
If you are willing to take the time to find the proper parts it's not
all that difficult. However finding the right size gearbox with the
correct ratio that will fit and a motor (that will fit the gearbox and
tower) can be time consuming.
However any one with a few tools and a bit of mechanical ingenuity
should be able to build a rotator the equal of anything on the market.
Fitting a pot for a direction indicator is usually simple. It takes a
bit more to add a pulse driven system, but not much. You can pull the
pulse unit off old C-band dish positioners, but the parts themselves are
relatively inexpensive, or were 10 years ago.
> BTW, Prop pitch motors cost thousands of dollars 60 years ago.
New, Yes, but not at the surplus shops. My comment about them being
available for between $10 and $20 was in the early 1960's and they had
piles of them from new to well used. If you wanted one it was "there's
the pile, go dig one out".
73
Roger (K8RI)
> John KK9A
>
>
>
> To: Towertalk
> Subject: Re: [TowerTalk] Heavy Duty Rotor
> From: Jim Lux<jimlux@earthlink.net>
> Date: Tue, 06 Sep 2011 14:59:47 -0700
>
> On 9/6/11 2:08 PM, David Jordan wrote:
>> PPM's are great if you have $4,000 for one...
>>
> Exactly... seems you could find an off the shelf collection of parts
> that get you there, perhaps with a bit of bracket fabrication (mind you,
> where I used to work, the words "all you gotta do is fabricate..." were
> guaranteed to result in giggles if not outright guffaws)
>
> But these days, $300 gets you a brand new 2HP TEFC motor, another couple
> hundred gets you a variable speed drive for it. The gearbox is going to
> be a bit tricky, because you need several stages if you're doing
> standard planetary gears to get down to the 1 RPM sort of speed you want
> from 1750. But even so, I don't see it being more than $1000-1500 all told.
>
> I suppose the market is SO tiny that it's not worth it for someone to do
> anything more than a custom one-off. The existing products from M2 or
> AlfaSpid or whoever are sufficient for 99%, and for the 1%, you're going
> to be cobbling up something custom anyway.
>
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