How to choose an actuator for (an undocumented) polar mount?

[Channel Hopper]

Why would they? Not much point. What mounts out there require 24" let alone 36"? My 18" actuator is sufficient to get from 57E to well past 61W.

A modified polarmount for the 1.5m design here, modified for full movement to the East, requires no less than 34 inches (ooer !) of shaft travel.

 

[Channel Hopper]

Both are Jaegar SuperJack.

Apologies, you use Jaegar products, I was talking about Jaeger

 

[Huevos]

A modified polarmount for the 1.5m design here, modified for full movement to the East, requires no less than 34 inches (ooer !) of shaft travel.

Love to see that. What is full movement? How much arc? The actuator must be at the rim of the dish. Have you got a picture?

Anyway true H2H (+/- 78º, 170º of polar axis) is way beyond the scope of a linear actuator. And just scaling the actuator and polar mount up doesn't change that fact. So what's the point? The way I see it it is just over engineering.

 

[Channel Hopper]

There are a couple of pictures somewhere on the site.

The actuator has to cope with a 1.8m dish on the old style IRTE polarmount, and being on the roof has to work with additional wind loads.

 

[hexah]

I don't know why people want the expensive 'super' jacks.

I used one of the ordinary jacks on a very heavy dish of just over 2m in a wind exposed area for years without problems. st1 is in a sheltered area so is not going to have any problems with any jack.

It even had a cups worth of rusty water in it when I opened it up. It was still working.

From a manufacturing point of view, screw and hydraulic actuators go back to victorian era machines and have been scaled up to lift massive platforms and flood defences. Just moving a dish round an arc is easy. An actuator that moves a dish has much more power in reserve than it needs to move a dish.

 

[Huevos]

I don't know why people want the expensive 'super' jacks.

Most important thing is you don't want lash in the actuator, otherwise positions are not repeatable.

 

[hexah]

The wind would happily 'lash' the actuator.

Sometimes you could hear it being lashed all night and day.

There was no (backlash) problem with repeatably and satellites were much weaker in the olden days, often much less powerful than footprints suggested.

Some footprint maps went beyond theoretical coverage to blatantly taking the p.

 

[Channel Hopper]

Hmm, they've vanished

http://www.satellites.co.uk/forums/threads/72-east.2233/#post-9704

 

[Captain Jack]

Would love to see those pictures, CH... Panamsat.. hah, there's a name I haven't heard in a long while!

 

[hexah]

This was more an exercise with the angle grinder and to see how far I could push the dish (and the wife) before something broke. Both are intact - along with my head.

Nothings changed since then.

 

[Channel Hopper]

Why would they? Not much point. What mounts out there require 24" let alone 36"?

Professional ones

 

[archive10]

Professional ones

Good pics. But what's with the fishing net? Keeping birds away?

 

[hexah]

Actuators were available in huge sizes in the olden days for big dishes, 48" and 60" heavy duty and iirc bigger but I doubt there is the same demand for them now.

I wish I kept more of the manufacturers marketing and data sheets.

Good pics. But what's with the fishing net? Keeping birds away?

Nets are everywhere in London to keep the damn pigeons and their poop away.

And to stop those annoyingly loud parakeets from perching and giving everyone a headache.

The nets are usually black or grey unlike this one.

 

[hexah]

That is a truly international dish.

It has a drainage hole for equatorial use.

 

[Huevos]

Professional ones

What size is that dish? Declination adjustment looks hard work. When you loosen the adjuster does it fall forwards?

 

[hexah]

Its not just the size of the dish, its the wind factor.

A m8 of mine has a company in another part of the world specializing in communications over a wide spectrum of frequencies including terrestrial microwave.

They used to be relaxed about working on flat roofs on tall buildings but they learnt their lesson on a lattice on top of a tall building. It was totally calm at street level. It wasn't too bad at roof level but a bit higher and

Wind at heights can be phenomenal.

Its all health and safety first these days!

 

[gibertini]

I don't know why people want the expensive 'super' jacks.

cos usually expensive means quality.... i guess if a cheaper version does its job well and lasts then its all good. as for the german sat shop my m8 ordered 2 18inch ones and got the proper version and not the superpowerjack. does that american company not still make quality actuator,s? cant remember the name

 

[hexah]

My view is that in terms of power output in N (Newtons) they are the same.

What matters is waterproofing whatever you get well using self amalgamating tape over the seals and a motorcycle shock gaiter (recommended by Channel Hopper) over the exposed parts and the gasket as you can't get the special actuator boots anymore.

Remember mine worked even with rusty water inside. Make sure the electrical connections are away from any potential water running down the bottom of the jack. Maybe spray them with white lithium grease or daub from a tube of servisol silicone grease if you have it. The servisol silicone grease would last longer.

 

[Channel Hopper]

What size is that dish? Declination adjustment looks hard work. When you loosen the adjuster does it fall forwards?

Never tried to move it since I installed it in 2001/2. The IRTE polarmount works well and again is only adjusted once in its life.

The 1.8m bolted on the front is similarly fit and forget. What is continuous maintenance are the feed bolts, and spider removal, once or twice a year with a piece of spaghetti.