Pier Construction - Are we all doing it wrong?

[Chris]

I wonder if the weak point in most peoples' pier & GEM setups isn't actually the alt pivot and adjustment mechanism?

James

Good point, if your going to have a pier engineered to this extent to limit vibrations, surely you need to have the rest of the system equally engineered to justify it? We could take it beyond the pier and mount e.g. the dovetail, the dovetail that comes with the 200p wouldn't warrant going this far with a pier in my opinion, and I've seen amazing results with the 200p!

[pete_l]

The content of those videos all sounds very rational, in the same way that people say you must have this-or-that for a top-notch hifi system. However, the whole approach lacks rigour as there are no measurements or numbers (or even consensus on what attributes are important and what values are acceptable for them).

I'm willing to be convinced, but I'd want to see those statements put to the test and objectively measured. The one thing I do agree with is that polyester resin is a fine material for fixing threaded bolts into concrete!

[JamesF]

The content of those videos all sounds very rational, in the same way that people say you must have this-or-that for a top-notch hifi system. However, the whole approach lacks rigour as there are no measurements or numbers (or even consensus on what attributes are important and what values are acceptable for them).

Exactly so. It sounds very much like the "Sound rational, say nothing specific" patter common to many salesdroids. I actually felt my skin crawl when he referred to the "torquage" on the fixing bolts.

James

[solarboy]

sorry about the odd missing word i'm dylexic so i have to read most of the stuff at leased 10 times and now have i'v noticed the odd missing word unlike the old SGL i can't see a button to edit stuff so it will have stay as is

apologies

solarboy

[yeti monster]

I actually felt my skin crawl when he referred to the "torquage" on the fixing bolts.

Yes, he let himself down there, also referring to kilogrammes as a torque value, I seem to recall, tsk tsk....

[JamesF]

Yes, he let himself down there, also referring to kilogrammes as a torque value, I seem to recall, tsk tsk....

I noticed that, too. Somehow I don't think I'd be wanting him to bolt up anything critical for me

James

[Zakalwe]

Thats why I called snake-oil on the videos. He is peppering the conversation with "pseudo-scientific" words that sound impressive (but only to someone that doesn't know what they are talking about), but which are either used in the wrong context or are just plain incorrect. If he knew what he was talking about, then he would not do this.

[swamp thing]

:D Does he not realise he is contradicting himself. What a turkey.

[Islander]

There's also the 1 cubic metre of concrete/1 tonne statement. Assuming a C20 mix (1:2:4) it's more like 2.4 tonnes not including rebar. The videos are full of sales BS.

[JamesF]

There's also the 1 cubic metre of concrete/1 tonne statement. Assuming a C20 mix (1:2:4) it's more like 2.4 tonnes not including rebar. The videos are full of sales BS.

I did at that point think "there's a man who has never tried to shift a cubic metre of concrete by hand"

James

[RogerTheDodger]

I'm still more than happy with my brick pier, this is just a load of scare mongering.

[solarboy]

nothing wrong with a rat box i'v built a few for folk over the years

solarboy

[Davey-T]

I wonder if the weak point in most peoples' pier & GEM setups isn't actually the alt pivot and adjustment mechanism?

James

I think the weak point on my setup is the "nut" holding the scope

Davey-T

[Jessun]

Interesting thread. I suppose to start with it depends on where you are on the globe, i.e. how deep and big do you need to did to reach frost free depth in the ground. For Sweden - my home country - a cubic metre sounds like a bare minimum if you want an otherwise unsupported structure solid and immovable throughout the seasons.

He talkes about pre stressed weld joints, but isn't that true that weld joints shrink and stress whatever parts you weld together? I have little experience in welding but whenever I put two pieces together they will try to alter shape slightly as the weld cools and shrinks, sometimes despite initial tack welding.

As to the 'rat box' - OK, may not ruin things but why spend the cash and effort when it achieves essentially nothing? Why not spend that time etc on making the pier straight in the first place?

And I'm still puzzled by the ammount of metal, concrete etc that goes into making piers when the pier adapter is sometimes held in place by 4 tiny hex M4 bolts, and the saddle has perhaps only one M6 to connect to a Losmandy rail fitted by again 4 M5 bolts to the actual scope? What part is actually going to be the first to move as gravity and thermal effects kicks in? Not the 4 M12 rat box bolts...

This is the mechanical equivalent to the f-ratio ghost, and needs sorting. Not by me - I'm here to learn.

[Jessun]

I think the weak point on my setup is the "nut" holding the scope

Just saw this too late Dave!

[Chris]

Jessun- I want to here more about this f-ratio ghost???

[Jessun]

Haha, another day, another thread. Basically it's another common area of lots of discussion and mixed opinions on its absolute properties. It's the rat box of optics

[solarboy]

hi dave get a bigger nut