Size of Support Studs for pillar mount

[pubquiz]

Hi All

I have bought a new mount and will have to raise it on the concrete pier as my ex mount was on a 12" pillar.

I will be making one of those 'platforms' you often see where 2 thick steel plates are joined by 4 large bolts/studding.

This will give me an adjust-ability in height and also for leveling

This will give me the height required ...not sure exactly how high I will need to make it till I get my dual mount and can measure things accurately...but will probably be between 10" and 12"

Is there a max height for a setup like this?

Will be having the plates made from some thick steel by a local engineering works and using hefty studding between them ...was in the engineers supply today and they had some 30mm studding in 1m lengths for £13....looked pretty hefty stuff

What I wanted to know was what sizes...ie thickness of plates, thickness of studding/bolts, and height between plates that folk are using.

Is there a minimum size of materials per the height between plates? I have seen some pics over the years where the bolts look quite thin and would cause flex but suppose they must have been ok.

I suppose the 'chunkier' the better but don't want to go too over the top due to cost etc.

Tom

[Pete Presland]

My plates are 5mm thick, and around 200mm square, with a gap of 50mm enough to tighten the mount to the top plate with an allen key. i used M10 thread for mine with large washers either side, very rigid !

[Steve Ward]

Bigger the better I'd say , seen too many using 10-12 mm and they never look good to me , 30 mm maybe over-egging it but I would use it myself I have to say ,

Eliminates the potential for flex instantly .

[Steve Ward]

Agree with that if you leave a minimal gap Pete , but to raise it to the 250-300mm height warrants something much beefier to eliminate the torsion potential.

[Bizibilder]

The longer the "studdung" the more prone to vibration it will be. Four at 12mm is fine for a gap of around 2" (50mm) but as the gap increases the studding need to get bigger (=more rigid) as well. 30mm is probably about right for the size of gap you are talking about. It would also be somewhat cheaper than having a "pier extension" either bought or made specially. The other option would be to use three or four lengths of something like scaffold pole as the spacers with "thin" studding up the middle each of them. Adjustment would then be limited to that available within the mount itself.

[cfpendock]

Just for interest, I had a similar problem trying to mount an eq mount onto a (very good) Celestron CPC (Alt/Az) tripod. I used three aluminium rods," did to give me a clearance of 4", which in practise was far bigger than i needed. Each rod is screwed into the top mounting plate which is 8" round bar, 2" long(!). It was not expensive - about £11. The set-up is unbelievably rigid.

[pubquiz]

Thanks for the replies.

Yes will definitely go as big as poss.

If it doesn't work I would extend the concrete pier with more concrete but that would be much more work.

Cfpendock...that certainly looks bomb proof!

Tom

[Sp@ce_d]

Well it can be a controversial subject.. making a nice solid Pier & then capping it off with 4 (or 3 even) bolts. However, that's exactly what I did & it seems to work fine. Could even have a disco.. ( age showing) in there whilst imaging

I used 12mm plate & M16 bolts

[pubquiz]

Yes Sp@ce_d That's exactly what I had in mind.

Are the plates alloy or steel?

Also is there any reason for the long length of the studs...have you had it higher?

What is the distance between the plates?

Sorry for all the questions....research

Tom

[Sp@ce_d]

Yes Sp@ce_d That's exactly what I had in mind.

Are the plates alloy or steel?

Also is there any reason for the long length of the studs...have you had it higher?

What is the distance between the plates?

Sorry for all the questions....research

Tom

Steel, sprayed to look like alloy.

Got them here about 18 months ago, excellent service, 24hr courier.. they're heavy.

http://www.ebay.co.uk/itm/Mild-Steel-Profile-Flame-Cut-Disc-Circle-250mm-Dia-x-10mm-thick-/290623949243?

Drilling them was fun, a good excuse to get a Drill Press.

I haven't adjusted them since setting it up about 18 months ago. I've checked tightness a couple of times but nothings moved, it's solid. I left a fair bit of adjustment in case I change the mount or fit different scopes. Plus it was hard enough cutting through 4 equal lengths with a hacksaw, I couldn't be bothered to shorten them again.. I guess it's about 6" between the plates but I'll measure it tomorrow.

[Sp@ce_d]

Ok it's a 4" gap. Those studs are 10".

Sent from my iPhone using Tapatalk

[teleskopjo]

One can do the leveling at the base instead to try and get tighter tolerances

like this 

But, would anyone have any idea if this can be done using these through bolts?

The idea being that you drill,

lay the pier base plate,

hammer the bolt in,

tighten the nut until its tightly secured (unleveled),

then undo the nut and

add washers under the baseplate to level it and

finally re-apply the nuts and apply say Loctite or use locknuts

My concern being whether the unscrewing of the nut would loosen the bolt as there is no longer any tension applied to it.

The advantage to this method being not having to manually cut stainless steel studding...not a nice task!!

[teleskopjo]

Interesting 

[lennylovit]

just use shims under each bolt , cut a U shape in the shim to fit around the bolt and slip them under your pier , I have lined and levelled many rolls to gearbox to motor in the steel works all to within a few thu ,  its standard practice in heavy industry doing it this way  

Lenny

[pubquiz]

Yes Interesting video from AE with usefull info.

I did make a 'ratbox' as he calls it for mine but did it from really hefty materials like 30mm bolts.

My pier is solid concrete poured into a large diameter plastic gas main pipe with a central I beam RSJ down the middle (10 years ago when I started making the obs I naively sunk a large I beam into 1 cubic metre of concrete thinking it would be solid.....it vibrated like a tuning fork!)

So I surrounded it with the tube and concrete and it is ABSOLUTELY solid

The 'ratbox' platform I made 18 months ago was to raise the height due to getting a new Mesu mount.

It has been a great success.....I havn't noticed any extra vibration so I think if you use enough bolts and hefty materials you CAN be ok with a 'ratbox' and it's wrong to totally dismiss them

Here is a link to the thread on SGL http://stargazerslounge.com/topic/192214-adjustable-pier-top-mount-ott/

Tom

[Carina Lass]

Oddly enough, the thickness of the plate is as important as the bolts as if the plate is too thin it bends due to the flexure of the system.

My ratbox plates are 15mm and so are the bolts.

I drilled them with a li-ion hand drill! Why use a drill press when honest toil will suffice?

The result is I can twiddle the focus without the x10 live view shifting ... at all

I have a pic of my guiding graph where I touched the camera to turn off the view screen. It jumped one arc second and corrected in two pulses.

Stiff is good, but all of it must be stiff or you're wasting your time.