Back yard pier

[axle01]

Made a pier for my telescope mounts, I made it so i can use 3 different mounts on it, a Skywatcher AZ-EQ6 a iOptron Pro Cube and a FTX Alt-Az mount.
Also made a PVC cap to cover it from the elements.
Got sick of setting up the tripod and having to level it etc. most times when i wanted to view or photograph something i found it was to much trouble so i would give it a miss, now i have no excuse.

Al

[brian nordstrom]

:thumbsup::thumbsup::thumbsup: to that ! , I job well done and I too could do with one of those .

Brian.

[Lee]

Looks great.... now just build a shed around it! :)

[miker]

Well done Alan! The difference between a pier and a tripod is amazing.
Were the discs and the slots plasma cut?

Michael

[Peter Ward]

Nice pier, but you really need scrap the three leveling bolts.

There is absolutely no requirement to level the mounts.

They will polar align perfectly without being level. The bolts simply reduce the the rigidity of your large diameter pier by around an order of magnitude....in engineering terms the weakest link applies, hence we have gone from bolting your EQ head(s) to a twig, instead of a tree trunk. ;)

[axle01]

Yes then some machining.

Al

[axle01]

Ok I wasn’t aware that the mount didn’t have to be level, I was taught to level the mount first.
The amount of work I put into making it I think it will stay but thanks for your input.

Al

[traveller]

Hi Alan,
Great to have a pier, as others said, makes the whole set up process a whole lot easier. I can get it going in 10-20 mins.
Anyway, if you want to do away with the rate cage as peter said, you can get a half pillar extension and do what I did. You may need more plate adapters for other mounts.
http://www.iceinspace.com.au/forum/showthread.php?t=136618
Cheers
Bo

[doppler]

I've got one of those "leveling" plates on my pier but its more so I can get my hand underneath to do up the mounting bolt. That's a lot easier than cutting a massive hole in the side of the pier. Those 3 bolts are a lot more stable than a tripod anyway so that's a big upgrade by it self. The only thing you might find is that the pier might "ring" when knocked, I filled mine with fine sand and it now has a dull thud.


Rick

[axle01]

Yeah that is one reason using 3 different mounts.
.
The pier has been galvanised so I won’t be doing that.
.
Might do that thanks.

Al

[Karlzburg]

Looks good Alan, I'd like to do that at home soon to make set up quicker.

[FlashDrive]

Looks Nice ....Good Job :thumbsup:

[Peter Ward]

For circular sections the moment of inertia is proportinal to the diameter to the 4th power. If my arithemetic is correct you have reduced the stiffness of the pier by about 6000x by using 10mm bolt(s) instead of the full diameter of the pier (150mm and say 4mm wall).....hence my comment.

I use a 10” steel pier with 1/2”walls. doesn’t move much ;)

[AndrewJ]

Bit of overkill for an EQ6.

Also, there are myriad threads on pier vibrations/stiffness.
Unless there is something to create vibrations, it is all moot.
If there are vibrations present, you probably need to do a proper analysis, as designing to suppress them is not as simple as add mass/stiffness.

Accidentally hitting a mount ( or wind on the OTA ) is the worst normal scenario, and in this case, the OTA and mount are normally far weaker than the pier, so you will lose the subs, no matter what.


Andrew

[peter_4059]

Here's a thread with the calculations in a spreadsheet. I think it also considers the levelling plate case

http://www.iceinspace.com.au/forum/showthread.php?t=166524&highlight=pier+design+spreadsheet

[axle01]

12mm SS bolts

Al

[Peter Ward]

Indeed, ideally you want low mass and high moment of inertia, so any perturbation will have a low amplitude (eg immune to small breeze) and decay quickly. That said even an EQ6 probably deserves better than a 8-10mm diameter bolt...the attached diagram from my old engineering text don’t lie.

[AndrewJ]

Gday Peter
The strength/stiffness/deflection calcs are only part of it.
Deflection is very rarely ever the controlling factor in a pier.
ie take an identical tuning fork design ( ie same moments of area etc )
Make one from tuning fork steel and one from bog std Mild steel.
Totally different end results :-)


And again i put it that if the knock/vibration is induced via the mount or OTA, then no amount of pier strength will save you.


Andrew


( also did Mech engineering incl vibration analysis )

[Peter Ward]

Not sure where you are going with this...but surely not to suggest 3x stainless steel bolts at the top is the best to preserve the stiffness of the lower section of Al’s beaut pier. :shrug:

Other than in the Hubble, small perturbations can and do go un-noticed in many a telescope...I’ve bumped my head occasionally on the 50kg of counterweights on my mount...and often exclaimed “gosh” or “golly” :). ....anyway, the post-concussion subexposure was fine.

[axle01]

Haha sure it wasn’t S*** or F***

Al

[Bart]

http://www.iceinspace.com.au/forum/attachment_browse.php?a=223455

Check out this remote observatory. I wonder how bad the images are from these as the mounts are a long way from the bolts so the wobble must be accentuated?

[AndrewJ]

Gday Peter

Of course it wont be as stiff as a solid pier, but the question is will it be stiff enough to do the job.
As long as he does his nuts up tight :-), i would suggest it is probably more than adequate for what is required.

Andrew

[Bart]

What I would do here is reduce the length of the adjusting bolts so they are as short as you can get them while still providing level. Your polar alignment will be easier if you are reasonably level. If you need to pull the centre bolt out you can undo the top nuts and pull the plate off.

[axle01]

Arrr yes but because I’m using 3 different mounts I need to get my hand between the two plates to do up and undo the center bolt.

Al

[AstralTraveller]

+1 :thumbsup: You should be able to keep the amount of visible thread down to 10-12mm. That will move far less than the stilts you have now.

[AstralTraveller]

I see. :D

[Peter Ward]

Very droll :)

Just because it works, does not mean the solution was optimal.

Also begs the question about the false need to level an EQ head.

Sure, if not level, you will get a little “crosstalk” in altitude/azimuth adjustments, but this is hardly fatal, perfect polar alignment is possible even if the EQ head is on lying its side.....but I’d suggest a degree or two of a lean is way better than reducing the rigidity of a massive mounting system down to that of a spindly (i.e weakest link) and unrequired component.

‘nuff said

[troypiggo]

The formulae are obviously correct, but they are only considering a circular section in isolation, not a group of 3 or 4 where they are some distance from the neutral axes. A single bolt will have fraction of the stiffness of a larger CHS section as you say, but a bolt group can have similar stiffness with sufficient spacing and/or diameter.

I do agree that pier heads don't need to be 100% level, although it does make polar alignment easier the more level they are, less iterative.
I do also agree that it seems a bit silly to put a "soft storey" if not needed when what we're after is minimising risk of deflections. However the calcs do show that stiffness can be maintained by carefully selection of bolt diameter and spacing.

[Peter Ward]

Did you really mean that: heads “don’t” need to be 100% level?

Lord knows I make enough typo’s (But I suspect there is a virus on my PC that randomly remaps the keyboard)

Assuming that this is the case, I guess we are agreed. :)

[troypiggo]

Oh yeah, I meant "don't". Off to bed for me... :)

[Kunama]

Nice pier Al, never mind the mathematicians, just remember not to hit the pier with a hammer while viewing or imaging ;)

Great idea to have it so you can use the three different mounts on the one pier. :thumbsup:

[axle01]

Yeah it’s all above my my pay scale.
Ok I must remember not to do that.
Thanks appreciated.

Al