Pier requirements ?

[ScubaMike]

Hi Folks,

I realise there is a huge amount of information on the forum regarding pier building and considerations, but I have some specifics to put before the experts who have been through the process.

I have been given the go-ahead from SWMBO to build a pier in a specific location, but there are a number of considerations.

We have 3 young grandchildren. Any pier must be relatively safe, no sharp edges where they may hurt themselves.

SWMBO would like the pier to be unobtrusive, and not be an eyesore. Any suggestions?

The proposed pier location has approx 24" of clearance around it, (considerably more when viewing south & west) will this be sufficient? (I realise not ideal, but is it going to be enough?)

I have some 6" diameter drain piping, will this be large enough (c9.25 on a CGEM will be the largest load).

What height should the top of the pier be, allowing for the pier head? Main scope will be SCT.

How do I get the polar alignment? how close do the bolts from the concrete tube need to be to ensure I can subsequently get good alignment?

Sourcing materials. Where do people get the ironwork for the top of pier plate & the pier adaptor?

How feasable is it to leave the mount attached to the pier for extended periods (with OTA & weights removed). I have a TeleGizmo 365 cover and this will be the protection. Any further considerations I need to make bearing in mind the electronics in the mount?

Any advice and suggestions would be much appreciated.

[laser_jock99]

Lots of questions there but I'll tackle some of them!

1) A round pier would be safest for a child bang their head on- but either way a steel / concrete pillar is going to hurt if you run at it full tilt. Call it part of the learning process- they'll only do it once.... You could wrap the thing in a bit old green carpet underlay as padding and hope this makes the pier look less obtrusive at the same time?

2) 24" all round clearance will be very tight- you need more room I'd say.

3) A pier can be any height you make it. Work out where a comfortable eyepiece height is when looking near the zenith. My EQ6 tripod was always too short in this respect so I made my pier 1.8m tall. Now I can look up without kneeling down. For objects closer to the horizon I get the steps out (hence the need for clearance around the base)

4) Metalwork- my pier head adaptor was made by a local engineering firm to my own dwg (sketch) as it was too large and complex to make at home. You'll find that most small firms should only be too happy to help. You can buy materials easily enough on the web. I got my aluminuim angle for the tracks of e-bay for example. The pier head top needs to be designed so you can access the nut under your mount- this needs to be slightly slacked off for polar alignment and tightened up later. Many people have bolts sticking out of concrete. You don't need these to level top plate- they're mainly required for clearnce to access the mount nut.

4) I have known people leave covered mounts outside- it saves time re-aligning the polar axis. The chap I brought my EQ6 off had left it outside (covered) for weeks at a time with no lasting harm. Do remember that they are electrical devices though and need to be kept as dry as possible.

5) 6" dia pipe should be okay but in this respect bigger is always going to be better. If it's thin steel or plastic pipe then you'll need to be filling it with concrete. Thick steel tube is fine on it's own (assuming a sensible length of course!).

Good luck with the project- but do get some more room around it.

[Bizibilder]

I agree with the above but would add that I've seen a pier and mount design where the mount was protected using an upturned plastic dustbin, resting on a circular "shelf" around the pier itself. This would certainly keep the "sharp pointy bits" out of harms way!

The solid pier is really no more dangerous than any other post in the garden, or even the walls of the house - solid and they hurt if you run into them.

You certainly need more than a couple of feet clearance - my obsy is 6' 6" x 6' 6" and that is just big enough for me and my scope.

[Breakintheclouds]

How do I get the polar alignment? how close do the bolts from the concrete tube need to be to ensure I can subsequently get good alignment?

Close, but not madly so. Your mount will have some azimuth adjustability from the adjusters you normally use when polar aligning, but this only moves a small number of degrees either way. So you need to get your install pointing quite close to North, but just doing it with a compass during daylight should be fine. (Don't forget to allow for magnetic declination)

How feasable is it to leave the mount attached to the pier for extended periods (with OTA & weights removed). I have a TeleGizmo 365 cover and this will be the protection. Any further considerations I need to make bearing in mind the electronics in the mount?

I left mine out, with a cover, for quite some time. I'm not going to lie: a little moisture got in. But it didn't seem to have any real effect.

[malc-c]

As stated by the previous poster, a round pier with a round adapter will be safer for the kiddies. Most adapters are formed by using 2 sections of metak bolted together using three or four bolts or studs at equidistance. You should be able to get something made by a local fabricators. Here's my mount - 160mm OD plastic drain pipe, filled with concrete, reinforced with rebar rods, and fitted with an adapter machine dfrom 180mm stock ali profile. The pier cost around £30 including the concrete inside it (it's concreted into a 1m cubic block in the ground so that would add around a further £20 - £30 if using bagged pre-mix). The adapter cost £80 cash - plus £5 for all tthe studs and nuts etc

Clearance wise 2' is not enough. I would suggest 3 foot radius for a SCT otherwise observing will be cramped

[laser_jock99]

I took a different approach to the "protrunding bolts" pier head and had an aluminium puck machined to drop into the pier steel tube. Coarse azimuth adjustment is made by rotating the puck within the steel tube. Access to the mount nut (if needed) is via the 'owl holes' in the steel tube. I actually found you can achieve the fine azimuth adjustments by tapping the puck around within the tube!

[ScubaMike]

Thanks for all the suggestions.

I'd really be pushing it to get 3' clearance all round, but I'll push it as far as I can.

@Bizibilder - I have seen the upturned dustbin - Don't think SWMBO would go for that one - a little intrusive.

@Breakintheclouds - I would imagine that a little moisture wouldn't hurt - there is a huge amount of dew gets to these mounts anyway.

I'm wondering if I cpuld combine two of the designs I've seen here...

The one from Malc-c & the one from laser_jock99.

Have a steel pipe, with an owls hole, filled with concret to just below the owls hole.

Have a bolt sticking out of the concrete to just below the puck design shown in Laser_jocks pictures. This bolt is then located into a hole in a puck of Laser_jock design - used to reloacte the puck to the same orientation each time.

Much to think about..

@Malc-c - do you have a contact for the adapter (if you are able to let me have the contact I would be grateful - looks great btw).

Likewise, @Laser_jock, if you have details of where you had the puck machined, I'd be keeping all options open.

I'm trying not to jump in and to give this some thought before I start. I only want to have to do it once!.

Regards,

ScubaMike

[malc-c]

@Malc-c - do you have a contact for the adapter (if you are able to let me have the contact I would be grateful - looks great btw).

Regards,

ScubaMike

Sorry I don't have them... Any metal fabricators in your area should be able to make what you're looking for

[JamesF]

Is stainless the usual choice of material for the studding mounting the metalwork to the pier?

James

[malc-c]

Generally I beleive so, as it is less prone to rust or corrode

[Bizibilder]

BZP (Bright Zinc Plated) is much cheaper and will work as long as you protect any "raw" ends with passivator (I use Jenolite) and a touch of paint.

Actually I should also say its OK if you have a dry observatory! It may not be such a good idea if your pier is out in the open.

[JamesF]

Typically, Screwfix do a pack of 5 x 300mm lengths of 12mm stainless threaded rod which I think would be sufficient for my needs, but only do BZP in 1000mm lengths. I shall have to look elsewhere.

James

[ScubaMike]

Just passed drawings to a local fabricator.

Asled for bottom plate in 25mm steel (then power coated).

Top plate in 30mm, but galvanized (as it will be more prone to breaking the paint seal) then powder coated.

Price....

we'll see when he calls tomorrow

[JamesF]

How did you decide on the thickness for the two plates? And was there any specific reason for choosing steel over aluminium?

James

[laser_jock99]

How did you decide on the thickness for the two plates? And was there any specific reason for choosing steel over aluminium?

James

I choose aluminium as its a little easier to machine and won't rust. Also I like the black anodised finish! Although I did have to have 1mm of the black anodising machined off (see photo above) to make it fit in the steel tube. Measure twice, cut once and all that......

[ScubaMike]

How did you decide on the thickness for the two plates? And was there any specific reason for choosing steel over aluminium?

James

According to my measurements, I could have just got away with 25mm for the top plate, 30mm just gives a little more spare when tightening the mount bolt. I didn't want the bottom plate to look too different in terms of thickness.

Chose steel as it is much cheaper than aluminium. As it will be powder coated, I figured that rust should not be an issue, but if it starts to rust, I can always get another machined up in aluminium. Plus, just in case my measurements are a little off, best to take the cheaper option first.

Unsure how long the threaded rod should be, I'm thinking 150mm to allow for connecting top & bottom to leave about 100mm gap between the plates. Any comments on this gap? too much? not enough?

[Macavity]

Who knows? (Well, probably pukka Engineers!). For the moment, I've just bought a couple of (6mm thin!) "blackened steel" plates and an "Altair Astro" pier top to experiment with... my Skywatcher Pillar. I do occasionally wonder re. (the canonical) 12mm [only] screwed rod idea though...

I like to have a go myself. My tame, local, CNC machinists, do get a few laughs re. my "prototypes"? <G> But they're "good lads"! Now that they know me better, WE usually learn something? Though their delivery schedule is a bit like the old-fashioned shoe repairers: "He's just finishing it off now..." etc. etc.

Aside: Just contemplating 12mm hand drilling those bits of mild, blackened steel.

Will I escape without "major injury"? <G> I do take REASONABLE care, but...