WIP Pier Design

[Digz]

Ok, some of you may know that I have been working on a hypothetical obsy design. At present the missus and I do not own our own home so there is no scope (excuse the pun ) to build an obsy yet.

This hasn't stopped me from developing a generic design in preparation for when we buy our own place, which I shall share once finished. To go along with that I have also designed my own pier.

This is very much work in progress and I welcome any advice and feedback from others who have been there, done that and got the T-shirt!

In preparation for the design I trawled this forum together with a few others and google. I came across this article from another forum which made a good basis for the design.

Pier Design Fundamentals - How To

It puts across some good theory, in a language I can understand! However, when using the figures listed I ended up with a massive pier, far larger than the ones that I have seen around here and for sale commercially.

So after some more research I finally decided to reduce the figures slightly and came up with this initial design, as attached.

It is based on a direct connection pier where the pier adapter for the mount is bolted directly to the pier.

Upon my research I noted three key points to a good pier design:

1. The ability to level the top of the pier;

2. The ability to fine tune the pier adapter to point North;

3. The ability to attach the mount to the pier / adapter using the threaded bolts from below.

Point 1

Levelling the pier still needs some resolution but ultimately will also boil down to ensuring the top of the pier base is level and that the threaded rods for connection are vertical and plumb. With this is mind Im sure I can fine tune the levelling of the pier with some sort of shim or gasket.

Point 2

In the designs I have noted the pier usually has a secondary pier plate to which pier adapter affixes to. The connection between these two items often contain slotted holes so that the pier adapter can be fine tuned to face North (Also, being connected with protruding threaded rods, also gives the ability to get the plate level.). In removing this set up on my design I needed to figure a way to achieve such fine tuning.

Now with my mount (NEQ6 Pro) as well as most EQ mounts there is a small amount of adjustment with the azimuth adjustment bolt. I have decided to add further adjustment by transferring the slotted holes to the base of the pier where it is connected to the pier base.

Point 3

In order to allow access to the underside of the top plate a slot is cut out of the pillar. This allows access to the 6no holes for attaching the pier adapter and central hole for attaching the mount. The 6no pier adapter holes are either spaced for a generic pier adapter or custom spaced for a custom made pier adapter.

So, thats enough waffling from me. I hope someone find this useful and, as mentioned above, I would be grateful for any feedback anyone cares to offer.

Direct Connection Pier.pdf

[Trull]

Your design looks good!

Can I offer up a couple of suggestions:

If you are going to weld the gussets on, nibble out the corner nearest the included corner. This will avoid arc blow - where its hard to get the arc controlled nicely (so you get a poor quality weld).

Also you may find that using box section is cheaper to weld - even better use I section and that leaves you with two easily accessible channels for cable runs.

Have you considered surface preservation? most shops will blast to SA 2-1/2, and then apply zinc oxide primer and a two pack epoxy for a long lasting coat.

Have fun!

[Digz]

Hey Trull, thanks for stopping buy and offering some advice.

I understand what you are saying with regards to arc blow etc but Im not too sure if I understand where I should be nibbling out? Any chance of a sketch or something to make it clearer for me?

I havent thought of using box section or an I beam, thats certainly given me food for thought. Also re surface preservation I think I would ultimately get it coated within something, but not quite sure what yet...

[Trull]

If you nibble out a hole at the 90degree or right angle of the gusset, make it a neat looking radius of say 30mm to avoid the chance of cracking. The problems of welding into a tight corner like that are: your heat affected zone will overlap (bad), can create a crack, which will then obviate the strain capabilities of the gusset. Also, trying to get a good steady arc in the twisted magnetic fields in a corner like that is dicey.

Have you calculated the bending of the plate under your projected loads? You may find that you can avoid using gussets if you size the central member nicely, also you are on 12mm plate - that's pretty chunky and won't bend much. It all depends on what the costs are, and what you can get your hands on.

Hope this helps

[Digz]

Hi Trull,

Sorry, got my thick head on tonight. I think I get what your saying. Ive attached a sketch of what I think you are saying - basically taking the corner out of the gusset plate? I might have to re-read it tomorrow with a clear head, lol.

With regards to calculating the bending of the plate, I have not done this, nor would know where to start tbh. Having said that, most of the sites I found when gathering information seemed to favour 12mm plate so I reckon you might be right insofar as not needing the gussets at all which should make the welding easier

I suppose the next step, for me, is to find a local welder / machinist / ironworks to get this costed.

Gusset Cut.pdf

[Gina]

I'm afraid I can't see any advantage of the gussets. The pier adapter is attached to the centre portion of the plate and there will be no stress outside the circle where the pipe is attached. Assuming a good solid weld where the pipe is welded to the plate, that will take all the stress and movement at that interface should be negligible.

[Trull]

Gina is right enough - and you might also bear in mind that tightening the top studs to the telescope mount is harder when you have to get a spanner inside the central column.

For the bottom, without doing some calcs, its impossible to say how much benefit you will have without knowing how heavy your optical kit is... so what have you got in mind to mount on this pillar? Is it to go in an obsy?

[Gina]

The critical point is the bottom of the pier - the bending moment is greatest there and the reason most piers have long gussets (fins) at the bottom of the pier. I can also see a snag with the access to the mount fittings - not only is it awkward to get at but there would be a serious risk of dropping the mount fixing bolt down the column.

[martin_h]

I can also see a snag with the access to the mount fittings - not only is it awkward to get at but there would be a serious risk of dropping the mount fixing bolt down the column.

Not if you fill the pier with sand!

[Digz]

Hi Guys, thanks for the comments.

Gina - you raise a valid point with respect to the gussets at the top of the pier. I think I shall remove these.

Trull - the most I would have on the pier would be as follows:

1. NEQ6 Mount

2. 250p DS Reflector

3. Nikon D200 DSLR

4. Atik Titan

5. Finderscope = Finder Guider

6. 3 x Counterweights (5kg each)

I think I may extend the gussets to the bottom, I may also see if I can incorporate a kind of safety mesh across the bottom of the opening to catch any stray bits that fall off. Alternatively I could design some sort of second plate that sits ontop of the top plate that the pier adapter fixes onto and have the top plate machined with a hole cut out of the centre big enough to allow the pier adapter fixings to fit through thus allowing the two plates to be fixed together flush.

Martin - Filling with sand sounds like a good idea, I would imagine it would make the dampening of vibrations a lot quicker as well?

[martin_h]

Some people fill it with a sand and engine oil mix.

[Digz]

Some people fill it with a sand and engine oil mix.

Great tip, thanks

[Doc]

Some people fill it with a sand and engine oil mix.

Used engine oil

[Trull]

Go easy on the used engine oil, its carcinogenic - and if it should leak into the ground you can cause pretty nasty pollution.

Filling with sand alone is more than sufficient IMHO - and I filled my speaker stands with dry sand to help the sound. No oil required.

[martin_h]

You only need enough oil to bind the sand together! but yes just dry sand will do...play sand would be best...dry

[George]

You only need enough oil to bind the sand together! but yes just dry sand will do...play sand would be best...dry

That kiln dried sand they sell for brushing into block paving gaps is reall good, its extreamly fine and very easy to fill a pier via a funnel.