Pier decisions! Look what I found :-)

davewaldo · #1 05-08-2010, 02:56 PM

So I want to build a pier. I wasn't going to rush into this but I have the chance to borrow a dingo digger for free, so I can't pass that up. I wasn't looking forward to digging a mega hole by hand

So on Saturday I'll be digging a 800mm deep by 600mm square hole for the pier. I plan to make a steel pier so I can unbolt it and take it with me as I think we'll be moving house in a year or two.

At the moment I have a HEQ5 mount and GSO 8" RC, so I'm imaging at 1800mm focal length.

Well today I went to a builders demolition yard and found these two beasts.

Post A is 150mm square and has a nice top plate already.

Post B has a great base with gussets and all but is only 120mm square.

Both are 6mm wall thickness.

So which one should I get? Either one is under $150 so the price is right.

I'm leaning towards Post A. Its a bit cleaner so won't require as much prep to paint. And the extra width is great and should mean I won't need to upgrade for ages or ever. the nice plate up the top can be the top plate or I could flip it and use it as the base plate. Also with my current gear I don't think I need to worry about gussets. Or I could cut a section out of the middle and weld it back together to use both top and bottom plates.

At the moment both are WAY too tall, I plan to have my pier about 1.5m high to the top plate so I'll be cutting which ever one I get down.

So basically I'm hoping I can finish off one of these posts for a total cost of $250 or so (add top plates and bolts etc). Welding isn't a problem.

So do you think, am I on the right track?

Cheers,

David.

leon · #2 05-08-2010, 04:03 PM

Yep David, that is the sort of place i get all my steel, very cheap I might a but perfectly usable, nice pier material.

And I too would choose A, cane you imagine that filled wit cement, you would need a Mac Truck to pull it out

Leon

sheeny (Al) · #3 05-08-2010, 04:46 PM

I'd go pier A. Don't worry about the huge baseplate on pier B as it's too big and flexible IMHO.

Watch the price though. It sounds a bit expensive considering I bought all new steel, cut the size and lazer cut, to make both the pier and mount adapter plate for $200! If welding is no issue for you, then check out some prices before you jump into this lot.

Al.

davewaldo · #4 05-08-2010, 05:00 PM

Thanks Guys

Sheeny, I'll have a ring around to check the prices of the new stuff. Can most places that sell steel do the cutting? Such as round top plates etc?

sheeny (Al) · #5 05-08-2010, 05:38 PM

It probably depends on the supplier, Dave. The local supplier here in town is also an engineering company that does laser cutting

. All you can do is ask... if the answer isn't what you want, keep looking!

Al.

Tandum (Robin) · #6 05-08-2010, 10:34 PM

Dave, since using mine, I'd prefer to have a round top plate, especially when the tak is on top and the filter wheel is hanging down. The corners can get in the way and cut things short occasionally.

ZeroID (Brent) · #7 06-08-2010, 09:41 AM

'A'
Cut it to your required length and sell the rest to another wannabe pier builder. Or take it with you for the next house/dark site. You say welding is not a problem. I assume cutting it is also not a problem. Add your own pier top to suit.

davewaldo · #8 06-08-2010, 03:35 PM

Thankyou everyone, but I've since found that I can buy the steel new for only about $30 more. So I'm going to go the new route as this means I can make nice round top plates out of 16mm plate.

Now as for welding.... My brother-in-law has a Mig welder and he's very confident he can weld this for me. Is there anything I should be aware of for welding such thick material?

sheeny (Al) · #9 06-08-2010, 04:17 PM

Quote:

Originally Posted by davewaldo

Thankyou everyone, but I've since found that I can buy the steel new for only about $30 more. So I'm going to go the new route as this means I can make nice round top plates out of 16mm plate.

Now as for welding.... My brother-in-law has a Mig welder and he's very confident he can weld this for me. Is there anything I should be aware of for welding such thick material?

Nope.

Al.

davewaldo · #10 06-08-2010, 06:42 PM

Hows this for a design? I'm guessing I don't really need gussets for my smallish scope.

I can add them later if needed.

Bassnut (Fred) · #11 06-08-2010, 08:06 PM

Why so high?, is this for visual or photography?. The higher it is, the taller the OBS needs to be, especially if you want to close with the OTA in any position. For photography, the shorter the better, for OBs hight, access and stability (assuming you dont have restricted views).

sheeny (Al) · #12 06-08-2010, 08:56 PM

Fred's right.

My pier for my C8/CG5 was between 800 and 900mm high. Now that I have the EQ6 and C11 I'd like to take 150mm out of it but I can't bring myself to take then scope oiut of service to do it.

Al.

davewaldo · #13 06-08-2010, 09:18 PM

Thanks guys, I know you're right. The shorter the better for stability. But my back yard has a lot of medium height trees only 8-10m or so from the pier. So the more height I have I gain a fair bit more of usable sky. At this height I have a full horizion above 30 degrees altitude (approx). If I go 300mm lower it would be reduced to something like 45 degrees which gives me a lot less sky.

Plus I will be using it for visual obs. Also it will be set 200mm under the earth with grass up to the edge of the post. So really it will only be about 1300mm high plus plate. At my current property I have no room for an observatory.

This will be ok won't it?

My plan is when I move to a larger property I can build a proper observatory and use this pier but fill it with concrete to make it extra rigid.

Dave.