Wood pier..which wood?

[MattT]

Now my 2" Pillow Block EQ head is getting closer to finishing I'm wanting to install a wooden pier to mount it on.

Why wood? ...I like the stuff, its easy to work with and with the right finishes will have the Victoriana look I'm after, mouldings etc.

Height above ground to base plate is 1600mm. Tall enough to view at Zenith sitting. 800mm deep hole with concrete all around.

What wood is best so it doesn't warp? Merbu is expensive, Red Gum less so and Cyprus pine is cheap. I'm thinking 4, 100x100 2400mm long posts bolted together, treated with a marine product to stop rot (if needed, possibly not for Cyprus) and decking oil on the parts above ground.

Is a tall pier like this likely to have vibration issues?

Any other things I have missed? Is a pier built from concrete blocks another solution?

This is for visual only if that makes any difference. Scopes on top weigh around 20kg's .

TIA

Matt

[Kunama]

Personally I would take a trip to the nearest Works Depot with a carton of beer and ask for the top section of a damaged galvanized steel streetlight pole.......

My brother-in-law just scored a 4m section locally doing just that.

If you get lucky you might score the lower section with the steel flange welded on...

[AndrewJ]

Gday Matt

I was going to suggest something similar, but use an old wooden power pole.
Down here, most poles are wood and very rot resistant.
Just get an auger to bore a hole about 1.5m deep and slot it in.
If you can find someone with a big enough lathe, you could get it turned to look like an old victorian pillar first.

Andrew

[jjz (Joe)]

If using wood I would suggest you make it out of laminated wood instead of a single board. It will resist movement a lot better, all wood moves.

If you want something other than generic pine or Tas Oak/Hardwood try giving someone like http://mathewstimber.com.au/ a call and see what they recommend. Find out if they also have a milling service to help make the laminating work easier.

If you need any help shoot me a PM I might be able to help with the glue up etc...

JJZ

[jenchris (Jennifer)]

I would also suggest marine ply - dimensionally stable and rot proof

[Tinderboxsky (Steve)]

Most marine ply is not rot proof. The key to marine ply is the glue used to bond the laminates. It is specifically formulated to retain its bond and structural integrity in adverse water and marine environments. The wood laminates will degrade over time with exposure to the elements if not properly sealed. Having said that, it is possible now to purchase treated marine ply that will resist rotting for an extended period. One would need to specifically ask for this.

It would seem to me that Matt's original suggestion of bolting four sections together would provide sufficient structural integrity. As to any vibration, it is difficult to bring any experience to the discussion. I have 1.5 metre round wooden fence posts set in concrete on our property that appear to be very resistant to vibration. Perhaps the success of wooden tripod legs is also an indication that Matt' pier proposal would be OK for visual observing.

Cheers

Steve

[jenchris (Jennifer)]

Bruynzeel is guaranteed for 25 years

[astro_nutt]

How about a steel/concrete tube and cover it with oak veneer?

[speach (Simon)]

I tried a wooden post 300mmx300mm Cyprus. wouldn't recommend it very prone to vibration, even walking on the ground around.

[MattT]

Thanks for the thoughts so far. Maybe a pier this high out of wood is not such a good idea after all As I have the tripod I may as well give that a good try out with the mount and scopes when the EQ head is finished. I'm not that keen on a concrete pier at the moment.

Matt

[Wavytone]

Many years ago I had an AOS Goliath mount with 8" f/7 Newtonian on it, big heavy beastie. The steel tripod under the mount was the weakest (flimsiest) part and I ditched that and made a very successful tripod out of Karri floorboards - think Jarrah or redgum.

Each leg was two boards edge to edge at a 60 degree angle (I had planed the edges to fit) - glued with epoxy and screwed with marine (monel bronze) screws, and assembled so that the complete tripod resembled the edges of a tetrahedron.

It turned out utterly, utterly rigid and lighter than the steel tripod, and it had the advantage of damping vibration much better than the steel one which twanged like a spring.

I wouldn't use softwood, and I wouldn't use Tassie Oak (victorian ash) as while strong that is also very springy.