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Doug Culbertson
Pooh-Bah
Reged: 01/06/05
Posts: 1353
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Maybe this would have been better posted in the Observatories forum, but I have been wondering about this since reading a couple of wood tripod threads, and planning ahead for my own observatory.
Since it seems to be widely accepted that wood tripods display better vibration damping characteristics than metal tripods, how come you never hear of anyone using a wood pier for thier mounts? I would think that a good thick wood pole, perhaps a length of telephone pole, sunk deep enough into concrete would make for a pretty decent pier that would be free of vibrations. So, what am I missing? Other than the threat of termites, perhaps? 
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Doug
Midway, FL
NS11GPS/Feathertouch/Starizona Virtual View
100ED/Giro II
Some eyepieces and a barlow
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bseltzer
sage
Reged: 10/28/07
Posts: 306
Loc: East S.F.Bay, CA
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The long and short of it is wood is dimensionally unstable. Over time, wood crawls all over the place. This characteristic can be reduced with various treatments and finishes, but never eliminated.
-Bert
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8" F4 Newtonian (Royce Mirror)
SV 105 APO Raptor
SV 80/9D (Erstwhile guide scope)
Losmandy G-11/Gemini L4
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SBIG ST-4000 XCM
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dancerchris
member
Reged: 08/12/09
Posts: 12
Loc: Southern, CA
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Plywood is dimensionally stable. A torsion box structure out of plywood is very ridgid, dimensionally and thermally stable.
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Televue Genesis
20mm, 9mm and 3-6mm Naglers (and zoom)
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Eddgie
Carpal Tunnel
Reged: 02/01/06
Posts: 2704
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Yes, over time, it might be, however that is what latitude and azimuth adjustments are for.
From night to night, and even month to month, a wood pier would not change shape enough to affect anything.
I have known of a couple of people that used old telephone pole sections for peirs in their back yards, and they seemed happy with the choice.
Best would be to build a beam by laminating say 4 2x4s together so that deminsonal changes will want to cancel each other out (or use the box section plywood mentioned already).
Modern paint can make woods almost impervious to the elements that it would be exposed to for observatory usage.
Wood is cheap, can be worked with hand tools, can be EASILY cut or drilled in to accept trays or other accessories, and can be stiffer and less prone to vibration on a pound to pound basis.
After seeing a telephone pole sectoin pier once, I almost considered doing it for myself.
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Celestron C14, CGE (Big Al)
Astro-Physics 6" f/8 (Buffy)
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Patrick
Postmaster
Reged: 05/16/03
Posts: 7810
Loc: Franklin, Ohio
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HERE's My Wood Pier thread. I've found that the pier is plenty stable for my mounts. The only negative is that the low resonance frequency of the pier is not as good as a steel or concrete pier, but then the pier's performance depends on how tall it is. As far as dimensional stability, with 4-6x6's laminated with glue and bolts, it's not going anywhere. I'll let you know more after it's gone through a freezing/thawing period this winter. 
I had slightly different goals when I built my wood pier and if I were building a real observatory, I don't think I would have hesitated building the pier with concrete block or steel. But, overall I'm happy with the wood pier for the money I've got invested in it and it's serving me well. My main goals were to isolate the pier from the deck and to be somewhat asthetically pleasing and at a low cost. I think I spent around $600 for everything, including the hired labor. The hardest part was digging the hole, which I was glad to pay somebody else to do. 
Patrick
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10" f/6 Truss Tube Newtonian
Celestron C6S-GT SCT
AT66ED Refractor
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Eddgie
Carpal Tunnel
Reged: 02/01/06
Posts: 2704
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While I do think that wood can be used to make a pier, the CHEAPEST and BEST piers that I have seen in observatory use have been concrete.
Use the same tubes that are used to build house piers in pier and beam house construction. Any company that does home leveling can sell you one. They are basically just big cardboard tubes. They can even be left in place and painted.
You can also simply sink your mounting bolts right into the pour. Use a plywood template to anchor them in place the correct depth. In fact, if you want get fancy, you can even put nuts on the ends and wrap the theaded rod with paper so that the rod can be removed or adjusted for length in the future.
A concrete pier is EASY to make, cheap to make, and perhaps the most solid to make.
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Celestron C14, CGE (Big Al)
Astro-Physics 6" f/8 (Buffy)
Televue 101 (No name, but I call it my Widescreen HD Space TV)
The night sky is my mistress. She seduces me away from all other lovers.
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Patrick
Postmaster
Reged: 05/16/03
Posts: 7810
Loc: Franklin, Ohio
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Quote:
A concrete pier is EASY to make, cheap to make, and perhaps the most solid to make.
It really depends on how tall it is. Anything over 4 feet and it's probably better to use concrete block.
Patrick
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10" f/6 Truss Tube Newtonian
Celestron C6S-GT SCT
AT66ED Refractor
Oberwerk Ultra 15x70 Binocular
475B Geared Tripod & 501HDV Head
Celestron Regal 8x42 Binocular
Canon XSi; Meade DSI;SPC900-NC
Vixen GP2 Photo Guider Mount
My Astronomy Pages
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Doug Culbertson
Pooh-Bah
Reged: 01/06/05
Posts: 1353
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Thanks for the replies, everyone! I keep thinking that I want to use a good thick wood pole, like a telephone pole section. These can be purchased pretty reasonably around here every couple of years when poles are replaced. Fortunately, here in N. Florida I don't have to worry about issues like frost heave. We may get four or five nights in the upper teens to twenties, but those are few and far between.
OTOH, it does seem simple enough to make one from concrete too. My problem with either method is that I am currently using a NS11GPS, but you never know when I may get the urge to upgrade to a C14, which would require a taller pier. I would hate to have to replace wood or concrete!
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Doug
Midway, FL
NS11GPS/Feathertouch/Starizona Virtual View
100ED/Giro II
Some eyepieces and a barlow
1 Thermacell®
Life's too short to drink cheap beer
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roscoe
super member
Reged: 02/04/09
Posts: 192
Loc: Northwestern Mass
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You could always build the lower section out of concrete, then use a wood or steel pier extension to get to the right height for your current scope. That way, even if you get dob fever, you're safe.
If you use wood, try to get some stock that has been stored inside, or at least under cover, for a long time, as it'll be more dimensionally stable.
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Antares/Vixen 812 120mm f/8 on reworked CG-5,
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Patrick
Postmaster
Reged: 05/16/03
Posts: 7810
Loc: Franklin, Ohio
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Here's a photo of my wood pier with my AP gear sitting on it.
Patrick
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10" f/6 Truss Tube Newtonian
Celestron C6S-GT SCT
AT66ED Refractor
Oberwerk Ultra 15x70 Binocular
475B Geared Tripod & 501HDV Head
Celestron Regal 8x42 Binocular
Canon XSi; Meade DSI;SPC900-NC
Vixen GP2 Photo Guider Mount
My Astronomy Pages
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oldsalt
Astro Philosopher
Reged: 02/12/05
Posts: 8677
Loc: Pa - between starparties
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The biggest problem, especially in Florida, would be termites. An old telephone pole would work, but be sure it is treated well. Also you do not want one that has been kreosoted.
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There are no winners in war, only bigger losers.
Jim
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mish
member
Reged: 02/10/09
Posts: 76
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As Jim has stated, the biggest problem with wood is that it will decompose if given a chance. So you need to protect it from termites and such (which often involves chemicals that you don't want your kids around), and you definitely need to protect it from wet/dry cycles, which will degrade wood very quickly.
So if you have intermittent high ground water problems, then wood isn't a great choice.
Wood is almost as stiff (i.e., ratio of stress to strain) as concrete, but it's a LOT lighter than concrete, so it exhibits more high-frequency behavior, but that shouldn't be a problem. Like concrete, wood tends to damp vibration pretty well by virtue of its composition (in concrete, damping occurs at the aggregate/cement paste interface: in wood, at the lignin-cellulose interfaces where cells are glued together to form wood fibers), so it should work well enough.
The main reason I would tend to avoid timber piers is that there are no good ways to treat wood that are guaranteed safe around inquisitive young ones. Old treated wood members used arsenic salts, more modern ones use copper, but neither is what you'd like to have your kids leaning against. You could use old-growth redwood (heartwood), which is about as decay-resistant as timber gets (with no treatment beyond a good sealer), but that costs a fortune, and really, old-growth redwood belongs in parks, not under a telescope.
And finally, the bolts that hold the mount to the timber pier will likely be attached to end grain (i.e., they will be pointing in the same direction as the grain of the wood). That's a bad idea if the wood dries out, as those bolts will loosen as the wood fibers shrink away from them.
So if you're going to use wood as a pier, get plenty of sealer, and don't shy away from putting plenty on the top surface -- the cells will soak it up, but just add another coat and you should be fine.
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Doug Culbertson
Pooh-Bah
Reged: 01/06/05
Posts: 1353
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Some excellent replies, thanks! Yeah, here in Florida termites are definitely a problem. I live in a rural area and my property is about half wooded, so I have them all over the place.
BTW, Jim,I have had my dealings with kreosote, and I am 100% in agreement with you on wanting to avoid it. While I don't have small children anymore, I also don't want to be in constant contact with too many chemicals either. I have seen untreated telephone poles for sale, or at least untreated as far as kreosote is concerned. That's more or less what I had in mind. Mish also has some good points about bolting the mount to end grain though. That's what I love about CN, someone always gives you more to think about! 
BTW, Patrick, that is an impressive wooden pier you built!
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Doug
Midway, FL
NS11GPS/Feathertouch/Starizona Virtual View
100ED/Giro II
Some eyepieces and a barlow
1 Thermacell®
Life's too short to drink cheap beer
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oldsalt
Astro Philosopher
Reged: 02/12/05
Posts: 8677
Loc: Pa - between starparties
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Doug, you may be able to find some cypress poles. They are usually untreated and could work. Unfortunately, you will probably have to look long and hard to find them. Another problem is knots if you do find them. Just a thought , if you do decide on wood.
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There are no winners in war, only bigger losers.
Jim
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Patrick
Postmaster
Reged: 05/16/03
Posts: 7810
Loc: Franklin, Ohio
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Regular pressure treated lumber is ideal for a wood pier application. As long as the timbers are encased in a concrete footer they should last a very long time.
Patrick
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10" f/6 Truss Tube Newtonian
Celestron C6S-GT SCT
AT66ED Refractor
Oberwerk Ultra 15x70 Binocular
475B Geared Tripod & 501HDV Head
Celestron Regal 8x42 Binocular
Canon XSi; Meade DSI;SPC900-NC
Vixen GP2 Photo Guider Mount
My Astronomy Pages
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HandyAndy
professor emeritus
Reged: 01/11/08
Posts: 652
Loc: West Midlands and around
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Hi,
Even with a treated post its only the surface which is effectively treated. You must re-treat any cut ends.
Before I stick any wood pole in concrete I want to last I stand it for a few weeks in a bucket with Cuprinol treatment to allow it to soak right into the whole timber which is in the concrete and will get splashed by rain of the ground with microbes in it. A bit of patience pays long term dividends.
Cheers. Andrew.
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Monarch 8x42, Zeiss 10x50 WA
10mm F2, Pentax 60mm F5
City: 7" MN78: MK4#2, 10" F6.3: MK4#1, 16" F5 ParaCorr
Country: 8" VISAC: (GP2)
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Doug Culbertson
Pooh-Bah
Reged: 01/06/05
Posts: 1353
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Andrew, thanks for that information. I am not familiar with Cuprinol but, then, I'm not exactly a woodworker either! I have found all of the responses in this thread very helpful, though I am still undecided as to whether I will eventually end up using a wood pier, concrete, or steel.
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Doug
Midway, FL
NS11GPS/Feathertouch/Starizona Virtual View
100ED/Giro II
Some eyepieces and a barlow
1 Thermacell®
Life's too short to drink cheap beer
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macular hole
super member
Reged: 08/12/09
Posts: 148
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A couple points on treated wood-
1. Modern treated wood is available in solid posts up to about 10"x10" by 8 ft long.
2. The treament actually does penetrate the entire board.
3. For the best longevity in an inground application, it is best not to use a concrete base.
4. The end grain will be soft, while still wet, but will harden up when it dries completely.
5. You must use stainless steel hardware or galvanized hardware that is rated for modern treated wood. Otherwise the hardware will rust and fail.
6. It is completely unnecessary to paint, or retreat modern treated wood. The end grain does not need to be soaked in anything to increase longevity.
&. I have pulled 4x6 treated fence posts that were placed in well drained soil, without concrete bases, that looked as good as they did the day they were placed in the ground 23 years ago. That includes the exposed end grain at the top and bottom of the posts. In fact, I reused all of them for another fence.
Edited by macular hole (09/18/09 10:31 AM)
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John Carruthers
Skiprat
Reged: 02/02/07
Posts: 2273
Loc: Kent, UK
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how about an old railway sleeper? in the UK we get them used from garden centres and reclaimed building materials yards. Maybe 2 bolted together, last pretty well for ever.
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Jc
ATM 10" F6.1, 1/25th wave spec (max wavefront error +/- 1/12.6 in zone 4 of 6, sodium light )
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gnowellsct
professor emeritus
Reged: 06/24/09
Posts: 733
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What about AZEK? (synthetic wood)
Greg N
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"Aperture will get you through times of no money better than money will get you through times of no aperture."
featuring selected astrojunk:
bunch o' widefield eyepieces
bunch o' narrowfield eyepieces
couple o' Barlows
couple o' scopes
couple o' mounts
couple o' tripods
and a pier 'n' stuff
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Doug Culbertson
Pooh-Bah
Reged: 01/06/05
Posts: 1353
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Quote:
how about an old railway sleeper? in the UK we get them used from garden centres and reclaimed building materials yards. Maybe 2 bolted together, last pretty well for ever.
Around here railroad ties (US term) tend to be infested with termites by the time they are dropped off at the home improvement center. I don't know if that is just a Florida problem or not, as our whole state is infested with termites.
Greg, would that be the stuff that's made from recycled bottles and such? If so, I have seen it, but only in decking planks that are something like 1x6 or so.
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Doug
Midway, FL
NS11GPS/Feathertouch/Starizona Virtual View
100ED/Giro II
Some eyepieces and a barlow
1 Thermacell®
Life's too short to drink cheap beer
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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I have seen 4x4 and 6x6 "lumber" made out of recycled plastic - gets used on docks here in one of the marinas. Not sure about it's properties in terms of vibration and the like, but at least it will not shink/grow when getting wet/dry. Treated lumber is likely to be less expensive though.
I would beware of railroad ties... while structurally I am sure they would be fine, all of those that I have seen up here have been creosote soaked.
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Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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macular hole
super member
Reged: 08/12/09
Posts: 148
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Here is what I would do-
Once treated lumber dries out thoroughly, it will hardly move at all. It becomes very stable. Particularly these large posts. It will shrink quite a bit initially as it dries.
1. Call all of your local lumber yards and see if they have the 10"x10"x8ft treated posts. If you find one, buy it.
2. If you can't find 10x10's, go to Lowes or Home depot and get an 8x8x8 for about $60.
3. While at Lowes, get 5-50lb bags of quickrete $20 and a hand post hole digger $20, string, and long spike nails $10.
4. Dig 10-12" diam hole about 3-4 ft deep.
5. Stick post in hole, level and plumb. Secure post with string or rope, tied to spikes in ground.
6. Mix Quickcrete with water, pour in hole.
7. 2 hours later, Crack beer purchased with money saved, contemplate how you are going to attach the mount, and smile at the job well done!
If it does not work out, borrow chainsaw, cut off post below ground level, cover with dirt.
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Doug Culbertson
Pooh-Bah
Reged: 01/06/05
Posts: 1353
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Quote:
Here is what I would do-
Once treated lumber dries out thoroughly, it will hardly move at all. It becomes very stable. Particularly these large posts. It will shrink quite a bit initially as it dries.
1. Call all of your local lumber yards and see if they have the 10"x10"x8ft treated posts. If you find one, buy it.
2. if no 10x10's then go to Lowes or Home depot and get an 8x8x8 for about $60.
3. While at Lowes, get 5-50lb bags of quickrete $20 and a hand post hole digger $20, string, and long spike nails $10.
4. Dig 10-12" diam hole about 3-4 ft deep.
5. Stick post in hole, level and plumb. secure with string or roop tied to spikes in ground
6. Mix quickcrete with water, pour in hole.
7. 2 hours later, Crack beer purchased with money saved, contemplate how you are going to attach the mount, and smile at the job well done!
If it does not work out, borrow chainsaw, cut off post below ground level, cover with dirt.
Kinda what I had in mind! Especially the part about the beer... 
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Doug
Midway, FL
NS11GPS/Feathertouch/Starizona Virtual View
100ED/Giro II
Some eyepieces and a barlow
1 Thermacell®
Life's too short to drink cheap beer
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mish
member
Reged: 02/10/09
Posts: 76
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Quote:
I have pulled 4x6 treated fence posts that were placed in well drained soil, without concrete bases, that looked as good as they did the day they were placed in the ground 23 years ago.
The treatments used on wood 23 years ago were generally toxic (some exceptions occur, but not many). If you placed those timbers 23 years ago and they were brand new, then they were most likely impregnated with various salts, including ones based on arsenic. Those salts can (and generally will) leach from the interior of the timber member onto its surface, and if children encounter these salts repeatedly, the risk of health problems is unacceptably high.
More modern treated lumber uses less dangerous preservatives (e.g., based on copper without attendant arsenic), and these are also being phased out (as were the arsenic compounds about a decade ago). The risk is simply too high, as the handling instructions for treated timber indicate (e.g., all sawdust from cutting operations should be collected for proper disposal).
Treated timber is generally made from sapwood, which is a living part of a tree (in contrast with heartwood, which is not). Sapwood in a live tree carries nutrients from the roots to the leaves, and hence its cellular structure is well-suited for conveying water-based chemicals. When wood is treated, it is generally soaked under pressure in the presence of the preservative, and the sapwood cells carry the various chemicals throughout the timber member, which is great if we are talking about railroad ties, but not so great for observatory piers.
The fundamental problem with wood is that it is a highly-reduced chemical system, so that it has a strong natural propensity to oxidize, either rapidly (via fire) or slowly (via decay). Resisting decay is difficult without use of some serious chemicals, and that is the Achilles' heel of timber construction, at least for any timber that is in contact with the earth.
Again, timber should work well for piers if properly detailed and protected from decay. The question is whether the risks inherent in that protection are serious enough to warrant choosing another material, e.g., concrete. This kind of question is generally the first consideration in the design of any structure, including telescope piers. In my case, e.g., where I routinely have inquisitive youngsters around, it's not worth the risk, and I'm about to pour a concrete pier. For other folks, well, your mileage may vary...
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scubaanddreams
super member
Reged: 11/24/08
Posts: 143
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The biggest lumber my home depot carries is 2x6...I just went in search of a possible "pier" 
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My "Urban Observatory"
http://www.lamesaobservatory.com
La Mesa, Monterey Ca
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macular hole
super member
Reged: 08/12/09
Posts: 148
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Quote:
The biggest lumber my home depot carries is 2x6...I just went in search of a possible "pier"
Come on, I said crack beer after the job is done, not before!
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HandyAndy
professor emeritus
Reged: 01/11/08
Posts: 652
Loc: West Midlands and around
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Hi,
Why not a composite pier?
Use 4 alloy angles as big as you want as corner pieces.
Make a frame out of alloy at the bottom to be concreted in to a base holding the 4 alloy angles upright. Drill and countersink a few screw holes above ground. Use some aluminium paint OWHY to give some protection to the alloy. It may not 'rust' but it will oxidise.
Slide a piece of varnished wood or exterior plywood box for a larger pier, down between the 4 alloy angles and screw in place, not touching the ground. That will provide damping and it can be replaced.
Bolt the top plate to the 4 alloy angles.
?
Cheers. Andrew.
--------------------
Monarch 8x42, Zeiss 10x50 WA
10mm F2, Pentax 60mm F5
City: 7" MN78: MK4#2, 10" F6.3: MK4#1, 16" F5 ParaCorr
Country: 8" VISAC: (GP2)
Car: 6" F5 MPCC: SP, 5" 127mm F7.5 (GP2)
TV 55mm, Paragon 40mm, UO Pretoria 28mm
B&L 32 Pl, Clave's 25, 8, 6, 2x
Hyperions 5, 8, 13, 17, 24, 31
Nagler1 9mm, Meade 14mm 4000 UWA
Antares 1.6x, 0.7x, 0.5x
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macular hole
super member
Reged: 08/12/09
Posts: 148
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Quote:
Quote:
I have pulled 4x6 treated fence posts that were placed in well drained soil, without concrete bases, that looked as good as they did the day they were placed in the ground 23 years ago.
The treatments used on wood 23 years ago were generally toxic (some exceptions occur, but not many). If you placed those timbers 23 years ago and they were brand new, then they were most likely impregnated with various salts, including ones based on arsenic. Those salts can (and generally will) leach from the interior of the timber member onto its surface, and if children encounter these salts repeatedly, the risk of health problems is unacceptably high.
More modern treated lumber uses less dangerous preservatives (e.g., based on copper without attendant arsenic), and these are also being phased out (as were the arsenic compounds about a decade ago). The risk is simply too high, as the handling instructions for treated timber indicate (e.g., all sawdust from cutting operations should be collected for proper disposal).
Treated timber is generally made from sapwood, which is a living part of a tree (in contrast with heartwood, which is not). Sapwood in a live tree carries nutrients from the roots to the leaves, and hence its cellular structure is well-suited for conveying water-based chemicals. When wood is treated, it is generally soaked under pressure in the presence of the preservative, and the sapwood cells carry the various chemicals throughout the timber member, which is great if we are talking about railroad ties, but not so great for observatory piers.
The fundamental problem with wood is that it is a highly-reduced chemical system, so that it has a strong natural propensity to oxidize, either rapidly (via fire) or slowly (via decay). Resisting decay is difficult without use of some serious chemicals, and that is the Achilles' heel of timber construction, at least for any timber that is in contact with the earth.
Again, timber should work well for piers if properly detailed and protected from decay. The question is whether the risks inherent in that protection are serious enough to warrant choosing another material, e.g., concrete. This kind of question is generally the first consideration in the design of any structure, including telescope piers. In my case, e.g., where I routinely have inquisitive youngsters around, it's not worth the risk, and I'm about to pour a concrete pier. For other folks, well, your mileage may vary...
Mish, you make some excellent points.
However,
The treated 8x8's or 10x10's that I have used consist of both the heartwood and the sapwood. They are basically an entire log that has been treated and dimensionalized for building purposes.
They are massive in both size and weight. I firmly believe they will work very well for a pier application when used with quickrete and buried 3-4 ft in the ground. I also believe that my little project, as outlined above, would be the cheapest and easiest method of pier construction, by far.
As to concerns about potential toxicity to children, all I can say is that in the US, 90% of all outdoor decks are made from treated wood. 95% of all 3 and 4 rail fences on ranches and farms across our country are made from treated wood. Finally, the building code in most/all US communities requires the use of treated wood in situations where wood is in direct contact with concrete, as in a basement floorplate.
One 8x8x8 ft treated wood pier in the ground is the equivalent of *BLEEP* in the ocean, IMHO.
Also, as I outlined above, the treated wood pier has the additional major benefit of being easy to remove, if you move or lose interest. Now, I'm going to empty my french press and come up with the cheapest, easiest, best looking way to attach a top plate. 
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
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I did one about 30 years ago .... I used an old railway sleeper (in those days wood sleepers were the common and you could them secondhand for next to nothing).
I believe the wood was Ironbark ,,,, hard as all heck , the hardest hardwood you could get.
I think you can still get them here from gardening centres , they are great for making raised garden beds and vege patches .... Termites like them too.
It was still there when mum and dad retired and moved to Forster and it was solid as a rock (about 15 years ago).
I used a 6" length of the same stuff (6"x6" when I put my mailbox in. That was 28 years ago and it's still there and though it looks a bit weathered and rustic , it's still solid , I can't budge it no matter how hard I kick or push on it .... the termites haven't touched it either.
I don't think a tumber pier would be much good though for putting a big heavy telescope and GEM on , I think it'll have too much give in it unless it's an enormous pier.
Edited by Ian Robinson (09/19/09 10:27 AM)
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mish
member
Reged: 02/10/09
Posts: 76
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Quote:
The treated 8x8's or 10x10's that I have used consist of both the heartwood and the sapwood. They are basically an entire log that has been treated and dimensionalized for building purposes.
A 1-foot DBH tree that gets turned into an 8x8 would likely not have any heartwood -- note that "heartwood" is not synonymous with "center of the log". Heartwood tends to form in much older trees, and it is not preferred for pressure treatment of chemicals, because the preservatives aren't readily dispersed through heartwood.
Quote:
They are massive in both size and weight. I firmly believe they will work very well for a pier application when used with quickrete and buried 3-4 ft in the ground. I also believe that my little project, as outlined above, would be the cheapest and easiest method of pier construction, by far.
I agree with you there. I use this form of construction a lot, including construction going back into the pentachloraphenol days (long before arsenic got banned). Timber really works well for a lot of uses, as long as due respect is paid to remedying its disadvantages.
Quote:
As to concerns about potential toxicity to children, all I can say is that in the US, 90% of all outdoor decks are made from treated wood. 95% of all 3 and 4 rail fences on ranches and farms across our country are made from treated wood. Finally, the building code in most/all US communities requires the use of treated wood in situations where wood is in direct contact with concrete, as in a basement floorplate.
I'm fully aware of that -- in addition to building decks, fences, and even homes as a sideline, I teach the timber design course here at our university. I fully appreciate the value of wood construction -- but you'll note that the prevalence of treated timber in decks and fences is what has driven the removal of CCA-treated lumber (containing arsenic) from the marketplace, as the health effects can be dire.
As far as the treatment of the bottom sill in stud-wall construction, note that member is invariably removed from contact with people, e.g., by sheetrock or other wall coverings. So regular contact with kids is not a problem there.
Quote:
One 8x8x8 ft treated wood pier in the ground is the equivalent of *BLEEP* in the ocean, IMHO.
The only important thing to take away about this is that if the treated post is old (and hence contains arsenic), and if that arsenic leaches to the surface, then people should avoid regular contact with it, e.g., touching it, etc. The risk is very real (that's why it's been removed from the market!).
But that risk is also very easy to mitigate, e.g., with a timber covering. I have a treehouse here supported by CCA-treated 6x6's and 4x6's, and all the members that children might be exposed to are covered with 1x poplar boards. Those weather very well, don't warp when properly anchored into the underlying main structural members, and they look really nice, too.
So it's easy to mitigate the problem by good design. But it's always worthwhile examining the risks of chemical treatments (I always have, and I've survived decades of CCA and Penta timber treatment exposures!)
Quote:
Also, as I outlined above, the treated wood pier has the additional major benefit of being easy to remove, if you move or lose interest. Now, I'm going to empty my french press and come up with the cheapest, easiest, best looking way to attach a top plate.
That's potentially one of the best advantages of a timber pier -- the ease of attaching (or reattaching) a top plate. Compare that task to concrete (how on earth do you modify concrete after it's cured?), and one of the primary advantages of timber construction becomes obvious: it's easy to work the stuff.
Good luck with your digging!
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HunterofPhotons
sage
Reged: 04/26/08
Posts: 266
Loc: Rhode Island, USA
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Macular Hole,
I've worked wood all of my life and Mish's post is right on the money. I've included some of my own comments below.
Quote:
Mish, you make some excellent points.
However,
The treated 8x8's or 10x10's that I have used consist of both the heartwood and the sapwood. They are basically an entire log that has been treated and dimensionalized for building purposes.
*** In the US these treated timbers are made with Southern Yellow Pine, which is one of the worst woods to work with. It splits, cracks, and warps with abandon. Contrary to popular opinion, pressure-treated wood is NOT the only wood that can be used in outdoor situations. There are plenty of suitable local woods that will last as long and are much more stable. You will probably have to go to a real lumber yard (not Lowe's or Home Depot) to find them.
Quote:
They are massive in both size and weight. I firmly believe they will work very well for a pier application when used with quickrete [sic] and buried 3-4 ft in the ground.
*** Once again, contrary to popular opinion, this is not the best way to anchor a post in the ground, especially a large one. The concrete restricts any and all seasonal movement in the wood. As you correctly pointed out, the initial shrinkage in PT wood is at the start, but even after this initial shrinkage this wood will move with the seasons and changes in humidity. When it tries to expand in concrete the wood fibers are crushed. When the post subsequently shrinks, the revealed space allows water to enter and rot the post. Replace the concrete with gravel for long life.
Quote:
I also believe that my little project, as outlined above, would be the cheapest and easiest method of pier construction, by far.
*** Cheap and easy, yes. Safe and stable, not so much.
Quote:
As to concerns about potential toxicity to children, all I can say is that in the US, 90% of all outdoor decks are made from treated wood. 95% of all 3 and 4 rail fences on ranches and farms across our country are made from treated wood.
*** I'm sure that your percentages are hyperbole, but the point is that poisons are the 'treat' is treated wood, even the ones sold today. Even the manufacturer recommends hand washing after touching the wood, and for the life of the product. Have you ever gotten a splinter from PT wood? It results in a nasty suppurating wound.
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One 8x8x8 ft treated wood pier in the ground is the equivalent of *BLEEP* in the ocean, IMHO.....
*** Ah, but if we all do our part....for, after all, it takes a village to poison a child. <g>
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mish
member
Reged: 02/10/09
Posts: 76
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Hunter (of Photons):
Slightly off topic, but hopefully I won't be barred for this tangent:
Quote:
... wood will move with the seasons and changes in humidity...
The first thing I ever built of timber was an alder dinner table. I took great care to flip the grain curvature of the wood on adjacent members (so the net warping with humidity would cancel itself out), and thought I had detailed everything just right... and then I glued and doweled a 2x2 alder edge piece around the entire perimeter of the table, including doweled rigid connections at the corners.
In short, I constrained the wood structure against lateral motion.
That table would flap with the seasons, and would go from near-perfectly flat in the summer to so barrel-shaped in the winter that dinner plates would start sliding off onto laps if the right place mats were used.
Since then, I've learned never to underestimate just how much a timber member enjoys changing its size with humidity.
Obviously, I second your suggestion about gravel. Concrete is fine if you're in a hurry and don't mind some lateral motion (tho don't set the bottom of the post on concrete -- set it on gravel at its base, always!), but for a telescope pier, even the slightest lateral motion would be unacceptable.
Lots of really well-compacted gravel is a better answer... so thanks for pointing that out!
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scubaanddreams
super member
Reged: 11/24/08
Posts: 143
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Ok; found 6x8 and here it is. Now how do I attach an eq6 head with extension the best way? then I will have my beer.
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My "Urban Observatory"
http://www.lamesaobservatory.com
La Mesa, Monterey Ca
Edited by scubaanddreams (09/19/09 06:50 PM)
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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Quote:
Now, I'm going to empty my french press and come up with the cheapest, easiest, best looking way to attach a top plate
I have an idea for attaching the mount plate to the end of a wood pier that might help with the end-grain problem. Rather then bolting into the top of the pier use two "angle iron" segments - aluminum or steel L shaped bars - lag-bolted into the wood with mount bolt holes in their tops.
I know around here there are consumer-facing scrap metal places where it is easy to get some nice thick aluminum angle irons. Those are quite easy to work with.
I am not sure if that matches your "best looking" criteria, but it should be cheap and easy!
- Sean
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
Edited by Falcon- (09/19/09 07:01 PM)
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macular hole
super member
Reged: 08/12/09
Posts: 148
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Quote:
Ok; found 6x8 and here it is. Now how do I attach an eq6 head with extension the best way? then I will have my beer.
Nice Job Scuba. That is a serious looking chunk of lumber. Can you give us a rough estimate of your time and materials to this point? Did you use quickrete in the hole?
Can you post a photo or two of your mount, particularly the bottom and underside?
Also, how much clearance do you need around the mount? IE. If you plopped it right down on the top of the pier, would anything on the mount wack into the pier as the scope moved?
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scubaanddreams
super member
Reged: 11/24/08
Posts: 143
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That took all of 30 minutes including cutting the lumber to the height I wanted. Yup, I used 3 bags of quikrete. It feels solid as rock. I don't have my computer at the moment (on iPhone) but it's a standard eq type connection--someone mounted an eq6 by drilling 3 holes in bottom but he used a concrete pier. If I could figure out how to insert 3 10" 1/2 all thread bolts the best way that would suffice...(or should I just screw them in?)
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My "Urban Observatory"
http://www.lamesaobservatory.com
La Mesa, Monterey Ca
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scubaanddreams
super member
Reged: 11/24/08
Posts: 143
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BOttom plate of extension. Note I also have a shorter extension, the important thing to figure out is how to mount that plate to the wood pier. Any help is appreciated.
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My "Urban Observatory"
http://www.lamesaobservatory.com
La Mesa, Monterey Ca
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EddWen
sage
Reged: 04/26/08
Posts: 367
Loc: Here or There
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Not exactly the same, but this thread might give you some ideas:
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/2730123/page/4/view/collapsed/sb/5/o/all/fpart/1
Good luck.
Quote:
Ok; found 6x8 and here it is. Now how do I attach an eq6 head with extension the best way? then I will have my beer.
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Edd Weninger
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**** Lightshield Observatory SoCal ****
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**** Blackdog Observatory Arizona ****
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sailor70623
scholastic sledgehammer
Reged: 01/12/08
Posts: 944
Loc: Ok.
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Nice pictures. OK I like treated wood and don't worry about getting poisened. When I wa a kid we played on play ground equipment made form old telephone poles, the arsenic treated type. Burned the scraps from when they built it in our fire place. Haven't died yet. For Fla. I would slap a solution of boric acid (roach proof) good old glycolated alcohol (green anti freeze) and orange oil on the wood. There's not a bug or fungus that will live on that surface. It's a mixture we used when rebuilding old wood boats, kills rot an fungus, termites won't touch it. The oragne oil and alcohol will leech out if it gets too wet, so it may have to be retreated every year. I treat all wood this way before painting it, if it's going to be anywhere near the ground. I have sheds that are going on 30 years old in Fl. treated this way, no problems. Even when both neighbors have been tented, one twice, for termites and I had to replace a window sill due to the buggers. I also liked cloridane untill I ran out, and am down to my last bag of Diazinon his year. I HATE bugs, especially ants. Now if I could just find something that would kill flies and mosquitos well. Wish they would bring back DDT.
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Corornado PST
LB 16" & 12"
Z 10"
LX50 8"
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ETX127
102&90mm MAKs
80mm Richfield APO
70mm refractor
ETX60
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macular hole
super member
Reged: 08/12/09
Posts: 148
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Quote:
BOttom plate of extension. Note I also have a shorter extension, the important thing to figure out is how to mount that plate to the wood pier. Any help is appreciated.
Scuba could you give me an idea of the overall diameter of that bottom plate and the diameter of the inner circle that protrudes down from it with the screw hole?
Lowes has 10 inch long threaded rod in various diameters up to 3/4 inch. You can buy 3-4 of them at $4 a piece. if you go with 1/2" Diam by 10 inchers, just buy a 1/2 inch wood bore drill bit and drill 3 or four holes straight down into the top of your pier, about 5 inches deep. Fill each hole about half way up with polyurethane construction adhesive speced for use with treated wood. You can then just pound the threaded rod into the holes. The threaded rod can then be cut to the length you want with a hacksaw or sawzall with a metal blade. The key is that you want the holes to be as straight and parallel as possible. There are hand drill guides that you can possibly rent or borrow from someone that will provide you with a very straight hole.
Does that bottom plate come all the way out of the extension? if it does, I have a very easy solution for you.
Edited by macular hole (09/20/09 04:55 PM)
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macular hole
super member
Reged: 08/12/09
Posts: 148
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Quote:
Quote:
Now, I'm going to empty my french press and come up with the cheapest, easiest, best looking way to attach a top plate
I have an idea for attaching the mount plate to the end of a wood pier that might help with the end-grain problem. Rather then bolting into the top of the pier use two "angle iron" segments - aluminum or steel L shaped bars - lag-bolted into the wood with mount bolt holes in their tops.
I know around here there are consumer-facing scrap metal places where it is easy to get some nice thick aluminum angle irons. Those are quite easy to work with.
I am not sure if that matches your "best looking" criteria, but it should be cheap and easy!
- Sean
Sean, I like your idea as well. I would modify it as follows for Scuba using just one piece of aluminum angle that is 6x6x 71/2" long and 3/8"thick-
www.onlinemetals.com has aluminum angle that is 6 inches by 6 inches by 3/8" thick. You can get a piece that is 12 inches long for $27. They will even cut this to 7 1/2" inches for a small added fee. This will cover the entire top of the pier and will allow plenty of room under it for access to the mount bottom plate screw.
I would glue/screw a 7 1/2" long 2x4 layed on its side, under the free, open side of the aluminum angle. This will provide additional support for the otherwise open end of the aluminum angle piece, and provide a 3 1/2" open space between the top of the aluminum angle and the top of the wood pier. This space will allow access to the bolt used to attach the bottom plate of the mount extension. It will be open on both sides.
Aluminum is easy to drill. The tricky part though, is that smaller inner circular projection on the bottom of the mount extension plate with the screw hole in it.
Once it is complete, use a black aluminum paint on the angle bracket, screws, and 2x4 to match the mount!
Rmember to use stainless steel, glavanized, or treated wood screws to attach the aluminum angle plate to the treated wood pier. I would use two or three 1/2" by 3-4" long stainless lag bolts with matching washers. You need to predrill the holes in the wood before you screw in the lags. Use the holes drilled into the aluninum angle for a template to mark the holes.
Always wear safety glasses.
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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That modification sounds good to me - I was guessing at a three or 4 bolt pattern to mount originally, and the 2x4 support on the lose end is an excellent idea.
Does an inset hole really need to be created? I am guessing that it exists for easy centering of the mount onto the tripod or pier, something that is not necessary except for ease of setup if the mount is going to be removed/re-added repeatedly. Especially if a permeant pier extension tube is going to be mounted, then so long as the central bolt is well secured it will not be going anywhere.
--------------------
Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
Edited by Falcon- (09/20/09 04:31 PM)
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HandyAndy
professor emeritus
Reged: 01/11/08
Posts: 652
Loc: West Midlands and around
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Hi,
I have a very similar looking half-pier base.
I found the bottom joint between the base plate and the pier tube had a lot of play. When it was taken apart there was a large gap which someone had try to fill with 3 bits of self adhesive Velcro base.
The top is similar but a previous owner had replaced the Hex bolts with SS thumbscrews with chamfered undersides. If you wiggle the top about and go round and tighten the thumbscrews you can take the wiggle out by seating all the chamfers in the holes.
At the moment my engineer is putting in 8mm bolts in the hope the tube can be distorted enough to clinch up to the plate.
Personally I would bolt 3 bits if angle inside the tube so I could then bolt the base onto the angles.
We will see what works.
I only found the problem when I used the half-pier on a steel base pier. On a tripod its lack of stiffness predominated.
If you could rout 4 slots in the sides of the pier a few inches down from the top to take a nut and drill a clearance hole down to the slot I would think you could get a good solid fix. You would be compressing the wood along its strongest direction.
Cheers. Andrew.
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Monarch 8x42, Zeiss 10x50 WA
10mm F2, Pentax 60mm F5
City: 7" MN78: MK4#2, 10" F6.3: MK4#1, 16" F5 ParaCorr
Country: 8" VISAC: (GP2)
Car: 6" F5 MPCC: SP, 5" 127mm F7.5 (GP2)
TV 55mm, Paragon 40mm, UO Pretoria 28mm
B&L 32 Pl, Clave's 25, 8, 6, 2x
Hyperions 5, 8, 13, 17, 24, 31
Nagler1 9mm, Meade 14mm 4000 UWA
Antares 1.6x, 0.7x, 0.5x
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Joe Hoener
journeyman
Reged: 02/26/09
Posts: 9
Loc: KS now, MA later
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Hedge(Osage Orange trees) posts are commonly used for fence posts here in Kansas. They are impervious to termites, and they do not rot, even after 30 years or more. The wood is so hard that hedge fenceposts are commonly driven by machine into the ground, like a large nail. A chainsaw will make sparks when cutting through a hedge limb. Native hedge should be found anywhere in the Midwest or Plains as a hedgerow or windbreak tree.
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One never know, do one?
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