Wood pier for casual

[steve000]

Hi all,

I have lurked around and found a few ideas but what is peoples thoughts on a wooden pier for a short term (3-5 years tops) backyard under a removable shed setup.

EQ6 with 6" reflector mounted on it. Visual and casual imaging

The ground is good soil and is located in Brisbane so no chance of a frost layer or anything crazy like that.

I want to go wood because I figure its quick to make and cheap. Some vibration is no issue.

Thoughts, ideas, drawings etc welcome.

My idea, get some hardwood around 100mm to 150mm and put in the ground about 1 meter give or take then hard compacted.

Make a leveling plate from a bunch of bolts and 2x 200mm square sleepers.

[astronobob]

Sounds interesting Steve, I wood ave never thought of this ?
But I suggest going with a 150 x 150mm hardwood square or round post 150 diameter would be pretty solid, providing it is packed in properly, I mean, if a meter in the ground, fill in only the 1st 6inches and go hard with the back end of a crowbar or similar, & keep packing 6" of fill at a time ?
As for the top plate to secure the mount, Id probably use steel directly under the mount, as the securing Bolt for the mount wood need a solid anchoring medium !
but the plate directly on the post could be made of wood I reckon, just my initial thoughts ?

[MattT]

Hi Steve,
If you haven't seen this thread, have a look at this from CN. http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5527689/page/0/view/collapsed/sb/5/o/all/fpart/1
I'm thinking this one over too, the more wood the better it seems. One 150mm pole might not be enough????
Matt

[leon]

No reason why not Steve, if it is solid enough, it would work fine, what a good idea.

Leon

[steve000]

Thanks Matt, thats a good read

I actually do have some steel plates with holes already in them, perhaps they will work better if I can find them.

Im going to take a trip to bunnings and see what they have.

[bindibadgi]

What I found to work really well for filling and compacting (not for a telescope pier though) was to fill the hole with sand (after putting the pier in of course), then lots of water, and then poke it with a thin rod right to the bottom lots and lots. Also make sure to vibrate the rod too. Then put something on the pier to vibrate it for quite a while. This makes the sand settle very nicely, and you'll see bubbles come out. The water helps the sand to compact as well. When it's done, make a little formwork box and pour about 150mm thickness of concrete for a small area around the pier to stop it from moving over time. Keep the concrete wet for as long as you can so it slows the reaction and prevents cracking.

I've had a tall beehive sitting on one such pier (although it was aluminium) for a couple of years now, and it's as rock solid and level as the day it was installed, even though it's subject to all the elements (including some very strong winds) which I assume yours won't be with the shed around it.

[steve000]

All great ideas and feedback.

It looks like I will have to go with a 100mm x 100mm hardwood square post. They only have 75x100 which using 4 makes an odd shape and the 100 x 100 is only 2.4m, I need around 50cm of pier and 1m in the ground meaning I cant use 1 to make 2 posts. If I did total would be 1.2m long leaving 70cm in ground, this may be OK I guess now that I think of it.

The cost of the pier, not how I put it in ground.
42.50 for the Hardwood
Free for sleepers as I already have some, but about $4 cost.
about $20 or so for threaded rod and stuff.

Not bad if you ask me, I thought of around $40 total is around $65-$70

If I were to go for a single 100x100 cost is about $40, this would be fine for an EQ3 perhaps.

[OzEclipse]

4 x 100 x 75 posts can make a 175mm square pier if you think laterally. See the attached diagram.


A friend of mine many years ago 1980's built an observatory near Toowoomba. He cut down a large ironbark tree where he wanted to put the observatory. Rather than remove the stump and roots, he decided to use the stump as his pier. I moved away from Brisbane around that time and lost touch so I don't know how it worked. I heard through a mutual friend a few years ago he was still working at his observatory, don't know if the Byers mount is still on the tree stump.

Joe

[steve000]

Interesting......

I'll price it up and see how it turns out. that will be stronger thats for sure.

Im concerned about the center hole tho, should I fill it with somthing?

[Ric]

If it's possible, you could run your cables etc up the centre hole to keep things tidy.

I'm watching this thread with interest, it's one possibility for my Obs construction.

Cheers

[steve000]

After a disappointing visit to Carselding bunnings I went to lawnton bunnings where I almost cried because they have everything in stock and the staff are good.

I have decided on 90x90mm x 4 bolted together to make a 180mm post. I wont worry about cables because it will not have power all the time as my battery is nice and portable. Its about $60 in wood + the rest of the stuff and should make a solid design.

Also due to the heavy rain of the last few days the ground has soaked in about 50cm making the hole digging very easy even for a unfit bugger like my self. I'll post pictures shortly as I go along.

The cost so far is $50 for a post hole pincer, I needed 1 anyway so its ok.

[OzEclipse]

Steve,

Even though you've decided to go for the 90x90mm I'll answer your question.

The hole in the center would have no effect on the overall strength.

Joe

[steve000]

Fantastic then, well perhaps that would be an option to someone who did want power bring permanent such as a solar setup. You could easily drill a hole mid way and put a little box on the outside with data etc in it.

Anyway attached is a picture of the final plan and the hole dug to around 850mm depth.

The hole was dug in about an hour, turns out brisbanes rain has soaked around 600mm into the ground. Made work pretty easy.

the sketch shows the total pier length on the left and the hole depth above the gravel and plate I put down there as well as the height of my EQ6 tripod which is perfect height for me. Grass texture represents the surface.
I have allowed about 50mm or so of adjustment in height and leveling. I wanted to keep it as small as possible and I don't trust my self to make a wooden pier perfectly level without it. the disk on top is an aluminum adapter plate that a guy on IIS made up for me for my steel pier that has not been put on hold for a while.. (big project will post news later)

Small recesses cut into the wood to allow the bolts to come in. main plates are 50mm thick 200mm square sleepers and 16mm bolts/threaded rods.
Plates attached to pier by 130mm coach screws.

Thanks so for the feedback and suggestions. As usual the IIS community has been great in helping me with a final design.
I would have gone the 100 x 75 but I don't like carseldine bunnings anymore and lawnton only had 90x90 :)

[steve000]

Proof that its actually coming along.

Attached is 4x 90x90mm bolted together
threaded rods for the head
and billy the not so helpful helper. His idea if building a pier is dropping the ball at my feet so I step on it and almost fall over every 3 mins.

I have also made the head, I have discovered my drill press isnt straight so I had to make larger holes in the top but it should be ok.

I finally found the adapter plate that I put safely away. It was always in the way so I put it away and couldn't find it for 3 days. Turns out it was on my tackle box of which I also couldn't find and missed a trip cause of that. Thats what happens when you clean up, if it were messy my gear would be where I left it.

More pics to come. So far a few lazy hours

[ZeroID]

Excellent, the 4 post configuration should minimise any water or environment induced bending. You going to give the timber a sealant coating ? Couple of doses of 50:50 enamel\turps or varnish\turps or if you are going to splurge out some tar based water proofing compound like Bitumastic.

[astronobob]

Looking good Steve, and yep, better seal up that pier, seems like your dog approves ;)
Watching with interest ,,

[steve000]

I am 50/50 on sealing it. Part of me doesnt want to trap any moisture because I cant seal the bottom 100%, it will be close but not perfect.

[ZeroID]

Seal the bottom buried section, any moisture can wick up through the grain to the top exposed section. Use a tar based sealant.

If you want to get really serious about it buy from your marine supplier some Everdure 2 pot. Its an epoxy varnish. First coat goes on with 50% turps and soaks right in, second coat is 25% turps, last coat is 100% varnish. I've rebuilt boat hulls with that stuff, it never rots !! Turns the wood into concrete.

[steve000]

I'll keep an eye out for that stuff to seal it, or cheap equiv.

bit of an update now, I tapped my first bolt hole with great success, something I have always wanted to do, tick that off.

My test hole worked but was a disaster getting it to work, I was wobbling all over the place so I got thinking.....

For the actual hole I put the cutting bit in the drill press then lined everything up and pulled down as if drilling a hole. I then turned the chuck with the key to slowly cut the thread, not what its intended for but wow did it work. The entire hole was done in about the same time it took to do a 3mm test piece wobbling all over the place.

A strange thing I noticed, whats up with the threads, in the attached pic the red highlighted rod threader doesn't match the bolt, yet the green highlighted hole threader does match. Both are a M10 1.5pitch thread, is my external one dodgy and perhaps needs some work? cheap ebay kit is probably why.

Also attached is a mockup of the pier, just gotta screw on the head and bolt it all together, seal it then chuck it in the ground.

Exciting stuff!

[LewisM]

I am all for using wood for the pier itself, but in no way would I use wood as the actual pier plates themselves! The wood shown is quarter-sawn, which means it will bow/warp in the direction of the grain curve. I would be using metal plates.

I intend putting in a wooden fabricated pier here, using 4 posts coach bolted together. The end will be tar treated, and wrapped in 3 layers of PVC water proof membrane (my former neighbour from years ago is a pool installer, and will give me most of what I require). External wood will get the epoxy varnish drench as mentioned above - I just have to look ahead outside to the treated pine fence to see how much warpage there is in non-sealed wood!!! (reminds me to replace 10 or so boards).

Seeing I CANNOT leave the head on it where I have to situate it all, during times of no use, I was thinking of putting a bird feeder on top! Dual purpose.

[steve000]

I expect some warp, but the goal is to last 5 years tops. I have some metal plates and if it goes bad fast then I'll use them, too much work for now, more of an experiment than anything.

I bolted everything together today and its done, just gotta seal it then build the cover.

[ZeroID]

The good old drill press can be a very useful tool. I do any alignment critical tapping in that.

My pier plate is wood. 2 x 23 mm thick layers of 17 ply epoxied and screwed together then another layer of 7 mm x 5 ply as the mount head base. Varnished and sealed. It hasn't moved at all, perfectly flat and rigid.

[LewisM]

Ply is OK, but NOT quarter sawn treated radiata pine (seeing the wood they use for treated wood is usually "scrub" pine anyway - low quality).

Saw some THICK sheets/plates of clear acrylic/polycarbonate (lexan perhaps?) at Bunnings the other day for $50 for a LARGE sheet, 1.5" thick. Was thinking it would make a GREAT pier head plate - relatively easy to cut and waterproof (though may craze in UV - not sure)

[ZeroID]

Radiata isn't good for anything really. Cheap fences and cheap housing.

The Polycarbonate (?) would never see sunlight, no problem :thumbsup: