Is the existing concrete base just a thin layer such as a pathway, or something more substantial? If it's a reasonable thickness, say 200mm or more, and spread over a wide area, then loxins set in the concrete will do a decent job if they're done right, though with the height you're after you'll need as wide a flange as you can get your hands on. I got my flanges from Blackwoods, and they were about $200 each.
The base is the existing concrete floor in my garage. It's been there for A long time so earth would be compacted. I doubt it's 200mm thick. I might drill a section to check. I don't have luxury right now of cutting it and boring a deeper hole so just going to set it to the existing garage floor with wide flange and see how I go.
Probably just get welding shop to weld some 30mm thick square plate to bottom of pipe and set this square plate onto existing concrete. If it's not stable enough then I will have to rethink. It's fairly well out of wind the pier below roof line of rolloff roof.
1.8 metres high will be pretty wobbly on a 300mm plate base. I'd be looking at at least double that, with 4 gussets out to the corners. Be careful, your slab may only be 50mm thick.
It might be worth thinking about pouring a concrete truncated pyramid to about 1m high then mounting an 800mm pier on that.
I meant the bottom plate woudl be 30mm thick not 300mm wide.
Definately agree it needs to be a very wide bottom plate.
Dont have ability to poor concrete. Because its in my garage I need ability to remove it. I figure if I go with a very wide bottom plate and spread the load. even if it is only 50mm thick it might be ok as its 3.5 m wide and about 8 meters long worth of slab. I like idea of loxins as they are set flat to floor and I can remove pier if needed without bolts prottruding from floor. Issue is I need at least 80mm depth to use an M16 loxin.
As you suggest a 600 - 800 mm sqaure plate that is 30mm thick bolted into existing floor should do the job.
Thinking of a 12" pipe around 8mm - 10mm wall thickness,
A 250mm NB pier has an outside diameter of 273mm which would provide plenty of stiffness. A wall thickness of 7.8mm will provide ample strength and should support a couple of thousand kilograms comfortably on top of the pier(serious). A 500mm square 20-25mm thick base plate would probably do with the gussets and you should only need 12mm(16mm if you like) dynabolts(pardon the pun) say 100mm long(20-25mm through the plate and 75-80mm into the concrete slab). Get the “hex head bolt” type which are easier to remove.
Just curious how high your garage ceiling is? If your pier is around 1.8m high and you put a mount on top(around 600mm with saddle plate?), won’t you be at 2.4m before you put a scope on it?
I'm not sure what you want to put on it, but either way, you’ll have one heck of a pier.
Good advice Dave, 20 to 25mm should be enough thickness for the base, but the gussets will be needed to stop flex of the base plate.
Be aware though Clive (if I remember your name correctly, sorry) a 1.8m 250 NB pier, with 25mm thick 500x500 base, plus gussets and a top plate, all as one weldment will be around 200Kg.
Thanks everyone for advice. Stupid question what's NB stand for ?
Also seems like prevailing view is not to have a rats nest on top. Ie the 4 bolts with plate for leveling the top of the pier. Is this still a valid concern?
NB = Nominal Bore, a pipe measurement. You'll also run in to 'Schedule' which is its pressure rating. The bigger the schedule number, the higher the pressure rating, and the thicker the wall.
I stayed away from the extra plate on top as I don't need it, and I feel they are just a point of added flexure. If you don't specifically need it, don't put it on. If you do need an adjustable top plate, there has to be a better way than long flexy bolts!
Thanks everyone for advice. Stupid question what's NB stand for ?
Also seems like prevailing view is not to have a rats nest on top. Ie the 4 bolts with plate for leveling the top of the pier. Is this still a valid concern?
You dont need to level the top of the pier. Eyeballed flat is close enough. You just need some ability to connect the mount and allow adjustment in azimuth. Alt adjustment is done via the mount. A level top just makes it easier to align if you are using a portable set up.
Having said that, the mount and OTA is heavy and if it is properly balanced it should put most of its force straight down the pier.- ie balance on the top of the pier. It the pier it is too tipped it will not balance and exhert more lateral force. This is not ideal for a stable pier.
Seems like a lot of steel and expense with no guarantee of stability.
If you want super strength, and minimal vibrations, mark out a 400x400mm square where your pier will be.
You cut out that part of the concert floor, then dig 600mm down into the soil below.
Buy your pier @ 2.4 long put in the hole, plumb it up, and fill the hole around it with cement, when set after one day, also fill the pipe with cement, and put your top plate bolts in the wet cement at the top.
Leave for at least a week.
One solid pier, that a Mack truck couldn't pull over, no need for base plate gussets, etc, a tidy round pier.
Hi Leon, in post5, Chris mentioned he would like the pier to be removable.
I have 4 x 10mm SS dynabolts securing my pier to a concrete slab. It only has about 70kg sitting on it but it still hasn't fallen over yet. Chris should be good with the M16s and have a reasonably stable mount. A pier is usually loaded in compression(usually), and not designed to have a wild Mack truck tied to it.
A little bit of expense isn't too bad if it is transportable and may be used again. Just MHO
My plan will be to try it bolted to existing slab.
I control everything remotely from inside the house so dont need to worry about vibration during imaging from the floor.
If I find it is not stable enough then I will do what you suggest Leon and cut the concrete, bore a hole , fill it with a plug of around 1metric ton. fix some threaded rod to it below the floor surface and then fix the pier to it.
This way the pier wont be waisted
Also redid my calculations tonight and Pier needs to be 1.49 high.
The Parmount MX I am waiting for is a fair bit taller than my MI250
1630mm total from bottom of base to top of upper flange.
We do make to order. AT 1630mm your in the ballpark and since the base flange has 8 setting holes, just do it with 8 Chemset bolts into your existing slab and your done.
Cheers
.
