Same principle as your bit of ply - but if you take a suitably thick packing piece of timber (like 2"x1"-ish - or whatever the new-fangled equivalent is) and gaffer tape it to one end of your spirit level - you'll now have a spirit level that reads 'vertical' when the thing you're gauging is actually at a specific angle....
(I'm not even going to _try_ to draw it with ascii art - life's too short!)
It's all down to that clever Greek chappie again - but the thickness of the packing piece is dependant on the length of your spirit level, if you see what I mean...
If you want to be _really_ clever - and you don't mind a little bit of engineering, you could always drill / tap a hole though the end of your spirit level and thread a roofing bolt through it, with a lock-nut. You would then have a tool that you could set up for _any_ amount of 'off-vertical' or 'off-horizontal'.... - but it depends how much of your life you expect to spend around tapered bollards
My levels all have three bubbles - one for horizontal, one for vertical and one that can be rotated to any angle. I would calculate the angle, set the rotating bubble and use that to set the sides of the post. However, if you don't want to calculate the angle, you could probably get away with trial and error: Prop the post up against a wall, leaving the rotating bubble unlocked. Keep trying it against opposite sides alternately, adjusting the post and then the bubble, until you can use the same setting on both sides of the post. The post is then vertical, the bubble is at the right setting and it can be locked in place.
Stand all five on a flat surface put a dab of glue and a bit of scrap board on top of each. Lay a large board on top of all of them to keep all teh board level. Let glue set. then each bollard has a flat top you can lay a spirit level on when you fit them.
Thus spake The Medway Handyman ( snipped-for-privacy@nospamblueyonder.co.uk) unto the assembled multitudes:
How about making a 200mm diameter 'hat' for the top of the bollard, and hanging a plumb line from the edge of the hat, so that when it's perfectly vertical the plumb line touches the edge of the base?
Rather than trying to get ply tapered to the right angle, you could cut out two squares of ply both the same size. Then cut out an internal square out of each, one larger than the other. Drop them over a post and you can hold your level against them to get a vertical.
Lie them down with a packing piece under the narrow end? I think you really mean perfectly vertical. B-)
Plenty of other solutions mentioned but if you put your long level against the a side then against the opposite side you simply adjust the vertical of the bollard until the error is the same on both sides. You obviously need to do this in the left/right and front/back planes.
Mark an encircling line (masking tape) fairly close to the top - get position by measuring from base. Make marks at opposite sides of the line
- 90 / 180 / 270 / 360 degrees. Locate bollard by eye and place a long level touching the base of the bollard. Measure the distance from one of the marks on the line to the level and repeat on the opposite side. When the measurements are equal the bollard will be level in that plane. Repeat the process on the other two opposing marks.
You can level them with a simple level, even if they're tapered.
Place the level vertical, with the vial crossways and tangential to the surface of the bollard. It's "leaning back" because of the taper, but because the vial is perpendicular to that, it doesn't affect the level. Repeat at 90=B0 around the bollard to set it on the other axis. This relies on using a level with "barrel" vials rather than "banana" vials (most recent plastic vials, but not glass vials). You'll also get better results if you chalk a couple of axial lines down the bollards first.
You could jig it too, which would be quicker, but I doubt I'd bother for only 5 of them. If you did, attach two levels to do both axes simultaneously.
I assume you have a laser level already (if not...), but these need to be a "flying spot" to be visible outdoors rather than a line projector and those are slow to set up (limited self-levelling capacity) unless you spend 200 quid on it. With a vertical laser line and a chalked bollard you could set them up vertical too, but this really needs two line projectors to set both axes simultaneously. It's also crucial that you place the line projectors so as to point exactly at the central axis of the bollard, or they'll carefully align you skewed. On the whole I think chalking this line onto the bollard would be more accurate than projecting it from a couple of feet away.
The quick trick for hollow bollards (such as lighting poles) is to drop a plumb bob down _inside_ the tube. A cheap LED torch as a plumb bob, a centring dangler made of two crossed, notched sticks, and a cardboard target circle (with a retrieval string!) are all you need. Maybe a mirror too, if they're tall.
I did that for the newel post on our stair rail, although I just rigged something which held the line sufficiently away from the top at the point where I was testing (such that the line wouldn't foul at the base), then ran it round the perimeter at a few different points (in other words not a complete 360-degree 'hat', but the same concept)
It's not like you're suggesting TMH spend thousands on something which is only going to be used once - an adjustable level would come in useful for all sorts of things.
Handrails on stairs and the fall of wastepipes for examples.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.