Thread: Pendulum Level

Here are some pics of my pendulum level I've just finished. Now some of you may laugh, but it's accurate to within .0185 mm and the results are able to be replicated. Made from just some bits of steel lying around and a piece of S/S rule it was certainly cheaper than a $160 machinists level. I don't have the height in the shed to make it more accurate, but it's close enough for me.

What have you used for the pivot at the top?
It would need to be quite friction free.

tongleh, I can't see why anybody would laugh, it's a great job and a handy gadget.

Close enough to 1/2 a thou over 6 inches is pretty bloody good.

I'd make one myself except the trigawhottomy would do my head in

Originally Posted by tongleh

but it's accurate to within .0185 mm

I dont understand your numbers. 0.0185mm in ??

How tall is it? I cant see the top in the pictures.

Originally Posted by tongleh

certainly cheaper than a $160 machinists level

And certainly better if the $160 level doesnt have a flat base.(like mine used to be)

Stuart

I had never heard of a pendulum level but it makes sense to me now you mention it. I really interested in the concept. I better start googleing! Thanks for sharing with us.

Simon

The hinge point is just a 6mm rod welded to the top of the pendulum and inserted into a 6mm hole at the top of the upright. Friction is not a problem, after mounting, it continues to swing for at least a minute or two, the slightest bump and it starts swinging again. I did toy with the idea of using a bearing or a knife edge hinge, but I think it would take all day for it to stop swinging using the bearing and keeping the pendulum from twisting side to side would require more thought than I was willing to put in. There is a guide rail at the back of the mounting apparatus to ensure it is square to the bed, if not the readings will be out. It also has a quick connect/disconnect system similar to the tailstock mount, minus the cam, although the original I made had a cam lock from a bicycle wheel. This pendulum level is just a copy of the plumb bob level, with a pendulum substituted for the string line, as posted in a previous thread. The math used to work out the discrepancies is the same, coming up at .0185 mm over the length of the bed (600mm). I tested the theory on a rough one I tacked together quickly, it worked so well I made a better one.

What about adding a laser pointer and a small mirror to reflect the image across the shed?

Just kidding - great job - I like it!

I'm going to try and make the pointer sharper today, even with a loupe it's difficult to read under .5 of a mm. When I checked the yesterday it was reading (what looked like) well under.25 mm, Unfortunately I don't think there is a rule available that is marked in .25mm increments or less. The obvious option is to make the upright longer and cut a hole in the shed roof?

Originally Posted by tongleh

Unfortunately I don't think there is a rule available that is marked in .25mm increments or less.

What about attaching a vernier scale to the end of the pointer?

Here's some pics of a new improved pointer. I've welded a clamp on the end to take a pin and angled the rule a little for easier reading; unfortunately, I filed the groove for the pin a little off, so it's not sitting quite square but it still gives a good reading with a loupe. It's working quite well now so I'll try to straighten up the groove and neaten it up a little, but I think that should do it. I gave some thought to a vernier, but thought why ruin a perfectly good vernier, and of course, pins are quite cheap.
.

Originally Posted by tongleh

I gave some thought to a vernier, but thought why ruin a perfectly good vernier, and of course, pins are quite cheap.
.

There is no need to ruin anything. It is very easy to rule up your own vernier scale just take the distance of 9 or 90 divisions of your current scale and mark a piece of steel with 10 divisions within that distance.

If you can find an inch rule marked in 100th's, that will give you 0.254mm per division.

Michael

I like it. Very interesting concept.

Looks to me like that would be very accurate.
Tried the plumb bob on mine, lot of mucking about, but could not get an accurate enough reading, think I will give your method a try.
You have made a huge improvement on the original plumb bob concept.

Here's a mock up of a vernier measurement system I made up for the pendulum level today. The top section is a S/S rule and the bottom section is piece of ali I marked off against the vernier using an eye loupe and a sharp blade. I tried a number of times, but just couldn't get the lines spot on, Unfortunately, no matter how carefull I was, some of the lines came out just a smidgin off. I also tried marking the graduations using a method employing a compass, but that didn't come out too well either. Unless someone has any ideas on how to mark off the graduations accurately, I think I'm going to have to buy a cheap vernier and canibalise it.