Thread: Pendulum Level

I don't see how you could get the claimed 0.0185 mm / m with a vernier. It's getting difficult below 0.05 mm to read. Also, both graduations have to be very close together, not to say you will have friction making the setup useless.

A way out of that misery would be a digital caliper. They work contactless. Canibalize a cheap one. Cut off about 30 mm of the beam and mount it to the pendulum. The part with the display goes to the non-moving part of your contraption.
Still you will have to precisely adjust the instrument so that the gap is minimal (a few 1/10 of an mm work) and you never have parts that rub on each other.


Nick

Well, shiver me timbers, that worked. Over 8 divisions it was spot on. Tomorow I'll mark up the full length and measure that up (wife won't let me work out in the shed at night - don't know why). Rather surprised the cross slide graduations are so accurate. Good idea, thanks for that.

I'm still struggling with the math behind the 0.0185mm number. If you are only reading to the nearest 0.25mm. For the 0.25mm graduations to be "0.0185mm a meter" apart, wouldnt you need a pendulum 13m long?
Stuart

Originally Posted by Stustoys

I'm still struggling with the math behind the 0.0185mm number. If you are only reading to the nearest 0.25mm. For the 0.25mm graduations to be "0.0185mm a meter" apart, wouldnt you need a pendulum 13m long?
Stuart

Hi Stuart,

Does your mind ever go to sleep?!

Simon

Don't get me wrong I like the idea, I just think we are talking about different things with the 0.0185mm number. The math in it the video talked about checking to 0.005" a foot, with graduations 1/32 apart he needed a 74inch pendulum. For the younguns out there and so we are using one system I make that 0.417mm a meter for a 0.79 graduation with a 1880mm pendulum. I dont think tongleh's pendulum is that long but if it was as he is reading to 0.25mm the graduations would be 0.139mm a meter apart.

I think

Originally Posted by simonl

Does your mind ever go to sleep?!

Only when I need it . Like currently, it cant even work out resistors needed for voltage drop in a simple curcuit! I used to know this stuff, it seems to have gone missing.

Stuart

If my brain were an imaginary friend - The Oatmeal (Crude content.)

Well, that's by my calculations (and I'm not a mathematician). I may be wrong, it wouldn't be the first time. I'm enjoying fooling around with it. Anyway, end of thread....

Originally Posted by tongleh

Well, shiver me timbers, that worked. Over 8 divisions it was spot on. Tomorow I'll mark up the full length and measure that up (wife won't let me work out in the shed at night - don't know why). Rather surprised the cross slide graduations are so accurate. Good idea, thanks for that.

Good stuff. Can you show us the final product?

Originally Posted by tongleh

I'm not a mathematician

Nor am I, not by a long shot. As I said I am trying to get my head around it and maybe we mean different things by the numbers.

Originally Posted by tongleh

I'm enjoying fooling around with it.

As I and I'm sure others have enjoyed watching. If my comments have been taken as something against the idea or your work then I'm sorry as that was not the intent.

Stuart

Originally Posted by Stustoys

Nor am I, not by a long shot. As I said I am trying to get my head around it and maybe we mean different things by the numbers.


As I and I'm sure others have enjoyed watching. If my comments have been taken as something against the idea or your work then I'm sorry as that was not the intent.

Stuart

I certainly didn't read that way Stuart.

Hi Tongleh, once again, thanks for sharing. Well done on the project!

Simon

Originally Posted by tongleh

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.

Maybe a stiff scribe in the mill. Don't turn it on, just use the DRO or scales to do the dividing for you. Move the scale under the scribe to scratch a mark.

An old boring bar with a modified tip should do it.

Thanks for working this one out. I was sure this old-time method had some merit.
I do like the idea of a DRO scales. But unless you have some to cannibalize, a level would probably work out cheaper.
What about magnetic dampening on the scales?

Unfortunately I don't have a mill and the graduations on the lathe cross slide hand wheel started going off after 8 or so graduations so I canabalized an old vernier I had. So far I've changed the top mount to a knife edge balance hinge with adjusters for moving it back and forward, there is also a plain bearing mount at the top where the pendulum joins the knife edge allowing the pendulum to hang correctly (vertical), regardless of column angle. I've mounted the ruler section on the bottom of the pendulum and added a S/S weight to slow down the pendulum. I've also made a sliding adjuster on the base to mount the vernier scale to for zeroing it in and the base now has a quick release mechanism from a bike seat post. I've tried a magnetic dampener (by accident) to the lower section of the pendulum but that didn't work at all, adding the weight on the bottom worked reasonably well, although the slightest movement, or simply breathing on it, starts it swinging again, a heavier weight should work well here. Painting day today and then wait a few weeks for the 2mm tap to turn up so I can mount the vernier scale properly. I've modified and changed every section of this project, over and over again, making slight improvements as I've progressed, this has been a very enjoyable project so far, I'll be sorry to finish.

Haha you really grabbed this project with both both hands! Good on you! I'm glad I stumbled across this YouTube video. Your doing a lot of leg work for everyone else and it's well documented. Thanks mate!

I'm surprised you found the magnetic dampener not to help. I have an old powder scale that is super sensitive with a magnet on each side of the the boom. I found it excellent at bringing the scale to a faster stop point. It too has a blade as a pivot point.

Let us all know how it worked out.

Did anyone come up with a definitive answer to the math and final post hight in comparison to an engineers level? I read all the posts a few times and got lost along the way.

I have posted a new thread under 'Completed (almost) Pendulum level'. Along with some pictures of the completed unit. It also answers the question on my mathematics.