Completed (almost) Pendulum Level

[tongleh]

Here’s some pictures of the completed pendulum level (almost). For the pictures, I hung the vernier scale on two 1.5 mm drill bits and glued it to the slide, the scale will be mounted using 2mm screws as soon as my 2mm tap arrives. The Pendulum is mounted to the knife edge assembly via a bronze bushing inside a steel tube welded to the top of the pendulum arm, ensuring it hangs true vertically, there is no sideways movement. The knife edge has thumb screws front and rear so I can adjust the distance between the rule and vernier scale (backing them off after adjustment). The vernier scale (in 0.05 increments) is mounted to a slide which can be zeroed via a phillips head screw and tensioning spring; again, there is no movement. Above the rule I mounted a weight as a dampener to reduce swing and ensure the pendulum comes to rest in the same place each time. Every part of the assembly has been cut and re-welded so many times the finish is a bit rough now and quite a bit shorter than it was to start with, but it does the job. To test, I mounted the assembly just in front of the chuck and zeroed the vernier scale. I then moved the assembly to the tailstock end (600mm) and took a reading,. Shimming the front of the tailstock end leg using a 0.05 feeler gauge brought the vernier to the seventh increment (0.35). I carried out this procedure several times and got the same readings each time. My mathematics: the distance between the knife edge and the tip of the vernier scale is 1320 mm and the contacts on the base of the unit have 100mm centres, giving a ratio of 13.2. I then divided 0.35 by 13.2 and got 0.0265151. I never made it to high school so I can’t spell trigonometry, let alone do it; however, the method I worked out seems logical to me. At any rate, 0.0265151 (0.1590906 over the length of the bed) seems reasonable to me and presumably I could get it closer with the right size shims. If you find fault with my math, then I'm happy for you…

[BRADFORD]

I'm impressed by your set up. Looks like it would be very accurate to me.
Have you tried turning something between centres and checked how much taper you have?

[Blu_Rock]

A very nice piece of kit there, well done!

[tongleh]

Some would disagree with the accuracy bit I think; and no, I haven't tested between centres yet, it was pretty accurate before levelling anyway - another day. If I was to make another (and I still might, I've had so much enjoyment from this project), I would change the pendulum to round bar, that would allow a heavier weight and also make it easier to align the rule with the vernier scale. I'd probably also change the knife edge pivot to an underslung design.

[Stustoys]

If you find fault with my math, then I'm happy for you…
I do, but as you appear to think math is a matter of opinion or a personal attack, I'll leave it at that.

Great work though.

Stuart

[Ben Dono]

Just another thought, and I'm not sure if this has been covered yet but you could test the resolution of this setup with shims.
Hopefully this will the resolve the math debate.

Zero your scale, unlock the cam and slide a fine shim under one side and check to see how much the pointer moved. I guess your after maximum swing for the finest shim you have.

[tongleh]

Excellent idea, I'll reglue the vernier and try that. On the other question of turning between centres: I think that would just show the tailstock is out, after all the carriage sits on the same plain (lathe bed) as the tailstock, I think you would have to turn something unsupported on the tailstock end to get a true reading. Anyone? :brava

[tongleh]

For Stuart. All I stated was that I wasn’t that good at mathematics (forget about trigonometry) and as I said: ‘I may be wrong’! I also described how I came by my figures; and, I still think it a perfectly logical method. I will try Ben Dono’s idea, as soon as I have mounted the scale properly. As for ‘I’m happy for you’, well that may have been out of line, life’s a bitch. ain‘t it? :o

[Ueee]

Threads have clearly been crossed here and it is rather confusing for those of us that havnt been following the other thread. The maths made my head hurt a bit too, but bens solution will solve the question.
Yes you need to turn a piece unsupported, maybe 4" long. Personally I would have bought a level......yes I know, I'm normally a why buy when you can make it guy, but not for measuring gear.

[tongleh]

Well, you can buy knurling scissors, die holders, coolant systems and just about every other item we use on a lathe or mill, but most of us have made these items or other items of a similar nature at one time. For me, it's the challenge and of course I enjoy projects of this nature, keeps me out of the pub.:doh:

[Ueee]

I suggest you re-read my post......i did not say why make when you could buy.

[Ben Dono]

I'm always making things that I could have or should have bought. I think we all like the idea of the challenge and lessons we learnt with each project.
I always get a kick out of finding another way. How often are we stuck on something and have to think out side the box to solve the problem.
This project really ticks that box.

The other side of it is we may have eneded up proving why this is not the best path to follow. Still a lot would have been learnt.

I just read over all that and realized I'm spouting the obvious. Sorry guys..

On a side note.. A lot of my projects end up being a new tool or jig etc to make my life in the workshop easier.. Hahaha I feel like I'm chasing my tail sometimes.. I buy tools to make tools to make my life easier in the workshop to make more tools!

[BobL]

On a side note.. A lot of my projects end up being a new tool or jig etc to make my life in the workshop easier.. Hahaha I feel like I'm chasing my tail sometimes.. I buy tools to make tools to make my life easier in the workshop to make more tools!

+1.

My other favourite is when a tool participates in making itself. Like when I made my milling vice/attachment for my lathe - I got it enough of it made where it could use it to hold some round stock and mill a slot in it for a vice handle.

[Ben Dono]

:2tsup: Bob thats awsome! I have not had the pleasure of that yet. I read a lot of gingery's books on machine building. That system played a big part of his construction methods?

[BobL]

:2tsup: Bob thats awsome! I have not had the pleasure of that yet. I read a lot of gingery's books on machine building. That system played a big part of his construction methods?

A couple of other cases where this has happened is my wood work bench.
I built the basic frame and then immediately added the front vice and then used that to make the rest of .

The same happened with my Welding Metal work bench and the welding fume hood.

My favourites are the 2 and 3 mm wide woodworking chisels I made a couple of years back where I prepared blades by grinding bevels on 2 and 3 mm wide pieces of HSS and then sharpened these. Then I turned some handles and used the blades to cut their own handle holes. It worked really well. Now I use these chisels to make handle holes for all sorts of other chisels.

[Stustoys]

I'm certainly no mathematician.
As far as I can tell there is no trig needed.
If the feet are 100mm apart and the column is 1320 high, shimming one foot 0.05mm(I assume its mm as the rest of your measurements are in mm), should move the "pointer" 13.2 times that, 0.66mm now you are only getting about half that. The most likely reason I can think of is that where you have shimmed, the mounting points are more than 100mm apart.

As for how accurate your results are. If slimming one foot 0.05mm and the feet are 100mm apart, 0.05x10 =0.5mm/meter. Now if you get a reading of 0.35 you can get to 1/7th of that, so each 0.05mm on the vernier is equal to 0.07mm/meter.
But as I said I think your mounting point might have been further apart than 100mm if thats the case things get better, if the feet are 200mm apart it halves thing to 0.035mm/meter.

At least thats how I'm seeing it.

Stuart

[BRADFORD]

Excellent idea, I'll reglue the vernier and try that. On the other question of turning between centres: I think that would just show the tailstock is out, after all the carriage sits on the same plain (lathe bed) as the tailstock, I think you would have to turn something unsupported on the tailstock end to get a true reading. Anyone? :brava

This gets bit hard to get my head around, but I think a twist in the lathe bed can cause the tailstock to be out of alignment with the headstock, this will cause a taper in the job being turned. Mind you there are other reasons for turning a taper, mostly to do with the tailstock being out as you have stated. Maybe a better method of testing would be to turn something fairly large and rigid unsupported by the tailstock and then check for taper.
It occurs to me that the lathe bed does not need to be level, but it does need to be exctly the same at each end ie no twist, the instrument you have designed would be excellent at achieving this.
Your next project could be to work out a method for headstock/tailstock alignment.:U

[scottyd]

A twisted bed will behave like a misaligned tailstock. However, you can check with just the tailstock. With a long test piece mounted between centres and with the tailstock right at the end of the bed, calibrate the tailstock until its bang on. Then mount a shorter test piece, say half the length of bed this time, and measure how paralell it is with the bed. If there is any variation, itll be down to the bed alone. A bed with twist will only be able to be fixed with a tailstock adjustment at any one point along the bed. A straight bed will only need the tailstock to be set once, and itll be right all the time.

[tongleh]

Ok, some numbers: The pendulum is exactly 1315 mm long, from the bottom of knife edge Vs to the top of vernier scale. The bed contacts are 80mm apart inside and 110 outside, I have used 100mm as a datum, as that is the point where I put the edge of the feeler. I used a 0.10 mm feeler as the 0.05 is under the bed. I zeroed the vernier, released the clamp and placed a 0.10mm feeler underneath one side at 100mm from the far edge, the reading coming up at 1.7 mm. I did this several times and replicated the results each time (within 0.05mm). Using my system: 1.7mm/13.15 = 0.1292775mm. Not 0.10 as I expected but .0292775 out. Make what you will of these numbers, but it is fiddly gizmo. I think a round pendulum with a much heavier weight should make it less so and the vernier adjustment screw needs to have a finer thread, it is a pain to zero, You also need an eye loupe to read it: if you’re just using a magnifying glass, it becomes hard to tell whether it’s zeroed on 0 or 9.

[MuellerNick]

I really hurts to have to read that bent math.
I don't want to be banned, so I try to calm down.

You don't need much math to get that right. There are a few things you have to understand and accept:
Machine levels do measure in mm/m. That is: If the scale is in mm and the level is resting on something that is 1 m long, and you lift one end 1 mm, you will get a reading of one division.
Now if you fix that slanted piece under measurement and leave the level on it and cut off 90 cm of that piece, the reading on the level will still be the same.
Conclusion: The length of the base plays no role!
Understand and accept that.

If your pendulum (that acts like a level being vertical) is one meter long and the resolution of your vernier is 0.05 mm you have exactly an equivalent of a level with a resolution of 0.05mm/m.
You can increase the resoltion by making the pendulum longer. With 2m and the vernier's resolution of 0.05 mm, you can read to 0.025 mm / m.
If you want to get close to a precsion level that has 0.01 mm / m, your pendulum has to be 5 m long. A bit un-handy, but I don't know your shed. :wink:


Nick

[Graziano]

I reckon you could stick a front surface mirror up at the pivot end of the pendulum mounted at 45 degrees and shine a fixed laser pointer vertically up at it to get a horizontal light beam running the length of the shed at a fixed target to get an increase in beam deflection and giving a long, horizontal "virtual pointer". The 5 metre+ long pendulum arm would become possible then (or however long your shed is, or even out the window, across the street and on the side of the neighbour's house.

Tongleh, that looks like a very neat project you have there! :2tsup:.

[Steamwhisperer]

If you were to place a metre long piece across the bed hooking on the far side and the excess sticking out where the operator normally stands then made the pendulum base the same length but with the pendulum support in the middle of the ways, then when the bed was twisted by adjustment, wouldn't the swing of the pendulum be amplified. or am I absolutely in a paralell world:)

Phil

[Graziano]

If you were to place a metre long piece across the bed hooking on the far side and the excess sticking out where the operator normally stands then made the pendulum base the same length but with the pendulum support in the middle of the ways, then when the bed was twisted by adjustment, wouldn't the swing of the pendulum be amplified. or am I absolutely in a paralell world:)

Phil


The amount of up-down movement at the end of the long horizontal base would increase at the end of the base (which was what I expect a pendulum steered light beam would do) but the angle and movement of the pendulum relative to the base would still be the same (unless I'm misunderstanding how the thing works).

[MuellerNick]

wouldn't the swing of the pendulum be amplified. or am I absolutely in a paralell world

If you have a level that is 1 m long and you saw off half a metre, does that change the resolution?
If so, there must be a mysterious space warp that changes the level (with the bubble in) itself


Nick

[tongleh]

I think I like your idea Graziano, sounds neat?

Steamwhisperer, I like the sound of that, can you explain that in more detail?

Muellernick, if reading this thread hurts your head and your having trouble staying calm, in all seriousness I would like to offer this solution: stop reading this thread.

[MuellerNick]

in all seriousness I would like to offer this solution: stop reading this thread.

If the purpose of this forum is to spread stubborn nonsense and not to educate people, I'm already gone!


Nick

[Steamwhisperer]

If you have a level that is 1 m long and you saw off half a metre, does that change the resolution?
If so, there must be a mysterious space warp that changes the level (with the bubble in) itself


Nick

It's basic physics. Moments of leverage. By increasing the length of the support and twisting the bed, the movement will be amplified at the end of the extension which will be then transferred to the extended pendulum base. Think of the old lever indicators. Moments of leverage amplify.

Phil

[Ueee]

To add to what Mark said about Phils idea, you are not measuring distance or the thickness of your shims. You are measuring angle from a known plane. It doesn't matter if it is 1deg over 10 meters or 1 deg over 10mm, the error is still the same.

I've just notice Phil posted as i am typing, you are adding leverage, but all you are changing is the amount of shimming required to move the same angle.

[Steamwhisperer]

To add to what Mark said about Phils idea, you are not measuring distance or the thickness of your shims. You are measuring angle from a known plane. It doesn't matter if it is 1deg over 10 meters or 1 deg over 10mm, the error is still the same.

I've just notice Phil posted as i am typing, you are adding leverage, but all you are changing is the amount of shimming required to move the same angle.

Damn you Ewan. Now I have to satisfy my curiosity and try my theory. Of course I doubt I will be allowed out in the shed. Something about fathers day or some such thing tomorrow. My son is taking me to see the saints slaughter Carlton.

Phil

[Ueee]

Damn you Ewan. Now I have to satisfy my curiosity and try my theory. Of course I doubt I will be allowed out in the shed. Something about fathers day or some such thing tomorrow. My son is taking me to see the saints slaughter Carlton.

Phil

Please do....I'm not 100% sure. Is it worth going to the game? We already know the outcome. Went to lunch last Sunday with my sister and brother I-L. He had the courage to wear a blues jumper......
Fathers day, doesn't that mean dad gets to do what he wants?

[Graziano]

I think I like your idea Graziano, sounds neat?

I had a few thoughts about this, if the laser is not attached to the pendulum, only shining on a mirror mounted on the pendulum, then you should get a doubling of the angle of deflection, i.e. the pendulum moves one degree but the beam will reflect twice the angle. if you could arrange a wide fixed mirror beside the fixed laser so the beam goes back and forth say 5-10 times you'd get proportionately more angular reflection with each beam bounce. Should be worth a few experiments but I have to get the roof on the shed extension before the wet season hits and evict another roof dwelling python etc etc.

I hope Nick still hangs around here after that bit of "robust discussion":rolleyes:, but I suspect the only problem is the small differences between Australian culture and German being lost via the keyboard. I'd imagine there's just a delay between Nick stating the facts and coming to understand them (at least there is for me personally).

[BobL]

I had a few thoughts about this, if the laser is not attached to the pendulum, only shining on a mirror mounted on the pendulum, then you should get a doubling of the angle of deflection, i.e. the pendulum moves one degree but the beam will reflect twice the angle. if you could arrange a wide fixed mirror beside the fixed laser so the beam goes back and forth say 5-10 times you'd get proportionately more angular reflection with each beam bounce. Should be worth a few experiments . . . . .

I suggested a laser back in the other thread. One problem with lasers is getting a fine enough spot so some exit and receiving optics may be needed - not always as easy as it might seem.

[Graziano]

I suggested a laser back in the other thread. One problem with lasers is getting a fine enough spot so some exit and receiving optics may be needed - not always as easy as it might seem.

Bob, which thread was that one?, I've only just got back online after a month or so break without ADSL at home. I've had good luck with fax machine condenser lenses and another one is the small value (tight focus) eyepieces out of telescopes, both focus tightly to a small point so they work well with those Ebay red laser diodes intended for DVD burners when used in reverse.

[BobL]

Bob, which thread was that one?,
This one. (http://www.woodworkforums.com/f65/pendulum-level-157496/)


I've only just got back online after a month or so break without ADSL at home. I've had good luck with fax machine condenser lenses and another one is the small value (tight focus) eyepieces out of telescopes, both focus tightly to a small point so they work well with those Ebay red laser diodes intended for DVD burners.

Sure I agree but a simple laser reflector still needs a longish beam to just match a physical vernier? The only way I've seen it beat a vernier over a few metres is with a photo-detector and beam profile analysis or of course using an interferometer.

Did you finish your turntable grinder?

[Machtool]

Muellernick, if reading this thread hurts your head and your having trouble staying calm, in all seriousness I would like to offer this solution: stop reading this thread.
I appreciate that you have quite a bit of time and effort invested in this, and more power to you for trying. But you seem to take it very personal, when there's some critic. Critic doesn't automatically mean criticism.

Apart from a typo Nicks figures are correct. If that were me, I'd use a level with a 0,05mm per metre resolution, exactly as he said. If you had that level sitting on a 1 metre long straight edge, and shovelled a 0.05mm shim under one end of the 1 metre long straight edge, it will change by 1 division.

In a vertical pendulum application, with a pendulum 1 metre long, the math is the same. You would expect the pendulum to move 0.05mm.

Yours being a longer pendulum at 1315 mm that would be 65.75 micron or 0.065xx to get the same resolution as 0.05/m. I'm not seeing that resolution in your tests. And that's not a personal criticism, just an observation.

This is coming from some one that uses pendulum devices, but with a piano wire, plumb bob, coffee can full of 220 gear oil to suppress, and an optical scope.

Phil.

[Graziano]

This one. (http://www.woodworkforums.com/f65/pendulum-level-157496/)



Sure I agree but a simple laser reflector still needs a longish distance to just match a physical vernier? The only way I've seen it beat a vernier over a few metres is with a photo-detector and beam profile analysis or of course using an interferometer.

Well say you have a beam length of 5.729 metres, that would give a circle with a circumference of 36 metres or 10 cm per degree. Assuming a 2mm diameter laser dot that would be a resolution of 1/50th of a degree with just a ruler. If the laser is fixed and the mirror moves with the pendulum then it would be 100ths of a degree over that distance. More bounces between a fixed mirror at 5.729 metres and the pendulum mirror would be even better resolution albeit over a narrow range of angle.



Did you finish your turntable grinder?

Haha, the "Spurret" has three 1.75 Hp DC motors now and a prototype PWM/IGBT based speed controller now, but that's another topic altogether, maybe once it's complete.

[BobL]

Well say you have a beam length of 5.729 metres, . . . .

I guess that's what I call a longish distance. :)

How about some update pics of the grinder in your original thread?

[Graziano]

How about some update pics of the grinder in your original thread?

What don't you believe me?:)

[tongleh]

I'm afraid you've misunderstood my post, I was commenting on Mueler's getting a headache and trying to stay calm quote. It would seem to me that if you know banging your head on a wall gives you a headache then the best way to avoid a headache is to not bang your your head on the wall in the first place, simple logic, offered with a little tongue in cheek. Personally, I think the time might be just right to finish this thread, before anyone else gets bent out of shape, I'm already bent out of shape apparently, so it won't make any difference to me...:~

[Bryan]

I thought about the laser too, but the problem is the target. If you move the device from one end of the bed to the other (which is kinda the point), you need a separate target right? And how do you get your targets dead level? Or does the scaling mean a carpenter's level will do for that?

[Ben Dono]

I really hurts to have to read that bent math.
I don't want to be banned, so I try to calm down.

You don't need much math to get that right. There are a few things you have to understand and accept:
Machine levels do measure in mm/m. That is: If the scale is in mm and the level is resting on something that is 1 m long, and you lift one end 1 mm, you will get a reading of one division.
Now if you fix that slanted piece under measurement and leave the level on it and cut off 90 cm of that piece, the reading on the level will still be the same.
Conclusion: The length of the base plays no role!
Understand and accept that.

If your pendulum (that acts like a level being vertical) is one meter long and the resolution of your vernier is 0.05 mm you have exactly an equivalent of a level with a resolution of 0.05mm/m.
You can increase the resoltion by making the pendulum longer. With 2m and the vernier's resolution of 0.05 mm, you can read to 0.025 mm / m.
If you want to get close to a precsion level that has 0.01 mm / m, your pendulum has to be 5 m long. A bit un-handy, but I don't know your shed. :wink:

Nick

I was about to jump all over that but looks like everyone got in before me!

Don't get me wrong! I love Germans. They are very efficient and matter of fact kind of people. Damn good tools, food and beer... But when anyone makes an 'absolute' statement to an Aussie that we are wrong... Well it just gets my back up! there is a 'gentle art of conversation' too often lost these days.

To be fair, I get your point. Where the rig rides on the lathe bed is the fixed distance, But that distance is important. Maths can have everything to do with it or none at all. You can use both trig and ratios to work this out. Grab a spirit lever and put a block under one end. Move it from end to end and you will see the difference.
On a side note Nick, I have never met a German who like Aussie meat pies? Why is that?

[Ben Dono]

I thought about the laser too, but the problem is the target. If you move the device from one end of the bed to the other (which is kinda the point), you need a separate target right? And how do you get your targets dead level? Or does the scaling mean a carpenter's level will do for that?

I got all excited when the talk about laser pointers came up. But your right about the target. I can't think of a way to make it reference back to the lathe.

Some lasers throw a line rather than a point. Maybe that could solve the reference issue.
Start at the headstock, set the laser to throw a parallel line with the lathe bed on the ceiling and mark that line. Move the rig to the tailstock end. The laser line should line up with your marked line on the ceiling to remove bed twist... I think?

If you have high ceilings this might work.

Hahaha but the laser lever probably costs more than the engineers level.
I'm chasing my tail again.

[Graziano]

I'm afraid you've misunderstood my post, I was commenting on Mueler's getting a headache and trying to stay calm quote. It would seem to me that if you know banging your head on a wall gives you a headache then the best way to avoid a headache is to not bang your your head on the wall in the first place, simple logic, offered with a little tongue in cheek. Personally, I think the time might be just right to finish this thread, before anyone else gets bent out of shape, I'm already bent out of shape apparently, so it won't make any difference to me...:~

Ahh well I still reckon it's a pretty cool project even if there's no point in telling you to "Get Bent" anymore :roll:. Without stereotyping countries I know a local machinist here from Germany over 30 years ago who I never discuss anything with too much as he's easily excitable by us dumb people.

Bryan and Ben Dono: two solutions to the laser target problem I can think of off-hand would be to 1: have a second fixed laser clamped near the moving mirror with a Line lens projecting a reference line fixed relative to the laser beam or 2: make the moving mirror beam go up and down the length of the pendulum 5-10 times with a fixed mirror at the bottom bounce back at the moving mirror to get the 5.729 metres path length and project onto a mounted ruler target attached to the unit. This would have a much increased angular deflection due to hitting the moving mirror multiple times so the pathe could be shorter too.

Ben: a lot of Aussies don't like meat pies too, I can't cop the artificial pastry shortening that is literally indigestible to save butter costs (Brisbane pies were worst imo). There was a local pie bakery right next door to a spray painting shop locally, they had the pies out on trestle tables cooling where they could catch the latest 2 pack car finishes. I used to avoid that brand after seeing that.

[BobL]

What don't you believe me?:)

Of course I believe you. But I like your pictures and your solutions and every time I look at them I learn something.

You might need to use a diagram to help explain your laser solutions.

[Graziano]

Of course I believe you. But I like your pictures and your solutions and every time I look at them I learn something.

Ahh sorry, I have to stop posting round midnight, I get irritable too easily these days. Right now without too much thread hijacking: I need to fix the Bantam cross slide screw and nut to finish the spurret, so I'm making a 9/16" 5 tpi left hand double start acme screw and nut. Fifth time's the charm!

Diagram as requested, hopefully it make sense to someone and not just me:2tsup::

http://www.woodworkforums.com/attachment.php?attachmentid=222088&stc=1&d=1346546686

[Graziano]

Apart from a typo Nicks figures are correct. If that were me, I'd use a level with a 0,05mm per metre resolution, exactly as he said. If you had that level sitting on a 1 metre long straight edge, and shovelled a 0.05mm shim under one end of the 1 metre long straight edge, it will change by 1 division.

Phil.


So Phil, for that resolution of spirit level you'd see an angular resolution of TAN^-1(0.05/1000)=0.00286 degrees?. Kind of renders mucking about lasers and reflectors almost obsolete without a long folded path to resolve 1000ths of a degree :o.

Edit, actually it would be sin^-1(0.05/1000)=0.028647 degrees, sine=opposite/hypotenuse not tan=opposite/adjacent.

[tongleh]

I don't know anything about lasers, but surely the point would be too large to measure in the increments being talked about here?

[Graziano]

I don't know anything about lasers, but surely the point would be too large to measure in the increments being talked about here?

Not if you are measuring it against a large diameter circle, iow a long beam path: that's why I picked a distance of 5.729 metres, at that distance, one degree of angle is equivalent to 10 centimetres of the circle's circumference, i.e. 1/360th of a 36 metre circumference circle.

That's just if you have the laser mounted to the moving pendulum, if you have the laser shining on a moving mirror on the pendulum, then the movement of the beam doubles compared to a laser just mounted on the pendulum. Mirrors reflect so the angle of incidence equals the angle of reflection, this means if the mirror rotates one degree then the laser beam shining on it will bend two degrees. If you ran the beam between to mirror strips one fixed and one on the pendulum pivot say three times, then one degree mirror rotation would reflect the beam 2 degrees on the first bounce, 4 degrees on the second, 8 degrees on the third bounce.

That means with a beam length of 5.729 metres bouncing three times over two mirrors 143cm apart would move the laser dot 80cm for a one degree rotation. so if your dot is 2mm diameter you could resolve 1/400th of a degree with a millimetre ruler.

[scottyd]

Has anyone considered the use of diffraction around a sharp edge to amplify the motion of the laser? The diffraction pattern moves much faster than the laser does. One could set the "centre" of the level for when the diffraction pattern matches a predetermined set of marks. You could also bounce the light between a pair of mirrors a number of times before meeting your diffractive edge. Two mirrors placed 572.9mm apart with the laser arranged to bounce ten times will give you your 5.7 meter length. You could make a slightly cumbersome but pretty cost effective level.

[Bryan]

I got all excited when the talk about laser pointers came up. But your right about the target. I can't think of a way to make it reference back to the lathe.


Ben I'm way behind some of these guys with their smoke & mirrors, but the thing that dawned on me is that the pendulum always points down, so a laser attached to that will always point to the same plane, and so provide a reference (target). If you then stick another laser on the base - which sits on the ways - and measure the distance between the two points on the wall, you're set like a jelly. I know Mark Graziano alluded to that in post 45, I just thought I'd expand a little in case it helps the slow learners - like me! :)

[MuellerNick]

But when anyone makes an 'absolute' statement to an Aussie that we are wrong... Well it just gets my back up! there is a 'gentle art of conversation' too often lost these days.

I didn't say that Aussies are wrong. Nor that they are always wrong, not even for genetic reasons. I said that this specific math is wrong.

When I once was in OZ, I didn't have the impression that Aussies are pussies like the Americans that immediately start crying whenever you critic something. I had the impression that they are robust, direct and open minded people. And VERY kind!


Nick

[simonl]

I didn't say that Aussies are wrong. Nor that they are always wrong, not even for genetic reasons. I said that this specific math is wrong.

When I once was in OZ, I didn't have the impression that Aussies are pussies like the Americans that immediately start crying whenever you critic something. I had the impression that they are robust, direct and open minded people. And VERY kind!

Nick

Hi Grumpy Nick. I'm robust. Stay with us buddy! :U

........ even if we do do your head in and we're #### at maths! :doh:

Cheers mate!

Going to have a BEX and a lie down. Happy father's day to me and eveyone else!

Simon

[MuellerNick]

Hi Grumpy Nick. I'm robust.

The Aussies must be robust. From what I have seen and learned in OZ. The way they drink!
And from what I have seen at the Oktoberfest Munich. OMG! But I don't think they are all combat drinkers. :D

It's OK to call me "grumpy". From time to time. :D

OK, back to topic ...


Nick

[Ben Dono]

The Aussies must be robust. From what I have seen and learned in OZ. The way they drink!
And from what I have seen at the Oktoberfest Munich. OMG! But I don't think they are all combat drinkers. :D

It's OK to call me "grumpy". From time to time. :D

OK, back to topic ...


Nick

Sorry Nicko! I got a little hot headed. Nothing worse than a poorly behaved Aussie! :B
I I'm getting the feeling a pendulum style level if kept simple in halfway between a good carpenters level and forking out for an engineers level.

I think when I get around to it, will just make a jig that sits on the ways with a laser line (not a point style) projected on the ceiling. No pendulum or any moving parts. Mark that line and reposition it at the other end and check the difference. I'm lucky as I have about 3m above the lathe bed. Will let everyone know how it goes.

[QC Inspector]

There is another way to measure using a laser and that would be one of the Faro Laser Trackers. It sends a laser beam to a reflector which sends the beam back to the sending unit and measures the distance. In this application you would attach the reflector to the pendulum and measure the distance the pendulum moves to .0001" or .00254mm.

The thing is that if you do have access to a Faro Tracker you could just take your readings directly off the bed of the lathe for level, twist, etc., and skip the pendulum altogether. :roll:

FARO Laser Tracker - Home (http://www.faro.com/laser-tracker/us)

The Worlds Most Accurate Large Volume Laser Tracker: FARO® Laser Tracker ION - YouTube

Note: I don't work for Faro so don't get a kickback if you get one for your shed. I get to use one at work on occasion though. :U

Pete

[tongleh]

"I'm getting the feeling a pendulum style level if kept simple is halfway between a good carpenters level and forking out for an engineers level."

The idea in the first place!

[Ben Dono]

"I'm getting the feeling a pendulum style level if kept simple is halfway between a good carpenters level and forking out for an engineers level."

The idea in the first place!

Did you try out the shim test after you zeroed the scales yet? I just went through the posts in did not see a report on it.

[tongleh]

Yes I did, but the results I posted recieved quite a bit of negativity: Don't think I'll bother with posting anymore!