Optical Elevator

Or a Laboratory Jack? For some time now I’ve thought that a Lab Jack would come in useful for desk top photography projects. In fact I’ve seen some in use on the net for Macro photography. Lab Jacks look pretty flimsy but are quite affordable, often in the £15 to £30 range for a 100mm model. Then you get the top of the range Optical Elevator, purpose built bits of precision at often eye watering prices. I’m now wondering if I should make my own, possibly something half way between the two. Have any of you made anything like this?

Laboratory Jack.

Optical Elevator.

Some of them are quite complex.

I have one like your first illustration, Vic … and the build-quality is dire

… It’s in pieces at the moment, waiting for me to gather enough enthusiasm to ream all the holes to an appropriate size.

Likelihood is that I won’t ever bother

I have a bigger, and much better, table available [see edit] … and a wide assortment of smaller devices.

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I suggest you think carefully about what size of platform you actually need

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Excuse the cheap pun, but: that blue one is “jack of all trades and master of none’

MichaelG.

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Edit: __ have a look here 

https://www.model-engineer.co.uk/forums/postings.asp?th=184518

Edited By Michael Gilligan on 20/09/2023 10:02:47

I bought one like the blue one for use at work. It was only for putting a dumpy level on to raise it off the floor to the level of a benchmark on a large fabrication and for that it worked fine. As this use did not require that the platform be level or able to take large loads or stay parallel to the base at all times I was happy to buy the cheapest off the shelf item available. The cost of designing and making something to suit in a factory that had hourly cost rates going from £40/hour upwards meant off the shelf was the best option.

Martin C

Thank you very much for your comments Michael, you’ve confirmed my fears. I think the 100mm platform is a little too small. I’ve seen a company on eBay selling laser cut alloy squares in 100, 125, 150 and 200mm in various thicknesses. I believe the 125mm would be ideal for my purpose. At about £22 for a pair in 8mm thick this could be a good start for a home project. I expect I’d need to spend another £20 or £30 for some other bits and pieces for the build. Like many folks I have a long list of jobs to do and I need to come up with as simple as possible design and come up with a drawing. These two don’t look too daunting. Neither are that expensive but the first one is too small and the other is not available for delivery to the UK.

I noticed that with the inexpensive Lab Jacks they have a combined left and right hand thread on the adjuster. The higher you raise the platform the further the knob sticks out. The other units I’ve posted seem to have a fixed knob so can I assume it’s just a conventional thread? Sadly I can’t see from the pictures.

+1 for what Micheal says about the blue one. Even the good versions are pretty poor and quite unable to lift any sort of load with sensible stability.

For best behaviour the load needs to be in-line with the cross arm centre pivots and no wider than the end arm span at the chosen lift. If it's a pointing or sighting thing the axis should run sideways rather than longitudinally. Used like that the thing is generally adequately stable once set but what happens during elevation tends to be inconsistent.

Realistically precision behaviour is asking too much of the concept. However carefully fitted the holes are. It's basically a load stabilised system but it's not really strong enough to take the load it needs to achieve proper stability.

For DIY best to copy the bottom one. The single piece nature of the pivoting "hinge" arms gives you the best chance of combining positive alignment with nominal zero play in the joints. The ones with a multitude of separate arms with sliding rods for alignment require things to be made to very close tolerances if the end result is not to prove excessively wobbly.

The third variety down looks good and has a minimal parts count but there are issues with the sliding block and plate that stop it from tilting. Had a couple like that made by a respected optical lab equipment maker in the lab at RARDE / DERA / DRA and they just didn't work very well. Certainly the last ones out of the cupboard and first ones on the loan list. As I recall matters the bottom slide assembly was the culprit.

Clive

I quite like the arrangement of the last (fifth) one. The way that the extra set of pivoting legs restrains the table in the second axis with fewer parts than the secong and third ones.

Still complex, but clever.

I do like the second and third idea with the double scissor assembly as this will give the best stability when fully raise unlike the cheap blue one where the scissor assembly ends up to one side

Mark

There is complexity and there is complexity!

If I recall correctly from the ones I've seen of that type only uses three each of two styles of arm with all the pivots machined integrally. So given a decent set uplifts probably relatively easy to machine and get all the pivots nice fitting and in the right place.

The other styles generally have rather more parts, albeit simpler, but tolerance requirements will still be similar.

I suspect that when you get down to it machining and assmbly time will be similar.

Clive