The Lemon Fool

… if it even exists. I’m sure I remember seeing them sometime in the dim and distant past but maybe I’m imagining it.

I’m trying - and failing - to find a bolt that is essentially a miniature scissor jack something like the following image of a jack that I just found on the internet simply to illustrate this post - https://www.chegg.com/homework-help/que ... -q44935168

I want to build a small contraption which is essentially a wooden sandwich where the “bread” is 2 wooden sheets (plates) separated by probably 4 of such bolts so that I can slide it under something and then open the bolts so that the plates move apart to contact the floor ant the bottom of the object it’s underneath. The challenge is that in its closed (most compact) configuration it can be no more than 7cm high including the thickness of the 2 plates so that means the bolts - or whatever mechanism I end up designing for the “filling” in my sandwich - can’t be more than about 5cm high when closed and ideally smaller since I would prefer to use thicker wood to maximise strength if I have the space to do so.

I have come up with an idea for a home made mechanism but it would be far simpler to find an off-the-shelf part that I could use but so far quite a lot of internet searching hasn’t come up with anything.

- Julian

Julian wrote:I have come up with an idea for a home made mechanism but it would be far simpler to find an off-the-shelf part that I could use...

Not what you are asking for, but have you considered something like this? They come in all shapes and sizes.

Chris

Julian wrote:I want to build a small contraption which is essentially a wooden sandwich where the “bread” is 2 wooden sheets (plates) separated by probably 4 of such bolts so that I can slide it under something and then open the bolts so that the plates move apart to contact the floor ant the bottom of the object it’s underneath.

Mmm, what about one or more of these threaded feet with a long nut on it.
Does that enable you to lift whatever it is to the point where you can get an actual scissor jack under there?

V8

Something like one of these maybe:

https://www.ebay.co.uk/itm/203479708018

What weight do you want yo lift ?


https://www.amazon.co.uk/DUEBEL-Scissor ... YXRm&psc=1

A search for miniature scissor jack gives a number of hits.

Something like this?

https://www.amazon.com/Toggle-Anchors-S ... r=8-2&th=1


Also you did not specify how far you need to lift and how often. There will be a big difference between something that goes up and down like an elevator and a one off lift into position.

Julian wrote:… if it even exists. I’m sure I remember seeing them sometime in the dim and distant past but maybe I’m imagining it.

I’m trying - and failing - to find a bolt that is essentially a miniature scissor jack something like the following image of a jack that I just found on the internet simply to illustrate this post - https://www.chegg.com/homework-help/que ... -q44935168

I want to build a small contraption which is essentially a wooden sandwich where the “bread” is 2 wooden sheets (plates) separated by probably 4 of such bolts so that I can slide it under something and then open the bolts so that the plates move apart to contact the floor ant the bottom of the object it’s underneath. The challenge is that in its closed (most compact) configuration it can be no more than 7cm high including the thickness of the 2 plates so that means the bolts - or whatever mechanism I end up designing for the “filling” in my sandwich - can’t be more than about 5cm high when closed and ideally smaller since I would prefer to use thicker wood to maximise strength if I have the space to do so.

I have come up with an idea for a home made mechanism but it would be far simpler to find an off-the-shelf part that I could use but so far quite a lot of internet searching hasn’t come up with anything.

- Julian

Have you considered an hydraulic/pneumatic method?
An inner tube 'tween a couple of bits of ply

I would need a better explanation of your requirements. Meanwhile, is this going in the right direction https://www.amazon.co.uk/KPTIJXE-Hand-L ... B0CB3LGZRW

GrahamPlatt wrote:I would need a better explanation of your requirements. Meanwhile, is this going in the right direction https://www.amazon.co.uk/KPTIJXE-Hand-L ... B0CB3LGZRW

Bit odd that the last photo titled "Widely Application" is a compilation of 6 images of which 5 depict the items performing no function at all

GrahamPlatt wrote:I would need a better explanation of your requirements. Meanwhile, is this going in the right direction https://www.amazon.co.uk/KPTIJXE-Hand-L ... B0CB3LGZRW

I think this product is an accessory for a doll’s house. Claimed dimensions are 10 mm by 10mm by 10mm and weight 1 gram.

Back to the original question - a "lead screw" or a "ball screw" may aid your googling...

DeepSporran wrote:

GrahamPlatt wrote:I would need a better explanation of your requirements. Meanwhile, is this going in the right direction https://www.amazon.co.uk/KPTIJXE-Hand-L ... B0CB3LGZRW

I think this product is an accessory for a doll’s house. Claimed dimensions are 10 mm by 10mm by 10mm and weight 1 gram.

Indeed. And this one must be made of an incredibly advanced material. Measures 19x8x19cm, lifts 120Kg yet weighs only 0.9g.

https://www.amazon.co.uk/Eidoct-Lifting ... B0B5M15WS8

Thank you everyone for the incredibly helpful replies. As well as triggering some ideas this thread has also resolved the mystery of the type of bolt I somewhat mis-remembered and also a few other useful items that, although not applicable to my current project (because I didn't fully explain the requirement), are none the less all very interesting bits of technology to file away for potential future use.

On the type of bolt I was misremembering Doug2500 put my mind at rest there. I had a distorted mental image of some sort of Frankenstein bolt comprising a pair of toggle bolts (hollow wall fixings) back to back which I guess only exists in my mind! Anyway, at least I now know what they really are and what they are called. Thanks Doug.

On my requirements I'm not wanting to actually lift anything. I have a very large cantilever patio umbrella at my holiday home that does need to be relocated about 4 times a year (every time I go away or come back) so the base is on locking wheels. The issue is that those 50mm diameter hard plastic wheels only provide a limited contact area with the tiles they sit on so, even when locked and the umbrella closed, a strong wind can still push the approximately 120kg weight (base plus umbrella) around a bit and a medium gust of wind can also move it a bit when it is open. We're only talking about between 5 and 30 cm of movement depending on wind strength and duration but still enough that I would like to reduce it.

My thinking is that if I can increase the friction between the base of the umbrella stand and the surface of the tiles that will give significantly increased resistance against lateral force and help keep the umbrella base where it needs to be. In order to do that maybe rather than describing the device I'm thinking of as a "sandwich" perhaps an inside out brake pad mechanism might be more descriptive where, rather than brake callipers pinching a pair of brake (friction) pads in towards a brake disk, the expansion mechanism that I was trying to come up with pushes a pair of friction pads outwards towards the base of the umbrella stand above and the surface of the tiles below. I suspect it's pretty obvious by now that my height restriction for my contraption comes from the clearance between the bottom of the umbrella base and the surface of the tiles which is 75mm. The device in its non-expanded state needs to be no more than say 70mm (to allow for a bit of tolerance) so that it can be slid underneath the base prior to expansion.

Chris (csearle) mentioned pneumatics and that got me thinking and I'm now pretty convinced that that is definitely the way to go. I also see that subsequently gnawsome and I came up with exactly the same idea, a car inner tube sandwiched between ply (and for my application with rubber sheet glued on top/bottom faces to create the friction). To make that work though one of the ply sheets (I would choose the top sheet) would need a groove/slit cut into it for a tyre inflator extension hose (that I have found on Amazon) to run through so that I could effectively relocate the tyre valve to the outside wall of the tyre otherwise it wouldn't be possible to get to it to fully inflate or to deflate it.

Having said that I was surprised to see that the products Chris linked to - https://www.amazon.co.uk/dp/B0C659KQ1P/ - are rated to lift 200kg and a 4-pack is only £11.99! I was concerned about having the inflation bulbs permanently connected but I see that they are only 43mm in diameter so they will easily tuck under the umbrella base to get them out of sight and avoid a tripping hazard when not in use so I think this is the way I'm going to go. I might still use the lifting bags as the expansion mechanism inside a ply+rubber sandwich - maybe one at each corner to expand the plates - but depending on how durable and grippy the material on the lifting bags feels and how much contact area they have when inflated to 75mm height that might not even be necessary. One of the nice aspects of this project is that if whatever device I come up with fails there would be no heavy weight crashing down or other dangerous/damaging event, all that would happen is that the extra element of lateral resistance would be lost and the system (umbrella sitting on 4 locked wheels) would revert to its original state.

Anyway, one way or another you fabulous people have helped me come up with three eminently workable plans - Plan A (lifting bags on their own), Plan B (lifting bags between ply+rubber plates) and Plan C (inner tube between ply+rubber plates) and you've also thrown up some other interesting fixings and gadgets along the way so I am most grateful to all of you who took the time to reply.

- Julian

I'm surprised that the caster type wheels don't have snap close locking mechanisms but if I understand correctly that the intension is only to stop the whole thing moving around then can you not just employ some small hardwood wedges to chock the wheels.

Alternatively could you have a go at replacing the wheels with something like this :-

https://www.amazon.co.uk/Castor-Wheels- ... 625&sr=8-4

Dicky99 wrote:I'm surprised that the caster type wheels don't have snap close locking mechanisms but if I understand correctly that the intension is only to stop the whole thing moving around then can you not just employ some small hardwood wedges to chock the wheels.

Alternatively could you have a go at replacing the wheels with something like this :-

https://www.amazon.co.uk/Castor-Wheels- ... 625&sr=8-4

It does have exactly the type of wheels you linked to and the locking mechanisms are very solid, it's just that the contact area between the bottom of the wheels and the tiles is very small. In high winds the umbrella isn't moving because the wheels are turning, it's sliding on its locked wheels.

Maybe I should have said that my holiday home is not in the UK, it's in Cape Town and I'm 10 floors up. I'd guess that someone familiar with typical UK southern England winds should add about an extra 10 to 20MPH to UK wind speed expectations to get the Cape Town wind levels e.g. "this is a nice calm summer's day" in Cape Town probably means the wind is in the 10MPH to 15MPH range gusting up to 20 to 25 MPH level and "gosh, it is pretty windy today (but nothing newsworthy)" probably means the winds are in the 30MPH to 40MPH range with gusts up to 50MPH or even 60MPH.

Obviously I don't have the umbrella up in those sorts of winds but even closed with a tight cover over it repeated 40MPH (or more) gusts hitting it can slide it around a bit.

I'm also not sure that chocks would stay in place in such winds. I've lost an almost full 5kg bag of barbeque coals swept over the balcony (which means it got lifted over a 60cm wall) and I've had some pretty impressive things blown onto my balcony that presumably were blown of someone else's balcony e.g. various shoes and the metal lid from someone else's Weber. I've also had my wicker patio furniture blown about 2 metres across the balcony over the course of a windy night despite the sofas being tethered to a pair of 25kg weights and each armchair to a single 25kg weight. The winds in Cape Town really can be something to behold.

- Julian

Would these be of any use? https://www.amazon.co.uk/dp/B08N9KHFS9/ref=sspa_dk_detail_1?pd_rd_i=B08N9KHFS9&pd_rd_w=0YHjg&content-id=amzn1.sym.67430c1d-696a-45e1-be6b-972213775cc6&pf_rd_p=67430c1d-696a-45e1-be6b-972213775cc6&pf_rd_r=MKBZ6Z89TS9NDQT8XGJD&pd_rd_wg=LmFJW&pd_rd_r=ac1e9dcd-9be4-4723-b0c0-00641fd5d677&s=industrial&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWwy&th=1

Remove the existing castors and use these when you need to move it?

Adrian

How about a low profile trolley jack. This one has a minimum height of 7.5cm...
https://www.halfords.com/tools/garage-w ... -AQAvD_BwE

Other trolley Jack's are available.

Julian wrote:

Dicky99 wrote:I'm surprised that the caster type wheels don't have snap close locking mechanisms but if I understand correctly that the intension is only to stop the whole thing moving around then can you not just employ some small hardwood wedges to chock the wheels.

Alternatively could you have a go at replacing the wheels with something like this :-

https://www.amazon.co.uk/Castor-Wheels- ... 625&sr=8-4

It does have exactly the type of wheels you linked to and the locking mechanisms are very solid, it's just that the contact area between the bottom of the wheels and the tiles is very small. In high winds the umbrella isn't moving because the wheels are turning, it's sliding on its locked wheels.

Maybe I should have said that my holiday home is not in the UK, it's in Cape Town and I'm 10 floors up. I'd guess that someone familiar with typical UK southern England winds should add about an extra 10 to 20MPH to UK wind speed expectations to get the Cape Town wind levels e.g. "this is a nice calm summer's day" in Cape Town probably means the wind is in the 10MPH to 15MPH range gusting up to 20 to 25 MPH level and "gosh, it is pretty windy today (but nothing newsworthy)" probably means the winds are in the 30MPH to 40MPH range with gusts up to 50MPH or even 60MPH.

Obviously I don't have the umbrella up in those sorts of winds but even closed with a tight cover over it repeated 40MPH (or more) gusts hitting it can slide it around a bit.

I'm also not sure that chocks would stay in place in such winds. I've lost an almost full 5kg bag of barbeque coals swept over the balcony (which means it got lifted over a 60cm wall) and I've had some pretty impressive things blown onto my balcony that presumably were blown of someone else's balcony e.g. various shoes and the metal lid from someone else's Weber. I've also had my wicker patio furniture blown about 2 metres across the balcony over the course of a windy night despite the sofas being tethered to a pair of 25kg weights and each armchair to a single 25kg weight. The winds in Cape Town really can be something to behold.

- Julian

If you don't want it to move can you tie/lash the base down?
I decided that was the safeste way to go for outdoor stuff after having had to take a 12" trampoline down from a tree
I like nylon cinch straps for this kind of thing - as they are easy to undo when you decide you do want to move the thing

servodude wrote:after having had to take a 12" trampoline down from a tree

A bit small even for the Koalas up there I suppose so do you have gymnastic mice?