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NDRiley

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Evening All,

I'm trying to figure out how to make a mechanism which will raise and lower a 700mm long c.20mm dia rod or dowel. The rod/dowel will need to stay horizontal and will need to carry a load of c.90kg. My intial idea is as per the sketch attached. The plan would be to use a piece of threaded bar at each end of the rod/dowel, held vertically and turned using winding knobs attached to the top. The threaded bars would pass through a threaded hole near each end of the rod/dowel and as the knobs are turned the rod/dowel would move up and down. The rod/dowel will not be loaded while it is being moved - it will only need to carry the c.90kg once it reaches the desired position.

My question is how do I create the threaded hole at the ends of the rod/dowel. My preference is to use a wooden dowel as that's where my skills lie and I have the most kit. I would consider using a metal rod but that's more outside my comfort zone. Either way it will need to be round. The ideas I have come up with so far are:

1: Use a wooden dowel: Drill vertical holes through the dowel and put in a metal threaded insert. To make this strong enough I will need to go for a dowel sigificantly bigger than 20mm dia. That can be accommodated.
2: Use a metal bar (or tube): Drill a vertical hole then tap a thread. If I use M8 threaded bar, any idea how big a bar/tube I should be looking at to accommodate the required hole/tap?
3: Try to identify a pre-made fitting (maybe a KD fitting?) which has some means of attaching it to the end of wood dowel and a threaded hole perpdendicular to the long axis of the dowel. I'm not really sure what to search for on this and a general Google search of KD fittings etc has come up blank.

Would be grateful to hear anyone's thoughts on the above suggestions or, preferably, come better ideas!

Many thanks


IMG_1832.jpg
 

Jameshow

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Just a suggestion how about taking a scissor jack apart they are about 18" long iirc.

You would then have the threaded rod and the fittings required.

Cheers James
 

bp122

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How much stroke are you looking at? If it is small stroke, you could look at a cam, it will be lot quicker than a helical adjuster like a screw.
 

Lons

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Am I right in thinking that's 0.9 kg (900 grams) not 90 kg ;)
Either wood or metal would do the job though you might need to use 25 mm dia dowel to accommodate the insert thickness. I have some and could measure the dia tomorrow if you need it. My preference would be a solid mild steel rod as tube would have to be thick wall anyway, it's easy enough to drill and tap.

As said it would take a while to wind it up and down with an 8 mm thread unless you use a cordless drill of course instead of hand wheel.
 

NDRiley

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How much stroke are you looking at? If it is small stroke, you could look at a cam, it will be lot quicker than a helical adjuster like a screw.
Thanks for the idea. Unfortunately Stroke needs to be c.200mm
 

NDRiley

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Am I right in thinking that's 0.9 kg (900 grams) not 90 kg ;)
Either wood or metal would do the job though you might need to use 25 mm dia dowel to accommodate the insert thickness. I have some and could measure the dia tomorrow if you need it. My preference would be a solid mild steel rod as tube would have to be thick wall anyway, it's easy enough to drill and tap.

As said it would take a while to wind it up and down with an 8 mm thread unless you use a cordless drill of course instead of hand wheel.
Thanks for your thoughts. No, it is 90kg! The cordless drill idea is also a great one - stroke needs to be c.200mm so that would avoid a lot of tedious winding.
 

TheTiddles

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I’d buy a TV lift mechanism or take apart a desk mechanism as a first option.

Aidan
 

TRITON

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Are you basing your idea on the UKJ router lift ?. 4 gears,one each corner and a chain to connect ?

I'd say might find such a lift, unless engineering is your thing, would be tricky to complete and a high degree of accuracy would be required, or you might find it tightens or seizes when trying to turn it.

+1 for a scissor-jack affair.
 

TheUnicorn

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Tris

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Look out for caravan corner steadies on ebay, they're cheap, have a fast thread and are driven with a 19mm socket in a cordless drill. All the parts you need should be there, just a bit of ingenuity required to get the threaded insert into your dowel/rod
 

mindthatwhatouch

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As others have stated, Scissor jack, the beauty also is with a left and right hand thread movement along the screw is quick.
I adapted one for lifting my cyclone off the bin, works well. I’ll try and get some pics if it helps.
 

NDRiley

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Thanks everyone for some really helpful suggestions- much appreciated. I’m going to digest all that then get back to the drawing board.
 

Terrytpot

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The op never actually specified exactly what he was trying to move but sounds a bit like a similar issue I could do with solving which in my case is not having rack and pinion table hight adjustment on my Meddings pillar drill although whilst it is substantial I don't think the table weighs in at 90kgs..
 
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