Need Help in Designing

Yes it can be done with just the right handed nut. But not as designed in the drawing. Have worked on many lift tables used in warehousing. All had the scissor arms pinned to clevises on one end. At the top to the platform and below it to the base. Force can applied to the free arms at the bottom to raise the platform. Not sure of the purpose of the spring. Weight of the platform should keep tension. Unless spring is to counter the weight of the platform to make it easier to crank up.

4 ft high by 3 ft wide ?

I want to be sure the dimensions are right !

If you want to elevate the inner tube by 3 feet then you nee to find space for the elevator. there is a design that is totally beneath the tube, but requires everything be raised to accomodate the mechanics, about 3.5 feet or 4.

there is an internal arrangement which the mechanics fit inside the raised tube, and there is no space required beneath it, however you cannot put anything inside the tube.

Yes, its correct. its 4ft high wt a dia of around 2.5-3ft. the entire tube needs to be lifted from beneath. pls note that the tube is not very heavy, approx.20-25kg. but the problem is- it needs to be rotated continuously at a slow spped. thats why i used a motor at the base.

waiting for comments and sketch.

1. fit the table previously described inside the larger tube. Add the chain drive so the handle exits the outer tube.

2. add height to the outer tube equal to the height of the compressed table

allowing 4 feet above the tabletop.

3. mount the rotation motor on top of the table previously described.

4. attach inner tube to motor.

5. for this setup it would be best to turn the handle directly on the table

with no chain or other drive due to space in the outer tube.

Dear Mr. Warner,

Thanks a lot for the modified design. Well whenever you get time please help me in designing the second exhibit. Being a non technical person, these designs are helping me immensely to develop the exhibit of my imagination.

Regards,

Look again at your drawing. If you put weight on the right hand side of the table it will collapse. You need to replace the rollers on the left with fixed joints. OR the rollers on the right. BUT with a single nut design the table will move sideways as it is raised. I am sure a turnbuckle could be bought and used in the design as they have both left and right hand threaded rod and "nuts".

Second problem could be solved with rope and a winding drum as seen on the table of most shop presses.

Jim

Jim: Thanks for your comments, but I've looked at it quite a bit more, and I don't see why it should collapse. The short arms keep the table centered. In case it's not obvious, the short arms are fixed to the table and base. Here are a couple more drawings where I've added some color to clarify it. I've also added channels for the corner wheels to run in. The first drawing shows the unit in the raised position.

Weight on the right hand side will tend to make the top rotate clockwise, but it is held back by the short green arm. It will also tend to make the entire table rotate clockwise about the nut, but it is held back by the light blue short arm. The entire unit will be considerably more stable if all corner wheels run in channels, as shown.

The second drawing shows the unit in the down position, and also shows a top view.

To the OP: I've shown the raised position where the struts are 30° from vertical. I don't recommend going any higher than that. I've also shortened the threaded rod to prevent it from going higher.

I just put in a little more effort and I agree that you are correct. For the scenario that was envisaging would happen, the centre pivot would have to be absent.

A GA from me.

Jim

Thanks Jim

I forgot to mention in my last post that I had thought about mentioning a turnbuckle (in fact it took me a large fraction of a minute to remember the word, although I had a perfectly good mental image, and have several up on the roof), but they don't have a very long stroke, and would be difficult to connect to an outside operator handle.

About the turnbuckle; I was envisaging it being cut in half with the threaded rod being extended to the required length and the resultant 'nuts' being welded to the scissor legs ( or at least, the bars between them ). This point is now moot as your design works with simpler material requirements.

I, for one, are looking forward to your solutions to his other problem.

Jim

Excellent idea to cut the turnbuckle in half! As you say, this latest design avoids the need for left-hand threads.

I really should have been doing other things, but since you 'challenged' me, I spent most of yesterday on the other problem. See next post.

Dear Friend,

I am waiting for your design for the next problem. Hope you get time.

Hi Sub ( hope you don't mind the shortened nickname)

First, I get the impression that you are working on some kind of a hands-on display, and I definitely want to encourage that!

For the scissor lift, there will be some variation depending on the sizes of the bearings and members, but as shown, to get 12 cm of lift would require ≈18 cm platform width.

I should have some time this evening or tomorrow. I'll clean this up a bit and send you a drawing with some dimensions. Since you've used both English and metric units in your posts, do you have a preference?

Meanwhile, for the cylinder project, how much space is there to be between the inner and outer cylinders? Or, if the outer cylinder has an OD of 3 feet, what is the OD of the inner cylinder? Wall thicknesses? Since the inner cylinder is acrylic, I assume it holds something to be seen. The more details you can provide, the more likely a given design will meet your requirements.

Here is the cleaned-up version with dimensions. Although I have a strong preference for metric units, my work requires me to work almost exclusively in imperial. I have to confess that when I made this drawing, I was thinking of standard inch size parts, like 0.750" bearings and 1/4-20 threaded shaft. I have left off any unit marks for the dimensions, so they can be interpreted as cm with no problem, except for example that you probably won't find 0.375 cm x 0.625 cm bar stock to make the Scissors bars.

I used a crossed chain/belt so the screw can be standard right-hand threads and still have the ergonomics. This will require a flexible chain/belt, possibly plastic.

Of course the whole thing can be scaled to any size. The only critical dimensions are the 1:1:2 ratios of the hole spacing in the scissor bars.

If you send me your email address via private message, I can send .pdf files that will be a lot sharper. If you have CAD available, I can also send DXF files.

Dick

Hello.

Nice drawing.
can I request to send to my email?
Thank you.

Robert (elektrikar@email.cz)

Thanks.

Welcome to CR4!

Normally they don't allow email addresses in posts, but I got yours... Yes, I can send drawings. Do you prefer 2D drawings or a 3D model, or both? Do you have file format preferences?

Dick

yes send this on my email. thx. bye.

2D and 3D.

Rob.

Welcome to CR4!

As I said in earlier posts, I can't place the detailed drawings here. Click on the honeycomb or my name on any of my posts to get to my profile page, then click on "Send DKWARNER a message". In that message, include your email address and which file formats you can import.

I don't have Autocad, but I can export to a variety of formats, both 2D and 3D. I most commonly use DXF for 2D drawings and IGES for 3D drawings, but I can do several others.

Each time someone has asked for this, I have done a little more work on it. Here are JPEGs of the current files:

The 3D (at a low position, NOT bottom), shown with the top plate flanged for stiffness and transparent for visibility:

A metric dimensioned front view:

It should be obvious that this can be scaled up or down, and that the lifting arms shown are for lifting fairly light objects. There are LOTS of details not shown, such as most fasteners, but a person with significant experience making stuff should be able to figure out those details.

Sorry for answering late.

At the onset I would like to thank you for taking time to finalize the design. I know that I am little demanding. But you guessed it right. I want to make hands on exhibit which will increase the liking of the common man to science. It gives me a lot of inner satisfaction.

Now lets get back to action- The tube project is being planned with the following objective-

There will be three tubes, with a lighting arrangement in the innermost tube. Outside it will be the second tube which will have some images. the outermost tube would be opaque tube with an oval window at a height of 4 ft and a handle at 3.5 ft. Only the inner two tubes would be rotating slowly.

Now the visitor would look through the window of the outermost tube and would see those interesting images against a colourful background, as provided by the light arrangement in the innermost tube.

now the visitor rotates the handle fixed on the outer tube. what he sees is- the inner tube is rising slowly while still rotating. the total rise would be around 4 ft from ground level.

actually i am using coloured light to give an impression of water.

I hope that I can explain the project now.

Looking forward for your comments.

As I indicated in my reply to JIMRAT, I spent most of yesterday on the tube project.

Here's the result, done before I saw your latest post. A set of three rollers mounted inside the top of the outer tube guide the inner tube. These should have Teflon or similar surfaces to avoid scratching the inner tube. The inner tube and its contents are supported on a 'spider' of bearings like those used in 'lazy Susans' or microwave ovens, and there is also a central shaft to drive it from the motor/gearbox mounted below a disk. Spacers provide space for the motor and connect that disk to a second one below it, which has three rollers that run in rails to prevent rotation of the assembly, while allowing vertical motion.

A set of three aircraft cables connect to this assembly, and run up and over a set of three pulleys mounted on the outer tube, then down to another set of pulleys, also mounted on the outer tube, and then to the groove in a drum. That drum is connected to a worm gear and worm, which in turn will be connected through a linkage to the visitor handle (not shown). As shown, the worm gear and drum must rotate about 142° to lift the assembly 3 feet. Using a worm gear prevents the assembly from falling if the visitor releases the handle. Since it might be difficult to find the worm and worm gear, another possibility would be to attach counterweights to the down cables totaling just under the weight of the lifted assembly; then the assembly would only fall slowly if the visitor released the handle, and a simpler arrangement could connect the drum to the visitor handle.

Dick

Dear Dick,

Can you please send the sketch in higher resolution so that my technician can understand.

Regards,

I can only send it if I have an email address to send it to. Unfortunately, CR4 does not have a mechanism for sending high resolution images. Click on 'DKWARNER' at the top left of any of my posts. this will take you to my personal page, where you can select "Send DKWARNER a message", near the top right. Send your email address and a list of file formats you can use. The original was created in Vectorworks 2012, but the likelihood of you having that available are close to zero. I can send it as a PDF, but if you have a CAD program available, I can probably export it in a format your technician can read, such as DXF or DWG.