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Please help me construct this
akil_prabhakar
Member Posts: 17 ✭
I want to design a helix type of coupler. The differnece between the normal and this helix coupler wound be that, its pitch on one side has to be larger and the other side it has to be smaller. Hope you can understand what im trying to explain, i have attached a image of a normal helix coupler, in this pitch on both the inside and outside are the same, i want to construct a helix coupler with the outside having a smaller pitch and the inner side to have a larger pitch (varies by very few mm), no need for the end connectors
Best Answer
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rick_randall
Member Posts: 382 ✭✭✭
Look at this example - It doesn't show the ends, just the spiral, but it's the method that's important (also there are some interesting feature scripts to develop spirals around a torus - but I didn't use that method in the example below).
Hope this helps.
1
Answers
Helix's can be tricky, each revolution of a solid helix must not be touching the next revolution.
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Here is an example of how to do this. Note you can edit the main sketch to get the inner and outer diameters that you want.
https://cad.onshape.com/documents/59e80c0257b3265ed3ffa865/w/214042e47d173b56d898746d/e/2c7dff5e7b77cfd86b499a68?renderMode=0&uiState=66e83eb64bda027a985eaf7d
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@MichaelPascoe Thank you so much, you have done it quick and awesome. Is it somehow possible to have a variable thickness along the helix. Like the one that i have marked in pink, on the right side of the helix it is thicker and on the left side it will be thinner. Sorry for troubling you, but im really new to this CAD environment.
Yes, it is possible. But if you are trying to match how these are made in the real world, the helix thickness is a constant thicknesses. It just appears thicker in the picture because it is bending over.
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@akil_prabhakar
Look at this example - It doesn't show the ends, just the spiral, but it's the method that's important (also there are some interesting feature scripts to develop spirals around a torus - but I didn't use that method in the example below).
https://cad.onshape.com/documents/585a5d68201c19bcf2dd93ea/w/11b6048a93ebe74469e26cdb/e/086c1871ae30a60317237888
Hope this helps.
I understood, But I'm planning to make a helix which will bend 90 degrees with minimal bend radius. This helix will not rotate it will just transmit compression force between the shafts
@MichaelPascoe Yes, I want to create that complicated model. I want such a helix coupling so that it can bend 90 degrees with minimal bending radius. Can you help me out. if you give me some basic details I will try to make it.
This is exactly what I'm looking for
The helix coupling is not going to rotate, it will just connect two shafts and will transmit compression load from one shaft to the other
Those are all the same thickness. What you are asking for does not exist commercially. Also, how do you plan to actually "make" one? Out of metal? With what equipment? I think you should re-think your requirements.
Nick is right. When manufacturing these, they are always cylinders, then you bend them to fit the angles you need.
The minimum bend radius is controlled by the empty spaces and they can all be even when machined. They only become uneven once you start to bend it while using it in an application. Once the metal touches metal, the bending mostly stops depending on the size and material. Rick's approach may be better if you want to show the min bend radius. If you are using "my" approach, and still want to calculate the bend radius, you could draw a simple sketch of the helix cross sections which would have the helix count and the helix wall thickness but where all the helix cross sections are touching, this would visually show you the min bend radius.
If you want, you could adjust the example doc I gave you to bend so that you can see what the bend would look like. But when you go to machine it, it needs to be straight in order for it to work right physically.
I'll see what I can do for a bendy example.
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@akil_prabhakar Alright, here is that bendy example which is a bit more complex:
Note that this uses @Konst_Sh's custom feature 3d spiral so you would need to add that to your toolbar.
https://cad.onshape.com/documents/59e80c0257b3265ed3ffa865/w/214042e47d173b56d898746...
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@MichaelPascoe @nick_papageorge073 @rick_randall , guys thank you so much for all the help. I thought of making this project with a metal so that it would be stiff as well as have a minimal bending radius. To manufacture, wouldn't a CNC machine be enough?? If that is not possible I thought i would give it to a gold smith and made it done by hand. Sorry for the late reply guys, I got stuck at work and couldn't even go through all your replies.
@akil_prabhakar
If you are going to actually try to make these, as an alternative, you might want to look in McMaster - Carr
High-Misalignment Precision Flexible Shaft Couplings
These are a little different (bellows instead of spiral) but might do the job , and are a catalog (buy-out) item. Just a thought.
I did enjoy working the cad problem though. Very interesting. P.S. @MichaelPascoe nice approach, I liked it.
@rick_randall same, this was one of the most satisfying problems I've come across yet. I love helix's.
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@rick_randall @MichaelPascoe thank you both for your help, but this is what I really want. I'm no engineer, but just a common man trying to solve a problem. The red color shows the path for the helix to go. The helix has to go through the tube (1.5mm radius) and then it has to be hammered through the box(wodden box).
The whole setup is placed deep inside a container, so you cannot actually see what is happening inside.
I have tried flexible shafts, normal compression springs. The problem with flexible shaft is bending radius. the problem with springs is it is not stiff, so even if its bends 90 degrees it won't go perpendicular through the wooden box. Thats the reason I choose helix, because it can bend(less than the spring), but it will be stiffer than the spring. To further reduce the bend radius, i thought we can reduce the size on one side so it can bend more.
There is not a machinist on the planet that will take this idea. They will all no-quote it.
What are you trying to actually do? The hand sketch you drew above does not paint the whole picture. There is probably a solution that is easier to design and manufacture if the whole problem is understood.
@nick_papageorge073 Imagine a small tube 40 cm long with 1.5cm radius. At the far end of this tube there is a small circular opening of 3mm. Now, this tube will be passed through even a bigger tube of radius 3cm. Once both the tubes are in place we have to pass a drill to make hole through the 3mm opening into the outer tube. (Technically making a drill is very difficult that's why the hammering)
@rick_randall can you please explain to me a bit more about how you designed it, please.
Look again at the example - Make a copy so you can edit. Use the rollback-bar to see each step. Edit each step so you can see how I come-up with the single segment. Pay attention to all the choices in the UI boxes (this is important). The biggest trick is to draw the two rectangles (in the first sketch) on the radials, so that the segments of the circular pattern blend smoothly. Note the example shown has an under-defined sketch - because this was was just meant to show one particular method, not a proper model
@rick_randall Thanks rick will go through and will let you know if I need some help