Spinner geometry

youjin_kim779

Hello there,
I need to draw Onshape design for calculating the rotational efficiency of this spinner (please see the pictures for top and side view). The rotational situation can be seen in the video link. I tried loft, sweep etc to draw this, however, I am new to onshape and awkward in drawing this kind of complex figure. Let me know how I can learn my self. It would be very helpful if you share me some important tools or documents for this geometry. Thank you in advance!
https://youtu.be/oRqKGTWRmsU

Best regards,
Kim

shawn_crocker

I think the main issue with this is that the edge of each fin is not actually fully visible at any perspective so working off photos is really not going to be as good as just guessing the shape while holding the object in your hand.  I would probably find a way to hold the object in a very stable way allowing it to still be rotated.  Then I would find a way to accurately measure points along the edge of one fin measuring the angle of rotation, the vertical axis and an axis perpendicular to the center of rotation.  Then I would map those points into onshape, create some type a curve to reference through the points.  After that the rest of the shape can be represented by sketches on planes.

steve_shubin

@youjin_kim779

The document below is certainly not going to be the full solution to what you’re looking for. But it might help you to get things started

I can’t remember who originally did this in Onshape.

https://cad.onshape.com/documents/870827ae697149dd857f9133/w/95b0f20c48acc62a05330e45/e/4261daf04ba98318ed5333ff

steve_shubin

@youjin_kim779

It’s hard for lme to tell exactly what’s going on in the pictures you posted. Especially with regard to the bottom of the part.

If I get some time, I’ll go back and work on all of the planes so when you first open the document, it won’t display at such an odd angle. The way it is now is because I was just modifying somebody else’s document that was used to make the Archimedes

Anyways, this is a little bit more along the way, hopefully, to what you’re looking for

https://cad.onshape.com/documents/00b3010312e8ca1b3878d7d6/w/bd6e9404fbda6cd6d416c5c1/e/e8350de96482541d89725940

youjin_kim779

@shawn_crocker @steve_shubin Thank you so much for help! I will try to figure it out with your advice!

youjin_kim779

@steve_shubin Thank you! I appreciate your awesome capability to shape it. Actually the more exact looking is here. I will try to modify your awesome draft, and try to make the ultimate solution. If you have more advice for drawing this, please let me know. Again, Thank you SO MUCH for your considerate and smart help.

steve_shubin

@youjin_kim779

https://cad.onshape.com/documents/67c94f1055da1336e5ffcb97/w/d983e9cbb121bed5dea00a51/e/ae496314f41d27144c293c5d

Even with these latest pictures, it’s still hard to tell what is going on in the inner portion of the spinners. I cannot make out the shape of the central shaft with the glassy like reflections in the pictures

eric_pesty

@steve_shubin
Nice surfacing work!
I really need to get better at surfacing as I would have seriously struggled to create something like this! The loft with just one "profile" hurts my brain!

steve_shubin

@eric_pesty

Thanks Eric. I really appreciate the comment. But I have no doubt that you could’ve done the same, and most likely better. Your knowledge of the program astounds me a lot of the time when reading your input into the various discussions here in the forum

I will say this — it wasn’t as if I made this part in a few minutes. It took some time to get things to work

To me, I like a challenge. I think it’s good exercise for my brain — which is a big reason why I like to do this kind of stuff

eric_pesty

@steve_shubin
Thanks for the kind words but I think you might be over-estimating my abilities a bit!
Especially when it comes to surfacing, I just haven't done much of it in general even back in SolidWorks so I really don't have a good grasp of surfacing workflows in general (not just with Onshape) and it's nice to see examples of problems like these solved!

I agree attempting to solve other's problems can be a good way to practice and do things outside of the normal day-to-day, in this case I should really spend some time attempting to solve surfacing problems!

EvanReese

I've gotta throw one in the ring here too. This method is pretty simple, but probably has less shape control than @steve_shubin.

steve_shubin

https://cad.onshape.com/documents/67c94f1055da1336e5ffcb97/w/d983e9cbb121bed5dea00a51/e/ae496314f41d27144c293c5d

Like seeing how other people go about their modeling. Thanks Evan. One of the main ways I learn Onshape — by stepping thru others docs.

Take a look at a cross-section. Notice how the edges of the blade at the cross-section are straight. I’m guessing this is an aspect of an Archimedes. See first picture below

Another thing — from what I could see of the spinners in the pictures, the helix does not have a constant pitch. Rather, the helix of each blade, starts out with a subtle pitch at the bottom — close to being parallel to the top plane. And then as you follow the helix upwards, the pitch increases more and more, to where at the top, it’s almost going straight up. See second picture below.

So, I incorporated the varying pitch design also. But along these lines — my guess is that Michael Pascoe has a more efficient way of doing this type of helix.

Initially, I had a fair amount more items in the feature tree upon roughing in this spinner. The tree is now down to 30 features for the part(s). Might be able to winnow that down some more, but don't feel all that much like trying at this point.