Hi everyone,

This my first post to the forum.

I have been learning to use MOI since the end of last year. This is a fabulous piece of software on it's own, but the scripts that have been created by different forum members make it even more amazing.

For the past few days, I have been trying to draw a KickStarter bicycle wheel called "loop wheels" (see attached picture and 3dm drawing), but I'm having some difficulties in getting the 2 fiber springs to connect properly.

Any help would be appreciated.

Thank you,

Yves

Hi Yves, welcome to the forum!

It looks like you've made some great progress on your wheel already. Is the particular problem spot right here? You want these to match up better?




How is it that you are constructing these pieces right now, is it by a sweep along a path curve?

- Michael

Michael,

Yes, that's the area that needs to align, but I don't know how to accomplish that.

Yves

Micheal,

sorry, I missed the second part of your question.

I started with creating an ellipse. I then trimmed the ellipse in 2 pieces. Then I used the sweep command to create the spring. I also tried to move the end points (where both springs connect), the result was getting a bit closer to what I need, but I got some alignment issues. The spring seems to need an offset and a twist, but I don't know how to accomplish that.

Yves

Hi Yves, one possibility might be to elongate your path curve so that each piece continued on a sort of mirror image path, then cut them both to the current ending spot that you have now.

But here's another possible way working with just what you have now using Blend.

You would start by cutting away a little bit to leave some empty space that will then be filled in with Blend:



Then slide one piece over so they're lined up with one another instead of offset:



Now select the open edges (you don't want any end caps in place for this, it should just be an open end), and run Construct > Blend to build a connecting piece like this:



Now use that blend section duplicated over (hold down Ctrl and drag it from an edge endpoint for a quick shortcut for this) to get this type of result:



- Michael

Michael,

After re-reading my post I now realise that I did a bad job in explaining my issue. Let me try again...

Each fiber spring consists of 2 separate (off-set) pieces that are joined in the middle. The left section starts with an off-set to the left but then twists so that it ends up in the middle of the wheel rim. The right section starts with an offset to the right, twists and ends up in the middle of the rim on the opposing side.

As you can see in the picture, (see "A" in picture below), both off-set sections are fully aligned in the middle of the rim.

Yves

Have you tried modifing an ellipse by cutting off 1/3 and rotating it out from the top point , duplicating it with array x2 joining and sweeping the profiles around it

I think you get a better result with 3 profiles as it forces the shape to stay square on and not rotate or twist when swept.
If the bottom profile is mirrored you can easily adjust their offset position for a gap

cheers
shayne

Hi Yves, yeah sorry I didn't understand the kind of alignment you were looking for at first, I thought that your current model was already shaped close to what you needed.

So right now with only a planar path for the sweep you won't be able to make that shape you'll need to make a longer path curve that is not planar, it will need to shift over a bit instead of being all flat. One way to do this is to draw it initially flat and then select some points and move them from a side view so you can introduce some out of plane shifting to it, check out the side view of shayne's path curve above.

Another way than that which may work is to use the Flow command to map a rising angled line that marches along your planar base path. There is some description of this method here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4785.13
http://moi3d.com/forum/index.php?webtag=MOI&msg=4877.14

That lets you do produce a non-planar result in a more sort of construction manner, starting from 2 planar curves, one being a base profile and other being a sort of elevation control.

I'm heading out for vacation in just a bit here so I may not be able to help you with this much while I'm traveling.

- Michael

Hi Yves,

Another method would be to created the two red surfaces (Extrude) and the green surface on the diameter, I used revolve at 40°, this would be where the clamp sits, then use blend (Curvature G2) between the end of the red surface and the end of the green surface this way you can dynamically adjust the bulge, I used 2.25, join all and apply a thickness.



Cheers
~Danny~

Does this bicycle is bouncing ?

Shock absorbing spring design instead of spokes :P

Martin Spencer-Ford

A BIG thank you to all the forum members for taking the time to formulate a response. I was able to create what I need by using Shane's method where you use 3 profiles to force the shape to stay square.

Since there seem to be a number of different ways to achieve the same goal, I'm going to continue to experiment with some of the other methods.

@ Danny: I am definitely going to take a look at your method. This also looks promising.

@ Pilou: the fiber springs in the wheels provide suspension. I'm especially interested in these wheels because I ride a Raptobike low racer recumbent (see picture). The small front wheel is uncomfortable on the bumpy Belgian roads. The specific layout of the bike does not allow any other form of suspension.

Very ingenious to put suspensions inside wheels!

The famous "Pavés du Nord" of Paris-Roubaix! ;)