Creating the Perfect Oval...

So, I have another question regarding my generator.

We have it powered by a hand crank. It is connected to the shaft with a belt, and the ratio of the big wheel that we turn to the wheel that is on the shaft is 6:1.

I am trying to make the belt that connects these two, but I am having substantial difficulties. If I make it large enough for the big wheel, there is a lot of extra slack, but if I make it smaller, it cuts through the wheel.

I guess the belt is stretched so its not technically an oval, but I am

stumped as to how exactly I should make it.

Thanks,

Connor

Connor,

The method I learned for constructing this geometry is described in a tutorial model I just uploaded to the 3D Warehouse:

https://3dwarehouse.sketchup.com/model.html?id=13c5c00fdd7b0cb4578ab59bb235330e

I hope this provides answers your question.

Regards,

Taff

Oh my goodness, that is amazing! Thank you so much! Really, I can't thank you enough, this is going to be such a great help.

-Connor

I just finished following your directions, but I now have another question.

I now have the perfect size belt, but it is only 2D at this point.

Whenever I try to use the Push/Pull tool, it deselects itself. It needs a face, right? How do I put one on my shape?

Thanks.

Do you want an 'oval' face, or do you want a 3D belt of that shape?

Taff

I would like a 3D belt. The belt we used is pretty thick, and it would be nice to represent that in the project.

Thanks!

Connor,

You would need to select the 'oval' and use it as a path for the 'follow-me' tool. The profile that would be tracking around the path can be a circle (as depicted) or a 'V'-shape, to get an automobile-style fan belt.

You can read about the 'follow-me' tool in the Users Guide, if you're not familiar with the particulars.

Taff

Great, that's exactly what I needed. Thank you so much, you have been such a big help.

It's great that there is such a helpful, friendly community for this program. It saves me a lot of headaches!

Thanks again,

Connor

Connor,

You caught me just as I was getting ready to go to bed...

There are video tutorials here:

https://www.youtube.com/watch?v=oX6bn0Q0pIM

Video number 9 is for the 'follow-me' tool. (Don't overlook the 'ensharpen codec' note at the top of the page.) [Now that videos are on YouTube, the need for the ensharpen codec has past.]

Good night,

Taff

Hi Connor, hi folks.

See this SU file for ideas:

http://groups.google.ca/group/SketchUp/web/Pulleys%20and%20strap.skp?hl=en [dead link]

I had it ready yesterday but the site would not upload it.

Anyway, you can compare the ideas, it is a variation on Taff's method.

I used circles with only 24 segments, to save on file size but you could use more for a better look, especially for the larger circle.

I also used meters as units. Use whatever dimensions suits you.

In the last scene, I show a crude flat belt made with the following steps:

1 - I build the shape composed of the two arcs and the two tangent.

2 - I redraw one segment to get a filled face.

3 - I use the Offset Tool to get a larger perimeter.

4 - I delete the inside face.

5 - I pull the remaining face to get the required width.

For a V shape, I would use the "Follow me" Tool with the shape built in step 1 as the path.

I would position the V shape on the horizontal plane so it will not be distorted when using the "Follow me" Tool. This Tool will project the profile in order for it to be perpendicular to the start of the path, so, if it is not perpendicular, distortion will happen.

I would also use the same profile with the circle of the pulley themselves, used as paths, to produce the pulleys with V-Notch. Maybe using more than one profiles if a multi belt system is required.

If I can find some time I will illustrate this in a SU file.

Just ideas.

Jean (Johnny) Lemire from Richelieu, Quebec, Canada.

Folks.

I have been following this thread with the usual admiration for usual pros. Most 2D cad programs have a snap-to-tangent command. Maybe SU7 could include one? or a Ruby script? (easy for me to say).

Thanks again, though.

Zook

PS: I found after constructing the belt, the 'V' shape was easy by selecting the inside edges of the belt and scaling them inward.

This discussion has been an interesting exercise/discussion for me, as well. I modified my tutorial to add a final scene depicting several outcomes, including the flat belt suggested by Jean's admirable tutorial.

Jean, your method is the other method I learned in high school. (I had to choose which one to share.) Thanks for providing an alternative technique for study. Sometimes, you just can't beat the old-school drafting techniques.

Regards,

Taff