# How to draw this roller on picture?

Heloo, can you draw this in sketchup? or there is a lack of information?

People are not here to model things for you but to help you learn to do it yourself. So why not tell us specifically what problems you are encountering trying to translate this sketch into a model?

And, yes, you have presented too little information, and in too illegible a form. To me, it’s a matter of simple courtesy to make a question asked here clear enough so that someone trying to answer does not have to waste time trying to decipher the question before providing the solution.

-Gully

Your question is still not completely clear, but I’ll take a stab at it…

I assume the goal is to draw the circles so they are tangent at the indicated point. And I assume that your issue is that the two circles you have drawn intersect rather than being tangent.

First, you didn’t state what radius you used, so it is not possible to determine whether the problem is with SketchUp or is user error. By my calculations the radius should be 528 1/3 cm. For starters, please realize that value cannot be represented exactly using floating point computer arithmetic, as in SketchUp.

But even using that value, you need to understand that SketchUp represents a circle as a regular polygon with many sides, not as a true circle. Only the vertices where the sides meet are located on the theoretical circle. You can increase the number of sides to improve the approximation, but it will never be exact. The result is that if you look close enough you will always find flaws like the failure of the sides to pass through that point. It will do so only if that point is a vertex (you can force it to be a vertex by using it as the second point when you draw the circle, but inevitably the issue will just show up somewhere else). The question when working with arcs and circles in SketchUp is always “when is the approximation good enough for what I need to do?”. So, what are you trying to do?

Hi dejvick, hi folks.

As written by Gully, there is some information missing to get precisely what you want.

The basic arc can be constructed from a radius and the angles that you provide. The radius is missing.

From the bulge and chord length given as approximate, the arc can be constructed but the angles from the vertical won’t be 25°.

The procedure, once the basic arc is drawn is to make one copy of it along the same axis that you use to build the first arc. Then you flip the copy so that its bulge is opposite of the first one. Finally, you can copy the two arcs as many time as required.

Just ideas.

Jean

Time for you to give us some information about your objective and constraints.

-Gully

Inspired by @Gully_Foyle 's suggestion. If you use 216 sides in the circle you get points where the circles should meet at 25.
But maybe you more need a sinus-curve?
So, spill the beans. What are you asking/needing?

cheers

thanks Pill60, thats what i needed.

My two cents:

Finally erase everything that is not needed.

Anssi

I find this amusing, because I’m the “cmc” who hand-drew this drawing of bmx/mtb pump track rollers.

http://forums.mtbr.com/urban-dj-park/dj-pump-track-plans-402237-2.html#post7415415