# Homework Help: Min pulley diameter

1. Jan 17, 2006

### KevD

Using normal 1.5mm diameter bike brake cable, what would be the smallest possible pulley i could use to make a 180 degree direction change with the cable without kinking or distorting the cable?/???

Any help with this would be VERY helpful!!

Thanks!

2. Jan 17, 2006

### vaishakh

How is you pulley, Does it has soe edge to balance the string or is it a flat surface. Well if its in the former way, then the radius of the pulley must be enough to sustain the diameter of the string and similarly the thickness of the pulley must be enough to hold the dimeter of the string. I think I have properly imagined about the structure you need.

3. Jan 17, 2006

### KevD

Yes there will be an edge or a groove on the pulley for the cable to rest in. This will be with a steel cable though (bicycle brake cable) and the cable must travel half way around the pulley without kinking. The pulley needs to be as small as possible for the application. I need to know the smallest pulley diameter i can use without kinking the cable.

Thanks very much!

4. Jan 18, 2006

### KevD

Anyone!?!?!

5. Jan 18, 2006

### Orefa

Doesn't this depend on the flexibility of the metal used in the cable? Unless this is a question of theoretical metallurgy, you can always test the cable in question around progressively smaller cylindrical objects until a kink appears.