How Do You Calculate Cam Dimensions for Optimal Rod Travel?

• Chantry09
In summary, the length of dimension "A" for the offset on a cam for this project should be equal to 1/2 of the desired travel of rod "C" when the axle is in line with the piston. When the axle is not in line with the piston, the Pythagorean theorem should be used to calculate the length of dimension "A".
Chantry09
Hi,

Im trying to work out the dimensions of the offset on a cam for a project. I know the travel of rod c, as well as the length of the connecting rod b, but I am not sure what the lenth of dimension a should be. I know this is probably simple maths (just pythagoras?) but I need to make sure I get the full travel out of rod c with full 360 degree rotation on the axel.

It would normally be very simple (a = 0.5 x travel of rod c), but it is the fact that rod b is allowed to pivot around the joint to rod c makes it a bit more confusing.

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c will be highest when a is pointing directly upward. At that position, the distance from the Axle to the tip of c is b+ c- a= 1.5- a. c will be lowest when a is pointing directly downward. At that position, the distance from the Axle to the tip of c is a+ b+ c= a+ 1.5. The distance between those, the "travel" is a+1.5- (1.5- a)= 2a. You want a equal to 1/2 the travel just as you said. The fact that b pivots changes the speed with which c travels but not the distance.

As long as the axel is in line with the piston, the cam "a" needs to be half the length of the travel desired at the piston. Therefore, since the cylinder travel is 3/4 units, the cam should be 3/8 units.

The Pythagorean theorem comes into play when the axel is NOT in line with the cylinder.

HallsofIvy said:
c will be highest when a is pointing directly upward.\

... unless the axle is not in line with the cylinder. In that case (in fact, in all cases), cylinder "C" will be highest when the pivot point connecting cam "A" and rod "B" is in a position such that the axle is directly between that pivot point and the joint between rod "B" and cylinder "C"

1. What are cam dimensions and why are they important for working out?

Cam dimensions refer to the size and shape of the cam, which is a mechanical component used to convert rotary motion into linear motion. They are important in working out because they directly affect the performance and efficiency of the cam mechanism.

2. How do I determine the appropriate cam dimensions for my application?

The appropriate cam dimensions for your application depend on several factors such as the type of motion required, load requirements, and speed requirements. You can determine the dimensions by considering these factors and using mathematical equations or computer-aided design (CAD) software.

3. What are the common dimensions used in cam design?

The common dimensions used in cam design include base circle diameter, cam profile height, cam profile radius, cam angle, and cam lift. These dimensions can vary depending on the specific application and requirements.

4. Are there any standards for cam dimensions?

Yes, there are several standards for cam dimensions such as ISO, DIN, and ANSI. These standards provide guidelines for the design and manufacturing of cams to ensure their compatibility and interchangeability.

5. How do I ensure the accuracy of cam dimensions in the manufacturing process?

To ensure the accuracy of cam dimensions in the manufacturing process, precision machining techniques such as CNC (computer numerical control) machining can be used. It is also important to regularly check and calibrate the manufacturing equipment to maintain accuracy.

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