Sprocket Design and Chain Link Calculation
This tutorial explains how to calculate the number of chain links required for a sprocket with specific characteristics and how to ensure a proper fit. Additionally, it shows how to use SolidWorks to visualize and assemble the components, though the main focus is understanding the technical relationship between the sprocket and the chain.
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"A small step for the designer, but a giant leap for engineering."
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Step 1: Introduction to Sprockets and Their Basic Characteristics
Step 1: Definition and Characteristics of a Sprocket
A sprocket is a mechanical element used to transmit power between shafts using a chain.
For our example, we will use the following specifications:
Sprocket #1
- Outside Diameter (OD): 3.62"
- Diametral Pitch (Dp): 3.35"
- Chain Pitch (p): 0.5"
- Number of Teeth (z): 21
- Shaft Diameter (id): 0.625"
Sprocket #2
- Outside Diameter (OD): 9.84"
- Diametral Pitch (Dp): 9.55"
- Chain Pitch (p): 0.5"
- Number of Teeth (z): 60
- Shaft Diameter (id): 0.625"
Almost forgot something important! One key aspect to consider is that the diametral pitch is calculated using the following formula:
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Step 2: Creating the Sketch in SolidWorks
Now that we have defined our sprockets, let's go back to SolidWorks and create a sketch with the following parameters:
- Center-to-center distance: 24"
- Diametral pitch (Sprocket #1): 3.35"
- Diametral pitch (Sprocket #2): 9.55"
Next, we will add tangent lines and create a closed sketch to improve visualization. This will also be useful for assembling the components later.
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Step 3: Adding Sprockets and Aligning Them
In this step, we will add our sprockets and make them concentric with their respective diametral pitch
As you can see, the diametral pitch represents the path where the chain links will pass through.
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Step 4: Adding Chain Links and Using the Chain Component Pattern
Now, let's add the chain links to the assembly. Remember that the pitch of both chain links must be the same as the pitch of our sprockets, in this example: 0.5".
Once this is done, we will use the Chain Component Pattern function in SolidWorks.
- Chain path: The closed-loop sketch we created earlier.
- Fill path: SolidWorks will fill the space completely along the curve.
- Chain group 1: The first type of chain link; make sure to select the entire chain link.
- Face 1: Select the first connection element of sprocket #1.
- Face 2: Select the second connection element of sprocket #1.
- Path Alignment plane: A plane perpendicular to our connection elements. In this case, we use the front plane of our chain link, as it passes through its center.
We will repeat the same process for the second type of chain link:
- Chain group 2: The second type of chain link; again, select the entire link.
- Face 1: Select the first connection element of sprocket #2.
- Face 2: Select the second connection element of sprocket #2.
- Path Alignment plane: A plane perpendicular to our connection elements, in this case, using the front plane of the chain link, as it passes through its center.
If everything is done correctly, the result should look like this:
To verify what SolidWorks has done, we can check it using the following formula:
- C = Center-to-center distance = 24"
- S = Sum of the number of teeth of sprocket #1 and sprocket #2 = 81
- D = Subtract the number of teeth of sprocket #1 from the number of teeth of sprocket #2 = 39. This value will be found in the following table:
From this, K = 38.53.
Now, substitute all the values into the expression to get the following:
Finally, round up to get 138 chain links. Since we have added two types of links to our chain, divide this number by 2:
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Step 5: Adding Connecting Links to Complete the Chain
You may notice that we are missing a link. This is normal because our path actually requires an odd number of links. We can correct this by adding connecting links.
Simply create a concentric and centered mate between the connecting links and the chain, and the result will be as follows:
