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On a flexible flat conveyor belt (rod network belt), drive sprockets are normally positioned in the odd-numbered spaces, leaving the even-numbered spaces free for splicing clips. The number of sprockets needed follows a simple rule: one less than the number of belt spaces, plus two blanks — with two exceptions explained below.
What Are Spaces and Blanks?
A space is one of the mesh channels running along the length of the belt — count the openings across the belt width to know how many spaces your belt has (our measurement and identification guide shows how). A blank is an undriven, toothless disc mounted on the same shaft: it supports the belt at the edges without engaging it, keeping the belt level while the toothed sprockets do the driving.
Where to Position the Sprockets
The sprockets are usually placed in the odd spaces and the splicing clips are placed in the even spaces, so that joining clips can be used without interfering with the sprockets. If clips are never used, the sprockets can be placed in the even spaces instead. Whichever convention you choose, apply it consistently — the two arrangements must never be mixed on the same belt.
Arrangement when clips are not used
Arrangement when clips are used
Calculating the Number of Sprockets
The number of sprockets required to drive your belt depends on the number of spaces across the belt:
- Belts with single loop edges need one less sprocket than the number of belt spaces, plus two blanks.
- Drive shafts for double loop edge belts should be set up in the “alternate” style — contact us with your belt width and pitch for the exact shaft layout.
Two exceptions to these rules:
- A) A single space belt uses only two sprockets.
- B) A three space belt requires four drive sprockets and no blanks.
| Belt Spaces (single loop edge) | Drive Sprockets | Blanks |
|---|---|---|
| 1 (exception A) | 2 | 0 |
| 3 (exception B) | 4 | 0 |
| 5 | 4 | 2 |
| 7 | 6 | 2 |
| N (general rule) | N − 1 | 2 |
Three space belt arrangement
Single space belt arrangement
Frequently Asked Questions
Q: What happens if sprockets and clips end up in the same spaces?
A: The clips ride over the sprocket teeth on every revolution, causing belt climbing, accelerated clip wear, and eventually broken splices. If you plan to use clips at any point in the belt’s life, reserve the even spaces for them from day one.
Q: What exactly does a blank do, and can I leave it out?
A: Blanks carry the belt edges at the same height as the driven sections without adding drive force. Leaving them out lets the belt edges sag on wider belts, which distorts tracking — keep the two blanks except on the single space and three space arrangements shown above.
Q: How do I know how many spaces my belt has?
A: Lay the belt flat and count the rectangular openings across its width. If you are specifying a replacement, record the space count together with the wire diameter, pitch, and edge type — the full checklist is in our measurement and identification guide.
Worn or mismatched sprockets are among the top causes of belt downtime. If you are setting up a new drive shaft or replacing components, send us your belt’s space count, pitch, and shaft diameter and we’ll specify the exact sprocket and blank set — contact us here.
