At first glance, a gravity conveyor looks deceptively simple. A frame, some rollers, a slight decline, and packages glide where you need them to go. But anyone who has watched a heavy carton race uncontrollably down a mismatched line knows simple does not mean one-size-fits-all.
The biggest mistake operators make when buying a gravity conveyor is choosing the wrong system for the load weight. Get this right, and your conveyor will run for years with no maintenance. Get it wrong, and you will be chasing safety incidents and slowing your operation.
Here is how to choose the right one for your loads.
Start With the Load: Light, Medium, or Heavy
Every gravity conveyor is built around its rollers, and rollers are sized by weight capacity.
Light-duty gravity conveyors (under 100 lbs per load) use 1.5″ diameter rollers in a steel or aluminum frame. They are ideal for cartons, totes, polybags, and most e-commerce packaging. For sorting orders, feeding packing stations, or moving boxes off a truck, a 1.5″ roller conveyor usually does the job.
Medium-duty gravity conveyors (loads over 100 lbs) use 1.9″ diameter rollers. The frames are heavier, axles stronger, and rollers handle higher cycle counts. Most warehouse operations land here.
Heavy-duty gravity conveyors require 2.5″, 2-9/16″, or 3.5″ diameter rollers. For pallets, engine blocks, or large appliances, these rollers have thicker steel walls and frames built for impact.
Roller Centers Matter Too
Roller diameter tells you how much each roller can carry. Roller centers, the distance between rollers, tell you whether your load will be supported.
The rule is simple: your load should rest on at least three rollers at all times. Quality gravity conveyors come pre-punched at 3″, 4-1/2″, and 6″ roller centers, so you adjust spacing as your product mix changes.
Frame Width: OAW vs. BF
Two measurements matter when sizing the frame.
- OAW (overall width): the outside dimension of the conveyor frame
- BF (between frame): the usable rolling surface inside the frame
Allow at least 1″ of clearance on each side of your product. If a load can slide sideways, add guide rails or step up to a wider frame. Standard gravity conveyors come in 12″, 15″, 18″, 24″, and 30″ widths, in 3′, 5′, and 10′ lengths that connect with butt couplings.
Decline Angle and Heavy Loads
For light packages, a 5-degree decline keeps the product moving. For heavy loads, that same angle is a problem. Heavy items accelerate and become impossible to stop at the end of the line.
You have two options. Reduce the decline angle for a gentler slope, or add speed control rollers, which act as a brake and slow descent to a manageable pace. For genuinely heavy or fast-moving loads, gravity alone may not cut it. A motorized live roller conveyor or CDLR conveyor (chain-driven live roller) gives full control.
When a Gravity Conveyor Is Not the Answer
Gravity conveyors are unbeatable for cost and simplicity. But they are not right for every job. A flexible conveyor is a better fit when you need to span variable distances, curve around obstacles, or expand and retract to match trailers at a dock. The expandable design of a flexible conveyor lets you set it up for one shift and stow it the next.
For permanent installations, an automated conveyor, such as an MDR conveyor using motor-driven rollers, makes sense when:
- Your loads vary widely in size or weight
- You need precise speed control or zone accumulation
- You want to bring labor costs down
- The path needs to be horizontal, inclined, or climb a slight rise
MDR conveyors are one of the biggest opportunities for cutting labor costs in modern warehouses. Each motorized zone handles its own flow without manual intervention, freeing your team for higher-value work and removing the repetitive lifting that drives ergonomic injuries.
Get the Right Gravity Conveyor the First Time
A correctly specified gravity conveyor will outlast most other equipment in your facility. An incorrectly specified one creates a cost every day.
If you are not sure which roller diameter, frame width, or decline angle is right for your loads, talk to an experienced conveyor manufacturer. The right partner will answer with a live person, walk through specs, and ship a quick-ship gravity conveyor the same day.
