The Hunt conveyor driving mechanism uses a stationary cam and a rotating faceplate carrying pawls. The cam puts the pawls into engagement with chain pins for a push, then lifts them clear for return. Hiscox no. 1227 illustrates this sequence of guided engagement and release.
Hunt Conveyor Drive · Cam-guided Pawl Calculator
Watch the fixed cam guide successive pawls into the conveyor chain. Calculate chain speed, advance and ideal drive work.
Equation Used
- One chain pitch advanced per pawl engagement.
- Six equally spaced pawls.
- Working face vertical during 60° push.
- Steady known chain pull; ideal work balance.
- Losses, inertia, engagement compliance and contact stresses omitted.
Mean drive torque applies at the faceplate, not an upstream motor.
The cam stays still while the pawls travel around it
The driving rim and faceplate rotate together. Each pawl pivots on the faceplate and has a follower guided by the fixed cam. A working pawl bears against a chain pin along the straight conveyor run; the cam then folds it clear for its next pass.
The illustrated arrangement uses six equally spaced pawls. Each vertical working face stays vertical through a selected 60° engagement interval. The chain pin slides vertically along that face as the pawl pivot follows its circular path, while the pin itself remains at the conveyor height. Thus the pawl does not stretch to keep its tip on a straight line.
The displayed cam groove is the centre path of a point follower generated from the selected return orientation. It explains fixed-cam guidance, but is not the original heart-cam profile or a manufactured roller-contact groove.
Size an ideal conveyor motion and work rate
Enter chain-pin pitch, faceplate speed and a known steady chain pull. The calculator reports advance per revolution, push rate, mean and extreme chain speeds, useful power and ideal mean torque.
The pull input represents the load already determined for the conveyor. This page does not estimate granular resistance, bucket fill, incline load, startup acceleration, motor losses or available traction. Torque is at the faceplate, not an unspecified upstream motor.
Six-pawl geometry
Let chain pitch be p. Select pawl-pivot radius R=p so that the horizontal advance over a 60° push is R[cos60°−cos120°]=p. Six pushes therefore advance the chain by 6p per faceplate turn.
At faceplate speed n rpm and ω=2πn/60, the working-face speed is v=Rω sin θ for 60°≤θ≤120°. Mean speed is 6pn/60; minimum and maximum speeds are Rω sin60° and Rω. Adjacent pushes meet with equal speed. Their accelerations differ at handoff, so this is a piecewise kinematic model, not a dynamic shock calculation.
For steady chain pull F, instantaneous ideal torque is FR sin θ/1000 N·m when p is in millimetres. Mean torque is F(6p)/(2π·1000), and useful power is Fv̄/1000 watts.
Selected geometry uses chain height 1.5R, pawl elbow distance 0.6R and a working face extending 0.25R–0.65R below the elbow. The point follower is 0.32R behind the pivot. Pawl orientation is zero during engagement; over the remaining 300°, β=−π sin²(πu), with u running from 0 to 1. Its generated fixed track is P−0.32R(cosβ,sinβ), where P=R(cosθ,sinθ).
80 mm pitch at 10 rpm
Six pawls advance 480 mm per revolution. At 10 rpm this gives 60 pushes per minute and 80 mm/s mean chain speed. Instantaneous speed varies from about 72.552 to 83.776 mm/s.
For 1,000 N steady pull, ideal mean faceplate torque is about 76.394 N·m and useful power is 80 W. Increasing speed increases power without changing the ideal torque needed for the same pull.
Illustrative geometry and design limits
Hiscox identifies the fixed heart cam, rotating pawls and chain pins. The dimension ratios, return law and six-pawl engagement timing are illustrative model assumptions. The animation keeps the pawls rigid and the chain on a straight guide.
Roller size, cam offset, follower pressure angle, pin and hook clearances, engagement compliance, contact stress, lubrication and inertia need further design. The drawing is an explanatory point-follower model, not a fabrication drawing or rated conveyor drive.
The calculator relates the entered chain pull to ideal faceplate torque and useful power. Upstream motor selection requires the complete drive arrangement and its losses.
Primary reference
Gardner D. Hiscox, Mechanical Movements, Powers, Devices and Appliances, no. 1227, printed page 303: Hunt conveyor drive with fixed heart cam, rotating pawls and chain pins.
Hunt conveyor-drive questions
Does the cam rotate?
No. The faceplate rotates around the stationary cam.
Why does the chain pin move along the pawl face?
The pawl pivot follows a circle while the chain travels straight. Sliding contact accommodates their changing vertical separation.
Is chain speed perfectly uniform?
Not for the selected geometry. The calculator shows its speed range and matching handoff speeds.
Is mean torque a motor rating?
No. It is ideal torque at the faceplate for a specified steady pull, with losses and transients omitted.
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