Guide
Trolley drop is the distance from the top of the I-beam down to the centerline of the conveyor chain. Two measurements, the I-beam size and the trolley drop, match the right replacement trolley to your overhead conveyor.
Before you start
You need a tape measure. Lock out and tag out the conveyor before you measure.
What you need
Two numbers match your trolley.
Fig. 1 · I-beam size and trolley drop on an overhead conveyor trolley.
| 01I-beam sizeHow tall the track beam is. | 02Trolley dropTop of the beam to the center of the chain. |
Step 01
How to measure the I-beam.
Measure the height of the beam, from the top of the top flange to the bottom of the bottom flange. That is your I-beam size. Frost trolleys fit 3, 4 and 6 in I-beams.
Fig. 2 · I-beam size: top of the top flange to the bottom of the bottom flange.
Step 02
How to measure trolley drop.
Find the middle of the center link. That is the chain centerline. Measure straight up to the top of the I-beam.
Fig. 3 · Trolley drop: chain centerline straight up to the top of the I-beam.
Measure from the top
Drop is measured from the top of the beam, not the bottom. On a 3 in beam, 2 1/2 in below the beam is a 5 1/2 in drop.
Match your numbers
Trolley drop chart for 3, 4 and 6 in I-beams.
Find your I-beam size and drop, then check the chain size and the direction of the attachment holes.
| I-beam | Chain | Drop | Attachment holes | Part numbers |
|---|---|---|---|---|
| 3 in | X-348 | 5 1/2 in 139.7 mm | Vertical | 3 in X-348 trolley |
| X-458 | 6 3/16 in 157.1 mm | Vertical | 3 in X-458 trolley | |
| 4 in | X-458 | 7 3/16 in 182.5 mm | Vertical | 4 in X-458 trolley |
| X-458 | 8 in 203.2 mm | Vertical or horizontal | Vertical · Horizontal | |
| X-678 | 7 7/16 in 188.9 mm | Vertical | 4 in X-678 trolley | |
| 6 in | X-458 | 10 in 254.0 mm | Horizontal | 6 in X-458 trolley |
| X-678 | 10 in 254.0 mm | Vertical | 6 in X-678 trolley | |
| X-678 | 10 9/16 in 268.3 mm | Horizontal | 6 in X-678 trolley |
Two trolleys share a 10 in drop on a 6 in I-beam. The chain size and hole direction tell them apart, or send us a photo. Frost also makes 4 in channel inverted trolleys. See all overhead conveyor trolleys.
Before you order
Choose the wheel, seal and bracket.
| Option | Choices |
|---|---|
| Wheel design | Retainer · Full ball complement |
| Attachment holes | Vertical · Horizontal |
| Seals and shields | Open · Splashproof® · Triple labyrinth · Contact lip seal, nitrile · Splashproof® and wiper, nitrile · Splashproof® and wiper, Viton® high temp · Welsh plug only · Shield only |
| Bracket | Forged, swaged wheels · Formed steel, bolted wheels (3 in X-348) |
Options vary by trolley. Not sure what you run now? Send us a photo of the trolley.
Questions we hear a lot.
What is trolley drop on an overhead conveyor?
Trolley drop is the vertical distance from the top of the I-beam to the centerline of the conveyor chain. A replacement trolley has to match both your I-beam size and your drop.
Do you measure trolley drop from the top or bottom of the I-beam?
From the top of the I-beam. Measuring from the bottom flange leaves out the height of the beam, so the number comes up short.
What size I-beams do Frost trolleys fit?
Frost overhead trolleys fit 3, 4 and 6 in I-beams. Frost also makes 2 in overhead trolleys, and inverted trolleys in 4 and 6 in. For those, send a photo or talk with our team.
Two trolleys have the same drop. How do I tell them apart?
On a 6 in I-beam, the X-458 horizontal and the X-678 vertical trolleys both have a 10 in drop. Check your chain size and the direction of the attachment holes, or send us a photo.
Talk with our team
Send us your two numbers. We’ll match the trolley.
Send your I-beam size, trolley drop, the part number if you have it, and a photo of the trolley.
616.453.7781 · frost.sales@frostinc.com
Want a copy for the shop floor? Download the printable guide (PDF). Next: find your trolley wheel configuration or measure your conveyor chain.
Related Guides
Guide
How to Measure Conveyor Chain
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