You might be surprised, but a section of Unistrut channel has a lot in common with a 2" x 4". Both the strut and a board aren't of much by themselves. To finish a project with wood, you might need nails, deck screws, or joist hangers. Your bundle of strut will stay in a pile until you add fittings, fasteners, and hardware to the mix. On any given day, we receive questions about all kinds of components found in the Unistrut Engineering Catalog, but a recent question about one of our trolleys was so good that we decided to share it with our Tech Talk Readers. Today's question concerns a Unistrut Trolley (part number P2750) which is a 4 Wheel Light Duty Trolley designed for use with 1-5/8" strut. Our customer was confused because of the specs for the Unistrut P2750 Trolley show an outside wheel-to-wheel dimension of 1-1/4". Based on this fact, he was wondering if this trolley is compatible with P1000 (1-5/8" channel).
If you don't work with Unistrut every day, or if you are a relative newbie to the Unistrut system, something like this might trip you up. Here what you need to remember...The outside width dimension of the P2750 trolley is 1-1/4" (1.250), but all the Unistrut trolleys fit within Unistrut P1000 channel and here's why...Unistrut P1000 channel has an outside dimension of 1-5/8" (1.625) with a 12 gauge wall thickness (0.105). The 1.625" OD of the channel minus the wall thickness of 0.105" twice equals an inside distance of 1.415". This distance leaves a clearance of 0.165" between the trolley width and inside walls of the channel. For the visual learners out there, check out the engineering drawing below.....
Now for the disclaimers...Our customer was asking specifically about P1000, but what if you are using P1000T or P1000SL? These channel styles have the same dimensions as P1000, but you need to take into consideration how the channel is being used. If you are bolting through a slotted P1000 member, the bolt might obstruct the trolley wheels. Put another way, the trolley is designed for all 1-5/8" strut, but strut with slots and holes MAY present a problem depending on the placement of your bolts. That said, P1000 is a solid strut with no holes or slots, so compatibility isn't a problem. If you are mounting 1-5/8" channel (solid, holes, or slots) with a Channel Trolley Support (e.g., Unistrut P1834A), the trolley can freely span the entire length of the channel without obstruction as shown in the picture below and then bolt placement isn't an issue.
We hope this clears up the confusion over whether the Unistrut P2750 Trolley is compatible with P1000 channel.....it is! If you have questions about any aspect of the Unistrut system, including parts compatibility, available finishes, dimensions consult our Unistrut Engineering Catalog or contact Unistrut Service Company and we'll gladly lend a hand.