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[TowerTalk] successful tram

To: "Tower" <>
Subject: [TowerTalk] successful tram
From: "Dick Green WC1M" <>
Date: Thu, 21 Dec 2006 21:55:08 -0500
List-post: <>
I'm happy to report that we successfully trammed the first 4-el SteppIR to a
ring rotor at 96' today. Thanks to all who commented on the tram issues,
especially K3NA.
The 1/4" wire rope tram worked great, and was much easier to tension than
nylon rope. I used three 1/4" drop-forged wire rope clips, with nuts
tensioned to 15 ft-lbs.
The aluminum split-side pulley worked fine, but as K3NA predicted, the
aluminum sheave didn't fare too well. The wire rope left deep gouges in the
wheel, in the pattern of the strands. I'd say some are as deep as 1/32". I
don't see any indication that the wheel was in danger of breaking, but it's
pretty-much useless for rope now -- the rough wheel surface would be too
abbrasive. I certainly wouldn't use it for tramming on wire rope again. I
had a marine snatch block with a steel wheel, but the diameter was only
about an inch, so I didn't use it.
Can someone direct me to a good supplier of metal sheave snatch blocks
suitable for tramming? 
K3NA says I need at least an 8.5" wheel, but I'd like to revisit the
calculations on that. I think they're based on the rope making at least a
90-degree turn around the sheave, which doesn't happen in the case of the
tram. The wire rope does bend around a small portion of the wheel's radius,
but not much. I suspect a wheel in the 2"-4" range would be more than
adequate. Comments? What are people out there using for pulleys?
73, Dick WC1M

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