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Re: [TowerTalk] Yaesu rotor controller: replacing drive belt with anO-ri

Subject: Re: [TowerTalk] Yaesu rotor controller: replacing drive belt with anO-ring
From: "Mark ." <>
Date: Tue, 21 Feb 2006 10:26:18 -0500
List-post: <>
Hi Dave,
I ran into a similar situation at work when repairing one of our scientific 
instruments that has a motor driven spindle. The manufacturer was happy to 
quote me a replacement drive belt for $20!
I found a standard o-ring that matched the size, and it appeared to be 
identical in every way to the original. Total cost was about 10 cents!

Standard industrial O-rings come in 5 different cross-section diameters. For 
each cross section, there are a range of sizes listed by inside diameter. 
Each specific size is identified with a 3 digit "dash number" (-XXX), where 
the first number identifies the series (and thus x-section dia), and the 
last 2 numbers determine the ID.

O-ring    X-section
series      diameter
-0XX        .070 in
-1XX        .103 in
-2XX        .139 in
-3XX        .210 in
-4XX        .275 in

For your application, the -0XX series has the closest matching cross 
sectional diameter. Next, you have to look up the ID's available in that 
series from a chart. One place to see a chart is Navigate 
to their catalog page #3271.

Back calculating the ID based on your OD measurement (subtract twice the 
cross section), I get a nominal ID around 1.36 in. On the McMaster-Carr 
online catalog page #3271, find:

The nearest match is: a # -028, with actual ID = 1.364", and actual OD = 

The general purpose, black rubber composition, "BUNA-N/nitrile" type will 
work just fine.

Since you probably don't want to buy their minimum qty of 100, ask for a 
#-028 from your local hardware store or machine shop.



Dave Asks:

<<Well, while powering up today for the weekend contest one of my Yaesu 
control box indicators failed to turn.  So I pulled out one of the spare
boxes and plugged that in... unfortunately when I turned it on the indicator
motor spun up to full speed but the needle didn't move!  Opening it up
showed a broke drive belt... looks like dry rot of the rubber as there are
some other small cracks in the rubber.  Besides looking like a real pain to
replace, does anyone know of a source for these little rubber belts?  And
how to specify them??  It looks to me more like an o-ring than something
meant for driving a gear train.  But anyway, its about 1.5" in diameter, or
about 4.75 in circumference and 1/16" thick.

David Robbins K1TTT  >>


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