On Mon, 01 Apr 2013 14:41:47 -0400, Spehro Pefhany
wrote:

On Mon, 1 Apr 2013 09:15:51 -0700 (PDT),
wrote:

Hi guys. I have a unique garage business selling hardware to builders and repairers of upright basses. Check bass capos dot com for details. One thing they need is a small but strong pulley wheel with a 1/8" dia. round belt race. The ones I supply are brass with a sealed bearing and are a bit overbuilt and expensive for the application. I want to arrange for a run of a few hundred which would be more fit for purpose, and hopefully a bit cheaper.

The plan is for a 7/8" dia. x 1/4" wide brass pulley with a 1/4" brass axle and without the sealed bearing. There is a constant force of about 120 lbs. on the shaft, but almost no rotation. Maybe +/- 1-2° a few times a day for tuning, and no adjustments at all sometimes for weeks or months, and it must be usable for decades. I think that simple brass on brass should work if both parts are well machined/polished/lubricated, but there have been anecdotal failures. So, I need to do something more if only for marketing, but also I stupidly offer a ten year warranty. So, I must be very careful about how I design and produce my wares!

Anyway, what are some options?

What's wrong with an oil+PTFE-impregnated bronze bushing bearing on
the 1/4" shaft? You'll need something like a 3/8" hole in the pulley.
It's a standard part costing less than $1.

P.S. an SAE 841 sleeve bearing with a Pmax of 2,000 will have a
maximum load (zero RPM) of 125 lbs on a 0.25" shaft if it is 0.25"
long. A 3/8 long 1/4" bearing would be rated proportionally more.

They recommend shaft hardness Rb 85 for the shaft material.

http://www.capturedlightning.org/hot...rasssleeve.pdf


Best regards,
Spehro Pefhany
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