Unusual bearing design question

lostfrom68jay · 2013-04-01T16:15:51+00:00

Hi guys. I have a unique garage business selling hardware to builders and r epairers 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 r ace. The ones I supply are brass with a sealed bearing and are a bit overbu ilt 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 a necdotal failures. So, I need to do something more if only for marketing, b ut also I stupidly offer a ten year warranty. So, I must be very careful ab out how I design and produce my wares! Anyway, what are some options? 1. A polished SS shaft instead of brass? Good, but the customer needs to cu t the shaft to length and polish the ends. Not practical for most violinmak ers /repairers. They can always special order the needed length, so not out of the question, but extra pain. 2. A bearing-grade bronze shaft with brass pulley? Seems like the most chea p and practical, but how durable? 2. A greased bronze or SS sleeve between the brass shaft and the pulley? So unds good except that afaik it would have to be machined from solid round, upping costs. Anyone know of bushing sleeve available in small diameters li ke this? 3. Delrin bushing sleeve? This seems available in the size I need, but some customers really don't want any plastic on their bass. I know. It's just s omething you have to deal with in my world. 4. SS or bronze Pulley? sounds expensive. ...

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lostfrom68jay 13 years ago

Am Donnerstag, 4. April 2013 23:12:33 UTC+2 schrieb d32:

ith a 1/8 dowl pin for a shaft. They are static load rated at around 200 lbs.

Ned, Sorry, I only checked out Igus just now. They're headquartered in my city! I need to get my head out of my yellow bible sometimes! I figure that a 1/

4" wide x 1/4" bore sleeve would need a minimum P value of 1900. I found a MDS-FILLED Nylon Bearing from McMaster with a P value of 2900. I see that I gus offers way way stronger options.

As to needle bearings, sounds cool, but I really want to use a 1/4" or 6mm brass shaft. It's not only the comfort issue with the luthier, but a 1/8" s haft might compress the wood too much. Many extensions are made of solid e bony, which should be no problem, but some are maple or other softer woods.

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David Billington 13 years ago

a 1/8 dowl pin for a shaft. They are static load rated at around 200 lbs.

need to get my head out of my yellow bible sometimes! I figure that a 1/4" wide x 1/4" bore sleeve would need a minimum P value of 1900. I found a MDS-FILLED Nylon Bearing from McMaster with a P value of 2900. I see that Igus offers way way stronger options.

brass shaft. It's not only the comfort issue with the luthier, but a 1/8" shaft might compress the wood too much. Many extensions are made of solid ebony, which should be no problem, but some are maple or other softer woods. If you sign up on the Igus site they will likely provide free samples of potential candidate bushes. I did this on their UK site and ordered the bushes I wanted and paid for them and got a follow up call wanting to know the application and volume and I explained it was likely a one off but the chap said they would still have provided the bearings as free samples, I presume this encourages repeat business and may lead to larger orders. I expect you would do well to talk to or email an application engineer there and explain the design requirements and see what they recommend and get some appropriate samples. They sent me a welcome pack containing more information and a variety of samples of the range of products types they do.

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Ned Simmons 13 years ago

a 1/8 dowl pin for a shaft. They are static load rated at around 200 lbs.

need to get my head out of my yellow bible sometimes! I figure that a 1/4" wide x 1/4" bore sleeve would need a minimum P value of 1900. I found a MDS-FILLED Nylon Bearing from McMaster with a P value of 2900. I see that Igus offers way way stronger options.

brass shaft. It's not only the comfort issue with the luthier, but a 1/8" shaft might compress the wood too much. Many extensions are made of solid ebony, which should be no problem, but some are maple or other softer woods.

Igus is a class act. I spent about $8000 with them in the last year, mostly cable carriers and flexing duty cable. But they've been just as helpful in the past when all I wanted was $15 worth of bearings.

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lostfrom68jay 13 years ago

Am Freitag, 5. April 2013 20:11:31 UTC+2 schrieb Ned Simmons:

ng with a 1/8 dowl pin for a shaft. They are static load rated at around

200 lbs.

ity! I need to get my head out of my yellow bible sometimes! I figure that a 1/4" wide x 1/4" bore sleeve would need a minimum P value of 1900. I fou nd a MDS-FILLED Nylon Bearing from McMaster with a P value of 2900. I see t hat Igus offers way way stronger options.

6mm brass shaft. It's not only the comfort issue with the luthier, but a 1 /8" shaft might compress the wood too much. Many extensions are made of so lid ebony, which should be no problem, but some are maple or other softer w oods.

Sounds like a great outfit. The GLW series has a P value 6x what I need. I' ll give them a call!

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