Multiple bearings on one shaft
06-07-23, 08:20 AM
#1
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Multiple bearings on one shaft
Asking once again since wasn't able to find anything about rear hubs with more than 4 bearings such as Bitex BX103R. It has been said that more than one bearing at one end of the shaft should be avoided as a way to increase the load capacity since it's impossible to match the bearings.
https://www.eng-tips.com/viewthread.cfm?qid=292906
https://www.eng-tips.com/viewthread.cfm?qid=292906
06-07-23, 09:19 AM
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I would think your concern is totally unfounded for anything as simple as a bicycle. That link of yours refers to high stress high speed bearings like in turbines that have to have zero flex. These issues come up here from time to time. Bitex hubs are pretty bombproof from what I read.
I copy/pasted this statement directly from that link you posted: "I think what it boils down to is that my hasty assumption of uniform load sharing among multiple bearings is correct only in the case of a perfectly rigid shaft. Elastic flexure completely disqualifies this multiple bearing approach in reality. I really should have seen the impracticality of this approach earlier."
I copy/pasted this statement directly from that link you posted: "I think what it boils down to is that my hasty assumption of uniform load sharing among multiple bearings is correct only in the case of a perfectly rigid shaft. Elastic flexure completely disqualifies this multiple bearing approach in reality. I really should have seen the impracticality of this approach earlier."
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06-07-23, 10:05 AM
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I would think your concern is totally unfounded for anything as simple as a bicycle. That link of yours refers to high stress high speed bearings like in turbines that have to have zero flex. These issues come up here from time to time. Bitex hubs are pretty bombproof from what I read.
I copy/pasted this statement directly from that link you posted: "I think what it boils down to is that my hasty assumption of uniform load sharing among multiple bearings is correct only in the case of a perfectly rigid shaft. Elastic flexure completely disqualifies this multiple bearing approach in reality. I really should have seen the impracticality of this approach earlier."
I copy/pasted this statement directly from that link you posted: "I think what it boils down to is that my hasty assumption of uniform load sharing among multiple bearings is correct only in the case of a perfectly rigid shaft. Elastic flexure completely disqualifies this multiple bearing approach in reality. I really should have seen the impracticality of this approach earlier."
Kinda seems pointless to argue without having in depth understanding of engineering.
https://www.meadinfo.org/2013/01/dup...ement%E2%80%9D.
06-07-23, 10:47 AM
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Perhaps the steel shell helps reduce flex.
The bicycle industry has a long history of doing "suboptimal" things and getting away with it. Before getting upset that it doesn't work in theory, maybe you should find out if it works in practice?
The bicycle industry has a long history of doing "suboptimal" things and getting away with it. Before getting upset that it doesn't work in theory, maybe you should find out if it works in practice?
06-07-23, 11:24 AM
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I'm not sure I understand your question.
Are you looking for a serious engineering analysis on a bike forum?
In any case, your question may br the result of confusion about the design.
The double bearings sharing load considerations don't apply here if you're looking at the rear hubs.
These do have 4 bearings, but they're doing different jobs. 2 bearings support the hub, and 2 support the freehub. So, each is a classic 2 bearing design.
Are you looking for a serious engineering analysis on a bike forum?
In any case, your question may br the result of confusion about the design.
The double bearings sharing load considerations don't apply here if you're looking at the rear hubs.
These do have 4 bearings, but they're doing different jobs. 2 bearings support the hub, and 2 support the freehub. So, each is a classic 2 bearing design.
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06-07-23, 12:41 PM
#6
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I'm not sure I understand your question.
Are you looking for a serious engineering analysis on a bike forum?
In any case, your question may br the result of confusion about the design.
The double bearings sharing load considerations don't apply here if you're looking at the rear hubs.
These do have 4 bearings, but they're doing different jobs. 2 bearings support the hub, and 2 support the freehub. So, each is a classic 2 bearing design.
Are you looking for a serious engineering analysis on a bike forum?
In any case, your question may br the result of confusion about the design.
The double bearings sharing load considerations don't apply here if you're looking at the rear hubs.
These do have 4 bearings, but they're doing different jobs. 2 bearings support the hub, and 2 support the freehub. So, each is a classic 2 bearing design.
Last edited by sysrq; 06-07-23 at 12:51 PM.
06-07-23, 12:44 PM
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https://principle-eng.co.uk/duplex-bearings/
Last edited by sysrq; 06-07-23 at 12:58 PM.
06-07-23, 01:19 PM
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In practice there is no way to tell without measuring the actual load of each bearing. Hopefully it's not just a needless weight being carried around.
https://principle-eng.co.uk/duplex-bearings/
https://principle-eng.co.uk/duplex-bearings/
I doubt any engineering analysis or advanced laboratory testing went into the design. They were probably faced with bearing failure on one side with their most demanding customers, made room for another one, and that solved the problem well enough.
06-07-23, 01:40 PM
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However, here's some grist for your mill.
While a single larger bearing I'd generally preferred to paired smaller bearings, that doesn't mean the second is necessarily bad. For example, as may apply here, dimensional constraints may drive the decision, especially if a roller bearing isn't a good option.
OTOH often what's claimed based on engineering is more about marketing. With a long and proven history of simpler designs, I tend to keep my hype filter set on high.
Personally, I wouldn't consider the added bearings a reason to buy the hubs. However, I wouldn't consider that a reason not to either.
Buy products based on reputation and proven performance. Consider performance in the field the best confirmation that the engineers made good calls.
Last edited by FBinNY; 06-07-23 at 01:49 PM.
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06-07-23, 02:04 PM
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i'd consider the extra bearings to be harder to maintain to clean & grease, unless the design took that into consideration.
What I'd entertain to try is the standard ball bearings in the normal places & then a set of needle bearings positioned in the center (whether one or two sets depending on serviceability] .
What I'd entertain to try is the standard ball bearings in the normal places & then a set of needle bearings positioned in the center (whether one or two sets depending on serviceability] .
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06-07-23, 06:34 PM
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Here is the Bitex hub
https://www.bitexhubs.com/htm/pd_detail.php?no=BX103R
The 6 bearings will increase the friction slightly. The inner bearing will likely stay clean, but won't experience a lot of stress either, most of which will be borne by the outer bearing.
The bearings shouldn't need a lot of maintenance, other than occasional replacement.
Perhaps low quality bearings will wear into each other quickly.
https://www.bitexhubs.com/htm/pd_detail.php?no=BX103R
The 6 bearings will increase the friction slightly. The inner bearing will likely stay clean, but won't experience a lot of stress either, most of which will be borne by the outer bearing.
The bearings shouldn't need a lot of maintenance, other than occasional replacement.
Perhaps low quality bearings will wear into each other quickly.
06-08-23, 10:26 AM
#12
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What is your investment in this hub? Something you're thinking of buying, or it just crossed your radar and now it bugs you?
I doubt any engineering analysis or advanced laboratory testing went into the design. They were probably faced with bearing failure on one side with their most demanding customers, made room for another one, and that solved the problem well enough.
I doubt any engineering analysis or advanced laboratory testing went into the design. They were probably faced with bearing failure on one side with their most demanding customers, made room for another one, and that solved the problem well enough.
06-08-23, 04:50 PM
#13
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So you are asking for an engineering analysis. Unfortunately vastly more specific info would be needed.
However, here's some grist for your mill.
While a single larger bearing I'd generally preferred to paired smaller bearings, that doesn't mean the second is necessarily bad. For example, as may apply here, dimensional constraints may drive the decision, especially if a roller bearing isn't a good option.
OTOH often what's claimed based on engineering is more about marketing. With a long and proven history of simpler designs, I tend to keep my hype filter set on high.
Personally, I wouldn't consider the added bearings a reason to buy the hubs. However, I wouldn't consider that a reason not to either.
Buy products based on reputation and proven performance. Consider performance in the field the best confirmation that the engineers made good calls.
However, here's some grist for your mill.
While a single larger bearing I'd generally preferred to paired smaller bearings, that doesn't mean the second is necessarily bad. For example, as may apply here, dimensional constraints may drive the decision, especially if a roller bearing isn't a good option.
OTOH often what's claimed based on engineering is more about marketing. With a long and proven history of simpler designs, I tend to keep my hype filter set on high.
Personally, I wouldn't consider the added bearings a reason to buy the hubs. However, I wouldn't consider that a reason not to either.
Buy products based on reputation and proven performance. Consider performance in the field the best confirmation that the engineers made good calls.
06-08-23, 05:42 PM
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So you're buying the hub based on info given, which may be material or just hype. But, as you note, the company enjoys a good reputation, so trusting them is probably OK.
OTOH I think you're overly concerned, and probably can do equally well with just about any decent hub.
1600km is not a very long trip, and many here, including me, have taken much longer tours on much less special hubs. Touring or not, my hub service interval is roughly 10k kilos.
So. You probably won't go wrong with these hubs, but you may be spending more than you need to.
BTW ---- Have a great trip, and make plenty of memories.
