OT Reducing friction between bronze bushing and shaft?

Hazzert · Sep 22, 2018

I have a 4.5” diameter aluminum spool running on a 1/4” 316 shaft with 9/16” flange and aluminum bronze bushing with 1/2” flange with approximately .001” clearance. The two flange faces make light intermittent contact with each other. I have relieved the flange face on the bronze bushing to reduce the contact area to two small rings. And the shaft is relieved in the middle to reduce overall contact.

The spool is retained on the shaft with a bolt which also makes light intermittent contact.

Similar commercial products will spin for 5-10 minutes with a solid spin and this spinning time is the end user’s judge of “quality” but right now I struggle to get 30 seconds.

I would prefer not to have to rely on the flange and bolt to maintain position but this application requires positive retention.

Does anyone have suggestions for how to reduce the friction in this application.

Trboatworks · Sep 22, 2018

Someone is getting a lightweight fly reel spool on bushings to spin for 5-10 minutes?
No possible way.

Hazzert · Sep 22, 2018

10 minutes is a bearing reel, but I’ve personally spun bushing reels had a conversation with someone and come back to reel still spinning. Specifically though this is a centerpin reel for drift fishing, hence the demand for low friction.

billzweig · Sep 22, 2018

I do not know much about your application but 316/bronze is not the best combination for low friction. For best results the shaft should be hardened steel and if is a question of corrosion resistance at least hardened stainless. The roundness and accuracy of the two is important too. Bored bushing and ground shaft, both round and parallel. And finally .001” clearance on 1/4 shaft is hardly a high precising. All this being said spinning for 5-10 minutes is approaching perpetual motion.....

Hazzert · Sep 22, 2018

Bushing is reamed with a new spiral flute HSS reamer, if the consensus is that a bored bush is better I will remake it. Dimensions are pre press and there is no discernible play. I had assumed with the shaft running on oil film that perhaps the cof between the two wasn’t quite as important.

CalG · Sep 22, 2018

dry lube....vent the flanges

Milland · Sep 22, 2018

Dynamic balance of the spinning assembly is also important, if you're out of balance there will be "tipping" within the bushing to shaft mate, which leads to metal on metal contacts at high frequency.

1) Good bushing choices - center relieved, porous bronze or similar, light synthetic oil lubed. Clean, burr-free pores, which means that if you have to resize it, you should bore it with a dead-sharp carbide tool. In this case, a repurposed new carbide two or three flute endmill might be a good choice.

A true .0005" (12U) fit between bore and shaft for smaller assemblies should work. Maybe a minimum of three or four to one on bearing/shaft length to diameter ratio.

2) Hard, straight, polished steel shaft, 440C stainless is a good material here.

3) Hard, polished thrust contact washer, again, 440C. Minimal contact surface, but enough to establish and maintain an oil film.

4) Balanced assembly; without good dynamic balance you can't spin for a long time without using ball bearings.

Trboatworks · Sep 22, 2018

Hazzert said:
10 minutes is a bearing reel, but I’ve personally spun bushing reels had a conversation with someone and come back to reel still spinning. Specifically though this is a centerpin reel for drift fishing, hence the demand for low friction.

Each line guide has more friction than your bushing.
A frictionless reel and the line piles up on your boots.
I would be designing more for acceptable free spool which stands up to years of use.

Hazzert · Sep 22, 2018

Trboatworks said:
Each line guide has more friction than your bushing.
A frictionless reel and the line piles up on your boots.
I would be designing more for acceptable free spool which stands up to years of use.

These aren’t my design requirements but more standards for this style of reel and whether or not I agree completely with them it is still how the product would be judged. I understand and acknowledge the point though. I am comparing this to a reel made for 50 years, I have made a single reel so far.

TDegenhart · Sep 22, 2018

For something to spin that long, I suspect either an air bearing or magnetic bearing.

Tom

Gordon Heaton · Sep 22, 2018

Did you use a known bronze alloy? All bronzes are not the same for bearing use.

Hazzert · Sep 22, 2018

954 aluminum bronze, no appreciable difference from 660 leaded I tried firs

Milland · Sep 22, 2018

Hazzert said:
954 aluminum bronze, no appreciable difference from 660 leaded.

Is it porous, or straight cast? I suspect you'll want a porous bearing (as I mentioned before) to try to maintain constant oil films.

Hazzert · Sep 22, 2018

Sorry milland I am on mobile was going to address your post when I got to a PC, it is straight cast. My initial design called for an oilite bushing but I had a design error and didn’t have a flanged bush on hand. McMaster carries a PTFE lubed and 30w lubed do you guys feel it makes a difference in this application?

thermite · Sep 22, 2018

Hazzert said:
954 aluminum bronze, no appreciable difference from 660 leaded I tried firs

I actually "traffic in " Nickel-Aluminium Bronze. Absent pressure lubrication? My choice of "stainless" for shafting would probably have to be Stellite, a Nytronic, or HSS-Cobalt. Nothing softer.

Shiney gummi-bear 316 has no business in any sort of bearing not KEPT under water or oil, and even then with an elastomeric mate, not a Bronze if it is for a rudder post or such. When mated with Bronze, it needs far more frequent inspection and attention.

If Oilite "1" Copper-Tin Bronze is too soft for yah?

Get an uber-hard shaft into the mix and try Oilite II (Copper IRON Bronze).

Milland · Sep 22, 2018

Hazzert said:
Sorry milland I am on mobile was going to address your post when I got to a PC, it is straight cast. My initial design called for an oilite bushing but I had a design error and didn’t have a flanged bush on hand. McMaster carries a PTFE lubed and 30w lubed do you guys feel it makes a difference in this application?

No worries. I'd still go for a oilite, but ideally with a lighter than 30W oil, and synthetic to ensure longer life. No Teflon, not for this application...

Hazzert · Sep 22, 2018

For everyone concerned about the 316 shafting, does your opinion change at all if the shaft sees low load sub 120 rpm for 99% of it’s life? I can look into harder shafting but the shaft is tapped #4-40 and #10-32 on the ends.

The old guy making these does the work manually so I chose materials mostly likely workable for him. It might be time for an improvement over his.

Milland · Sep 22, 2018

Hazzert said:
For everyone concerned about the 316 shafting, does your opinion change at all if the shaft sees low load sub 120 rpm for 99% of it’s life outside of casting?

Nah, it's just not a good choice unless it'll NEVER make contact with the bushing. It's too soft, and any incidental contact will scuff it up, making it worse for dynamic bearing function.

Really, you want a hard, polished shaft for this application. Or, use the 316 shaft as the axle for a ball bearing assembly. It'll work for that.

thermite · Sep 22, 2018

Hazzert said:
For everyone concerned about the 316 shafting, does your opinion change at all if the shaft sees low load sub 120 rpm for 99% of it’s life outside of casting?

Mine does not. Most of its "life" it is actually going to be idle, in storage, I'd bet. That doesn't mean one could use silica gel or Camphor wood when it is called upon to do a JOB.

So no. 316 just isn't "good at that", and there are other SS which ARE, so no compelling reason to choose it.

Not as if you needed all that much of it per unit that the materials cost diff was Big Bucks.

thermite · Sep 22, 2018

Milland said:
Nah, it's just not a good choice unless it'll NEVER make contact with the bushing. It's too soft, and any incidental contact will scuff it up, making it worse for dynamic bearing function.

Really, you want a hard, polished shaft for this application. Or, use the 316 shaft as the axle for a ball bearing assembly. It'll work for that.

When.. we were living where river, brook, and lake trout were on the Dance Card some weeks, Deep-sea charter boats other weeks, Dad went all OCD over the best "Shakespeare" reels he could (probably not really) afford. He tried to explain the difference between freshwater rigs and saltwater, spin-csting, fly casting, jigging, dunking, etc.

Given I took all the Rainbow or Bluegill we could eat on an ignorant stick, #9 hook, Earthworms, the only thing I much remember is that they DID have ball-bearings and appeared to be better-built than a Swiss watch (of 1949-1954, anyway..) . Just over-kill for the simpler business of eating reliably of uber-fresh fish.

OT Reducing friction between bronze bushing and shaft?

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