Alternative Materials to Bronze for high-load bushings... are there any?

[Orange Vise]

I would talk with an applications engineer at IGUS. They offer a huge range of polymer bushing options, and with a "safety (near) critical" bushing of this nature, I'd want a pro assisting the materials decision.

Contact an igus expert

Contact an igus expert

www.igus.com

I bought a few of those awhile back. They're nicely made, but the tolerances were a bit loose - made to spec, but the spec is loose, IIRC something like 0.002". Bronze can easily be machined to a couple tenths tolerance.

 

[Rollerman]

Consider C9130 Bronze, 80% Copper, 20% Tin, or
C9530 Bronze, Copper, Aluminum, Iron alloy

 

[TwinSpool]

Without knowing the loads on the bushings it's hard to spec a material. The dynamic loading makes the calculations not trivial.

I would stick with the OEM material. Maybe try to figure out why the bronze is wearing so quickly. A lubricated pin in a bronze bushing shouldn't wear at an unacceptable level unless there's something else going on (IE dirt ingression, etc). It's likely there's a contributing factor that is going to affect any bearing material.

 

[eKretz]

Probably they aren't getting lubricated as frequently as they should be, on top of the apparently fairly sloppy fit right off the bat. Likely not easy to reach from the ground. I always wondered why they didn't throw o-rings in the end of the pins (captured by the bushings) to hold grease in and dirt out.

 

[Gordon Heaton]

Talk to these guys: https://thordonbearings.com/
They have some amazing materials. The one I'm familiar with is called 'Thordon Blue'. It is very resistant to abrasive contaminants. It is also very expensive. Biggest problem for your application would be that it is normally an interference fit. Sounds weird but it works, and if it lasts long enough maybe the installation hassle would be ok.

 

[Rickyb]

Two things that should be in the bushing design are seals and grease grooves. If they don’t exist in the current design add them before making major design changes. Aluminum bronze may be an option for you also.

in regard to plastic bushings of any kind it is impact loading and/or creep will come around and bite you. The material can flow out of the high stress areas

 

[JS]

954 aluminum bronze will wear pins, if not greased........
841oilite bronze & 660 leaded bronze seems to be used in about everything with bushings............

How hard can it be?

You just have to figure out bronze, figure out a seal .......make them do the maintenance.......

When in doubt find an Engineer.............he'll figure it out by the book and it'll get field modified to actually work.......[]

 

[JST]

Probability of a serious issue is small, agreed. Consequences of an issue are very large, even monetarily, not to mention the cost to anyone injured/killed. Juries award totally stupid amounts of money these days.

Small probability of happening, large overall cost if it does..... makes the "actuarial risk" much the same as a larger probability of an issue, with a smaller cost per failure.

If something has a chance of happening only once in 10 million rides, but the cost is 10 million dollars if it does happen, you will on average pay the same amount as if it happens every single time the ride is started, but only costs a buck when it does.

And, where does the responsibility fall? On the person making the change, and on the carney owners.

 

[john.k]

i wonder if the OP is putting correct oilways (for grease) in the bushes .....all sorts of complex patterns used by the old timers........without oilways/greasegrooves bushings wear rapidly,.....with proper lube distribution wear is negligable.

 

[Peter from Holland]

Slip fit There is your problem The pin must be propperly secured to begin with
It must be tight and locked Any movement in the pin results in a extra hammering effect on the bushing
Also the tighter the bore of the bushing the less hammering you have
With the spiders I worked on the booms stayed connected to the frame btw

 

[bosleyjr]

If the current replacement worked well I'd be leery of a back of the envelope design. That said, this seems to be a pretty poorly designed unit, given excessive grease required, poor service life, and excessive lash. That lash bothers me as it could end up fatiguing some part of the joint leading to catastrophic failure. The point is that the current mfr-supplied solution may have liabilities, too.

Without engineering analysis and testing I'd be leery about trying something, but if you are able to monitor the equipment and perhaps tear down your replacement bushing for inspection over very short, short, and medium duty cycles you might be able to come up with something that works.

If you want to try a plastic, you might want to look up Vesconite. Out of South Africa - used in diamond mining equipment. Low friction and durable. But you have a constant asymmetric load, so you might see creep.

That said, cast bronze is used in a lot of earth-moving equipment. Perhaps try to find a drop-in cast bronze replacement with a matching pin, properly sized, to minimize lash. There are companies serving this area.

Cast Bronze with grooves (National Bronze):

 

[snowshooze]

An Internet forum engineering change for a carnie ride! What if the harder bushing wears the shaft to a small diameter and the shaft snaps?
Man, I’d never touch a project like this. Carnie rides fail occasionally and people get hurt.
Be careful out there

The guy services it weekly.

 

[snowshooze]

If the current replacement worked well I'd be leery of a back of the envelope design. That said, this seems to be a pretty poorly designed unit, given excessive grease required, poor service life, and excessive lash. That lash bothers me as it could end up fatiguing some part of the joint leading to catastrophic failure. The point is that the current mfr-supplied solution may have liabilities, too.

Without engineering analysis and testing I'd be leery about trying something, but if you are able to monitor the equipment and perhaps tear down your replacement bushing for inspection over very short, short, and medium duty cycles you might be able to come up with something that works.

If you want to try a plastic, you might want to look up Vesconite. Out of South Africa - used in diamond mining equipment. Low friction and durable. But you have a constant asymmetric load, so you might see creep.

That said, cast bronze is used in a lot of earth-moving equipment. Perhaps try to find a drop-in cast bronze replacement with a matching pin, properly sized, to minimize lash. There are companies serving this area.

Cast Bronze with grooves (National Bronze):

View attachment 372822

If the current replacement worked well I'd be leery of a back of the envelope design. That said, this seems to be a pretty poorly designed unit, given excessive grease required, poor service life, and excessive lash. That lash bothers me as it could end up fatiguing some part of the joint leading to catastrophic failure. The point is that the current mfr-supplied solution may have liabilities, too.

Without engineering analysis and testing I'd be leery about trying something, but if you are able to monitor the equipment and perhaps tear down your replacement bushing for inspection over very short, short, and medium duty cycles you might be able to come up with something that works.

If you want to try a plastic, you might want to look up Vesconite. Out of South Africa - used in diamond mining equipment. Low friction and durable. But you have a constant asymmetric load, so you might see creep.

That said, cast bronze is used in a lot of earth-moving equipment. Perhaps try to find a drop-in cast bronze replacement with a matching pin, properly sized, to minimize lash. There are companies serving this area.

Cast Bronze with grooves (National Bronze):

View attachment 372822

I got Bronze.
The Factory replacements are junk.
I can do far better.
But, I am also trying to get a decent lifespan out of these simple bushings.
Customer is well tired of purchasing 2 dozen pieces of junk for premium rates.
Too much clearance on both ID and OD....

Junk.

 

[eKretz]

I got Bronze.
The Factory replacements are junk.
I can do far better.
But, I am also trying to get a decent lifespan out of these simple bushings.
Customer is well tired of purchasing 2 dozen pieces of junk for premium rates.
Too much clearance on both ID and OD....

Junk.

Try fitting some sort of seals captured at the ends of the pins or bushings. Alongside the better fits and assuming proper lubrication intervals, that should help prolong the life of the pins and bushings considerably.

 

[snowshooze]

Sounds like the problem is the quality of the bushings (poor execution of the manufacturing), not the material choice/design. Loose bushings will wear faster.

I would sooner source better bushings than jump ahead and change the material.

McMaster has material. Not sure if this is the exact grade, but the dimensions match: https://www.mcmaster.com/8911K337/

Bronze cuts like butter, and with a 1:1 length to diameter ratio, this is a gravy job.

I am not a Machinist to be buying somebody else's junk, which is exactly the problem my Customer has now...
I am a danged Machinist.. not a re-seller...
Ha.
No offense.
Mark

 

[snowshooze]

Try fitting some sort of seals captured at the ends of the pins or bushings. Alongside the better fits and assuming proper lubrication intervals, that should help prolong the life of the pins and bushings considerably.

The Factory bushing are junk when they are new.
Junk.

 

[eKretz]

The Factory bushing are junk when they are new.
Junk.

Yes, we all pretty much gathered that. I was running under the assumption that you were going to make some properly fitted ones yourself this time.

 

[snowshooze]

Sounds like the problem is the quality of the bushings (poor execution of the manufacturing), not the material choice/design. Loose bushings will wear faster.

I would sooner source better bushings than jump ahead and change the material.

McMaster has material. Not sure if this is the exact grade, but the dimensions match: https://www.mcmaster.com/8911K337/

Bronze cuts like butter, and with a 1:1 length to diameter ratio, this is a gravy job.

Uh huh.
Been doin' this well over 40 years.
Over 25 years as an Owner.
Source them.
But then, why the hell am in in business???
Quit it.

 

[snowshooze]

I bought a few of those awhile back. They're nicely made, but the tolerances were a bit loose - made to spec, but the spec is loose, IIRC something like 0.002". Bronze can easily be machined to a couple tenths tolerance.

Hi Orange.
I am a machinist, of all things.
I am looking for materials, not anything else.
I am taking field measurements tomorrow.
A couple tenths?
Every day here.
The job is to do better than the Manufacturer.
That is the PROBLEM.
And, that is my market.
Would I machine your work to where it suited me?
I honestly doubt it. You don't play around. If you took this job, you'd be on the same page.

 

[snowshooze]

Yeah, shit. Well...
Are you a Machinist?
I doubt it.