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

snowshooze

Hot Rolled
Joined
Sep 15, 2010
Location
Anchorage, Alaska, USA
Hi guys;
You may be familiar with the carnival ride called the spider.
Flying chairs on 20' booms. And they cam up and down.
Like a crane boom. Just up and down. Pin through hole, slip fits for being constantly torn apart and moved then assembled again..
Alright. The bushings are 3" x 3 1/2" x 3 1/16" Long and made of bronze. A dozen per rig.
Owner is not happy with factory supplied replacement bushings, too sloppy and at 20' he says he has too much lash.
Plus, they wear out and the thing is a grease guzzler. It sounds like he greases all the time but still wears them out.
I suggested a spring loaded grease cup on that particular point.
But I was thinking, possibly, Nylatron bushings?
Maybe Delrin... ( Seems way too soft for the tonnage loading ) Peek plastic???
I need to be able to handle a couple three hundred pounds per square inch or better.. accounting for the surface area of the bottom half of the bushing... maybe practically I should triple that... -- engineering for the real world --
Does anyone know of a Phenolic or plastic bushing that can handle this type of exposure?
When I was working for Wagner Mining equipment, they had like graphite infused phenolic tubing, like 18" ID and I'd make bushing out of that a foot long or so... that would be the bushing for articulating front-loaders... no idea where in come from.
Like a linen blanket in graphite loaded epoxy.. it would look kinda like bakelite, except black from the graphite. Don't have a trade name.
Anyway... alternative to bronze in this application.
Is there any? ( I was wondering too if oil-lite... )
Thanks,
Mark
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
Glacier bushings used in many cranes .........made of a sort of copper graphite string......at least they unwind as string when they fail.............I never liked them ,because I need to see lots of grease.
 

snowshooze

Hot Rolled
Joined
Sep 15, 2010
Location
Anchorage, Alaska, USA
Glacier bushings used in many cranes .........made of a sort of copper graphite string......at least they unwind as string when they fail.............I never liked them ,because I need to see lots of grease.
John, you have any source or somebody I could talk to in application engineering?
I have this morbid interest in things like this...
Thanks!
Mark
Oh, gee!
Like kingpin bushings, I know them .
Maybe I could machine an insert and just replace these as needed, and with the grease dimples, may be quite superior.
Thanks again!
Mark
 
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D Bronson

Aluminum
Joined
Dec 12, 2012
Location
MN
Mark:

SKF has filament wound bushings that can withstand static pressures of ~20,000 psi. You might give them a look. We haven't used them - so I can't comment on cost, availability, or performance.

Regards,

DB
 

snowshooze

Hot Rolled
Joined
Sep 15, 2010
Location
Anchorage, Alaska, USA
Lives are literally riding on these bushings. Who is assuming the liability for the engineering change?
Yeah, there is that.
It seems like lives hang on everything I do these days, escalators, elevators, Jesus nuts for helicopters.
Somebody has to take the job.
I would rather do it myself rather than give it to China...
You may note that I am consulting the best people I know here.
 

eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
Compressive strength on GS is WAY higher than 300 psi. I don't think it's that big of a deal if one of these bushings starts to go out; the ride will probably clunk and grind a little but it's not like the arm is going to fall off from a bushing failure. If it were an area where a failure meant the arm would actually fall that would be different.
 

eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
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

It's a 3" diameter pin. Pretty sure it's going to take a while to wear that down anywhere near it "snapping" with a load of 300ish (or even the tripled 900ish) psi. Preventative maintenance? Inspection? Some of you mustn't have worked on much big machinery. This particular machine owner is complaining about bushings repeatedly wearing out, so obviously he's doing maintenance and inspections. It's worth a try, he can always switch back to bronze if they don't perform any better.
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
I think the string bushings may be problematic with regular assembly and disassembly.....they are quite easily damaged ,and once the strings come loose ,they ve had it.......not to mention costly......so there is no way you can just roughly align the holes and drive a steel pin in with a sledge.
 

johansen

Stainless
Joined
Aug 16, 2014
Location
bainbridge island
if the loading is high enough that plastic will not hold up, i don't want to be riding on one of those things.

work out the surface area for a ball joint in an average vehicle and you might discover your life is riding on less of a safety margin than a 3" pin on a carnival ride.
 

Comatose

Titanium
Joined
Feb 25, 2005
Location
Akron, OH
Yeah, there is that.
It seems like lives hang on everything I do these days, escalators, elevators, Jesus nuts for helicopters.
Somebody has to take the job.
I would rather do it myself rather than give it to China...
You may note that I am consulting the best people I know here.

There are people who could do the calcs here. There are people that could stamp the drawings here. But there are NOT people with enough clairvoyance to do that based on the information given.

Making parts to print is one thing. This is not that. Be careful.
 

gwelo62

Aluminum
Joined
Sep 17, 2011
Location
ga,usa
How about oil-filled plastic? There used to be one sold to the mines. The oil content was so high it would stain a sheet of paper. MMC used to sell a 'dryer' version.
 

UptownSport

Cast Iron
Joined
Jul 25, 2012
Location
Minneapolis
On every forum there is always the guy that screams 'YOU'RE GONNA DIE AND KILL EVERYONE ELSE.'
Every one. Car Forums. Camping Forums. Machining Forums.
They can retreat to their safety fortress, and sortie with an upped dire prediction every third post.
They have zero helpful to add, except the calculation the upcoming body count.
 

Orange Vise

Stainless
Joined
Feb 10, 2012
Location
California
Alright. The bushings are 3" x 3 1/2" x 3 1/16" Long and made of bronze. A dozen per rig.
Owner is not happy with factory supplied replacement bushings, too sloppy and at 20' he says he has too much lash.

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.
 
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