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

Comatose

Titanium
Joined
Feb 25, 2005
Location
Akron, OH
There seems to be a lot more respect for the original engineers here than I would expect. How do we know the engineers didn't spec out loose garbage because it would run long enough and was cheaper, or they simply made a bad call?
Is nobody else constantly redesigning crap that someone engineered terribly to begin with?
I bet the pin was made a small OD for an easily assembled slip fit that wears too quickly.

The original design might well be shit. But it's gonna be at least an analyzed shit, and the complaint is "this is a high wear item" rather than "I'm running out of places to stuff the bodies." I don't think anyone here is saying that this couldn't be analyzed and improved. But that's expensive, time consuming and requires a lot more information.

The OP seems to revel in ignorance, and that's dangerous in this application. For example, what does coefficient of friction have to do with any of it? It's fine to make high consequence parts to a print. It's fine to design high consequence parts. But assuming that competence in one qualifies you to do the other, either way, is a whole other can of worms.
 

dian

Titanium
Joined
Feb 22, 2010
Location
ch
(sorry for not having read the whole thread.)

find out the exact material pairing. improve from there. there are innumerable bronze alloys. no need to get fancy or into unchartered territory imo.*

e.g.: use a harder alloy (some manganese bronze?) and crome plate the pin.

also the type of wear has to be clear. in the case of abrasive or corrosive wear the above will not help much. protect the bushing.

* there are many kinds of bronze products with cavities, dry lube inserts/pucks, powder or infused technology. but this sound simple enough.
 

jackal

Titanium
Joined
May 4, 2006
Location
northwest ARK
(sorry for not having read the whole thread.)

find out the exact material pairing. improve from there. there are innumerable bronze alloys. no need to get fancy or into unchartered territory imo.*

e.g.: use a harder alloy (some manganese bronze?) and crome plate the pin.

also the type of wear has to be clear. in the case of abrasive or corrosive wear the above will not help much. protect the bushing.

* there are many kinds of bronze products with cavities, dry lube inserts/pucks, powder or infused technology. but this sound simple enough.
This is what I was thinking .
Maybe use a naval brass/ aluminum bronze.
It doesn't wear easily,, you said he was greasing it,, and it will take the impact of driving pins thru the bore.

Just a thought, but might be better than what he has now.
 

snowshooze

Hot Rolled
Joined
Sep 15, 2010
Location
Anchorage, Alaska, USA
Em..
The easiest solution perhaps is just to make the bushings 6" in diameter, vs 3".
This will likely make them 4x-8x stiffer and stronger and last 12x+ longer.

Rigidity and strength and longevity tend to be diameter power of 3, or power of 4.
Cost tends to be linear per size.

If it´s easy, and cheapish, I would also make them longer, to maintain the 1:1 D/L ratio.
So 6" in D, and 6" in length.
This is likely about 40x stronger and 40x longer lived.

There are many fudge factors involved, thats why 4-8x vs 16 x in strength.

And almost always, something vastly stronger than "peak load" lasts nearly forever.
Every (good/decent) lathe on the planet is a good example.

Lathe peak loads are 2% of failure/deformation loads.
Mills and VMCs are about the same.
A good manual lathe lasts 50-100 years, give or take.

Another option is std bearings, stacked, perhaps in elastomeric mounts.


Doubling the D will greatly increase the surface speed and R rating of the bushings, but the rides have very low rpm.
Should not have any effect, imho.

Fwiw, I built a carnival ride, and had it professionally inspected and certified and insured, ..what tjhey are.
The pin and hole are a
Another alternative material to consider is GarMax. I've seen that used in loader bucket bushings and such.
Thanks!
More stuff from Garlok...
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
I can tell a story about missing bolts.......Greenslopes Veterans Hospital highrise block job (Civil & Civic AKA Concrete Constructions)...........Hosp Sec issues orders to the main gate to stop wholesale theft of food from the kitchens........this week must search bags for potatoes.......one of the apprentice cooks has his bag searched .....its got a coupla dozen big bolts and nuts in it...........he says he just picked them up off the ground .......OK ,its not food ,off you go.......week later he s stopped again ,more big bolts and nuts from the same place..........anyhoo,this time the Hosp Sec gets the boiler house foreman to have a look at them ,see if they are coming from the hospital......he says ,nope not from the hospital...........Over night ,the tower crane falls down.
 

triumph406

Titanium
Joined
Sep 14, 2008
Location
ca
What the OP should do, before anything else is estimate the max loads on bushings, this will shock horror

REQUIRE AN ENGINEER!!

Once the Engineer has determined the max load on the bushing, and by refering to the PV limits of the material, the OP would then be able to determine which materails are suitable and which aren't.

--------------------------------------------

If what the OP says is true and the ID and OD's are loose on the bushing, then I assume the bushing is getting hammered by the pin and housing during running.
 

Garwood

Diamond
Joined
Oct 10, 2009
Location
Oregon
3" pin is fucking huge. Dirt machines that slam around with multi-ton buckets attached ripping rocks with a couple hundred thousand pounds of force use 3" pins.

The original post says the problem is the pins are sloppy and it hogs grease.

Well, if the fit is sloppy, it's going to puke all the grease out. If the fit is sloppy it's going to pound out the bushings.

Make some bushings that fit tight in the housings and have the correct pin clearance for grease.

All modern dirt machines have sealed bushings. There are lip seals on all the bushings. You could probably cut some grooves in the ID of the bushings for some thin section O-rings. In all reality though, the things should last a real long time if the clearance is correct.
 

triumph406

Titanium
Joined
Sep 14, 2008
Location
ca
The OP says their loose. But how loose?

I suspect their loose to avoid assembly complications. Slide the bushing into the housing, assemble the 2 pieces, slide the pin in. Quick and easy.

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If the bushing is made to have a light press fit into the housing, then it's going to require freezing in Nitrogen prior to assembly (well at least that how I'd do it), maybe into a housing that isn't round anymore. Which is going to increase assembly time, and makes it more complex to remove. So there in lies a problem. Is it more cost effective to have a longer lasting bushing, with a more costly assembly process, requiring better people to install.

Or a looser tolerance bushing that is quick to install, and quick to remove.

And if the OP wants to make better bushings**, I assume he's going to measure all the bores to find diameter variation, and pins as well. Might quickly discover there isn't a bushing ID/OD that works at every location.

-----------------------------------------

It would be interesting to know how often bushings get changed, and how much grease gets used.

Maybe for the average carnival ride operator, changing the bushing more often then once every five years is unacceptable, and more then a pump of grease at the beggining of the season is excessive.

**edit changed pins to bushings
 
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jccaclimber

Hot Rolled
Joined
Nov 22, 2015
Location
San Francisco
This particular machine owner is complaining about bushings repeatedly wearing out, so obviously he's doing maintenance and inspections.
Clearly you know different carnival ride operators than I do. The ones I know wear out three sets of bushings, all while not changing they sloppy worn pins because those cost more, and everything is jury rigged just as good as it needs to be.
Also, everything can be fixed with more grease.
Then, after 5-10 years they get fed up, fix it the right way, and have a few years of smooth sailing before the process repeats.
 

eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
Clearly you know different carnival ride operators than I do. The ones I know wear out three sets of bushings, all while not changing they sloppy worn pins because those cost more, and everything is jury rigged just as good as it needs to be.
Also, everything can be fixed with more grease.
Then, after 5-10 years they get fed up, fix it the right way, and have a few years of smooth sailing before the process repeats.

I guess it depends on the definition of repeatedly and how often he changes them. It would seem he is at least trying to make improvements if he's contacted a machinist asking for a better way... I have to give him at least a little benefit of the doubt.
 








 
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