Bronze Bushing wearing out steel?

[magnumb 121]

I've read several posts that have indicated bronze bushings are not a good choice because they wear out steel shafts.

Do you think this is an accurate statement? ...bronze should be softer than steel and many are impregnated with oil. Seems like it would take a long time for a bushing to do any damage....

I've found using bushings on crawlers for the pinion shaft on the diff is a better material as they last significantly longer than bearings...about 4 times as long and i've had bearings completely fail and end up chewing up ring/pinion gears due to this. 

 

[MickRosco 10]

Will it be contaminants getting in that wears the steel? That would be my guess anyway

[Kowalski86 3983]

It depends on the application, they're fine in crawlers but I wouldn't want them in a faster RC. Either one is better than plastic bushings.

[TurnipJF 9722]

Consider it a battle, with losses on both sides. The steel is stronger than the bronze, but it will still lose some particles due to wear, just not as many as the bronze will. 

[Mouc-RC 469]

3 minutes ago, TurnipJF said:

Consider it a battle, with losses on both sides. The steel is stronger than the bronze, but it will still lose some particles due to wear, just not as many as the bronze will. 

Agreed!

My Brother recently bought a used OG Bruiser, that spent all his RC life in 2wd Rear-wheel drive (2 servos in the radio box, only throttle + steering)... Just take a look at this, it's the drive pinion for the rear axle:

I started re-building it, luckily I had some spares.

 

 

[magnumb 121]

44 minutes ago, Mouc-RC said:

Agreed!

My Brother recently bought a used OG Bruiser, that spent all his RC life in 2wd Rear-wheel drive (2 servos in the radio box, only throttle + steering)... Just take a look at this, it's the drive pinion for the rear axle:

 

I started re-building it, luckily I had some spares.

That is looking chowdered! That did some damage! Do you know if the bushing was well worn....or was the shaft worn more? 

Also, my bruiser has a black steel pinion shaft and that one almost looks like aluminum!

 

 

[alvinlwh 6884]

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[Mouc-RC 469]

The bushing was totally worn also, but comparatively less than the shaft I'd say.

[TurnipJF 9722]

According to the Wikipedia article linked to (edit: in the now deleted post above), "traditional Oilite is mostly made of copper with approximately 10% tin and up to 1% iron"

Bronze is an alloy of copper and tin, hence, bronze bushings. 😀

[Tamiyastef 2505]

On Crawlers I prefer what I call bronze bushings to ball bearings for the simple fact they don't rust.

I like to run my crawlers in water and not only when I have the next day off to dismantle them completely and clean, dry and relubricate all the bearings.

That's why I build both my CMX's with bronze bushings. An alternative I'm giving a try on my TRX4SPORT build (mostly because the kit comes with all the bearings included and I couldn't find bronze bushings in all the right sizes) is using the ball bearings with Denicol bearings grease for 1:1 motorbikes which is strongly resistant to water.

Normally I always use ball bearings on dry shafts, the only oil used is inside the bearings. On the SPORT they are completely packed in grease. Can't report on the effectiveness yet as my SPORT is still unfinished...

On the subject of wear on the axles the hardness of the materials isn't the deciding factor in my experience. On my Grasshopper BITD the greased (as per manual) kit supplied plastic (definitely the softer material) bushings wore two clear grooves in the front axles. For me it's the grease and dirt combo that creates a sandpaper effect. And that's also the reason I use the water resistant Denicol on the bronze bushings also. If it repels water I hope it will keep dust and dirt on the outside as well. 

[alvinlwh 6884]

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[Nicadraus 6417]

On 6/19/2024 at 2:54 AM, TurnipJF said:

According to the Wikipedia article linked to, "traditional Oilite is mostly made of copper with approximately 10% tin and up to 1% iron"

Bronze is an alloy of copper and tin, hence, bronze bushings. 😀

Let the Wookie win. 

Edit: Let the Jawa win. 

Edit again: Eventually Mr. Know-it-all conceaded and deleted his replies. 

[chris.alex 1050]

I always thought they were made of brass, another alloy of copper and tin*. 🤔 Tamiya call them "metal" anyway. 😀

*Edit: zinc

Edited June 20 by chris.alex

[TurnipJF 9722]

3 hours ago, chris.alex said:

Tamiya call them "metal" anyway. 😀

I think that we can all agree on that. 😁

However if anyone is interested in the composition of bronze(s), I found this article quite informative:

https://www.gsa.gov/real-estate/historic-preservation/historic-preservation-policy-tools/preservation-tools-resources/technical-procedures/bronze-characteristics-uses-and-problems

 

[magnumb 121]

Makes sense about the dirt causing the wear and not the bushing per se...i guess with bearings that is not a concern. Although if the tolerances are tight enough you would think dirt/sand would have a hard time getting in-between the 2 surfaces. I've had soo much trouble with bearings wearing out and causing other parts to break that i now tend to prefer bushings even though bearings have always seemed like an upgrade. For offroad they seem more of a downgrade if you run the car a lot and not great with maintenance. 

Had good luck with them in crawlers and one truck probably has over 150hrs and swapped out the bushings once and the old ones were not that bad. I'll have to measure the wear next time around. 

 

[nowinaminute 3319]

I think with both bronze and plastic, you'll eventually get small deposits of grit etc embedded in the softer material which will start to wear on the steel whilst possibly prolonging the life of the bushing.

There's also the fact that in many cases, the load on the busing is going to be mostly in one direction so the hole will elongate slightly whereas the steel part will get uniformly worn down like a groove which stands out a lot more visually.

[rich_f 245]

7 hours ago, nowinaminute said:

I think with both bronze and plastic, you'll eventually get small deposits of grit etc embedded in the softer material which will start to wear on the steel whilst possibly prolonging the life of the bushing.

Yes I was always amazed that my steel shafts would wear down faster than my plastic bushings/plain bearings, in my very early days of rc, before I could afford ball bearings.

15 hours ago, chris.alex said:

I always thought they were made of brass, another alloy of copper and tin. 🤔

Brass is copper and zinc, not copper and tin. 

[chris.alex 1050]

19 minutes ago, rich_f said:

Brass is copper and zinc, not copper and tin. 

Thanks for the correction! 👌

[Juggular 5079]

I've also noticed that bushings seem to wear less.  I gave some thought on this (because I'm a bored old dude).  

1) Initially, the bushing and the axle might wear equally.  Just that it's hard to notice the wear inside the bushing.  Even as it gets wider (but wider than what?), you have no other surface to compare it with.  But the metal shaft has untouched area above and below the contact point.  I'm sure the bushing [87% copper + 11% tin + 1% iron + etc] is weaker than stainless steel. 

2) Once either (or both) wear enough to let debris in, it's a different story. Oilite bushing protects itself with oil.  Some will get rubbed on debris.  The shaft will get the least amount.  

3) If a perfectly round and perfectly sized grain of sand got caught, that wouldn't be a problem. But what are the chances of that happening?  If its shape is a square, triangle or a flat, it will drag.  The bushing will grab it, but the shaft won't grab.  The inside of a bushing is concaved or cupped, it's easier to grab things.  After all, we put salad in the bowl, not on top of the upside-down bowl.  The outside of a shaft is round and bulged out.  It can't grab.  

Below diagram exaggerated the gap and debris, but you can see how contact points are 2 points for the bushing.  But the contact point for the shaft is 1.  

It's a tug of war between 2 feet and 1 foot.  1 foot side will slide, drag and grind, and that's the shaft side.  Even if the bushing were made out of extra soft copper, debris might lodge itself on the copper, and drag on the shaft.  The result would be the same for pentagons and hexagons (they may roll, but occasionally stop and scratch the shaft more).  That's my theory anyway.  

[magnumb 121]

It seems like a more ideal setup for a bushing would be to have some sort of rubber Oring/gasket to help prevent dirt from getting in....i'm just wanting to avoid bearings at all costs:) At least for offroad RCs. 

[OoALEJOoO 3239]

@Juggular I think you hit the nail spot-on on why the softer bronze wears faster than steel. On my job, we work on rotating equipment that many times use journal bearings with both the external static bushing and an inner rotating sleeve both made of very hard carbide parts. The sleeve generally wears much more than the bushing when running in abrasive conditions because of what you describe.

[markbt73 5610]

On 6/19/2024 at 9:40 AM, nowinaminute said:

There's also the fact that in many cases, the load on the busing is going to be mostly in one direction so the hole will elongate slightly whereas the steel part will get uniformly worn down like a groove which stands out a lot more visually.

I've heard of worn-out industrial motors being "fixed" for a while by pounding out the bushings and re-installing them 180 degrees off, giving the motor shaft a "new" bushing surface to ride on. It's enough to get the motor going until you can replace or rebuild it.

[TurnipJF 9722]

2 hours ago, markbt73 said:

I've heard of worn-out industrial motors being "fixed" for a while by pounding out the bushings and re-installing them 180 degrees off, giving the motor shaft a "new" bushing surface to ride on. It's enough to get the motor going until you can replace or rebuild it.

That sounds like a clever workaround in light of the above.

[nowinaminute 3319]

20 hours ago, markbt73 said:

I've heard of worn-out industrial motors being "fixed" for a while by pounding out the bushings and re-installing them 180 degrees off, giving the motor shaft a "new" bushing surface to ride on. It's enough to get the motor going until you can replace or rebuild it.

Did the same thing on an old tumble dryer once!



I noticed most of them are asymmetrically shaped these days, wonder if it's to impede this "life hack"?

[Gebbly 760]

I remember for a completely different project a few years ago I came across an explanation of "galvanic corrosion". The idea being that some metals cause corrosion simply from being in contact with each other. (I was interested in stainless steel plates being screwed to galvanised steel hinges, which was apparently a very bad idea.) Is there any possibility that bronze bushings are coming into contact with some other metal that causes corrosion and that corrosion is then rubbing away at the steel shaft?