AR60 Pinion Bushings vs Bearings vs Bushings Thread

[TheScaleAddict]

Here's a discussion that has made appearances in various threads. I figured that now would be a good time to devote a thread to the topic.

So, why not use internal and external bearings on the pinion?

The External Pinion Bearing:
Should this bearing fail, the pinion shaft may be allowed to move enough that the pinion gears might pull away far enough from the ring gear (angular movement) that the pinion gears and ring gears would either 'mash' one another, or sheer one another. Typically, it's the ring gears that take the brunt of the damage. The ring gears are much more likely to sheer than the pinion gears.

The Internal Pinion Bearing:
Should this bearing fail, the pinion shaft can, and will, move in one of two, or both directions. The first is angular, similar to the movement allowed by the failure of the external pinion bearing. While the angular movement is significantly less than it is when the external pinion bearing fails, coupled with the lateral movement of the shaft retreating toward the drive shaft, the effects can be devastating. Even if you hear the failure and stop running your rig immediately, the damage to the ring gear may be so significant that it may be damaged beyond usability.

Enter Bronze (Oilite) Pinion Bushings. (TRAXXAS Bushing Set 11x5x4 TRA1243)

Immediate failure is not really possible with these. However, the bushings will 'wallow' out over time, so you should keep a close eye on the tolerances of the bushings, most specifically, the interior diameter. You'll have to pull your axles and lockers to do this. The simplest way is to see how much you can wiggle your pinion shaft around. You'll need to know how much it moves around to begin with, so make sure to do this WHEN you install the bushings in the first place.

Now, we all know bronze is a soft metal. Therefore, the bushings will wallow out faster than you might expect (respectively associate to how much power you have in your rig).

Enter Iron (Super Oilite) Pinion Bushings. (HPI Metal Bushing 5x11x4mm - B072)

Everything that I stated about the bronze pinion bushings applies here but one thing: Iron Pinion Bushings will last longer than Bronze Pinion Bushings. You'll still need to monitor them, just not as often as you would their bronze counterparts. They are not made of hardened steel, so they will not be stronger than your pinion shaft. Bushings should ALWAYS be weaker than the shaft they are supporting.

What about Friction in a bushing vs a bearing??? The friction is nominal. However, just to be on the safe side, I tend to grease the pinion shaft for added lubrication. Further, and I may be more fastidious than most, I tend to disassemble and clean my rigs after any major run if they get exceedingly dirty. Clean rigs are happy rigs. Dirty rigs will likely deal with greater viscosity where there are moving parts and lubricant. Greater viscosity leads to greater heat. Heat is not a good thing for our rigs. Cooler is better. Cleaner is cooler. You get the idea...

vis·cos·i·ty

/ˌviˈskäsitē/
Noun

• The state of being thick, sticky, and semi-fluid in consistency, due to internal friction.
• A quantity expressing the magnitude of such friction, as measured by the force per unit area resisting a flow in which parallel layers...

The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the informal notion of "thickness". For example, honey has a higher viscosity than water.


Viscosity is due to friction between neighboring parcels of the fluid that are moving at different velocities. When fluid is forced through a tube, the fluid generally moves faster near the axis and very little near the walls, therefore some stress (such as a pressure difference between the two ends of the tube) is needed to overcome the friction between layers and keep the fluid moving. For the same velocity pattern, the stress is proportional to the fluid's viscosity.


Grease, believe it or not, is a fluid. Grease mixed with dust/dirt is more viscous than clean grease. The moral of the story. Use bushings, and keep your rig clean (more inside than out).


So, why did I post all of this now? I was working toward producing a stainless steel bushing. The bronze bushings were failing too fast for my taste. My rig is more powerful than most, and heavier than most, so the stress load on the bushings is, hello captain obvious, greater than the stress load on the bushings/bearings in most Wraiths.


The product that was produced did not match the tolerance levels I had specified. Further, the cost was prohibitive to producing the bushings ($5 per sub-standard bushing). I was not a happy camper!


Enter Google. I searched more, and more, and more... I found the HPI Metal bushings! The tolerances are spot on! What's more, I picked them up for about $0.83 each. That's worth sharing. And that's what prompted this long winded, and hopefully helpful, post.


Where do you buy the Super Oilite Bushings???
Right now, eBay has the best deal on these bushings at $6.05 per package of 6 (shipped). I bought mine on Amazon. Sadly (for you), I bought all that they had in stock. There were only six packages... ;)


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[ninja turtle]

Sweet. That's for the info. I was just about to order the brass ones.

[Dostradamas]

Good info

I would go one step further (because I just cannot leave things as vague as "brass" & "metal")& explain what the 2 types of metal alloys those bushings are made of.

***Traxxas Bronze ones are Oilite:

Oilite material is the most widely used of all the types of Oilites. Standards that encompass the Oilite material are: ASTM B-438-95A Grade 1 Type II, MIL[disambiguation needed]-B-5687D Type 1 Grade 1, CT-1000-K26, SAE 841, and old SAE standard Type 1 Class A.[3]


Oilite 87.2–90.5% Copper /max 1%Iron / 0–0.3% Graphite / 9.5–10.5% Tin / 1.0% Other Elements

Oilite Plus is the same bronze alloy as an Oilite, impregnated with turbine oil and fine particles of polytetrafluoroethylene (PTFE). This reduces the friction by approximately 17% versus standard Oilite material. This material is usually used in applications that exhibit mixed-film or boundary condition lubrication. Situations where this type of lubrication is encountered commonly include oscillating motions, slow speeds, intermittent use, pulsating loads, and uneven loads.

***HPI Metal Bushings are:
Super Oilite 18–22% Copper /Balance Iron /0 Graphite /0 Tin / 2.0% Other Elements
Super Oilite is an iron based material that is harder, stronger, and cheaper than Oilite. It is rated for slower speeds, but it can handle higher loads. Common applications include farm equipment, winches, sheaves, conveyors, and pulleys. Applicable standards are: ASTM B-439-95 Grade 4, MIL-B-5687D Type 2 Grade 4, SAE 863, and old SAE standard Type 3.


Super Oilite 16 18–22% Copper /Balance Iron /0.6–1.0% Graphite /0 Tin / 2.0% Other Elements
Super Oilite 16 is Super Oilite that has been heat treated to a hardness greater than HRC 50. This material is used for extreme loads and slow oscillating motions. Common applications include cranes, hoists, machine presses, and conveyors. The applicable standard is ASTM B-426 Grade 4 Type 2.

[TheScaleAddict]

Originally Posted by Dostradamas

I would go one step further & explain what the 2 types of metal alloys those bushings are made of.

Good info.

Now... where in the heck did you get that tech information???? That's awesome!

[ZippoMan]

They should make this a Sticky!! Great reading! Thanks for the awesome info! One more thing I have to add to my list..hehehe

[rangercat23]

Great info here!
I am glad to know about the bushing option, I definitely need to look into this upgrade.

[Dostradamas]

Originally Posted by cephas

Good info.

Now... where in the heck did you get that tech information???? That's awesome!

I sell Industrial Pipe Valves & Fittings so I must know specs, alloys, blah blah blah.

I was familiar with Oilite already & Wiki has a quick, semi accurate rundown.
The pain was getting what I cut & pasted into a readable format on here.
Glad to add to a good post.

[TheScaleAddict]

I just checked Amazon. They have 3 packages left in stock. Get them while they're there... They're about half of the prices on eBay, which is the cheapest (next to Amazon) on the web that I've found.

[Dostradamas]

Originally Posted by cephas

I just checked Amazon. They have 3 packages left in stock. Get them while they're there... They're about half of the prices on eBay, which is the cheapest (next to Amazon) on the web that I've found.

Installed with plenty o' spares.

[TheScaleAddict]

Originally Posted by Dostradamas

Installed with plenty o' spares.

Spares are good. I've got about 20 of the super-oilites sitting at my bench.

[chopan84]

tower hobbies has them in stock

TowerHobbies.com | HPI Racing Metal Bushing 5x11x4mm

[Devil Inc]

Thanks for the thread/posts on this, as I'm getting ready to do some maintenance to my rigs. I have the TRX bushings in my toolbox, but I'll for sure be stopping at the LHS to see if there's any of the HPI ones in stock.

[Devil Inc]

I just picked a set of the HPI ones from my LHS and they're brass like the Traxxas ones. I wonder if HPI revised them?

[TheScaleAddict]

Originally Posted by Devil Inc

I just picked a set of the HPI ones from my LHS and they're brass like the Traxxas ones. I wonder if HPI revised them?

Are they the same part number?

[Devil Inc]

Yep, I pulled up the Tower page linked to confirm. I'm gonna check with my other LHS see what he can order.

[TheScaleAddict]

The packages I bought did look somewhat 'weathered'... Maybe HPI did change it up.

[Harley]

There is a better option around the corner...

[TheScaleAddict]

A stainless option???

[ZippoMan]

Sticky this please!! It deserves a spot on top!!

[TheScaleAddict]

Originally Posted by Harley

There is a better option around the corner...

TEASE!!!!