Motor Bushing Lubrication

[Otis311]

I'm wondering what you all are doing for lubrication of bronze motor bushings. I try to put a drop of oil on the exposed endbell bushing before every run. I don't however make it a habit to regularly lube the output shaft bushing due to lack of easy access. I will always oil it before initial install and if it is ever out for maintenance. Does anyone lubricate both bushings every session? Is it even necessary to oil these bushings regularly anyway? For the most part I am dealing with silver cans so not really worried if they wear out but not prematurely if possible. Tamiya uses bronze bushes in some more expensive open endbell motors too and they are worth preserving. Thanks in advance for any input.

[markbt73]

The reason bronze is used for bushings, as I understand it, is that bronze absorbs oil, so if you oil them once, they're good for a good long time. I usually add a drop of 3-in-1 oil on each bushing when I build the kit, and then just leave them alone.

However, on used motors, I have solved bushing "chatter" by adding a fresh drop of oil. I have done this with the motor running on a test stand before, and you can actually hear it smooth out and speed up.

Over-oiling probably won't hurt anything, but it has the potential to make a mess, and it's wasteful. Think of it this way: these are industrial motors repurposed for RC cars. How often do you think the fan motors in a printing press (which I have seen 380 and 540 motors used for) get oiled? If you guessed never, you'd be right.

[Juggular]

Yes, that's an awesome idea.  I use motor oil. 

When I did a test, a drop of light machine oil increased RPM immediately like 100RPM (if I remember correctly).  I didn't use motor oil at that time. And that was at 3.7v.  You'd gain more RPM at 7.4v.  So I'm all for lubricating the bushings.  The pinion-side is hard to get to.  10-30w motor oil is thicker than machine oil.  But it should last quite a long time.  After all, it was designed to protect 1:1 engine's crankshaft for 30,000 miles.  A drop of motor oil should last at least 300 hours of running. (Basically for the life of the kit)

 

I have a box fan that's running 24 hours for 365 days a year (to remove radon).  It also has bushings. I lube the shaft with motor oil every 3-4 months. That's every 2000--3000 hours.  If I don't lube it, it would seize in about 18 months. By then, there would be a noticeable gap between the shaft and the bushings. Just like some 540 motors I have, which won't run anymore. (They came with used chassis.)  I doubt that bushings would go that bad if motor oil was used.  

This fan ran for about 26,000 hours (3 years continuously). It runs as good as new. I forgot to write down the dates for the first and second lube.  Since the 3rd one was January 2022, I think I got this fan in 2021.  

Before this fan, I had tried Tamiya ceramic grease, various machine oils, my favorite teflon greases and SuperLube.  But 2 other boxfans before died within 3 years.  There were 4 other smaller fans that also didn't last 3 years.  3 years is still twice as long as not lubing.  But the best seems to be a drop of motor oil every 3-4 months. (sometime I went 6-7 months between lubes.)  

Why doesn't Mabuchi ship it with semi-synthetic motor oil?  Most Tamiya kits don't come with bearings. My guess is that they want the least viscous oil, so the motor can run as fast as possible, even if the bushings don't last as long.  Besides, synthetic oil is too expensive for a $5 motor. 

If I get a new bottle, I'd get thinner 5-20w.  But this $2.50 bottle I got 8 years ago will probably last for the rest of my life. I use one drop at a time with a toothpick. 

For most of us, a silvercan without additional lube will last seasons. And it's not an expensive motor to replace.  But lubing would help.  If you are worried about not being able to get to the pinion side, use motor oil only on that side of the shaft. So you won't have to lube again.  And the tail end can be lubed with lighter oil every season. Or use motor oil on both ends and forget about lubing for the next 300 hours. 

 

[alvinlwh]

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[Otis311]

Good points made here.

My motivation for this question was two fold. Firstly, the oil is indeed making a bit of a mess. A drop every session seems to be overdoing it. There is a lot of residual oil film on the outside of the can, and likely inside, that collects fine dust. Maybe I will reduce the application to one drop when a vehicle is taken off the shelf for the first time in a long while. I had figured the bushings were a sintered metal, like Oilite, based on their appearance. Nevertheless, I thought the extra lubrication couldn't hurt, but it actually may be if it is fouling up the innards of the motor. A little bit goes a long way, especially with the synthetic engine oil I am using, much like Juggular is using in his application.

The second motivation for this question is that the two vehicles with basically new Torque Tuned motors are making a noise that I attribute to the motor. It is the classic "chatter" sound of a shaft spinning in a bushing that is worn or dry or both. It's that nasty squealing/shrieking sound and it seems to be at a frequency that matches the motor rpm. It also is most noticeable at very light loads and goes away under heavy acceleration.

It just seemed odd that a new motor would behave this way. Wasn't sure if anyone else is experiencing this.

[Pylon80]

3 hours ago, Otis311 said:

Good points made here.

My motivation for this question was two fold. Firstly, the oil is indeed making a bit of a mess. A drop every session seems to be overdoing it. There is a lot of residual oil film on the outside of the can, and likely inside, that collects fine dust. Maybe I will reduce the application to one drop when a vehicle is taken off the shelf for the first time in a long while. I had figured the bushings were a sintered metal, like Oilite, based on their appearance. Nevertheless, I thought the extra lubrication couldn't hurt, but it actually may be if it is fouling up the innards of the motor. A little bit goes a long way, especially with the synthetic engine oil I am using, much like Juggular is using in his application.

The second motivation for this question is that the two vehicles with basically new Torque Tuned motors are making a noise that I attribute to the motor. It is the classic "chatter" sound of a shaft spinning in a bushing that is worn or dry or both. It's that nasty squealing/shrieking sound and it seems to be at a frequency that matches the motor rpm. It also is most noticeable at very light loads and goes away under heavy acceleration.

It just seemed odd that a new motor would behave this way. Wasn't sure if anyone else is experiencing this.

The "can" motors like the TT do make an annoying noise very early on but that's not from the bushings in my experience, that's the brushes rubbing on a dirty and damaged comm.

[El Gecko]

15 hours ago, Otis311 said:

Good points made here.

My motivation for this question was two fold. Firstly, the oil is indeed making a bit of a mess. A drop every session seems to be overdoing it. There is a lot of residual oil film on the outside of the can, and likely inside, that collects fine dust. Maybe I will reduce the application to one drop when a vehicle is taken off the shelf for the first time in a long while. I had figured the bushings were a sintered metal, like Oilite, based on their appearance. Nevertheless, I thought the extra lubrication couldn't hurt, but it actually may be if it is fouling up the innards of the motor. A little bit goes a long way, especially with the synthetic engine oil I am using, much like Juggular is using in his application.

The second motivation for this question is that the two vehicles with basically new Torque Tuned motors are making a noise that I attribute to the motor. It is the classic "chatter" sound of a shaft spinning in a bushing that is worn or dry or both. It's that nasty squealing/shrieking sound and it seems to be at a frequency that matches the motor rpm. It also is most noticeable at very light loads and goes away under heavy acceleration.

It just seemed odd that a new motor would behave this way. Wasn't sure if anyone else is experiencing this.

I picked up a used Sport Tuned awhile back that does the same thing. It looks brand new from the outside, but at slow speeds it screeches and wails like a banshee. I tried some Tri-Flow bicycle lubricant because it has Teflon, and the squeak came back within a few runs, so I'm guessing it evaporated rather quickly. Same when I tried 3-in-1 oil. Never had any issues with my normal silvercans, so I'm not sure what's different about the ST. Different bushing material maybe?