Jump to content
nowinaminute

When bearings have too much drag and it defeats the object

Recommended Posts

I've bought a lot of bearings in the past few years and noticed quite a broad range when it comes to the viscosity of the grease inside them. It doesn't matter if I buy inexpensive Chinese ones or ones from reputable sellers (which are probably the same ones anyway lol) or even premium branded ones, it seems like some are velvety smooth and will free spin in your fingers for at least a few revolutions and then other ones seem to have much thicker grease and have noticeably higher drag when you move them by hand. 

Sometimes I find they actually put up more resistance than the plastic bearings they are replacing! I know you shouldn't judge a bearing just on how it performs without a load but I have definitely noticed a hit on performance and motor temps in some instances with vehicles that use a lot of bearings.

When I find they are particularly bad, I remove the shields with a scalpel, clean the old grease out with an ultrasonic cleaner and put some simple 3 in 1 oil in them and replace the shields, this usually results in a dramatic reduction in drag with no noticeable affect on overall performance and the oils seems to last for at least a couple of years.

Does anyone else repack their bearings in this way?

And does anyone know of a better lubricant? I've tried my usual go-to greases like Red 'n' Tacky, Tamiya, Labelle, Molykote stuff intended for printer gears etc and whilst they all improve on the gunk I've found in the problem bearings, none of them give the same performance as 3 in 1 oil so it seems illogical to use them.

Does anyone know of a more specific bearing grease that has a low viscosity and gives nice silk results? If not, I'll probably stick with the 3 in 1. It might not last as long as grease but I've had some last over 2 years now which I think is sufficient.
 

Share this post


Link to post
Share on other sites

This thread has @Juggular written all over it, he loves bearings and does this. I'm surprised he doesnt have all the Kongheads so he can sort bearings

I have noticed that some spin freely and others that are sticky like you but just use them. I know people do exactly what you do as well and it frees up the drivetrain, especially for spec racing. This comes up on rctech from time to time, people suggest things like the oil for sewing machines etc, and just a few drops. They also need to be checked quite often as they don't last as long. I hope one day I'm fast enough for things like this to make a difference to me!

  • Like 1
  • Haha 1

Share this post


Link to post
Share on other sites

When I got into bicycles, I learned of Tri-Flow brand PTFE oil. It penetrates and lubricates with some of the best, and performs well; I have seen good results with it on performance bikes carrying rather-high drivetrain loads.

Like any light oil, bearings so treated require some upkeep, but Tri-Flow is easy to apply and quite effective.

  • Like 2

Share this post


Link to post
Share on other sites

I use the steel shield type bearings and Yeah Racing's bearing oil. It's water thin on application but goes slightly sticky after a few seconds. Any bearings that see dirt and grime on a regular basis get a blast of WD40 to clean, blown out with an airline then re oiled.

I'd rather a little extra maintenance than use nasty power sapping bushings that eat axles and gear casings.

  • Like 1

Share this post


Link to post
Share on other sites

I prefer the rubber shielded ceramic bearings for hubs and other exposed bearings. I prefer metal shielded bearings in the gear cases where heat is much more of an issue. Something interesting I was told by someone who actually designs bearings is this. A packed bearing needs to be broken in before you can say how well it will run. It also needs to get up to operating temperature. When the new bearing is run, the grease heats up, and gets thin. On top of that, the excess grease will usually find it's way out of the bearing. Here's the really interesting bit he said about high speed bearings. If you use oil and it's too thin, the bearing will get too hot. This means that the races and balls will expand, and then resistance increases. And if you then add the issue of dust or dirt getting into the bearing, then everything gets to become an even bigger issue. It might seem like the bearing is running better initially, but that might not alway be the case when it's operating in heat, dust or moisture. I'm no expert, but it makes sense to me - and I can definitely tell a difference between how a greased bearing runs out of the box and how it runs after a little while.

As for the plastic bushings. They do not do anything better. A bearings intended task is not just to spin more freely. It's also a load bearing item, it aids in stability and durability. When those bushings heat up, they bind, and then they wear pretty quickly. They also collect dirt and grime, and have a tendency to not stay true. I saw a test of a DT02 a few years ago of bushings vs. bearings. On a bone stock silvecan and a 7.2v MIMH, the top speed difference was about 6 kph in favour of the ball bearings. Those were the bone stock Tamiya ball bearings vs. the plastic bushings that came in the kit.

The best way to figure out what the effect of each type of bearing lubing is, would be to speed test them. Run four or five packs through each set of bearings to make sure they are broken in, and then do a few speed runs.

I don't have the patience for it, but it would be an interesting test.

  • Thanks 1

Share this post


Link to post
Share on other sites

Great comments! I should clarify that I NEVER use plastic bushes in place of bearings as a preference, it was just an observation that some bearings end up giving you greater rolling resistance than relatively fresh plastic ones. This includes bearings that have been run in. Some definitely have a little too much grease initially which distributes itself after a while just like when you grease gears but in other instances, the grease itself is just too thick, perhaps because the bearings themselves are general purpose and not necessarily intended specifically for RC use, it's in those instances that I try and relube them.

A good example I've noticed is on my Lunchbox, both front wheels have bearings from a well known UK supplier but from different orders and I've noticed that after a roll over, one wheel always stops after a few seconds and the other will keep going for over a minute and this is still the case after 2 years of running. It might not have any effect on performance in this instance but it does illustrate how variable they can be. I imagine there would be a significant difference if you had 24 of the slower ones vs 24 of the free spinning ones in something like a tl-01

In an ideal world, I would just leave them as they are, I'm more interested in reduced wear that bearings provide as well as their better ability to stop dirt entering the gearbox than I am about any performance gains but it's nice to reduce the strain on the motor too but sometimes the opposite happens and it can be a problem because a lot of these older brushed models run quite a bit hotter simply from the fact that we now run them on 2s lipo which has a higher voltage most of the time, allows the motor to draw way more current and generally tend to have several times the capacity of the old nicads. It's in those instances that I really don't want to introduce any additional strain for the motor. No doubt even "sticky" bearings will end up being smoother than worn out and grinding plastic bushings but that doesn't mean they are optimal.

I'm definitely not a racer so it's not about gaining a few tenths of a second or anything like that, it's more to do with the fact that I like to drive my stuff quite hard and off road a lot and that tends to get things hotter anyway so I'd rather reduce the motor's work load rather than increase it.

  • Like 1

Share this post


Link to post
Share on other sites

If one bearing set on one wheel will let the wheel spin on, and the other stops after a ew seconds, then I'd say there's a bearing issue, more than just a difference in bearings. I have bearings in my Lunchbox as well, and the wheels do have enough weight to make them spin for a while, even with a light turnover. I have used the bearings from RC Bearings in the UK, and I generally find them to work well. I have the coloured ABEC 5 bearings in the LB, and use the Ceramic bearings in higher end builds. What I've also found is that the rubber sealed bearings from that company usually spins more freely than the metal shielded bearings. Just an observation, and thinking that lubrication types are not the only factor in play.

  • Like 1

Share this post


Link to post
Share on other sites
On 5/3/2019 at 7:53 PM, Jonathon Gillham said:

This thread has @Juggular written all over it, he loves bearings and does this. I'm surprised he doesnt have all the Kongheads so he can sort bearings

I have noticed that some spin freely and others that are sticky like you but just use them. I know people do exactly what you do as well and it frees up the drivetrain, especially for spec racing. This comes up on rctech from time to time, people suggest things like the oil for sewing machines etc, and just a few drops. They also need to be checked quite often as they don't last as long. I hope one day I'm fast enough for things like this to make a difference to me!

Lol... you know me well.  

The room with my computer was occupied.  Usually guests take one room, but this time uncle Roger's entire family of 3 humans and 2 dogs came from Florida to see us.  Only now, I am back to the world wide web.  (and our dog went back into that room and peed on the plastic mat for the chair to reclaim it -- gee, thanks!)  

Indeed bearings are all over the place.  I found DK308's info about grease informative.  That applies to perfectly to Tamiya's metal shielded bearings packed with grease (but I think they are too thick).  For the gearbox, they are way too thick (which is why I wash them).  Many non-Tamiya ones use heavy grease that could be suitable for roller skates taking on the body weight.  RC cars don't weigh that much.  

Little bit of rolling resistance adds up a lot.  Especially if you have 36 of them.  Plumber's faucet grease is sealing the gearbox, so I have taken the shields off the bearings entirely.  They are lubed with light teflon oil.  6 rubber sealed-bearings are used on the diff gears.  That part will get a lot of dirt, so they must be rubber-sealed. (or fully packed with grease like Tamiya bearings)  But even those rubber sealed bearings were de-greased once and re-lubed with teflon grease.  

Ym6XyDo.jpg

Konghead owners would know that these don't turn freely.  Because of a dozen gears, if you grab an output drive cup and turn it by hand, it won't turn.  But with some care, they will turn.  

If I have the money, I'd get just 4 ceramic bearings for Konghead.  Or 2 ceramic bearings for ordinary cars.  The counter gears rotate fastest, so that should have the least amount of rolling resistance.  Even after re-lubing all 24 bearings seen here, they roll differently. I sort them. The easiest turning ones get installed closer to the motor.  The slowest ones go near the wheels.  

Gear reduction means the last gears will not have much trouble turning even with the bushings.  (On the other hand, the reason why Tamiya puts copper bushings closer to the motor has nothing to do with efficiency. They do that for longevity because nylon bushings will wear out quite easily and the counter gears would get ruined by rotating with large slops)  

I use Labelle oil & grease mostly.  108 is watery light machine oil (no Teflon, but plastic safe).  After de-greasing the bearings, a drop of 108 would make them spin like fidget spinner bearings.  But as people have mentioned, light oil alone won't last forever.  So I dig a tiny dab of 106 Teflon grease with an Xacto knife, and put that in the bearings after 108 oil was applied.  The oil will thicken and slow down the bearings a bit.  But it lasts a lot longer, and still much much faster than original grease.  108 oil + 106 grease is a good compromise. 

Labelle Teflon 106 is a good over-all substitute for Tamiya grease.  Very very thin coat on gears would last decades.  On bearings too.  106 will be 3 times freer-turning than Tamiya metal shields (3 times is my guess, no concrete tests were done).  However, I want gearbox bearings to turn even more freely (hence the 108 oil).  But I might get myself a bottle of "Labelle 102 medium oil," which already has Teflon mixed in it.  (I'm not connected to Labelle, by the way. I think they have been in business for a long while, selling lubricants for scale train folks)  

kVBD7MO.jpg

 

  • Like 4

Share this post


Link to post
Share on other sites

Good stuff @Juggular

Reassuring to see a lot of your views correlate with mine. I also tend to use them without sheilds if I'm confident that dirt will not get into them, it makes a significant difference, especially with a vehicle thst uses so many of them! If you can notice a difference in one bearing then the motor is certainly going to notice a difference with 36!

I've also noticed the shields themselves can play a big part, especially rubber ones. With some bearings, they are a perfect fit and come out very easily with a craft knife, those bearings tend to spin very freely and then other ones are a much tighter fit, have more excess rubber in the inside and outside edges of the shield and make a bigger difference to the resistance than any lubricant. I wish I could say this phenomenon was directly related price/claimed quality but in reality it seems to be a gamble.

There doesn't seem to be a solid price/quality guarantee in general, some of the lowest resistance shielded bearings I've ever used were those cheapo green and brown ones from eBay (they aren't totally consistent though) and some of the worst were Mugen ones, they might as well have had snot inside!

There are different "ABEC" specs too with an Abec 5 supposedly having much better tolerances and lower resistance than an Abec 1 but again, in reality I've had abec 1 beat abec 5 and so on. 

Anyways, glad it's not just me who's concerned about the resistance! 

  • Like 3

Share this post


Link to post
Share on other sites
10 hours ago, nowinaminute said:

Reassuring to see a lot of your views correlate with mine

I think it could be an inevitable progress of RC.   

When I was a teenager, I thought about a stronger motor and battery.  "Whoa, man. That black motor looks so cool. Technigold must be so fast!" etc. etc.  Then you wonder if 3 ch radio is going to help (nope).  When ESCs came out, you'd always want a better ESC with finer frequencies.  A stronger servo for heavy Wild Willy!  Finally you give up analog radios and get 2.4Ghz.  And then a Lipo (or two...or 5).  All the aftermarket bling-blings, etc, etc.  

You to learn about how the new technology works.  After all that, though, your mind won't sit still.  It starts to wonder if there is any other way to improve.  You do 3rd shock on your Grasshopper after joining Tamiya Club.  You try slick new grease, ceramic and ABEC bearings, etc.  Eventually, the Tony Stark in you start to think, "maybe I can improve bearings."  After all, that's who we are (I don't mean Iron Men).  We love rolling things.  Aside from wheels, what's more fundamental than bearings?  Good topic you brought up, nowinaminute!  

I like those bean-bearings (green and brown like beans).  One time, I got metal shields mixed in.  The seller refunded for those 10 bearings.  So I got 30 bearings for $4 instead of $6.  The rubber shields have almost no gap. Yet, as you noticed, the rolling resistance is almost nonexistent.  

CvtVIF7.jpg?1

Below yellow bearings were more expensive and looked better. 

But they had more gaps, and the grease inside was rock-hard.  Even after washing the grease out, the shields with more gaps had greater resistance. How does that even work?  So I'm back to the bean-color bearings (I just got 40 more for $8.12). 

The bean color bearings are inconsistent. If a TC member wants to just use them, get 10 more than you need.  Install the most free-rolling ones, and keep the stiff ones for later (when you want to play with them).  

JQL3DMA.jpg

 

  • Like 1

Share this post


Link to post
Share on other sites
2 hours ago, Juggular said:

I like those bean-bearings (green and brown like beans).  One time, I got metal shields mixed in.  The seller refunded for those 10 bearings.  So I got 30 bearings for $4 instead of $6.

Score lol!

I think we have discussed the bean ones once or twice before and speculated about them. Sometimes they are branded NMB which are a relatively well regarded brand. Not sure if they are liquidated stock or recovered from somewhere or what but they certainly seem to be made to quite a good standard for the most part. I quite often get 2 out of the ten that have a black shield on one side too for some reason. All I know is, when they're good, they're really good, plenty of well regarded name brand bearings don't spin that freely by hand, especially not rubber shield ones. Even if you only got a 50% keeper rate they are a bargain! But saying that, even the less smooth ones are often no worse than some other offerings are like consistently.

I got some yellow ones a while back too. They are really not easy moving at all. I like to think I'm not SUPER choosy, quite often I relube them just for something to do, just that striving to make stuff as good as it can be like you mentioned, but in the case of ones like the yellow ones, the resistance makes me genuinely concerned about negative performance.

Interesting point about the shields, there's so many variables and sometimes it seems contradictory.

Although I often find snugger shields do cause more drag and vice versa, I have also sometimes experienced shields that they seem like they would spin freely but you can feel the bearing tighten up as soon as you put them back on and you realise it was probably the shields all along causing the issue. And I've had them so snug that I've bent the **** things prying them out (usually after snapping part of the blade off!) and had to try and straighten them again, certain they would be awful afterwards and yet somehow they have still been silky smooth when reassembled. I wonder if the depth of the grooves in which the shields sits varies too and has some significance?

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...