Axle drag question based on an observation

[Russell Stevens]

Now on to the Voodoo science of lubrication as it refers to our use of these bearings. Quoting tests and specs based on other environments and loading conditions are all well and good, and have some merrit. I believe the best way to solve this, however, is to come up with a test that shows how the bearings are reacting to the different lubricants in our environment.

1) The test must be repeatable by any karting enthusiast with some basic inexpensive equipment. IR temp, fish scale, weights, you get the idea.
2) The test must be repeated multiple times, and at multiple sites. There needs to be a statistically relevant amount of raw data.
3) All of the data from all of the tests must be posted publicly to allow the karting community to analyze it and draw their own conclusions. No cherry picking data to support one conclusion or another.
4) Involved parties must agree on the the important test parameters, and methodology used.
5) The question(s) being answered must be defined and agreed upon by all parties in advance.

Anyone interested in working together and throwing a little scientific method at this one for the betterment of the sport?

Rusty

[patrick slattery]

I don't believe that either type of lube will not get the job done if sufficient lube is present,
But,

If Pete says its better, that is good enough for me. Pete has never led us astray with his observation IMHO

[Walt Gifford]

[Benn Herr]

Found this on the Machinery And Lubrication site.

http://www.machinerylubrication.com/Read/923/grease-oil

And from a linked page:

Grease lubrication should be used when the bearing operates under normal speeds and temperatures. Grease has several advantages over oil, including simpler and less expensive application procedures, better adhesion, and improved protection against moisture and contaminants.

Grease selection varies with the application. Factors to consider include hardness (consistency), stability (ability to retain consistency) and water resistance (emulsification). However, grease is oil suspended in a base or carrier, and when these bases are exposed to moisture or heat, they can turn into soap or carbon ash. Therefore, it may be necessary to use synthetic additives to prevent deterioration of the base.

Overfilling may cause a rapid rise in temperature, particularly at high speeds because the rolling elements have to push the grease out of the way. This leads to churning in the grease, which produces heat. Adding more grease only worsens the problem, creating the risk of blowing out a seal.

Bearings operating at slow speeds, and those requiring corrosion protection, can have their housing completely full of grease. The length of time that a grease-lubricated bearing will operate satisfactorily without relubrication depends on bearing size, type, speed, operating temperature and the grease used.

Oil is the preferred lubricant when speed or operating conditions preclude the use of grease or where heat must be transferred from the bearing. Oil is often used to meet the operating requirements of other components such as seals and gears.

Oil bath systems are suitable for low shaft speeds. To avoid frequent oil changes due to high operating temperatures, an oil circulation system can be used. At high shaft speeds, oil must penetrate the interior of the bearing to remove excess heat. An oil injection system is an effective method to ensure that oil gets to where it is needed. The speed of oil being injected must be high enough to ensure that sufficient oil penetrates the air vortex created during bearing rotation.

The frequency at which oil needs to be changed depends on the operating conditions and the oil quality. For oil bath systems, oil should be changed more often if its temperature exceeds 120 degrees Fahrenheit, or if the machine operates in an environment containing abrasives or contaminants. For circulating oil systems, oil change intervals are determined by checking oil quality to determine the presence of abrasive particles, oil oxidation and additive breakdown.

***************************

I don't think any of us are ready to put a recirculation oil system for our rear axle bearings. Besides, we don't really have a heat problem unless something is failing, in which case it won't matter what you use - the damage is done. Current axle bearings come with grease in them. They do "churn" when new and the excess grease is pushed out. Messy the first couple of runs but you know you now have the correct amount of lubricant left inside the bearing. Using oil can work okay if you have a way of getting all the old contaminated oil out. I used to pull my axle bearing once a year, pry the seals out and flush them with brake cleaner until they would roll without any rough spots. Then I lubed them up with Chain and Bar oil (it's like a tacky chain lube). They seemed to be okay but every time I cleaned them, they were very dirty. Now I just put new bearings in every couple of years and don’t worry about it. Much easier!
_________________
Benn Herr
Come see our Superkart Build Off @
http://www.lostenduros.com/?page_id=1534
beherr3@cox.net
http://www.southwestkarters.com/
http://www.lostenduros.com/
Kart Design
Chandler, Az.

[Russell Stevens]

Great article, however it doesn't address drag issues, and is geared towards machinery that is in continuous service. It also doesn't address how grease and oil behave during 10-20 minute lightly loaded run cycles, with the ability to re-oil between.
I have issues with how much of the article applies to our use, but lets take your quotes for examples.

1) Grease lubrication should be used when the bearing operates under normal speeds and temperatures. Grease has several advantages over oil, including simpler and less expensive application procedures, better adhesion, and improved protection against moisture and contaminants.
- without the context of the rest of this article it seems to be the absolute answer. We however are not running heavy equipment, cars, trucks, or tractors in an environment where it is either diffucult to re-apply oil, or corrosion is a regular issue.
2) Grease selection varies with the application. Factors to consider include hardness (consistency), stability (ability to retain consistency) and water resistance (emulsification). However, grease is oil suspended in a base or carrier, and when these bases are exposed to moisture or heat, they can turn into soap or carbon ash. Therefore, it may be necessary to use synthetic additives to prevent deterioration of the base.
- So grease is just oil suspended with other stuff to make it stay put. If oil is being re-applied between races why is there a need for the other stuff to hold it in. Is corrosion a regular problem when lube is being sprayed into the bearing regularly?
3) Overfilling may cause a rapid rise in temperature, particularly at high speeds because the rolling elements have to push the grease out of the way. This leads to churning in the grease, which produces heat. Adding more grease only worsens the problem, creating the risk of blowing out a seal.
- Doesn't pertain. I have seen seals blow out on the EZ maintenence trailer bearings when someone got to generous on the grease gun. Seen the same thing happen when my son lubed up his 4 wheeler. Have yet to see a zerk fitting on a kart.
4) Bearings operating at slow speeds, and those requiring corrosion protection, can have their housing completely full of grease. The length of time that a grease-lubricated bearing will operate satisfactorily without relubrication depends on bearing size, type, speed, operating temperature and the grease used.
- Again, Heavy machinery and continuous operation are involved in this point.
5) Oil is the preferred lubricant when speed or operating conditions preclude the use of grease or where heat must be transferred from the bearing. Oil is often used to meet the operating requirements of other components such as seals and gears.
- Yet again, this is not refering to how we are using the bearings. What they are saying is that in an industrial application, or on engine internals you want oil as it helps cool the parts.
6) Oil bath systems are suitable for low shaft speeds. To avoid frequent oil changes due to high operating temperatures, an oil circulation system can be used. At high shaft speeds, oil must penetrate the interior of the bearing to remove excess heat. An oil injection system is an effective method to ensure that oil gets to where it is needed. The speed of oil being injected must be high enough to ensure that sufficient oil penetrates the air vortex created during bearing rotation.
- Effectively by re-lubing the bearing between runs a manual oil injection system is being applied. Have you ever run a gearbox, or a rear end on a larger vehicle out of oil? I have, and there is no magical immediate failure. These are placed under much more heat, stress, and load then the chassis bearings in our karts. "Developed" a hole in the front differential cover of an off road truck I used to own. Drove it 20 miles through the mud and trails (and had to really reef on it in more than a few spots) to get it back to the trailer. Got it home, pulled it apart, and scooped the mud out of the diff. There was no apparent wear on any of the bearings, the gear surfaces, or in the trac-loc. The residual oil film was enough to lubricate and protect everything in conditions that were abnormal and extreme. (Not something I would do on purpose in that particular environment)
7) The frequency at which oil needs to be changed depends on the operating conditions and the oil quality. For oil bath systems, oil should be changed more often if its temperature exceeds 120 degrees Fahrenheit, or if the machine operates in an environment containing abrasives or contaminants. For circulating oil systems, oil change intervals are determined by checking oil quality to determine the presence of abrasive particles, oil oxidation and additive breakdown.
- Um can't get more frequent then a quick clean and re-spray every run.

If you are running sealed bearings - sure leave the grease in. You aren't thinking about the tiny bit of extra drag (or you wouldn't be running sealed bearings). If you don't want to maintain bearings on a frequent basis (although how hard is it to get a can out, squirt, spin?) grease and go. Neither side has scientifically proven that thier way is better, or that the other way is causing damage. There are a lot of articles stating the benefits of one type of lubrication over the other. There are as many posts from engineers (armchair and actual) stating facts that don't directly pertain to the bearings we use, and the conditions that we use them under.

Let me add another engineer to the mix. I just got off of the phone with my best friend. He's a mechanical engineer with over 17 years experience in the automotive industy. He has worked for a number of suppliers, and 2 of the 3 major US automotive manufaturers. He has done design work on just about every mechanical facet of the modern automotive chassis. I told him about this discussion, and before I could even get into the details, or my oppinions his response was "Grease is the way to go, unless you are re-lubricating the bearings on a regular basis, and don't have to deal with seals or a harsh environment."

To summerize:
1) Light oil will lubricate a bearing just fine if reapplied frequently. The required frequency has not been defined.
2) The questions of drag, bearing temperature, and wear when the bearing lubrication methods are tested in the karting environment is still unanswered.
3) Information from other industries, although interesting and educational has little relevance to the question at hand and how these products will react in our environment. I can quote race bicycle, skate board, and roller blade tests that show light oil is the way to go. These have about as much to do with the environment kart bearings face as an article on heavy machinery, automobile wheel bearings, or turbine bearings.

Rusty

[Dennis Tapp]

LET HIM WASTE HIS TIME

[Michael Knauf]

[Russell Stevens]

[Tim Doll]

I don't recall now who posted it, but years ago, on one of the previous (of numerous) threads on axle bearings, someone in the bearing industry posted that, under the sort of loads that kart bearings experience, bearings lubed with some lightweight lube chattered, while bearings lubed with a heavy oil or grease operated smoothly with less overall drag.

A common mistake that people make when thinking about kart axle bearings is the direction of loading. For a very simplistic example - take a kart that weighs 400 lbs, perfect front/rear and side-to-side weight distribution, and a two bearing rear axle. First grade arithmetic says each bearing is supporting 100 lbs. BUT, that same kart pulling 2+ g's in a corner is putting a side load on the bearings of twice that amount - a direction most ball bearings are NOT designed to gracefully handle. Add in weight distribution, slop (are your rear axle bearing PERFECTLY centered?), tolerances, and a 400 lb kart at max corning side load can be putting close to 1000 lbs side load on a rear axle bearing
Add to that, axle bearings are subject to large amounts of external heat (how far is that axle bearing from the brake disk?). The normal rules for ball bearing installations simply do not apply the way we use them. Do you really want to trust tri-flow to protect an overheated bearing subjected to a 1000 lb load in a direction is wasn't designed for with a race on the line?

I've failed an axle bearings in a big race - pulled into the pits when it was obvious I had a problem and saw the balls literally fall out of the bearing as I stopped .

If the question is lower bearing drag, a light oil might provide a slight improvement compared to grease in axle drag. But axle drag is maybe a .0000001% component on overall lap time - and a crappy axle lube could cost you the race.

Tim
_________________
Standard disclaimer - I'm FREE - No longer affiliated with any organization, I can say whatever I darn well please!.

Everett, Washington

[Benn Herr]

[Steve O'Hara]

Great thread guys, love the attitude! The science and theory makes for nice reading but how about I throw in some good old fashioned empirical evidence to help the discussion along.
Going back to Pete Muller's contribution to the thread I will add that when Pete decided he was going to abandon the McCulloch classes he sold me the special custom built chassis he had Hartman build for him that had a rear axle that would spin for 7 minutes with GREASE in the bearings.
Using the chassis in question I went on to win 7 Duffys over the next three years and lapped the field in every one of those races. BTW, the field usually included the likes of Kathy Hartman, Scott Pruett, Hollis Brown, Scott Overby and many other well known and successful road racers of the era.
In those three years I never once needed to service the bearings or remove the axle for any reason and it still spun for 7 minutes after three seasons of racing.
Results are what matters and winning with no maintenance is about all one can wish for.

One more simple thought on the subject... any meaningful drag causes heat and I have never found a rear axle bearing hot to the touch after a session on the track that has seals and grease but I have seen bearings with the seals removed and TriFlo or some other lightweight oil as a lubricrant come off the track smoking and turned blue... a sure sign of heat!
Steve O'Hara

[Michael Knauf]

Before this goes over a really bad cliff it might not be a bad idea to contact a supplier like SKF and get their take on it.

They might have different takes on different applications but I also recently read about Arrow team drivers using triflow over grease, and I know they use SKF bearings, as do I now.

The concentra bearings are pretty darn expensive so I'd hate to smoke them out of ignorance. I'm sure the factory guys can afford to replace them whenever, but I cannot. And I'll bet they have done some testing.

Just a thought...
_________________
Mike

[Russell Stevens]

Benn,
I'm a "fat old guy" racing recreationally in Western NY. I would be in the TAG "out for a nice Sunday drive - oh look at the squirrels, stop so we can take a picture" class if there was one. My son is in a local sealed Raptor Gold Plate Gas class.
Hope my reply to your previous post didn't come off as a personal attack. I disagree that the info was entirely pertinent to the sport, but always encourage others to make up thier own minds.
I just hate when folks state oppinion as fact, quote unknown sources as proof, and use apples to demonstrate how oranges work. These are the same type of "internet experts" who will disregaurd any emperical evidence that doesn't support thier oppinion on the subject.
The funny thing here is that I don't really care about the last 1/10th or what the best whizbang is. My original question was a curiosity on bearing size, gear ratio's, and the differences in drag caused by these factors.
Either way the oil folks will still use oil and believe they are right. The Grease folks will still use grease and call the oil folks fools. I'll continue to leave the bearings in the TAG karts as they are (grease), and squirt triflow into the rolly bits on the Coyote... I mean it's a 10+ year old chassis with inexpensive bearings... It's been working fine this way for a long time, and replacement bearings a less than the cost of ordering in Chinese food.
Thanks
Rusty

[Tim Doll]

[John Matthews]