Axle drag question based on an observation

[Russell Stevens]

Kart 1 - My son's Coyote FreeRoller W/T with 1.25" axle, 2 bearings, #35 chain, and a plane jane bell type clutch. Kart has unknown time on the bearings Spin the rear tires on the stand and the rear end rolls for a good while. Substantially longer then #2 and #3.
Kart 2 - '08 Kosmic T-11 with 50mm / 3 bearing / 219 chain / standard Rotax clutch. Bearings spin free but have unknown time on them. - Give the tires a spin and it turns over a couple of times quickly coming to a halt. With the rear caliper removed approximately the same.
Kart 3 - '08 Italkart Supersonic same setup as #2 with an '09 leopard clutch and new bearings. Same results as #2 when spinning the tires.

Is the extra drag from the 3rd bearing, the diameter of the bearings, the difference in axle sprocket to drive sprocket ratio? The Coyote is geared much higher then the Tags so it has to turn the clutch sprocket over fewer times when spinning the tires. I'm just curious, and am wondering if there is something on the Tag karts that I shoudl be doing differently.

Thanks
Rusty

[Walt Gifford]

That's apples and oranges, at least take the chains off.

You can't tell much with the bearings on the kart, they all spin pretty good with weight behind them.

btw if the Coyote is used it may have triflow in the bearings, I'd suggest putting in some grease.

Gif
_________________
FAA certified jet engine and aircraft technician
Nicholson Speedway class champion 2001
Yamaha KT100 Service Center
40 years karting experience

[Peter Zambos]

Hi, Russell. Just make sure that nothing is dragging on your Italkart and Kosmic. Good bearings, especially the new set on the Italkart will be full of grease that provides greater resistance when cold. When the kart starts running and gets that axle turning, the grease will warm up and will be less viscous, kind of like engine oil does in your car.
That being said, you should still check to make sure that your brakes aren't dragging, your chain is straight, there is no debris in the clutch. You'll also want to inspect between the bearing and the bearing cassette from time to time, as the aluminum can gall from time to time, preventing that joint from doing it's job and therefore binding up the axle. If all of those are fine, then that's just good, proper, sticky grease you've got there.
_________________
AP Kart Racing - wasting retirement money since 1987
L.A.D. Specialties
Italkart Supersonic V/Rotax

[Russell Stevens]

Thanks,
The Tag's are both fine. Just not the spin the tires, go make a sandwich, come back and the tires are still rolling "free" like the Coyote. From what I'm reading I believe that it's the difference in the TriFlow vs. grease that I'm seeing. Not planning on switching the TAG's to TriFlow, not like I notice a loss of power on the track (with the Rotax/Kosmic). The entire Italkart has never moved under it's own power, and is a brand new '08. No really, it's spent the past 4 years as a showroom display. I may switch the Coyote to grease, or keep running TriFlow till the bearing show slop and buy another complete set for $40. I'll check the Kosmic and see if they need a re-pack.

Seriously. thanks for the answers...
Rusty

[Walt Gifford]

Tri flow is faster on the stand but grease is faster on the track.


Gif
_________________
FAA certified jet engine and aircraft technician
Nicholson Speedway class champion 2001
Yamaha KT100 Service Center
40 years karting experience

[patrick slattery]

OK Walt, not doubting your post but would like to see something to back up the grease is faster than tri-flow

Pat

[Greg Wright]

Walt is correct!! Once a bearing is under load and up to it's operating temperature (Pretty low) grease is much better.

Tri-Flow looks really good when you spin the axle on the kart stand but means nothing, unless of course you race on the stand!!
_________________
Greg Wright
Rapid Racing Inc.
NKN Columnist & Host "Karting News Live"

I AM INDY!!

"When in doubt, gas it. It won't help but it ends the suspense."

[Russell Stevens]

Wasn't trying to pick that scab! What have I started...?

Dear Internet gods,
I'm sorry I asked.
Sincerely
Rusty

[Michael Knauf]

Having done lots of friction measurements myself I would say unless you have some data to back that up, it is BS.

I've never once seen where a grease has less friction than an oil.
_________________
Mike

[John Matthews]

How much power does it take to spin the axle by hand?

How much power does your engine have?

It's pretty likely as long as nothing is draging the difference between grease and tri-flo is nominal when it comes to racing karts. Also the difference in bearing life is probably not any real issue of consequencce.

The thing to think about is drag put on by the center bearing when the axle flexes during corner loading. Mike Clements designed a center bearing for oval karts that would keep axle flex in a vertical plane and reduce toe-in/toe-out induced by engine and breaking torque when running very flexible (aluminum) axles. On TaG karts I hold the center bearing in place with zip ties, I only bolt them tight when going to a rain set-up.

Of course if it pleases you to have the axle spin for hours on end with the wheels off the ground then tri-flo is the way to go.

Cheers,
_________________
John Matthews
Heartbeat Power, LLC.

[Walt Gifford]

[Greg Wright]

[Pete Muller]

Greg is spot on: grease is the correct lube for an axle bearing. Tri-Flow simply does not have the film strength to do an adequate job of lubricating an axle bearing.

Many years back, I had an enduro kart (Hartman chassis to be precise) where I had reworked the bearings with custom made shields (non-contact) and remachined everything to be dead square. Bearings were packed with a special Chevron grease made specifically for the size/speed/load type of our axle bearings. A single flip of the wrist on the rear axle would spin it for over 7 minutes (2 bearings though, not 3). And by the way -- absolutely zero maintenance on those bearings for an entire season of road racing.

If anyone were to see the grease in the can, they would have thought it would stop the axle in short order. That's not how grease works in a bearing though if the proper amount and type is used.

This is not my idea or knowledge -- ball bearing lubrication is a science that's been well developed for many years.

PM

[Michael Knauf]

Tests I've done were on engines with very precise torque meters. I've never tested a kart bearing, hence why I asked for the data... else I call BS.

Like I say, show me the data. We run needle and ball bearings all the time with oils and they last a very, very, very long time under high temperatures and loads. In fact all they really need is a mist for lubrication unless temperature is an issue. The oil acts to cool the bearing. Grease is actually something that is needed where very high sliding contact stress is encountered and there is not enough velocity for a film to form, like a non forced oil journal bearing. If the balls and races are hardened and the loads/speeds are with the acceptable range then ball bearings need very little lubrication. Greases are also used in very high load/high speed wheel bearings on vehicles where retention of oil would be impossible. Oil will break from the surface very quickly and cause metal to metal contacts which promote cold welding i.e. fretting, spalling and galling which will increase friction and damage the bearing quickly.

The speed and loads for kart axle bearings are far below what those bearings can actually handle. They only need a small amount of lube.

If the bearings have a continuous coat of oil they can go as long or longer than with grease. This requires frequent lubrication. Grease can go much longer between intervals before it is slung out, contaminated or sheared thin. Seen as how contamination kills these type of bearings the quickest, it is best in my mind to clean then frequently and use light oil. I used the same bearings for two years doing this, and using light oil the whole time, no grease... and I jump curbs.

I like the response of whatever you think, etc... very professional. I see so much BS on forums it is hardly even worth frequenting them except to sell something.

So show me the science, because all the science I have seen, read or measured shows the exact opposite of what you guys say.
_________________
Mike

[Russell Stevens]

Seeing how this thread has gone in an unintended direction anyway I decided to toss in my .02.

1) Fact checking some of the information presented I can say that I agree with the statement that the bearing being used are stressed far below their operational specifications. I've done some searching and across multiple manufacturers the 50mm insert mount bearings that I have found have a dynamic load rating of 4600lb-7800lb, and a maximum continuous operational speed of 6000RPM-8000RPM with some having a maxumum speed of 10,000RPM.
a) 11" diameter tire is ~34.557" circumference. 6000RPM at the axle bearings max continuous operational speed is ~196.349MPH. In actual use the bearings are turning at ~1/3 capacity 2000Axle RPM = ~65.450MPH.
b) The closesest I can find on a load rating for kart tires is ~200lb. This tire is at the end of the lever and has the most force applied to it of anything along the axle plane. This means that to load the axle bearing to it's dynamic load rating, a force ~23X the force that is applied to the tires would need to be applied to the bearing. Karts have at least 2 bearings holding the axle, and although it doesn't double the load rating because one wheel is unloading in the corners I have to think that it would be difficult for a 400lb kart to load either bearing by a factor of 10 or more while not colapsing the tire completely, or causing regular tire failures.

I do understand that there are additional torsional loads on these bearings, however I cannot see where they are significant enough to cause the bearing to run anywhere close to the maximum operational parameters for which they were originally disigned.

Thanks
Rusty