Thinking in Circles? A Hypothetical Question

[Maineiac]

Here is an odd thought I had while plowing....

Many of us have fluid in our rear tires to add weight. At some rotational speed, the friction of the fluid against the inside of the moving tire will cause the fluid itself to begin moving.
Now, my tractor's top speed is something like 11mph, so I don't imagine there is much--if any--effect from this circumstance. But couldn't this cause some very strange balance situation if the rotational speed was high enough?
(Perhaps there is a math and fluid dynamics expert among us who could calculate the approximate rotational speed at which the fluid would be flung around the inside of the tire. /forums/images/graemlins/crazy.gif It must be a fairly high number.)

 

[ronjhall]

In my previous life before retirement I worked a a Field Technician for the largest manufacturer of Automatic Tire and Wheel Balancers. One of the problems we had was if to much lube soap was used to assemble tire and wheel it would cause improperly balanced tire and wheel assemblies. One of the trick used to get these bad assemblies off the line was to increase the Balance cycle time. The liquid would distribute inside tire equally after they reached 300 rpm for about 10 seconds. There would be 2 problems if they got out onto owners vehicles.
1. The liquid would turn to steam when hot. This would cause over inflation of tire. Of course you have more problems than that if your tire gets to the temperature where it will boil water. /forums/images/graemlins/blush.gif
2. When it was below freezing. Tires would thump bad until tires warmed up enough to melt ice.

 

[Donnyj]

That is very interesting. From my experience working in a automobile dealership I have found as soon as I try to balance a tire and the weight requirements change with each spin of the tire, I know to break the tire down and remove the fluid. Always the case. Everytime I always find fluid in the tires. Causes alot of vibration concerns.

 

[SnowRidge]

The things you learn on TBN. /forums/images/graemlins/crazy.gif /forums/images/graemlins/laugh.gif /forums/images/graemlins/smile.gif

 

[Bird]

</font><font color="blue" class="small">( At some rotational speed )</font>

I think that's the key, but I'm not sure just what rotational speed that would be on a tractor. I've never bothered to calculate wheel rpm from forward mph. But I've driven my B2710 at top speed (11.9 mph) with water and antifreeze in the tires, and my neighbor's 85 hp Oliver at top speed (16-18 mph) with calcium chloride in the tires and never felt anything different from driving them with no liquid in them. But, like the other guys said, you can definitely have a problem at automobile speeds.

 

[ronjhall]

It has a lot to do with the differences in the way they are balanced. Most current garage type balancers mount the tire vertical like they are mounted on a car. These machines for ease of handling in the middle of a conveyor line, position the tire horizontally.They also run at 250 to 300 RPM's. Much faster than a garage type machine. When checked for how well they were balanced they would use most of the limit that they had to be balanced to. If not more. The Audit machines would start having a high percentage of rejects. Causing the request to fix machine. /forums/images/graemlins/crazy.gif
Another concern with having liquid in a tire mounted on a vehicle is the tire is not round. There is a flat spot where tire hits pavement.

 

[Maineiac]

Just for laughs, I dug out a calculator......

A tractor tire with a diameter of 4 feet rotating at 300 rpm would be going the equivalent of 42.8 mph. My little Kioti will need some serious tweaking to hit that speed--like driving it off a cliff!

Also, a related observation is that if the fluid did catch up to the tire speed and arranged itself evenly around the circumference at high speed, it would cease to be felt as added weight at the contact patch on the ground. The tire would have the same mass as before, of course.

 

[ToadHill]

When I was in high school about 1000 years ago I worked in a auto repair shop. It was not unusual to have balance problems with tires that had water inside. While is wasn't a result of mounting solution we did find that the guy who worked mornings and was supposed to drain the water out of the compressor never did it.

 

[SkogenMe]

I realize it isn't what you were talking about but the question reminded me of a story a friend related to me from a local Cat dealer.....Somebody had bought a used wheel loader down south and brought it home. Drove it down the road one December morning and just about lost their teeth....The filled tires were filled with frozen water. The fluid was rotating with the tires but since the tires weren't full the whole unit was trying to jump into the air /forums/images/graemlins/grin.gif