Long ago I tried in my motorcycle tires.
They were horrivle!
I couldn't stand it any more, so a few weeks later removed them.
They were horrivle!
I couldn't stand it any more, so a few weeks later removed them.
I'm trying to understand the logic behind this. A T-Wrench spinning in zero g inside the ISS. Why is it constantly changing?I wish one of our physicist here would explain why the beads find the opposite side of the imbalance. My non-physicist brain thinks the beads would find the same side as the imbalance and make it worse.
For the same reasons balance beads find the opposite of the imbalance, nobody seems to knowI'm trying to understand the logic behind this. A T-Wrench spinning in zero g inside the ISS. Why is it constantly changing?
Could you go a bit deeper?Newton's Third Law?
Could you go a bit deeper?
I'm trying to understand the logic behind this. A T-Wrench spinning in zero g inside the ISS. Why is it constantly changing?
The object is precessing, with zero total external torque. It's generally true that the rate of precession is high for small moment of inertia I, and small for high I. About an axis through the shaft, I is large. About an axis parallel to the handle, I is small.
i) While it is rotating with its shaft nearly parallel to the angular momentum L , its moment of inertia is large, so it precesses slowly. Hence this rotation state seems approximately stable (but in fact is slowly varying).
ii) Once the precession takes the long axis (the handle) nearly parallel to the angular momentum L, its moment of inertia about this axis is small, so it precesses rapidly. In fact the precession is so rapid that we hardly notice it: it seems to 'flip' rather quickly to the
iii) next state with its short axis (high I) nearly antiparallel to the angular momentum L, it precesses slowly so that this seems 'stable'.
My next door neighbor taught physics and did research at the local university for 30 years. I asked him how balance beads work, to which he promptly explained it has to do with the relationship between the center of mass and the center of rotation. The beads will move to reduce the distance between the center of mass and the center of rotation. He offered to model it for me mathematically. I said that I would take his word for it.I wish one of our physicist here would explain why the beads find the opposite side of the imbalance.
Probably a great application for these, ginormous trucks.I just had to use some yesterday on a set of LT tires. It was for an f550 stake body truck. When I went to mount them on our balancer, the hub adapter for the trucks hub size didn’t work, it was improperly machined, so it wouldn’t slide over the shaft of the balance machine. Tried filing it but wasn’t getting anywhere so i broke a bead down of each and installed 3oz if equals beads in each, along with the proper stem cores etc.
Took it for a ride and it seemed fine, although with a full framed heavy duty vehicle idk if I would’ve felt a vibration anyway.
Our big truck guys use the same pack of balance beads in 22.5” wheel/tires. Unless they’re using a couple packs per wheel, I can’t see that being enough.Probably a great application for these, ginormous trucks.
The beads I tried worked fantastically until I went around a corner and the beads migrated to the outside of the turn, then there was an out of balance shake until I stopped and started moving in a straight line again. Beads are great for high profile tires, but not low profile. Antifreeze could be very interesting, because it would migrate in a corner, but would likely migrate right back to where it found equilibrium.They also won’t work well, if you add too little (just like wheel weights) or too much (been there, done that). People who report that DBs "don’t work” probably did one or the other and/or have some other issue with their tire/wheel combination.
Great experiment. I think series 70 series or higher profile is the cutoff. Your 60 series was the problem as the ratio to the 265 width was too much of a low profile. If you air up close to max pressure on curvy runs, it may have helped eliminate the flat spot bunching up but would make for a harsher ride.I have heard for years about wheel balance beads and wanted to try them on the Durango. My motivation was simple curiosity, I didn't have an imbalance problem to solve. I also have access to a lift, tire mounting machine, and tire balance machine at Bill's shop and Bill was curious to, so we figured we'd give it a try. All my cost would be is time to install the beads and a few bucks for the beads, so what could go wrong?
I bought some beads from https://www.magnumbalance.com after reading the material on their website. They have a bead application phone app, which works very well, which will tell you how many beads to use by tire size or tire weight. On their website in the FAQ https://www.magnumbalance.com/en-us/faq/ they state you do not need to balance your tires. Seeing this, I decided to remove all the balance weights when I put the beads into the tires.
The first trip to Bill's shop was to remove the tire weights, break one bead down on the tire machine and use a small funnel to get the beads inside the tires. The app calls for two scoops or 6.5oz in 265x60R18 tires. So I added three scoops or 9.75oz, because more is better, right? We finished the job in about 45 minutes and went for a test drive. The freeway is about three blocks away so we jumped on and drove about three miles, turned around and drove back to the shop. The beads do work, there was zero shaking, which meant the tires were perfectly balanced. This is going to be cool!
The next day I drove back to my hometown, which is 300 miles. I jumped on I-80 and started the drive at my normal 73 MPH. All was in balance, life is good. The interstate has nice long sweeping curves, this is where the trouble began. Every time I went around a curve, the shaking would begin and would last for a couple miles, then it would be all smooth again. There are a lot of curves on the interstate in a 600 mile drive. Why was this happening? Did I put too many beads in? Maybe three scoops was too much weight in beads?
Bill and I talked about the shakes in the curves and decided we would take some amount of the beads out. We had to break both beads down to get the beads out. We sucked them out with a vacuum and put one scoop (3.25oz) back in each tire. We were pretty sure less beads would be better and smooth everything out.
A couple days later I left on a 2,000 mile trip. The shaking was slightly less, but it was still there around every corner and then for a couple miles. If you exit the interstate and get right back on, there was zero shaking, but enter the first curve and the shakes begin. There are a LOT of curves in a 2000 mile drive. You also have a lot of time to think about why curves cause shaking, about 28 hours of time.
Objects in motion tend to continue in a straight line, unless acted on by an outside force. Tire beads, not being fixed to the inside of the tire, are free to attempt to travel in a straight line, until they contact the sidewall of the tire. The beads inside the tire, pile up on the outside of the curve because they want to go straight. This causes the temporary imbalance until the beads have enough time to slowly migrate back to an equilibrium distribution and the shaking stops.
Ugh, this experiment was failing, but why does it work so well in semi and motorcycle tires? Because they are much higher profile, meaning the ratio of height to width is greater. The shape of the inside of motorcycle tires also helps keep the beads in the center of the tread. The wider the tire, the worse the imbalance caused by bead migration to the outside of the turn.
We broke the tires down again, removed all of the beads, balanced the tires with wheel weights, and had a good laugh at how much time we had wasted on this experiment. However, we both agreed that it was worth the effort because we learned about tire beads!
The next weekend, I made another 2,000 miles round trip and enjoyed the shake-less drive. Bill's tire balance machine had just been re-calibrated and that thing is right on the money.
My verdict on tire balance beads is, they aren't for tires with wide footprints. Motorcycles and semis, great, but not for cars.
As an aside, I do have Centramatics on my truck and they work wonderfully, because the steel balls are captured in a tube and can't migrate.
My $.02
I don't think the flat spot had much if anything to do with the beads migrating to the outside of the turn. I think physics dominate the cause of the beads traveling in a straight line and bunching up inside the tire toward the outside of the turn.If you air up close to max pressure on curvy runs, it may have helped eliminate the flat spot bunching up but would make for a harsher ride.