can anyone tell me what this thing is really really used for?

Just what you said: to balance wheel/tire assemblies. Before spin balancers, this was an accepted method of statically balancing a wheel.

-Carl

Hope its still accepted. I have one like bill's and my own tire changer machine. Static balancers do as good a job as the new dynamic units, but they are fussy and slow. Two traits that don't go well with the work you get at wally world etc.

Karl

"Karl Townsend" wrote: (clip) Static balancers do as good a job as the new dynamic units, but

^^^^^^^^^^^^^^^^^^^ When the tire shop does a dynamic balance, they add weights to the inside and the outside of the rim, according to what the computer tells them. A static balancer cannot distinguish between the two sides of the wheel.

Bill, I must take issue with your statement, in the e-bay listing, that the height of the post increases the sensitivity of the level. The bubble moves off-center according to the ANGLE that it is off, and this does not change with the height of the post. What DOES change is the DISTANCE that the level moves off center, but that does not provide balancing information. (I guess I'm just a nit-picker.)

Same here. I have a manual changer and a nice Coates as well. Balancer machines are nice BUT there are a bunch of tires you cannot do unless you either buy a dedicated machine OR a bunch of adapter hardware. So for them I use the static bubble. It just takes a brain to use it and you HAVE to pay close attention.

How do you achieve dynamic balance (freedom from side-to-side wobble) with a static balancer, which measures circumferential balance?

As I understand it, you could get away with static balance when tires were very skinny, but as they've gotten wider, it's become necessary to balance them dynamically. Correct?

-- Ed Huntress

On Sun, 6 Apr 2008 20:17:49 -0400, with neither quill nor qualm, "Ed Huntress" quickly quoth:

Correct. We used to split the weight at a certain point, halving it to either side of the rim at that one point. For larger weights, indicating a real trash tire, we'd split it in half again on either side, separating the quarter weights by about 25 degrees around the rim. This kept the dynamic imbalances to a minimum.

-- Never tell people how to do things. Tell them what to do and they will surprise you with their ingenuity. -- George S. Patton

"Ed Huntress" wrote: As I understand it, you could get away with static balance when tires were

^^^^^^^^^^^^^^^^^^^^ Correct. Also, speeds were lower, and wheels were larger, so the lower RPM placed less importance on balance.

What I was trying to say by "increased sensitivity" was that for a given amount of unbalance the bubble would move farther so that you could see it better - isn't that sensitivity?

"William Noble" wrote: What I was trying to say by "increased sensitivity" was that for a given

^^^^^^^^^^^^^^^^^^^^^^^ What I meant was that for a given amount of unbalance, the position of the bubble within its surround is the same. To me that is the SAME sensitivity. For the sake of discussion, let's take this to a ridiculous extreme. Make the post 8' tall, so you have to stand on a ladder to see the bubble. A small tilt of the balancer would move the bubble about a foot, but the surround would move with it, so you would still see very little displacement of the bubble with respect to the "bullseye." {Hit nitpick send key.}

Arnt there some adapter rings missing though?

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

I don't think so - the bottom cone is fixed in place, the top cone slides on the 1/2 inch shaft - so it ought to hold whatever wheels it was designed to hold - I don't think you could put a car wheel on it (well, maybe a very teeny tiny car wheel....) and if there were adapters, I don't have them anyway.

Anyone recognize the company? G&N Product Devleopment? they existed recently enough to have a phone number with an area code and an address with a zip code, but I can't find anything out about them

Ed Huntress wrote in article ...

On page 22, March 2002 Rod & Custom Magazine........

"Believe it or not, Goodyear uses a good old-fashioned bubble balancer to balance large-diameter, fat-tread street rod tires. Why not use a sophisticated spin balancer? There are several reasons: First a good bubble balancer is perfectly accurate. Another reason is that a spin balancers have to be re-calibrated each time they're moved. Finally, spin balancers are not designed for use on large diameter tires, and the new generation

20s definitely fall into that category. It's something to consider when balancing big back tires for your street rod."

----------------------

I realize the information is old by today's technology standards, but it DOES shoot holes in the idea that bubble balancers cannot handle wider and larger diameter tires.

FWIW, I own a Micro bubble balancer, and I have never had a comeback on wheel balance. I use it to balance oval-track racing tires, too!

The trick - also the correct procedure, according to the instructions - is to use FOUR weights......two inside and two outside......every time.

I had a difficult speed-sensitive tire vibration problem on my old Ranger and made a static tire balancer to help solve it.

Actually an upper shock mount had rusted out. The lip that trapped road salt also hid the damage. I had to replace the front spring hanger plate.

The hub adapter is a disk that seats in a machined countersink in the center hole of the alloy wheels. I tapped the center of the disk

1/2"-20 and bored a conical hole in the threaded end of the hex bolt that goes into it. It balances on an upright point made of music wire. Is that clear without a picture?

Screwing the 1/2-20 bolt in or out (up or down) adjusts the sensitivity by moving the balancing point axially towards or away from the center of gravity of the wheel. If I turn the bolt in until the wheel always tips sideways, then back it out until the wheel just barely balances, a 1/8 ounce wheelweight tips the wheel noticeably. It's so sensitive that it doesn't need a bubble. It also wore so quickly that the point needed to be sharpened after every wheel.

This was a useless exercise caused by misreading the problem but it shows how balancing works. Suspend the wheel at its exact center of gravity and it will be stable in any position. When I moved the suspension point 0.010 - 0.020 above the center of gravity the tire balanced level but a nickel (5 grams) was enough to tilt it.

The height of the stand under the balance point has absolutely nothing to do with sensitivity, just convenience.

Jim Wilkins

As a practical matter, I don't doubt that it works out in actual use, because wheels (if not tires) are not much out of balance to begin with. This is especially true with machined racing wheels and other fancy wheels. I used a simple bubble level to balance my own wheels when I was racing, back around 1970.

As a matter of mechanical principle, though, static balancing, even by distributing weights, is not "perfectly accurate." It's only accurate in terms of the circumferential balance of the wheel. If wheels didn't rotate, or if they rotated only slowly, you could statically balance a wheel so that it didn't hop up and down, and you could get it dead-nuts accurate.

If there is any inequality in the inside/outside static balance (which you can't measure with a static balancer; that's why we have dynamic balancers), the wheel will wobble, because a heavier spot on, say, the outside of the wheel or tire, even when it's perfectly balanced by an equal weight on the inside of the tire but 180 deg. opposed in rotation, will make that heavy spot want to seek the center of the tire's track as it rotates down the road. The heavier spot on the outside is pulling the whole wheel out of line, and the heavy spot on the opposite side is pulling the wheel out of line in the same way, so the wheel wobbles.

All of this works better with an illustration. It happens to be the identical situation to balancing cutting tools in their toolholders for high-speed machining. Once you go beyond 15,000 rpm or so you really need to spin-balance (dynamically balance) them. I wrote several articles on dynamic tool balancing and I wish I still had one around, because I'm sure I explained it much better there. I can't see any difference between a wheel and a toolholder in this regard but I had to ask, because I wasn't sure I was thinking of all of the implications.

-- Ed Huntress

On Apr 7, 9:02=A0am, "Ed Huntress" wrote: =2E..

The static balancer I described above was meant to spin-balance a tire as well. The music-wire point was mounted in the center of a ball bearing so it would rotate. Of course the wheel would rotate on a stationary point as well but the contact area would quickly wear, so the bearing let the point turn when friction increased.

If the tire was balanced level with a weight on the top only, when the wheel was spun that weight would pull itself toward a plane through the center of rotation and the wheel would wobble. I could mark the high spot opposite with chalk.

It did wobble but not enough to bother with, since the tire had been spin-balanced originally (and the problem wasn't imbalance anyway) so I used the 4-weight pattern, 2 oversized weights on each side spread apart to reduce their effect. I actually got the tire to run smoothly up to 65MPH with no active shock absorber.

Jim Wilkins

.It did wobble but not enough to bother with, since the tire had been

This discussion is always hampered by not having illustrations -- animated ones are best -- and I've had a heck of a time over the years discussing it just in words. But I'll try. Bear with me.

What you're describing, if I understand you correctly, is a static balancing system that makes its measurement by rotating the wheel around its axis, allowing a pointer to swing through a circle. The radius of that circle is the measure of relative imbalance.

But that's still static balance you're measuring -- the displacement of weight around the wheel, in just one plane, which is a plane that is perpendicular to the wheel axis (the axis of an axle through the wheel.)

Dynamic balance is something completely different. Some automotive tech literature actually describes it incorrectly. There are several ways to describe it correctly but I'll try an example:

Say you start with a perfectly balanced wheel and tire, and you put it on your static balancer. Now put a wheel weight in one spot on the outside rim. Now put the same amount of weight on the inside rim, 180 degrees away from the first weight. Check it with your static balancer; if you did it right, it still indicates that the wheel is perfectly balanced.

But put it on a dynamic balancer and spin it at the (typical) 300 rpm, and you'll see that it's way the hell out of whack. The wheel is wobbling from side to side like a drunk.

The reason is that centrifugal force is acting on those weights, forcing them to seek the plane of the wheel's rotation. When the weight on the outside rim is at the top of rotation, the centrifugal force vector is trying to push it as far from the axis of rotation as possible. What's "possible" is that the weight wants to swing in an arc to one side, so that it's farther from the axle. For this example, say that it's being pushed to the right.

Meantime, centrifugal force is pushing the other weight, the one on the inside rim, through a similar arc, but in the opposite direction. This one is pushing to the left. You have a "couple" of two forces pushing in opposite directions, with the axle as their center point. The two forces together are trying to bend the wheel on its axle. Resistance in the bearings prevent the two weights from seeking the largest possible circle of rotation, so the wheel has a force on it, which rotates as the wheel rotates.

That's a "wobble." You can't predict it with a static balancer. You can only measure the imbalance, and predict what's going to happen, with a dynamic balancer. You have to actually get centrifugal force working on the wheel before the forces appear. Normally a spin balancer rotates a tire at something like 300 rpm to measure these forces. Very sensitive electronic balancers only have to rotate the wheel slowly to achieve the same result.

The point of all this is that no amount of accuracy or care in setting up a static balancer is going to measure this centrifugal effect. The wheel has to be spinning fast enough to measure the side forces. Only a dynamic balancer can do it. As tires have gotten smaller and wider, this force, or couple, gains leverage and becomes a bigger factor in causing front-end shake or shimmy. It takes an expert to tell this shake from the shake you get from bad static balance, which actually is the wheel hopping up and down, but which translates, through the suspension geometry and through play in the bearings, to shakes that are hard to distinguish from bad dynamic balance.

FWIW, this is the exact same principle as static versus dynamic balance of a tool and toolholder assembly for a high speed milling machine.

-- Ed Huntress

Not going to happen. The heavy spot on the tire will still show heavy. The 180 out weight will only offset the weight you added. I proved this to someone who sells dynamic balancers by doing your exact test in front of him. Tire started off 1 oz off. Added 1 oz to just the one side. then added a duplicate weight 180 out on the back of the rim. Put it back on the bubble and guess what. It showed the tire was STILL 1 oz. out of balance.at the same spot on the rim.

And it should wobble. You have NOT balanced the tire properly.

And if you had properly used the static balancer it would show it being balanced. Like I said it requires a brain to use on properly.

I presume you mean that a longer distance up from the pivot point to the bubble increases the distance?

You can put one of these on top of the Eiffel Tower, and increasing that dimension isn't going to make the bubble move any more.

Hey, Steve, take a look again at the example. I said that the wheel and tire started out PERFECTLY BALANCED. In other words, there was no "heavy spot" to begin with in the example.

In your example, the two weights balanced each other, but they didn't balance the original out-of-balance condition.

Ah, it was balanced properly before we even started.

Yes, it WOULD show that it was properly balanced on a static balancer, after the two weights are put on it. But it isn't. Put it on the car, and the front end will wobble all over the place.

-- Ed Huntress