← Balanset-1A Knowledge Base — all chapters
Verbatim explanations from real tech support (dates from the chats). Useful both as a reference and as ready wording for training colleagues.
What to watch in the vibrometer
“Overall vibration — the total vibration from everything combined (imbalance + bearings + looseness + everything else). 1×RPM component — only the part of the vibration at the rotation frequency. This is the part caused by imbalance — it’s what balancing actually works with. The FFT graph shows the vibration split by frequency… If the biggest peak is at 1×RPM, it’s imbalance. If there are big peaks at other frequencies, the vibration is coming from something else (bearings, looseness, resonance, etc.).”
Three causes of unstable readings
“1. Worn bearings with play. 2. Weakness in the structure — cracks, loose bolts, loose mounting. 3. Structural resonance at the running speed. To check this, change the rotation speed by just 50–100 RPM and see how much the vibration changes. If it jumps up by, say, 10 times, then we are on a resonance or close to it.”
Resonance or looseness — telling them apart by spectrum
“A resonance usually amplifies a narrow band of frequencies, while multiple integer harmonics (3×, 5×, 6×) are the classic signature of mechanical looseness.”
The balancer’s main skill
“The most important skill in balancing is to identify a mechanical issue. In about 90% of cases, the inability to balance is caused by a mechanical fault in the machine itself or by resonance. Therefore, you need to look for loose bolts, cracks, and backlash/looseness.”
Three cases where a rotor won’t balance
“It is impossible to balance a rotor in three cases: the bearings are worn — there is play; there are cracks on the mulcher housing — even small ones; the rotor itself is deformed.”
“Practically every second mulcher can be balanced only after both bearing sets are replaced. Second place goes to housing cracks.”
“Be sure to remove the belts, take a pry bar and rock the mulcher rotor side to side. There must not be the slightest knock in the bearings. This is the most common cause of balancing problems — about 80% of cases.”
The half-mass rule
“When the device shows you the correction mass for the first time, always install only half of it. Then, depending on the result — if it suggests adding another half in the same place, you can add the second half, and the balancing will be complete. But if it starts placing weights around the circle, gradually changing the angle, or the mass becomes disproportionate to the initial half, then you need to make an adjustment. Always install half the weight the first time.”
“The half-mass recommendation is a check of the system’s behaviour. The device is accurate, but the machine may be nonlinear. If after the half the program proposes the remainder in exactly the same spot — the calculation is right. If it proposes less weight, starts changing angles, or vibration grows — look for the cause: bearings, cracks or resonance.”
“The closer you get to zero, the less you install… at that point it’s no longer a half, you can already go with 1/3.”
The trial weight
“When adding a trial weight, the vibration level and phase must change noticeably. Ideally by about 30%. If the changes are insignificant, the device has nothing to base its calculations on.”
“A trial mass of almost 300 g in plane 2 changed almost nothing — vibration went from 34.5 to 36.2 mm/s and the phase barely moved. The system practically doesn’t react to the mass, and that’s why the program calculates an absurd correction mass of 2664 g.”
“If the initial vibration had been high — say 5 to 10 mm/s — a 4 kg weight might have been reasonable. But when the vibration is near zero, even 100–200 grams can cause a noticeable spike.”
“The trial mass and the final correction mass must be placed on the same radius.”
The run sequence
“Run#0 — start the rotor with no weight at all… Run#1 — install the trial weight in Plane 1… Run#2 — move the trial weight from Plane 1 to Plane 2. Important: the trial weight is moved, not added on top. After Run#2 you remove all trial weights and install only the correction masses calculated by the software.”
“It is better to take the measurements at roughly the same speed. No more than 100 rpm difference.”
Counting the angle
“You can place the trial weight wherever it’s convenient — this point will be your reference position. From this point, measure the angle in the direction of rotation.”
“It’s like a clock face — you’re not moving around the dial clockwise; instead the whole clock is turning clockwise while you stay still.”
Resonance and choosing the RPM
“Look: in your first photos at 1300 rpm the vibration is 70. And at 1400 it’s 50. A sharp change of vibration over 100 rpm tells us there is a resonance at about 1300. I recommend balancing at 800 rpm first.”
“Starting from, say, 400 rpm, raise the speed by 50 or 100 rpm and watch the vibration level. If at some point the vibration starts growing sharply, there is a resonance at that frequency. Balancing at or near the resonance frequency is impossible.”
“The RunDown function records vibration as the rotor decelerates from operating speed to a stop… Peaks on this chart mark resonance zones. In a resonance zone the phase changes sharply — clearly visible as a steep bend in the curve.”
“Near resonance the system becomes extremely sensitive even to small speed changes. A deviation of just 2–3 rpm can noticeably change both amplitude and phase… Balance either well below the structure’s natural frequency, or above it.”
“For an above-resonance rig the working frequency should be 2–3 times higher than the natural one; for a below-resonance rig — 2–3 times lower.”
“When a customer builds a rig we always recommend fitting springs. Springs are chosen so that the rig settles slightly on them and can be rocked by hand. That gets rid of the resonances that block balancing.”
Preparing a mulcher (the full memo)
“1) Check all joints, the housing, supports and bearings — no cracks or play. 2) Tighten all bolts and fasteners. 3) The tachometer must always aim at exactly the same point; don’t move it during the process. 4) For the duration of balancing, weld the front flap and the pusher frame to the housing — that kills the parasitic vibrations. 5) The mulcher must be slightly lifted and must not touch the ground.”
“I’m quite often asked to balance a mower shaft without the knives. Don’t do that… When the customer puts the knives back, they add mass asymmetrically.”
“The weight difference between a new and a worn hammer can reach about 100 grams… Replace them as a pair: the hammer being replaced and the one 180 degrees across.”
“If vibration exceeds 40–50 mm/s I always recommend reducing the speed and balancing in two stages: first at low speed, then after the first correction raise to working speed and do the second stage.”
Tolerances and “when it’s enough”
“Anything below 7 mm/s is already good. The ideal is 4.8 mm/s… when the device shows masses below 50 grams there is no longer any practical point in adding them.”
“Mulchers don’t have rigid supports but soft ones… so their permissible vibration is higher — about 7.1 mm/s… Anything below 8 mm/s is already a good result. At a vibration velocity of about 2 mm/s you can stand a coin on its edge on a running mulcher.”
“Although we installed only half the weight, the vibration dropped far more than twofold. That shows our oscillatory system is nonlinear… This is not a device error — it is the physics of the process.”
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“For diagnosing the stability of the readings it’s better to use fewer averages [8], but for the balancing itself set 32.”
“If a second rotor spins nearby at slightly different RPM — set the averaging to maximum: the averaging is synchronised to your rotor’s tacho mark, and anything not synchronous with it gets suppressed.”
Structural resonance vs unbalance
“Normally the farther you move away from the rotor, the more the vibration decays. If, on the contrary, it increases as you move away, that clearly indicates a resonance phenomenon.”
The tachometer
“If the tachometer shows RPM but the program keeps raising a tachometer error — set Tacho Unevenness to 200 in the settings. If that doesn’t help, it may be a bad contact: unplug and re-plug the connector several times.”
“Most problems come from shiny areas on the rotor — they act like the reflective mark. 8695 and 2856 rpm — it sees three marks: 8695 / 2856 = 3.”
“When the laser beam is exposed to direct sunlight, the sensor cannot see the reflection from the tape and shows 0 RPM. That’s why it reacts to a finger but not to the tape. The solution is simple: make a shadow for the tachometer.”
