As I know, independently mounted and operating unbalanced motors automatically tend to run in phase. Therefore, possibly they may not run 180 degree out of phase, if both have identical operation. This is as per my observation for vibrating feeders, etc.

Let experts comment / suggest about the solution to your problem.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Firstly I agree with Ishwar that the synchronization of unbalanced motors will automatically occur by mechanical phenomena, but with the added proviso that both motors must be attached to a single rigid member (and this last point is very important).

As to achieving the direction of linear motion?

The answer is simple but the explanation may not be, so here goes …….

If you can first picture the two unbalanced motors side by side on a flat base.

Before startup their flyweights will naturally both hang at their six o’clock position (mother gravity at work).

When the motors startup (in opposite directions of rotation), after 90 degrees one flyweight will be pointing at 9 o’clock and the other at 3 o’clock, and so will cancel each other’s forces out (there will be no unbalanced force generated in this east west direction).

After a further 90 degrees of rotation however both flyweights will be pointing at 12 o’clock, and their out of balance forces will combine to produce a force in that (north) direction.

This process is repeated in that after a further 90 degrees of rotation when at 3 o’clock and 9 o’clock the flyweight forces cancel each other out again, and then at 6 o’clock both flyweights generate the unbalanced force in a southerly direction.

If you can picture this, the next step is to rotate the base that both motors are on so that it is laying at an angle which is at 90 degrees to the direction of vibration (angle of attack) you require …. and bingo you have liftoff. ■

Referring to my reply, the vibrating feeder tray for mounting of these motors was at the back of my mind, so I missed to mention this point. Thanks to Mr. John for noticing this point. I am correcting my earlier reply as under

Two motors of identical rpm with unbalanced mass, and both mounted on oscillating (vibrating) common member would tend to run in a synchronized manner.

It seems that the phenomenon is similar to two numbers of identical balls placed in a box and when the box is shaken horizontally, both the balls will tend to move in synchronism. This is due to reason that their motion is consequence of oscillating motion of the box, which is common for both the balls.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

I am not sure that I understand your concern … but let me try

When “at rest” the position the motor flyweights will always naturally fall to the 6 o’clock position (on the vertical center line).

However because we have rotated the position of the motors, the flyweights will automatically synchronize during operation (due to the mass effect principle) to achieve a linear motion at the angle of attack you have set up for.

Your 30 degree angle of attack is common for most vibrating feeders (it’s usually a steeper angle for screens), and so if you look at any linear motion feeder using unbalanced motors you can notice the motor position rotation that you are after.

It does take a bit of getting the brain around at first, but be assured that it does work without any need for smoke or mirrors. ■

This may help illustrate. XL discussion.

Shaft above horizontal vibrating screen with counterweighted shafts with heavy and light sides.

These machines actually come out of the shop at a 45 degree timing angle. Stroking the machine by timing the shafts.

If you are talking about an INVICTA motor type setup that of course is different. With a sep motor on each side with their own offset pie weight counterweights.

Attachments

types of vibrating screens 2 (ZIP)

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HERE we work with separate INVICTA type motors, one on each side.

We have 1/2 moon pie weights on each motor on each side. With all weights on heavy side (6 oclock) we obtain the most stroke and conversely, if totally offset, to simulate a FULL MOON, we would have a concentric shaft simulated and no stroke. ■

Steelforbrains

Unbalanced motors shall selfsynchronise - if you want to run then out of phase you can do that electronically. Some screens manufacturers do that when they use 2 circular motion mechanisms and want to control the elliptical shape of stroke.

regards

Ziggy ■

Rob

Both arrangement can be used - the only difference is that in case of failure of one of the unbalanced vibrators bottom arrangement will cause excessive side movement but if you have sensor installed to controll vibration than is does not matter.

Regards

Ziggy Gregory ■

see pic of 2 motors on this feeder/screen box ■

invicta motors ■

the attachment shows as accepted.......but, does not show up.

forget it. ■

still did not work. sorry. VERY FRUSTRATING. and time consuming. ■