Greetings from the slowly defrosting "easteern Wilderness,"

I have conveyors bounce a lot in the mine where I worked-it all ended up being due to belt overloading and the resulting stretching and rebound of the rubber belt from start up torque and speed switches etc.

The other thought that comes to mind is belt stretching with age as well- when is the last time you had a new belt or new splice on that conveyor?

signed, curious in the "Eastern Wilderness" ■

A very interesting problem.

I did experience a similar problem but not to that extent. We had a slight bounce at the head end.

I traced it out and found the the top fold cylinders were bottoming out before the frames came together. This created a slight bounce from the hydraulic cylinders. We simply shimmed the truss frame until the frames bottomed out before the cylinder bottomed out. Problem went away.

May be something for you to look at.

Also I would assume that your drive is on the return side of the belt creating approx equal belt tension on carry and return belt around the head pulley. But is the drive located toward the head end of the tires or towards the back end from the tires.

The tires are the pivot point and if the drive is not positioned properly within the system, it may cause the head end to pull down if the drive is ahead of the tires or can create an uplift at the tail pulley if the drive is located behind the tires. The tension drops from T1 to T2 after the drive pulley and the forces change.

You will need look at the geometry and the loads created by the tensions to prevent any uplift at the tail or pull down at the head end. The drive need to be located to balance these tension forces.

Hope this is helpful. Let us know if you solve the problem.

Regards, Gary Blenkhorn ■

I forgot to mention that the tension forces need to be calculated with a full load of material on the system.

I just ran a couple of quick calculations on your tension and came up with the following.

Based on 36" x 130' (assuming max of 18 deg incline) and 400TPH of minus 2" stone.

The tension are calculated at.

unloaded T1=1350 lbs.

T2=850 lbs.

loaded T1=4500 lbs.

T2=2000 lbs.

Note the change in differential between T1 and T2 when loaded.

This could very well be your problem.

Good luck

Gary Blenkhorn ■

Does the bounce happen at all flow rates or just at full capacity?

Is the bounce in the support structure or between idler spacings?

Is the take-up fixed or gravity?

What are the idler spacings carry & return?

WHat is the idler roll diameter and trough shape? ■

Dear sir



It is a fixed stacker tyre monted with 130 foot long boom with additional support at centre.

Conveyor is not fixed to ground which in turn is tyre monted.

Due differential forces at head pulley there may be uplift and downward forces at tyres of machine.

As boom is 130 feet long slinght uplift/ down ward movement of tyres is amplified at boom end which is 130 feet long.

If you send me sketch of stacker we can findout exect effect on boom discharge pulleydue to per millimeter downrad/ upward movement of tyres on grond

A R SINGH ■

Most things in this life run with some out of balance load.

Most structures have a natural frequency.

Seems to me you've managed to to get the frequency of the out of balance load at the natural frequency of the structure. Might be worth changing the speed of the conveyor a bit.

We once did a vibrating conveyor job and got the frequency of the conveyor more or less the exact natural frequency of the building and started loosening some of the masonary. Had to change the speed of the conveyors, but luckily we had advised the client of our operating frequency before supplying the goods. ■

Quantifying the amplitude, even without a walkway, at the discharge end is not giving the picture. What is happening at the axle & the loading point?

But it does look like case of belt stretching. ■