Capstan Brakes are typically mounted on a gravity counterweight rope assembly to control excessive upward motion of the take-up during a non-powered stop. The capstan boosts the gravity take-up force with a known additional rope tension.

The capstan is only applied when the non-powered stop has a belt-line geometry that both retards belt forward motion (up hill terrain) and causes additional drift displacement (downhill terrain loaded)where the downhill preceeds the uphill along the belt path. This can be visualized by observing the deceleration of a downhill section (from tail station) followed by an uphill section with a faster deceleration rate. The vertices cause belt to accumulate with high sag and maybe spillage as belt is removed from the take-up tower, often with a high impact of the take-up mass against the towere upper structure.

This type of anomoly is easily modelled with a dynamic analysis program. In extreme cases a static or rigid-body model will also give warning with a prediction of negative tensions along the belt path during a drift stop. ■

Alternatives to Capstan Brake that may be applicable:

1. Change conveyor geometry by eliminating or reducing geometry depression

2. Increase idler spacing in predicted low tension drift zone

3. Flywheel drive assy

4. Tail brake or brake after take-up

5. Increase take-up tension - also found in items 3 & 4

6. Change location of drive and take-up ■

Originally Posted by nordell

Alternatives to Capstan Brake that may be applicable:

1. Change conveyor geometry by eliminating or reducing geometry depression

2. Increase idler spacing in predicted low tension drift zone SHOULD READ - DECREASE IDLER SPACING !!

3. Flywheel drive assy

4. Tail brake or brake after take-up

5. Increase take-up tension - also found in items 3 & 4

6. Change location of drive and take-up

Will try to edit before sending in future. ■

Hello Shakee

If you like, you can use my rule of thumb, which I have found quite useful, and that is if your overland conveyor is longer than 4km, then it is usually beneficial to fit a capstan brake on the gravity take-up tower.

Cheers

Taggart LSL Tekpro ■

CDI rule-of-thumb is to use only when necessary. Most decline conveyors will not need such a device at any length.

We have applied to short horizontal 2 km conveyors as well. ■

Indeed Larry, what you say is true..

Its just that for me, the Capstans have been around for I suppose about ten years now, and have been a great help.

For the fifteen or so years before that, I have had to decide wether to use gravity take-ups or winch ones on my long overlands.

I have always preferred to use gravity, and going through all the ones I have done in the past, which ones would I stick a capstan on if I were to put them in today.

Generally I would say its the ones over 4km that I would pop a capstan in .. hence my empirical rule of thumb.

Also, I had an extendable overland conveyor. When it got to 4km long it became obvious that it could do with a capstan brake on the take-up, so I poped one in, and all is fine.

I hope this will be of some help to the others out there

Cheers

Taggart LSL Tekpro ■

I recall doing a capstan brake 17 years ago on 5 km German Creek with Laing O'Rourke. We followed this with 6 km Muja 14 years ago, also Nesher Cement about 14 years ago. Early versions were band brakes. Now all are caliper disk. New units use solenoid calipers. ■

The Capstan Brakes I use on the lighter duty long overlands are still the band brakes, as these provide a very useful one-way function, in as much as they let the counterweight go down freely, but offer the required resistance when going upwards, i.e. exactly when you need it.

For this I simply use correctly selected weights on the band brake lever arm, and there is therefore no electrics involved whatsoever (Keep it simple) I have modified the band brake lever arm arrangement by fitting a truck type shock absorber to act as a damper. This eliminates the juddereing you sometimes used to get.

Cheers

Taggart LSL Tekpro ■