This type of tensioning device is not new. It has been utilised in underground conveying. You may try to contact Mining Academy in Cracow (Poland) as they can tell you more about practicalities of its application.

Regards

Marian Otrebski ■

I have not seen it published in any literature.

Maybe, Marion could offer the references of patent number. ■

Hi,

Indeed an interesting concept but given the cost, I believe it's major opportunity will be, as has already been said, in underground mines where we often use mechanical winches as tensioning devices. One issue however is we are linking dynamically a high tension and a low tension pulley and this could cause some operating instability given that we generally use fabric belting underground and this type of belting can stretch by over 1% elastically during operation. In all applications where you could look at this type of tensioning device, the system dynamics will have to carefully looked at.

Col Benjamin

Gulf Conveyor Systems Pty Ltd ■

I have not used this concept myself . One of the references and some pictures you will find in " Przenosniki Tasmowe w Gornictwie" ( Belt Conveyors in Mining) by T. Zur ( 1974 and 1976 editions) and 1996 edition by T.Zur and M. Hardygora.

As far as I know prof. R. Jablonski and dr P. Kulinowski ( both of Akademia Gorniczo Hutnicza in Cracow ) were involved in some of the installations of that type of tensioning concept in the Polish underground mines and you will be able to find their publications on the subject. I suspect that all literature is in Polish only.

Regards,

Marian Otrebski ■

Yes, dynamics will be the big problem. I eluded to this in an earlier posting that gives you a reasonable magnitude of T1 tension difference of up to 5:1 sometimes greater and sometimes smaller.

The rate of change can be within 0.8-2.0 seconds for the range of T1 tension differences. This depends on the motor size (inertia) and belt strength (elastic modulus). ■

Clever, but contains undesirable features.

First, you have three tension pulleys instead of one.

Second, you have a dirty side belt contact with a high tension pulley.

Both undesirable points lead to substantial reduction in belt splice reliability, added pulleys will reduce overall lower mechanical availability, and will add significantly greater cost. ■

Agreed. May be good deal for underground applications.

Gravity is by the divine hand and works divinely. ■

A slight correction on the first posting - Three high tension pulleys.

Also the value R will have great difficulty with conveyors that have large T1 variations during stopping. This value could vary by 5:1 or more.

Retorically, where will the takeup travel go? How can it be predicted? ■

So far the attachment has been downloaded 48 times; there is always great interest in take-ups.

Is there any merit in, where layout permits, altering the wrap to match the loading? Sometimes it would be possible & more often it wouldn't. Suppose we "rolled" the snub drum, under g t u (or better; this thread's concept) influence, so that the wrap also matched the loading requirement. Its purely academic but mathematically possible (for a very stiff belt). Has variable wrap ever been considered or tested?

I mention the thought because I see applications, underground & in tight plant installations, for the thread proposal & just observed the particular 180 degree wrap condition. Its a condition we only encounter on smaller shorter belts but that shouldn't detract from the potential of the thread concept.

It's always gratifying to see new ideas.

(We have another new thread running wherein the conveyor steelwork drawings were not checked properly/at all. That is going to cost the punter more than a sample installation of this thread concept would cost. Such is the business we are in.) ■

Hi all..

First impression I like it ... except for the drawbacks mentioned above.

Second impression I would worry further however, about the dreaded aborted start.

With no T1 (F1) the system reverts rapidly back to rest situation with the belt behaving like the usual cracking of the whip!

At least with a gravity take-up you have the counterweight to dampen things a bit and with a capstan brake you are fine.

I reckon this system may well need flywheels or a capstan brake to make it dynamically stable.

Seems that you will not beat the simple winch take up with this one.

Cheers

LSL Tekpro ■

We perfected such a device for gravity takeups prior to the development of Springvale. I believe REI had a similar method installed at the Springvale mine in Oz. This goes back many years. ■

Morning Lyle..

Indeed I used such a counterweight many years ago for the tail horizontal gravity take-up of the 3.4 Megawatt Majuba inclined shaft conveyor.

On top of the counterweight was a rope sheave to provide two falls of rope above.

I put a special rope clamp on the non moving side rope so that as the cwt rose, the clamp contacted the sheave effectively making it a single fall of rope.

In this way the T tail / take-up tension from the moving side rope doubled when I wanted it to.

It worked fine.

Cheers

LSL Tekpro ■

We do gravity take-up boosting all the time with a captstan-brake applied to a TUP rope sheave. It boosts the counterweight force when the mass rises and can release when the couterweight falls.

This is used to control dynamic shock wave action.

My first application was to the 12 km Selby incline in 1990. REI had locked the capstan with a hydraulic motor. This was removed due to its excessive force boost and replaced with a caliper-disk brake. It did not have a one-way clutch. Others have also practiced this concept. Today it is common. ■