Rail mounted stockyard machines are vehicles and subject to the same behaviour as any large juggernaut ( as in Jaggernath ).

There is a rolling resistance, from distant memory 1.1%, plus the windage, for which you would have to consult the weather records. Add the gradient resistance developed by rail level variations and that is the end of the beginning.

You must be able to travel up the steepest rail dip against a head wind so that you can reach the storm anchorage. This might, will, be necessary in the severest case and the client specification will most likely contradict itself by oversight. Cross wind and rail misalignment will provide additional tractive resistance and finally the normal and worst case digging scenarios must be provided for. Worst case is always the easiest, because it overrides the normal and is desperately simple. You must be able to push the machine so that the slewing clutch slips when you are working around mid-pile. (Otherwise, what's the clutch there for? OK it's not the only reason but it helps define a digging limitation here.)

As explained, perhaps, it eventually boils down to developing one of those old fashioned tables where several load cases must be considered. Cross wind might reduce download and produce wheel slip etc. etc.

Those good old load case definitions cannot be underestimated.

Professionals from Leipzig can tell you more. ■

Originally Posted by taxaysolanki

Dear, I want to find out tractive force for the BWSR machine travelling on rail.

Pls. suggest any formulae/ reference book/article/paper to calculate traction force for any BWSR.

Regards,

Taxay Solanki

Adding to what louis has so kindly mentioned;

You HAVE to understand that a rail mounted bucket wheel stacker reclaimer is

nothing more than An ELECTRIC RAILROAD LOCOMOTIVE with a three leg pantograph

along one side!!!!!!!!!!!!!!!!!!!!!!!!!!

The weight on each axle is what provides you with adhesion which are also referred to as the

weight over drivers in steam engine discussions.

Without adhesion you have no traction, with wet rails you have REDUCED TRACTION

which REDUCES ADHESION which reduces the ability for the wheels to creep along the

rail flange way which reduces its ability to reclaim ores or stack them.

AS the axles do not have sanding boxes to aid in traction you are already in trouble if the alignment and

geometry of the rails is not maintained.

IF AND ONLY IF these machines had a rack drive system and a smaller geometry with booms that are shorter and lower

to the ground we would never have to worry or discuss these issues.

IT all comes down to what is the opportunity cost ?, which is "what are you willing to give up to obtain something else." ■

From memory (since I am not where I can look it up), use a friction factor of 0.15 for a steel wheel driving on a steel rail. For the various corner load distributions and total tractive effort required in each case, this will determine how many and which wheels to drive and the power to each wheel.

Joe Dos Santos ■

Hello,

To know about the tractive force for the travel of the machine, one has to firstly calculate following forces arising in machine. Some of the forces can become helping (negative resistance) when machine is traveling in forward direction, but same will become opposing force (positive resistance) when machine is traveling backward (towards conveyor tail end). Some of the forces will be positive resistance for either direction of machine travel. Some forces like wind can be from any direction. So their worst influence to be analysed as helping force and alternatively as positive resistance.

The tractive force for the travel of the machine is made up of following forces:

1) Conveyor main resistance for tripper zone i.e. f.g.Lt (Mm + Mb + Mc).

2) Idler tilt resistance, if applicable.

3) Pulley turning resistance.

4) Pulley wrap resistance.

5) External scraper resistance.

6) Skirt-board resistance.

7) Material lift resistance.

8) Machine rolling resistance including crabbing if / as applicable.

9) Cable reeling drum resistance.

10) Wind resistance.

11) Slewing resistance component along rail track, during reclaiming.

12) Rail track localised gradient resistance (as per accuracy of track).

Sum of forces sr. numbers 1) to 7) is actually dragging force exerted by belt on machine. So this force is always towards conveyor head end. Thus they become helping force to travel motion when machine is traveling from tail end to head end. However they will become resistance when machine is traveling from head end to tail end.

The machine rolling resistance will always be opposite to travel motion. Cable reeling drum resistance can be either way depending upon machine location with respect to central fixed supply point. The machine reclaims during forward motion only. So slewing resistance arising due to stockpile reaction will act during forward travel of the machine. The localised gradient resistance can be either side. Similarly wind resistance can be in either direction i.e. negative resistance or positive resistance.

In addition to above, the travel drive size (or drive inherent starting characteristics) should be able to accelerate the machine, the traditional value upto 0.5 m/second square i.e. accelerating force upto 5% of machine mass.

The calculations of this nature are proprietary information of machine designer / manufacturer and may not be available.

The forces direction, etc. are mentioned in above description in context of regular stacker-reclaimer machine bucket wheel on boom, and not for reversible type machine or reclaimer alone.

Ishwar G. Mulani

Author of Book : Engineering Science And Application Design For Belt Conveyors (new print November, 2012)

Author of Book : Belt Feeder Design And Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

Hi,

Your reference #1 should be adequate for all queries.

#2 & #3 mainly concern excavators which are much larger machines and generally confined to the Iron Curtain where expense and ecology didn't matter.

As I recall, and you will have noticed, there was a proposed model classification based on bucket wheel diameter suggesting that manufacturers really imagined that they might sell in numbers. Their crowding glory didn't stand the test of time.

A troll through these forums will probably be your best solution for explaining more recent developments. ■