Mahmud,

Cast iron is often used for wheels. The loads imposed by a conveyor take up do not warrant much consideration of Hertzian stresses.

If you fix the pulley to the shaft, keyway etc, & place each outboard bearing within a reasonable diameter rope sheave you will not need a take up carriage at all. Chamfer the sheave edges and run the assembly between toes-in angle sections & you've cracked it. The clearance twixt the angle & sheave plane circumferential face is adequate for take up rope passage.

If you feel the urge to be scientific just add a figure for the extra revolutions, imparted by the take up travel, to the L10 life of the bearings.

This design removes the design tedium of stabilising a trolley, saves space, steelwork, wheels & bearings. ■

Dear John,

Can you spare a sketch? ■

Dear John,

Your ideas sounds great. How do u go with skewing prevention of the TU pulley.

I have found that using a square hollow section turned 45 degrees to form a V running surface and steel wheels machined to suit from plain carbon provide the skew guidance - which occurs and is sustained by belt mis tracking.

If U really wnat to get technical on wheel design - please refer to typical crane design codes eg AS 1418 et al.

Cheers

James ■

An article which I prepared for an Indian magazine a couple of years back is attached. I still think the idea has merit despite the Indian apathy.

Attachments

examining the gravity of take (ZIP)

■

Dear John,

Does the sheave act as the anti-cribbing device? This appears to be the case. If so, how does the small length of wheel flange, in contact with the guide rail, inhibit large belt misalignment cribbing forces? There seems to be a large mechanical disadvante to controlling guidance. If so, there would then be exaggerated wear on the sheave cheeks.

This concept would further require to have a captured sheave, top and bottom, to control its desire to jump the bottom rail. Although it might have merit, this can only be demonstrated with some in-depth analysis on its wear and tear verses conventional trolleys and guides.

Have you done the sums on belt mal-tracking action/forces with regard to wheel forces? ■

Hello Mahmud

I assume that since it is a tail take-up, the conveyor is not that long, and therefore the take-up pulley is not that heavy.

You will therefore have success by simply making the four wheels out of ordinary mild steel, without case hardening.

The best is the V-profile wheel which runs on an inverted angle iron or on square tube with apex upwards as previously suggested.

You must however allow two wheels on one side of the carriage to float sideways by 10 to 15mm, whereas the other two wheels must not have any float at all.

This compensates for missalignment of the rails.

Good Luck

LSL Tekpro ■

Dear Graham,

I know you know. Zimbabwe Iron & Steel Company (ZISCO) has a tail gravity take-up that is 16 km long. There are many more examples of long overlands with tail TUP's.

Come to think of it, when we design downhills, we often place the TUP at the head end such as at Los Pelambres up to 6 km totaling 3 flights down 12.2 km and Collahuasi maybe a little longer than 6 km.

Just a little reminder of the over 60 syndrome which I also suffer from. ■

In a diferent area of materials handling we suffered problems where material got onto a track and impared the free movement of a trolley fitted with wheels.

The solution was to reverse the arrangement, the "track" was fitted to the truck and the wheels to the fixed frame. Does this have any mileage for this type of application? ■

Hello all...

Indeed, I have climbed all over the tail take-up for the Zimbabwean 16km overland conveyor. The difference is that it has a tail drive, which I assume Mahmud's one does not have.

(I may be over 60, but I am "in my prime"...61 is a prime number you know).

Therefore assuming Mahmud's conveyor to be nothing out of the ordinary, I recommend the Vee grooved wheels on inverted angle irons as I prescribed earlier. This method also avoids material build-up on the rails.

Maybe Mahmud can qualify his needs a bit more to negate the guesswork.

LSL Tekpro ■