You need to solve a quadratic equation. Not difficult, but Intellectual property. The carry side is harder due to the trough shape.

Maybe, if you identify your affiliation by email. ■

Sorry, I did not think of this: BELTSTAT solves this condition. ■

Assuming the idler spacing, alignment with belt line (non-vertical curve), and idler shape (flat roll), the bigger roll will not carry more load.

Changes in vertical, horizontal, angular (yaw and roll), or offset due to larger roll extending above normal belt line and in transitions between trough and flat idler geometries need special analysis.

Publishing these details is outside the scope of this forum. ■

I believe an old Prok idler catalog gave a hint at a value. Again, you have to solve a dual set of equations with the solution being a quadratic equation with two roots.

You can solve it or pay for it. ■

The load on a return idler is the self weight of the roll, plus the the belt mass per metre x return idler spacing, plus the force due to the belt tension from misalignment etc.

To calculate the tension force, it is convenient to use a typical vertical misalignment of 10mm and work out the resultant extra load.

This force is 2 x cos(90-arctan(10mm/idler spacing mm)) x belt tension.

If you have a convex radius, you have to calculate the idler displacement and add it to the misalignment. This force will then tend to become significant, otherwise it it relatively small, unless on a high tension return section of the conveyor.

Regards

LSL Tekpro ■

Mr. Spriggs,

You obviously do not agree with my hint. I claim your solution is not correct. It is a far more complicated.

Your equation is simply looking at the vertical reaction of the parallelogram of forces as expressed alternatively:

Idler vertical force = 2*Tension * (y/(sqrt(y*y + Isp*Isp)) where,

y: vertical displacement (mm) and

Isp: idler spacing (mm)

I guess this is why we do not give away all IP.

Other hints?

Think about the supporting idlers. By your concept, the forces will tend toward infinity when the idler spacing tends to a small number with the same "y" offset. It is impossible to support your thesis when one considers belt sag. You assume the parallelogram of forces are fixed the "y" and "Isp" which is not so.

The reaction angle is set by the idler spacing, according to your solution. This is not true with high belt tensions "T". Your solution only partialy works when the "y" sag value does not exceed the associated idler spacing as a function of "y" and "T". The true solution is a hyperbolic function.

Your solution does not consider the material and belt mass or the trough conditions. ■

Hi Larry..

Indeed, my formula: "does not consider the material and belt mass or the trough conditions."

This is because the question was:

"Does someone have a formulae, where one can calculate the force (N), on a flat return idler, given a specified belt mass (kg/m) and tension (kN)?"

For such a fundamental question, I believe my basic formula to be quite sufficient, and has served me quite adequately for flat return idlers on low tension belts. High tension returns which are suceptible to misalignment need more attention to ensure that the belt is also carried by adjacent idlers.

Mark was looking for a "fairly accurare way" of calculating the loads.

This is what I have tried to give him.

Regards to all

LSL Tekpro ■

Dear Mr. Mark Hupertz,

It seems you intend to say that if the particular return idler is at higher elevation compared to general belt line, what should be the load on such idler? This is calculated using the belt weight kg/m and belt tension, which will create specific profile and belt inclination at the up-misaligned idler. This is standard method of calculation and is being routinely used in the design of the rollers, since very long time.

While calculating the load on idlers it is also checked that if particular idler is down-misaligned compared to general belt line, there would be additional load on the neighbouring idlers.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■