Design of flat belt conveyor

This URL looks like a good place to start, an engineering view of crown.

I found it with a google search of "pulley crown", the 5th hit, so not hard to find.

Richard

SBAER wrote:

I am an engineer, I do machine design on a contract basis mostly automation equipment. I have to design a flat belt conveyor (something the customer normally just purchases) about 10" wide and 24" long. My question concerns the crown on the pulleys. Does the tail pulley have to be crowned as well as the head pulley? I prefer to approximate the crown by turning a slight angle on each end of the pulley so that the machining can be done on a simple lathe. Does anybody have a suggestion as to the angle and length of this chamfer? My four year engineering education did not cover this (or anything else that might be of use to a automation designer) and none of my handbooks have do either.

Any help would be appreciated.

stan

Here's some info from Habasit, you could probably find more on Shingle and Siegling's websites...

You can purchase crowned conveyor pulleys with QD hubs from Van Gorp. Van Gorp used to be part of Browning and Emerson Electric-that doesn't appear to be the case any more.

If the 24 inch length is not a misprint, one crowned pulley should be adequate.

Ned Simmons

SBAER wrote in news:h8ydnQ2GgYKOzWXcRVn- snipped-for-privacy@rogers.com:

Cross posted to AMC where Koz may be able to help you out. He may even be able to get you the exact conveyor you need, without you having to design it.

Stan, where are you located? Ive got a Shitload of stuff for conveyor systems that I need someone to haul off.

Gunner

"Gunner, you are the same ridiculous liberal f--k you ever where." Scipio

sure does

I prefer to approximate

I usually used 1/2 a degree. You get better results though with a tracking strip welded onto the centre of the belt and a groove in the pulleys. Try the belt supplier for details. Tom

Sigh...nope...not a quick one.

ROAD TRIP!!!!!!!!!!!!!

Gunner

This message does not reflect the thoughts or opinions of either myself, my company, my friends, or my cat; Don't quote me on that; Don't quote me on anything; All rights reserved; You may distribute this message freely but you may not make a profit from it; Terms are subject to change without notice; Illustrations are slightly enlarged to show detail; Any resemblance to actual persons, living or dead, is unintentional and purely coincidental; Do not remove this disclaimer under penalty of law; Hand wash only, Tumble dry on low heat; Do not bend, fold, mutilate, or spindle; Your mileage may vary; No substitutions allowed; Offer good for a limited time only; This message is void where prohibited, taxed, or otherwise restricted; Caveat emptor; Message is provided "as is" without any warranties; Reader assumes full responsibility; An equal opportunity message; No shoes, no shirt, no message; Quantities are limited while supplies last; If any defects are discovered, do not attempt to read them yourself, but return to an authorized service center; Read at your own risk; Parental advisory - explicit lyrics; Text may contain explicit materials some readers may find objectionable, parental guidance is advised; Keep away from sunlight; Keep away from pets and small children; Limit one-per-family please; No money down; No purchase necessary; You need not be present to win; Some assembly required; Batteries not included; Instructions are included; Action figures sold separately; No preservatives added; Slippery when wet; Safety goggles may be required during use; Sealed for your protection, Do not read if safety seal is broken; Call before you dig; Not liable for damages arising from use or misuse; For external use only; If rash, irritation, redness, or swelling develops, discontinue reading; Read only with proper ventilation; Avoid extreme temperatures and store in a cool dry place; Keep away from open flames; Avoid contact with eyes and skin and avoid inhaling fumes; Do not puncture, incinerate, or store above 120 degrees Fahrenheit; Do not place near a flammable or magnetic source; Smoking this message could be hazardous to your health; Reading is addictive; No salt, MSG, artificial color or flavoring added; If ingested, do not induce vomiting, and if symptoms persist, consult a physician; May cause drowsiness, alcohol may intensify this effect; Read with food; Use caution when operating a car or dangerous machinery; Possible penalties for early withdrawal; Offer valid only at participating sites; Slightly higher west of the Rockies; Allow four to six weeks for delivery; Must be 18 to read; Objects in mirror are closer than they appear; Use of this message is governed by the terms and conditions of the Bank and Messageholder Agreement received by the Messageholder. Message remains the property of the Bank and must be returned on request. Disclaimer does not cover misuse, accident, lightning, flood, tornado, tsunami, volcanic eruption, earthquake, hurricanes and other Acts of God, neglect, damage from improper reading, incorrect line voltage, improper or unauthorized reading, broken antenna or marred cabinet, missing or altered serial numbers, electromagnetic radiation from nuclear blasts, sonic boom vibrations, customer adjustments that are not covered in this list, and incidents owing to an airplane crash, ship sinking or taking on water, motor vehicle crashing, dropping the item, falling rocks, leaky roof, broken glass, mud slides, forest fire, or projectile (which can include, but not be limited to, arrows, bullets, shot, BB's, shrapnel, lasers, napalm, torpedoes, or emissions of X-rays, Alpha, Beta and Gamma rays, knives, stones, etc.); Other restrictions may apply; Contest ends 12-31-2001.To prevent damage, feel the film continuously during the showing. Do not rewind after the last showing. Return all filmparts around their proper reels, thank you.

Although there are several factors involved, the actual answer to the amount of crows is"as little as possible". Yea, that doesn't answer the question at all. Assuming the belt is nearly perfect and mostly non-elastic, crown would be approximately 1/5 of the belt thickness relative to the radius of the pulley. In addition to providing some minimal tracking, a crown is really there because most of the thickness errors and wavyness in the belt strip material occur in the outer 20% of each edge. By relieving the pressure against the pulley on these outer edges (smaller pulley diameter under the outer edges), errors in the strip at this point have a reduced effect on causing tracking errors.

Regarding doing the crown via a taper, that's called a "narrow bodied roll". Typically, 60% flat in the center, 20% tapered at each edge by reducing the radius 1/5 of the belt thickness, with some flat left over on each end so that if the belt wanders, it doesn't wander off the edge of the pulley.

Reality is, however, that belting strips tend to be elastic and require slightly greater crown than the 1/5 of the belt thickness mentioned. This becomes a subjective matter depending on so many factors that it can become a guess. It tends to be relative to the belt thickness and width. Crown should usually never be more than the thickness of the belt. However, this rule falls into the dumpster for really wide belts. Same goes out the window the other direction for small diameter pulleys: crowning the thickness of the belt may make it act weird if the pulley is a 1" diameter nosebar.

As to crowning the tail pulley, In theory you should. On most conveyors the only place to provide any tracking adjustment is at the tail and having a little crown here can improve the system so that it isn't so "touchy" to adjustment. The goal is to get the belting to come of the tail heading the right direction (square to the frame) and enter the head pulley square to the frame. People tend to neglect the return sides of the belting when designing conveyors (belt goes on a roller coaster rode) so the tail pully crown tends to be needed to compensate for errors induced by the return side.

Tracking is NOT accomplished by tensioning the belt. The only tension on the belt should be enough pressure on the drive pulley so that Friction factor of the pulley x Pressure overcomes Friction factor x Pressure of the rest of the conveyor. Anything more than that just wears things out. To track an unruly belt, Think in terms of RELIEVING tension. That is, don't tighten one side to get it to track, loosen the other side. Once it starts appearing to track OK, then start tightening BOTH sides evenly to make sure there is enough pressure on the drive to overcome the friction on the rest of the conveyor. When doing this, you may have to make some slight adjustments in tracking angle of the pulley...kind of a process of apply a little more tension to both, adjust tracking via reducing tension on one side...apply a little more tension to both process.

Even when doing all the right tracking adjustments, they sometimes seem to have a mind of their own. Assuming that everything is square in 3 dimensions and the belt is good quality, sometimes you just have to consult the voodoo gods and do whatever works.

Koz

The end user can probably get away with a stopgap solution like this, but the fabricator can't. That one in a million chance that some idiot gets caught in a "tape" that unravelled is too big a risk. All it takes is for some maintenance guy to reverse a pulley and any tape-like substance (glued well or not) will unwind over time. There are cases of glued on urethane sheets that were pre-crowned while flat that have worked though.

When you can get sued (and lose) because someone else was stupid/ removed guards/ ignored warning label with idiot symbols, etc., it's best not to vary from industry standards of construction.

Koz

Try this site