Mr. Potvin:

From your description, I assume that your problem is one where the logs are slipping on the belt, as apposed to the belt slipping on the drive pulley.

You will achieve higher friction values with softer rubber componds -- but you also experience faster wear. Depending on your conveyor design, length, incline, et cetera, the use of a profiled belt may assist the "grab" of the logs by the belt. Unfortunately, most profiled belts are are of lighter construction and would not be suitable for your application -- your belt supplier can advise.

Another option would be to add low profile bolt-on cleats, available from companies such as Flexco. The problems that may occur with this solution include the potential for the logs tearing the cleats off and an increased difficulty in belt cleaning.

Your local belt service company or belt manufacturer's representative should be able to help. If not, feel free to e-mail me and we can discuss the problem in greater detail.

Regards, ■

Dear Francois,

I see the problem in two parts: 1) accelerate the receiving belt speed to prevent slip and 2) cushion the load onto the receiving belt without damage.

This can be accomplished by regulating the number of logs being dumped at one time to the receiving belt's crossection and assure the head end of all logs to be dumped are reasonably in alignment. The the logs can be guided down a curve chute designed to give the log forward velocity equal to the receiving belt speed - no log slip on belt. The lowest chute exit position is configured just above the belt - no impact damage. this concept can be modelled with our DEM code. Pick the lengths and diameters. CDI can then tell you the chute geomtery and behavior of all logs in the chute and upon landing on the receiving conveyor.

Belt constructed with small elevated nibs or pegs, made of rubber, vulcanized to the carcass would give further benefit. The nibs support the log's irregular shape and give it grip. The nobs also provide small deflection to reduce minor shock.

Most large belt mfgs. have such product. It is also used in elevating round product up inclines. The specific nature of the log geometry and physical properties must be know to give further advice. Suggest you contact Goodyear.

Lawrence Nordell

Conveyor dynamics, Inc.

www.conveyor-dynamics.com ■

Dear Mr. Potvin,

I suggest you to mention following information, which will help for more appropriate response to your question.

1) Size of wood logs i.e. diameter & length. Also indicate size range

2) Surface nature of the logs i.e. smooth or rough. Whether with bark or without bark

3) The statement that wood logs getting transferred transversely is not clear. Whether wood log length is along conveyor length or is at right angles to conveyor length.

4) If wood logs are at right angle to conveyor length, they might gather rolling speed with delayed linear motion.

5) Your need i.e. whether you want to accelerate wood logs quickly etc.

Regards,

I G Mulani

Author - Book - Engineering Science and Application Design for Belt Conveyors.

Email : parimul@pn2.vsnl.net.in ■

Mr.Povin

I have has a similar problem with a saw mill. There logs were coming from a log deck and then beeing dumped onto another conveyor which was at 90deg. to the other. The speed of this second belt was about 600ft/min. The logs would slip as they droped onto this belt. We tried cleated belts but the cleats would simply get torn of in a very short time. We considered bolt on cleats but decided that the cleats would end up tearing the belts as the logs caught a cleat.

We are now going to try internal cleats, We have a tool that enalbles us to actuallly cut a pattern into the top cover of the belt.

This will , hopefully help to grab the logs and haul them along as they drop onto the belt. We have used this system on inclines for chip conveying with very good results. The biggest problem that my customer was having was that the logs were beeing measure by electric eye. The logs would slip two logs would be overlapped as they passed the eye, giving a falls production figure at the end of the day.

If you consider trying this , I suggest that you have a belt with at least 6mm cover, 9mm preferred. A proper cover selection is important, for ex: Good Year Stacker Cover or similar .

R.Babin ■

In my opinion the belt surface propertiesare not as important as the method of tranfer the logs.

The chute design needs to provide the initial acceleration of the logs into the receiving belt. Ofcourse this is easier to say than to do it.

A company in California used an inclined water fall type chute with spiral ribbed rollers to feed the logs into the receiving belt. I'm not sure of the belt speeds.

Antonio Reis

www.vitrom.com ■