which is better direct drive or belt drive

A few things come to mind. Is the belt drive a v-belt drive or a synchronous belt drive?

Either way, I would think that the culprit is over tensioning of the belt drive causing excessive overhung load on the stirrer shaft. This would cause the seals to leak and more then likely also reduce bearing life. Not seeing your actual application I am making an assumption that there is a bearing involved, on mixers this is not always true.

By going to a direct drive you would remove any overhung load induced by the belt drive.

Depending on the answer to the question above you could also increase the efficiency of drive and therefore not only realize a cost savings in down time and seal repair but an additional benefit of energy cost savings.

As I thought about my answer I realized that I forgot to mention. You will need to use a gear reducer to match the ratio of the v-balt drive. I would suggest that you use a inline helical gear reducer for this. Efficiency stay high compared to a worm gear reducer. Again, I making an assumption that you want to be inline.

If you go with a direct drive/ gearbox setup it will be necessary to have some type of protective device for the gearbox/mixer shaft and motor to prevent breakage in case the stirrer gets jammed. You could use a shear pin , torque limiter or an electronic overload relay. If you stay with a V-belt arrangement the belt will usually slip long before anythong breaks. If you use a toothed belt drive ( timing or HTD for example) you will need this protection. Ed Kedz

Thats a very important point Mr other Guest makes!

You would avoid the need for gearing if you use a speed controlled motor, really the point is to reduce your losses while preventing seal wear as I see it. There are several types of variable speed motor available but I think you should do your own research as to which might be best for you. CR4 has a motor section in globalspec which has lots of good info for you to start with and there is a very wide variety there as well.

If your mixer is dealing with abrasives or near abrasives ore some plastics which wear metal quickly I suggest you place a pre-seal felt washer in front of the seal to keep the powder and grit out. i've found these very effective in the concrete cutting industry where you are dealing with silicone and diamond dust.

It's a matter of the application that you are applying the direct drive or belt drive too. You can't do direct drive in every circumstance.

Another factor is costs. Direct drive is more expensive then belt drive. Cost is commonly the driving factor in that part of the decision. It is cheaper to replace a belt then it is a gear or shaft. Even if you have to replace the belt several times it is still cheaper then replacing one gear or one shaft once.

Dear Friend,

It is clearly known fact that the direct driven drive is better than the belt driven or any other intermediate due to the slippage losses, friction losses and maintenance losses.

If it is belt driven check the tension, it is usually about 1/2" depression per meter length and if it is sandwitch belt it should be 2% elingation after tightening. (mark a mtr and tighten upto stretch of 20mm.)

your problem may not be due to the selection of the type of drive but the seal area may not be ok. Check whether the shaft is worn out or there is any burr on the seatiing area.

GUESTT