Tech Tip #205: Building Your Own PTO Support To Minimize The Damaging Impacts of Sideload

We often hear from people using mechanical power take-off clutches from Twin Disc, Rockford™, NACD®, or WPT Power® in heavy duty or intense applications (ex.  tub grinders or wood chippers).  Sometimes they are trying to understand why their PTO, clutch pack or bearings failed to make sure they care for their investment and minimize their downtime.  Often, the issue is that their application is putting too much side-load on the output shaft of their PTO.  When this happens, it can cause the shaft to rotate out of alignment putting excess force on the other PTO components, which in turn overheat, wear and then fail.  This failure can even extend to the engine flywheel, pilot bearing carrier or even engine main bearings in extreme cases.

Excessive side-load on a PTO output shaft can be caused by any number of factors. Maybe the PTO was never spec’d properly for a side-load and pulley application so it wasn’t designed to handle the forces it is being subjected to.  Maybe there are too many pulleys or they have been over-tensioned, putting more force than intended on the PTO.  Maybe the equipment manufacturer thought that by using an undersize pulley they could get more power out of the engine at the expense of pushing the PTO to the edge of its sideload capabilities.  Whatever the reason, side-load is a common issue that needs to be thoughtfully managed to maximize the life of your PTO.  One way to help minimize sideload on your PTO to by using a properly designed PTO support or cradle.

In Foley Tech Tip #147: Running a Twin Disc/Rockford PTO? Want It To Last Longer? we discussed a PTO cradle system that could be fabricated to help minimize twisting from high side-loads.  This Foley Engines Tech Tip goes a step further, by providing a drawings and some possible dimensions to use when fabricating a cradle support plate for some of the larger PTO’s with 14″ to 21″ friction discs.  The same concept can be used down to PTO units with 11″ discs as well, but the dimensions will need to be sized for your PTO.  Below we reference Twin Disc model number, but the concept applies equally to Rockford, NACD and WPT Power unit even if the measurements are slightly different (ex.  a Rockford, NACD or WPT Power unit with three 14-inch discs or two 18 inch discs will generally require the same kind of support as the respective Twin Disc 314 or 218 unit respectively).  In any case, this one-piece support plate should give you even better sideload support than the two pieces we discussed in Tech Tip #147 and the dimensions should make it easy for you to weld one up to fine-tune for your application and PTO.

Mechanical PTO Side-Load Support Plate For Larger 14″ to 21″ Power Take-Off Clutches:

We recommend that you use Grade 8 bolts or better and at least ½” steel plate for the support.