Drive shaft angle

[hayden]

I've got a few implements that go klunk, klunk, klunk when fully lowered, and run smooth when raised up a bit. I think it's because I'm exceeding the max angle for the drive shaft.

Does anyone know if there are different types of drive shaft joints that can handle greater angles? For example, will CV joints handle more of an angle than a conventional U joint? My shafts are all U joint today.

I can look at reconfiguring the mounts on the implements so they are farther behind the tractor to reduce the angle, but I think this is only an option with my snow blower and I'm not thrilled about the loss of maneuverability and shift in weight distribution if I do this.

Anyone have any thoughts on how the address this?

Peter

 

[Anonymous Poster]

I'd like to add to Peter's question:

Does anyone know of any straight-scoop regarding how much a pto-shaft can be " offset", (either left or right, using sway links, etc.) and still be within "design-linits" for power transmission? I assume there are such ok/not-ok limits, at least in some design-engineer's opinion, but have never seen any reference to them.

Thanks, /w3tcompact/icons/smile.gif

Larry

 

[Anonymous Poster]

There are different kinds of PTO drive shaft joints available. Constant velocity joints for use at up to 80 degree bends can be had. This probably shouldn't be necessary if everything else is OK, unless your tractor's PTO shaft is much higher or lower than the input shafts on your implements.

One issue that is easy to check and correct is that the tractor and implement shafts should be as close to parallel as possible to evenly distribute the angles between the joints. This may require that you adjust the top link to change the implement angle. Make sure you grease the shaft joints and telescoping sections frequently.

 

[geneP]

Hayden, most modern PTO shafts are designed to prevent an "out of phase" situation, but you should ascertain that the half of each joint that is made into the shaft is aligned in a straight line with each other. Automotive driveshaft joints (the traditional rear drive type) are recommended to run less that 7 degrees out, but PTO shafts aren't nearly as critical.

Do you notice any "bucking" or signs of binding in the shaft when in these extreme positions?

 

[Bird]

Peter, you sure do arouse my curiosity. When I had the B7100, the driveline on my tiller would clatter if I raised the 3-point all the way to the top with it running, but it apparently never damaged it (of course I learned to avoid picking it up too high at the end of a row), and I've never had a problem or unusual sound with any implement when it's lowered. What implements are you talking about?

Bird

 

[hayden]

My snow blower and Patu Chipper. Both have a promounced downward slope/angle to the drive shaft when the implement is lowered. The snow blower gets worse when I tip up the back blower edge (increasing the drive shaft angle) which further suggests it's related to the angle.

So far nothing has broken or been damaged, but noise in moving parts seldom leads to a good outcome, so I'd like to fix it.

Peter

 

[hayden]

The little pamphlet that came with my drive shaft says the max angle is 35 deg if I remember correctly. As far as the drive shaft is concerned, I can't see why that 35 deg deflection can't be to the side just as easily as up/down.

 

[hayden]

I like the out-of-phase theory. I'll check. I don't know if the shafts can be rotated 90 deg and reinstalled, but I'll check.

I haven't tried to measure the angle to see if it exceeds the 35 deg limit speced for the shaft, but just eyeballing it I'd say I'm in that neighborhood.

Sounds like it's time to try a CV joint shaft.

 

[Anonymous Poster]

Your driveshaft angles are not both the same. The output shaft on your tractor and your input shaft on your implement need to be parallel. U-joints are not constant velocity and will get worse as the angles are increased. What saves you is that when the angles are the same the pto shaft will speed up and slow down 8 times every revolution but the angle on the implement (if it is the same as the angle on the tractor) will compensate and the input shaft of the implement will turn at a uniform speed. Watch for this effect when you set your mower with the front deck unusually high for the mulching effect but "something isn't right" in the way it sounds and vibrates.

 

[Anonymous Poster]

Peter, Is it possible that the problem is not in the angle of the drive shaft but rather in the length? When the impliment is all of the way down the drive shaft would be at it's max extension. The klunking that you are hearing may be flexing between the two halves because they don't overlap each other far enough in that position.
You could check this by disconnecting one end of the drive shaft, seperating the two halves and then reconnecting the end to the PTO/impliment. Lower the impliment all the way down and then align the two halves to see how much the two halves overlap each other. Your impliment owner's manual should give you min. overlap for the drive shaft.