PTO Driveshaft Length Calculations

[Spudland_Dave]

How does one determine the correct length for a PTO shaft?
Just got my new Blizzard B74 and Want to set it all up...the manual is so confusing.....measure this, then measure that, divide by the day of the month, multiply by you shoe size and then covert to Metric and voila
Is there a simple/easy to understand way to determine it? Or should I just bolt everything up and have her cycle the 3pt while I hold the shaft in its relative position?

 

[RickB]

How does one determine the correct length for a PTO shaft?
Just got my new Blizzard B74 and Want to set it all up...the manual is so confusing.....measure this, then measure that, divide by the day of the month, multiply by you shoe size and then covert to Metric and voila
Is there a simple/easy to understand way to determine it? Or should I just bolt everything up and have her cycle the 3pt while I hold the shaft in its relative position?

Make sure you have at least 6" of overlap when the shaft is extended the most.
Make sure the shaft doesn't 'bottom out' when the shaft is contracted the most.
Preferably, have enough clearance to connect & disconnect the shaft to/from the tractor when it is at its shortest point.
I connect the front half to the tractor and rear half to the implement with the halves side by side, not assembled. mark the shields with a Sharpie or similar at the closest and furthest points. then decide where to cut. Cut the shielding about 1/2" shorter than the shafting.

 

[greg_g]

Remove the PTO shaft from the implement. Connect the implement to the three point hitch. On level ground, use the tractor hydraulics to lift the implement until its transmission input shaft is exactly the same height as the tractor PTO output shaft. This will be the shortest your PTO shaft will ever compress (on that implement/tractor combination).

Measure the gap between the tractor output shaft and the implement input shaft. Usually the output shaft has a groove, and the input shaft has a hole. Measure center to center. Then measure the fully collapsed PTO drive shaft. Measure from where the pin fits into the groove on the tractor end to the hole that lines up with the input shaft end. If the first measurement is larger than the second, no cut is required (provided there's still the minimum 6" operating overlap mentioned above). If it's shorter, subtract the smaller number from the larger. Add one. That's the number of inches you cut from both PTO drive shafts. Add one more, that's the number of inches you cut from both plastic shaft covers.

Measure twice, cut once.

//greg//

 

[Spudland_Dave]

Thanks to both of you for the easy to understand instructions....one of these nights I'm gonna drag the blower out and get everything setup (still waiting on some chute rotation parts).

 

[MicroPilot]

...
1.)Measure the gap between the tractor output shaft and the implement input shaft. Usually the output shaft has a groove, and the input shaft has a hole. Measure center to center.
2.) Then measure the fully collapsed PTO drive shaft. Measure from where the pin fits into the groove on the tractor end to the hole that lines up with the input shaft end.
3.) If the first measurement is larger than the second, no cut is required (provided there's still the minimum 6" operating overlap mentioned above).
4.) If (1) is shorter than (2), subtract the smaller number from the larger. Add one. That's the number of inches you cut from both PTO drive shafts. Add one more, that's the number of inches you cut from both plastic shaft covers.

Measure twice, cut once.

//greg//

Wouldn't you have to divide (4) by 2 to get the amount to cut from EACH end of the shaft?

 

[greg_g]

No. You're apparently not taking into consideration the tube-in-a-tube design of the PTO driveshaft and cover. Let's say you cut 1" off the outside tube, but nothing off the inside. Collapse the shaft to minimum length, and the inside tube hits the opposite end first. The 1" you just cut off the outside is so far meaningless. But cut off 1" from the inside, and the shaft collapses completely.

So. For the sake of argument, you've recorded a 48" shaft measurement - but only measure a 45" gap. Cutting off the mathematical 3 inches (from each) still risks binding when fully collapsed. Hence the extra inch. That means you want it 4" shorter, or 44 inches. But if you divide by 2 - that is cut off only 2 inches - you end up with a 46" shaft. It will definitely bind.

Same principal applies to the outer covering, except it's not load bearing. I shorten the covering an additional inch so I can better see to mate the two inside halves after they've been separated for lubrication.

//greg//

 

[CrazyQ]

And if the shaft is too long but you manage to get it on without noticing the pin does not snap in you will bend a yoke when it tries to compress! ARGGGGG! I hope I didn't damage anything else...