PTO shaft questions

[RedDirt]

I am converting a garden tractor snow blower to a rear PTO tph. I have a couple questions regarding setting up the PTO shaft.

I will be using a Surplus Center 15HP PTO shaft with 1 3/8 x 6T spline on the tractor end and a 1 1/4" dia smooth bore with shear pin at the blower. Ive kept the design angle of the shaft at about 7.5 degrees.

1. PTO shaft length. My current fabrication design has only 14" +/- between the crosses of the U joints. I won't know this for sure until it arrives. Is this length too short? I'd like the blower as close coupled to the tractor as possible but should I move it further away to gain more shaft length?

2. Tractor PTO shaft angle vs blower shaft angle. When the blower is at working attack angle the drive shaft angle is a couple of degrees different than the tractor PTO shaft in the horizontal (level) plane . Is it critical that both shafts be at the same angle? Seems like I read that when setting up a vehicle drive train, say a fwd truck with transfer case separated from the transmission. like an old Dodge, that all the shaft angles should be the same, front & rear axles, transfer case and transmission. Seems logical but I don't know. I also don't know if the geometry of a tph lift is a true parallelogram and the two shaft angles would not change anyway when lifting/lowering. For sure, the two shaft angles would change if the top link was adjusted. For this reason alone I'd say the two angles do not need to be equal but I'd like to hear that from someone who knows more.

Here's a PDF of my CAD plan. This plan does not show the variance between the tow shaft angles; it was discovered later. I've also upgraded to #6 gears with 1.5" gear face instead of the 1" face gears shown.

View attachment 146334d1258797473-snowblower-impeller-auger-speed-question-snowblower-gear-drive_112009.pdf

Thanks, Ray

 

[DaveOmak]

RedDirt, Great question. Got me thinking. I found this web site that is very informative. It answered my questions about my hay baler. It chatters badly when I turn a corner.
It might answer yours.
About your drive line length. In my trials, a short driveline can be difficult to hook up. Not much room between the implement and the tractor. Something to consider.
Great drawing and project. Pictures would be appreciated during the build.
Tom Wood's Custom Drive Shafts - Driveline 101
Hope this link works? Never done this before. Dave

 

[radioman]

The way I figure it, the top link only changes the angle of the implement so if you adjust it so the PTO face off the blower is 90 degrees with the ground, you can see the angles is not necessarily a true parallelogram, but the corresponding angles of lower links and TPH are created where a transversal (PTO shaft) crosses. With this line of thinking, I would say both shafts should be the same angle on level ground regardless if the blower is in up or down position for parts longevity, but with the u joints it will allow you to be at a different angle over uneven terrain.

As for the length of PTO shaft, I recommend making it as long as you comfortably can, the issue is trying to hook it up. a short shaft is somewhat frustrating like my tiller combined with BX tractor short lower lift arms. I suspect the same would go with the blower- the blower blower housing behind a compact tractor can feel like its in the way.

 

[RedDirt]

Thanks to both for your replies.

The U joint tutorial was informative and reinforced the idea that the two shafts should be parallel. I'm fairly sure they will go out of parallel if the top link is adjusted or the blower is raised or lowered but now I have them set to be parallel at what I figure will be my common height and angle.

Also thanks for the heads up on difficulty connection implements with short PTO shafts.

Tonight besides modifying my design drawing to make the shafts parallel I changed the support design that will allow flexibility to couple the blower further aft and gain more pto length.

Big gear arrived yesterday and the small one is due tomorrow. Friday should see the PTO shaft and bearings. Then I'll do a last look at the design with all critical parts in hand. Maybe I can start to work on it this weekend. I'll probably start a separate post for the build