How True for a Driveshaft?

[Greg Riutzel]

This is for a 1975 1650.
In looking things over for the season, and an effort for less vibrations, I see a slight wobble in the driveshaft from the engine to hydro pump.
Having 2 flex discs, 1 one each end, I wonder how much eccentricity is allowed?

As it is I can measure a runout of maybe 1/16" to about 3/32" or 1/8".

I recall some years ago when checking the shaft, it was straight rolling on a flat surface and I can check it again.

Maybe some new flex discs or coupler bushings are in order?

Asking for field guidance before the shopping begins.

 

[dschwandt]

3 flex joints, w/2 in the rear.
Check the coupling arms and their pins, front and rear, for wear.
Check the ball bushings, front and rear for wear.
Check both ends of the driveshaft and the spirol pins for wear.
Good luck!

 

[Greg Riutzel]

3 flex joints? This tractor only came with 2. I only see 1 at the rear in the Service Manual pictures. The Parts Manual lists 3 however though the line drawing depicts 2 recognizable ones.

Ball bushings don't have slop I can see but I'll take the bolts out of the flex discs to be sure.

 

[dschwandt]

Put a 2nd one in the rear.
Bolts will perhaps need to be a pit longer is all.
The aged ones become distorted & petrified over time.

 

[danderson]

At serial number 622952 they changed to 2 discs on the rear. They also changed the shaft and removed the large ball from inside the rear coupler.

 

[Greg Riutzel]

The S/N on mine is 540720. So I unbolted the flex discs. They seem okay, resilient, tight bolt holes, and the ball centers are say in the neighborhood of .010-.015" movement which is just enough to move the shaft for disassembly/assembly. The spirol pins are tight enough that I used a jack underneath to support the shaft when removing them. Perhaps what I'm seeing is the slight engine movement when running, especially at idle.

I've never had a machine with this large a single cylinder engine and I understand at 16 Hp it's quite a thumper, but I'd like to mow an acre without my ass getting gelled. Last year's overhaul included all new factory engine mounts, removal of the balance gears, and installation of Kirk's balance plate.

 

[dschwandt]

Check for on the spot timing using the static method.
My 1650 w/Dave's balance plate after the major and static timing is the smoothest running Cub in my stable next to the diesel 882.

 

[mgonitzke]

As it is I can measure a runout of maybe 1/16" to about 3/32" or 1/8".

All of my tractors that I have measured are less than 0.010" runout. What you have sounds quite excessive.

 

[Greg Riutzel]

Okay, here's what I've done: Mounted the mag base/dial indicator and checked the shaft R.O. It's out there in the breeze at .030-.035"; close to the 1/16" I thought I saw.

The timing was a tad off. I widened the gap a skosh so now the points open right on the "S" on the flywheel.

Looks like I'm off to the store for a new shaft and I'll order some coupler balls for good measure.

 

[Greg Riutzel]

New parts installed and little change with the results. The new shaft is turning with slightly less run out and pretty much the same vibes when full throttle as before. I am supposing at this point it's the nature of the beast. I've done a year or so of researching this behavior and it seems to be a common complaint of owners of working machines with this large a horsepower. With balance gears or without, new iso mounts or solid mounts, cradle mods or not they all have similar stories. In the mean time a 4" thick foam pad is helping the posterior. Perhaps if I keep this for the long term maybe going V twin is something to look into.

 

[eweiss]

Okay, here's what I've done: Mounted the mag base/dial indicator and checked the shaft R.O. It's out there in the breeze at .030-.035"; close to the 1/16" I thought I saw.

The timing was a tad off. I widened the gap a skosh so now the points open right on the "S" on the flywheel.

Looks like I'm off to the store for a new shaft and I'll order some coupler balls for good measure.

Check the engine and trans couplers for run out

 

[mfrade]

At the trans end, remove the coupler and check the shaft runout itself first. The coupler will need to be verified on the ID, not the OD. The same thing will need to be done at the motor itself. You'll first need to verify runout of the engine coupler /adapter ID for runout. Once those are verified to be at least the numbers posted above ( .010) then install the driveshaft and remeasure at each end on the shaft. If you have access to a lathe or can devise a set of centers, set up the shaft to verify straightness before installing.. HTH

 

[bwstevens]

The kitchen table will tell you how straight the driveshaft is .

 

[Greg Riutzel]

The coupler will need to be verified on the ID, not the OD. The same thing will need to be done at the motor itself. You'll first need to verify runout of the engine coupler /adapter ID for runout.

Not gonna happen on these couplers for run out. This chassis is a pre 622 serial number. Both have self aligning semi-circular ball inserts and 2 flex discs are used in the drive line with 1 on each end.

The engine side adapter is new. The shaft is also new and the ball insert was replaced on the pump end coupler. I have to give a positive YEA! to CCSpecialties for sending the drive shaft well packed in a box; unlike some others and competitors who have taken to shipping even machined parts in bubble bags, UGH!

I did the flat surface check for both shafts and the new one is slightly better. The holes for the spirol pins are tighter in the new one so it's good I got it anyway.

The dial indicator readings after all the new parts are in are about 1/2 of what I had but no way am I gonna get .010" or less. A spinning shaft held by 2 rubber bands with standard bolt holes; no grid, no pins or pin and bush those flex discs are working pretty good especially at absorbing torsional peaks from the engine and probably why the pump end at this age is still in good shape.