OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers SB 45 - Rear Roller issue

Hi there, thanks for your help on my previous post re the 33.
I did upgrade to a 45 in the end (anyone want to buy a good 33 ;)), but I had an issue with the 45 where it wouldn't drive and also I couldn't pull it backward as the roller would jam (rear one)

I had a bit of a hunt around and I think that the non-drive side little key thingys may have dropped out and only allowed rolling in one direction (forwards).

I took the roller off and had a look, but so far I am at the stage where I have the roller in half, but am unsure how to remove the non-drive side bearing..

So following that what is the best way to reinstall the key thingys (sorry for my ignorance on the name there) ie with roller horizontal or vertical.

Also how would this happen, would the mower need a serious tilt?

Thanks for your help...

Andrew

Diff lock pins is I think what I was looking for

That mower does not have a differential. I think they are ratchet pawls, but I'll leave this to one of the SB45 people.

Ratchet pawls!?
You would know more than I Grumpy that is for sure!!! :), I just copied that from another post

Hi Waikphys,

As Grumpy has already eluded to it will be a Pawl issue within the drive roller.
For that the roller will be required to be removed and stripped down, completely cleaned and relubed. It's not a huge job but one that must be tackled carefully.

Cheers,
BB

Did you put it in backwards?

I only uninstalled it, was working fine and then stopped!!!

Do I need a puller for the non drive side bearing?

Yes I would use a puller if it doesn't slide off easily by hand

Ok so fully apart now...
So the ratchet pawls should engage the roller when it is driven and allow it to freely rotate backwards?
Or does the roller and shaft rotate backwards as one unit and its only when the drum clutch engages that the pawls lock up the drum.

I am confused now as to why mine wouldn't roll backwards, or is this normal for a 45?

Hello waikphys and ODK members and guests,

I'm sorry we did not initially address your question- how to remove the non-drive
side bearing. In any case, it is now fully apart.

Personally, I would have done a couple of checks to see whether the land-roll was the problem,
before it was dis-assembled.

You said,
"I had an issue with the 45 where it wouldn't drive and also I couldn't pull it backward as the roller would jam (rear one)"

That could have clearly been a secondary / landroll clutch issue.
In any case, let's proceed - Here is a diagram of the assembly:
[ignore the centre, small drum - this diagram covers the 20" machine as well]



To answer your question:
"So the ratchet pawls should engage the roller when it is driven and allow it to freely rotate backwards?
Or does the roller and shaft rotate backwards as one unit and its only when the drum clutch engages that the pawls lock up the drum."

The first question is the right one.
When turning the lawnmower, the outside roller can turn at a faster speed than the roller shaft.
Neither roller can turn more slowly (or in reverse) to the speed of the roller shaft.

The pawl and ratchet system is an excellent and reliable means of gaining
differential action on lawnmowers, and it has been used right from the earliest days.
It is still used today.

It's a simple test to see if it's working.
The 6 pawls will all face forward [left] from the drive side on re-assembly.
Lubricate them with oil, but not a heavy grease.
Lubricate the roller shaft and drum bushings with grease.

On assembly, rotate the drive-side sprocket anti-clockwise:
the pawls will engage in the rollers, and the shaft will lock.
Turn the drive-side sprocket clockwise and there will be free travel of the shaft.
You will hear the pawls 'ticking' on their respective ratchets as they rotate in the drums.

[Do this test before putting the assembly back in the frame.]

NOTE that the R.H. side bearing housing (opposite drive side) is slotted.
This is to re-align the rollers with the bottom block so they are parallel.

I hope this answers your questions about the pawl/ratchet system on the 45.

-----------------------------
JACK.

Thanks awfully Jack, I will try this asap. Fingers crossed or I will be hitting you up to see what could be causing the issue in respect to the secondary clutch

With the pawls do they sit flat side up or down in their holder? as they do have that concavity on one side

Hi waikphys,

Mate, I'm just filling in for the experts.
I haven't split a 45 land-roll in decades.
From memory, the flat side will face its pawl carrier.

---------------------------------------
JACK.

As I recall, there is only one way it can work. When the drum axle rotates forward, the pawls that are below the axle drop downward, and engage the ratchet wheel in the drum, so the drum can be driven forward. If you put the pawls in upside down they will have difficulty dropping down fully.

When the pawls engage, they drive the drum forward if the landroll clutch is engaged - but the mower can be pushed forward freely whether or not the landroll clutch is engaged, since the pawls will disengage if you push it when it is not being driven. This implies that the drum can only be pulled backward when the landroll clutch is disengaged, because the driven plate of that clutch will have to spin backwards for the mower to move backwards. If the mower could not be pulled backwards, might that mean that the landroll clutch was not freeing properly, or you weren't pulling hard enough? It will obviously be quite a bit harder to pull it backwards than to push it forwards, because you have to turn the drive mechanism and half of the clutch - which you don't have to do to push it forwards.

No Worries Jack, I very much appreciate the help on this one!!!

Ok, thanks very much Jack and Grumpy all is well and things are purring like a kitten.
I had a great time pulling the drum apart and removing all of the ancient, rock hard grease, before cleaning and re-lubing as you recommended.

As a tip for other younger players I honestly do think that it was the lower part of the drum clutch adjuster fouling the drum sprocket that prevented the unit from driving and jammed it from being able to be pulled backwards...so worth a look if anyone has the same symptoms.

Still like I said it was good fun, and really medically necessary to give the drum a birthday. I really enjoy working on these, always something new to discover, and such a well designed and produced machine!

It is certainly a lot more pleasant to work on a well-engineered, well-made machine than on a tin-pot short-life one. It is also a great deal nicer not to have to contend with major tenant's improvements.

Now that you've been through that process, you are familiar with your mower and will not be afraid to attend to future faults in relatively obscure places.