YM276D Brakes

[CoyPatton]

Thank you. The tractor stays in a barn or garage when not being used. That corrosion had to occur or begin prior to me purchasing the tractor a couple of years ago.....

The big lesson here for all of us is to learn all we can about our tractors and to check out all of the maintenance items as soon as possible once the tractor becomes ours.
Was that corrosion there 2 years ago when you bought it. Probably! Was it that bad? We will never know, but best guess is no—even humidity in the air can cause things to continue to rust.

How does your drum look? I expected much worse pitting on your cover than I saw in your pictures of it cleaned up. I also expected more rust in your drum than appeared in your pictures from the looks of your shoes and cover.

 

[richriddle]

As suggested, the drum goes to the local mechanic to get machined tomorrow. Here is the rusty drum cleaned up a bit from when it was on the tractor.



Versus this on the YM276D.

 

[richriddle]

The mechanic didn't have a tool small enough to machine the drum. Hopefully a machine shop can surface the drum. The original YM276D Manual seems much more detailed with diagrams and information.

 

[CoyPatton]

Have you measured your drum’s inner diameter? 2 thoughts here.
1) Is the drum out of round—constant pressure from the locked up breaks equals heat build up. Then with the one liner loose inside the drum, it could have had pressure to force it out of round.
2) 2mm of wear allowance with continual pressure for ??? how long.....longer than you have owned it! Along with the depth of your pitting, you may just need to be looking for a replacement drum. Hoye shows it as a used part only so call them and any others you know of that might have used parts. Aaron at Hoye may be able to let you know of other tractors that may use the same brake drum.

 

[rScotty]

The mechanic didn't have a tool small enough to machine the drum. Hopefully a machine shop can surface the drum. The original YM276D Manual seems much more detailed with diagrams and information.

View attachment 660975 View attachment 660976 View attachment 660977

Yes, I agree that a machine shop is the way to go for this. It sure would be easier on the machinist if he had a splined shaft to mount the drum on to maintain concentricity. Hoye may have a stub shaft that he uses as a tool for this. Probably worth a call.
I don't believe these are lined drums. it's been a lot of years, but I recall them as being one piece.

 

[CoyPatton]

I don't believe these are lined drums. it's been a lot of years, but I recall them as being one piece.

I totally agree the drums are not lined but are as you say one piece. My reference to the lining was that one of his rusted up brake shoes appeared that the bonded brake lining had detached from on of the shoes. It was then possibly free to jam against the drum and other parts to constantly create heat and then when allowed to cool cause distortion in the drum.
Also that 1.9-2.0mm is very tight tolerance on being turned on a lathe. An inexpensive 6” slide caliber could have him using the time to find a machine shop to handle splined center looking fir a drum if it is beyond 142mm or out of round.

 

[richriddle]

Coy, the machinist checked for out of round prior to working on the drum and stated it fell within tolerance. He also read the specifications from the manual provided above and said after machining the drum falls within specifications. The machinist finished the drum today and said he removed about 17/1000". Almost all of the pitting is gone, but some minor pitting exists. Running a finger across the area doesn't allow one to "feel" the pitting at all though. There is a slight discoloration in the area where the "pitting" still exists.



The operating arm/cam pin pressed out of the cover with no problems for cleaning. Whoever said the operating arm/cam pin had only one o-ring was spot on the money. And a very deformed and old o-ring it was. The operating arm/cam pin would barely move prior to removing it and cleaning, but it now easily moves when dry fitted. Of course, the o-ring needs to be replaced, but that should not offer a huge amount of resistance.



The stationary one is certainly holding tight when put on the press. I am not sure it's worth risking cracking the cover to remove and reinstall that anchor pin since the exploded view shows no o-ring inside it. It seems appropriate to simply replace the washers and reinstall the nut.

 

[rScotty]

Coy, the machinist checked for out of round prior to working on the drum and stated it fell within tolerance. He also read the specifications from the manual provided above and said after machining the drum falls within specifications. The machinist finished the drum today and said he removed about 17/1000". Almost all of the pitting is gone, but some minor pitting exists. Running a finger across the area doesn't allow one to "feel" the pitting at all though. There is a slight discoloration in the area where the "pitting" still exists.

The operating arm/cam pin pressed out of the cover with no problems for cleaning. Whoever said the operating arm/cam pin had only one o-ring was spot on the money. And a very deformed and old o-ring it was. The operating arm/cam pin would barely move prior to removing it and cleaning, but it now easily moves when dry fitted. Of course, the o-ring needs to be replaced, but that should not offer a huge amount of resistance.

The stationary one is certainly holding tight when put on the press. I am not sure it's worth risking cracking the cover to remove and reinstall that anchor pin since the exploded view shows no o-ring inside it. It seems appropriate to simply replace the washers and reinstall the nut.

I think that it was the brake operating arms on the earlier and smaller tractorsthat had two O rings mounted in grooves cut in the actuating arm. They sealed by being inside the bore of the mounting "barrel" on the cover. For some reason the YM276/336 went to a single O ring .... and I believe that O ring sealed differently. I think it was held pressed against the cover by the face of the actuating arm rather than being inside the cylindrical bore... but I'm not sure of that.... & also not sure just how your actuating arm is held into the case cover. It doesn't appear to have the shim & circlip setup of the smaller tractors, and from your picture it doesn't have the crazy threaded-into-the-cover mounting system that some did.

I would NOT try to remove the stationary shoe pivot. There isn't any advantage to doing so. It may be a shrink fit.

Nice brake job you are doing there.
rScotty

 

[CoyPatton]

I agree with rScotty on not messing with the stationary pin at least not as long as it is the correct orientation for your shoes. Considering the condition that the cover appeared to be in when you got it off, you could create more problems.
It has been many many years since I have done any brake machining work, but I still have concerns about the drum. Back in the day, a standard pass on a lathe was 0.010”. Perhaps this has changed over those years I do not know!
The concerns that I have still have are
1) he did not take out all of the pitting
2) 0.017” converts to 0.4318mm
3) you did not mention measurements merely that you were told it was within specs

As you are talking about braking from high speeds as in an automobile, it will probably be fine. In truth if the drum was not out of round, it would have likely been fine without being dressed.
I do not know about your usage of brakes, but I do do that from your description, you have not had a brake on that side since prior to your ownership of the tractor.
I would tend to estimate my brake usage to be 95%+ as either while parked or while holding the tractor on a incline. The less than 5% remaining would including the stopping and starting on an incline and other slowing/ stopping and hard turning using one brake for steering.
Best of luck in getting those brakes all back together.

 

[richriddle]

I agree with rScotty on not messing with the stationary pin at least not as long as it is the correct orientation for your shoes. Considering the condition that the cover appeared to be in when you got it off, you could create more problems.
It has been many many years since I have done any brake machining work, but I still have concerns about the drum. Back in the day, a standard pass on a lathe was 0.010? The machinest completed two passes because the first pass didn't remove the pitting to the touch. Apparently he wasn't quite cutting .10" each pass (or at least on average) Perhaps this has changed over those years I do not know!
The concerns that I have still have are
1) he did not take out all of the pitting
He said he removed it to the touch but not discoloration. Technically the pitting is gone.
2) 0.017 converts to 0.4318mm
The machinst measured the drum after turning at 140.5mm, the range is between 140 and 142mm for the drum.
3) you did not mention measurements merely that you were told it was within specs. The second photograph in post 53 in this thread shows the specs between 140 and 142mm (and a few other specs) according to the Yanmar manual

As you are talking about braking from high speeds as in an automobile, it will probably be fine. In truth if the drum was not out of round, it would have likely been fine without being dressed (several people suggested it was fine with a sanding, but I wanted it to be smoother).

I do not know about your usage of brakes, but I do know that from your description, you have not had a brake on that side since prior to your ownership of the tractor.
I would tend to estimate my brake usage to be 95%+ as either while parked or while holding the tractor on a incline. The less than 5% remaining would including the stopping and starting on an incline and other slowing/ stopping and hard turning using one brake for steering.
Best of luck in getting those brakes all back together.

Thanks for your help with the brakes.