MF35 Front axle beam

[Ulrich]

I am rebuilding a MF35 (3-cyl). The front axle centre bore (where the pivot bushing sits) is damaged as the old busing was well worn through. I have several options and want to explore two:
1) expand the centre bore by ~2mm to get a clean hole and fit a different possibly custom made bushing.
2) welding on addional material to the worn out area and then remachine the bore to suit the standard bushing.

Has anyone done this before and can recommend the best path?

I also have a design question - why is this bushing so short ~20mm and does not make use of the entrie depth of the bore ~50mm? Has anyone used a longer bushing and found it to be problematic?

Thanks for your input.

 

[stevieb49829]

I am rebuilding a MF35 (3-cyl). The front axle centre bore (where the pivot bushing sits) is damaged as the old busing was well worn through. I have several options and want to explore two:
1) expand the centre bore by ~2mm to get a clean hole and fit a different possibly custom made bushing.
2) welding on addional material to the worn out area and then remachine the bore to suit the standard bushing.

Has anyone done this before and can recommend the best path?

I also have a design question - why is this bushing so short ~20mm and does not make use of the entrie depth of the bore ~50mm? Has anyone used a longer bushing and found it to be problematic?

Thanks for your input.

As to your design question, a shorter bushing in the bore makes no sense, except it's what they had. There is the possibility there were 2 short bushings with a grease space between them in the middle. If it were me, and the axle was already out of the tractor, I'd overbore the hole and fabricate a custom bushing or find a standard size bushing that will do the job and overbore to fit your new bushing press fit. Then ream it to fit your pivot pin. Just don't forget the grease passages. I'm not familiar with the MF35, but are you sure your pin pivots in the axle, and not in the bolster? steve

 

[Jim.ME]

As to your design question, a shorter bushing in the bore makes no sense, except it's what they had. There is the possibility there were 2 short bushings with a grease space between them in the middle. If it were me, and the axle was already out of the tractor, I'd overbore the hole and fabricate a custom bushing or find a standard size bushing that will do the job and overbore to fit your new bushing press fit. Then ream it to fit your pivot pin. Just don't forget the grease passages. I'm not familiar with the MF35, but are you sure your pin pivots in the axle, and not in the bolster? steve

Bushing in the axle tells you that it is most likely the pivot point. A look at the parts book confirms that, as the pin is locked to the support with a bolt.

They only show one bushing, which is short for the space. I think I was able to put 2 into a 135 axle last time I had one apart, but I'm not sure on that.

If you are going to bore the axle, have it welded up, or bored and install a press fit sleeve, then bore it to take the standard bushing. The sleeve could be a bit longer than the axle is thick (if there is room in the support for that) to allow two standard bushings to be used. A grease hole with fitting could be added top between the two bushings. The risk is a hole will slightly weaken the axle at that point.

 

[Ulrich]

Thank you Steve and Jim.
I will check with a mechanic / engineer and see if he can weld it but it is my preferred option. I am a bit worried that by boring it out I will weaken one side of the beam as the bore is off the centreline of the beam. I will then machine it to fit two of the standard bushings. I looked further at the design and concluded that the busing only needs to support the pitch moment on the axle generated by the tyres, the yaw axis is supported by the radius rods, roll axis is free and motion allowed for via the bushing.

For future readers of this tread, the IT shop manual states to NOT use grease, but graphite. I assume this is as grease will bind dust and dirt and likely lead to more wear.