KAMA 554 Front Drive Repair

[tommu56]

Rob
Great thread as usual

Just a thought on the wear.

I bought a 56 jeep years ago and the front end was trashed when I got it.
I called the previous one and he put me on to the 1st oner.
I found that would use the jeep on the farm and only put new tires on rear and summarized that the different tire diameter caused the wear.

check the ratios of tires and rears if possible.
I almost bet that that's what caused wear and then death.

tom

 

[Red55]

Rob You can test very quickly the mesh pattern in the field with persian blue.

I've read in the manuals about doing this with the bevel gears with some kind of paint was wondering how it actually looked in/under field conditions.

Rob thanks for sharing- and I too have also found with the equipment I work on that it's always the same gear or part that fails. I believe that it's designed that way. -Ed

 

[milkman]

Hi Ronald,
I checked for the mesh between gears. You are aware that all the housings and plates are assembled with shims to set the correct running clearance between the gears. This is especially important when using miter or bevel gears since having them sit too close together causes the addendum and dedendum to interfere. From what I could tell, especially in this photo, it looks like the ones that wore were set pretty far apart. You can see the root base of the teeth still exists.



But that does not necessarily mean it was set up incorrectly, but it could be the case. One thing I found interesting was that each casing had exactly the number of shims shown in the parts manual. In real life, the number of shims would vary depending on the tolerances of the gear shape and height of gear hub. What we do is design that theoretical distance but then fill it as needed (via shims) determined by actual fit. Like any machined part, there are tolerances to take into consideration when fitting them together.

With that said, I have no way to determine if the involute arcs actually were set correctly or not, with proper spacing between teeth. Because that is what you want touching when setting up gears like that. That involute arc on each gear tooth is the curved shape that makes contact with it's mating gear tooth. To set that distance, I would need to set it up and bench test the clearance ... to determine where the base hub SHOULD be in relation to the mating gear, in order to determine the number of shims required (if any) to get perfect mesh.

I will most likely do it by "feel" in the field repair. I have lots of experience with gears and I should be able to get it shimmed correctly upon re-assembly. Hahaha...I hope!!

There you go, I knew that when it went back together, it would be exactly right and better than new.

 

[Ronbo]

When I rebuilt my front end (look at John's site) I inquired about the mesh of the gears and the lube. The gears are all straight cut and will be noisy. They all have some play so it will be very hard to shim tighter. I was told to use the recommended oil so that it would lube all parts of the assembly. Thicker oil would not flow as well.

Looking forward to the rebuild.

Ron

 

[3RRL]

When I rebuilt my front end (look at John's site) I inquired about the mesh of the gears and the lube. The gears are all straight cut and will be noisy. They all have some play so it will be very hard to shim tighter. I was told to use the recommended oil so that it would lube all parts of the assembly. Thicker oil would not flow as well.

Looking forward to the rebuild.

Ron

Hi Ron,
I used that 85W/140 gear oil for the front lube. I think the book calls out straight 90W though. I was thinking at the lower viscosity it should be OK? Correct me if I'm wrong though.

You say your bevel gears were straight cut? Like in that there was no involute arc on the tooth shape? I checked mine and could clearly see the tooth shape had curvature to them. If you look at the large ring gear and even the small worn off gear, you can see the curvature to the remaining part of the teeth.



I don't have the replacements in my hands yet, but I will surely look at that.
BTW can you give me a direct link to that post over there?
Thanks,

 

[dfkrug]

I've read in the manuals about doing this with the bevel gears with some kind of paint was wondering how it actually looked in/under field conditions.

Many years ago in metal shop class, we used a steel marking fluid called Dykem Blue, as I recall. In my recent ring/pinion gear replacement on my
Kubota, I just used a black felt marker and adjusted for a contact pattern
in the middle area of the 2 spiral bevel gears. If you look closely, you can
see the black dye, but not the wear pattern. Kubota provided 2 diff shim
thicknesses for ring and pinion.

Rob: I, too, am amazed at the disintegration of your small gears and the
fact that the large ring gears are unscathed. Nice photos!

 

[3RRL]

Dykem is what we use in the trade to layout our steel. Then we would scribe locations using a height gauge on the surface plates. Dykem also makes an impression blue that you smear on for "blueing off" gears or shut-offs. You can get oil base or water soluble and now you can get it in red. You should put it only on the teeth of one gear, set and run it, then look for the marks on the mating gear to see how and where it hits. Then adjust/shim as needed.

The other method is to stack up the gears fully meshed and measure or gage block the distance where the back of the hubs and centerlines of the shafts are in relation to each other. This will be hard for me to do at camp, so I'm going with the "feel" method. One thing I like about the photo Dave shared is the gears and their shafts are in the same housing. On my Kama, the darn things are in separate parts, so it requires assembly to determine proper fits.

As a side note about blueing off, when I was an apprentice back in the 60's, my lead man was an old timer.
He showed me how to "blue off" using black smudge from lighting a wad of cigarette paper sprayed with a little oil. He would hold the lit paper under the steel shut-offs until they were lightly coated with smudge and then "blue it off"... black it off against the other piece of steel. I used that trick a couple times years later to show my apprentices ... they thought I was nuts.

 

[dfkrug]

The other method is to stack up the gears fully meshed and measure or gage block the distance where the back of the hubs and centerlines of the shafts are in relation to each other. This will be hard for me to do at camp, so I'm going with the "feel" method. One thing I like about the photo Dave shared is the gears and their shafts are in the same housing. On my Kama, the darn things are in separate parts, so it requires assembly to determine proper fits.

As a side note about blueing off, when I was an apprentice back in the 60's, my lead man was an old timer.
He showed me how to "blue off" using black smudge from lighting a wad of cigarette paper sprayed with a little oil. He would hold the lit paper under the steel shut-offs until they were lightly coated with smudge and then "blue it off"... black it off against the other piece of steel. I used that trick a couple times years later to show my apprentices ... they thought I was nuts.

For the Kubota, the ring gear shims were not bad to change, but the pinion
required installing the rearend housing onto the main gearbox as its shims
were installed in the latter box.

Nice idea with the carbon black.

 

[dynasim]

When putting gears like that together in the field, can you "feel" the interference when they are to tight by turning the gears? I have not had that sort of issue yet, but am likely to in the future(equipment accumulation =equipment use = equipment repair).

Thanks for documenbting this!

Chris

 

[3RRL]

When putting gears like that together in the field, can you "feel" the interference when they are to tight by turning the gears? I have not had that sort of issue yet, but am likely to in the future(equipment accumulation =equipment use = equipment repair).

Thanks for documenting this!

Chris

Hi Chris and good question.
I am hoping so, since I've not done this before either.

My thoughts are to start assembly using the shims that were in between each part, trying to turn and "feel" the gear engagement. Then remove one or more shim and try to "feel" the difference. If I can tell the difference, I will go with the least amount of shims that doesn't lock up the gears. Otherwise I'll use the same amount as when I took it apart.
I will report if indeed I can tell.