Tongde M113A1 Bearing problem

[tdriver113]

While disassembling my ACAV model for additional painting I noticed I have a new problem. Looks like excessive grease migration through the open bearings in the hull. Previous to this I had not seen any excess grease anywhere around the motors or drive sprockets, so it's a complete tear down for more investigating. It has spread to the first 3 suspension arms on both sides and at the corner and top on the front hull.

[tdriver113]

So after taking everything apart the news is disappointing. All the hull bearings are open style inside and out. The size is 7x11x2.5 MM. A quick look around the net did not turn up any sealed bearing options. Closest are the size used on the Tongde M-60 7x11x3 MM that would stick out of the hull slightly and would need to have the inner bearing notch widened.

Not the best looking bunch.



Drive sprocket gears are held in with a c clip.

[tdriver113]

I finished taking out the front shafts, gears, and bearings. I am going to de grease everything and replace the outer hull bearings with sealed ones. I have the leftover M 60 bearings and I ordered a set of flanged bearings to see which works best. I also plan on sealing around the firewall to stop any further problems so I don't get any future grease staining on the finished crew compartment.


Drive shaft parts.




Firewall area to be sealed.




Front drive bearing.

[RichJohnson]

I looked on eBay and found shielded ones but they are $8 each. That was it all others were open

[tdriver113]

I looked on eBay and found shielded ones but they are $8 each. That was it all others were open

I saw that one. Seems to be a popular size for fishing reels.

[tdriver113]

Here is the test fit of the new bearings.

Flanged.


Rubber sealed.


Side view.



I'm going with the flanged bearings and removal and replacement of the factory grease that likes to spread around. I do loose a little contact area with the torsion bars but I don't think that will be a problem. My plans for the detailed crew compartment have changed so I'm back on track.

[RichJohnson]

The flanged bearings will add width to the hull thickness at the hub for thr tortion bar. You need to now verify if the tortion bar will correctly install and its wheel will still line up with thr idler and drive sprocket.
I suspect it will be out board set by the thickness of the bearing flange.

[tdriver113]

The flanged bearings will add width to the hull thickness at the hub for thr tortion bar. You need to now verify if the tortion bar will correctly install and its wheel will still line up with thr idler and drive sprocket.
I suspect it will be out board set by the thickness of the bearing flange.

Thanks RichJohnson for the tip about lining things up. I figured something would be out of alignment and I was not disappointed. The idler wheel is the problem child, about 2mm out of alignment. The front sprocket and road wheels all line up pretty good. Same with the torsion bars. I spun them with a track on and everything seemed OK. The shoulder screw for the idler needs to have a longer length to line everything up. When I was working on my M60 I had a problem with one of the shoulder screws and found a replacement at McMaster Carr. I'll see what I can find.

Idler.



Drive sprocket.


Internal drive shaft and torsion bar.