Replacing Gears Weaver RS-3 Chain Drive

This is all fiddly work.   It is hard to break the parts, but not impossible, and it gets easier the more  you do.   The first time it is confusing and a learning experience.

To start  you have to disconnect the universal from the spider on one or other.   I suggest disconnect the one on the shaft you just took the clip off.    To do this slip a small screw driver blade under one leg of the universal and twist it gently to pop it off the spider.  

Then you need to remove the chain.   To do this slip a very fine screw driver in between the outside leg and inside pin on one of the links.   Again a little twist and it pops loose.    Putting it back is hard.

Once you do that you can move the shaft from the motor to the side and slide the shaft from the gear tower out.

I would not replace the tower unless you have run this a lot and it very sloppy.    If the top gear is the split one,  you need to pull the  universal half off the shaft, and then pull the gear off.    The split gear will come off fairly easily.   these are all tight fits, so putting them back on takes some patience.    I have a small vise with grooves in the jaws.    I open it so the end of the shaft will fit into the grooves and the jaws will support the gear.   Then I gently tap the shaft down into the gear.

Putting the chain back is a real chore.    I find I can do it by wrapping it around both sprockets so the loose ends are next to each other on teeth on the sprocket, then using a small screw driver to pry the outer link of the one over the inner link on one side.   ONce one side is on, the other goes on easy.

Putting the universal together is usually easy.   I use a screwdriver with a blade a bit smaller than the opening between the jaws on the universal.    I slip this behind the spider on the universal that is still attached, and that holds the spider in place while I snap the other universal half over the pins.

Now if  you need to replace the lower sprocket, you to take the truck apart.    First you do the above process to the the tower disconnected and to get access to the screw holding the truck to frame.   Unscrew this screw and you can take the truck off the frame.    When remounting the truck, do not use a power driver.    Carefully turn the screw in the reverse direction  until  you hear and feel a slight click to find the existing threads, then screw the screw in the right way.   I use hand tools and this method for all screw in plastic so as not strip out the plastic.  

To take the side frame off one side - you only need to do one, turn the truck over look at the pins in the bolster.   The pins have a groover that is slid over a notch on the bolster.     DO NOT PULL on the sideframes - if  you do  you will break the pin off and make them  useless.     Again use a screw driver with a blade about the width of the pin.    Slip into the space under the end of the pin from the middle of the truck and pry/twist slightly to pop the pin loose the side will come off.    To put it back on, allign the wheels in the one still attached and then the one loose and push them together IN THE MIDDLE OF THE SIDEFRAME behind the pin.

to the bottom sprocket off, you probably have to take the gear box apart.    It is screwed together.   When weaver built these, they put some sort of locktight on the nuts.    It is very hard to get them apart the first time.    Use a needle nose plier to hold the nut and a decent screw driver to turn the screw.    You need a blade that will fit the 2-56 screw, but the bigger the handle the more leverage you get.    The sprocket tower is put on with same screws  and will also be loose.   If you get this far, you might as well use the adjustable new one.

The method to change the sprocket as described above applies to the lower one once you have the worm shaft out of the gear box.   

I hope this helps you.   It is harder to explain in writing than it is to do.    I have done dozens, and it all makes sense once you see how it works.    I think these are great drives and very easy to maintain.

My exploded parts diagrams offer no guidance. That said, the center hole of the 3 to the right of the chain drive should have a screw in it,  as that is where the truck frame pivots. Remove that, and the truck should drop down. Watch out for a possible nut at the other end of the screw. The drive line just pops off the universal's pins. You may need a screw drive to carefully open one yoke up. It's a snap fit. Check all the plastic components of the universal joint for cracks. They happen! Your pictures don't show it, but there should be a secondary drive line that connects the 2 trucks and goes through the fuel tank. It is usually joined by universals and a sliding joint. It comes apart the same way as the top drive line.

The attached diagrams may help...

Chris

LVHR