- Joined
- Jan 25, 2021
- Messages
- 50
Big 8 wheeled Valmet double bunk forwarder 840.3 can haul 12 full cords of wood to the landing....2 axles in the front.....2 axles on the rear......articulated in the middle 8 big logger special tires....but if the transfercase for the drives is Slopping around like a Northern Pike out of water your in big trouble!!! First thing that happens is the mounting brackets that hold it gets the bolt holes egg shaped,which allows the case to move even more,the second thing that happens is the rocking motion busts the casting where the bolts thread in,the third thing is you **** your pants when told you cant just buy the broken casting and a new one will be 30 grand...the whole transfercase!!!...that's where I save your day....grind the casting with carbide burr and degrease well....I build up the big missing chunks with the tig welder making sure to butter up the casting well after preheating to 250 degrees...you are on high frequency AC. Like welding aluminum...keep stacking beads.. be extra cautious where you will be going in with a tap drill and tap... you dont want to melt the cast iron and mix it with the aluminum bronze filler rod as the carbon in the cast iron will turn into CARBIDE and then your in trouble!!! With a good eye and steady hand feather the foot pedal to just below puddling the cast iron...lay down a bead around the hole and move away for a while..then head back and stack your beads around the bolt hole....overbuilding the damaged area so you can machine it back to OEM. Spec's....I went in with an 11/16 carbide endmill to cut the egg shaped bores true... then tapped out to 3/4 X 16 tpi. On the boring mill....the owner came up with a novel idea!! We made a cardboard template by laying it over the mounting bosses cutting all around it with a ball pein hammer like your cutting out a gasket...you then transfer that to a 5/16 plate cut out tightly then slid over the bosses....you bolt up the mounts then slide your plate back against the mounting brackett and clamping it in position...remove the whole affair and edge weld the sides and bottom only!!! The bracket is a fancy alloy and welding across the top could cause a shear point or Stress Riser...be sure to preheat to 275 degrees before welding....now if the bolts loosen up the bosses are locked in like a socket over a nut...it cant move....this is an inherent problem for this machine...but no longer for this one....as of this writing they have moved over a thousand cords of wood with this machine with no problems!!
