KAT excavator - upgrade

[Rimrock]

Hi all,

As I did notice the threads about the relative new excavator on the market, the KAT out of China, I got curious about the thing and order one myself. Well, it just dropped down on my bench this weekend I did pick the basic version without any hydraulics, but it was delivered with the track and swivel motors.

Scale;
I like numbers, so I had to check out what kind of scale this machine would fit. The fabricator states 1:12...nooo, can't agree on that one..The inspiration for the KAT is quite likely the CAT 365, 65-70 tons, and it seems to turn out at a scale of 1:15.5 . In the Tamiya scale, 1:13.5, it will have the size as a 25-30 ton machine, though with a bit narrow cabin version.. The width of the undercarriage is 225 mm, on the tracks, that makes it fit fine on a 1:Tamiya trailer. Generally it's a neat sized machine, fits fine operating with the Tamiya trucks (and Wedico naturally)

Compared to the 4200xl, the KAT is a bit smaller machine. Construction vise the 4200xl is a more robust, and heavier piece of equipment, as it is fabricated mainly out of 6 mm alu.plates. The KAT is mainly of 2-3 mm alu. That works out quite fine in many locations, but I see that the plate thickness should be larger on some critical points. I guess it is a combination of lack of knowledge, and an urge to make a low cost product, that is behind. The fabricator could 'easily' with some minor, and relatively cheap, adjustments risen the quality some steps. I might send him some epictures and ideas after I've completed my modifications..

Alright, my idea is to equip the machine with a Premacon pump, Magom cylinders, and not decided what valves, Premacon or the cheaper option Magom. I will just keep the cost a bit down, may sell it later on, but want a good performance. (I also am scratch building a excavator, that will be my 'number 1 operator' will post a seperate thread later on)

Initially I did not plan to modify 'the shell' of the machine, except tighten up joints and swivel, but it seems that some more work have to be done...

* Boom and dipper arm
I like the way the boom and dipper have been put together; the side plates attahed to each other in 4-6 point with countersunk screws, added threadlock, good. It seems surprisingly stiff.

- Counter sunk screws. I have made the counter sunk deeper, to be able to hide the bolt heads and make the surface flush.

- I've added a piece of 2 mm alu on each side of the boom/upper structure interface, to make it a bit more stiff.

- The original cylinders are of equal length (?) I don't have them myself. It seams that the stroke of the cylinders are adapted to the movement of the 2 boom cylinders. On the dipper and bucket these cylinders seems to have an too long stroke. Anyway, I could not get the Magom cylinders to match the max lenght needed on dipper and bucket, so I will put new cylinder brackets here, to be able to use shorte cylinders (movement will still be the same)

- Stick. As I am going to fabricate a new bracket for cylinder anyway, I just as well removed the existing one and did some other modification too. See picture. I did mot like the original open space on in each end of stick. so i made a new 'banding' plate to make the stick look a bit more real.

- I too place bushings of brass in all joints, and get rid of the 5 mm bolts, whose threads soon would had eaten up the alu.material in the holes...I will use 6 mm bolts, 'smooth surface', in the main joints.

* Engine house

-The bottom plate of the engine house is too thin, 2.7 mm. Was a bit dented and bent when delivered. Will try to 'make it flat', and possible add a flat bar running in the centre of the bottom plate, for stiffening.

- May will ad a counter weight, steel plate, in the rear end of the house, if needed.

* Undercarriage

- Plates on which track gear motors are attached, are of too thin material, 2-3 mm alu. Not stiff enough to keep the idler wheel lined up straight. I've added a bracket at the rear end of the motor, that helps things straighten up, and gives the setup much more stiffness.

- Track rollers...mmmm..come ooooon..) alright, they may work for a while. Maybe to fabricate some 'real' rollers, and get rid of the thread bolt shafts..

Puuuh, it's getting late...can we do one more....?

- The idler wheels are not attached 'straight' on gearbox shaft. Shaft diameter is 7.95 mm, and the centre hole drilled in the idler wheel is 8.3..Need make that fitting tighter

best regards
Oyvind