Bachmann Geared Steam Climax

[Schraddel]

Hello,

these fine locos are plagued with cracked gears. But not only the bevel pinions in the trucks are prone for cracking. There is a tiny spur gear deep hidden in the center gearbox. Here i post several photos to show in a step by step manner how to get there:


It's 3-Truck Climax with Walschaerts valve gear. The trucks are simply fixed by snap fasteners like in textiles. They can be easily clipped off.


Remove the 2 screws on the bottom plate of the center gearbox. And lift off the cover.


Remove output shaft.


Unscrew and remove valve gear on both sides.


Lift out jackshaft.


The boilershell is fixed with 4 screws:
2 unter the cab sides.
2 under the boiler.


Unscrew the small PCB and pry off gear cover.


Remove motor screws and motor.


Then you get acess to this screw hidden under the motor. Remove it.


Then you are able to lift out the center gear box.


Beware of the strutted frames. They are partly mounted on the gear box and have to be removed there.


Remove the screws on the side of the gear box.


Lift out this gear shaft.


Look an that! This is the faulty piece, a cracked spur gear (10 teeth, Module 0,5, shaft diameter 1.5mm)
Only the first releases are concerned. Later Bachmann made the little spur gear out of brass.
Remounting is in reversed order.
Hope this is helping somebody.

Lutz

[Schraddel]

Hello, 

now the more easy to handle bevel pinions in the trucks.


A 3 Truck Climax. This was another loco with no cracked spur gear in the center gear box. But all bevel pinions were cracked.


Easy clip the trucks off.


To get acess.
- remove brake beam. They are simply clipped, bend brake shoes to the side. They are very elastic, so no danger of breaking them.
- unscrew the 3 oder 4 tiny crossheads screws
- lift the bottom frame
- lift out the gear shafts


This is the middle truck. The bottom frame is mounted with 4 screws.


Remove the cracked pinions. They came easy right off. When off the shaft, the gaps close and are only visible by the means of a magnifier.
Throw them immediately into the dust bin. So they can't fool you anymore.


Before you mount the new pinions.
The bore in the pinions are too small in diameter. If you press fit them with force right onto the shafts, then there huge internal tensions will be raised. Too much and unnecessary for this little gears. Probably they will crack again in near future.
You see the shaft were the pinions will sit is knurled. Taking a measure with a caliper; it says 1.2mm. Enlarge the too small bore in the pinions with a 1.2mm drill bit. Don't worry, plastic is also elastic. The bore will be 1.2mm when the drill bit is inside. But when you pull it out, the bore is smaller as 1.2mm. The plastic material has relaxed.
But this bore is absolutely adequate for a press fit. And adequate for the forces to transfer. And the mounting is much easier.
And at least it is the trick to give the new pinions a long life.

From time to time Bachmann has this bevel pinions available individual. But no more than 10 pieces per order  
Sometimes you have to buy complete shafts with mounted gears. Depending what is just available.


Lutz

[Charlie B]

Hello, 

Lutz, 

     Thanks for this tutorial. The mention of drilling the hole in the gears will be very useful in other applications. I had never though about the plastic hole shrinking when the bit was removed. 
Charlie

[LiveSteamer]

Lutz,

That is a great tutorial for anyone that has a problem with a Bachmann Shay. Thanks for sharing.