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Installing the Aster Mikado Axle Pump


by Joe Betsko




If you have bought the Aster USRA (Black) Mikado kit and intend to install the axle pump, then do not proceed past Section 6 until you have the axle pump kit in possession and ready to install.  


For purposes of these notes: a Kitbuilder is one who is assembling the pump in sequence with the overall kit; a Retrofitter is one who has already completed the Mikado kit and is subsequently installing the pump. 


The notes below are intended to be used in conjunction with the original Aster assembly instructions;




1. Retrofitters: remove the 14-2 cab and 14-3 end plate. Don't put both SB4 balls into the 6B-10 pump body; otherwise, the other ball will fall out. For now, place one SB4 ball into the top half of the 6B-10 pump body. The top half is the only half with a seat for the SB4 ball. Make sure that SB4 ball seats correctly. The 6B-12 banjo bolt is identified as having a notched out slot.


2. Straightforward per Aster assembly instructions.


3. Perform this after step 5. 


4. The remaining banjo bolt, 6B-8, is identified as having a seat for the remaining SB4 ball which can be added at this time. Do not fit the 6B-9 pipe to the 6B-16 end beam yet. 



Kitbuilders: hold off on installing the back three 6-5 break beams,6-4 break shoes and 6-6 break beam rods until the axle pump is assembled.  


Retrofitters: remove the back three 6-5 break beams,6-4 break shoes and 6-6 break beam rods which can be refitted after the axle pump is assembled. 


5. Loosely fasten the 6B-7 lock nut over the 6B-10 pump body.  



Retrofitter: remove the E2 clip from section 13 and remove trailer truck frame assembly from the center pin of the frame.  


Retrofitters and Kitbuilders: you should notice a notch on either side of the center pin. Position the 6B-10 pump body over the second cross-tie from the back and temporarily tighten the 6B-7 lock nut over the 6B-10 pump body. Both pipes should be routed through these notches as close to the frame as possible. Please note that shaping the pipes involve some trial and error. These pipes should be routed as close as possible to the top and side of the frame to avoid fouling the trailer truck frame. 


Once satisfied with the pipe routing, it is time to fit the 6B-17 angle (or 11-2 pipe angle for Retrofitters) on the frame.  


Retrofitters: remove the existing jumper pipe from the check valve to the 11-2 pipe angle. This pipe will not be used again in assembling the axle pump. 



Kitbuilders and Retrofitters: perform step 3 while fastening the LN5 lock nut loosely, for now, to allow enough play to tighten the compression fitting from the jumper pipe. Once the compression fitting is on tightly, then completely fasten the LN5 lock nut. 


6. Straightforward per Aster assembly instructions. 


7. Perform this after step 9. 


8. Straightforward per Aster because previous steps have led to the final mounting. 


9. Use P-4 set screws to fasten eccentric cam to axle. The eccentric cam should be centered between the frame and in line with the 6B-10 pump body. Put some machine oil on the eccentric cam. At this time, assemble the eccentric rod components over the eccentric cam with B10 screws. The instructions from step 7 can now be followed. 


Retrofitters can now fasten the 6B-9 pipe to the the 6B-16 end beam. Refit the 14-2 cab, the back three 6-5 break beams,6-4 break shoes and 6-6 break beam rods. Retrofitters will find that the axle pump will require a break-in period. 



The pipes under and inside the tender... If you have already installed the hand pump and saved the diagram, the illustration shows how to fit the return pipe inside the tender. As for underneath the tender, the pipes need to be crossed so that the pipes terminate directly in line with their respective connections on the engine. 


The supplied rubber hoses may be replaced with 1/8" inside diameter automotive vacuum hose and fastened with a black plastic clamp suitable for the outside diameter of the hose. 





1. To fill the boiler with the axle pump while running, close the bypass valve to block return flow to the tender. 


2. To return some water to the tender, open the bypass valve slightly when the sight glass indicates the boiler is approximately 2/3 full when running. 


3. To keep the sight glass indicating that the boiler is slightly more than half full while running, crack the valve open about 1/8 turn. Trial and error will define the optimum bypass valve position.



Appreciation is expressed to Joe Betsko for permission to post his article and pictures on www.SouthernSteamTrains.com   Article and pictures Joe Betsko.





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