Dianne Best Personal Web Page 2018
Re-Fitting the American
previous upgrades to the American, I STILL wasn't happy with the
performance of the crosshead pumps! There were too many problems:
1 - the pumps couldn't keep up with the demand for water in the boiler.
By calculations, they should have been able to deliver TWICE as much water as needed but they weren't doing that.
- The original design used graphite packing to seal the ram to the pump
cylinder, which was about the only option in the early 1960s, but the
packing nut was impossible to get at to adjust and replacing the
packing required stripping the crosshead off.
3 - The pump mounting was flimsy and allowed too much "lost motion"
4 - Although the pump ram was 0.25" in diameter, many of the passages in the system were substantially smaller.
So a re-design and rebuild of the crosshead pumps and feedwater system was in order.
The new pumps were machined from 3/8 x 1" brass bar with stainless steel rams.With
the cylinder bore of 0.266", that left only 0.050" for wall thickness
and, when drilling to a depth of 3.25" that meant great care was
required to keep the drill straight. Sometimes being lucky is better
than being good and I was. 0.266" diameter was a good fit for a 3mm ID,
2mm cross-section O-ring but the small O-ring size could not be
stretched over the 0.250" ram without damage the end of the ram was
turned down and threaded #6-32 and a nut was turned down to slightly
less than 0.250" to allow the O-ring to be slipped over the end before
installing the nut.
rear crosshead support had to be removed and the opening for the pump
enlarged to accommodate the new pumps and a mounting hole for #4-40 was
drilled and tapped directly into the main frame of the locomotive.
Fortunately a frame stiffener provides a doubler at that location.
With the pump installed it was time to put the crosshead back together and move to the other side.
second pump was fabricated and installed with little difficulty and it
was on to making 4 check valves with minimum resistance to water
The lower bodies were made from 3/8 hexagon brass bar drilled and tapped 3/8-24 and drilled through at 1/4".
tops were made from 3/8 round brass bar threaded 3/8-24, drilled
through at 1/4", and fitted with a brass hex nut from the same bar
stock as the body.
top components were soldered together. The 1/4" tube was allowed
to extend through the top to act as a ball stop and was filed with
crossed passages to allow the water to flow through when the check
valve is open.
t\he pumps mounted, it was on to installing the delivery plumbing. The
rubber tube allows the pumps to move as they require. One T fitting is
for the engineer's side pump and the second for the fireman's side
pump. (It wasn't practical to increase the size of the delivery tube to
the boiler check valve because the boiler check is 1/4" and adding a
second one or replacing the existing check with a larger one
would require disassembling the entire locomotive!) The discharge tube
going off to the right goes to the bypass valve in the tender.
the engine the intake line was changed to 5/16" tube and a T was
fabricated with 5/16" inlet and 1/4" outputs to the pump. Again,
rubber tubes allow for some pump movement.
The 5/16" inlet line extends to the rear buffer for connection to the tender.
- lake testing
- pressure/delivery test
Return to my Home Page