Steam & Excursion > Testing a Franklin Trailing Truck Booster

A few days ago, there was a discussion of the Franklin trailing truck booster.  This is video of the booster from Frisco 1522 being run on compressed air during the locomotive's restoration on April 19, 1986.  Here is the mechanism that provided the extra power in a pinch.

Mary McPherson
Dongola, IL
Diverging Clear Productions

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Instructive, to say the least!  Thanks for the post.

Thanks for finding that Mary!  Shocked me to see the date on the tape.  Almost 39 years ago.  You should  have seen the guys when we first cranked it up.  Everything stopped and they all ran over to watch it.Geez I was in my 40s then.
If I recall we made one new bushing, checked clearances and tested it.  Always worked great, although very little used by us  Was sure handy when we did need it.  Rebuilt the cylinder cocks, lapped the throttle and did what was needed on the rest of the system.

When operating on air how the oil added to the valves & cylinders?

Gerry Gaugl
Ottawa ON

We used an oilcan here.  In service, it has a hydrostatic lubricator in the cab that feeds the steam line in.

What is the reduction ratio from the driven shaft to the powered axle?

Would the booster ever be used for a reverse move?

Gear ratio....
Reverse moves....


Gear ratio would be about four crankshaft rotations to one trailer-wheel
rotation---   4:1 

There is No Reversing capability, the booster's valve gear only has capacity
for one-way powered rotation.  And the booster engagement system, is 
all full-foreward, only.

Also, the primary compressed-air control valve --- that operates the engagement 
cylinders's timing and operations--- is mounted only on the engineer's reverse 
lever quadrant, and operates only at the quadrant's full-forward end.
One of the air control's functions is to open the stream supply to the booster,
once the gears are engaged.  The main steam supply to run the booster is
a large steam valve, with two positions: open or closed.  
The air-logic system opens the steam-supply valve only after the gears are engaged.

There are several air operated systems that function simultaneously to allow the
booster to go to work.  Removal of that control air pressure takes the gear-train
to a neutral, and disengaged position, and steam power to the booster is stopped 

To operate the control-air supply pressure to the booster's "air-logic" circuitry,
the engineer must first, put the reverse lever to it's full-forward postion.

As soon at the train accelerates, up to about 23-mph, and the engineer begins to
hook-up the valve admission timing, the  booster "control cam" ( on the reverse quadrant)
operating the booster's air system, is disengaged and loss of control-air pressure allows the
steam power to the booster to go to zero,

The booster's air cylinder engaging the idler-gear ( linking the crankshaft gear to the axle gear)
pulls the idler-gear away from the axle, and the booster pistons stop...no steam power.

It's a simple system to operate, but a complex, self-control system inside the booster
engine housing.

One final note:  The booster axle can have it's own sand pipes from 
the sand dome --- whenever the engineer "turns on"  the sanders, the booster wheels 
get their own sand.   On Reading 2100s, the hot water/steam 'rail washers' 
are mounted on the front  of the 1st tender truck's lower frame .. that rail-washer
is AFTER, the engine's booster wheel-set.  

Although it looks like condensed water vapor, the rail-washing benefit is actually the
very hot water from lower down, in the boiler.. about 350 to 400 degrees F.
How hot is condensed, boiled water, at sea-level ?
​
W.


 



Edited 8 time(s). Last edit at 01/22/25 13:51 by wcamp1472.

Wow, how very interesting. Thanks for posting.

Thanks, Wes. Always interesting.

Regards

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