Steam & Excursion > Test: Booster discussion.

( I had originally posted this on my my I-phone,  bad choice..
   Trying to clean it up on my I-pad... for  clarity..)

 “If something can go wrong, it will go wrong” : Murphy.

 So, it’s possible that IF something went seriously wrong in a booster,
there is a possibility of a derailment caused by a locked-up booster problem
and gear-drive.

So, Franklin ( vendor of tye locomotive booster) devised a "weak-link" in the system
that would fail-safe, protect the booster engine, and the damaged parts would not
 interfere with the free motion of the trailer truck’s axle.

So, to elaborate... the booster engine is a 2- cylinder Steam engine that only
rotates in one direction —- forward.

At the engineer’s position is an air pressure control valve that operates the booster,
when needed. The ONLY way to activate the Booster is to operate that valve by
putting the Engineer’s valve gear lever in full-forward position.  
There is a Booster-Operate air-control valve at the very front of the
Power Reverse lever's rack, in font of the engineer.

The preps and steps to energizing tte booster set the stage for the power-step.
Once the idler gear has been moved on it's trunion levers, and engages 
both the trailer truck axle gear and the pinion gear of the booster engine---
the only thing needed is steam that powers the main cylinders, as well as the booster.
There is a cutoff valve in tye steam supply to the booster ---- but, when preparing 
to power tge train, that valve is opened, by the set-up steps towards using the booster...

When ready, the engineer opens the throttle .... and live steam flows to the main pistons,
and back to the booster engine...  The live-steam line to the booster is generally on the
fireman's side of the loco --- from the cylinders to back, under tye cab to the booster.
There is a matching exhaust-steam pipe on the engineer's side of the loco;
typically, ending with  it's own exhaust stack next to the main exhaust stack.

As the engineer accelerates his train, he moves the valve gear lever out
 of the “all-the-way-forward”, position, and the booster air-control valve for controlling
compressed air for the booster circuit's operation drops away, removing the controlling
air pressure…and also closes the steam supply piping, from the front cylinders.

The air control system in the Booster circuit is a series of timing air-volumes
and the sequence controlled 'Logic’ of the multiple control air pistons, timing tanks,  
and ports.

The 2-cylinder Booster engine has a crankshaft, with each piston rod connected
at its outer ends and rotates the crank shaft, with the 2 cranks at 90-degrees spacing
from each other.

Between the two cranks are the crankshaft bearings and pinion drive-gear gear,
of a few teeth,  it engages with an ‘axle-gear’ with 4 times the number of gear teeth.
If the pinion gear has 15 teeth, the axle gear has
60-teeth. Giving the pinion a 4:1 mechanical advantage.

However, in order to dis-engage the crankshaft from the axle, an idler gear is used.
The idler gear is a medium sized gear that is supported on each end of
it’s axle-bearings, by two rocker-levers,---or trunion arms---  pivoted on the pinion
gear’s crankshaft.

The idler gear stays spinning, as it’s always engaged with spinning pinion and
crankshaft...During 'warm-up' periods, the idler spins, but is dis-engaged from
the trailer truck's axle/gear.

When the engineer engages the booster control valve, at his full-forward --- reverse gear---
position, an air cylinder at the pinion/idler shaft, operates, and swings the trunions & idler,
forward, to engage the 60-tooth axle gear…. The booster is now ‘engaged’ …
and waiting for power Steam from the engineer's throttle, to run the booster’s pistons.

He could be starting after a station-stop,and have the booster engaged,
waiting for the main throttle to be opened..

The power Steam comes from the cylinder steam line feeding the left, main piston and
crankpin.   As the engineer opens the engine's throttle, Steam powers the main pistons,
and also powers the booster engine, under the loco cab….

A small timing reservoir in the air-control booster-logic, closes the booster-engine’s
cylinder cocks, after about 30 seconds.  It's an automatic, self-timing booster feature.

When the train gets up to speed, and the engineer  “hooks-up” the reverse-lever,
that action drops away the booster “engage” air pressure valve, and stops the steam,
as well as moving the idler-gear’s trunion arms, and the idler, lifts and falls back,
but still meshed to the booster crankshaft---freeing-up the trailer axle… to freely
allow track speed.

For clarity:  when engaged, a small air piston and cylinder moves the idler-gear's trunion arms 
so that the idler gear moves forward, to it's functioning position --- linking 
all 3 gears to drive the rear axle of the booster truck.

IMPORTANT:
The two, gear trunion-arms, are the fail-to-safe feature that prevents possible axle lock-up.
When impatient engineers try to re-engage a booster on a slowing train, the 
trailer-truck's axle is turning too fast and the booster gears are spinning slower ---
that whole gear train gets over-strained ---- those two trunion arms carrying the idler
gear are designed to collapse --- protecting the train and also protecting the 
booster engine's critical parts.  Upper speed limits to safely "re-engage" is no more than 
about 24 mph.  Any faster,  and the axle gear is rotating too fast to engage the slower,
booster pinion gear.  The bent, broken trunion arms are sacrificed to prevent more 
extensive damage --- by design...

  If you have a booster equipped engine.... now is the time to have spare trunion-arms
on your shelf, as well as spare idler-gears and spare shafts, and spare trunion-operating
air cylinders, all set and ready to go !

I hope 614's new owners have Strasburg also provide them with spare trunion parts...
During 614's "winter coal-trains episodes",  614's booster was attempted to be 
re-engaged while travelling too fast ----- and the Booster's fail-safe feature 
protected the booster engine and there was no locked-up trailer-truck axle.
However, the 614's booster will not, now, operate.
There is no "clutch" in a loco's Booster..

Strasburg, if the 614's new owners decide, will have some reconstruction 
work in the booster's gearing and the destroyed trunion arms.

HINT: Having additional spare trunion arms on-hand, will save time in case of another, future,
attempt to 'test' the Booster's safety-feature.



Edited 3 time(s). Last edit at 01/18/25 17:32 by wcamp1472.

wcamp1472 Wrote:

> During 614's "winter coal-trains episodes",
>  614's booster was attempted to be 
> re-engaged while travelling too fast ----- and the
> Booster's fail-safe feature 
> protected the booster engine and there was no
> locked-up trailer-truck axle.
> However, the 614's booster will not, now,
> operate.
> There is no "clutch" in a loco's Booster..
>
> Strasburg, if the 614's new owners decide, will
> have some reconstruction 
> work in the booster's gearing and the destroyed
> trunion arms.
>

No destroyed trunion arms on 614 in '85, a tooth on the idler gear broke.

Either way, its a BIG job...
For one moment of careless thinking.

A little slower engage-speed might have made the difference,
and possible success.  Boosters can stay engaged at faster track 
speeds;  but,  to re-gage safely, follow manufacturer's instructions...
& attempt re-engage at slower than maximum recommended RPMs.

I also suspect that this attempt was part of a pattern of 
reengage-while-powering practices... and they got sloppy...
Definitely,  'operator error'

​W.


 



Edited 1 time(s). Last edit at 01/19/25 04:21 by wcamp1472.

I wasn't present when the 614's booster broke some teeth of the bull ring gear so I can't testify to the exact cause. The crew told me it occured when the booster had been engaged for about 15 minutes and they were doing about 15 mph.

    Of all the times I was honored to be the hogger on the 614 I only needed to engage the booster 3 times ( 17 mile grade, Sandpatch grade and starting a 21 car train out of Ellicott City station. Only 3 times...but....we would have failed in all 3 without it.Therefore it's a tool you want in your tool box just in case.

    Ross Rowland