Woodland Park Memories #7

I want to congratulate anyone who has hung in there with all of this little history of mine when I was a teenager. Thanks for reading.
Dad
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The G-16 MTC trains had a vacuum throttle and braking system. Vacuum is created in a carburetor equipped gasoline engine, especially when the throttle was at idle or low power setting when the throttle valve prevented a free flow of air into the intake manifold. The engine pistons would try to fill with air during the intake cycle with the throttle body preventing this. There was a tube that took this vacuum from the intake manifold and led to a tank, resembling a fuel tank that would accumulate the vacuum and provide it to the two cab controls, one each for the throttles and for the braking system. The throttle controlled both engines, with no provision for individual (A or B) control.

It's been noted that at least some models of the MTC G-16 series had in addition to the manifold system, an auxiliary, engine belt driven vacuum pump, at least on the A unit. The Woodland Park engines did not have this appliance.

The cab had two gauges related to this system. There was a reservoir vacuum gauge telling me how much vacuum 'pressure' that I had stored in the tanks, and for the braking system an applied, or train (brake) pipe vacuum level. The gauges used Inches of Mercury (similar to a common Barometer). A high value was about 15-18 inches or about 6-8 lbs/Sq In of pressure. That was the maximum that I had available to control the train, especially braking.

As you moved the control levers, either brake or throttle the control ported some of that vacuum pressure to either the bake line that ran the length of the train or to the engine throttles. Both systems used a cylinder, about 4 inches in diameter that moved a plunger into the cylinder as the air pressure outside pressed against the lower pressure (vacuum) inside the cylinder.

The throttles, having a pretty short distance from the control lever to the cylinders, responded pretty quickly to my movement of the levers. The train brakes, due to the length of the train, as well as the volume of air that had to be sucked out of the system had a pretty noticeable delay, between control application and braking affect.

You could feel the brake action, depending on how level the track was as the cylinders took affect starting at the engines and working back along the train cars length. On a full application stop, if the brakes went from released to full, the cars would chatter a bit as the slack in the couplings allowed the back of the train to run in to the front cars and engine a bit. This was caused by the vacuum working on the front car brakes, but hadn't yet sucked out the air in the back cars.

The train was not new and we had a period where we were always having to do repair on the brake hose couplings between the cars. The hoses were connected between cars with a set of rubber caps, that in theory would form a seal and preserve the vacuum pressure between cars as well as allow the cars to be uncoupled if required. They chronically leaked.

We'd have the brakes on full application, with the engines idling (highest vacuum) while stopped at the station and walk back and listen between the cars for any air leaks. When we found one, we'd apply some plastic tape. Over time we'd build up quite a number of layers of tape trying to squelch the vacuum leaks. I had an idea and approached the boss about solving the problem by removing the stock rubber caps and replacing the inter-car vacuum connections with lengths of common automotive fuel line hosing. I figured it was so rare that we actually uncoupled the cars, that the extra time when we did to remove the hoses wouldn't be an issue. That solved that problem for good. Maybe I should have asked for a bonus?

There was a very brief period when the brakes failed nearly completely. I was not the operator this day but was aware of the situation. During this time, we'd station two of our biggest ride operators up by the station and the train engines would be cut off as it entered the station area, just past the Great Northern locomotive. They would grab the cars of the slowly coasting train and stop the train through muscle power. Clearly, such a situation would not be tolerated these days. 

Another chore I took up on a series of slower days was to adjust the brake shoe slack on each of the cars. I over did the adjustment the first time, as my next run, I had to use a lot of throttle, even on level ground, just to get around. I backed off the adjustments and made sure on release, there was some slack on all of the brake shoe sets.

Brakes were important at Woodland Park. As I've noted earlier, the park grounds were anything but level and the trackage  traversed one hill or slope after another with changes of grade from downhill to uphill happening several times on the run. Only now, after seeing other park train layouts that are mostly level, or on very slight grades, and thinking back do I realize how much attention was required on this run to go back and forth between power levels and braking effort to keep the train going at the proper speed, gain momentum for the Elephant Barn hill and remain under control on downgrades.

As I've said, best job I've ever had.