Large Scale Central

throttle trouble?- ACC mogul

Electronics Live Steam
#1

Hi Folks,

I have an ACC Mogul (fuel tank in cab -era) that seems to have a throttle issue. Took the engine for a run yesterday after letting it sit for a few weeks parked. Everything seemed to be okay at first…

Then I began to notice I was not getting much power to the cylinders despite having sufficient boiler pressure and good valve timing. Upon stopping the loco to add water it also became clear that the throttle was not closing fully with normal torque. The Johnson bar was the only way to park the engine.

I notice the throttle “needle” appears to wobble a bit in its rotation…I seem to rember seeing this in my other ACC engines in the past. Is this normal?

I didn’t have a chance to back out the valve yet to inspect… What should I look for when I take it apart tonight? Is it just a failed o-ring?

Thanks in advance for any help!

Jeff

#2

Hey Jeff,

I’ve only had personal experience with two of Accucraft’s throttle assemblies and neither had a wobble. They just unscrew and pull out with the O ring remaining on the shaft. From the sounds of it maybe there is some debris stuck in there that may be preventing the needle from seating fully. The debris may be a chunk of deteriorated oring or something else. I would inspect down in the tube with a flashlight once the needle is pulled.

I would also think if the O ring has failed and is plugging things up that steam would be leaking out the end of the throttle. The O ring blocks the steam from exiting there. Rolling the removed needle on a table ( similar to checking your pool cue) will reveal whether or not it’s bent. Let us know what you find.