I'd say it's a safe bet trailer-truck boosters always had the idler gear, so they could be cut out. The 1924 Franklin booklet so describes them. Dunno whether that applies to tender boosters as well-- maybe any engine that had a tender booster was thereby limited to 20 mph?
This book shows no rocking or idler gears on the booster engines. Maybe later than 1927 the gear train was added?
Pete
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IIRC this same question came up maybe a year ago, you could do a search of the forums to see. Anyway, seems to me the concensus was that no, it had virtually no drag effect. Apparently the relative unpopularity had more to do with maintenance problems.
A steam locomotive that wasn't under power would roll pretty freely despite having cylinders and siderods. I recall reading somewhere that when roller bearings came along engines became so free-wheeling that 2-3 men could move even a big engine just by pushing on it. Frank King in one of his books noted that the DM&IR almost lost one of their first Yellowstones into a swamp, because it started to roll down a track that everyone had always thought was flat so they didn't bother to tie it down. Turns out it had a tiny grade to it that was enough to get the big engine rolling.
Hi guys.
I borrowed a 1927 locomotive cyclopedia ( Truly amazing book) and was looking at trailing truck and tender booster engines. What I had noticed was that there was no way of disengagement of the driving engine from the wheels. When the booster is working steam is introduced to the cylinders just like the main drivers. When steam is cut the wheels and reciprocating machinery is still moving as long as the wheels are turning. Wouldn't that be a tremendous drag on the locomotive? You would think there would be some sort of clutch or sliding gear set to disengage the engine? Looking at the parts breakdown there appears to be nothing to keep the piston and rods from moving while the wheels turn. I can see why they were not very popular.
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