Merlin vs Turbosupercharged Allison

[Dave Hadfield]

The most accurate and factual info regarding Merlin vs Allison is Dan Whitney's book, "Vs for Victory". He takes the trouble to put these machines into their historical setting, adding a great deal of persepective.

It really is exceptional, and has tables that compare engine models and ratings, with explanations of the testing data and references. A vast amount of data, but well presented.

An expensive book, but fascinating.

Dave

[Dave Downs]

Did I read that article correctly? It said the V-1710B used in the dirigibles was REVERSABLE?

The way I take it was the engine itself could be reversed, not as in a separate opposite turning engine like the P-38.

How'd they do that!???

[shrike]

Did I read that article correctly? It said the V-1710B used in the dirigibles was REVERSABLE?

The way I take it was the engine itself could be reversed, not as in a separate opposite turning engine like the P-38.

How'd they do that!???

Just a guess, but with a duplicate set of idler gears, and a sliding splined selector gear in a special accessory case.

[Randy Wilson]

The book Vee's for Victory! is an excellent history of the engine but it was published a year or so after I wrote that article. As for the question of the Navy's airship V-1710-B engine being "reversible", the sources I had did suggest that the engine rotation was actually reversible. Looking at Vee's for Victory!, the following is found on page 30. "Meanwhile, Allison was hard at work on the V-1710-B Navy airship engine. This was a naturally aspirated, liquid-cooled V-12, directly developed from the GV-1710-A1, but equipped with devices to allow it to fully reverse direction and return to full power within eight seconds."

Randy

[Tiger Tim]

"...equipped with devices to allow it to fully reverse direction and return to full power within eight seconds."

I wonder how they dealt with reversing valve timing?

-Tim

[bdk]

I've seen an overprimed R-1340 in a T-6 run backwards for about 15 seconds... Maybe you just need a carburetor on the exhaust?

[eze240]

My bet is that there were a number of parts that didn't actually change direction...
Either it was a change in direction of the prop, which may not have been efficiently handled by a clutch system....ie: using a sliding idler gear arrangement....so, to change direction, the engine shuts down just long enough to come to a stop, kicks into reverse gear on the prop and starts again, it could probably be done in 8 seconds....
Or what? I have a hard time seeing it have two sets of cams, etc....being on a airship, it would have had to be as light as possible...
Here's a question....at the time that this would have been used, were fully reversing pitch props available?

[bdk]

Couldn't you just reverse the cam driveshaft as well? The cams and magnetos would thus always turn the same direction but the crankshaft rotation would reverse. That would solve the intake vs. exhaust reversal issue also.

You are right, a reversing gearbox on the propshaft would be easiest if there was a supercharger, but without it, reversing the camshaft geartrain would have been lighter since they don't transmit as much power.

I hope someone finds some documentation to provide the real answer!