Jacobs Dr.1 - Allied Engines and Performance

[StephenLawson]

Originally Posted by Byron

..... That sounds rather foolish. Just a thought - could Achim Engels perhaps be persuaded to approach the possesor of these interviews?
Byron

Prejudices come in all shapes and sizes. There is a common belief held by some that if you are not German you don't need to publish German history. There are even a few of the "Silent old Birds" that come here and never speak that hold to this narrow view point. Not all mind you but some few. It is unfair to publicly ask Herrn Engels to possibly violate his relationship with others to give us or anyone a scrap of information.

This next bit is for public consumption not just to Byron.
Have you ever thought of writing an authority and ask them to send you everything they have on a given topic? The great A.E. Ferko is known to have stated "What I have paid for with money or in trade is mine. How is it you think that what is mine translates to you?" The "network" of WWI aviation historians is based in both mutual trust and mistrust. A noted Silent Old Bird who peers in here from time to time and occassionally sends me e-mails is known to have visited another Crusty old bird. One night while Silent was supposedly sleeping Crusty was up pulling photos from his files to hide them from Silent. The names have been changed to protect me from their wrath. And to the rat b*st*rd who stole the aviation photos from Jacobs album when Neal O'Connor purchased them, I still know what you did.

[Romani]

Originally Posted by Byron

..... I've noticed that rotaries tended to fall off in performance with altitude to a greater degree than in-line engines.
Byron

It's because the same reason radial air cooled engines performed worse than in-line water cooled engines in WWII. That always perplexed me until an engineer explained me why.

All engines loss performance the higher the altitude because air gets thinner and thefore there's less oxygen going into the combustion chamber. You will notice this in a car in a mountain road.

But in addition, air cooled engines suffer because of basic thermodynamics. With thinner air , there's less cooling fluid that can be circulated around the cylinders, for the same effort the engine overheats sooner. This loss in power outweighs the marginal benefits of less air resistance and the cooler ambient temperature.

For this reason the Fokker Dr I was well liked during the spring offensive of 1918, because the low cloud ceiling meant combat took place at low altitudes were the engine could be used to its full power.

Originally Posted by Romani

It's because the same reason radial air cooled engines performed worse than in-line water cooled engines in WWII. That always perplexed me until an engineer explained me why.

All engines loss performance the higher the altitude because air gets thinner and thefore there's less oxygen going into the combustion chamber. You will notice this in a car in a mountain road.

But in addition, air cooled engines suffer because of basic thermodynamics. With thinner air , there's less cooling fluid that can be circulated around the cylinders, for the same effort the engine overheats sooner. This loss in power outweighs the marginal benefits of less air resistance and the cooler ambient temperature.

For this reason the Fokker Dr I was well liked during the spring offensive of 1918, because the low cloud ceiling meant combat took place at low altitudes were the engine could be used to its full power.

Thank you Romani. A very interesting explanation which I had not considered.

Two things I believe that Vosses Triplane was delivered to him with a leRhone. Is there any evidence for the types of Clerget used by Jacobs? What concerns the archieve I can help if you show where, I am German.