a question about rotary control

[jlan5031]

I've a question about throttle control on WWI radial engines. Were they all controlled by blipping, or were some hand throttle controlled? I've noticed that some of radial ac have a cockpit throttle lever which will move in response to my joystick throttle. Anyone know?

[Panama Red]

Are you talking about "radial" engines or "ROTARY" engines. Rotary engines used the blip switch for "off & on". The primative throdles did not always work correctly on rotary, so the blip switch was safer.

[jlan5031]

I was talking about rotary. Thanks for your answer. I'll take it as definitive and keep blipping.

[Bullethead]

Rotary engines used the blip switch for "off & on".

 

IIRC, there was also a way to make only some fraction of the cylinders fire, so you had settings for like 25%, 50%, and 75% power as well as on/off. I'm not entirely sure how this worked, given the inability to control fuel flow to individual cylinders. It might have been a magneto setting that disabled the spark in chosen cylinders, but you'd think that would fill the cowlling up with atomized fuel within its explosive limits.

[Hasse Wind]

IIRC, there was also a way to make only some fraction of the cylinders fire, so you had settings for like 25%, 50%, and 75% power as well as on/off. I'm not entirely sure how this worked, given the inability to control fuel flow to individual cylinders. It might have been a magneto setting that disabled the spark in chosen cylinders, but you'd think that would fill the cowlling up with atomized fuel within its explosive limits.

 

Yeah, I've read about such technology being used at least in some rotaries. For example in a 9 cylinder engine, the pilot could choose to keep 1, 3, 6 or all 9 cylinders in action. One very important and useful method of controlling RPM in rotaries was adjusting fuel mixture, and it was common practice with many aircraft to cut off fuel completely when landing.

 

As far as I know, rotary technology progressed through the war so that by 1918 throttles were the norm in rotary engined aircraft, but blip switches were of course still used.

[carrick58]

Didnt they do that in a auto engine a while back 4 cyn to 6 or 8 ?

[BigAl56]

Didnt they do that in a auto engine a while back 4 cyn to 6 or 8 ?

I recall something like that, as a fuel saving measure.

[Bullethead]

Didnt they do that in a auto engine a while back 4 cyn to 6 or 8 ?

 

They do it today in most truck engines. There's a thing called a "jake brake", originally made by the Jacobs company but now by others It not only cuts off fuel to some number of cylinders, it also alters the valve timing so the dead cylinders act as air compressors. Thus, those cylinders eat the truck's kinetic energy, allowing it to safely negotiate steep downgrades and also to stop more quickly on the level.

 

http://www.jakebrake.com/

[Bletchley]

I was talking about rotary. Thanks for your answer. I'll take it as definitive and keep blipping.

 

With the exception of the early Gnome rotaries (few of which were still in use by mid 1915), the blip-switch was supposed to be used only when the engine was already throttled back to idle - either on the ground, when taxiing, or in the air when throttled back for landing. The blip-switch was retained on all rotary engines because of the high idle speed of the rotary - most rotaries could not be throttled back much below 600 rpm on the ground or 800 rpm in the air. I have seen some evidence that the blip-switch was sometimes used in combat, but officially the use of the blip-switch at high engine speed was frowned upon because of the damage that it caused to the engine. Blipping the engine could also lead to flooding of the engine with excess fuel, which could lead to the engine cutting out for several seconds or even a fire under the cowling - not something modelled in OFF, but a powerful deterrent to use in combat. I model late rotary management in OFF by using the number keys across the top of the keyboard, using 6, 8 and 0 only (most WWI pilots had 'preset' positions of the throttle/fine adjustment for idle, cruise, and full power, and stuck to these), and only use the blip when throttled down to the '6' position. The mixture control can then be used for fine control of the engine speed, as well as altitude changes.

 

Bletchley

Edited July 27, 2010 by Bletchley

[Creaghorn]

With the exception of the early Gnome rotaries (few of which were still in use by mid 1915), the blip-switch was supposed to be used only when the engine was already throttled back to idle - either on the ground, when taxiing, or in the air when throttled back for landing. The blip-switch was retained on all rotary engines because of the high idle speed of the rotary - most rotaries could not be throttled back much below 600 rpm on the ground or 800 rpm in the air. I have seen some evidence that the blip-switch was sometimes used in combat, but officially the use of the blip-switch at high engine speed was frowned upon because of the damage that it caused to the engine. Blipping the engine could also lead to flooding of the engine with excess fuel, which could lead to the engine cutting out for several seconds or even a fire under the cowling - not something modelled in OFF, but a powerful deterrent to use in combat. I model late rotary management in OFF by using the number keys across the top of the keyboard, using 6, 8 and 0 only (most WWI pilots had 'preset' positions of the throttle/fine adjustment for idle, cruise, and full power, and stuck to these), and only use the blip when throttled down to the '6' position. The mixture control can then be used for fine control of the engine speed, as well as altitude changes.

 

Bletchley

 

precious information as always bletchley. thank you. i'll do it like that with rotaries in future as you do:salute:

[jlan5031]

Bletchley,

Thanks for the information-very interesting. I too will make use of it.

[RAF_Louvert]

.

 

jlan5031, if you would like some more bits of wisdom on this subject from Bletchley here is the link to a related thread I started some time back:

 

Setting Up And Using Magneto Blip Switches

 

Hope you find the info useful.

 

Cheers!

 

Lou

 

.

[jlan5031]

RAF_Louvert,

Thanks for pointing me to the thread. It was very interesting. I'm going to try the magnetos to see what happens.

[Bletchley]

There are some more detailed notes on 'control of rotary engines' that Shredward re-posted from Phase 2 in the OFF Historical Archive, if anyone wants more detail on the control of different types of rotary engine:

 

http://combatace.com/topic/37648-great-war-historical-archive/ p.16

 

Bletchley

Edited July 28, 2010 by Bletchley