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Aviation’s Largest Piston Engine (2016)
11–20 of 51 posts
Re: Aviation’s Largest Piston Engine (2016)
#12>At full power, the XR-7755 generated a tremendous amount of heat. Speaking as a full time engine mechanic for a small chain of midwestern repair stores, this is the death-knell of every heavily customized car. Heck, 3/4ths of the engineering for a Dodge Hellcat or Mustang cobra is just to keep the thing cool enough that the driver isnt chased out of the cockpit. You cant idle them the same way you idle a Toyota...th…
Take the hood off, bring a cooler of ice water, don't get stuck in traffic, stop every 10-15 minutes to cool off. Problem solved.
I had to do this with my first car which had a leaky cooler :-). Always had a bottle of water with me.
Re: Aviation’s Largest Piston Engine (2016)
#13120 liter displacement. 4x9 = 36 cylinders and many valves and sparks plugs in each.
As comparison an early generation single spool turbojet has pretty much one moving part.
Nowadays there might be two or three spools and moving vanes and a thrust reverser.
But aviation would never have been possible for the masses with piston engines.
Re: Aviation’s Largest Piston Engine (2016)
#14>At full power, the XR-7755 generated a tremendous amount of heat. Speaking as a full time engine mechanic for a small chain of midwestern repair stores, this is the death-knell of every heavily customized car. Heck, 3/4ths of the engineering for a Dodge Hellcat or Mustang cobra is just to keep the thing cool enough that the driver isnt chased out of the cockpit. You cant idle them the same way you idle a Toyota...th…
I'm not seeing how crank and cam specs significantly affect cooling at idle all else being equal. Any cooling system that can work under load will be fine at idle. Edit: For something like a race-car that's trying to minimize weight/power loss by running the minimum radiator/fan necessary and depending on airflow from movement (or rely on the fact that you're only running 1/4mi at a time) I can understand. Still, tha…
Airflow.
Powerful motors will sometimes run well enough at speed but overheat at idle. For example, after receiving an upgrade like a camshaft with more radical timings.
One key point: you can increase the size of a radiator or oil cooler but that helps a lot more when the vehicle is actually moving.
Re: Aviation’s Largest Piston Engine (2016)
#15>What was truly unique about the cams was that there were two sets of lobes for each cylinder. One set of lobes optimized the operation of the engine valves at high power settings VTEC, yo. In in the 1940s no less. There's tons of tech that was well understood for WW2 aviation that finds its way back into land transportation given enough time. Adding water and alcohol blends to the intake charge to reduce temperature…
A large part of these technologies making their way into consumer automobile engines was advances in material science, lubrication, manufacturing, etc, that allowed for them to exist economically and reliably. Those WW2 era piston engines were horrifically expensive, and required dozens to hundreds of hours of maintenance per hour of flight time.
Sleeve valves could enable higher compression ratios without detonation, for higher efficiency? I guess there is the NOx to consider nowadays though.
Re: Aviation’s Largest Piston Engine (2016)
#16Sometimes I think about aerial bombardment, and what that really meant during that period of conflict. When you think about the effort to concoct the compounds for the air war, and drop them on cities, with no guidance like lasers or anything, and then you look at the sheer tonnage dropped, and how indiscriminate it really was, you wonder how aerial bombardment is at all distinguishable from chemical weapons. It real…
It's an arbitrary distinction a lot of the time, really. But you have to draw the line somewhere. I just wish we could draw the line at eliminating all war and violence, instead of playing semantic games.
It's super bad if some bad guy destroys innocent lives with chemical weapons, but totally fine if we drone strike them. Doesn't make much sense, although in this crazy world things aren't as black and white as we'd like.
Re: Aviation’s Largest Piston Engine (2016)
#17Even if you ignore the heat and the power/weight ratio, reliability starts to become a problem. Adding more smaller piston engines improves reliability and safety in long flights.
The number of moving parts and the complexity of the piston engine compared to a gas turbine is significant.
Re: Aviation’s Largest Piston Engine (2016)
#18Sometimes I think about aerial bombardment, and what that really meant during that period of conflict. When you think about the effort to concoct the compounds for the air war, and drop them on cities, with no guidance like lasers or anything, and then you look at the sheer tonnage dropped, and how indiscriminate it really was, you wonder how aerial bombardment is at all distinguishable from chemical weapons. It real…
It's an arbitrary distinction a lot of the time, really. But you have to draw the line somewhere. I just wish we could draw the line at eliminating all war and violence, instead of playing semantic games. It's super bad if some bad guy destroys innocent lives with chemical weapons, but totally fine if we drone strike them. Doesn't make much sense, although in this crazy world things aren't as black and white as we'd…
Who says it is totally fine when we drone strike them? There are reviews and large numbers of staff who do their best to minimize drone striking of innocents. Chemical weapons on the other hand are designed to maximize striking innocents.
Re: Aviation’s Largest Piston Engine (2016)
#19Sometimes I think about aerial bombardment, and what that really meant during that period of conflict. When you think about the effort to concoct the compounds for the air war, and drop them on cities, with no guidance like lasers or anything, and then you look at the sheer tonnage dropped, and how indiscriminate it really was, you wonder how aerial bombardment is at all distinguishable from chemical weapons. It real…
The taboo against chemical warfare developed after a war that involved mass bombardment with both chemical weapons and explosives. I’m not qualified to discuss the reasons, but the people on the pointy end of the stick seem to have come away thinking that there’s a significant difference.
Re: Aviation’s Largest Piston Engine (2016)
#20>What was truly unique about the cams was that there were two sets of lobes for each cylinder. One set of lobes optimized the operation of the engine valves at high power settings VTEC, yo. In in the 1940s no less. There's tons of tech that was well understood for WW2 aviation that finds its way back into land transportation given enough time. Adding water and alcohol blends to the intake charge to reduce temperature…
A large part of these technologies making their way into consumer automobile engines was advances in material science, lubrication, manufacturing, etc, that allowed for them to exist economically and reliably. Those WW2 era piston engines were horrifically expensive, and required dozens to hundreds of hours of maintenance per hour of flight time.
They were also ridiculously unreliable and had the tendency to just catch on fire. Acceptable losses in wartime. Not so much elsewhere.