Not sure at all how you can tell it seemed anemic from the video. Idicated climb rate was 1780fpm, and it was an intersection departure. That hanger that I panned over to after we were in the air is 1000' from the interesection we departed from. Probably 5 or 600 feet roll I would estimate.captainron http://www.youtube.com/watch?v=oM8I...related&search=
I watched the take-off run (inside) and from the start of the T/O run to approx. 500' AGL looked like about 50-55 seconds. Seemed pretty anemic to me. Don't know what all the other conditions were, though.
I noticed your altimeter before take-off indicated 900'MSL. Near the end of the video, and about 50-55 seconds after the engine went to full power, the altimeter was indicating 1400'MSL, or a 500" gain during that period. I assume you weren't deliberately climbing "flat" because of CHT issues with your water-cooled engine.cjensen said:Not sure at all how you can tell it seemed anemic from the video. Idicated climb rate was 1780fpm, and it was an intersection departure. That hanger that I panned over to after we were in the air is 1000' from the interesection we departed from. Probably 5 or 600 feet roll I would estimate.
captainron said:I noticed your altimeter before take-off indicated 900'MSL. Near the end of the video, and about 50-55 seconds after the engine went to full power, the altimeter was indicating 1400'MSL, or a 500" gain during that period. I assume you weren't deliberately climbing "flat" because of CHT issues with your water-cooled engine.
cjensen said:Well, between here and RB, I feel like I've learned my lesson with posting videos. I thought this would be a neat "fun" idea, but it did nothing but spark arguments and speculation with endless comparison about performance.
I've gained some experience in Lyco and Subie RV's, and no matter what you think you see in the video, it'll never fair well with anything I can say about it, bad or good.
I'll be removing the videos.
Bummer.Yukon said:Very disappointing Chad. Book burning went out of fashion years ago.
No, you're not interested, but others are, and are viewing them with critical eyes. Most of us are not "Lycoming fanatics", but we are just looking for solid, proven, and safe performance from our 25K purchases. If we were after all-out performance, we wouldn't be building Vans. What I want, and what I suspect most of us want is the excellent performance that these planes provide, the satisfaction of building it yourself, and the peace of mind that comes from the realization that the powerplant is NOT a somewhat risky unknown.cjensen said:I can only report what I saw personally in each airplane, and I'm not interested in everyone breaking down the videos.
Thanks though.
cjensen said:Here are two video's from Egg's site. Not the best, but they do show some performance. I can't speak for either one since I was not there. I'll repost a couple of the video's along with the 9A takeoff sometime this weekend.
Gary Newsted's 4 cyl Gen3
Andy Parish H6 Gen3
flyeyes said:I really like the idea of auto-engine conversions. I like the water cooling, smoothness, and potential economies of scale, but I haven't seen one that performs as well yet wasn't either very labor intensive (Tracy Crook) or expensive (Mistral)
Where does all that horsepower go? I'm sure that same engine, if you had left it in the car, would do 0-60 in much less time than 8 seconds. And the car probably weighs 3250 pounds and doesn't get any "lighter" on its feet the faster it goes! What does your RV-8 weigh when it's getting this performance?rv6ejguy said:My Sube RV does 0-60 knots in 8 seconds without holding it up on the brakes and without ramming the throttle ahead.
In a car, the engine's power is transmitted via transmission, CV joints etc. The transmission is very efficient, so the vast majority of the power produced by the engine is available as thrust horsepower. On an aircraft, the engine's power is sent to the propeller, and the prop creates thrust. But, the prop is optimized for high speeds, which is where the aircraft spends most of its time. The prop efficiency is almost certainly less than 60% during the takeoff, and it is probably less than 50% during the early part of the takeoff roll. So, if the prop efficiency is less than 50%, that means that less than 88 hp of the 175 hp is actually used to produce thrust. This is one big reason why an aircraft will have worse low speed acceleration than a car of similar power to weight ratio.captainron said:Where does all that horsepower go? I'm sure that same engine, if you had left it in the car, would do 0-60 in much less time than 8 seconds. And the car probably weighs 3250 pounds and doesn't get any "lighter" on its feet the faster it goes! What does your RV-8 weigh when it's getting this performance?
In the car, horsepower is sapped by the transmission, 4WD running gear, air conditioning, exhaust system, etc..
On your plane, the only thing you're driving is the re-drive and a propeller.
Where's the performance?
captainron said:Where does all that horsepower go? I'm sure that same engine, if you had left it in the car, would do 0-60 in much less time than 8 seconds. And the car probably weighs 3250 pounds and doesn't get any "lighter" on its feet the faster it goes! What does your RV-8 weigh when it's getting this performance?
In the car, horsepower is sapped by the transmission, 4WD running gear, air conditioning, exhaust system, etc..
On your plane, the only thing you're driving is the re-drive and a propeller.
Where's the performance?
Yukon said:Apples to apples Kevin. Doesn't this apply to Lycoming aircraft also? How does Van's claim 350 feet for takeoff for an RV-7 on 88 hp???????
szicree said:I'm not following this. First off, will a Subaru car really do that much better that 8 seconds? Secondly, why would it matter if a car was "lighter on its feet"? The car's (or plane's) inertia is a function of its mass which is constant regardless of lift, and is the main thing preventing acceleration. Finally, the fact that the prop is operating in air makes it a completely unfair comparison unless you want to put the tires on some slippery surface.
In any case, I can't for the life of me understand how there can be hundreds of these conversions flying and not one single set of dyno data.
szicree said:I'm not following this. First off, will a Subaru car really do that much better that 8 seconds?
Yukon said:So that we can know the answer to these questions, I will pay for the dyno test if somebody will make their engine available. Speak up Subie guys!
szicree said:I am certainly no engineer, but the actual rolling resistance offered by my car's wheels against the pavement is a small thing. On the other hand, I would say that the moment of inertia for those wheels is a big thing. Also, I admit that I am ignorant of the finer points of how horsepower is converted to thrust but consider this experiment: Take the grill and radiator off of a 300 hp car to expose the cooling fan, stick car in neutral, floor it and hang on while the car just sits there. If the car has an engine driven fan and no fan clutch all of the horsepower should be going to that fan, but nothing happens. Why not?
captainron said:Gee, where to start here. You are only developing HP when there is a means of absorbing it. Think of an engine on a dyno, you could start the engine up and rev it to its redline, but how much throttle would that take? Probably not much. Now load the engine to the point where you have to have full throttle in to keep the RPM up and now you are doing some work (HP). Think of how you select a fixed-pitch propeller; you want the one that will allow the engine to reach its redline but no more, when flat-out at standard day, sea level conditions. Too much pitch and the engine can't make RPM=HP loss. Too little pitch and you have to reduce throttle so not to exceed redline=HP loss (your car fan theory). The proper propeller will absorb all the engines available HP and convert it to thrust.
Yukon - I was answering a question about why the difference in performance between cars and airplanes. But, yes, a Lycoming powered aircraft would have much worse acceleration than a Lycoming powered car, assuming the engine in the car provided propulsion power by driving the wheels through an appropriately geared transmission, etc.Yukon said:Apples to apples Kevin. Doesn't this apply to Lycoming aircraft also? How does Van's claim 350 feet for takeoff for an RV-7 on 88 hp???????
szicree said:Well said and I think I get it, but I guess I'm picturing a propeller driven vehicle starting from a dead stop as more similar to a high powered car with a locking dif. If you stomp on the gas hard enough you can get the car to just sit there and spin the tires. No over rev, just burning rubber and a car moving slowly forward.
captainron said:.....All this is Lycoming's bread and butter....How many car engines promise to give you full rated HP for the life of the engine and warranty it? It's your call, but then again it's your b**t hanging up there too!
captainron said:Car engines may produce the HP needed to drive airplane propellers, but car engines weren't designed to operate this way. Your car may have 300 HP, but it may take only 45 or so HP, and 1900 RPM to keep it rolling down the highway at 70 MPH. The 300 HP is there, but certainly not full time. Their components were never designed for full HP all the time. Think about it; do you think that car manufacturers would expend their design resources, provide the metallurgy and the stress analysis required thinking that a few of them might end up in airplanes?
rv6ejguy said:This misconception has been visited many times before. The statement is totally unsupported by fact. Standard testing and validation today sees auto engines pushed to far higher standards than certified aircraft engines require. They are quite capable of running at 75% power for many hundreds of hours. Proven on the test tracks, dynos and in aircraft as well. You can search previous threads for the numerous details I have posted of these tests. The EJ255 (STI) has produced a staggering 960hp with stock case and crank- the equivalent of 2300hp from an O-360!
The design, manufacturing, metallurgy and QC far exceed what is employed in aircraft engines.
Running along at 4000-4500 rpm all day long is a non-issue with modern auto engines.
The first Egg H4 Glastar just past 450 hours with no issues.Yukon said:Show me the beef!
If a guy can bench press 960 lbs once, how many times do you think he could bench press 250 lbs?Yukon said:...This is a "red herring" argument. How long did it produce 960 hp? A dragster will produce 7000 hp, but after a couple of runs it's torn down. So what?...
rv6ejguy said:This misconception has been visited many times before. The statement is totally unsupported by fact. Standard testing and validation today sees auto engines pushed to far higher standards than certified aircraft engines require. They are quite capable of running at 75% power for many hundreds of hours. Proven on the test tracks, dynos and in aircraft as well. You can search previous threads for the numerous details I have posted of these tests. The EJ255 (STI) has produced a staggering 960hp with stock case and crank- the equivalent of 2300hp from an O-360!
The design, manufacturing, metallurgy and QC far exceed what is employed in aircraft engines.
Running along at 4000-4500 rpm all day long is a non-issue with modern auto engines.