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Chevy LS2 and Trans??? any real issues besides weight
Hey guys i'm a new pilot that really wants to build his own craft. help
me with this one issue. I want to use a chevy ls2 or ls7 as the power plant in my craft. now looking at everything including the hp/torque curves i've decided running the engine around 3100 rpm should give me around 250 hp with good torque now getting that power to a propeller seems to be an issue. I'm wondering besides weight would there be any real issue using the associated transmission locked in gear maybe 3rd/4th/5th gear whichever is just under 1:1. it would seem the car tranny has been engineered to convert the engine motion into the spinning i would need to propel the propeller. plus running the engine at 3100 rpm it would prob last longer than i will. the aircraft i want to design is a very cab foward design with a pusher prop and the engine would be mounted approx mid craft. i'm new at this and besides having an engineering background i really have no exp building an aircraft so any opinions would be helpful thanx Mrv |
#2
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Chevy LS2 and Trans??? any real issues besides weight
A car transmission is not a suitable propeller redrive, neither for a
car or a boat. Study marine practice carefully: it is the same duty cycle, and after all, no one puts a Lycoming in a boat even though they could afford to. No sensible propeller for 250 hp is going to want to turn 3100 rpm. The diameter of the prop sets its maximum RPM as the tips must be kept below Mach 1. Probably, you are going to want about a 2:1 reduction. With a Gilmer belt drive you need to be at exactly 2:1 or fairly far, say 1.6:1 or 2.4:1, or it will hunt and skip teeth. With gears you will want them ideally at prime number tooth counts, such as individual teeth see each other only rarely, and very definitely not 2:1. This is what caused the catastrophe known as the Continental Tiara. Driveshafts are very problematic in aircraft drive applications, plus which there are substantial negatives to pusher propellers. You do not want to design a engine package _and_ an airframe. There are more good airframes than engines, although admittedly many are better built by factories (one wood design hawked by an arrogant son of a bitch in Virginia who has never built an airplane himself comes first and foremost to mind.) Most homebuilts are just not designed for 600+ pound power packages. Most people want smaller airframes, I think, for lower materials cost and easier garage building, even if they are not afflicted with the common brain disease pervading experimental aviation, WSE. (Williamsport Spongiform Encephalitis-a disease where the brain has cooling fins eroded in its surface, causing the victim to think that 1939 lawn tractor technology is essential to flight.) |
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Chevy LS2 and Trans??? any real issues besides weight
MrV wrote:
Hey guys i'm a new pilot that really wants to build his own craft. help me with this one issue. I want to use a chevy ls2 or ls7 as the power plant in my craft. snip the aircraft i want to design is a very cab foward design with a pusher prop and the engine would be mounted approx mid craft. i'm new at this and besides having an engineering background i really have no exp building an aircraft so any opinions would be helpful LS1/2/6/ http://www.v8seabee.com http://www.seabee.info/seabee_engine_conversions.htm http://www.republicseabee.com/Corvette_Power.html They did all the legwork and I've seen publishied aritcles in the aircraft magazines in regards to the Corvette engine conversions... |
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Chevy LS2 and Trans??? any real issues besides weight
Thanx for the reply, i actually messed up in my previous post. the
intended numbers are 3200 to 3500 rpm and the propeller spinning approx 2500 to 2700 rpm. why isn't a car tranny good ? it seems to do just what i want for years in millions of cars reliably? Isn't the mated transmission made to convert the slightly oval engine rotation into the circular motion nec. for the prop? and also damp vib? now the belt drive u mention seems reasonable but i really really don't want my engine spinning faster than 3500 rpm: thanx again mrv |
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Chevy LS2 and Trans??? any real issues besides weight
"MrV" wrote in message
ups.com... Thanx for the reply, i actually messed up in my previous post. the intended numbers are 3200 to 3500 rpm and the propeller spinning approx 2500 to 2700 rpm. why isn't a car tranny good ? it seems to do just what i want for years in millions of cars reliably? Isn't the mated transmission made to convert the slightly oval engine rotation into the circular motion nec. for the prop? and also damp vib? now the belt drive u mention seems reasonable but i really really don't want my engine spinning faster than 3500 rpm: thanx again mrv The car transmission is not designed to run for hundreds of hours at high loads in a lower gear. Lower gears in a car only accumulate tens of hours over the life of the car. Plus you will be hauling a lot of excess iron /aluminum around - excess weight is just about the last thing one needs in an aircraft unless the intent is to minimize performance... Slightly oval motion ot circular motion??????? It's just gears. Damp vibrations? Not from a prop... -- Geoff the sea hawk at wow way d0t com remove spaces and make the obvious substitutions to reply by mail Spell checking is left as an excercise for the reader. |
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Chevy LS2 and Trans??? any real issues besides weight
truthfully the idea is to make an OKAY craft. i'm thinking 150 to
160kts with okay fuel burn. now if i'm right i'd be running the tranny in like 4th gear. isn't this where its designed to spend a good deal of its time ? if i remember right, a car engine's output is not perfectly circular its kinda eccentric. and something is neccessary to convert the irregular motion into the circular motion for the prop |
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Chevy LS2 and Trans??? any real issues besides weight
"MrV" wrote in message
oups.com... truthfully the idea is to make an OKAY craft. i'm thinking 150 to 160kts with okay fuel burn. now if i'm right i'd be running the tranny in like 4th gear. isn't this where its designed to spend a good deal of its time ? if i remember right, a car engine's output is not perfectly circular its kinda eccentric. and something is neccessary to convert the irregular motion into the circular motion for the prop If you are thinking of the top gear in a trans with overdrive, the overdrive isn't designed for high torques (read the owners manual - "do not tow trailers in overdrive"). Plus it will speed the prop, not slow it down. If you are thinking 4th out of 5 gears in the typical trans with overdrive, then you have direct drive - not much pont in bolting on a trans just to get out what you put in, eh? The auto trans has everything you don't want and nothing you do. No gears would be a better choice than the wrong gears. The torque output is not exactly constant, but the flywheel damps most of that out. A propeller, on the other hand generates torque pulses as it goes by cowling and stuff - that can cause problems if you are trying to run a drive shaft. Pusher aircraft are "worst case". Note that most piston engine aircraft have the prop bolted right on the end of the crankshaft - nothing required to account for the torque pulses from the engine (Ignoring the cases where you excite the resonant frequencies of the prop). -- Geoff the sea hawk at wow way d0t com remove spaces and make the obvious substitutions to reply by mail Spell checking is left as an excercise for the reader. |
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Chevy LS2 and Trans??? any real issues besides weight
actually i'm thinking 4th or 5th gear from a 6speed manual tranny.
from the LITTLE research i've done 3rd gear is like 1.43 and 4th is like 1.2 seems like a good range 3500rpm= 2400 prop rpm or at 1.2 3250 rpm = 2700 prop rpm. now wouldn't the prop vibs be less than the abuse the average tranny takes from a daily drive ? |
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Chevy LS2 and Trans??? any real issues besides weight
On Thu, 10 Nov 2005 15:01:46 -0600, Darrel Toepfer
wrote: MrV wrote: Hey guys i'm a new pilot that really wants to build his own craft. help me with this one issue. I want to use a chevy ls2 or ls7 as the power plant in my craft. snip the aircraft i want to design is a very cab foward design with a pusher prop and the engine would be mounted approx mid craft. i'm new at this and besides having an engineering background i really have no exp building an aircraft so any opinions would be helpful Car transissions aren't designed to take any thrust. I also suspect a phenominon called P factor would twist the end off the tranny the first time you started up the engine with a prop attached. |
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Chevy LS2 and Trans??? any real issues besides weight
Drew Dalgleish wrote:
Darrel Toepfer wrote: Car transissions aren't designed to take any thrust. I also suspect a phenominon called P factor would twist the end off the tranny the first time you started up the engine with a prop attached. If you're going to snip out what I typed, then please remove the quote reference to me as well... |
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