engine requirements?

[Harvey L. Sorensen]

Originally Posted by RVbySDI

Well, here is an area that takes some knowledgeable analysis. When comparing the output of an electric motor with the output of an Internal Combustion engine the electric motor will put out much more power/HP than will an IC engine.

Primarily because of the greater efficiencies of the electric motor it does not need to have the same HP rating as an internal combustion engine in order to produce the same output of power. I am sure there are mathematicians or engineers out there that can chime in with the specific HP numbers needed for an electric motor if it is to replace say a 100 HP IC engine. Generally speaking an IC engine rated for 100 HP can be replaced with an electric motor that may be rated for say 25 HP (someone please correct me if this number is way off).

When comparing weights of comparable IC engines and electric motors one must make sure the comparison is for engines with equal outputs. Your 50 and 100 HP electric motors would better be compared to 400-600 ci IC engines (180-300 HP) rather than the 235-360 ci IC engines (115-180) typically used in RV's. Because of this the weight savings will be due to the fact you will be using a smaller electric motor to produce the same level of power output as you would with an IC engine. Not to mention the reduction in weight for all of the other peripheral components needed for the operation of an IC engine (i.e. starter, oil cooler, radiator, carburetor, exhaust, fuel pump, fuel lines, fuel filters, magnetos, etc.)

Steve in just about all cases you are correct. However in this case maybe not. The one diesel engine we replaced with electric was a 90 hp and the other one was a 125 hp. Both of these diesels were replaced with 100 hp electric. Both these diesel engines were about 350 ci and were industural rated, this being the difference. If you would stick these engines in a car they would call them 350 - 400hp. They developed their hp at about 2100 rpm.

[Ola]

Here's an engine specced for the right use, mounted in the Tesla Roadster.

http://youtube.com/watch?v=cE2Yd-pTS-s

~250 hp, 70 pounds.

Have to mention the battery weight of course, that's 900 pounds.

[Jerry Cochran]

You should really read the previous discussions on this...it has all been hashed out before.

1. All engines are air cooled in the end...with a rad it is just that an intermediary transfer is used...coolant...which means two additional heat transfers 1. engine to water, and 2. water to rad, before the air can cool the rad. Each transfer is less than 100% efficient which means that by the time it gets to the rad you have some additional cooling needs. When the air interacts with the rad, it is at a much lower delta T, which means a greater volume of air is required to achieve the same cooling in terms of heat energy removed.

2. Weight has been hashed again and again, the "heavy" cranks and such in an aircraft engine do not result in heavier packages...as noted many times the car engine will result in a hundred pounds or more installed weight. This is being generous.

3. There is no documented fuel burn/ performance advantage, and in the RV class of aircraft, just the opposite.

However, you can expect smoother operation, and easier starting.

Back to the original question, to me it is all about speed/fuel burn, and the most simple installation possible. Simple, not because I am afraid of instalation and the work, but rather because the simple solution ought always be preferred over the complex, from a reliability standpoint.

[/quote]
I am paraphrasing, but some smart person said "If you want to experiment, get a Subie, Chev, etc... but if you want to fly, go Lyco."

Here's a post just today on VAF Classified that begs the question "Why would a guy with $40K invested be selling same for half price?" Too much power? err... throttle it back..

Jerry

jim skala Join Date: Jun 2007
Location: Hartselle, Alabama
Posts: 3

Subaru STi FF package & MT prop give-away

--------------------------------------------------------------------------------

<<<My new Lyc 320 engine is due to be shipped the week of Oct. 21, so I relisted my Eggenfellner STi (4-cyl, over 200 HP) on eBay for $20,000, including MTV-7 CS prop. $20K is less than half of what I have invested in it to date. It is way too much engine for a 9, but should do fine for a 7A. At this point, I simply need to get it out of the shop to make room for the Aero Sport Power 320 Lyc engine.>>

[Andy_RR]

I always think it's hilarious that the Rotary fan-boys always think the slider-crank mechanism of a piston engine is a problem in need of a solution.

Of all the parts in a piston engine, the crank, rods and pistons are probably the most reliable and low-wear-rate components in an engine. It is so well understood, can deliver a good approximation to the ideal combustion chamber shape and is so easily manufactured that it simply doesn't require any futher inventive attention.

The wankel engine, on the other hand, has had more than half a century of development and it's still struggling to make it as a serious engine concept.

A

[rv6ejguy]

Originally Posted by Andy_RR

I always think it's hilarious that the Rotary fan-boys always think the slider-crank mechanism of a piston engine is a problem in need of a solution.

Of all the parts in a piston engine, the crank, rods and pistons are probably the most reliable and low-wear-rate components in an engine. It is so well understood, can deliver a good approximation to the ideal combustion chamber shape and is so easily manufactured that it simply doesn't require any futher inventive attention.

The wankel engine, on the other hand, has had more than half a century of development and it's still struggling to make it as a serious engine concept.

A

I totally agree. Wankel advocates are always talking about piston and rod failures on piston engines and how high Wankels can rev. Not sure where these ideas come from. F1 engines rev to 19,000 rpm and your modern production piston engine never has failures like this if kept within factory rev limits. They also don't use any oil between changes, get excellent mileage and outlast the chassis in most cases. Hard to beat a century+ of evolution.

I believe you should fly what you like and I like to see anything different flying, including Wankels. Let's just stick to the facts on advantages/ disadvantages of engine types.

[RVbySDI]

Originally Posted by Harvey L. Sorensen

Steve in just about all cases you are correct. However in this case maybe not. The one diesel engine we replaced with electric was a 90 hp and the other one was a 125 hp. Both of these diesels were replaced with 100 hp electric. Both these diesel engines were about 350 ci and were industural rated, this being the difference. If you would stick these engines in a car they would call them 350 - 400hp. They developed their hp at about 2100 rpm.

Well this kind of proves the point I was attempting to make. You are replacing Diesel engines with a real world HP output in the 350-400 HP range with an electric motor that has a real world HP rating of 100 HP. Comparing HP ratings on A/C electric motors with HP ratings on an internal combustion engine (be it gasoline or diesel) is not a straight across the board comparison. There are many additional factors that have to be evaluated before one can directly address what size electric motor can replace what size IC engine.

[Garth]

Got a link to that Dan Horton site on the redrive issues? I just get TV and movie stuff.

[rv6ejguy]

Most of the discussion was on this thread: http://www.vansairforce.com/communit...ght=belted+air

[gtmule]

Originally Posted by RVbySDI

Well this kind of proves the point I was attempting to make. You are replacing Diesel engines with a real world HP output in the 350-400 HP range with an electric motor that has a real world HP rating of 100 HP. Comparing HP ratings on A/C electric motors with HP ratings on an internal combustion engine (be it gasoline or diesel) is not a straight across the board comparison. There are many additional factors that have to be evaluated before one can directly address what size electric motor can replace what size IC engine.

I'm not sure I follow. If I need to run a pump at a certain flow rate and pressure rise I need to supply the pump with a certain amount of torque at a given rpm. Doesn't matter if the thing turning the pump is powered by diesel fuel or electrons. I guess it's possible that people are operating disels WAY out of their optimum range, and therefore having to use bigger engines (also out of their ideal powerband...).

[airguy]

And also running them at way less than full rated power, in the interest of long life. An electric motor rated for 5 hp (or 50, or 150) will deliver that power or a large percentage of it for it's entire life - because it's designed to. MOST (not all) IC engines are rated for maximum possible output - but not designed to keep it up. A 150 hp automotive engine will NOT last very long running at full power, but will last basically forever running at 30% load. Aircraft engines are the exception to this rule - they are designed to operate at a large percentage of maximum power for their entire life.