General Subaru 1 place questions??

SnoBird

Member
Joined
Mar 21, 2009
Messages
203
Location
Maryland
Hi everyone, great forum. Thanks for making it available to wannabe pilots like myself. I have a SnoBird single place that doesn't have an engine, and I'm trying to decide which powerplant is best for me. I think I have it narrowed down to three possible choices: Rotax 503 or the 582 (preferably 582), or maybe a Subaru of some sort. The Subarus I'm really not familiar with at all, other than the real basics. So here's a series of questions I was hoping the experts might be able to help me out with:

1. If I did use a Subaru engine, what type/configuration would be best to achieve the same net power to weight performance that would be achieved with a 582? (taking into account weight differences, and perhaps adjusting rotor diameter to achieve same disc loading etc). I'd also like a Subaru engine that's not underpowered or overworked. I don't really want an overpowered zoom-zoom gyro (especially being a beginner pilot), but I'm a big believer in using an engine with a decent power reserve so it will not be overworked (thereby contributing to reliability). I'd also like the extra power to help get me out of botched landing attempts etc, although I suppose this could be a double edged sword. But suffice to say I want an engine with reliable performance on par with the 582.

2. And I'd prefer a re-drive system, but I'm not familiar with the best system. Near CL thrust is very important to me, but every time I see a redrive system it usually seems to be a "hi-drive" system (with the prop shaft placed above the engine output shaft). Is it practical to invert these high drive systems and place the engine above the redrive, or does this usually not work out for whatever reason? And how reliable are the redrives? To coin a movie phrase "is it safe?"

3. Lastly, how much would a quality Subaru build be to put together?

Anyway, guess that's enough questions for now. Thanks in advance for any help/advice.
 
Last edited:
Hi everyone, great forum. Thanks for making it available to wannabe pilots like myself. I have a SnoBird single place that doesn't have an engine, and I'm trying to decide which powerplant is best for me. I think I have it narrowed down to three possible choices: Rotax 503 or the 582 (preferably 582), or maybe a Subaru of some sort. The Subarus I'm really not familiar with at all, other than the real basics. So here's a series of questions I was hoping the experts might be able to help me out with:

1. If I did use a Subaru engine, what type/configuration would be best to achieve the same net power to weight performance that would be achieved with a 582? (taking into account weight differences, and perhaps adjusting rotor diameter to achieve same disc loading etc). I'd also like a Subaru engine that's not underpowered or overworked. I don't really want an overpowered zoom-zoom gyro (especially being a beginner pilot), but I'm a big believer in using an engine with a decent power reserve so it will not be overworked (thereby contributing to reliability). I'd also like the extra power to help get me out of botched landing attempts etc, although I suppose this could be a double edged sword. But suffice to say I want an engine with reliable performance on par with the 582.

2. And I'd prefer a re-drive system, but I'm not familiar with the best system. Near CL thrust is very important to me, but every time I see a redrive system it usually seems to be a "hi-drive" system (with the prop shaft placed above the engine output shaft). Is it practical to invert these high drive systems and place the engine above the redrive, or does this usually not work out for whatever reason? And how reliable are the redrives? To coin a movie phrase "is it safe?"

3. Lastly, how much would a quality Subaru build be to put together?

Anyway, guess that's enough questions for now. Thanks in advance for any help/advice.

The SnoBird is an ultralight machine a Subaru engine would be to heavy, besides a proper converted Subaru engine would be more expensive that what you paid for the SnoBird.

raton
 
Thanks for the response Raton. But why would the Subaru be too heavy for a 1 place SnoBird as long as the rotor was enlarged sufficiently to get the proper disc loading? It doesn't have to be an ultralight, it can be configured as a non-ultralight easily enough. Plus, as far as I know, the two place SnoBird uses the same basic type of material and construction in its airframe as the one place does (someone please correct me if I'm wrong). And the two place SnoBirds frequently have auto conversions in them, like Chris Burgess' 2 place, for instance. So can you expound in more detail why a 1 place SnoBird is too fragile to handle a Sub?

Also, how much is a Sub conversion? The price of a new 582 is on the order of $6000. I'm assuming I could find a good low mile junkyard Sub motor for ~$2000 + the price of the redrive, maybe another $2000? Thanks for the response.
 
Thanks for the response Raton. But why would the Subaru be too heavy for a 1 place SnoBird as long as the rotor was enlarged sufficiently to get the proper disc loading? It doesn't have to be an ultralight, it can be configured as a non-ultralight easily enough. Plus, as far as I know, the two place SnoBird uses the same basic type of material and construction in its airframe as the one place does (someone please correct me if I'm wrong). And the two place SnoBirds frequently have auto conversions in them, like Chris Burgess' 2 place, for instance. So can you expound in more detail why a 1 place SnoBird is too fragile to handle a Sub?

Also, how much is a Sub conversion? The price of a new 582 is on the order of $6000. I'm assuming I could find a good low mile junkyard Sub motor for ~$2000 + the price of the redrive, maybe another $2000? Thanks for the response.

I believe the SnoBird is an ultralight please check it I could wrong but not sure it will take a Subaru but if that is the case, you can pick up a Subaru engine for less than US$2000 at a junkyard and for a conversion you be paying to much as you only need the crankcase and the cylinder heads, the rest is not used in a professional Subaru conversion. I know of some expert conversions are less than you be paying for a new Rotax 582, in our case it will twice as much you are paying for a new Rotax, and the only difference between them and us , we warranty (except overheating) the engines for 600hr. Hope this helps you.

raton
 
Bill, which Subaru engine are you using in your comparison?

It's rare to find the bigger EJ-series 2.2 and 2.5L engines used on single-place machines. If you're talking about the older EA82 series, you'll nearly double the weight of a 582 to get less than 50% more horsepower, and probably save little or no money.

Everything I've heard from guys who fly the Rotax two-stroke engines suggests that they actually run cleaner and happier at high throttle settings. A 503 would have the added advantage of a much simpler cooling system.

Despite the drawbacks of the two-strokes, Rotax still sells a bunch of them. The reason is they're hard to beat for power/weight/cost, and in recent years they've been relatively reliable.
 
Understand what you are doing

Understand what you are doing

Bill,

I am not an expert on this matter and not trying to act like one. However I do know enough to be able to tell you the kind of modification you are considering making, by using a Subaru engine, is a much bigger deal than most people think. This is a much heavier engine than the machine was designed for. That not only entails possibly changing some of the structure to be able to support the extra weight but will seriously affect the weight and balance of the machine, the center of gravity and the stability and flying characteristics of the machine.

Putting a bigger or heavier engine can be done to any Gyroplane as long as you understand what you are doing and make the appropriate design changes to keep the machine designed correctly. However, understanding all the ramifications a simple change can make to a Gyro is a lot more complicated than most people think and the lack of a full understanding has led to many people making less stable machines and many of those people paid for their mistakes with their lives.

Unless you are willing to take the time (and this may mean years) to study and learn enough about Gyroplane design to be able to safely design your own Gyro, then you would be wise to leave Gyro design to the experts. And changing the engine or the power significantly or anything that affects the way your machine will fly is in affect becoming a Gyroplane designer.

Being in the Experimental class gives us the freedom (from the FAA) to be able to make changes like that to our machines. It does not however free us from the consequences of making bad choices, even if we didn't have any idea that what we were doing would have any affect on the stability of our aircraft. I wouldn't make a design change to an aircraft without running it by the person who designed the machine in the first place. And if that is not possible I would seek the counsel and guidance of someone with as much design expertise and years of experience as I could find. Remember when you make a design change based on someones else s recommendation, you are betting your life on their knowledge and understanding of the subject. You don't want to take that lightly.

Learning what makes a Gyroplane safe and fun to fly is part of the journey. Take you time and do it right and you will enjoy the process as well as the end result. Gyroplanes can be one of the safest forms of recreational flying, but done without proper understanding or training they can be deceptively dangerous. Best of luck!!!
 
Thanks everyone for the helpful responses. I appreciate the time everyone has taken to help me out. And just so you guys know, my name is not "Bill". In order to sign up I had to put some kind of name in the field. I usually don't post my real name or personal information anywhere on the internet for privacy and security reasons. Not trying to hide anything, but just thought I'd clear that up since so many of you are referring to me as "Bill." :lol: You can just call me "SnoBird" for now if you don't mind.

Raton I take it from your posts that you're actually involved in the sale of Subaru conversions? I'm a little confused by your posts, but if I read you correctly you actually make or sell these things?

PW_Plack so you're saying using a Sub just ain't worth it when everything is factored in and wont even save much money? (If any) I'm not really familiar with all the various makes and models, so I guess I'll just take your word for it. But apparently the straight auto engine is not used, only components from a donor engine are then transplanted into a custom made crankcase etc?? Is that how these things are done? Any link, pics etc I can see to help flesh this out?

GyroDoug thanks for the warning and kind advice on not building a death trap. Believe me, the last thing I want to do is to build a rickety, unbalanced and unsafe death trap. To give you a quick background, I've been very interested in gyros since I was a child (in my 40's now). I used to spend hours upon hours reading Bensen brochures (in the pre internet days) after ordering them from the ubiquitous Bensen ads in the back of Popular Mechanics and Popular Science magazines. That love of gyros and other types of aircraft stuck with me as I got older. So much so, I ended up taking a degree in aerospace engineering when I went to college. Then later I finally decided to take my first flying lessons in a two place gyro. After accumulating about 11 hours of dual, I was at the point where I was ready to start groundwork with my own machine. But at the time I didn't have my own machine, so I put gyro flying on the back burner for several years afterward. Fast forward to today and now I'm buying a single place SnoBird kit. I've decided to start a leisurely process of finally putting together my own gyro once and for all. And the question of how to power this gyro is in the forefront, so that's why I'm exploring my options in regards to Rotax vs Subaru.

As for the stability issues, although I've been out of the gyro loop for many years, I'm aware of the basics concerning PPO, PIO, thrust lines and horizontal stabilizers. And although I've never hang tested a gyro, I'm familiar with some of the basics concerning weight distribution, disc loading etc. Although I certaintly don't know it all, and is why I plan on hanging out here more often to try and get up to speed on practical gyro design and construction while I plan the build of my own gyro (which I'm in no hurry with right now).

As to the structural issues pertaining to mounting a large, relatively heavy automotive engine on a lightweight aluminum gyro frame, that is a very important factor obviously. And I take it very seriously. It's also one subject that I'm not terribly informed on and have no practical experience with as pertaining to gyros. Which, again is why I'm asking for advice here from those who might've done this before.

Anyway, hopefully that offers a bit more of an introduction for myself. Based on what I'm hearing from you guys so far, it sounds like the Subaru engine is not the best choice for the single place. And if it's no cheaper than the 582, then that does move the decision more towards going with a 582. I like the lightness and simplicity of a quality 2-stroke. And I could use the existing motor mount system wth no modifications - which is a nice plus.

In the meantime does anyone have information on powerplants where a lot of detailed close up photographs show the mounting systems? Or just generally discuss the pros and cons of the various powerplant choices? Sometimes pictures truly are worth thousands of words.

Thanks for the help, looking forward to chatting with ya'll more in the future.
 
Replacing a Rotax two-stroke with a 200-pound (EA82) auto conversion which increases aircraft empty weight more than 30%, almost entirely behind the CG, is likely to require at minimum new cheekplates to reposition the rotorhead relative to the top of the mast, associated adjustments to control rids, trim spring(s) and prerotator assembly, relocation of the main gear axle rearward, and you'll probably need a heavier motor mount, as well. You'll be left with a keel with extra holes, not a good thing. It can be done, but how much redesign do you want to take on?

Your other question is a topic of some debate. Some people throw away much of the original Subaru engine and rebuild it with aftermarket racing parts. Others trust the factory's reliability record more than aftermarket rebuilders, and swear by pulling it straight out of a junk car and adding a redrive. There are plenty of examples of both success and failure spread among both camps. There are reports of infant mortality among the modded engines, and Australian cattle musterers who report thousands of hours of service from stock, used engines. ("Replace 'em when they start smokin'.")

If you favor using the engine with its original internals and as few changes as possible, you might save money over a Rotax, but EA82 donors are older cars now, and finding one that's not already beat may get tougher.

Adding 100 pounds to what's supposed to be a light, single-place gyro can also transform its handling from "motorcycle" to "minivan."

There may also be other considerations, depending on where you live. I bought a partial Sport Copter kit from an estate sale when I lived at 200' MSL, and it looks like the 582 that came with it won't cut it here in the high desert. Our summer density altitude at ground level is often in the 8,000' range, so I'm researching turbocharged four-stroke options.
 
Bill Snobird,
A double hang test was done on a single place snobird with a 503 down at Bensen Days last year. The trust line came out to be 5" high. I think a 582 would give you the best performance on it but you may want to make some changes to get the thrustline closer to the center.

This one was for sale a few months ago. Not sure if it still is.
 

Attachments

  • Snobird-1.jpg
    Snobird-1.jpg
    47.3 KB · Views: 0
Thanks again guys. I've seen quite a few single place VW direct drive conversions over the years. I've always heard they're usually a bit underpowered, but overall generally work ok. And recently I've seen a few direct drive Subaru single place machines on this forum as well. But I'm sensing the trend that most of you guys generally disapprove of auto engines in a single place for the reasons cited.

So back to a Rotax powered Sno-Bird - Tim thanks for the info on the SnoBird with an actual measured 5" high thrustline. That's good to know. Do you know if the 503 was equipped with a high drive or a low drive config? And was the thrustline measured with the actual pilot sitting in the seat and accounting for the weight of the blades and crossbar? And yes I've already looked over my kit and have a few probable changes planned for it. They are as follows:

1. Engine will be mounted so the redrive hangs below the crankshaft (i.e. lowdrive). Possibly will require modifying mount to elevate engine appropriately.

2. Raise the seat a coupla-five inches (TBD).

3. Probably change the front portion of the keel to elevate it a similar distance (2-5 in) to comprehensibly move the control stick linkage and pedals up with the seat. I'tll need a small extension on the nosewheel, but as far as I can see these mods should be pretty straightforward.

4. I've looked at the relatively small horizontal stab that comes with the kit. The stab is small, but on the plus side it is immersed in the propwash, so at least it's got that working for it. I might build a larger, more substantial HS (with a higher aspect ratio) and also probably support it with triangular metal bracing (tied into the keel). The way it is now seems a bit flimsy to me.

5. Possibly slightly tweaking the angle of the engine thrustline to further move it closer to the CG - although I'm hoping not to have to angle the thrustline by slightly tilting the engine one way or the other. Not sure about this one, TBD.

Anyway, I'm pretty sure these mods would bring the thrustline quite close to the CG. And even if it weren't exactly thrust-CG coincident, I feel fairly confident with proper instruction and not rushing my practice, I can learn how to fly the machine safely in regards to longitudinal stability. Basically I plan on training in the same type machine and closely adhering to the philosophies of super established, super knowledgeable gyro-gurus like Chris Burgess, Chuck Beatty, Igor Bensen, Ken Brock and others - many of which have successfully logged thousands of hours in non-HS/non-CG thrust machines long before any of this was widely recognized and accepted. I guess my point is that I'm ok with the thrust CG not being exactly lined up with the CG, as long as I dont skimp on the training and practice and dont try to bite off more than I can chew, especially during my early solo flying.

Thanks again to everyone for the great info.
 
Thanks again guys. I've seen quite a few single place VW direct drive conversions over the years. I've always heard they're usually a bit underpowered, but overall generally work ok. And recently I've seen a few direct drive Subaru single place machines on this forum as well. But I'm sensing the trend that most of you guys generally disapprove of auto engines in a single place for the reasons cited.

So back to a Rotax powered Sno-Bird - Tim thanks for the info on the SnoBird with an actual measured 5" high thrustline. That's good to know. Do you know if the 503 was equipped with a high drive or a low drive config? And was the thrustline measured with the actual pilot sitting in the seat and accounting for the weight of the blades and crossbar? And yes I've already looked over my kit and have a few probable changes planned for it. They are as follows:

1. Engine will be mounted so the redrive hangs below the crankshaft (i.e. lowdrive). Possibly will require modifying mount to elevate engine appropriately.

2. Raise the seat a coupla-five inches (TBD).

3. Probably change the front portion of the keel to elevate it a similar distance (2-5 in) to comprehensibly move the control stick linkage and pedals up with the seat. I'tll need a small extension on the nosewheel, but as far as I can see these mods should be pretty straightforward.

4. I've looked at the relatively small horizontal stab that comes with the kit. The stab is small, but on the plus side it is immersed in the propwash, so at least it's got that working for it. I might build a larger, more substantial HS (with a higher aspect ratio) and also probably support it with triangular metal bracing (tied into the keel). The way it is now seems a bit flimsy to me.

5. Possibly slightly tweaking the angle of the engine thrustline to further move it closer to the CG - although I'm hoping not to have to angle the thrustline by slightly tilting the engine one way or the other. Not sure about this one, TBD.

Anyway, I'm pretty sure these mods would bring the thrustline quite close to the CG. And even if it weren't exactly thrust-CG coincident, I feel fairly confident with proper instruction and not rushing my practice, I can learn how to fly the machine safely in regards to longitudinal stability. Basically I plan on training in the same type machine and closely adhering to the philosophies of super established, super knowledgeable gyro-gurus like Chris Burgess, Chuck Beatty, Igor Bensen, Ken Brock and others - many of which have successfully logged thousands of hours in non-HS/non-CG thrust machines long before any of this was widely recognized and accepted. I guess my point is that I'm ok with the thrust CG not being exactly lined up with the CG, as long as I dont skimp on the training and practice and dont try to bite off more than I can chew, especially during my early solo flying.

Thanks again to everyone for the great info.


I agree with PW_Plack there is no savings using a converted Subaru engine if anything it will be twice as much as a new Rotax 582

raton
 
I as well agree with what others have said here. I am in the process of replacing a EA81? Subaru off a guys gyro bee and replacing it with a 80hp FI Yamaha motor. He has been messing with that Subaru for 3 years and has yet to get it to fly and is wishing he could somehow get some of the $$$ back that he has dumped into it.

My personal opinion is go with the 582. That will be the simplest and they are pr oven to be good. Russ Hobbs here on the forum has a good used one for sale if you are interested. My friend Dick has his Subaru engine that is not working out for him for sale as well.
 
I as well agree with what others have said here. I am in the process of replacing a EA81? Subaru off a guys gyro bee and replacing it with a 80hp FI Yamaha motor. He has been messing with that Subaru for 3 years and has yet to get it to fly and is wishing he could somehow get some of the $$$ back that he has dumped into it.

My personal opinion is go with the 582. That will be the simplest and they are pr oven to be good. Russ Hobbs here on the forum has a good used one for sale if you are interested. My friend Dick has his Subaru engine that is not working out for him for sale as well.

He has been messing with that Subaru for 3 years and has yet to get it to fly and is wishing he could somehow get some of the $$$ back that he has dumped into it.

Maybe he is not getting the right advise..? Subaru would be the easier engine to convert for aircraft use…

raton
 
Raton...........ol maate

week or 2 back i asked if you were aligned with soob aero engine conversions / sales.
You replied...........NO

On another thread here [ now locked closed ] you now confirm you are involved in such an enterprise, even have a web site / catalogue etc etc

pal...........you've got me confused [ which ain't hard ]:confused::confused:

could you clear this up please.........cheers
 
The snobird double hang test at Bensen Days was done with the pilot in the seat with the blades on. He has a 503 with the gearbox mounted up.
 

Attachments

  • Snobird-2.jpg
    Snobird-2.jpg
    54.6 KB · Views: 0
2 vs 4

2 vs 4

Snowbird: reading your messages one can come to the conclusion you have a good knowledge about gyros and if weight/balance can be accommodated to your gyro then the only question you have should be the reliability and life span of a 2 stoke versus a 4 stroke engine.

raton
 
Here is some data I did with Tom Milton last year using aircraft scales.

Engine Subaru EA-81
Pilot 235 lbs
Fuel 2 gals

LEVEL SURFACE MEASUREMENTS
Wheelbase-------------------------69.5
Left main wheel weight------------345 lbs
Right main wheel weight-----------350 lbs
Nose wheel weight-----------------57 lbs
Main axle height above floor --------6 ½”

INCLINED SURFACE MEASUREMENTS
Angle, degrees, from step (5)-------4.2
Angle Measurement Accuracy------0.1
Nose wheel weight, step (4)--------34 lbs

CALCULATED RESULTS
AUW-----------------------------752 lbs
Horizontal CG-----------------------5.27” Distance in front of main wheel centerline.
Vertical CG------------------------35.45” Distance above floor, gyro at flying weight, not on scales.
Vertical CG Accuracy---------------0.69 Same units as Vertical CG.

Based on Angle measurement accuracy. Other inaccuracies may apply.
Prop is 44.5" above floor (9.05” above VCG)
 
Wow, 9" above the CG?? That's scary. That's a very substantial moment arm. Do you know offhand if that was an engine with a reduction drive? If so was it over or under? I'm assuming over with thrust/cg displacement that large.
 
Top