Knights of the Sky Foundation

[BMA_Hellbender]

11 minutes ago, Chill31 said:

Looks like Bender beat me to it!  This engine seems to be more sensitive to mixture settings, so I am still learning how to run it well.  Got it purring nicely in this video though!

 

 

Too late, I already farmed your likes!

 

Seriously awesome job. I’m speechless. When do you think you can fly her?

 

 

[Chill31]

 

1 minute ago, Hellbender said:

Too late, I already farmed your likes!

 

Seriously awesome job. I’m speechless. When do you think you can fly her?

 Maybe a week or two.  I need to have the propeller hub lock plate made and drill the hub bolts.  I also have to be able to run it perfectly on the ground.  In the air, it is too late to learn.

[Holtzauge]

@Chill31: What about the Levil BOM? IIRC then you wrote earlier on that you were considering getting one of those? Or have you got one already? Would be fantastic with some solid flight data!

 

For instance the Dr.1 speed issue: How fast does a Dr.1 really go on the deck? Have seen lots of different numbers for that so it will be really interesting if you get the BOM to finally get some solid numbers on that, especially seeing you have what I understand to be the "standard" 2.62 x 2.3 m prop most commonly used.

[JGr2/J5_Baeumer]

We are fortunate.  Thanks, Chill.

[Chill31]

5 hours ago, Holtzauge said:

@Chill31: What about the Levil BOM? IIRC then you wrote earlier on that you were considering getting one of those? Or have you got one already? Would be fantastic with some solid flight data!

 

For instance the Dr.1 speed issue: How fast does a Dr.1 really go on the deck? Have seen lots of different numbers for that so it will be really interesting if you get the BOM to finally get some solid numbers on that, especially seeing you have what I understand to be the "standard" 2.62 x 2.3 m prop most commonly used.

I do have the BOM, and I plan to fly with it on the first flight, just in case something unfortunate happens.  The prop is a copy of the only original Dr.I propeller in existence, kept in the Berlin museum, so it is the real deal.  Same as Mikael Carlson.  Cant wait to get some data!

[Holtzauge]

12 hours ago, Chill31 said:

I do have the BOM, and I plan to fly with it on the first flight, just in case something unfortunate happens.  The prop is a copy of the only original Dr.I propeller in existence, kept in the Berlin museum, so it is the real deal.  Same as Mikael Carlson.  Cant wait to get some data!

 

Sounds great and looking forward to seeing some BOM data! Congratulations on the Le Rhone acquisition and restoration! Looks and sounds awesome!

[Chill31]

Well, I can officially confirm maximum rpm for the 120 Hp Rhone/Oberursel UR2 is 1220 rpm static.  Getting close to a first flight.  This engine is a completely different animal from the 80 Rhone.  My grandmother could fly an 80 hp Le Rhone. The 120 hp...makes me nervous ?

 

I'll link a video soon

[AndyJWest]

Take care, Chill31. Keeping safe is more important than testing aircraft, even if it doesn't always seem that way...

[Holtzauge]

19 hours ago, Chill31 said:

Well, I can officially confirm maximum rpm for the 120 Hp Rhone/Oberursel UR2 is 1220 rpm static.  Getting close to a first flight.  This engine is a completely different animal from the 80 Rhone.  My grandmother could fly an 80 hp Le Rhone. The 120 hp...makes me nervous ?

 

I'll link a video soon

 

Wow, 1220 rpm static, that sounds very good indeed! Especially seeing you have the documented Dr.1 propeller with 2.62 diameter x 2.3 m pitch and since the Le Rhone is rated at around 1200 rpm AFAIK getting such high rpm on the chocks indicates you have a very well performing engine indeed!

 

AFAIK a rule of thumb is usually to target around 85% rated rpm static but I don’t know if the Germans in general followed that rule or not for the Dr.1. OTOH, I have seen rpm numbers for the Albatros D.V with the 160 hp Mercedes D.III which is rated at 1400 rpm having circa 1385 rpm in climb and 1530 rpm at top speed so in that case the rated rpm is reached only at speeds slightly faster than that for best climb rate.

 

Given that you get 1220 rpm already static it’s going to be interesting to see your top speed and climb rate: Based on the above I would not be surprised if you will go much faster and climb better than what some historical sources indicate but maybe you will have to throttle back to avoid overreving at top speed? Any ideas about where you will set your rpm limits for this engine? OTOH speed and max rate climbs maybe have to wait until engine is fully run in?

 

AFAIK, rotaries are very much individuals in terms of performance and power output and I’m guessing your Le Rhone has been lovingly renovated with exacting tolerances and is run with high quality castor oil and fuel which probably puts it in another class then compared to a hastily assembled war time manufactured Oberursel run on “Ersatz”-oil.

 

Anyway, good luck with the test flight and looking forward to hear how the Dr.1 behaved with what seems to be a very potent power-egg indeed!

Edited February 3, 2021 by Holtzauge

[Chill31]

54 minutes ago, Holtzauge said:

 

Wow, 1220 rpm static, that sounds very good indeed! Especially seeing you have the documented Dr.1 propeller with 2.62 diameter x 2.3 m pitch and since the Le Rhone is rated at 1200-1250 rpm getting such high rpm on the chocks indicates you have a very well performing engine indeed!

 

AFAIK a rule of thumb is usually to target around 85% rated rpm static but I don’t know if the Germans in general followed that rule or not for the Dr.1. OTOH, I have seen rpm numbers for the Albatros D.V with the 160 hp Mercedes D.III which is rated at 1400 rpm having circa 1385 rpm in climb and 1530 rpm at top speed so in that case the rated rpm is reached only at speeds slightly faster that for best climb rate.

 

Given that you get 1220 rpm already static it’s going to be interesting to see your top speed and climb rate: Based on the above I would not be surprised if you will go much faster and climb better than what some historical sources indicate but maybe you will have to throttle back to avoid overreving at top speed? Any ideas about where you will set your rpm limits for this engine? OTOH speed and max rate climbs maybe have to wait until engine is fully run in?

 

AFAIK, rotaries are very much individuals in terms of performance and power output and I’m guessing your Le Rhone has been lovingly renovated with exacting tolerances and is run with high quality castor oil and fuel which probably puts it in another class then compared to a hastily assembled war time manufactured Oberursel run on “Ersazt”-oil.

 

Anyway, good luck with the test flight and looking forward to hear how the Dr.1 behaved with what seems to be a very potent power-egg indeed!

Yes, I think you are right on all accounts.  This engine may very well be in better than average shape compared to a war time production engine.  That being said, it does have some light wear over the last 100 years that I could not eliminate in a reasonable budget.  I have had several people comment on how well it holds compression in the cylinders though...it is indeed very strong.  

 

I will do tests at several rpm settings and see what speed it gets.  If I get 115mph at 1250 rpm, we will be debunking some myths immediately! I'd be willing to let it rev up to 1350 or 1400 for a brief time though.  I am sure Mikael Carlson hits whatever the maximum is in his show, so I am confident in a well restored motor.

 

I need to go look at FC and see what max static RPM the Dr.I hits...

 

Exciting times!

 

 

Edited February 3, 2021 by Chill31

[BMA_Hellbender]

21 hours ago, Chill31 said:

Well, I can officially confirm maximum rpm for the 120 Hp Rhone/Oberursel UR2 is 1220 rpm static.  Getting close to a first flight.  This engine is a completely different animal from the 80 Rhone.  My grandmother could fly an 80 hp Le Rhone. The 120 hp...makes me nervous ?

 

I'll link a video soon

 

I find this stuff fascinating and I'm not ashamed to admit that I'm totally lost about trying to make sense of airframes, engines, horse power ratings, RPMs, and top speed.

 

For most if not all of these engines according to totally reliable information I dug up on Wikipedia, theaerodrome and elsewhere, it would appear that the cylinders would begin to stretch and depart around 1500 RPM, regardless of the engine and rated hp/RPM, due to the physical limits of a spinning engine block.

 

Other than that, I can't make much sense of what the engines were actually able to output at max RPM. For example:

 

• Sopwith Pup: Le Rhone 9C, 80hp, 1200 RPM, 112mph (180km/h)
   
• Nieuport 11: Le Rhone 9C, 80hp, 1200 RPM, 101mph (162km/h) @ 2000m (TAS?)
   
• Nieuport 17: Le Rhone 9J(a), 110hp, 1200 RPM, 110mph (177km/h)
   
• Nieuport 17bis: Clerget 9B, 130hp, 1250 RPM, 109mph (175km/h)
   
• Sopwith Camel: Clerget 9B, 130hp, 1250 RPM, 113mph (182km/h) or 118mph (190km/h) depending on who you ask
   
• Nieuport 24: Le Rhone 9J(b), 120/130hp, 1250 RPM, 109mph (176km/h)
   
• Hanriot HD.1: Le Rhone 9J(b), 120/130hp, 1250 RPM, 115mph (184km/h)
  
   
• Fokker Dr.I: Oberursel Ur.II, 110hp, 1200 RPM (???), 103mph (165km/h) @ 4000m (TAS?) and/or 110mph (180km/h) @ 2600m (TAS?)
   
• Fokker E.V/D.VIII: Oberursel Ur.II, 110hp, 1200 RPM (???), 127mph (204km/h)

 

The ones that immediately jump out are the Sopwiths. Did they run the engines beyond rated RPM and then measure the top speed at sea level? For the Le Rhone 9C this would have been 92hp at 1300 RPM, and for the Clerget 9B 150hp at 1400 RPM (this matches the FC Camel). The Hanriot also fits in that list, though it's quite close to the 113mph (182km/h) measurement of the Camel, and the Hanriot is a lighter, more streamlined machine with only one machinegun. It was meant to be at least an improvement over the Nieuport 23/24. In the same vein, the Nieuport 17bis equipped with a Clerget 9B would at least in theory have been faster than a Sopwith Camel, owing to its sesquiplane design, but sporting the same engine. The Fokker E.V/D.VIII monoplane is the most extreme example of that, where a similar engine would have led to a top speed in excess of 200km/h.

 

Or am I looking at this from the wrong angle and is there more to propellers and climb rates?

 

 

Quote

I will do tests at several rpm settings and see what speed it gets.  If I get 115mph at 1250 rpm, we will be debunking some myths immediately! I'd be willing to let it rev up to 1350 or 1400 for a brief time though.  I am sure Mikael Carlson hits whatever the maximum is in his show, so I am confident in a well restored motor.

 

 

Please be f****** careful.

 

Edited February 3, 2021 by =IRFC=Hellbender

[Chill31]

I am highly skeptical of WWI performance data that was collected during WWI.  I am with you. A Pup on 80 hp is faster than a N17 on 110+ hp? I find it very unlikely. 

 

Fortunately, I think I will get good data on both of those planes in the next few years.

 

One bit of modern day info I received was that TVALs UR2 Fokker D8 will fly circles around the 160 Gnome Camel.

 

I think some flight data from the Dr.I will be very revealing about the reliability of much of the data we have poured over as a WWI community. It will also give us a great benchmark for the aircraft in FC and ROF. 

[ZachariasX]

5 hours ago, Chill31 said:

I am highly skeptical of WWI performance data that was collected during WWI.  I am with you. A Pup on 80 hp is faster than a N17 on 110+ hp? I find it very unlikely. 

I'd definitely agree on that. There was definitely not really a standard to assess flight performance as we have it today.

 

I'm also very sceptical about actual power output from the respective engines as form my experience, similar type vintage engines can differ drastically in their actual volumetric efficiency and actual shaft power output. Engines that are in fine order and that you just keep running over decades may well lose a third of their horses. This is usually only apparent after rebuilding the engine.

 

I think it might be important to have an idea of the relative power output between your "80 hp" and "110 hp" engine. This could be done easily if you put the morse prop on your 110 hp engine and do a static run. This would come closest to putting your engine in a bench. As power output scales to the cube of vs rpm, you then know the relative power. If you claim 80 hp to be the nominal power for the small engine, then you have a supposed nominal power for the "110 hp" engine, something we can work with if for instance @Holtzauge were to simulate the performance your aircraft. Not having at least a plausible assessment of the actual power gap would certainly introduce a systemic error in any performance analysis.

 

But we can correct for both prop size and power to see what we should get as static performance. (If you would find an engine with a precisely known power output, you can put on your Morse prop on that one and get a base line for power vs rpm.)

 

Thus, I'd estimate your current 2.62 m prop to require ~15% more power to be canked at the same speed than the 2.5 m prop. (2.62/2.5)^3 = 1.15

Conversely, cranking 5% higher rpm would require ~35% more power.

This makes for a grand total of 50% power budget increase to match your data, hence if your smal lengines has 80 hp, then you probably have a 120 hp engine installed now. Given the differences in the original "110 hp" and "120 hp" engines and what you  did with yours, I would find any assumption of 110 hp output implausible.

 

Thus, the residual power budget after subtracting the energy spent in cranking the larger prop amounts to 5% rpm increase. If you had AFAIR 1150 rpm on your "small combo", putting on the "big combo" would give you 1210 rpm. You say you got 1220 rpm? I think we have something we can work with. Your engines must be pristine. And as said, my bets are that your 110 hp engine is in fact a 120 hp engine.

 

Man... If I ever end up with a broken combustion engine, I'll come asking you to rebuild it. You're my rotary whisperer for sure.

 

What I am surprised with is your speed expectations from your current setup.

 

In this sense, (as I understand you) what makes you assume you'll do 115 mph at 1250 rpm? If your propeller matches your stated specs, I'd give you 107 mph level speed, if your prop is very cambered then *maybe* 110. But 110 would really make it an outliner, I've never seen such hyper efficient aircraft and propellers. 115 mph I'd consider a speed where one should have again a closer look at your propeller.

 

On the previous page you stated:

 

I am really curious if the math lives up to reality. With full throttle on the 80, I was right around 100-103 mph and about 1350 rpm and about 1000 ft/min climb. 

 

Full throttle on the 120, I should be in the 110-115 range, and around 1400 ft/min climb.

 

This gives you about a 10% slip on the Morse-proped 80 hp LeRhone while doing 1000 ft/min climb. I think this is as expected as it is normal. 1350 rpm would also give you ~115 mph level speed. We would need climb rpm for your "big combo".

 

Now, putting on the larger prop with the *same* pitch in my understanding should not give you any higher max level speed at all, as you already have almost no slip, you'd need to precede your propeller considerably to go that fast at 1250 rpm. Sounds like a Warp drive to me. But I'd expect your climb to definitely increase as well as that that you probably should go faster doing the same climb angle. However, the math above is precise enough to tell us that your propeller is actually of the same pitch than the Morse propeller, else it would draw more power at given diameter to crank. This indicates to me that you cannot expect a higher level speed at given rpm from the 110 hp combo than you get from the 80 hp combo. And that you will go 107 mph at 1250 rpm in your current aircraft.

[J2_Trupobaw]

12 minutes ago, ZachariasX said:

In this sense, (as I understand you) what makes you assume you'll do 115 mph at 1250 rpm? If your propeller matches your stated specs, I'd give you 107 mph level speed, if your prop is very cambered then *maybe* 110. But 110 would really make it an outliner, I've never seen such hyper efficient aircraft and propellers. 115 mph I'd consider a speed where one should have again a closer look at your propeller.

 

Should we start a betting pool?

[ZachariasX]

3 minutes ago, J2_Trupobaw said:

Should we start a betting pool?

Is it legal?

 

Edit: I find it always more informative where people place their money than where they place their opinions.

Edited February 4, 2021 by ZachariasX

[J2_Trupobaw]

Dunno. Maybe if we bet for bragging rights.

[ZachariasX]

One thing they taught me at the university is to always know and anticipate the result of your experiment. Any data you come across wears a backpack of context. Knowing the result and why you get that result is what makes you understand. Only then you you understand the context. The data alone are treacherous. They do not tell you if you have failed the experiment nor if you set it up in a wrong way. You can perfectly well draw false conclusions from correct data.

 

Bragging on the other hand is an end in itself.

[Chill31]

4 hours ago, ZachariasX said:

I think it might be important to have an idea of the relative power output between your "80 hp" and "110 hp" engine. This could be done easily if you put the morse prop on your 110 hp engine and do a static run. This would come closest to putting your engine in a bench. As power output scales to the cube of vs rpm, you then know the relative power. If you claim 80 hp to be the nominal power for the small engine, then you have a supposed nominal power for the "110 hp" engine, something we can work with if for instance @Holtzauge were to simulate the performance your aircraft. Not having at least a plausible assessment of the actual power gap would certainly introduce a systemic error in any performance analysis.

Unfortunately, the 80 Le Rhone and the 110 Le Rhone have different bolt patterns on the hub, and the hubs are not interchangeable between engines.  It would be impossible to swap propellers between them.  Considering I am well into becoming a regular rebuilder of rotary engines, I will probably construct a test stand in order to verify power output of engines I rebuild.  It will be some time before I do that though.

 

4 hours ago, ZachariasX said:

Thus, I'd estimate your current 2.62 m prop to require ~15% more power to be canked at the same speed than the 2.5 m prop. (2.62/2.5)^3 = 1.15

Conversely, cranking 5% higher rpm would require ~35% more power.

This makes for a grand total of 50% power budget increase to match your data, hence if your smal lengines has 80 hp, then you probably have a 120 hp engine installed now. Given the differences in the original "110 hp" and "120 hp" engines and what you  did with yours, I would find any assumption of 110 hp output implausible.

 

Thus, the residual power budget after subtracting the energy spent in cranking the larger prop amounts to 5% rpm increase. If you had AFAIR 1150 rpm on your "small combo", putting on the "big combo" would give you 1210 rpm. You say you got 1220 rpm? I think we have something we can work with. Your engines must be pristine. And as said, my bets are that your 110 hp engine is in fact a 120 hp engine.

The only difference from your numbers posted there is that the 80 Rhone propeller was also 1200 rpm static.  I never measured the pitch of either propeller, so I i still need to verify the angle of the blade to be certain.  The prop for the 80 Rhone was a custom job, and I am not sure what the actual pitch was since it was a modified version of the Hardman Peck Thomas Morse propeller.  The only thing that is certain for me at this point: the propeller on the plane now is an actual Fokker Dr.I propeller.  It is exactly the same as Mikael Carlson's, and his is copied (by a machine) from the only known surviving Axial made Fokker Dr.I propeller in the Berlin museum.  He and I are the only ones in the world with such propellers flying on our aircraft.  All others are reproductions made to look like an Axial, their accuracy to the original airfoil, pitch, etc being an unknown.

 

4 hours ago, ZachariasX said:

 

Man... If I ever end up with a broken combustion engine, I'll come asking you to rebuild it. You're my rotary whisperer for sure.

Haha, I have been learning from a master rotary engine rebuilder (he did TVALs Oberursels).  The only feather I have in my cap at this point, and the prototypes are still being made by Classic Aero Machining (the builders of the new made 100 Gnome), is that I have designed a new pushrod pin to better actuate the exhaust vavles on the 110 Le Rhone.  People often complain about how poorly they run, and in my testing on my motor, the added weight provides a major improvement for running the engine.  (side note, Oberursels don't have this problem because their pushrods are heavier than Rhone pushrods).  Hopefully, everyone who owns or operates a 110 Rhone will benefit from these new pins and enjoy their motor more than they do now!

 

4 hours ago, ZachariasX said:

 

What I am surprised with is your speed expectations from your current setup.

 

In this sense, (as I understand you) what makes you assume you'll do 115 mph at 1250 rpm? If your propeller matches your stated specs, I'd give you 107 mph level speed, if your prop is very cambered then *maybe* 110. But 110 would really make it an outliner, I've never seen such hyper efficient aircraft and propellers. 115 mph I'd consider a speed where one should have again a closer look at your propeller.

 

On the previous page you stated:

 

I am really curious if the math lives up to reality. With full throttle on the 80, I was right around 100-103 mph and about 1350 rpm and about 1000 ft/min climb. 

 

Full throttle on the 120, I should be in the 110-115 range, and around 1400 ft/min climb.

 

This gives you about a 10% slip on the Morse-proped 80 hp LeRhone while doing 1000 ft/min climb. I think this is as expected as it is normal. 1350 rpm would also give you ~115 mph level speed. We would need climb rpm for your "big combo".

 

Now, putting on the larger prop with the *same* pitch in my understanding should not give you any higher max level speed at all, as you already have almost no slip, you'd need to precede your propeller considerably to go that fast at 1250 rpm. Sounds like a Warp drive to me. But I'd expect your climb to definitely increase as well as that that you probably should go faster doing the same climb angle. However, the math above is precise enough to tell us that your propeller is actually of the same pitch than the Morse propeller, else it would draw more power at given diameter to crank. This indicates to me that you cannot expect a higher level speed at given rpm from the 110 hp combo than you get from the 80 hp combo. And that you will go 107 mph at 1250 rpm in your current aircraft.

You are correct.  I looked at my prop pitch and speed calculator, and I don't expect to get anything more than about 110 mph out of it at 1350 rpm.  The climb rate should be quite nice though!  My 1250 rpm comment above was only to say that if I am hopping along at 115 mph and 1250 rpm, we would know instantly that something is wrong in the historical data and FC.

 

I am really excited to fly this thing! based on my work schedule and the remaining testing I need to do, I probably won't get to it before the end of the month though

[ZachariasX]

12 minutes ago, Chill31 said:

I am really excited to fly this thing!

I just can't wait seeing you taking the Dr.I up and put it though its paces! But you stay safe!

[=IRFC=Gascan]

I'd love to see that thing in action before I move out west. There's a model battleship event in Statesboro I'm trying to attend on the weekend of the 27/28. If I can get the time off for that, would you be willing to let me visit and take some pictures, Chill31?

[Chill31]

3 hours ago, gascan said:

I'd love to see that thing in action before I move out west. There's a model battleship event in Statesboro I'm trying to attend on the weekend of the 27/28. If I can get the time off for that, would you be willing to let me visit and take some pictures, Chill31?

Of course! I'll send you a PM with my phone number. Just give me a call and let me know a few days before hand when you want to come out.  

[=IRFC=Gascan]

Will do! Thanks!

[1PL-Husar-1Esk]

@Chill31 I have three question regarding Dreidecker and hypothetical damage, maybe you can help?
Does Dr.1 use push rods for control surfaces and if damaged can they jamm whole control surface in fixed position? 

If one of the control surface cable would broke, whole control surface like elevator would be jammed in fixed position ?

If one ailerons cable would broke both ailerons would be inoperable and jammed in fixed posstion?

[Chill31]

11 hours ago, 1PL-Husar-1Esk said:

@Chill31 I have three question regarding Dreidecker and hypothetical damage, maybe you can help?
Does Dr.1 use push rods for control surfaces and if damaged can they jamm whole control surface in fixed position? 

If one of the control surface cable would broke, whole control surface like elevator would be jammed in fixed position ?

If one ailerons cable would broke both ailerons would be inoperable and jammed in fixed posstion?

On the Dr.1, it would depend on what was shot.  The ailerons would have the potential to be jammed if the control itself was shot.  How it is design, I think it would be very unlikely.  One aileron could control cables could be shot away, and the opposite aileron would still work, because they have independent sets of cables.

 

The rudder could be disabled by shooting away a cable, or less likely, it could be jammed with a direct hit on its support tube.  If the rudder cable on a Dr.I is shot away, it would be a very dangerous situation, because the rudder does not center itself.  The plane would almost certainly be crashed upon landing, if not destroyed.

 

The elevator has dual control cables, so 2 cables could be shot away as long as they are not both on the top or bottom of the elevator.  Again, there is a low probability that the control would be shot and jammed.

 

There are a number of other late war aircraft that have redundant control cables such as the Bristol F2b and the SE5.  The F2b has redundant rudder and elevator cables, but I can't remember what the SE5 has.  

 

The level of redundancy built in to some WWI aircraft tells us that they did receive hits often enough for it to be worth the extra weight of adding the cables.  Some aircraft also had independent elevator halves.  If the cables were shot away or jammed on one side, the other side would still work.  I could get information on this to find out specific aircraft.

[1PL-Husar-1Esk]

Thanks a lot for feedback.

9 hours ago, Chill31 said:

I could get information on this to find out specific aircraft.

This would be great because is hard to find this kind of information, man which build planes for sure know the best how it was design.

9 hours ago, Chill31 said:

The ailerons would have the potential to be jammed if the control itself was shot. 

You mean control column? "I read some diaries when damage to control column did jamm control surface.

 

I'm very interested in Camel which had 4 ailerons, this design would be very hard to make roll axis total inoperable not mention be jammed in fixed position.

 

S!

[Chill31]

Finally. I have it running well.  I need to get my BOM hooked up.

[Chill31]

Finally. I have it running well.  I need to get my BOM hooked up. Interestingly, it will prop hang so steeply, and under control, the the engine will lose power due to the extreme uphill flow from the tank to the engine.  

 

The low pass in the video is fast, maybe 140-150 mph.  I dove in at idle, with 1200 rpm showing! Then held it to 1250.  

 

It is much more sensitive to mixture control than the 80. For example, when I loop it, I lose about 25-50 rpm from the increase in fuel pressure which causes it to get too rich. 

 

The gyroscopic forces are more pronounced too. The prop is bigger and more massive along with a more massive motor.  A loop needs all of the rudder I can give it.  

 

Turns are exceptionally tight. My cheeks sag through the whole 180 degrees. Energy retention is noticeably better. 

 

Now I need someone to dogfight...

Edited May 24, 2021 by Chill31

[Holtzauge]

2 hours ago, Chill31 said:

Finally. I have it running well.  I need to get my BOM hooked up. Interestingly, it will prop hang so steeply, and under control, the the engine will lose power due to the extreme uphill flow from the tank to the engine.  

 

The low pass in the video is fast, maybe 140-150 mph.  I dove in at idle, with 1200 rpm showing! Then held it to 1250.  

 

It is much more sensitive to mixture control than the 80. For example, when I loop it, I lose about 25-50 rpm from the increase in fuel pressure which causes it to get too rich. 

 

The gyroscopic forces are more pronounced too. The prop is bigger and more massive along with a more massive motor.  A loop needs all of the rudder I can give it.  

 

Turns are exceptionally tight. My cheeks sag through the whole 180 degrees. Energy retention is noticeably better. 

 

Now I need someone to dogfight...

 

Congratulations! Looks and sounds awesome. Can't wait for the Levil BOM results: Especially top speed and climb rate will be very interesting given you now have a historic engine and prop setup. Will also be interesting to hear what kind of revs you get under climb conditions with the new engine /prop combination. As far as I have understood it, all you need is a "hardpoint" with a suitable bracket to mount the BOM? Maybe you already have that in place somewhere out on the wing? And when can we expect the first results?!!!

[Chill31]

If you are close enough to come to this, please stop in!

 

https://www.facebook.com/104727730885334/posts/529976331693803/?sfnsn=mo

 

Edited May 25, 2021 by Chill31

[Chill31]

I have some preliminary numbers Temperature 20C, altimeter 29.98 inches

 

Ground speed at 2100 MSL, 1200 rpm, 4 leg pattern to compensate for wind: 100 mph.  Yes, there is throttle left, and I think it would hit something around 1300 rpm at full throttle in level flight.  Waiting on new pushrods before I rev it up higher than 1250.

 

Climb from 1,700 MSL to 2,700 MSL was one minute.  Slower than I expected, so I may need to adjust airspeed OR it could be inaccuracy from my altimeter installation.

 

I still need to get the Levil BOM mounted for some comparative (hopefully more reliable) results.

[ZachariasX]

8 hours ago, Chill31 said:

Ground speed at 2100 MSL, 1200 rpm, 4 leg pattern to compensate for wind: 100 mph.

Gives your propeller 2% slip. So you'll go 110 mph @1300 rpm.

 

Thank you for the tests. It's just wonderful having a Dr.I like yours flying!

Edited May 30, 2021 by ZachariasX

[Cynic_Al]

4 hours ago, ZachariasX said:

Gives your propeller 2% slip. So you'll go 110 mph @1300 rpm.

 

 

Have you accounted for the square-law increase in drag as speed increases?

[ZachariasX]

22 minutes ago, Cynic_Al said:

Have you accounted for the square-law increase in drag as speed increases?

In principle a good point, but drag drag increases to the cube vs airspeed. Albeit here it is not applicable anyway, as a fixed pitch propeller is not geared such that all shaft power can be transformed into forward thrust. It can only do so, until max engine revs are reached. All excess energy beyond that is lost level flight. @Chill31 is describing this fact by limiting revs by keeping the throttle back.

 

The problem is now that a fixed pitch propeller has a very narrow band in which it operates efficiently. By keeping the pitch such that the plane doesn't reach it's equilibrium drag vs airspped (this is where your point would be of importance), you don't make your aircraft trade airspeed for altitude even with the faintest climb. Keeping the pitch such that the max. airspeed is below the aerodynamically possible maximum, you retain excess energy that is available for climb or turn. This way, the aircraft doesn't immediately enter a configuration where it converts shaft power to thrust in a less efficient way.

 

The early Spitfires and Hurricanes had fixed pitch propellers that aimed for maximum airspeed. It made the for terrible, on average low performing aircraft, as for the most part, the pilot had the wrong propeller at his disposal. The performance gain with constant speed propellers is drastic in every metric. It is like comparing a fixie bike with a racing bicycle. the fixie is not just worse, it so much worse, it makes it almost a different sport.

 

Regarding the slip, the Dr.I behaves very much like a Cessna. Just for the ones that read the manual.

[Monostripezebra]

Happy landings, that sounds really great!

[Holtzauge]

Post 1:

 

14 hours ago, Chill31 said:

I have some preliminary numbers Temperature 20C, altimeter 29.98 inches

 

Ground speed at 2100 MSL, 1200 rpm, 4 leg pattern to compensate for wind: 100 mph.  Yes, there is throttle left, and I think it would hit something around 1300 rpm at full throttle in level flight.  Waiting on new pushrods before I rev it up higher than 1250.

 

Climb from 1,700 MSL to 2,700 MSL was one minute.  Slower than I expected, so I may need to adjust airspeed OR it could be inaccuracy from my altimeter installation.

 

I still need to get the Levil BOM mounted for some comparative (hopefully more reliable) results.

 

Your BOM results will of course be good for new revised tuning but with current tuning based on historical sources my results for the Fokker Dr.1 C++ simulation model (at 15 deg C not 20 though) at full throttle are 177 Km/h TAS at 2100 ft MSL (just like @ZachariasX predicted!) and a climb time of 49 s between 1700-2700 ft MSL assuming T/O weight 1267 lb.

 

Post 2:

 

1 hour ago, ZachariasX said:

<Snip>: as a fixed pitch propeller is not geared such that all shaft power can be transformed into forward thrust. It can only do so, until max engine revs are reached. All excess energy beyond that is lost level flight. @Chill31 is describing this fact by limiting revs by keeping the throttle back.

 

In some sense I can't say I'm surprised that Chill needs to reduce throttle somewhat: The prop he has on is tailored for a WW1 Oberursel maybe hastily put together with wartime tolerances running on Ersatz oil which I would expect not to be on the same level performance wise as a lovingly restored Le Rhone run on prime castor oil. So it could well be so that the Le Rhone he has on now is capable of churning out more power than the Oberursel. This is actually a bit in line with what Javier Arango was saying in a part of the essay I have not posted: These rotary engines are very much individuals and each one has its quirks and they don't all perform the same. Pure speculation of course but I would not be surprised if Chill's Le Rhone is head and shoulders above a WW1 era Oberursel running on Ersatz for which the prop he has on now was probably intended.......

 

PS: Yet another two posts that in this forums infinite wisdom were automerged..........

 

Edited May 30, 2021 by Holtzauge

[ZachariasX]

42 minutes ago, Holtzauge said:

These rotary engines are very much individuals and each one has its quirks and they don't all perform the same. Pure speculation of course but I would not be surprised if Chill's Le Rhone is head and shoulders above a WW1 era Oberursel running on Ersatz for which the prop he has on now was probably intended.......

He is certainly my rotary whisperer. But I think that type certification and ratings were done on pristine engines that absolutely were to the manufacturers specifications. Hence, I'd think and ideal Fokker back then would behave about the same as his. I would assume that war worn examples back then managed a tad less rpm and performed accordingly. As his 80 hp and his 120 hp perform remarkably to theoretical predictions when comparing static runs, I think that he has truly engines that are both to whatever specs implied back then.

 

In my experience with old (car) engines is that manufacturing tolerances reflect the poor lubrication and do not really benefit from the good stuff we have today in terms of volumertic efficiency. You can't use high performing lubrication of today in old engines, they'd leak right out of the engine for no benefit. In old car engines, if you'd use 5W-40 oil insead of 20W-50 (that you'd use for an original 60's engine), then the engine runs well, but expect to lose a quart for every 100 miles of driving!

 

But with todays gasoline, they do run much, much cleaner and thus are far easier to operate. If you have a terrible burn best case (compared to what engines can do today), that shows then really the diference between V-Power and the cheap stuff at ARCO's: although both fuels give you about the same power, not stalling on a red and changing sparks much less, that has a lot of charm in it's own way.

[Holtzauge]

1 hour ago, ZachariasX said:

He is certainly my rotary whisperer. But I think that type certification and ratings were done on pristine engines that absolutely were to the manufacturers specifications. Hence, I'd think and ideal Fokker back then would behave about the same as his. I would assume that war worn examples back then managed a tad less rpm and performed accordingly. As his 80 hp and his 120 hp perform remarkably to theoretical predictions when comparing static runs, I think that he has truly engines that are both to whatever specs implied back then.

 

In my experience with old (car) engines is that manufacturing tolerances reflect the poor lubrication and do not really benefit from the good stuff we have today in terms of volumertic efficiency. You can't use high performing lubrication of today in old engines, they'd leak right out of the engine for no benefit. In old car engines, if you'd use 5W-40 oil insead of 20W-50 (that you'd use for an original 60's engine), then the engine runs well, but expect to lose a quart for every 100 miles of driving!

 

But with todays gasoline, they do run much, much cleaner and thus are far easier to operate. If you have a terrible burn best case (compared to what engines can do today), that shows then really the diference between V-Power and the cheap stuff at ARCO's: although both fuels give you about the same power, not stalling on a red and changing sparks much less, that has a lot of charm in it's own way.

 

When Chill did static tests with the propeller he has on now he got 1220 rpm for an engine rated at 1200 rpm as I recall it. Now modern convention is to target ballpark about 85% of rated rpm static, meaning around 1020 not 1220 rpm. Most tests of aircraft I've seen from the WW1 period reach rated rpm's somewhere in between climb and high speed conditions, e.g. Albatros rpm's are usually under 1400 rpm in climb and over 1400 rpm at top  speed. A high speed optimized prop would consequently not rev too much above rated rpm at high speed but pay for this through poorer climb since the rpm at climb will be lower yielding a lower climb rate. Conversely, a climb optimized prop would be closer to rated rpm in climb yielding good climb rate but pay for this by revving higher at top speeds thus forcing the pilot to take his chances and overrev the engine or reduce throttle.

 

Now if Chill gets over rated rpm already static I think this indicates either that the Germans who put a 2.62 X 2.3 m propeller on the Dr.1's at the time did not know what they were doing since they put on a propeller lacking the solidity to absorb the power that the engine produced or, which seems more likely, that Chill's engine is producing more power and torque than the average WW1 Oberursel did.

[Cynic_Al]

5 hours ago, ZachariasX said:

In principle a good point, but drag drag increases to the cube vs airspeed.

 

Could you link to a formula in which any form of aerodynamic drag does that?

 

Another factor to be considered is the relatively high increase in generated precession with a rotary engine, which has to be countered by the flying controls, thereby generating further drag.

[ZachariasX]

2 hours ago, Holtzauge said:

which seems more likely, that Chill's engine is producing more power and torque than the average WW1 Oberursel did.

I very much think that at the time the combo of the prop Chill (and Mikael Carlson) use, the Oberursel on average did not have the power it reached in later series, hence the uprating later on. I think that prop as born on the 110 hp Oberursel. From what I have read, I think Chill has a 120 hp engine. And it should be, as it is a copy of a 120 hp engine. And Chill certainly made it a better copy than it ever was. If I am not mistaken, the Oberursels were rated higher later on. Or did I get the sources wrong there?

 

I do also think that in the field and over constant use back then, compression was an issue, hence they were reluctant to formally issue a more suitable propeller, as it is for instance mounted on the Camel. Also, this was the time the Dr.I had a habit of losing wings. I doubt that optimizing the propeller for a specialist, small series aircraft was a great priority for Antony. At the time they really should have put that prop on by default because the engines really had 120 hp, then default was the Fokker D.VII.

 

If you get compression like Chill has from his engine, that is a great sign for having a powerful engine.

 

 

bloody merge…

4 minutes ago, Cynic_Al said:

Could you link to a formula in which any form of aerodynamic drag does that?

 

5 hours ago, ZachariasX said:

drag drag increases to the cube vs airspeed.

 

Edited May 30, 2021 by ZachariasX

[Chill31]

Without boring you with technical details of how the engine runs, I made a small modification which puts a little more strain on the pushrods.  Once I have the stronger pushrods, I will allow it to rev to 1350 rpm. 

 

The original engine was tested to at least 1300 rpm, so I think it is safe there and a little beyond.