Chill31

It has been many years in the making, but I am about to have some wonderful data for WWI historians. My Fokker Dr.I will fly with 3 engines: 80 hp Le Rhone, 120 hp Le Rhone, 130 hp Clerget. The biggest modification to my plane is taking place now, subsequent engine swaps will take only an afternoon I should have both the 120 Rhone and 130 Clerget running by year's end.

The Strutter is a great idea. That is very tempting. I need to see how big one is to know if I have enough space for it. I intend to do that. Right now, it looks like I will get to fly the Dr.I with the 80 Rhone, 120 Rhone, and 130 Clerget. I'm really interested to see the difference.

That one isn't mine, but I do fly there a lot. Did you take that?? You should stop in sometime. 8ga9

The Clerget deal is complete! It does leave me in a place where I must decide which direction to go with my next airplane project. Should I pursue the Nieuport 17 or change direction and build a Sopwith Camel? I could do the N17 with the 110 Le Rhone and the Fokker Dr.I with Clerget power like Josef Jacobs. Or I could do the Fokker Dr.I with the 110 Le Rhone and the Camel with the 130 Clerget? I'd love to know what other WWI enthusiasts around the world would be interested in seeing take flight. Please let me know your thoughts!

The intake valve on a Le Rhone is pulled open by the pushrod. Only the exhaust valve is pushed open. At high RPM that could be a possibility it would cause damage to the push rod. I guess the bottom line is failure would probably result in power loss or rough running vs instant seizure.

I did some research on those failure of rotary engines. Steel should be able to hold the cylinder on to more than 1700 rpm, though I didn't account for the heating from a running engine. So not likely that the cylinder will fly off. More likely is this....after discussing with an old time rotary guy...the steel will stretch and deform prior to failure which will result in the cylinder being longer than it should be. The valve pushrod will not change length due to it's fliexible attachment. The over all effect is that over revving would likely result in significant power loss due miss timed intake and exhaust valves. Would it cause complete failure? I don't know, but it is certainly possible.

Getting the Dr.I to be Le Rhone powered is my highest priority. I have spent some attention toward acquiring a 130 hp Clerget though, and it looks like we've made a deal. Pictures once everything is finalized.

I don't know from personal experience, but it seems quite a lot gets on the landing gear, belly, and wings. Watch here starting at 7:20

The TVAL Oberursel/Rhone numbers... 594ft/lb and 144HP @1280 rpm from our 110 Le Rhone

haha, I've yet to produce anything of value! But yes, I do! Mostly for the undesirable even of an in-flight fire...My chute is a modern seat pack emergency parachute that weighs about 15 lbs. I'm not sure where one would place 60 lbs of parachute in the cockpit...sitting on my chute leaves me sitting about 2 inches too high in the seat, which isn't a big deal, but it does leave me hanging out in the wind a lot more as well as requires me to lean down to aim down the gun sights. I bought the book on amazon. It is in German though. I don't know any technical German, and my conversational German is rusty. Google translate to the rescue??

Do you have a copy of the original manual? I sure could use one. I have a maintenance manual for it, but it does not have the rpm limits in it. I don't know personally (and I don't think TVAL does either) what rpm causes them to fly apart. I have seen pictures of aircraft in WWI where the rotary engine threw a cylinder through the cowling. I am attaching a couple of documents that show relevant info of the URII vs the 9J. There is only a marginal gain in HP with increased risk of engine damage/destruction. I am sure a large part of the reluctance to run the engine very hard is that these things are irreplaceable. I never in my wildest dreams thought I would be able to have one in my hands, but a stroke of luck has allowed it. They are extremely rare, and I doubt if you could buy one from anyone who has one. Though I've heard TVAL will make a new URII for 185k...don't know that for sure though, since I haven't asked. Quite a bit out of my price range. All of that to say, it is better to run it within the recommended rpm range than to push it hard. Without any other evidence to support a higher rpm, I intend to use 1300 as a maximum on my 9J.

Without question, the Dr. I is a 175 kmh airplane. I currently have a 320 cubic inch 160 hp engine in it turning a 76 inch propeller and it gets 172kmh at 2700 rpm. I am going to put the Rhône 9Jb (essentially the Oberursel UR II) which is 920 cubic inches turning a 102 inch propeller at 1200 rpm. The old engine is putting a lot of energy into the air, so I don’t anticipate it going any slower than it does right now. The Oberursel is more closely a copy of the Rhône 9Jb which has aluminum pistons instead of steel and yield an additional 10 hp. In fact the Germans called it the 120 Rhône. The Germans went to great effort to improve the engine by making it lighter. I don’t know how much lighter though. I am friends with the rotary engine expert who put TVALs engines together, and I’ve seen the pictures of those details on the Oberursel. The practical rpm limit on the rotary engines comes from the centrifugal forces pulling them apart at high rpm, hence the reason the rpm limits are very similar. My understanding is that TVAL doesn’t run their 80 Rhône’s over 1250 rpm out of that fear they will fly apart, though I don’t think they have had one fly apart.

I posted some updates on the website to include more pictures of the Rhône 9Jb. This engine has the appearance of being “like new.” There is still a bit of cleaning and measuring to do before we know for sure. Here is a link to the calendar if you wish to join in and get your hands dirty with WWI grease, and here is a link to pictures of the Rhône overhaul. Workdays are scheduled for Mar 2nd and 23rd. I do know a couple aerodromes planes owners. They seem to enjoy their plane well and get to experience many of the same quirks found in more authentic replicas. However, those kits are not quite authentic enough for me to pursue them as a true WWI flight experience. The steel tube fuselage offers some important safety advantages over wood, in ne being the fact it doesn’t splinter in a crash. I think it is wise to build a WWI replica with that in the back of your mind. However, I am not willing to sacrifice authentic weights and balances, so there is a middle ground I am trying to find. Perhaps a steel tube cockpit with wood everywhere else. Or perhaps just accept that a crash is going to beat you up pretty well...

Gasoline is extremely flammable. I had a friend who caught fire in the sky from a broken fuel line near the engine while flying a WWI era aircraft...he did not survive. One major difference between the Camel tank and the Dr1 tank is that the Camel tank is pressurized. A puncture will result in fuel spraying out of the tank vs the Dr1 where suction from the engine would result in a slower leak.

Slowly, I am getting to know more and more people who are flying WWI replicas throughout the world. It is wonderful to hear their perspectives on flying various aircraft, so I thought I would share with you some of the things I've learned. I've shared some stuff in other threads, and if I can remember it all, I will consolidate it here. If you have info, please share it here as well! On flying the Pup compared to the Fokker Dr.I "The pup is more harmonized than the Dr.1 and doesn’t suffer quite as much adverse yaw." Nieuport 11 "N.XI has very heavy controls compared to the Triplanes. When you do a wing over, it requires a large forward stick force to get the nose down again. The ailerons are very heavy, it’s actually hard to get full deflection when you're flying with one hand on the stick." On flying the Pup "I find the biggest thing with them is that there is a bit of forward stick force required for straight and level, the engineer is going to add some springs onto the control column so it’s not so heavy, but the controls are far far more harmonized than that of the Nieuport XI....really isn’t that pleasant" "Same with the pups, even though they are all built exactly to the drawings. They have slight variation [between each plane] and engines too, we have 4 80hp LeRhones that we operate and they are all slightly different." I find this to be the most illuminating comment since we struggle often to find "accurate" data for WWI aircraft. "I haven’t tried the max S/L speed yet but it does about 85mph at 1050rpm. When we were flying with the camel we were going 1200rpm and about 110mph down hill, and the camel (160 Gnome powered) was pulling away.. On flying the BE2 "The BE2’s are stunningly brilliant on a lovely evening they are like giant kites, the controls are quite heavy but effective. Like moving a barge around the air. I've flown the Early BE2c with the 70hp Reault engine and that’s probably the sweetest and it’s the lightest all round. The late C, E and original F are also lovely but slightly heavier on the controls." On WWI engines "The differences in all the 80hp LeRhones is amazing too. We operate 4 at the moment and they are all a bit different run." "Talking hours, the Nieuport has the sweetest running 80hp Le Rhone we have and it’s got over 125hrs on it!!! They pull the nose off it every 25hrs to inspect it, but it really is a lovely engine." "Our triplanes have radial engines but bigger propellers than what you have with the Lycoming. In terms of performance, we have flown our triplanes with a Lycoming once, and it was certainly noticeable the difference in climb performance. The Warner powered aircraft produces more thrust." "The 80hp Le Rhone is probably one of the easiest of the rotaries to operate IF they are set up well. It takes a bit of time operating the engine on the ground to learn what the engine is supposed to sound like and what it sounds like when it’s getting too rich or too lean and what to do about it (that’s the critical part). Almost every time you operate a rotary the Air/Fuel leavers will be at a different ratio, eg when I was flying the pup in the morning, the fuel leaver was leading the air by about 2/3 inch, but in the afternoon the leavers ere next to each other. The 80hp LeRhone is quite a forgiving engine it’s it generally has a wide operating range unlike other rotaries." "That was the first flight I have ever struggled to keep a rotary running well. I could not get it to run well at 1050-1100 rpm, but when I took it up to 1200 rpm it would eventually sort itself out. I suspected it was carb ice, and when we returned from the flight, I opened the hatch on the side of the cowl and put my hand on the intake tubes. They were ice.. so that would explain it." "With the 80hp LeRhone, when they are rich, they are a bit more labored and flat sounding. When lean, they are very sharp sounding and can backfire. But then when you are on the ground and at a low idle, they can get small exhaust pops when they are too rich."