Engines > Your Own Design
The Le Rhone 9C
Jo:
--- Quote from: Craig DeShong on September 05, 2021, 08:10:37 PM ---As I got into the design I began to realize that an awful lot of stuff whirls around inside the engine case and getting it all to fit, let alone preserve the needed clearances was going to be difficult. This became so problematic that as the design progressed, I started doubting my skills in building something as complicated as the design was becoming. Reluctantly I decided to switch my efforts to designing a free-lance rotary engine with five cylinders.
--- End quote ---
I assume the tricky bit you refer to is the slipper arrangement on the master rod and the three concentric grooves. You could "cheat" and reused the mechanism used on the Chenery Gnome rather than be mechanically true to type inside the crankcase :-X
...just an idea ;)
Jo
RReid:
By the way, if you want to make the long drive to Bethel, Pennsylvania, the Golden Age Air Museum there has an accurate, scratchbuilt, DR-1 flying behind an authentic Le Rhone rotary engine (I don't actually know for a fact that it is a Le Rhone). Lot's of other cool stuff there as well, and they put on really fun airshows. Kinda like Old Rhinebeck, only different.
https://www.goldenageair.org/collection/1918_fokker_dr_i_triplane.htm
Elam Works:
I hate to be the one to point it out, but the intake pipes on the 80hp LeRhône 9C are on the trailing side of the cylinder. Rotaries had the exhaust on the leading side maximize cooling of the hottest bits of the cylinder heads. In the case of the 80hp LeRhône, things are rather more fortunate than its contemporaries as there are drawings of most all of the components as it was built under license by Union Switch & Signal in Swissvale, PA. Some of the drawings (photocopies) are very difficult to read, but in most cases the dimensions can be figured out from the mating component drawing. It does save a lot of experimentation and guesswork of proportioning the parts so they all fit together. Of course you might still simplify it dramatically just to make it easier to build. I got most of the way with my CAD model, less the rocker and valve gear before running out of steam.
The situation is almost as good with the 110hp LeRhône 9Jb, with most of the drawings available. The first pics in your post are of the 110hp, which had the intake pipes on the rear side of the crankcase. I did not get as far with that so not entirely sure what is missing in the drawing package until you go to look for something and find it is not there. Most other engines you end up scaling a cross section view from a handbook. Though in the case of the Clerget 9B I was able to borrow an original Gwynne built version, disassemble, clean, and reverse engineer it in the process. And if you have a British built Clerget 9B you have a third of the Bentley BR1. Not to be confused with the slightly bigger Bentley BR2 popularized by Lew Blackmore's serialization in Model Engineer and publication as a book.
-Doug
steamer:
I'll be watching this one take shape! The design work is a huge part of building from scratch, I can attest to that!
18" is a big engine....this one can hurt you!....Like Mike said, it can surprise you just how big they are....
I'm really looking forward to the build on this one! Get on with your good self sir!
Dave :popcornsmall:
Craig DeShong:
Thanks for all the interest. I’ll attempt to answer or recognize all the responses/questions.
Chris and CNR- great to have you along!
Mike: don’t know what I was smok’in yesterday. The scale is actually much closer to 1/3rd size than ½. The distance across the cylinders (rocker to rocker) is a tad over 12 inches (not 18??). One of the places where I’m deviating from the full-size engine is in the area of the cylinder head. The full size has blind cylinders with the valve guides set into the end of the cylinder (head). I’m not looking forward to boring out a blind cylinder and then reaching in about 3 ½ inches to cut valve seats and expecting to have much success, accuracy and a smooth valve seat is paramount; therefore I’ve designed the heads to be separate and I’ve decreased the bore of the cylinder so I can bring cap screws up from the bottom of the cylinder to ‘blindly’ attach the head. This should give the appearance of the head and cylinder being one integral unit on the model when in-fact they are not. In order to do this I needed to thicken the head so that it can accept the threaded ends of the bolts and an attentive observer will recognize this in the model.
The bore/stroke of the full-size is 4.13 x 5.51 inches. The bore/stroke of the model will be 1.125 x 1.425 inches. You can see that I’ve shortened the stroke (to get things to fit in the engine case) and decreased the bore (to accommodate the fasteners for the heads). The model will have close to 9 cubic inches of displacement so I doubt the decreased bore will be a concern in allowing the engine to run. I’ll probably need to use a smaller propeller.
I thought I’d start with the engine case, and assemble the engine as I go.
Ron: "old hat" for you I'm sure, but for others.... The Germans thought so highly of the Le Rhone that they acquired a few from downed allied aircfraft, dis-assembled the engines, and reverse engineered their version; the Oberursel U.R II. These engines were not considered as reliable as the Le Rhone, but further investigation seems to point to the oil being used. The Le Rhone and its clones operate on a total loss oil system, where the oil was injected into the engine, and then lost through centrifugal force through the many orifices in the engine case. The Allies had access to castor oil which was used as the lubricant; the Germans did not have access to castor oil, so they used an inferior oil, thus the increased incidents of failure of the Oberursel.
With a total loss oil system, this is a messy engine with oil being flung out in a 360 degree circle around the cylinders and blown back through the prop wash. Even though many of the airplanes had cowling over the engine the pilots still became covered with castor oil, having to occasionally remove their goggles and wipe them clean. This also resulted in ingestion of a certain amount of the oil and we can understand why a pilot might be compelled to hurry back to the airdrome after a mission. :toilet_claw:
On another note: I was up at the Rough and Tumble show in Kinzer, Pa. with my four Otto & Langen models a few weeks ago. They put me up in the Willock building and I was right across the aisle from the three full size Otto & Langen engines they have on exhibit (two of which I’ve modeled) I had a great time. I was also a hop, skip, and jump away from Bethel, Pa. I would have stopped by had I realized.
Jo: One of the engineering aspects of this engine is the slipper rings. I had to draw this up in my CAD system to actually see these things in operation. For those who don’t know… where most radial/rotary engines have a master connecting rod with all other slave connecting rods attached to a disk on the main rod with a bolt; the Le Rhone is different. It has no master connecting rod, but rather a disk on the crankshaft with concentric groves cut into it. Each connecting rod is connected to the disk with “slippers” that fit the groves in the disk. The nine connecting rod slippers have convex ends that can slide back and forth in the disk groves as required as the engine case revolves. They don’t slide much, probably less than ten to fifteen degrees but they do slip in the groves. I’m going to attempt to model this. This will take some very close tolerance fitting so the engine doesn’t have a lot of “rod knocks” when it runs. I’m eager to give this a go.
The slipper rings are certainly an issue, but the real problem was fitting the intake and exhaust cams, the cam rockers, and the gearing that drives the cams inside a scale size engine case. I can’t make a ring-gear in my shop as the full size uses to drive the cam disks, so I’m stuck with spur gearing. With a little “finagling” I managed to squeeze everything in.
Doug: :-[
Sometimes you get so deep into the forest that you can’t see the trees. I have no excuse, but I’m sure glad you caught this. I’d have made a scale model of a “nothing” had you not pointed this out. THANKS!
Finally, Dave: Glad to have you along!
So, let’s try this again…. A few photos of the Le Rhone 9C
I’ve revised the CAD drawing. Fortunately, the required changes didn’t cause too much of a fuss inside the engine case, and in-fact the re-positioning of a few components might have helped a bit.
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