Ohrndorf 5 Cylinder Radial

[petertha]

PS any residual oil left in the crankcase after a run, will drain down into the lower cylinders. past the pistons and into the cylinder heads. There is a danger of a hydraulic lock if too much oil reaches the cylinder heads. It is normal practice to walk the engine through at least 2 complete revolutions (eight blades)  to clear the oil before appalling the starter

Good advice. On my inverted RC engines I disconnect fuel, remove the plug & rotate prop around many times to drain anything that shouldn't be there for that exact reason. Or particularly if it didn't start right away & there was any chance of fuel flooding.

I could probably look it up, but do you happen to know if your Seidel radial has openings to the gears/cams for induction mist lubrication like the other engines I've shown?

[Admiral_dk]

OS uses a nice circulation system without any pump in their four strokes. It works with the oil that pases the piston ring and ends up in the crankcase. Some of it is hit by the crank and lubes the bottom end and piston pin(s). As it has a positive pressure in the crankcase, the oil is pushed out into the bearings and to the cam gears and shaft. From there it goes up the push rod tubes and lubes the rockers, axle and valves.
And now to the really smart detail - there is a very small diameter short length hole from this cavity to the inlet port, where there is a negative pressure -> the oil is sucket back into the combustion chamber - repeat (as some is burned - you need some in the fuel too).

[petertha]

Re the OS 4S, I kind of figured that must be how it works on majority of RC 4S engines because they all have tubes enclosing the push rods & silicone O-ring type seals on both ends of the tubes. When I've dissassebled them the rocker assembly is completely oily looking.The valve cover usually has a gasket, so you know lubrication is working to the extent they don't want it to leak out.

The O5/O9 has pushrod tubes as well but... its another one of those things I'm scratching my head a bit now that I'm getting into it. The tappet bushing is kind of a conical external shape, presumably so the tube can rest on it at a 3D angle (maybe with a bit of mitering). Where it gets interesting is the rocker perch end. Now the receiving tube hole has to be at a funky 3D angle because the inlet & exhaust pushrods are at different angles based on the forward/aft positions of cam plates. Then he has a lateral set screw through the perch base that indexes into the tube. I'm no expert but it looks fiddly to me. 

Then when I look at the the shop made radials like Edwards & Jung, they all have exposed pushrods, no tubes at all. So are the rockers getting sufficient lubrication from valve/cage blow by or is an occasional manual drip before running all thats required? I'd like cover tubes & I've spent some time looking at the motion geometry. Its yet another kick-the-can-down-the-road theme, but my plan is to drill oversize holes in the rocker perch & then figure out some kind of rubbery fitting that will both capture the tube & seal it a bit. I've had a little bit of experience making rubbery-like urethane or silicone parts from aluminum molds. These are pretty teeny. But I'm getting ahead of myself.

[dieselpilot]

OS uses a nice circulation system without any pump in their four strokes.

Some OS engines used one form or another for a very long time. FS-120 Surpass since the 80's. SurpassII versions of FS70 and 91 also used it (case vented to intake manifold).  The most recent iteration you describe above was used in the first Alpha series which added passages by the cam followers (only low volume car versions of FS-26S-C and 40 had this prior) and the hole to the intake in the head. They have reverted to a normal case vent in the II versions of FSa-56 and 72. In the real world, with overly rich needle setting, excessive oil in the fuel, inverted installations, that system caused inconsistent running in the smaller engines due to randomly pulling rather large volumes of oil when orientation promoted it. I have added this system to several engines and never noticed unusual behavior, but I don't run typical fuels or oil ratios. OS rarely used gaskets.

Some complained about rusty bearings due to the closed case. I ran mine up, got them hot and let it idle for a while prior to shutdown. Some people like to push after run oil into the breather vent, and this wasn't possible with the closed system. There was one I left on the test bench for a week and ended up with bad bearings.

Exposed rockers need regular oiling, just like full scale. Even enclosed valve train can end up quite dry in RC four strokes. Varies with type of oil, how hot it runs, fits of parts, though most seem get oil. Valvetrain doesn't need much being properly hardened. Until recently as mentioned above, rockers were lubed by want managed to squeeze by the followers and valve stems.

[petertha]

Interesting, dieselpilot. I'm probably mistaken then about valve cover gasket being present. I cannot honestly recall which of my dads 'castor-bunged' engines I disassembled (there were so many haha). Thought it was an OS but like you say they have spanned many years. Looks like the newer OS 4S are no gasket. I might be confused with YS which was more familiar to me, but maybe that was related to the air box boost? Interesting the Saito gasoline (with premix oil) has gasket.

Maybe the silicone fittings at the ends of the pushrod tubes are more about fitting up the 3D angle geometry & withstanding vibration etc as opposed to sealing oil residue.

Also attached OS methanol snip regarding crankcase drain.

[Art K]

You got a bit ahead of me, had a busy evening yesterday. The small Kinner was a 1/6 scale. I did Talk to someone at the NAMES show in Detroit who built Jemma and said there were discrepancies and get in touch with him if I built that. Didn't get anywhere with that one either.
Art

[petertha]

Ya. This is just my own beginner opinion, but design discrepancies scare me. Especially if discovered late in the game. I'm sure all plans have the potential for boo-boos, its just to what degree. I get it, these creations originate from human minds. And many designs created in the absence of modern software to validate things. And we have to pick a project we enjoy & stay motivated through tough times. That's kind of how I landed on this engine for better or worse. I figure if I can build it & get running, I'll be in a better position on future projects. Happy to pay my dues following others with much more experience than me.

Just as an aside, I mentioned the Edwards (free plans) & Jung designs (purchase plans) were next in line on my list
https://www.cad-modelltechnik-jung.de/construction-plans-model-engines.html
Jung recently revamped his website & lots of links of running engines, which for me is a confidence builder

I like this link. Lots of construction pics & he had the kahunas to strap it in a model. Its not an gasoline/ignition like Jemma but 7 cylinders.
http://philsradial.blogspot.com/

[dieselpilot]

OS machining has been very nice for a very long time, so they don't use gaskets in the four strokes for the most part. YS on the other hand, operation depends on proper sealing. Another intersting note is that virtually all steel components of the better glow engines have been coated for rust for over a decade now.

Saito have a similar design with the pushrod covers. They use fairly thick gaskets at the perch to seal and a sleeve at the follower guide. https://www.horizonhobby.com/product/pushrod-cover-and-rubber-seal-2-ca/SAIG60R340.html

[petertha]

Crankshaft Intro

The O5 crankshaft was turned from a bar of 1144 SP (stress proof) steel. This was the first time I've machined this material & I don’t have much comparative experience to similar tougher alloys like 4xxx series, but I was pleased with the results. The material specs are: 83% machinability (1212 reference = 100%), 132 ksi tensile, 100 ksi yield, 27 RC hardness. It turns & finishes well with my offshore carbide inserts. But the important claim to fame by other engine modelers is that it’s less prone post machining stress relief distortion on parts like crankshafts with irregular geometry.

The crankshaft is solid, by that I mean the counterweight profile and crankpin are cut from the same stock (as opposed to a built-up crankshaft with separate components). While probably stronger, a one piece also means quite a lot of waste material removal to get down to the much smaller shaft OD area.

[petertha]

Rough turning was relatively straightforward, I just took it easy for the most part. It was around this time that my complaining lathe threw in the towel, even with moderate DOC. The clutch started rattling (disengaging), the finish was progressively crappier & I could feel this was more serious. So, reluctantly I had no other option but to remove the stock before the critical finishing stage & deal with the lathe.

The repair was a long, drawn out process. I won’t go into details but some of the story is documented here. https://www.homemodelenginemachinist.com/threads/14x40-lathe-power-feed-improvement.27629/#post-318716
The problem likely originated on the factory floor – somewhat flaky design, skewed power feed rod & misaligned related driveline components. I hope I don’t have to repeat this anytime soon, but the upside is that it’s never run better & I have a deeper understanding of my machine.

The rear end stock was held in 3-jaw and front end in live center. With the rough turning complete, it was critical dimensions time. There are 4 bearing races and a spur gear which are slip fit on various OD sections. In retrospect this was my first real go at having to produce OD’s within a couple tenths and simultaneously with good finish. My lapping methodology was kind of crude, & learn as you go, but eventually the job got done. It is important to let the part heat stabilize to room temp after turning because that can easily trick the OD measurement. Something I would now do when it comes to bearing fits on a CS or part with a lot of time invested is turn or utilize a dummy gage pin to establish the bearing fit beforehand, then use the same (quality) micrometer to translate that dimension to your part as you transition from turning to finishing or lapping. The last of the turning related operations were completed – groove for retaining ring and (hand) threading for the spinner nut. The part was removed from the lathe & band sawed to rough length.

[petertha]

Crankpin Roughing
I decided to rough most of the excess material in the mill leaving a remaining square of crank pin material for finish turning in the lathe. This setup also allowed me to make a center drill mark to the exact crankpin throw radius and also drill/tap the 2 holes for the added counterweight slug fasteners.

[petertha]

Crankpin Turning
Next I made an aluminum holding fixture that was a close sliding fit over the finished shaft OD. It has 2 through holes to match the counterweight tapped holes. It also has a milled flat on one side parallel to the bolt hole line, a reference surface for later. This fixture provided something for the chuck to grip & the bolts acted as kind of dog to transfer rotation. The crankpin center was dialed in with a DTI against a pointer rod extending from the tailstock. With setup established, the crankpin was turned down to diameter as well as the rear face of the counterweight profile and a thin boss profile for the master rod bushing. I tried a different style of lapping tool which was kind of a squeeze clamp affair.

[petertha]

Counterweight Profiling
Back to the mill. With the holding fixture still on & reference surface presented to the vise, the counterweight profile was cut out. Then the roundover profile was milled & hand filed away using a slip on guide bushing.

[petertha]

Crankshaft Counterweight
The design calls for an additional counterweight mass which is bolted to the matching crankshaft profile. One of those 5 minute jobs that took 3 hours. It has a relief arc cut to accommodate the master rod, but its center occurs at a different center than the OD, so required 2nd setup in the 4 jaw. I integrated that registration point in the same fixture used to hold the crankshaft for crank pin turning. Brass face mills really nice with the sharp uncoated inserts used on aluminum.

[petertha]

Some partial assembly at this point