Ohrndorf 5 Cylinder Radial

[petertha]

Before leaving the crankcase for now, I wanted to elaborate on the oil bath lubrication details. I mentioned the O5 design calls for the nose housing to be partially filled with oil. The cam plates, planetary gears & bearings spin inside this housing so bath makes great sense from that perspective.

This view shows the approximate oil level based on recommended fill up volume. Notice how the bottom set of tappets (cam followers) would always be submerged in oil. I envision even medium viscosity oil working its way out through the annulus gap between the cylindrical tappet & the bronze bushing ID hole. The tappets are sliding fit & perpetually moving up & down. So possibly even some light pumping action. Maybe any bypass oil volume is minimal & just migrates down the pushrod tube where it ends up in the lower covers. I’m not really sure. Obviously it must work because it’s common to the larger O9

 

[petertha]

Here are some other methanol radial engines for comparison. The common theme seems to be that the gear plate mounted to front side of CC has openings to allow oily fuel it’s to carry forward & lubricate the gears, cams & bearings. There is no compartmental liquid oil bath like the O5 & O9.

OS Sirius

 

[petertha]

Jung 7-cylinder radial (Jung-5 is similar)

 

[petertha]

The Edwards radial has an integrated oil pump actuated off the crankshaft. Oil from external tank is directed to specific areas. It drains by gravity into a lower elevation sump where it is recirculated.

 

[petertha]

I like the Edwards principle. I seem to recall the recommended fuel was straight methanol/nitro and either zero or low percentage (insurance?) oil added because of the pump. It’s too late to integrate a similar mechanical pump into the O5, it would require be significant modifications.

I’ve toyed with the idea of external electric oil pump. I suppose it’s maybe kind of a cheat from vintage standpoint, but so are glow plug drivers & other modern necessities. The engine wouldn’t look out of place with external oil feed lines to the nose area. But I know nothing about what kinds of pumps would work so any thoughts welcome.

But if I trust what I think I’m seeing of the mentioned designs which includes established commercial RC engines that probably see much tougher service, then all I would have to do is cut an array of openings into the front gear plate & it might closely resemble that arrangement. Remove the bearing shields as previously mentioned & fingers crossed that rear entering intake mist sufficiently coats the important rotating bits in the nose case.

 

[Michael Rosenbauer]

Keep in mind, the gasket sheets change the compression ratio.

 

[tornitore45]

A note on the Edward 5 pump.
I built it to print but added the recommended springs because I had a feeling that all this little fiddly parts would not pump much.
I was surprised to see the oil running pretty fast and consistently when I run the engine. That double pump works great.

 

[petertha]

Keep in mind, the gasket sheets change the compression ratio.

Exactly. That's why I'm trying to select material thickness as minimal as possible. The stuff I found to try is 0.1mm (.0039"). Maybe a bit less once sandwiched. I have seen the same material as low as 0.001" but just as convenient to get (for me in Canada). Initially I thought I could skim the difference off the bottom of the flanges but the way the assembly is configured now, the liners have a slight shrink fit & the liner skirt protrudes out of the bottom so flange skimming is not a good option. So any CR adjustment will have to come from the lip of liner. I'll have to go back to my notes but I think I'm still well in the (upper) range though so hopefully OK.

 

[petertha]

A note on the Edward 5 pump....

I think the Edwards pump system was a smart idea on his part. Oil is directed to where lubrication is most needed & properly sucked away for re-circulation. I think I will spend some effort on the next methanol engine to incorporate a pump. I think the rule of thumb in methanol engines is if its fuel wet then its getting sufficiently lubricated with the pre-mix but I'd rather have more confidence.

Now that you have had some run time on your engine, have you noticed anything of note operationally?

- I don't recall much for gaskets or O-rings on the Edwards plans but been a while since I looked at them. Did you do anything on your own engine for flange seals? How is the assembly for oil seepage when you run it? Do the rockers look lubricated or do you do them manually before a run?

- do you notice any kind of liquid (oil or spent fuel) loading on the lower cylinders? As in important to remove the plugs & turn it over by hand so no hydraulic lock?

 

[Michael Rosenbauer]

By final assembly I will take a smal amount of Hylomar blue agent, to seal any necessary parts. At the crank case housing i made groove´s for nitril O rings but I will set it also with Hylomar .

 

[minh-thanh]

Hi petertha !
I don't understand how the engine's gears and cams work, can you or anyone explain it to me ?
The better ,if there are sketch images
Thanks !

 

[Michael Rosenbauer]

The gear on the crankshaft drives the middle gear which drives the inner gear to the same direction like the crank. Inner gear and camdisk are connected.
Ratio of this gears turns a cam at the right time to the lifting lowing angels. Intake- compression - ignition- exhaust!
You find runnig scetches on GRABCAD type in RADIAL ENGINE

 

[petertha]

Hi minh-thanh. As Michael says the spur gear on the crankshaft drives an identical gear on a 2 gear cluster. The smaller cluster gear then drives the internal (ring gear). The ring gear is attached to 2 identical cam plates mounted face to face, one for inlet, one for exhaust. They have an angular offset to one another to yield the correct inlet/exhaust timing. Each cylinder has a tappet (cam follower) sliding in a bushing & connected to pushrod which actuates valve rocker. I will have more pictures coming with all these parts & discuss engine timing too, but that's basically how the cams work on this style of radial engine.

 

[josodl1953]

I built my Edwards without an oil pump and kept the cam housing separate from the crankcase. I fill the cam housing with gear oil SAE 80 and it works fine. Leaks from the lower cam followers is minimal. Crankcase is lubricated by blow-by oil from the fuel . I made two vents in the crankcase rear cover so I can flush the crankcase after running. Methanol and nitro can cause nasty corrosion if left in a confined space.

Jos

 

[Vietti]

Because of the cam ring cam placement almost all radials are odd numbered so the cams don't do something unwanted at 180 degrees,see Petertha's 0024 jpg above. I suppose most all know this but it took sometime for me to discover this.

 

[minh-thanh]

Michael Rosenbauer , petertha !
Thanks !

Hi minh-thanh. As Michael says the spur gear on the crankshaft drives an identical gear on a 2 gear cluster. The smaller cluster gear then drives the internal (ring gear). The ring gear is attached to 2 identical cam plates mounted face to face, one for inlet, one for exhaust. They have an angular offset to one another to yield the correct inlet/exhaust timing. Each cylinder has a tappet (cam follower) sliding in a bushing & connected to pushrod which actuates valve rocker. I will have more pictures coming with all these parts & discuss engine timing too, but that's basically how the cams work on this style of radial engine.

Thanks for the images, the images make it easier for me to understand !

 

[petertha]

Crankshaft Intro

The O5 crankshaft was turned from a bar of 1144 SP (stress proof) steel. This is 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. 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
14x40 lathe power feed improvement

The problem likely originated on the factory floor – somewhat flakey design, skewed powerfeed 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.

 

[petertha]

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.