JU-87 Stuka engine gear. Looks like teeth edges rounded directly in form at forging process.
JU-87 Stuka engine gear. Looks like teeth edges rounded directly in form at forging process.
The first thought that comes to mind, is teeth cracking prevention. This is the crankshaft gear that turns propeller gear.
Yes,I agree that those fillets are to prevent cracking in that highly loaded part..I continue to be amazed at the very high quality of the parts built during wartime conditions with manual machines from all of the nations..My hat is off to all of the masters who have lived before us and that we may continue in their foot steps!
I read a bit about that a while ago.
https://www.geartechnology.com/issue...geardesign.pdf
Last edited by Muhr; 17th March 2021 at 08:51. Reason: I misunderstood the question
No amount of experimentation can ever prove me right; a single experiment can prove me wrong.
This makes con rods just so "ho hum"....
http://www.nadiraksoy.com/
"Success is the ability to go from one failure to another with no loss of enthusiasm.”
Radial piston hydraulic pumps and motors have been built in a similar way for years. The translation into an IC engine hasn't worked. It's a lot harder to seal a piston that's not bathed in oil at moderate temperatures.
Lohring Miller
Finally engine run today with intake through transfers type, adapted for Honda RS 125 GP cylinder. Still not ready for riding or dyno tests, just checked if this could work at all, without damage. Add short video https://www.youtube.com/watch?v=uK-MLMWTl-g
Thank you Ceci, but I have some doubts. Intake through transfers scheme, with Honda Rs cylinder, have one down side. Two wide exhaust ports restrict intake ( red zone) through whole A transfers area. Only at TDC piston fully uncovered A. With one exhaust port type cylinder, A is not restricted, but exhaust became restricted.
Yes, this could be huge restriction if the all flow mass, that goes into crankcase through A and B, evacuated only through the bottom crown side reeds.
But with this concept, I guess the most interesting thing is that the bigger part of the mass flow returns to the transfers channels, again through A and B windows when the piston moves down. The previous inertial flow from carb collided with returned flow, intake reed valve closes and all this increases the high pressure in the transfers tunnels. And this is why, maybe it is possible extract something from this concept.
Yes, crankcase separation crown with reeds, just needed to evacuate what left in the crankcase and later this helps to increase negative pressure just before the intake process started through A and B, when piston moves up.
As flow through A and B goes in both directions, before they opened for scavenging, even small restriction could be critical for build up high pressure in transfers tunnels.
Would be good to do three main comparisons tests with the same cylinder.
1 Spec piston and separation crown with side reeds (intake through A and B).
2 Spec piston and opened crankcase ( normal intake )
3 Std RS 125 piston and opened crankcase ( normal intake )
Still not ready for tests, but not many things left to do.
Finally finished tests with direct to transfers intake configuration. No dyno, just all road tests 800 km, always on the same 3km section, so just comparison between different configurations, but this enough to feel the engine reactions.
Test engine
Honda NS400 crankcase with adapted modified NSR 250 (54,5mm stroke) half crankshaft to 1cylinder.
Cylinder Honda RS 125 gp, with 22,5mm thick plate between cylinder and crankcase for reed intake route. Because of this conrod length 120mm ( original NS400/250 and latest Honda RSW 250 109mm and std RS125/250 104mm)
Carburetor Mikuni TMX05 38mml in non pressurized airbox, reed valve cage RGV 250 with manifold from Polaris Sportsman 500 HO
Ignition Honda RS 250 1987 (some tests with Honda CR 125 2003 ignition, but rev limiter at 13700rpm. )
Pipe Honda RS copy stainless 0.8mm
Pistons for normal configuration
1. Honda RS 250 nx5 A kit locating pin at C
2. Custom made identical to Honda RS 250 just with lowered side transfer cutouts, at the level that A and B is closed when piston at TDC.
Piston for direct to transfer intake configuration, custom made from 2618 alloy with special shape that works together with crankcase, one way flow, separator. Intake duration through A,B fixed at 206 degrees.
After many back-to-back tests, with huge other small changes, the power with standard configuration were higher from low to 10000 /10500 rpm and more or less similar at max 13000 rpm.
There was not a surprise of lower output at mid range, because very similar reaction was from previous last year test with one exhaust port NS cylinder. But doubts about restricted intake through A (because of wide two exhaust port Honda RS cylinder), seems confirmed, as no improvement at top end over standard configuration.
Honestly I was happy, that for this 3-cylinder NS project with RS barrels, no need to do complicated pistons and crankcase separators, until decide to do last modification with direct to transfers intake configuration.
So finally decided to destroy cylinder and cut two compensation intake passages under front part of A, positioned at same angle where exhaust overlapped A. Passages opens and closes at the same time with A and B. The total additional intake area corresponds to 18mm dia.
The engine reaction was what I looking for. From 10000 to 13000 rpm the best output of all tests after four moths, wheelie in 1 and 2 gear. Mid range better than before, but not higher than with standard configuration. And most importantly, it was repeated on other days.
I guess that if A opens fully all the way like B, without piston skirt restriction, engine goes even better without additional passages, but this is impossible to do with exhaust ports that partly overlapped A. and A fully opens only short time just at the moment when piston is at TDC
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