rklopp
Well-Known Member
- Joined
- Oct 6, 2008
- Messages
- 375
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I just finished up Mark I Mark II Nalon Vipers from plans purchased from Ron Chernich at ModelEngineNews.org. They are rear rotary valve, ball bearing, 0.15 in3 (2.5 CC) "Diesels." They both run great, but they're LOUD!
About the only deviations from the plans were in the design of the conrod and to have the wrist (gudgeon) pin be a press-fit in the piston, rather than floating. I CNC-milled my conrods in a typical I-beam cross-section. The plans called for a round cross-section. I used black Delrin for the valve disc.
These are not beginners engines due to tricky cylinder porting and fine fits involved with the ball bearings. The needle valve assembly is unusual, consisting of a diagonal slot in the fuel tube spanning the venturi. The slot is blocked to varying degrees by a "needle" with no point. It works fine, but the fuel tube seems weak due to the amount of cross section removed by the diagonal slot.
About the only deviations from the plans were in the design of the conrod and to have the wrist (gudgeon) pin be a press-fit in the piston, rather than floating. I CNC-milled my conrods in a typical I-beam cross-section. The plans called for a round cross-section. I used black Delrin for the valve disc.
These are not beginners engines due to tricky cylinder porting and fine fits involved with the ball bearings. The needle valve assembly is unusual, consisting of a diagonal slot in the fuel tube spanning the venturi. The slot is blocked to varying degrees by a "needle" with no point. It works fine, but the fuel tube seems weak due to the amount of cross section removed by the diagonal slot.
