View Full Version : Making a model hit and miss engine hit and miss.

brian Rupnow
03-05-2011, 01:52 PM
The model Hit and Miss engine I built works very well, but I have been attempting to build a mechanism which would automatically impose a load on the engine at intervals to demonstrate how, when under load the engine will fire on every second cycle like a true 4 cycle engine. Then when the load is removed, it will fall back into "hit and miss" mode. I have had some success with the mechanism shown, but have decided to go another route.
http://i307.photobucket.com/albums/nn294/BrianRupnow/th_MovieHITANDMISSUNDERVARIABLELOAD-1.jpg (http://s307.photobucket.com/albums/nn294/BrianRupnow/?action=view&current=MovieHITANDMISSUNDERVARIABLELOAD-1.mp4)

brian Rupnow
03-05-2011, 01:55 PM
When I recut the groove in the large pulley so that it has a tapered bottom instead of a flat bottom, that stopped the belt slippage. The problem is that this small engine is too powerfull for this type of mechanism to "display" really well. And the mechanism, while correct in theory, is too damn big and clunky looking. I'm pleased that it works, but I think I will take a closer look at G Britnells suggestion of a Prony brake. Perhaps not a band style brake, but rather a pad style brake with a felt pad, on a peice of spring steel which could be activated by a small handle with a rotating cam. The felt "pad" could possibly bear directly on the outer face of one of the flywheels.(I'm not sure how the bronze would stand up to that). By simply flipping the short handle on the cam thru 90 degrees it would engage and lock the brake in place, imposing a load on the engine to make it 'hit" every cycle, and the amount of pressure would be regulated by the spring steel supporting the pad. Hmmm---I'll have to think on this.----

The Artful Bodger
03-05-2011, 04:25 PM
You could make a permanent magnet alternator connected to a few light globes and some sort of mechanism to switch the lights off and on. Or perhaps you could switch in more or less globes to vary the load and adjust for 4 stroking, 8 stroking, 12 stroking etc!:D

The alternator could be part of the 'display' if built in ye olde style.