| From : |
Mark |
| Date : |
2003-06-04 12:23:54 |
| Subject : |
Re:Simple Adjustable Inlet Nozzle |
Larry Cottrill wrote :
>Purchase a long set screw and a hexagonal 'castle nut' [the kind that are grooved all around for cotter keys to be put through] with matching threads. Try to get these in a 'fine' thread [the set I bought was 1/2-in x 20 TPI].
>
>You'll find that you can thread the 'point' end of the set screw a little way into the 'castellated' [grooved] end of the nut, just until the thread catches hold all around. This leaves six good sized, nearly identical ports which can be gradually 'valved down' by screwing the set screw in farther, all the way to 'cutoff'. Thus, you have an easily adjustable [though rather heavy-duty] inlet nozzle for jam jars and small valveless engines.
>
>Unmodified, the six ports will not equal the clear diameter of the nut [so, you won't get an effective .5 inch diameter from a 1/2-inch nut, for example]. If you want to increase the air flow capacity to closely resemble the nominal diameter of the nut, take a small round file [needle file] and file from the outside downward at the bottom of each groove, going in at a 45-deg angle down toward the center, through the threads just below the bottom of the groove. You'll end up with six round-bottom channels. With this modification, the maximum capacity is greatly increased and the screw goes a lot farther into the nut before 'cutoff' of the air paths is reached. The air path is also much smoother overall. Another possible improvement would be to drill out the thread of the nut from the bottom side -- you only need threading up in the castellated part for the assembly to stay together.
>
>File the plating off the bottom [flat end] and solder, silver solder, braze or weld the bottom of the nut to a large washer to make a 'jam jar' top plate. Or, weld the bottom of the nut onto the nose of the [oversized] intake tube on your engine. If you drill out most of the set screw, you can weld on a tubing 'stack' for a 'Reynst Pot' model jam jar -- what excitement!
>
>For adjustment, you'll need a piece of hex stock or an Allen wrench that fits the socket in the screw. If the fit between nut and screw isn't too snug, you can probably make adjustments even while your 'engine' is running and the parts are hot.
>
>Pros: Cheap and super simple, and once you get it set for proper running, it should give you a decent rough estimate of the inlet area you need for a more 'finished' model.
>
>Cons: Notable defects are significant path roughness and abominable weight.
>
>I'm planning to try a little Mark 'Thixis' style jam jar with this design.
>
>L Cottrill
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Would be interesting to see a sketch with all the trimmings you do so well. Everyone likes drawings and pictures.
Mark |
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Re:Simple Adjustable Inlet Nozzle
( 2003-06-04 12:23:54)