Graham C. Williams wrote:Larry.
What have you been doing? 2.6Lbs straight off the drawing board!!!.
Is that pretty good? It's a far cry from the Dynajet, which to me is the standard for everything. Been doing? Not much this year except working my day job and helping take care of horses (we have a new colt, 3 months old tomorrow).
And the motor's so nice and short.
I like them to give out a nice eery high-pitched squeal ;-)
We must try this beast on Methanol, could get up to 30% extra if you can get the injection correct.
That would be better, for sure. What would be a real hoot (as we rural American folk like to say) is if it turned out just by chance to be BETTER tuned for some liquid fuel than it is now, and the thrust took some really amazing jump. One might as well dream ...
My precise calculations show that to achieve the T/W ratio of the Dynajet, we would only have to reduce the engine weight to 9.79 ounces. Though bulky, that would certainly qualify as a flight engine if liquid fueling could be properly arranged. Of course, if liquid fueling really does improve thrust, if wouldn't need to be quite so "trimmed to the bone".
It's hard to imagine crash integrity in such a lightweight shell. The mounts I show in the plans would never do. Probably the best method would be to eliminate those entriely and use the Bukowsky-style "spark plug engine mount" at the front end, with just a lightweight truss strut at the rear for lateral stability. The chamber dome is such a small area that it could still be fairly thick material to spread the crash load, without weighing much. The rest of the engine (except the intake tube) is basically a stack of long cones, which would be pretty good in longitudinal compression from forward-running impact - especially if very low mass. I'll try to work out a thickness (in stainless) using Eric's calculator, abd we'll see if anything reasonable can be achieved. Jerry said the Dynajet shells were .015 inch thick material, SS Type 321, so that will give us something to compare to.