Moderator: Mike Everman
Rossco wrote:Nice progress Larry,
Very interesting about the volume ratios.
Hows this for some numbers for you?
Diameter from front to back is 3" constant, minus the necked down bit which is technicaly two six inch cones back to back, that are about 2" D in the middle.
The CC is about 20" long to the restriction. And the tail is about 60" long!
Considering the volume of the CC is minus the intake in the middle, this gives some way out proportions to the ones you are coming up with!!!
. . .
hinote wrote:Also, I'm convinced that a megaphone in the tailpipe assembly is a necessary part of the makeup of this family of valveless PJ's. It creates the extended rarefaction duration necessary to "activate" the intake end, and then re-magnifies the returning compression wave to provide the necessary front to compress the fresh fuel/air charge. Without the megaphone there's just not enough energy available in the tailpipe action to do the job with any degree of efficiency.
Avenger wrote:Wow, a lot smaller than I expected. Nice precision work here! Keep us informed!
brunoogorelec wrote:Larry, we are waiting for the report on the first firing with bated breath. If you don't report soon, we'll all turn blue in our faces.
Rossco wrote:Im so slack!
My projects look so slapped together compared to yours larry.
My new Biggun took me 9 hrs in total. From sheet to firing. I'd love to spend the time to put the finish into it, but i so rarely get that much time in a row to build something that i just went for it.
I dont want to take too much of a side road, but i would like to look further at dimention ratios.
This little engine of yours has limilar ratios to my sort of idea of the "common" or expected. Intake small, CC big, and tail somewhere inbetween. To put it in very simplistic turms.
My inside intake engine made out of drive shaft pipe, that i gave rough dimentions of before in this thread, runs great. Intake 1", CC 3" and necking down before the tail is about 1 3/4 - 2". It doesnt throttle up very far before flaming out, but once its up and hot, you can "pump it up". I give it a blast of air when its already running, this steps up the frequency a bit and dumping more fuel in at the same time really puts up the power out put and returns to its normal sound but louder. It then sustains at this higher level. I can do this about 5 times before going over its limit and flaming out.
My big engine will not sustain again. 10 sec in the maiden run is all that i got out of it.
The diameter ratios of it. (sorry about the measurment system jumps, this is off the top of my head and its as close as i can get to accurate) (its late, i have too sleep, not think)
Intake funnells down into the CC to 2"
CC is 250mm and 250 long plus the funnel down to the restriction of 100mm. (for volume the intake up the centre has to me taken into account.)
this necks down to about 4" at the restriction and then funnels nearly all the way to the end of the tail to 200mm.
The monster is 7' long.
I really should give you a diag, and even more so some photos. Later. when i have more energy. And i still do not have any shots of either running yet!
This big one i think the problem is the restriction funnel does not go small enough. most lockwoods ive seen have the intake nearly the same size as the intake and half of them have it bigger!???
I think this one opperates like the lockys, i just built it this way because of my tests with my test rig. Larger in the restriction than the intake.
Its not at all a bad thing tho. The intake is removeable, and i plan to put a cone aft of that acting as a pressure wave deflector (as ive had success in my test rig). This cone will protrude down into the restriction zone, lessening the CSA. Effectively this will give me a variable restriction with different intakes made up with different cone lengths.
Ive just had a closer look at "the" lockwood-hiller engine itself. The intake is at least TWICE the initial restriction size!
In my experience this lets it throttle harder. But i bet it has to be up hard to start too. Ill think of a way to be able to change the intake size and volume too in the test rig and get back to you on this one. Will the same length but larger diameter intake still run at the same frequency at a higher apmlitude? I dont see why not? How about an intake throttle body, best of both worlds! could even be self govorned.
Unsubstantiated thought is running away from me again!
PS Larry, do you have some thoughts on my "sonic exhast nozzel"?
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