New and Improved Lady Anne

[larry cottrill]

James D -

I should have one built out of plain steel before too long, unless it just stays too cold to weld out in the garage. The intake will be my bent sheet version, but the acoustic dimensions will be the same. The main difference will be that my intake will allow the incoming air to hit the dome at a slightly steeper angle. We'll see what happens - I still have faith in the basic dimensions, which leads me to believe that the flow details at the front end must be the main problem.

L Cottrill

[larry cottrill]

Here's a plan of a practical welding jig that I've almost finished building. What it does is basically make the main subassemblies (except the intake) essentially self-aligning with the jig in place. It basically consists of a front-end cap with a threaded stud (same as spark plug thread) and a pair of steel tubes, one 29mm OD and the other 32mm OD. These are different lengths and are 'telescoped' together and welded.

To make the front end cap of the jig, I threaded an M10x1.0 bolt and nut onto a thick washer, and welded them in place; then, this assembly was chucked in a small lathe and the outside of the washer turned down to 29mm diameter. Then, I turned a small "shelf" into the edge so it would fit neatly centered into the end of the 29mm steel tube. Since the end was carefully cut square, the protruding shank of the bolt lies on the tubing centreline. This was put together and carefully tack welded, then after checking the alignment by rolling across a flat surface, the seam was butt welded all around. Finally, the weld was smoothed down with a file so it will not hang up when the jig is extracted from the engine shell.

The next thing to do is fit the 32mm tubing onto the smaller tube. There is about a mm or so of gap, since the larger tubing is very thin walled; so, I'll wrap masking tape very evenly around the smaller tube at two places to form a good solid sliding fit. Then, each end will be welded at four spots, as shown on the plan. These two will need to be filed a little, to avoid any hanging on extraction of the jig.

To weld the Anne Boleyn angine using the jig, proceed as follows:

1. Butt weld the chamber dome to the front of the chamber cone, but leave the spark plug mount nut off for now
2. Butt weld the middle cone and the choke cone together
3. Verify that the narrow ends of all cones are sufficiently round to slide snugly on the jig tubes
4. Make sure there is a free (loose) nut threaded onto the stud of the jig, run down till it touches, but not tightened
5. Slide the mid-engine midsection (middle cone / choke cone assembly onto the jig, from the front end, till it's about halfway over the front end of the 32mm tube
6. Slide the combustion chamber subsection over the front end of the jig until the dome rests against the free nut already threaded on
7. Thread on the M10x1.0 jam nut that will become the sparkplug mount - thread it down finger tight against the center of the chamber dome
8. Thread on another free nut, running it down finger tight on the jan nut - this will protect the threaded stud from weld heat and splatter
9. Slide the mid-engine subsection forward until it's in good contact with the rear of the chamber subsection
10. From the rear of the jig, slide on the tail cone, followed by the steel centering disk with its three or four bolts
11. Slide the tail cone and disk forward until the tail cone is in solid contact with the mid-engine subsection, and secure with the hose clamp at the tail end of the jig
12. Rotate the subsections to align the cone seams however you think best - I like them all lined up, since I think that's the best appearance
13. Re-check to make sure that the subsections are being tighly held together
14. Fillet weld the jam nut to the dome, all around, being careful to NOT to weld to the free nut on top of the jam nut!
15. Make four to eight little tack welds around the chamber / mid-section joint
16. Make four to eight little tack welds around the mid-section to tail cone joint
17. While the welds cool, un-thread the free nut from the front end, leaving the jig threaded into the jam nut
18. Once the assembly is cool enough to handle, apply a little penetrating oil at the jam nut and the tack-welded joints and un-thread the jig from the welded assembly
19. Finish weld all the tack-welded areas on the main engine shell
20. Finally, tack weld the intake in place, then finish weld it and add the air starting tube and/ or fuel tube holder, engine mounts, etc.

L Cottrill

[James D]

Looks like a good procedure Larry.

With your bent sheet intake, how do you decide on the size of the opening into the combustion chamber? it seems like an important dimension.

[larry cottrill]

Looks like a good procedure Larry.

With your bent sheet intake, how do you decide on the size of the opening into the combustion chamber? it seems like an important dimension.

Dave -

Thanks. On the opening, the rear edge needs to be at the right spot according to the calculations, of course. Cutting it straight across should give tighter tuning to the intake than if it were a curve. I tried to design the intake duct so it is a not-too-flat quasi-rectangle at the rear edge of the port, and so its area is fairly well maintained from end to end (i.e. it is not significantly nozzle-like nor diffuser-like). What I end up with at the rear port edge and the taper of the sides determines the width of the port. If possible, I want to have the transition area flow smoothly into the port all the way around. I think with this layout, the only thing critical about the port area is that it is not smaller than the intake duct area, i.e. it is not acting as a "choke" for air going in or out.

Other than the calculation of the rear port edge location and the desired intake duct area, it's pretty much intuitive design, really. I have done nothing to make up for the proven inefficiency of a rectangular section, where the corners are of little benefit for flow.

L Cottrill

[Eric]

You are oftly brave using steel on steel as a jig!

Eric

[Mike Everman]

Yeah, copper would be better.

[larry cottrill]

You are oftly brave using steel on steel as a jig!

Yeah, copper would be better.

Actually, I've already tried tack welding cone ends on top of both thin steel tubing and steel conduit, with no problems. This was even though, in a couple of cases, my cutting accuracy was poor and the cones came together with a significant gap to bridge to close the seam.

Of course, one has to be careful ... ;-) The way I work, the underlying jig never gets to visible red heat (at least, as seen through the goggles). I can see where (some) electric methods might have trouble with this, though.

The thing I was really worried about is that the welded section would tighten after welding, and "seize" the underlying jig tube so I couldn't separate it. This "problem" did not materialize, however - it is a snug sliding fit, but can be twisted without undue strain.

L Cottrill

[larry cottrill]

James D et al -

I received a note and photo from Bill Hinote that may be of interest, and have his permission to share these. Bill wrote, in part:
__________

Larry:

Please see attached.

This motor started out as a version of my very successful M15E project
with the intake moved around to the side of the CC as shown in the
photo. This motor was a non-runner--not even close. No assisted
resonance, even.

I talked it over with Graham and we decided the path length was modified
because of the location; as a result I lengthened the CC to
compensate--and the result is a nice running, easy starting motor. The
addition is approx. equal to the radius of the CC.

Only problem is, it won't make any power!! I took a motor design that
will produce more than 14 lbf on a good day and turned it into a
weakling that does about 3 lbf on the same amount of propane. Ain't
that special!?!

...

Bill
__________

On thinking about this, I offered the following hypothesis:

The whole problem (as I see it) is that this layout is VERY DIRECTLY tapping into the pressure antinode / velocity node of the system. Acoustically, there is nothing wrong with this, as shown by the fact that the engine starts easily and runs smoothly. BUT, it means a couple of things are happening that turn out to be killers: First, the intake is being driven from the center of the air/fuel blast, i.e. a spot where the velocity is practically zero even though high pressure is supposedly developing. Second, it creates a low-impedance pressure bleed that is preventing the chamber from developing full pressure and adequate expansion.

The thing that makes this situation unique is that there is no "transition space", i.e. a zone of the chamber where expansion can be developed BEFORE anything in the intake has a chance to reverse flow and start getting pushed outward. My hypothetical conclusion is that, without this "transition space", the intake does not properly valve the chamber. The engine IS resonating, but not in a way that allows proper pressure development in the chamber where it counts.

I intend to develop this hypothesis further in a new thread. I don't really think this is what's keeping yours from working, James, but we may learn something more once I get mine put together. I think the engine as you built it has sufficient space to develop good expansion - note that in Bill's engine, the port into the chamber is a tiny fraction of the overall engine length - it sees nothing but the velocity node region. What he says about the length modification might be worth considering, though.

L Cottrill

[mk]

Interesting evidence, that Bill got the engine to operate self-aspirated with the inlet that much in front of the combustion chamber. Even though thrust output was reduced heavily, and dimensional sdaption was demanded.
Well, and note the heat distribution. Hmmm...

[larry cottrill]

James -

If you lose confidence in the extreme front intake location:

I have verified with UFLOW that the intake in its original location will work with the revised Lady Anne body style. This is a very strong design - it pressurizes well and runs out wonderfully, just as with the original pipe, but better mass flows due to the new body design.

I show this with my bent shell intake as Lady Anne Rev 05, below - but you can use your tubing intake just as well. In that case, the 43mm dimension would be disregarded. You would put the inside of the "elbow" (where the transition ends and the intake pipe begins) at the 77mm point shown. The intake is reduced slightly (just 2mm) from your last build to 111 mm physical length (again, measuring from the inside crook of the "elbow", out to the flare edge. Even with a good-sized flare, you shouldn't quite come in contact with the surface of the middle cone (as you can see in the drawing, the intake will overhang the middle cone by roughly 18mm).

Anyway, if between us we just can't make the front-end intake work, this is a layout that should perform beautifully, based on what you proved with the original Lady Anne.

L Cottrill

[James D]

Larry, I’m sure we’ll get it running one way or another.

Something I noticed when trying to run mine was that the pops and bangs from the tailpipe didn't seem very harsh, at the time I thought maybe it was because of the relatively large intake, but your explanation ("a low-impedance pressure bleed that is preventing the chamber from developing full pressure and adequate expansion.") might make more sense.

Hopefully I should get a chance to try it again towards the end of next week and I’m really interested to see how your build runs with its tapered intake and larger ‘port’.

[Eric]

Actually the non harsh cracks are not necessarily a bad thing, they can mean that you actually have a very good tailpipe.

With a straight tailpipe the gas shoots out the back at extremely high speed, where with a proper expanded tail, the transer of energy from the combustion chamber through the tailpipe is evenly distributed over a much larger final exhaust area, reducing exhaust velocity, but with much more flow.

With some tail pipe designs there can be some seperation in internal flow, basically the high velocity core gas shoots out and doesnt quite expand in the expansion chamber, unless it is of the proper dimensions.

The small advanced style chinese valveless for example will not make extremely loud bangs like some engines, in fact the pops and bangs are considerably more quiet than normal low throttle running. The more efficient and complete energy transfer also lets the engine run at much higher power levels too.

Im trying to think of the easiest way that you can make a pulsed air injector, perhaps if you use an existing style air gun nozzle and fit a fire alarm motor (the linear kind that strikes a bell) to activate the lever so that you can get some very fast pulse rates and adjust it by controling the voltage.

With a fast air pulse rate you should be able to get almost anything to run as a pulsejet so long as you have the spark plug and fuel injector in the right place.

Eric

[larry cottrill]

You are oftly brave using steel on steel as a jig!

Yeah, copper would be better.

Actually, I've already tried tack welding cone ends on top of both thin steel tubing and steel conduit, with no problems. This was even though, in a couple of cases, my cutting accuracy was poor and the cones came together with a significant gap to bridge to close the seam.

Of course, one has to be careful ... ;-) The way I work, the underlying jig never gets to visible red heat (at least, as seen through the goggles). I can see where (some) electric methods might have trouble with this, though.

The thing I was really worried about is that the welded section would tighten after welding, and "seize" the underlying jig tube so I couldn't separate it. This "problem" did not materialize, however - it is a snug sliding fit, but can be twisted without undue strain.

L Cottrill

Well, I have now used the jig to weld up the main body of my first Lady Anne Rev 03, and it is now ready for the intake to be added. It was a bear.

I thought the tack welding and plug mount welding went really well on Saturday. (Recall that the dome was already fully welded to the chamber cone.) However, when the whole assembly had cooled and I got it back down to the basement, I found that it was IMPOSSIBLE to break the internal jig loose from the shell! I even tried a pipe wrench on it, but the tubing end was deforming before anything broke loose to turn (remember, it has to be threaded out of the spark plug mount at the front end). I also tried shocking it with a hammer on the front end (a couple of nuts threaded on the M10x1.0 stud) - this of course was doomed to fail, with the spark plug mount locking it together. Let me tell you, this was an extremely frustrating moment.

I thought about this for a long time, and finally decided that I needed to start breaking the sections loose, from front to rear, even if I ruined them in the process, to find what the problem really was. I also suspected that it was one of the tack welds between the chamber and the middle cone: there was one tack weld that I dawdled over a little because I had melted back the cone edge slightly and added just a touch of filler rod to re-build it (should have let this go till later!!!). I thought that must be the problem. So, I used the jeweler's saw to cut through all the tack welds holding the chamber to the mid cone. I found that I was easily able to thread the chamber off the end! So, the seized point had to be somewhere "south" of where I had cut the tack welds.

Got back to this last night, and decided to open up the front of the middle cone a little using a 3/16-inch wide stone chisel (this is a tool just like a 'cold chisel', but tiny). I did this, opening up the entire front edge of the cone by about half a mm or so all around, but still couldn't twist it loose - so much for my theory about the overworked tack weld! At this point I noticed that I could "rattle" the shell on the jig - the front end was moving; the seized point was farther down the line, at the joint between the choke cone and tail cone! I decided to try the hammer once again, since now the attachment of the spark plug mount wasn't interfering with the force getting to the tight (or possibly, welded) spot.

I set the assembly upright between two scrap wood blocks (to protect the rear skirt edge of the tail cone), put a couple hex nuts back on the stud and gave them some pretty good raps with the hammer. After a few such blows, the jig broke free and began sliding (with considerable drag) down through the shell. I was able to extract it by hand, with some difficulty, the rest of the way. What I found surprised me, though it should not have ...

My mistake was not cleaning the paint off the outer tube of the jig!!! The jig was made of an inner galvanized tube and an outer painted tube. At the front end (the joint between the chamber and middle cone), the tack welds were over the galvanized shell (the galvanizing simply burned away during welding), but at the rearward joint (between the choke cone and the tail cone), the paint blistered up and burned, "gluing" the jig to the shell at each tack weld! Duh ...

Needless to say, I grabbed some medium sandpaper and cleaned away the burned paint in that area! Then, I reassembled the whole thing and re-tacked the chamber onto the middle cone. After that, I was able to remove the jig from the tack-welded assembly - lots of drag, but you could tell it was going to come apart as planned. Once the jig was removed, finish welding the joints was easily accomplished, and I had a finished engine shell as straight and true as you'd ever want.

I figure that burned paint cost me at least two hours of consternation and extra effort, plus a few minutes reassembling and re-tacking the parts. But, it turned out to be a chastisement rather than a divine judgment - at least I have something now that looks like an engine! AND, the concept of the internal jig is proven workable after all.

L Cottrill

[Irvine.J]

Way to go Larry, only the inlet to go!!! Cant wait to see this thing roar to life, you have worked really hard on it and have got my fingers crossed. Bad luck leaving the paint on there though, I can imagine the teeth gritting that ensued LOL! Speaking to the fabricators where i buy my metals, they tell me Galv+welding = BAD maybe the galv itself contributed to your frustration. Anyway, happy to hear you've got it worked out after some "white knuckle" adventures. I'm very excited to see if the engine performs as well as you'd hoped, "inline with the valved pj's at equal-ish length" if I'm to remember correctly. Go get em tiger!
Regards.

[larry cottrill]

James -

Thanks! I guarantee you that jig will work better next time ;-)

Remember, though, that this is my Rev 03 model - completely front-end loaded, just like the second one James D built. The question at hand is whether I can get mine to run at all. If I somehow get that far, THEN the question is one of power, as Bill Hinote brought up in his communication with me. So, if this runs, I've got to come up with a simple way to measure thrust.

One thing good about this one is the flexibility in experimenting with the depth of the fuel stinger in the intake duct. So, if it runs at all, I'll at least have one parameter I can play with, possibly with meaningful results. I should be able to weld up the intake and the starting air tube tonight. The starting air tube is, of course, also the support structure for the fuel tube. I also need some kind of mounting lug, of course - can't forget that.

Maybe I could get back to working on my 'raised garage door thrust stand' to check this baby out ...

L Cottrill