Proposed FWE III Sveldt Lady for Jet-Age Blacksmiths

[larry cottrill]

If you're into smithing, this may be the engine for you!

Since Bruno proved that the Fo Mi Chin II engine runs "sweetly", we can now use that intake design with the FWE chamber to create the 'Sveldt Lady', an FWE that will fit anywhere a Dynajet can go - overall length is 21.5 inches, front view profile is a 2.6 inch OD circle! The tricky weld underneath the intake is gone, but this time you have to make the cone out of a big "horseshoe" shape, as shown below.

The intake is made from a half-shell cut from a pre-flared piece of 1.25-inch tubing, exactly as in the FMC II but pinched a hair narrower to expand the center height a little for better intake cross-sectional area. Starting air / fuel tube is my standard design, fabricated from 1/4-inch OD brake line and 1/8-inch OD copper tubing. For intake fabrication details, see the photos in my Fo Mi Chin Re-work thread in this forum. See:
http://www.pulse-jets.com/phpbb2/viewtopic.php?t=1767

I WILL be making one of these, from the second chamber cone Steve made for me; however, anyone who's itching to try a new design can blast away at it and beat me to it, if you want to be the pioneer builder [guinea pig, lab rat, etc.]. Go for it!

Why am I calling this one Version III? Well, as I see it my original planform and anything basically scaled from it is version I, and the 'straight FWE' designs developed by Steve and Eric should be Version II, leaving this one as Version III. The way I see it, scaling and minor variations in intake dimensions, etc. are merely 'variations', whereas 'version' implies a significantly different profile to some part of the engine.

Good luck!

L Cottrill

[Jmitchell]

I was going to rebuild my short lady, but I'll do this instead!

[larry cottrill]

I was going to rebuild my short lady, but I'll do this instead!

Man, go for it! Just keep us posted. If you have any questions on that weird intake, don't be afraid to ask. But, studying the whole series of photos on the other thread should show you just about all you need to know.

Best of luck!

L Cottrill

[larry cottrill]

Well, duh ...

While I was washing my hair this morning, I suddenly realized that I could make the cone sheet much easier to cut and roll by splitting the oval slot in two and sliding the halves out to the straight edges.

I apologize for not thinking of this as soon as I had the original drawn up. Al Belli must laugh right off his chair at some of the things I post, expecting people to fabricate them ...

L Cottrill

[Jmitchell]

What exactly is the scale on that, last time I had to do it by trial and error and wasted about 50 sheets of paper continuously trying new scale percentages and printing it out and measuring the squares.

[larry cottrill]

What exactly is the scale on that, last time I had to do it by trial and error and wasted about 50 sheets of paper continuously trying new scale percentages and printing it out and measuring the squares.

The scale is [a totally arbitrary] 20 pixels = 1 cm. On the HP printer I normally use at work, printing at 190% would result in almost perfect sizing. I tried printing it at 100% and using the office copier to duplicate it at 190%, and that came out virtually perfect, certainly closer than I can cut and file ...

Hope this is the answer to what you're asking.

L Cottrill

[Jmitchell]

A ha! Perfect!

[larry cottrill]

A ha! Perfect!

Have you had a chance to look over the Fo Mi Chin Re-work thread, and does it seem to communicate everything you need to know to construct the intake?

Remember that the shape of the oval slot in the cone is basically guesswork - I assume you are ready and able to close some long gaps with weld if the need arises! When you get to fitting the intake in there, try to get some photos of the fit along those side seems before you weld them shut, and I'll correct the drawing if it's way off in some regions.

Will you be using your slightly oversize tubing for the tailpipe? If so, the oval slot won't close as tightly together as it would with the standard pipe, so you might want to adjust the slot layout accordingly. It's a lot easier to file / grind it out a little to fit than it is to fill big long gaps with weld!

L Cottrill

[Jmitchell]

I'm a tad confused about the intake, from what I understand so far, you cut the 1.25" pipe in half, pound the end so that it's pointing downward, and cut out a slot of the 1.25" pipe that will cover the bottom of the split pipe half smoothly. Then this whole assembly is welded over the slot?

Is it exactly like this picture?

But with no slot on the tailpipe, right?

I'll be using the 35mm tube, so I'll have to adjust accordingly, as you said.

Does the intake protrude onto the tailpipe section? Can you give an exploded view of the CC and intake?

[larry cottrill]

Note the one major difference between the FMC and FWEIII: In the Fo Mi Chin, the intake piece extends beyond the chamber onto the full-depth part of the tailpipe - on the FWE, it does not!!! The tailpipe must still butt weld onto the end of the cone, aft of the intake flare. What this means is that the large notch cut out of the tailpipe front end will be longer than the intake half-shell. You should be able to see this on the original plan I posted. There will be two little 'slots' between the chamber cone and the long 'tongue' of the tailpipe, right behind the flare. These will need to be closed with weld as a final step.

So, don't get carried away with the detail drawing from Fo Mi Chin - it's OK for the dimensions of the upper part - the intake shell. But the big notch cut out of the tailpipe below the 'tongue' that the shell welds onto will extend farther back into the pipe. I'll try to re-draw the Fo Mi Chin detail tomorrow to work for the FWE, since that will make it clearer!

Sorry if this seems confusing! The facts to consider are that the intake shell ends up in exactly the same relationship to the very front of the chamber, while the tailpipe joins the chamber a lot farther back than on the FMC. The reason for this is that the FWE chamber cone is much longer than the shaving cream can chamber of the Fo Mi Chin engine. So, the 'tongue' protruding forward into the chamber has to be longer, to achieve the larger set-back of the front rim of the tailpipe.

In the FWE, the ENTIRE length of the intake shell will be welded onto the protruding tongue [except for the little overhang at the front end, of course], and there will be two short edges of the tongue remaining that will eventually be welded to rear part of the slot in the cone.

L Cottrill

[Jmitchell]

Ahh I see! so the tailpipe looks like this then?

[Jmitchell]

OK I'm casting a cone form out of some polyester resin, it's hardening as we speak. It should make rolling the cones a lot easier, as I can just wrap the metal around the form and pound/press it into place.

[larry cottrill]

Ahh I see! so the tailpipe looks like this then?

Exactly - now you've got the concept. I think now you can see why I mentioned two little 'gaps' just behind the flare - the oval slot in the cone is there to accommodate the intake shell, but the shell doesn't run the full length of the slot! So, you have one little section on each side where the edge of the slot welds directly to the sides of the tongue! And, since the cone is widening out, it doesn't stay lined up with the tongue [which, after all, is still a cylindrical section]. What I would do for this area is get the intake and tailpipe basically welded in, then locally heat those areas of the slot edge and gently pound them in to line up, then do the finish weld of those zones.

Note also that when you weld the intake shell on both sides, the bottom ends of the flare need to be heated and hammered back in straight - that will help the slot fit around it and also facilitate a neatly welded "straight" seam. This only needs to be a small fraction of an inch, right at the bottom where the shell was split off.

L Cottrill

[Jmitchell]

It's making more and more sense by the minute!

I don't quite understand what you mean about the intake shell flare being heated and pounded back in, but things will probably make more sense once I have more of the parts assembled

Jim

[larry cottrill]

It's making more and more sense by the minute!

I don't quite understand what you mean about the intake shell flare being heated and pounded back in, but things will probably make more sense once I have more of the parts assembled

Jim

Because the shell is split from a flared tube, it has two long "bottom" edges where it welds to the tongue of the tailpipe. At the flare end [rear end] of these edges, the flare turns outward at the "corner" formed between the edge and the flared end. All I'm saying is to bend just the corner back in straight so it isn't hooking outward, but lies tight against the edge of the tongue, like the rest of the shell. This makes it easier to weld to the edge of the tongue, and keeps it from interfering with the edge of the slot in the cone, which would be right up against it if the width of the slot made a perfect fit [ha!].

So, when you split the flared tube to make the intake shell, the end of the shell will be a flare that runs 180 degrees. When you bend the two corners back in, there will be a few degrees less at each end, where it will get welded to the tongue of the pipe. Only the very corner needs to be pulled in, because at that point the cone wall won't be very much larger than the cylinder of the pipe. There will be plenty of flare left around the rest of the intake for good breathing.

L Cottrill