Dang911, thanks for your critique. My responses:
Dang911 wrote:The starting tube was VERY easy to align, it was basically self aligning, all I had to do is eyeball the air tube 13 mm from the start of the small intake centered it horizontally. Then just a 1 second tack weld on the rings that the air tube went through, and it was held it in place just fine!
I knew this shoudn't be difficult - however, I'm still not understanding what you did to keep alignment on the intake centerline while you made the first tack weld. Please explain further.
The simple support wire at the end was almost useless, it supports the top of the exhaust tube, not the bottom. Supplying a simple L bracket that would need to be welded onto the bottom of the exhaust tube, and screwed into the wood base would be quite satisfactory, the flimsy and fussy wire bent support didn't do the job well.
Yes ... that was not the finest thing I've ever designed. It's funny: when I was shaping the 1/16-inch SS (type 308) wire, it seemed so hard and stiff that it should really work well. Then, once the piece was done, I could see that it was going to be pretty easy to distort out of shape. I had a feeling this was trouble, and should have held you off a few more days while I fabricated something better. But, I was already pretty late in getting you your engine, so I let it go ... shouldn't have done that. You're right, a simple sheet steel bracket and a hose clamp would have been a lot better.
The concept of the kit was excellent, and the fabrication was light, with tools everyone should have. The kit was intended that you also have a welder, but unfortunately, it looked like the kit was intended for someone with a very expensive welding setup. Since the metal was so thin, I ended up welding it with a MiG, at 1 amp, yes just one (1) amp!!! This would not be good for a beginner welder, and was difficult for me, although I would consider myself practically a beginner.
To fix the above problem, the kit should be made with thicker material, lets say 1/16". This will make it a true beginners kit. This is what I had the most trouble with, and I would want changed. With thicker metal, it will be easy to weld it with different welding processes, and lower quality welders, for people with only basic skill.
That's a good point - the same thing Eric mentioned to me, privately. Thicker steel would also make for longer life, and (probably) nobody's under any illusion that they're going to fly this engine, anyway.
Probably my number one mistake was not providing a tailpipe tube. This was based on the really stupid assumption that, since antenna mast tubing is available everywhere, it must be the SAME everywhere. Dumb assumption. It would have cost almost nothing to use a little bigger box for shipping and supply the tailpipe with the front end, thus providing a complete kit.
This "kit", in my opinion appeals to the noob. I myself can be the best example. I had fussed on building my first own, and still unsuccessful pulse jet. When I put this pulse jet kit together, and had it running, (its very reliable, starts instantly all the time) I now know more about pulse jets than what this forum could offer, it was that experience that really got me hook. Now in the upcoming days I am ready to fire up my all stainless 55lb lockwood, I can't wait. All of that energy coming from this kit, which helped me gain the fundamentals, and get a working, easily built pulse jet.
As we see on this forum there are many people who see these and are astonished by them, and then set out with millions of questions, only to find out that they are too difficult to build, or they do not have the resources to build it. This is there chance to get a reasonably priced kit, which can get them into pulse jet experimenting!
The real "red flag", though, was when you psyched yourself into thinking you just couldn't weld it. Of course, you recovered admirably after reconsidereing, but that really made me stop and think about the feasability of welded kits. Think of how many beginners could ruin their kit thinking they could weld it and not being able to. I doubt that there is any caveat I could write that could really convince someone NOT to try it if they believed they could just go ahead and hack away at it and get it. At least you knew you might be in trouble - a lot of beginners would never consider that possibility. I can figure out how to take the time to produce the kits - I CAN'T take the time to deal with dozens (hundreds?) of disappointed buyers who thought they could weld their kit and ruined it!
There are a couple of ways around this. I could offer a "shipping plus $10" kind of service for repairing botched kits. However, this sounds like a poor mode of customer service - if your offering a "kit", there is a reasonable expectation on the part of the buyer that they can build it successfully. Otherwise, what's the point of offering it as a kit? A better solution, I think, would be to offer a kit where the tailpipe and starting tube could be slipped on and clamped to make a running engine, with the OPTION of welding "at your own risk", with lots of warnings about the difficulty involved. Maybe that would be acceptable from a marketing perspective - a "no weld" kit that could be optionally welded, at the risk of the purchaser.
Of course, what you've said about thicker material would help this somewhat, but believe me - there are still a lot of people who would ruin it, even with 1/16-inch steel parts.
The price remains the same, $90-$110 would be a good price for this "guaranteed" working pulse jet engine, that is very easy for the beginner to build.
Well, that's better than I expected. But, even at that figure, I would have to be turning them out with a MAXIMUM of three hours of my own labor to feel like I'm getting ahead. If I had good equipment for cutting and forming the chamber cones and jigs for all the welding, I could probably do them in short-run "assembly line" fashion and end up with 2-3 hrs invested in each one. So, it seems doable (unless these actually appeal to thousands
of people, all of whom order immediately - ha ;-).
The last concern is starting up the engine. For this you are right, you need some special equipment. But nothing extraordinary. I haven't tried, but it is probably possible to start this up using a bicycle pump, what do you think? As for the spark, there are many alternatives out there, that are not only reasonably priced, but ready to work right out of the box. I myself built my own sparker unit with a 555 chip and a rectifier mosfet, but that's just me. For fuel I had great success with an "off the shelf" set up. Two of them in fact. One was a 20 PSI regulator to a big turkey fryer ($23) that hooks up to a 20lb propane tank, the other was a small torch ($13), that just had to be disassembled, and reassembled, minus 2 parts (diaphragm, and flow meter). After that I had those small tanks pushing over 80 PSI of propane, even though I only needed about 18 to run the engine, 12 once it was warmed up!
Yes, a propane-powered FWE with the starting air tube is a snap to start, just by following the directions. Fueling is another excellent opportunity for liability problems, however. How many beginners are really qualified to set up a propane rig like you're talking about? Some 10-year-olds could do a good job; some 20-year-olds will burn down their garage, or worse. That part of it is a terrible responsibility. It might only make sense if I sold special propane rigs specifically designed for it - but that only lessens the potential problem; the liability would still be there, in terms of incompetent users.
I still apologize for the delay on pictures of this engine running, please bare with me, I live in an upscale gated neighborhood. I ran this engine once, and got 5 complains from my non tolerant neighbors. When my Parents and I came back into the house and listened to our messages, I took a lot of crap.... Because of this I can only run this engine in remote places. The night pictures and video are what will be the hardest for me to get, I still haven't seen it run at night. This is all top priority on my list, and I should be able to the media by early next week.
No, I don't suppose someone living in an exclusive community expects to be assaulted with pulsejet noise after dark! Good luck.
Oh and as far as the aluminum shielding goes, I didn't have any thick aluminum sheet and didn't bother for foil. I ended up just placing some cut up road sign directly under the combustion chamber. Yes it was too late I had already chard the wood, and it actually caught fire once ...
Well, the shielding doesn't have to be thick. What I showed in the FWE photo posted earlier is almost paper thin - cut easily in a few minutes with big scissors, from a $3 clothes dryer duct from Menards. Aluminum reflects about 97 % of the infrared that hits it, so it really doesn't need to amount to much to get the job done. Even if your board is already charred, it would be a good investment, and is very easy to do.
Thanks, Dang, for your evaluation! Feel free to add more comments any time you happen to think of some. Now, get someplace out in the country and get some photos of the Sveldt Lady in action!