Just made a Advanced Focused Wave Engine cant keep it going

[nickwilson]

I got the prints from Beck Technologies site. It is a advanced focused wave engine 2.25 lbs thrust. I can't keep it going without air and I don't know why. If someone could help me out, I would appreciate it Thanks.

[metiz]

Lets go through the usual suspects:

1 did you flare the intake?
2 did you build acording to specifications, leakfree?
3 are you using a restrictor on your gas tank? aditionally, what kind of gastank are you using? A little camping bottle wont cut it
4 what kind of injector are you using, how far is it in?

[nickwilson]

Yes built it to specs. Only thing thats not perfect is the cone, because I didn't have a roller, but it is very close. Intake is flared to specs. The exhaust flare is not because it wasn't on the diagram. So I made the flare a quarter inch bigger than the exhaust and about a quarter inch out. I'm using a 15 lb propane tank and there is no regulator. I'm using a metal pipe quarter inch id for the injector. There is not a specific spot to put it to keep it going, I've been holding it, trying to figure out a good spot.

[metiz]

do you have a pic of your setup?

[nickwilson]

here are some pics, hope they help

[metiz]

Ok and you're using a 6mm internal injector. How big is it on the outside, 8mm? Is it a straight open pipe or is there a nozzle of some sort on the end like a Rosscojector? how far is it in, what positions have you tried?

I'm thinking it might be injector related. The plans do specify 1/8" inside D injectors.

[nickwilson]

There's not a nozzle at the end of the pipe, it is a straight pipe. Not sure of the o.d. it is probably 8mm. I've tried it from quarter inch outside all the way to the bend of the intake. Center of the intake and all around the inside. Does it make a big difference if I use a 1/8 inch tube?

[metiz]

In a small engine like this it might very well but I'm not sure. I've ran mine on a 1/8" tube back in ye old day. If you have some tubing like that lying around, give that a try

*edit* oh yeah, how are you mounting the injector in the intake? is it fastend to something or are you holding it by hand? is it pointing straight into the intake centered or is it pointing to a wall?

[nickwilson]

ok THANKS Have a good one

[nickwilson]

by hand going to mount it in washers so i can slide it back and forth. it should be centered right?

[larry cottrill]

Nick -

One more thing should be mentioned as a "usual suspect", since you seem to be a beginner: Too much starting air.

This is a funny one, because it seems so counterintuitive: A pulsejet moves a lot of air, so it must need a lot of air to start, right? Wrong. What happens is, if you really blast the air in, you will then open up the propane to get a nice roar, but now this perfectly correct air/fuel mixture is based on EXCESS air (i.e. a lot more air than the engine itself will naturally draw in free running). So, what happens when you take the air away? You are now piping fuel in at a rate far BEYOND what the engine can tolerate to run. This would be especially easy to do with such a large fuel pipe.

I would use a 1/8-inch OD or at most a 3/16-inch OD fuel pipe for this size engine, if the end is just an open spout. THEN, I would try to start with the slightest PUFFS of air from a compressor blowgun several cm (3 or 4 inches) out from the intake flare. Puff 2-3 times per second while gradually increasing the fuel valve from the off position. The air going into the intake (each puff) should be just a light breeze at the intake. That one change may do everything you need to make it run.

It is VERY easy for beginners to "overblow" these small engines while trying to start them. I never succeeded in getting anything to take off and run until I learned to limit the starting air.

Good luck!

L Cottrill

[nickwilson]

would a few small holes make it not run? thereis only two or three. and the intake is slightly tilted twards the exhaust but it is in the wright spot but my conbustion chamber is not perfect. but to me it seems like it would still run if you have anything it would be sweet. i am going to make another one like it. but i wanted to see if i could make it work first PLEASE and THANKS

[nickwilson]

i have seen on differnt plans that the intake tube goes into the combustion chamber mine dose not could that be the prob

[metiz]

different plans, different specs. the Beck tech plans do not specify the intake to enter the cc so it's fine the way you have it i.e: to plans

[nickwilson]

Making a new one. It is going to be an octagon. Haven't started it yet, will have pics soon. Couldn't get the other one going, think the cc was too messed up. I will take more time with this one.