New guy getting started

[GRIM]

Hi CLAY
Heres a drawing that I have on file , I believe it to be of one of the original Lockwood designs ,
There is a calculator type thing somewhere for lockwood style engines , to enable scale up /down, BUT
If I were to attempt one of these , I would give some serious thought to getting in touch with Eric Beck , he will sell you a drawing for a similar, but I believe superior engine , Easier starting ,better efficiency etc ,

Hope this helps

G

[CLAY]

Cool. I might have to do that then.

Much progress tonight! Here we go:
intake pipe flared- that was a lot of fun!

Combustion chamber rolled- these were some ugly welds. It took me a bit to remember thin metal welding technique.

The pipes attached, the cap is formed and welded, but not attached yet. I want to get the spark plug welded on first:

Another view:


If anyone sees any glaring errors please let me know! It seems about right so far. I need to take care of the sparkplug mount yet, then it's on to the igniter setup and firing!

[Ghrey]

Re: regulator

I got mine at a roofing supply store.


Nice progress, Hope to see some run videos soon.


Belated Welcome ,.,

[Graham C. Williams]

... Or could one simply scale up the Short Lady design? I didn't think you could really simply scale up a design, since resonance plays a role and I can't imagine that ratio to size is simply linear.
I have been searching here for about 20 minutes with no large lockwood plan results. Any ideas? Thanks!

Dear Clay.

Correct, you cannot simply scale these motors. This is for many reasons, your thinking is along the right lines.
I have a number of reservations about the Lockwood drawing as shown; it proved difficult to start and not at all fuel efficient. Until Nick modified it we couldn't get it to start at all! Oh yes, the tailpipe is given to heat and pressure induced collapse.
If your friend must have a motor of this power have a word with Eric or James Irvin who will be able to help you.
If you would like to build a motor that's shorter than the 'short Lady' I have a proven FWE based design that gives about 22.3N but requires a high standard of construction? Send me a message if you want to have a go.

Graham.

[larry cottrill]

Clay -

Looks like you're doing fine. The only place on this engine where roughness would be considered critical is the annular weld connecting the tailpipe to the chamber. Of course, I mean roughness on the interior side -- how it looks on the outside is essentially meaningless as long as the welds are sound.

You'll have this one going in no time, and be ready to take on something more challenging.

L Cottrill

[CLAY]

... Or could one simply scale up the Short Lady design? I didn't think you could really simply scale up a design, since resonance plays a role and I can't imagine that ratio to size is simply linear.
I have been searching here for about 20 minutes with no large lockwood plan results. Any ideas? Thanks!

Dear Clay.

Correct, you cannot simply scale these motors. This is for many reasons, your thinking is along the right lines.
I have a number of reservations about the Lockwood drawing as shown; it proved difficult to start and not at all fuel efficient. Until Nick modified it we couldn't get it to start at all! Oh yes, the tailpipe is given to heat and pressure induced collapse.
If your friend must have a motor of this power have a word with Eric or James Irvin who will be able to help you.
If you would like to build a motor that's shorter than the 'short Lady' I have a proven FWE based design that gives about 22.3N but requires a high standard of construction? Send me a message if you want to have a go.

Graham.

Thanks for the info Graham. I'll make sure he doesn't go with that one then- I'll probably have him contact Eric and maybe buy his plans. It's great having this wisdom availible. He's more interested in building a larger design that he could use to power something (like a go cart or a sled- even if it's slow) than a small demonstration model.

Looks like you're doing fine. The only place on this engine where roughness would be considered critical is the annular weld connecting the tailpipe to the chamber. Of course, I mean roughness on the interior side -- how it looks on the outside is essentially meaningless as long as the welds are sound.

You'll have this one going in no time, and be ready to take on something more challenging.

L Cottrill

Thanks Larry- The insides are nice (as opposed to the outside!)- I knew they had to be smooth per the design. This is where a TIG would be nicer than a MIG (which I have). I may reach in and do a bit of grinding/filing in there just to smooth the whole thing a little better, but it looks pretty good so far. Thanks for the help!

[Mike Everman]

Looking good so far, Clay!

[CLAY]

So I tried to start it yesterday. I should be using 1/8 copper line for the fuel line, right? Where do you guys get that? The closest thing I could find is 1/4. I also think I'll have to put in a needle valve to control gas flow- the valve on the tank didn't seem sensitive enough. Also I need a better coil than the spare motorcycle coil I ad- the spark is there, but not big, and I couldn't get it to ignite. I used a propane torch from the thrust tube side, got flame out the back, then added sir to the intake to light, but she wouldn't catch and hold. I could get it to buzz, but as soon as I cut the air it quit.

So, my questions: What cheap (preferably) coil should I b using to get a *big* spark,

Where did you find 1/8 inch copper line (hobby shop?)?

How do I know how much fuel to put in?

Thanks!

[Mike Everman]

Yes, hobby shop. Wherever there's the display with many different tubes and sheets for modeling.
Open up the spark plug as far as you can, even snapping off the electrode will work.
Personally, I use a spark unit from a household gas range, powered with AC. Simplest when AC is available.
Putting a finer valve on there is a plus, as some tank valves are not so fine to adjust, though I've always made do with them.
Let it buzz for a while, like 1-2min for warmup.
See my starting thread in the FAQ's. That buzz isn't anything like running. haa ha, you'll see...

[CLAY]

OK- Thanks Mike. Breakthrough time. I got it to run using the torch in the intake, then I can back away the torch, but it only runs when compressed air is blowing in the intake. I did the warm up- buzzing with air for a minute or two, then I could turn it up and with the compressed air she would *scream*. As soon as the air runs down, she quits. I would assume that means my 1/4 inch copper line is blocking too much air? Or am I giving it too much fuel? Or is it a combination? Thanks!

[Graham C. Williams]

Hi Clay.
You could try this method:

viewtopic.php?f=3&t=2021&start=0&st=0&sk=t&sd=a

Graham.

[CLAY]

Could someone explain the rossco injector? I googled it but only come up with this forum.

[Jutte]

Hi Clay - ah yes ...the world famous and highly technical Rossco Injector - the
high tech solution for hard to start Pulse Jets as used world wide by
Pulse jet Engineers...but wait theres more....LOL !!!
No - really it's simple - just get your metal fuel pipe and cut a 45ish degree
cut across with your cutters etc.( Simple and mondo cool ).
Here is an old picture of one of my really badly beaten up Rossco Injectors.
It really should look a lot better than that but at that stage I think it had been dealt
to by about 4 different Pulse Jets.
Hope that helps.

[CLAY]

Can I assume the 45 deg angle is to try to make it flush with the wall of the combustion chamber? Is it important to make the angle face a certain direction here?

[PyroJoe]

That slight angle Jutte posted, works well. One of the most important features is the narrow opening that is at the cut surface. For the narrow slit I try to visualize it just open enough that the corner of a piece of notebook paper would be a tight fit in there.

Sounds like your close. Try not to let off the air until the combustion chamber starts to glow or is relatively hot. The injector may need to be somewhat deep, nearly to the seam in the intake. May need to increase or decrease the fuel as you back off the air. It is a delicate touch on a tank valve.

As a side note, I have found that Larrys intake fairing is slightly easier to start. Some 3" diameter chambers are much easier to start, but are second class in performance.

Joe