Planing for next years speed weekend, (1/2 scale Argus)

Moderator: Mike Everman

erik
Posts: 42
Joined: Thu Apr 01, 2004 7:20 am
Antipspambot question: 0
Location: sweden

Planing for next years speed weekend, (1/2 scale Argus)

Now its time to plan for this winters speed weekend here in sweden. As you may know, last year i did build a kick powered by a 100lbs pulsejet and this year we are planning something bigger.
I was think something like a 1/2 scale Argus mounted on the (modified) ice yacht (iceboat) that weldion, Johansson and their team built for last years race.
I still need to make some drawings but i want to know what you think about the idea.

Link to the ice yacht: http://mobackenracing.se/category/isjakten/

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Planing for next years speed weekend, (1/2 scale Argus)

Hi Erik, Good to hear your back in the running.

Robbert Maddox has "Lil Big Man" that is nearly a half scale. He reports 300-350 pounds thrust from the 40 pound engine. (Although the engine lacks amplitude at lower throttle which is typical for short tailed engines)

Do you still have your engine from last year? I have been looking at high efficiency valve grids in relation to engine dimensions and think a couple of tweaks in the CC and tail could greatly increase the thrust.
The down side would be more difficulty in starting and noise level would increase.

Was Valve Glide ™  0.431 ever applied to that engine?
Attachments
LBMnV1.pdf

erik
Posts: 42
Joined: Thu Apr 01, 2004 7:20 am
Antipspambot question: 0
Location: sweden

Re: Planing for next years speed weekend, (1/2 scale Argus)

Accordingly to WebPilot's calculations with 0.25mm valves i did get 0.455 which is not that fare from 0.431.
"The new dfr computation using these revised parameters, is dfr = 76/167 = 0.455 which differs by +5.59% from the requisite value of 0.431. These valves should still last a while."
viewtopic.php?f=2&t=5717&st=0&sk=t&sd=a&start=45

How close are your dimensions on the "Lil Big Man", because i have been locking on that engine for inspiration?
One thing that i am going to improve from last years engine is to make it much more easy to service, because the old valve head did have over 400! small parts to disassemble when removing the head for inspection and changing the reds.

I still have the engine and kick from last year, but then i would probably make a completely new CC and tail because i did damage the motor during one of the static test runs (it did get sucked into a oval in the transition from CC to tail) It still works fine ofter some reinforcements but i think i lost some thrust there.

I don't think the noise level is a problem (otherwise i wouldn't build a pulse-jet at all ) , but i am not sure if i like to have it much more difficult to start, especially when we are going to start and use it under arctic conditions.

Johansson
Posts: 1161
Joined: Sun Nov 21, 2004 9:42 pm
Antipspambot question: 0
Location: Northern Sweden

Re: Planing for next years speed weekend, (1/2 scale Argus)

I´ve been waiting for this thread to start!

This video of his 350 pound engine is interesting, the heating pattern starts immediately after the transition cone and reaches all the way back to the tailpipe flare.

Why isn´t the CC and TC-cone heated more? Probably has something to do with internal parts in the CC, it would be very interesting to have a peek at his grids.

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Planing for next years speed weekend, (1/2 scale Argus)

Not sure on the length resolutions as they were stripped from the video. I suppose they are within 25mm/(1"), Maddox speaks of the diameters in one video and those mentioned match nicely. All in all they represent close to a 1/2 scaled Argus.

I did a quick scale based on thrust, and Lil Big Man showed up at the 340 lb. mark

Bill Hinote had a good system for keeping his test engines from distorting by welding rings around the exterior.

One downside to tweaking the engine from last year is that the dfr would need to be reworked.

Those heating patterns are interesting.

erik
Posts: 42
Joined: Thu Apr 01, 2004 7:20 am
Antipspambot question: 0
Location: sweden

Re: Planing for next years speed weekend, (1/2 scale Argus)

One thing that i am planning to improve on this engine is the fuel system, so today i did some experimenting with home-made fuel nozzles.
The nozzles are really simple, the pressurised fuel is pushed through a 0.8mm hole and hits the end of a 2mm pin that then creates a fine mist.
(I will try to make a video later.)
The idea is to mount a fuel rail inside the venturi and having holes for the nozzles.
And then let it spray the fuel mist just before the the air enters the venturi.
I also made a short piece of fuel rail just to make sure that everything fits.
PyroJoe: What do you think of building a engine with your dimensions from the video, or do you have any better design up your sleeve?

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Planing for next years speed weekend, (1/2 scale Argus)

Nice work on the injectors.
Rather than just post dimensions I think there is a path to re-create "LBM".
If the dimensions of the Argus are scaled down to have a 12" diameter CC, the CC length is very near 11.36" +/-, which is very close to what i see from the video.

The Argus has a transition angle a little over 9.9 degrees, which looks to be rounded up to 10 degrees in LBM. Also the Argus had a tail diameter of 8.57" which has been increased to 9" diameter in LBM

Length was tricky, but a lil work on the PULSE JET CALCULATOR shows a duct length of approx. 78.27" for a 12" diameter CC to produce 181 lbs of thrust.

The depth of the valve grid, and any internals are left to task.

The tail nozzle is still a mystery, but has a hint of Bruce S. in it.

Fueling this engine would be a considerable task, 170% of your last engine.
Hope to see Webpilot chime in here sometime soon.
Attachments
lbm.pdf

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Re: Planing for next years speed weekend, (1/2 scale Argus)

Hi All

In the Argus there are some aerodynamic flow straighteners mounted just behind the valve grid, do you or Bob have those fitted to your engines? it may cause the heating pattern you see

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

erik
Posts: 42
Joined: Thu Apr 01, 2004 7:20 am
Antipspambot question: 0
Location: sweden

Re: Planing for next years speed weekend, (1/2 scale Argus)

Viv:
I did use use a venturi between combustion the chamber and valve grid but didn't get the same heating pattern, but i could be that he just used thicker material for the combustion chamber? .
http://hv4all.com/pulsejet/ny/CIMG6817% ... rge%29.JPG

PyroJoe :
If i understand correctly, the dimensions of "Lil Big Man" matches a much smaller engine when calculated on the PULSE JET CALCULATOR, the question is if Maddox made some revolutionary design change or if the calculator is inaccurate?
Because i don't think 180Lbs will be enough for me this year.
Yea, i know fueling will be a challenge , if my calculations are correct(?), a 350lbs engine will consume about 500L of fuel per hour, 8.3L/min.

Edit:
Here is a 1500N motor (~340lbs) calculated with the "Pulse Jet Calculator" Excel spreadsheet.
http://hv4all.com/pulsejet/2011/drawing ... lbs%29.PNG

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Planing for next years speed weekend, (1/2 scale Argus)

Well lets take a look at the PJ calculator 181 lbs. engine with a 12" diameter CC, and see what the significant differences are.

First- there is much more CC volume in the 181 engine creating a more stable, easy start engine, but shifts the frequency lower.

Second- the tail diameter of LBM is near 1.5" larger in diameter, increasing the through flow significantly. Especially if one considers the tail diameter as a significant indication of thrust.

Ok, with the given differences is the PJ calculator wrong? Well, not necessarily, remember there is a balance in design. The PJ calculator will probably make a much more stable, forgiving engine that will run with moderately efficient valves, and have a wider (useable) throttle range.

LBM probably represents a high through-flow engine with considerable attention in valve design to run in a narrow band of amplitude. The lack of containment in the CC when using such a large diameter in the tail speek to the care taken in valve/grid design.

All in all, it is a balance on characteristics of engines. Being right or wrong is one of the big problems with looking at designs. So many disputes have been brought forth in the past over different designs. Hopefully there will be a understanding that a design isn't right or wrong, it just has characteristics of that design.

Have included the Caliber method for VPJ (expanded tail length not shown), although it is somewhat apples to oranges in tail diameters. It would probably fit better if the scale was reduced by 98% or base on a 11.75" CC
Attachments
pjc181.pdf

MANOLO
Posts: 149
Joined: Mon Jan 24, 2005 3:19 am
Antipspambot question: 125
Location: CARLET (VALENCIA )SPAIN
Contact:

Re: Planing for next years speed weekend, (1/2 scale Argus)

hello friends fascinating work. I just do not understand how you put the injector
use only 1 injector?
I almost did not write me here because the language is complicated and not always translate some people understand me

Rocket Man
Posts: 144
Joined: Sat Sep 26, 2009 9:59 pm
Antipspambot question: 125

Re: Planing for next years speed weekend, (1/2 scale Argus)

You already have a proven design 180 lb thrust engine that works, build another 180 lb thrust engine.

2 engines will give you 160 lbs of thrust.

3 engines = 540 lbs of thrust.

4 engines = 720 lbs of thrust.

5 engines = 900 lbs of thrust.

Are you old enough to remember the Saturn 5 project. I believe that was Wernher von Braun's idea according to information that I read.

Johansson
Posts: 1161
Joined: Sun Nov 21, 2004 9:42 pm
Antipspambot question: 0
Location: Northern Sweden

Re: Planing for next years speed weekend, (1/2 scale Argus)

I think that Erik is more interested in designing a new larger engine than just copying his old one, he has come up with several design changes that will make this engine both easier to maintain and build along with a much improved fuel system so there would be little fun in repeating old mistakes by building another 100 pounder.

metiz
Posts: 1529
Joined: Fri Apr 21, 2006 6:34 pm
Antipspambot question: 125
Location: Netherlands

Re: Planing for next years speed weekend, (1/2 scale Argus)

I agree fully with Johansson. And this post has nothing to do with me trying to get up to 1000 posts before 2011

But seriously, a single engine is a lot better then multiple smaller ones. Ockhams razor to the rescue.
Quantify the world.

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Re: Planing for next years speed weekend, (1/2 scale Argus)

Hi Erik

As I have stood next too and climbed all over a real Argus while it was still bolted to the V1 can I go out on a limb and ask why half scale and why not build a full scale one? (or the smaller Porch version) how big is this yacht you have lined up? we know a full scale Argus works (and its range;-) and lets face it you do not have to have it running all the time at full throttle, you could run it in a series of short bursts to get the performance you want, the actual available thrust is a fraction of what it makes at flight speed and you wont be going any were near that (I hope;-)

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire