problem with Roscco stinger

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pablo
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problem with Roscco stinger

Post by pablo » Sat Jul 09, 2005 5:48 pm

hi everyone

I've been trying to start a linear FWE with this device, but I can only get it to "work" at a low freq, as if it needed more fuel (IMO)
I tried increasing the gap in the tube, but then the "venturi" effect isn't enough to drag the necessary air. Any ideas?, I think it might be that the propane tank has low pressure, despite it is full of liquid,
thanks

Pablo

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re: problem with Roscco stinger

Post by pablo » Sat Jul 09, 2005 5:55 pm

i have another tank, but I should buy a different hose for it, is it worth trying with it?

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re: problem with Roscco stinger

Post by Dave » Sat Jul 09, 2005 7:00 pm

Make sure you don't have a regulator in the line.
They have been known to cause all kinds of problems.
Dave

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re: problem with Roscco stinger

Post by pablo » Sat Jul 09, 2005 7:05 pm

nop, it has no regulator
it's a small 5 kg tank

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re: problem with Roscco stinger

Post by Dave » Sat Jul 09, 2005 7:26 pm

Pablo

Yes, it is possible that the hose is the problem. First thing to check is for a flow limiter / excess flow device. These are typically visible just inside the POL (the connector that goes into the tank) and usually look something like a star washer backed up with a little plastic ball. Other times it is as simple as a very small hole in the POL to limit flow.

Does the tank cool down and sweat, or form ice on the outside, when you try to start the engine? If so, you probably DO have enough pressure and flow. If not, you may have a fuel flow problem.

Additionally, Rossco did indicate that the angle was fairly important. His instructions were to make it about a 40 degree angle.

Dave

PS: Attached are picture of two POL devices. One has an excess flow device and one does not.
Attachments
P1010028.JPG
Without an excess flow device
(757.47 KiB) Downloaded 759 times
P1010027.JPG
With an excess flow device
(766.92 KiB) Downloaded 818 times

pablo
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re: problem with Roscco stinger

Post by pablo » Sat Jul 09, 2005 11:12 pm

as i suspected, the pressure is too low. I attached a syringe with a section of arond 5 cm2, and got around 7 kgf, meaning that the pressure is around only 20 psi!!
btw, i cheked the hose and it didnt had a regulator, anyway thanks for the tip
ill buy a plug for the other tank and try again

thanks again

Pablo

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re: problem with Roscco stinger

Post by Dave » Sun Jul 10, 2005 1:04 am

Poblo

Earlier you said: "I think it might be that the propane tank has low pressure, despite it is full of liquid"

Then later: "the pressure is around only 20 psi!"

Please check the attached link showing the vapor pressure of Propane at various temperatures: http://www.flameengineering.com/Propane_Info.html

As shown on the chart, the vapor pressure of Propane at 70F should be somewhere between 110 and 122PSI. Based on what I would guess to be the temperature where you are at this time of year, now I have another question. Are you sure you are working with Propane? Or, could it be Butane, which has a much lower vapor pressure at the same temperature?

Dave

pablo
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re: problem with Roscco stinger

Post by pablo » Sun Jul 10, 2005 2:31 am

I think it is supposed to be a mix, but I'm not sure about it since I fill it in a store wich sells even beer.
the temperature at this time of the year in the afternoon is around 60-70 F

I'll get a propane fitting for the other tank (this one was never filled in that store) on monday and let you now what happens
if that works I'll turn the other tank upside down, burn all that "propane-butane" in my pseudo pressure jet and never refill it in that store

Pablo

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re: problem with Roscco stinger

Post by mk » Sun Jul 10, 2005 9:49 am

I just had the same trouble with the "Rosscojector" when tweaking with the "M-SP 14c" engine.
A low, warming up resonance mode or an inlet only resonance is set in place. It was definitely felt a lack in fuel flow. Well, I just cannot remember the propane vapore pressure anymore, but larger figures brought better results.

Regarding to restrictors in the fuel line, I think that the "Rosscojector" is the over-restricting part itself, with its ultra small slit. You could just take a fueling assembly that already worked fine to cut out any trouble from this side.

However, the squeeze shape seems to appear as a critical value.
Which material is your "Rosscojector" made out of, Pablo?
I discovered ones made out of copper worked better than ones made out of aluminum -- both 1mm wall thickness --, at least without further ado to the cut.

Did you already try adding a small puff of air?
Might be worth a try, too, when air induction is not happening as purposed. This case seems to be affected by the paragraph above.

I assume you already tried different injector placements, including protrusion length -- x-axis -- changes, angle changes -- not necessarily the cutting angle, but the angle you hold the tube --, off-center placement -- y-axis -- changes, and rotating the stinger along the center line itself for a given x-y position, didn't you?
mk

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re: problem with Roscco stinger

Post by pablo » Sun Jul 10, 2005 8:16 pm

mine is made of copper too, i'm not sure about the wall thickness, but it's a standard gas line.

I tried everyting i could, even different angles.
the problem I have is that the vac cleaner engine I had is dead, so I have no air source.
that's the main reason why I am trying to start the engine with this system, to avoid buying a new one (they ask about 30 USs for a new one!, around 120 pesos!)
I'll try with the other tank tomorrow, and if that doesnt work, I'll buy the new engine. after all I never had a problem starting it that way despite the low pressure. In fact I also want to try ¨natural gas" (net gas) wich is wayyy cheaper

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re: problem with Roscco stinger

Post by mk » Mon Jul 11, 2005 1:29 pm

Did you already try opening up the slit a bit by using pliers? You can adjust the slit quite nicely this way round. Maybe you'll find some time and luck.

Trying larger and smaller copper pipes before buying a new engine seems to be a nice choice, too.

I'm not sure what makes a "Rosscojector" work and what not.
mk

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re: problem with Roscco stinger

Post by pablo » Tue Jul 12, 2005 4:13 am

i tried again this morning with the other tank and still no luck, I increased then decreased the gap and still nothing, I'm getting tired of this, I'll switch to other project for a week to regain some enthusiasm and then get back to this one. (but probably with a new vac cleaner engine)

thanks anyway for the tips.

Pablo

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Re: re: problem with Roscco stinger

Post by mk » Tue Jul 12, 2005 10:59 am

Ben wrote:Try steel brake line tubing. I imagine the width of the slit left depends to a large degree on the metal; something soft and malleable like copper probably smashes really far closed before it cuts.
Aluminom tubing exactly showed this behaviour. I had to further squeeze the slit, to get the suspected "Rosscojector" looking end.

A three milimeter OD copper tube was pinch closed almost 100%-ly. There was no gas flow noticed at all, even at max. vapore over-pressure of about 6 bar.
I had to oben the slit by cross-squeezing the outlet with pliers.

But I still have not been able to operate an engine on a "Rosscojector". Weird.

A simple "fuel probe" flowjector worked similar and partially even better.
mk

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re: problem with Roscco stinger

Post by Rossco » Tue Jan 31, 2006 8:56 am

How the hell didnt i see/remember this before!
Ive tried every single posible way to get my linear FWE (built for Camerondownunder88, thanx Eric) to start with the "rosscojector"! No go.

This injector will not run this engine!

And ive been thinking all this time that it would start and run any linear engine.
I still maintain that it will with most, although the accoustics have to be spot on... and im finding that there is a couple of different modes that will not be kicked into gear by the above mentioned low resonance/rumble.

But, this engine wont even operate with it as a fuel feed with added air! Odd!


I found this reference in looking for a sound/video file of the engine. Eric, you got a good one?

Rossco
Big, fast, broke, fix it, bigger, better, faster...
[url=callto://aussierossco]Image[/url]

Rossco
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re: problem with Roscco stinger

Post by Rossco » Tue Jan 31, 2006 8:56 am

How the hell didnt i see/remember this before!
Ive tried every single posible way to get my linear FWE (built for Camerondownunder88, thanx Eric) to start with the "rosscojector"! No go.

This injector will not run this engine!

And ive been thinking all this time that it would start and run any linear engine.
I still maintain that it will with most, although the accoustics have to be spot on... and im finding that there is a couple of different modes that will not be kicked into gear by the above mentioned low resonance/rumble.

But, this engine wont even operate with it as a fuel feed with added air! Odd!


I found this reference in looking for a sound/video file of the engine. Eric, you got a good one?

Rossco
Big, fast, broke, fix it, bigger, better, faster...
[url=callto://aussierossco]Image[/url]

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