Short Lady Build Log

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sid_raptor
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Re: Short Lady Build Log

Post by sid_raptor » Sun May 18, 2014 9:43 am

A few things left to sort out before i can try to start the engine. One being the propane tank and gas regulators which should arrive on monday (hopefully)... and the other being an ignition system for the spark plug. Since i dont have access to a model t box here, i am going to try to rig something myself. Hopefully i will be ready to test the engine sometime next week and i will post the results here.
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tufty
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Re: Short Lady Build Log

Post by tufty » Sun May 18, 2014 11:21 am

You don't actually *need* a spark box. Or, indeed, a spark plug.

A burning rag, sparkler, blowtorch - in fact, anything that provides an initial ignition source - shoved up the tailpipe will do the trick. The only downside is that they will finish up "downrange" rapidly. Leave your spark plug in place to block the hole, of course.

"Regulator" is a dirty word round these parts, and for good reason.

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Re: Short Lady Build Log

Post by sid_raptor » Mon May 19, 2014 5:31 am

tufty wrote:You don't actually *need* a spark box. Or, indeed, a spark plug.

A burning rag, sparkler, blowtorch - in fact, anything that provides an initial ignition source - shoved up the tailpipe will do the trick. The only downside is that they will finish up "downrange" rapidly. Leave your spark plug in place to block the hole, of course.

"Regulator" is a dirty word round these parts, and for good reason.
Yea, that is my back up plan. If i can't get the spark plug to work, i am probably going to use a lit stick in the tailpipe or something similar.

Whats so dirty about regulator? :P
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Re: Short Lady Build Log

Post by tufty » Mon May 19, 2014 7:54 am

sid_raptor wrote:Whats so dirty about regulator? :P
You don't want one. Although they give you a regulated pressure, they restrict flow.

Your setup should look like this :

Gas bottle -> ball valve -> fuel line -> engine.

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Re: Short Lady Build Log

Post by sid_raptor » Mon May 19, 2014 3:31 pm

Ok so i tried the engine out today...i did not have a ball valve but i plan to get one now because the engine did not sustain.....

I managed to get it growling like an ideling motorcycle engine...then when i increased the fuel i got a few 'barks' and then it would cut the flame. I was using a lighter at the tail pipe to ignite the engine since my spark plug rig wasnt ready. I will post a video of the failure soon so perhaps someone can tell me what i am doing wrong?
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Re: Short Lady Build Log

Post by metiz » Mon May 19, 2014 6:30 pm

That's a clear sign of it needing more gas
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Re: Short Lady Build Log

Post by sid_raptor » Tue May 20, 2014 4:45 pm

Ok I tried again. also this time i held a welding torch at the intake for ignition and the engine started to roar!!! but it does not sustain!!

Once i remove the air supply it cuts out....
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Re: Short Lady Build Log

Post by tufty » Tue May 20, 2014 6:54 pm

1 : Sounds like you need more gas.
2 : You'd probably get closer to running with a movable "stinger" fuel feed (the fabled Rosscojector, see viewtopic.php?t=1902&start=0#p21887).

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Re: Short Lady Build Log

Post by sid_raptor » Wed May 21, 2014 5:12 pm

thanks a lot!! that looks quite intresting! That should be the next logical step for my build.

Although....i did a major floopup and cut my tailpipe too short. And my CC got deformed in the vice. I dont know if its worth trying to salvage or do a complete rebuild from scratch. I am leaning towards the rebuild idea because i would like to get a better finish in the air intake flare. I will keep posting updates of whatever i do here of course.
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Re: Short Lady Build Log

Post by sid_raptor » Wed May 21, 2014 5:54 pm

Oh and here is a video of me trying to run the engine.....My friend was pumping the air while i held the camera and controlled the gas...

https://www.youtube.com/watch?v=Kg1hLbF ... e=youtu.be
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Re: Short Lady Build Log

Post by tufty » Wed May 21, 2014 5:57 pm

sid_raptor wrote:thanks a lot!! that looks quite intresting! That should be the next logical step for my build.

Although....i did a major floopup and cut my tailpipe too short. And my CC got deformed in the vice. I dont know if its worth trying to salvage or do a complete rebuild from scratch. I am leaning towards the rebuild idea because i would like to get a better finish in the air intake flare. I will keep posting updates of whatever i do here of course.
As long as your CC isn't massively deformed, I wouldn't worry about it too much. The tailpipe isn't an issue at all, make up a "sleeve" of tube or, better, rolled sheet to slide over the end of your extra-short-lady's tailpipe, and you can adjust tailpipe length, trombone-style. Get it running like that, once you've got a length that works, then start thinking about rebuilding.

Looking at your video, that's not too far from running.

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Re: Short Lady Build Log

Post by sid_raptor » Thu May 22, 2014 5:41 am

Oh that is an EPIC idea!!!! Sorta like a variable geometry engine! lol

Im going to get on that right away!!!!!!!!!

I knew it was a good idea to join the forum!

Thanks a lot!
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Re: Short Lady Build Log

Post by tufty » Fri May 23, 2014 5:36 pm

I can't take the credit for that. I'm not even sure where it originated, feels like something from Mike Everman, Bruno Ogorolec, Larry Cottrill or maybe Bill Hinote, and probably on the old forums. It's been "common practice" for a while now...

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Re: Short Lady Build Log

Post by sid_raptor » Sat May 24, 2014 4:15 pm

https://www.youtube.com/watch?v=iAAy8rJ ... e=youtu.be

Gave it another try with a slightly better fuel system. I used a tank that gave me better flow and much more control on the pressure. This time i think the engine ran close to 210 hz (based on the sound frequency) but still no self sustain. On Monday i am going to make the trombone slide and see what i get with that.
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Re: Short Lady Build Log

Post by sid_raptor » Mon May 26, 2014 3:32 pm

ok so i tried the trombone arrangement but still no joy :(

but first i think i should give a breakdown of what exactly is going on.

First time i got it to pulse, it barely ran for a few seconds at around 180 hz.
Second time, i managed to get it started and ran at about 200 hz making a lot more noise than before and i can keep it running for as long as i supply air.

My air pressure is around 3 bar and i the first couple of times i could only get the gas upto 50 kpa before it cut out.

With the trombone slide, the engine is able to run with gas at well above 110 kpa before it cuts out. the noise from the engine is also a lot more 'healthy' and is much louder than before.....BUT

The moment i cut the air off the engine dies.......


Now i suspect i might have made a mistake in aligning the intake pipe. i tried to keep it as close to the plans as possible.

Also, i found 2 versions of the intake diagram in the original thread and both had a slightly different diameter of the inlet. Mine is around 20 mm which is about a millimeter larger than the original plans and i think i cant get self sustain because of that. But in the second version of the p;ans (The black CAD drawing), the intake diameter is 21mm. which is the correct diameter to use? i only managed to find a pipe with an inner diameter of 20...if that is the problem, i dont think rebuilding from scratch will solve it....

So my options so far are..
1) Rebuild the engine from scratch
2)Modify the the engine and fit a new intake pipe

But if i can not find the correct diameter, i can try to roll a new one from a sheet....still i need confirmation of the correct diameter.

Also, the trombone slide pipe i made has to be a little larger than the original tailpipe. My current version is only 1-2 mm larger but what kind of tolerances am i looking at here?

Please help!!!!!!!!!

P.S. Can the mods change the title of the thread to ' The trials and tribulations of Sid_Raptor' ? I think that would be far more appropriate :lol:
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