7" Core with TripWire/P-Channel/KickTail - Design

[Robert]

So few moments later and i have completed the feed tube with the channel and a cooling system...





please comment on that if there are other flaws on this

[Robert]

and a kick tail... this one still needs more explanation

[peterberg]

Jan 13, 2014 19:48:41 GMT -8 Robert said:

and a kick tail... this one still needs more explanation

OK then, I'll try...
To date, the sloped rear side of the burn tunnel is called the back sweep. The small back curved top end of the back sweep is called the kick tail. See second picture.



This is what I thought up: the right angled corner of the standard J-tube is inducing the much needed turbulence but also quite a lot of drag. The gases won't go straight horizontal to the sharp corner and from there at right angles to vertical. Instead, those gases do take a trajectory much like the shape of the back sweep, ignoring the corner largely. At the same time the width of the tunnel at that spot is a great deal wider than the rest of the burn tunnel or riser. As a result, there's a slight under pressure present in that corner and a lot of turbulence. Under pressure in corners also create drag so only part of this is ticked as positive effect.



In order to keep the turbulence and eliminate most of the drag I shaped the transition to what I thought the ideal trajectory could be. The kick tail is there to concentrate the flame at the heart of the vertical channel, in an attempt to reduce the annoying hot spot at the back of the heat riser. As such, it's functioning like a second trip wire, inducing its own small turbulent area. The back sweep introduced another effect: fly ash which tend to accumulate in that rear corner before, is blowing away now. Seeing the heap of dust at the back of the tunnel actually made me think this could be done differently.
It's quite difficult to implement this shape in bricks, I've made an attempt once and it took me a day of very messy and dusty work, trip wire including. Maybe fireclay and perlite make a better choice of materials for this shapes.

[peterberg]

Jan 13, 2014 19:46:36 GMT -8 Robert said:

So few moments later and i have completed the feed tube with the channel and a cooling system...
please comment on that if there are other flaws on this

Yes there is a flaw, maybe two. The secondary inlet look too small, it should be at least the same csa as the p-channel but preferably a bit larger. And it's too close to the feed, maybe you could situate this further away or as a slit or segment, it's not necessary to implement it as a round hole. But for the rest of it, you've got the right picture: this is exactly the type of construction I've been using to actively cool the top end of the feed.

[Robert]

It's quite difficult to implement this shape in bricks, I've made an attempt once and it took me a day of very messy and dusty work, trip wire including. Maybe fireclay and perlite make a better choice of materials for this shapes.

Lets imagine that we would like to keep it veeery simple and use just the bricks and simple cutting. If we cannot make a perfect rounded shape of the back sweep and we would just place the triangle shape made of a brick is that making sense?

if will this shape help a little bit with the negative drag effect you are describing:



or it is better not to do it at all?

[patamos]

Thanks you Peter and Robert for sharing this info.  It is very timely as i prepare to build my core.
Getting into the details of brick layout, am i correct in assuming that 7" system makes for easier assembly with 4.5"x2.5"x9" bricks?  Or is there another rationale for this size?



This flue/bell will have about 38' ISA.  Do you think the gasses from a 7" square riser will condense enough to flow through a 6" exhaust flue after the bell?  The vertical flue after that will be 20' from ground to chimney cap.

(Sorry for going off topic with this thread.  I only just noticed the second page of discussion.  Robert, perhaps the lowest brick at the back of the heat riser could be set back so that the top of the triangular brick is set back too.  This could create the trip wire effect without too much cutting...) 

many thanks

pat

Attachments:

[Robert]

Jan 14, 2014 9:54:22 GMT -8 patamos said:

Thanks you Peter and Robert for sharing this info.

All credits goes to Peter. He is the source of the knowledge i am just trying to make images, to be sure that i understand his technical language:)

Getting into the details of brick layout, am i correct in assuming that 7" system makes for easier assembly with 4.5"x2.5"x9" bricks? Or is there another rationale for this size?

i am not good in US system of measuring ;(
7" is 18cm diameter of the heat riser i am usually using in my projects... never build the 8incher before:) we do not have 20cm pipes easilly accesible )anyway now we speak in therms of the bells more often... but again... the standard size of our modern chimneys is also 18cm... so i stick to that dimensions according to the constant CSA rule

This flue/bell will have about 38' ISA. Do you think the gasses from a 7" square riser will condense enough to flow through a 6" exhaust flue after the bell? The vertical flue after that will be 20' from ground to chimney cap.

i am not sure where is the totall area of your flue/bell... but what i am seeing from the picture it looks quite big for me... and also if you use 7inch riser than the exhaust flue also should be the same size... that would be safer...

but as i said difficult for me to read US measures.

anyway keep updating your build, but here please let us focus on the Trip Wire technology
i am sure that you getting lot of help from gusy here on your thread. even i am following you, and recntly send you picture of one similar build.

i am very interested in your design... looks like you are doing great job.

Robert, perhaps the lowest brick at the back of the heat riser could be set back so that the top of the triangular brick is set back too. This could create the trip wire effect without too much cutting...)

interesting idea, i will try to implement it in teh design... i am wondering what Peter will think about, he knows the science, i am just making pictures

[peterberg]

I think it's possible to have the back sweep as a 45 degrees brick, set back a bit and have a small 45 degree ridge above it as the kick tail. It's a rather coarse implementation but I think this could work.

[patamos]

Yes, happy to focus on this topic here. Apologies again for hopping topic.

So to refine the implementation we will need to carve a concave curve into the 45 face of the triangular brick. Grinder with a masonry disc most likely. Important to stabilize the brick firmly and have both hands on the grinder as it likes to dance around. Big dust cloud for sure...

well being

pat

[patamos]

Hi Peter and Robert,

I am approaching a final decision about how i will build my heat riser. Thinking about casting a circular 6" to sit on top of a square 6" burn chamber. If i snug the riser forward and round the back corners of the burn chamber (probably with sodium silicate, perlite and clay) i might be able to effect the back sweep and kick tail effects. Peter, have you had any experiences with this approach from which you have drawn solid conclusions?

well being

pat

[Robert]

Hey Patamos. I am not sure wheter the clay-perlite -silicate mix for the back sweep will be strong enough to take the heat. But it is a worth to try. Than you can make a nice shape

I will be gone for a while. I am going to Belgium to build one stove with Joris Yuhhhu!!!
When back i will continue to work on a design.

cheers.

[independentenergy]

Thanks Robert for asking Peter to these things, I am developing a similar system and are very useful.Thanks also to Peter for the information

[misterkel]

Can anyone PLEASE link me (and place links) when referring to things like p-channels and trip-wires - for the basic design info? It would make the forum so much more useful for people learning about these things.
Can anyone do an easy cut-n-paste post with links to detailed plans for various design innovations?
Sorry to be a bother, but I search for these things in the forum and just find super lengthy lists with no way to know what is useful or not.

Also - how to view a skp file?

thanks, Kelly

[Robert]

Misterkel, this is what i am trying to do in this thread... to gather the information about the J-tube design with trip wire/p-channel/backsweep and kicktail integrated...

to view the SKP files ou need to get the wonderfull software called Google SKETCHUP.

i hope that the Design i am placing in this thread and the descriptions from its inventor Peter van Den Berg will help the others to implement it in their J-Tube rockets.

[2tranceform]

Jan 25, 2014 11:29:17 GMT -8 misterkel said:

Can anyone PLEASE link me (and place links) when referring to things like p-channels and trip-wires - for the basic design info? It would make the forum so much more useful for people learning about these things.
Can anyone do an easy cut-n-paste post with links to detailed plans for various design innovations?
Sorry to be a bother, but I search for these things in the forum and just find super lengthy lists with no way to know what is useful or not.

Here is the basic definition....donkey32.proboards.com/thread/732/glossary-terms