2" shotgun vapor tube spacing

[Chroi]

About to complete my 2" shotgun build I started last night. consists of (7) 1/2" tubes inside a 2".

what a PITA with only hand tools. Made several sets of plates before I got 2 I was willing to use.

First attempt building a shotgun for me. I originally started with a 4 hole design, and ended up with a 7

Now, I'm wondering if I have enough space left for H20 to circulate efficiently? I'll be using city water so pressure and volume are not an issue.

Have I screwed this up? (before I waste a length 2" for the jacket.....)

If the spacing is too tight I'l could always cut the thing in half and make a couple cross flow condensers

(But knowing my luck they wouldnt be tight enough for that application!)

[Bob Loblaw]

Wow - As I read the message, I was wondering how you fit all those in there... I'm in the midst of building a 2"shotgun but using 3/8" tubes to get 7 in. Like you, I was worried about getting enough water volume around the tubes. Looking at that drill pattern, I suspect that the vapor is going to be heating the water more than the water will be cooling the vapor - unless you are pushing water through at a really high gpm rate.

BTW - I think that is also a lot longer than you need to go for a shotgun with that many tubes. Based on other builds and commercial offerings, I was planning 15" for mine. That looks like what, 24"? Probably overkill.

[Chroi]

Overkill is underrated IMHO esp when you jump into projects feeling your way along as you go like I do

I got 20' of L grade 1/2" for free so I wanted to make use of it even tho a thinner walled 3/8's woulda made life much easier

Like I said it's hooked up to a garden hose so flow is as good as it gets without a fire hydrant

[Bob Loblaw]

Free is a good deal, I always say. As long as water is cheap, go for it.

[still_stirrin]

Making a 7 tube (3/8") in a 1 1/2" jacket looked about the same. But dang, is it efficient! I put 1/2 plate baffles throughout the length too so the water would spiral through the HEX. It increases the water turbulance increasing its effectiveness. Overkill, I'm sure. Another way to do essentially the same would be to spiral your tubes as they progress through the jacket.

But stuffing your jacket like that will be fine. Water will find its way through the maze. Where there's a path, it'll get through.

[Chroi]

Another way to do essentially the same would be to spiral your tubes as they progress through the jacket.

I would but then it would be basically a graham and have to be run upright. still a cool design.

i do have all the busted plates I didnt use tho.....could use one in the center to create additional turbulence. hmm.

But stuffing your jacket like that will be fine. Water will find its way through the maze. Where there's a path, it'll get through.

after some cursory experimenting tonight, i completely agree. this thing is gonna have some serious knock down power.

[Scribbler]

Nice work. I'm with you: I like overkill. If I'm going to make something, I want to push my abilities as well as make the most effective project possible.

That being said, I would worry just a little about how much water flow the single tube in the center will see. The water is going to want to take the easiest path possible (meaning those wide channels between tubes).

I think the idea of a few baffles is a good one...

Scribbler

[Brutal]

I think it looks great. I have been considering building something just like that but I was going to run the water through the tubes and let the vapor try to get by around them.

[Scribbler]

This is the sort of baffle setup I am thinking about using (but my condenser will be 12 tubes in a 3" barrel..) on a 16" shotgun, I plan to use 5 baffles, (3 inner flow, and 2 outer flow). This would create 6 gaps, forcing the water to move in between the pipes quite a bit. I also intend to make sure that the combine area of all my baffle holes is slightly less than the area of my water inlet/outlet. (Water inlet is 3/8 ID with an area of 0.11 sq inches. 1/8" bit is an area of .012sqi and a 3/16" bit is .028 square inches. So I would go with three two 3/16" holes and four 1/8" holes for a total of .104 square inches... The coolant will then face a slight restriction which will encourage it to move evenly through the baffle instead of just taking the shortest path possible...

Here is a quickie drawing of how I'm thinking of doing my baffles... (Except for 12 tubes, not the seven I used here...)

[Chroi]

what about scrubbies for baffles?


would putting a valve on the output line to increase the pressure inside the shotgun help at all?

[Scribbler]

The issue isn't just slowing down the water... It needs to be directed as well and this is in proportion to the openings and the ratios involved... Since 100% of the flow will go through the exit spout, resisting it there won't do anything but increase pressure and maybe slow it down a little....

Scrubbies might create some turbulence inside, but I would be scared to go that route because predicting the new flow patterns produced would be way beyond my math skills!! (I'd be worried that I unknowingly created eddies and dead spots of little or no moment...)

"What's the problem?"
"Eddies in the space time continuum..."
"Well... what's he doing in there? Tell him to get out!"

[still_stirrin]

image.jpg

Similar to this....is what I did. The baffles clock their way (I think I have 5 between the ends) through the tube & shell creating a spiral water flow. It is very efficient at heat transfer.

ss

[Scribbler]

Still-stirren: how did you fix them in place? A full solder job?or did you just tack then in one or two places?

[still_stirrin]

The baffles were made just like the end plates only with just 5 holes in them. That left 1/3 of the shell diameter open.

I slid them onto the 7 tubes and positioned them along the run. Then soldered them to the tube bank.

Next, I slid the tube bank into the shell and soldered the tube ends to the shell. I ground the ends down and buffed them up a bit to make them smooth.

Finally, I put the 1 1/2" to 1" reducer on the shell end and soldered it on. I did use some heat sinks so that I wouldn't risk desoldering the tube end plates (C-clamps). It worked great. Good joints with no leaks.

To answer your question, the baffles were soldered only to the tube bank, not the shell. But it fit snug enough. Even if some water were to sneak under the baffle lip, the general flow of water follows the spiral path through the shell.

Does it make sense?

ss

[Scribbler]

Makes sense. Did you solder the baffle all the way around each tube or just sort of "spot tack" it...

... Since you are using it to direct the flow and not actually retain substantial pressure, this is the way I was thinking... No need to do much more than hold it in place...

[Chroi]

Well, she ain't purty, but she works!

(The takeoff end will be covered with a friction fit 2" to 3/4" reducer just to facilitate collection.

This will be my condenser for both a VM and flute build I just began

Didnt end up doing the baffles although I really like the idea. But there's always the next build...



PS- Who the hell named this a shotgun condenser? Someone who's never heard of Richard Gatling??

/endrant

[Halfbaked]

Well, she ain't purty, but she works!

Are you crazy!!!!! It is beautiful!!! Honestly, I had doubts and would not have put that many tubes and was betting that you could not solder it up without leaking. I wrote at least 6 posts telling you this and deleted everyone before I hit send. IF you aren't just proud of it send it to me. I'm proud of it and I didn't make it. I'd say your gatlin would knock down an elephant. You need to be pattin your self on your back (if you can).

[Scribbler]

Nicely done!!!!

[Chroi]

thanks gents! looking forward to seeing how much it can knock down.

halfbaked, the hardest part (after the plates, which really sucked) was hardsoldering the brass hose fittings to the outer pipe, without radiusing AND allowing none of the fitting to protrude into the pipe

Had to use tiny pieces of copper to fill in the massive gaps, then keep them in place while applying flux and heat. Coulda gone with a simpler way to attach the water but I like how easy (and leak free) the connections are this way.

Once the tubes were in the finished plates, soldering it all up was a breeze.

[still_stirrin]

....Who the hell named this a shotgun condenser? Someone who's never heard of Richard Gatling??

+1

The "Gatling condenser" for a 5+ barrel 'shoot um if ya gottum' condenser! History in the making...

[still_stirrin]

Had to use tiny pieces of copper to fill in the massive gaps, then keep them in place while applying flux and heat. Coulda gone with a simpler way to attach the water but I like how easy (and leak free) the connections are this way.

Once the tubes were in the finished plates, soldering it all up was a breeze.

What I did was to take a short piece of 1/2" copper, drill a hole big enough to snugly insert the pipe through the shell wall (5/8" OD on 1/2" copper), and then soldered it in the shell. I was then able to take a file and smooth the inside to the shell ID before sliding the tube bank right through.

I know you've got yours built already, but another reader may use the tips to build theirs. Chroi, have you had the chance to fire it up yet? you'll be amazed at the knockdown power, and how little cooling water you'll need to accomplish it. Great job.

[Chroi]

Well....

I'm disappointed. I suppose thats putting it mildly.

The condenser does not work. At a very modest heat input (maybe 10K BTU's external) with an entire copper scrubby in each tube, and the return water on full blast and ice cold, it pours a combo of condensed distillate and uncondensed vapor out the end. Tried varying which end was the water input/output as well.

Obviously, those who said the spacing was too tight were correct. There is not enough water contacting the vapor tubes. It also wasn't limited to the center tube like I was hoping (would simply seal that or make it part of the cooling jacket somehow). No, the vapor and distillate would alternate between all 7 tubes. No easy fix that I can see. Whether baffles would have fixed this, I'll never know.

Already started thinking about what I can salvage. I think I left enough space between the ends and the water inlets to chop off the end caps, remove the vapor tubes and start all over with a 4 or 5 tube design.

What a crummy night

While my theory might be lacking, at least I know I can build something more complex than I need......sigh....

Back to the garage.

Edit.....cant stop thinking about this. Could possibly drill out the center tube, remove and make water tight? Leaving the center open to coolant flow? Easier fix than chopping the caps? maybe reverse the directions and repurpose into a gigantic crossflow condenser? argh im so pissed.

[Scribbler]

Don't tear anything down yet. Figure out the issue first and the make a plan, the do your mods... Otherwise you are just yanking about in the dark.

How long is your condenser? How much space between water input and water output?

[googe]

How did you tell it was realising vapor?. It wasn't a whitish smoky cloud?.

[Scribbler]

Looking at this pic again:

Starting to think that "yeah, that spacing is too tight"

Without baffles, m guessing that very little water ever touches your interior tube...

Without baffles, a friend of mind suggested 1/8" as the min space between tubes. 1/16" will work if you have baffles forcing the coolant to go into tight spots. Otherwise the water will take the easiest path.


What is your min gap? Less than 1/16?

[Chroi]

Don't tear anything down yet. Figure out the issue first and the make a plan, the do your mods... Otherwise you are just yanking about in the dark.

How long is your condenser? How much space between water input and water output?

Length of water jacket: 25"
Length of vapor tubes: 24"
Distance between water in and water out: 19"

Due to the hand done nature of the plates, in some places the tubes are nearly touching, in others, between an 1/8" and 1/16"

I'm sure the majority of the water is running between the two outer tubes along the outer wall and right back out.

Moving one of the water inputs to the opposite side of the condenser would have been a smart move as opposed to both in a straight line on the same side. Dumb...

[Chroi]

How did you tell it was realising vapor?. It wasn't a whitish smoky cloud?.

Since it was a new piece of equipment, and a condenser at that, I was hovering over it like an nervous hen.

putting my nose near the takeoff, I smelled it long before the vapor started being visible. It was visible in a flashlight, and left condensate on a mirror.

It was definitely not flux or water.

My stomach dropped when I smelled what I knew was uncondensed fores.

[Scribbler]

Yeah, looking at that pick, there seems to be a "path of least resistance" between your in and out points along the outer jacket.

In my opinion, cutting the innermost tube out will not change this... The water is still going to want to take that path.

I know you don't want to hear this, but my gut reaction is to pull it apart (save the solder if you can) and cut new caps for 5 tubes...

Don't feel bad, it was an excellent build, and it WAS an excellent experiment. It yielded positive results: we now know that 7 regular 1/2" plumbing tubes in a 2" pipe doesn't work. You also KNOW that you successfully built it. The problem isn't you, the problem is coolant restriction.

[Chroi]

Yeah, looking at that pick, there seems to be a "path of least resistance" between your in and out points along the outer jacket.

In my opinion, cutting the innermost tube out will not change this... The water is still going to want to take that path.

I know you don't want to hear this, but my gut reaction is to pull it apart (save the solder if you can) and cut new caps for 5 tubes...

Don't feel bad, it was an excellent build, and it WAS an excellent experiment. It yielded positive results: we now know that 7 regular 1/2" plumbing tubes in a 2" pipe doesn't work. You also KNOW that you successfully built it. The problem isn't you, the problem is coolant restriction.

Yup, I completely agree with all of this.

No worries. All I spent was my time, as half the copper was free and the other half salvaged. I have more in silver solder than copper I could turn the whole thing in for scrap and get about $30, almost enough to start over (But im not. this beast WILL live again, minus 2 tubes)

And to be clear, I'm not positive I proved 7 1/2" inside a 2" doesnt work; But I'm positive If you attempt it, make sure it's done on a CNC or some other very precise rig.

EDIT- do you think relocating one of the water inlets would be worth the effort? Although honestly, that would be harder than pulling it apart.

[Scribbler]

Remember to post progress pics of the tear down as well as the rebuild!

For what it's worth, if you've got a good seal on your in and out fittings and don't want to change them, make sure you put some sort of heatsink around them so the DONT come loose during your mods. That kind of shit pisses me off! And once I'm pissed off, I start making OTHER mistakes, and pretty soon what started off as a kick ass project turned into a disappointment.

My other opinion: change out the garden hose connectors! -YES, they are PERFECTLY fine.. They will work, they will work WELL... But they ain't sexy!! A shotgun is like the holy grail of sexy power! A six foot Liebig is like a 1970's muscle car... But a 20" shotgun is like a Lamborghini countache from 2019- sexy and sleek!! The most ultimate thing ever built! Check out "western pipe fitters" for parts options, and your local tool store for thread cutters (tap & dyes) that use national pipe taper. Consider using like a 1/4" NPT for your water in/out.

I guarantee that this wont add anything to the performance of your machine, but it sure is sexy!!

Good luck bro.

Make it live!