Gold rush and the reverse flow plate

[handymanstan]

I have been reading and reading on RF and all the builds here and dreaming.  This may sound funny but I was watching Gold Rush the other day and they were talking about a sluice box and how it works to remove the gold.  I thought if you turned the box up side down and turned it around the technology of it would work in reverse for a reverse flow plate.  So by starting at the fire box side if you had strips or fins of steel welded down under the plate then the heat should create a cyclone effect in front of each fin.  Instead of the gold dropping into the box this way the heat would rise and get trapped I would think that if you started with 1/8x1/2 for the first couple rows the heat would travel fast then go to 1/8x3/4 for a few more rows then 1/8x1 there the heat would be moving slower because of more surface area then keep going lower with each few rows to the end. 

smoke 050.jpg

• handymanstan
• Nov 2, 2012

Picture just to get a idea of what I mean.  picture not to scale

I am not an expert or even close but when the show explained the sluice box technology I thought it would be worth thinking about.   I don’t know how far apart they should be so as to get the most cyclone action but I might try this.

.  What do you guys think?

 

[daveomak]

Stan, evening and welcome to the forum..... Sounds like an idea worth contemplating... However, those fins will create friction and reduce air flow....  compensating for that friction will require increasing the area under the RF plate to obtain adequate air flow for heat/smoke to travel to the cooking grate and stack...  Dave

 

[goinforbroke]

Reminds me of a reverse flow plate idea I had recently...  this is a thermodynamics idea mostly... 

the plate extends into the chamber like the usual, but the thrust here is that the fins are oriented in the opposite direction than what you've drawn.  They instead run in the longitude..  in essence, creating a heatsink which I gather is what you're trying to achieve here. Since they run long ways, airflow isn't impeded, and maximum surface contact occurs.  

sidenote in metallurgy, the reverse plate is made of aluminum for better heat exchange, being coupled to the firebox end of things.  might get expensive, but most good science is!  

 

[handymanstan]

Thanks Dave for the input.  I know my drawing is way out of scale but I am thinking that in my SNP i will only need about 32" of plate and the first 4'' or so I wont need anything then a strip 1/2'' tall then 2'' down the plate another strip same size then every 2'' a strip increasing by a 1/4'' every other one.  This should give me a 2'' strip at the end of the plate.  I think I will still have enough clearance to get a good draft.  I think that in the area between the fins will start rolling with the main amount of heat flowing just under the fins as the heat cools  from the plate it will fall in to the heat stream and be reheated.  Adding the extra surface area of each fin should help keeping the plate even in temp as there are no fins on the hot end and bigger fins on the cold end,  Thanks for looking my wife says I think to much.  LOL
 

 

[ribwizzard]

I believe just the flat plate normally used would distribute the heat more evenly.  The first fin on this concept would actually cause heat build up at the beginning of the plate, and I dont believe the airflow would be anything like what your hoping it would do. Any where the path of air meets resistance, it will create a hot spot.  Better to let the air have a smooth unrestricted path under that plate is my advice.

 

[handymanstan]

I believe just the flat plate normally used would distribute the heat more evenly.  The first fin on this concept would actually cause heat build up at the beginning of the plate, and I don't believe the airflow would be anything like what your hoping it would do. Any where the path of air meets resistance, it will create a hot spot.  Better to let the air have a smooth unrestricted path under that plate is my advice.

Thanks Ribwizzard your builds are amazing.  I have not used a RF but reading on here it seems the plate can have a big difference from the hot side to the other side.  So by adding and increasing  the Resistance and surface area on the bottom of the plate I thought it would even out the temp of the plate.  I do consider you a expert and I am listening.  I got some cardboard and am making a template.  I will start with just the plate and when I can get it put in I will try test runs then add a few fins and try again.  I will post pics

 

[jarjarchef]

I am courious to see where this goes.

By no means an expert, but love to see things tested and new things tried. The only way to find something new is to think out of the box. Sometimes you find gold and sometimes you find yellow rocks........

 

[JckDanls 07]

yup.. sometimes your the bug.. sometimes your the windshield.. be interesting to see where this goes...

 

[rib tickler]

Yes, this is an issue I've also been quarreling with conceptually, before my build. I agree for the most part with GoinforBroke, and though difficult, I came up with a design concept for the underside of the RF Plate/Drip Pan. Following the principle theories behind thermodynamics, coupled with the principles of forced air and aero dynamics; I believe the design of the plate may have the most effect if the underside is lightly ribbed and fins running perpendicular in the opposite direction of airflow, much like shark fins. The ribs help to create a light cyclonic effect when spaced about 11/2 in. apart and the fins (spaced 2 to 21/2 in. apart) helps to maintain and direct airflow. Now not only this, but also if possible, make the plate of cast iron, if not; pair the steel plate (3/8 in. Thick, my preference!) with an 1/8 in. thick sheet of copper, to promote even heating of the steel. What do you all think? Ideas? Comments? Mods?

Mind you, I will be replying to this post soon with a detailed diagram of the plate.

 

[ribwizzard]

Well, to be honest, even heating of the reverse flow plate has not been much of an issue. My cookers all hold remarkably even temp through out the cook chamber.

I believe that any disturbance you place on the bottom of the reverse flow plate will trap and hold heat there.  Adding more fins, ribs , or whatever to try to distribute that heat evenly , will only trap more heat into the reverse flow plate, causing the plate to be hotter than the rest of the cooking chamber. So now you would end up with temperature irregularities from top to bottom.

Now, with that said, on builds where the top of the firebox is either the same plate or attached at the same level as the reverse flow plate. I recommend installing an additional plate under the top of the firebox, about 1/2" down from the top of the firebox. This makes a huge difference on that reverse flow plate, and maybe why I dont have those temperature issues.

 

[fwismoker]

I'd love to see where this goes as well but the space between the fins would need to be narrower towards the FB  getting more widely spaced as it goes. 

 

[handymanstan]

I am still planing on trying this but with winter here the shop is real busy and to cold out to play with it.  Come spring for sure. We already cut the plate and have made some of the fins and plan to tack a few on and fire it up and see what happens then pull the plate and add or change and try again.  I told my friend Kevin that this will only take a afternoon and a case of beer so hes up for it. I will update when we do it.

Rib Ticker,   I would like to see your plans.

Ribwizzard ,  I wish I could build a smoker like you but I have to work with what I got and I might be all washed up on this.  Although with the case of beer to find out it will be fun.

The second plate under the RF plate is something else I will try and play with. How far under the plate do you go with that?

Stan

 

[ribwizzard]

Im only leaving 1/4" on the mini builds, but I put just 1/2" gap on #19.  I'm really not sure if I have explained my reasoning very well, but trust me, it makes a big difference. It basicly is a sheild between the top of the flames in the firebox and the top of the firebox that is usually an extention of the reverse flow plate. This sheild will keep the firebox end of the reverse flow plate from getting hotter than the rest of the plate.  On builds where the firebox is seperate from the cooking chamber and attached with tubing, it does not need this. But on build that have the firebox 1/3 under the cooking chamber ( highly recomended on large pits ) its very important.  I usually like to build my fireboxes a little taller than most builders anyway, then after the box is complete, I cut a piece of 1/4' plate to fit  and just stich weld it in and leave about a 1/2 gap between it and the top of my firebox.   Im sure that there are other ways to create this same effect, but I like my smokers to look uniform and I like the top of my firebox to be level with the reverse flow plate.  Also, like I mentioned, part of me believes this adds a cetain amount of insulation effect to the top of the firebox, but to what degree, I have not tested that theory ( all four smokers I currently have have the plate installed ) but it does seem like I use less wood that on my older cookers.

Ive expressed my opinion about fins on the reverse flow plate, but to be honest , Im am interested in seeing how it works. I am very opinionated, and have been known to be wrong before, maybe this will be another one of those times.

id like to thank everyone here for being a builder and thanks for the comunication and fun.