Electric SS Hospital Cart Smoker Built (W/ PID)...Updated

Well on your way! Looks good so far

Brett, evening.....   I see what may be a couple of problems....  first, the heat shield will direct heat to the side of the smoker... I could overheat and warp.....   Second, the venturi and orifice are inside the smoker....  the flame could consume all the oxygen inside the smoker, then the flame would go out, and you would have a very large propane bomb.... the venturi end of the burner needs to be outside the smoker..... also, the burner seems a little large for that small area....  

When using propane, you need good air flow inside the smoker....

The SS box is a cool unit for a smoker.... Nice find.....   Dave  

Brett,

I'm with Dave on this one (Great Dave's think alike!).  I don't really like that burner and the heat shield "as is".  I've never been a great fan of propane smokers as usually the flame is turned way down to get the low temps, and there is that "propane bomb" situation if it goes out.

In addition to "wicking" heat to the side I think one side of your racks will be hotter than the rest.  I would like to see some sort of a central burner in the middle with a angled heat shield (think roof top) but open on all sides around the burner.  I would also put a second sheet as a real heat shield as any meat fat dripping on the one you have now or the angled one I'm talking about would immedieately ignite into flames (the metal is directly over the flame and would be very hot.  If you have a 2nd sheet of metal spaced say 1" above that with an air gap between them, it will prevent this.

Also since it's a single walled body it is going to be hard to hold temps "as is".  And as is, if you are smoking at 225* the body of the smoker will also be 225* which could be "fun" (once anyway).  I would think about adding at least 1" of roxul or similar insulation (high heat resistant insulation especially with the flame like it is and the small box size).  You could skin it in either aluminum or stainless on the inside of the box and probably use the spot welded in shelf brackets to mount the skin on. Do you know anyone who does sheet metal fabrication?  Probably worth the cost to have them make you a 5 sided box that would fit.  That's such a nice shell, might as well keep it pro looking.

Actually the more I look at this photo, I think you could use a 3 sided bend of sheet metal to form the top, bottom and back.  On the back edges you could leave some tabs that would bend over and rivet to the shelf rack that's already in there.  Then make each side a flat piece with tabs on the back that bend and rivet to the back insert. Use the solid blind rivets (no air hole all the way through when the stem seperates).  If you set the sides back from the surface of the rack supports you could probably still us the rack support slots as is.  The tabs would be in between the slots.  You would need to seal the joints between the panels though.  That would be the advantage of the 5 sided insert and new shelf racks as you could have it made as a sealed interior box when it's fabricated.  Does this make sense?

Also you could leave the bottom uninsulated and put two sheets of the 1/4" thick hardi-board in the bottom both as thermal mass and a fire shield.  If you insulate it the bottom sheet metal will need some x-bracing across the bottom to support the new bottom.

Just a few thoughts, I'm sure it can be refined before cutting anything.

Yep, if you are hitting those temps at the exhaust port there is a REAL problem!

If you go with a interior skin over the insulation you could use aluminum instead of stainless to reduce costs.  That would let you use thicker material too so you could attach your food rack supports to the left and right side by riveting or through bolting (or welding the aluminum if you still have the right equipment available).

If you are going to upgrade the burner and stay with LP, Northern Tool has a $39.95 model that has three valves that control different parts of the burner for real tight flame control.  There are several builds on the forum that use this burner but they are in full size units more like Frank.  Maximum output is 35,000 btu. Pops used one in his cabinet if my memory is correct.  And I'm pretty sure he can dial it low enough to do cured sausage smokes in steps up to 150*.

http://www.northerntool.com/shop/tools/product_15490_15490


I would still try to mount it in the center with an air intake directly below it (perhaps with a rotating vent damper with a stem out the side or front for adjustment of the air flow.   Heck, with that size burner you could just cut a 10" hole in the bottom and probably still hold temps.  My main concern would be avoiding oxygen starvation and having that flame go out.

I also would not even mess with a chip pan and just use that pellet tube.  You already have it on hand and it's a proven performer in this type smoker, plus the smoke will be more even and last longer than chips in a pan. And I would still like to see a double layer of metal above this to prevent drippings catching fire.

I think if I was going with a LP burner, I would just mount a 12" square steel plate a few inches above the burner as a heat plate and thermal mass.  Then use the lowest rack a inch or two over that to be a dedicated drip/water pan rack for hot smokes.  That setup would work like a Holland Grill does and prevent any drips from flaring into a fire.  Just use a disposable aluminum drip pan and toss it after a smoke.  That way you could still use that lower rack for cold smoking when you don't have the burner lit.  I forgot to label the plate in the drawing but it's there.  I would go 1/4" or 3/8" thick and hit with with 2,000* flat black header paint. It's going to rust otherwise from the moisture that is generated by burning LP.  Just make some simple 90* brackets to hold the 4 corners up above the burner.  The one in my Holland grill would glow red hot in use, but I never had a drip flare up while I owned that grill.

Also you could use aluminum channel instead of angle and that would give some tip protection to keep your racks from tipping when pulled forward. Or just mount another small piece of angle above the racks at the front to act as tip prevention.

Something like this perhaps?


Just mount the pellet tube to the side of the burner since it will be well below the flames.  Just make sure the drip pan or something covers the tube to prevent it from being dripped on and extinguished or flaring up.

Looks like "Son of the Electric Franken Smoker AKA/ Frank Jr." is about to be ALIVE!!!!!!!

Since you are going electric, no reason not use just plain old fiberglass insulation from the home improvement store (bare insulation, unfaced).   It should work fine since electric will not be quite as "flame on" as the LP version would have potentially been. 

Are you going to buy a Auberins ready to run 1,800 watt controller or roll your own from parts?  (Not sure what those two panels were, but I bet there is a temp control unit in there somewhere).

Ain't cheap, but this one is pre-made and ready to go for $215.  One probe for the pit and another for the meat all in one neat box and handles up to 1,800 watts of load.

http://www.auberins.com/index.php?main_page=product_info&cPath=8&products_id=203


Since we all know you are like a mad scientist type (keeping in role with the Frankensmoker motif), I would buy the PID module, and pick up some temp probes and a 20-25amp SSR relay with heat sink on Ebay.  Probably get the parts for around $100.

And Plan "C" is figure out what all those circuit cards in those two other panels the U.S. Guberment gave you are for.  I bet one of those has temp control in it. Then try and scavenge and re-task it.

If you have some mechanical relays up to the task of switching 20 amps, you could use them, but SSR (Solid State Relays) are better with no moving parts.  The constant "click, click, click" of a mechanical relay in a process control module will eventually cause a mechanical relay to fail (could fail open or could fail closed and start a fire).  That would be the drawback to a recycled mechanical relay for $5 on ebay.

Take a look at this web page on the Auberins site.  The page is for the box, but scroll down and look at the photos of what they show can be put in the box (which already has the cutouts).  That would work but it uses a mechanical contactor (relay) instead of a SSR.  Relay is cheap though and rated for 30 amps which would be more than a 120v circuit would ever output.  Take the rubber feet off and just screw it to the top of Frankie Jr and there 'ya go....

Items on the back plate are a BNC connector for temp probe, 120v PC type power socket for power in, and a single female 120v outlet for power to the element.  You could just drill round holes for cords and use grommets to protect the cords since it will be hard mounted to the smoker. Or if you want a clean look, drill hole for the power to the element and the K probe in the bottom of the box and run it on the outside edge of the insulation in the smoker (use high temp wire).  Then mount the BNC on the inside of the smoker.  You would have a 12 gage SJ wire coming out the back through a grommet with a 120v plug on the end to plug the whole thing in.   I would probably add an appropriately sized push to reset circuit breaker to the box also.  Actually might add two. One for the main power and a 1 or 2 amp one for the power takeoff to the PID to protect it.

http://www.auberins.com/index.php?main_page=product_info&cPath=7_34&products_id=262

Brett,

Check out this search list on Ebay.  Lots of PID controller kits in the mid $30 range (most with relay and temp probe, some with relay & ssr but no temp probe).  Most are buy it now and a lot have free shipping.

http://www.ebay.com/sch/i.html?_trk...pid+temperature+controller&_sacat=0&_from=R40

You do know you will end up drilling those rivets out and installing insulation at some point.  Look on e-bay for Roxul batts. You can get a box of 6 pieces of 2'x4'x2" shipped for around $60-70.  It it's too thick, just split them into thinner pieces to fit.

On a side note I fiddled around with my warmer cabinet today.  Found out why the element is not heating.  The school I bought it from had it disconnected but then reassembled the cabinet for some reason.  I did not have my meter with me so I don't know if the element is open or just has high resistance (slowly dying).  Good news is it looks like a standard finned element so once I pull it I should be able to find a replacement at a decent price.  I need to lay the cabinet on it's side to work on that though and I was by myself.  Cabinet is rated at 16.8 amps and lists a 20amp breaker recommendation so it's probably a 1,500 watt element (with the rest going to the 3 fans & interior light).  I'll see what the marking are when I pull it.