Resizing 55 gallon 200L Drum

Thanks Denis, that really helps me visualize the cam working on the top of the column.

Thanks Pete. I should see how much space below the burner it would take to contain a failed A10.
(elevator music)
So 2.4L or 147 cubic inches would be to the top of a 2.5" (63mm) x 5" (127mm) diameter plinth in a 10" (254mm) bore. I will enclose a pic of this with a 4" (100mm) diameter plinth to gain a little more.
I went after the welding without (cough) practicing first on the coupons.
Fitting and tacking went slow but turned out fine.
The butt weld is probably my worst to date, even with backing material. Not enclosing a pic...
Going to lick my wounds and try with MIG tomorrow, on coupons first, instead of flux cored.

 

I did a 'retrospective' (a buzzword from my latest corporate training session) after I built a new scrap wood saddle/workholder, installed an old inner form to keep the installed bricks from falling out, removed the previous old outer form, and cleaned up the adjacent area for sawdust, wood scraps, and tools.

It looks like my new extension band is forming a 'spout' at the butt weld (8 o'clock). Upon 'retrospection' the circumference of the new piece is about 7/32" (6mm) larger than plan, most likely because I used a thin 18" cork-backed metal ruler to lay out 49+1/32" (1.245m) rather than something like a flexible metal tape clamped at the 10-inch mark to avoid distortions from flexing the ruler or the tape's hook. I am still glad that I added the piece and think I will adopt the tuyere position outlined by Pete that is about 2.5" (63mm) of the floor of the bore. I still need to do the stitch welds where the paint is sanded away (same as tack welds).

 

Not to confuse the issue, but I’ll throw in my 1.5 cents worth. I think keeping the burner a bit off the floor is a good idea so as to maximize combustion time. But you also want it as low as can be without adverse consequences. So, I would put it maybe an inch off ( mine is tangent and my burner is aimed 5 degrees or so toward the top) the floor. Early on I had some pooling issues with a prior furnace. But I found that turning up the atomizing air from 20 to 45 PSI solved pooling which I think originated on the incident wall and was accompanied by coke build up there. Both cleared with better atomization. Increased atomization also seemed to improve heat/melt times. I have surely have found tuning these furnaces to require a lot of thought and guess-and-check testing. It’s worth it though. My fuel consumption and melt times have decreased by better than 40% from early days. Most likely that can be improved yet 5 or 10%.

Denis

 

Denis, I appreciate your thoughts on the tuyere height.
Ran out of energy to keep going on it today.
Here is a graphic of the three positions under consideration, as they would roll out into a flat pattern to wrap the OD for cutting:

 

On my first furnace I made fancy drawings and a mathmatically correct cutout for the tube. But really all the skin is doing is holding the insulation in place. So, I would suggest just cutting it a bit oversize and letting the insulation fill in around the tube or tuyere. Don'tmspend time on making the hole cutting too fussy. Likewise, the position up or down probably only mattrs a little bit. But, myself, I do favor the 1" or lower.

Denis

 

I was thinking more along the lines of 1” as well.

Don’t cut yourself short. Worth 2.5 cents, at least! Lol.

Pete

 

Maybe an even 3 !

 

Played with the cammed lifter mechanism in Fusion360 and Inventor. On my screen it moves back and forth.
@Uglydog thinks we can get the pieces turned as a side project during the upcoming casting event.

 

Yup, that's the idea. Drawing looks very nice. You may want to grind a flat on a fully open cam location so that the lid does not auto-descend. I really like this setup on my furnace. You do also need to be mindful that the undersurface of the lid will be radiating heat very vigorously later in your melt. So, don't let fuel, electrical, or air lines pass in that vicinity. Dry grass could light on fire and green grass will be brown soon. I have timber "outriggers" on my furnace. So, on the lid-open side I covered them with aluminum flashing. I dribble some oil on the mechanism almost every session to keep it working smoothly and with little effort. Heat tends to be hard on the oil---thus the need for oiling each melt. I also use drop-in pucks to make fine height adjustments. It looks like you already drew a puck.

Denis

 

I was thinking more or less the same thing as Denis. The cam, when it's in the fully "open" position, should have a flat spot or be somewhat over center so that the lid wouldn't drop under it's own weight. It's not entirely clear from our drawing if that's the case.

 

Thanks for the tips Denis and Rocco!

Denis, so far I just have a welded cap on the vertical 1.25" sch 40 pipe or 'pole' for the cam to ride. I should be able to place a piece of sheet metal under the swung lid on top of the rolling base to give the ground a fighting chance against the heat. I turned the cart so it would be more stable with the lid open.

Rocco, I did not think about a flat spot at all, I was trying to learn the joints and relationships needed to make it rotate and slide on the screen. The spline for the cam is freehand. I tried one with more of a semi-circular lead-in and it drove the relationship to levitate the cam off contact from the cap on the pole.

 

Looking

Looking at the above drawing, the point of contact the cam makes with the stationary vertical bar is to the right of center of the rotational center (pivot pin). That will cause the lid to want to autoclose unless there is something to prevent the cam rotating. A pin could lock the cam. But I do NOT recommend that as you would then have a two-handed operation. A flat would also prevent autorotation. Do that.

Denis

 

Tops, Your nice drawing of the lift cam got me curious about drawing a "Golden Spiral" which is similar to, but not identical to, a nautilus shell curve.
So, I had to learn some new stuff about drawing parametric curves based on mathmatical functions. It took a while for me to get the brain gears all synched up, but I got there. On mine, when I built it a few years ago, I took the easy way and and just scratched out a curve that looked "good." And often since I had wished the curve were a bit fairer. Here is an approximation of the golden curve any portion of which could be used for the cam.

And here is a link to the Onshape document it was created in.
https://cad.onshape.com/documents/7...renderMode=0&uiState=6441c3e7ec87ad03e2ae8d32

Of course, you will have to "ruin" it by grinding a flat!
FWIW,

Denis

Added: It would have been easier to just use a math formula plotter, but I needed to learn how to do this in Onshape!

 

The Golden Spiral is interesting, spent some time with the Golden Rectangle in school as well:


I understand wanting to figure it out in CAD. I decided to put down the mouse and put on the helmet and gloves to weld and cut on the shell and lid. It doesn't really matter how good I make templates or drawings, my metalworking still has that seemingly kindergarten level of fit and finish that only a ... oh nevermind At least we're getting closer to a crucible of molten metal!

PS The Onshape file looks nice, thanks for adding a link.

 

Part of my reason for drawing this in CAD is that by extruding the shape into a thin solid in CAD I can then print it in PLA and use that form to transfer the line by scribing, tracing, or spray painting onto a surface. And there will be other shapes I will want to make into patterns or templates that may be based on math functions. Once written, it is so easy to scale the drawing with a mouse click... Kinda pays back the upfront cost of making the drawing.

Denis

 

That is so true. CAD often takes longer that napkin sketches and paper drawing for the first round, but revisions are usually faster and work can often be recycled into future drawings. I want to say the main furnace drawing on this thread is north of 50 revisions saved, most which are the small details as we discuss things here and I decide to implement.

How much lift does a person really need on the lid? I thinking I was shooting for about 1" (25mm) over about 135 to 180 degrees. The 'golden' could probably achieve that in closer to 90 degrees depending how I add it onto the cam.

 

An inch clearance isn't bad in my experience. I have a bad habit of making things fit nice and close while I'm building it and then regretting it when it starts to get worn in. Some folks use guy wires on their lids to prevent droop, others don't. I had them on my lid initially but the turn buckles turned out to be zinc alloy and didn't survive their first use. (I had covered the whole furnace with a 55 gallon drum after my firing heat so it would cool down slowly and they got baked). I just took the wires off. It works fine just cantilevered off the pivot mount.
Were I did run into a bit of an issue is in the clearance of the nested pipes comprising the lift mechanism. They had a nice sliding clearance initially but have gotten sticky with use and oxidation. As Denis previously indicated I douse the whole mechanism with PB Blaster with each use to minimize the binding. An additional clearance of 1/32" would have been better.

Pete

 

An inch or 1.5" should be adequate. I do load my crucible as full as I can at the start of a melt. So, I'm often wishing for another inch of lift. SO, I added a stub of pipe to th external lid pipe as an extra lift handle to get the lid up and over the crucible bypassing the cam. The furnace at that point is just getting started, so it is not blasting out heat and you won't burn the glove off your hand. Once the melt is going in earnest, grabbing the handle is uncomfortable.

More and more I am finding that making accurate drawings of even quite simple parts saves time. I recently made a belt-tensioner arm for my muller. It was just a 3" stub of 3" channel bored to hold two 22mm ball bearing assembles that carried a plate that supported an idler pully. But when I started drawing it, started to see some potential interferences due to the internal geometry of the angle iron. Once the drawing wass done, having the hole locations precisely specified made set up and execution simple and, most importantly, error-free. I also then knew for sure the dimensions of the associated parts and did not have to guess and check when I made them.



I agree with Pete that having the nesting pipes be a loose fit is a good idea for the reason he says. That also allows the lid just a bit of freedon to find its bearing on the furnace top.

Denis

 

Back from the Tamarack event with pieces made for the lifting mechanism. The guys totally set me up for success!

Event write up here:

https://forums.thehomefoundry.org/i...marack-minnesota-summer-2023.2498/#post-50191

 

I mocked up a cam using the base image of the Golden Spiral provided by Denis and CNC-routed it from 1/2" (.465" or 11.8mm) plywood.
It has about an inch (2.5cm) lift and does not auto-close when loaded with 20# (9kg) and me leaning on it a bit besides. I am very happy it is working.