VegOilGuy

HOW TO MAKE AN ELECTRIC METAL FOUNDRY (Part 2)

Easy build High Temperature Indoor Electric Home Made Metal Foundry for Metal Casting

It was around this point in the build that I noticed the mortar had a significant strengthening effect on the bricks. In this scrap test piece, you can see how easy it is to damage untreated bricks. But those with even a very thin coating of mortar were much stronger. (See the accompanying video here).

This made me rethink the top which was likely to receive some wear and tear.

I removed the top frame, added water to some mortar to the consistency of runny paint, grabbed a brush and painted the top. I was so pleased with this that I extended down a couple of rows inside the foundry, making sure I didn’t accidentally coat any coils. I added two coats in total and let this dry for a couple of days.

I still had 4 bricks left and I decided to bond three on edge to make a thick lid. Here’s two of them and you can see I’ve recessed out an inch square at each end. This will accept some 1 inch square steel later on. I bonded these with mortar and left them 24 hours for good measure.

The following day I stretched more thin polythene across the top and then pushed home the metal frame. I scraped a thin coating of mortar across the bottom of the three lid bricks and then positioned this nice and centrally. These comfortably covered the main chamber of the foundry.

As I looked at this, I looked at my collection of off-cuts and began to ponder. The off-cuts were perfectly shaped to retain the hexagonal pattern so I couldn’t resist bonding some on. And I kind of got carried away with this… I guess I was having too much fun.  

It looks a bit of a crazy mess but the idea is to add more insulation and integrity to the lid. In bricklayer fashion I tried to stagger joins to add strength then I added a thin paint coat of mortar – and added two more slices of a brick finishing off my supply of 30.

Okay the finished look is a little unorthodox and any comments about it looking like a face will be ignored by me and my mate Dave the Lid. Because of how much brick laying is involved in the lid, I left it a good week before touching it again.

When I was happy the lid had had long enough to dry, I pushed through some lengths of box steel. At the end of these I’d already drilled a 10mm hole. Rather than try to calculate exact length, I slid some overly long lengths of box steel onto some threaded rod. Some simple maths told me that a five inch length would fit the gap neatly, so I placed this onto the upper frame at the rear corner. Pulling everything back through, I was able to gauge where everything could comfortable rest. This enabled me to cut those dangling lengths to something more suitable and weld together this basic H support bracket.

The treaded rod was pushed back in place and I used nuts and washers to ensure everything was aligning how I wanted it. Careful use of a tape measure was a must. The H bracket could then be welded into place on the frame.

On the other side of the lid, I was able to adjust how long I wanted the handle. I cut this to a length that suited me and welded a crosspiece, making sure I had plenty of clearance for gloved fingers.

Noticed these holes? I’ve drilled and threaded these to receive bolts. But I needed to make some simple brackets. These hold the lid and support handles together. I fitted these with bolts and metal putty again, initially scoring position, then drilling, and finally adding bolts with putty. I made and fitted similar brackets at the back and the whole lid pivots and opens nicely, providing a nice big opening.

With the lid completed, I turned my attention to the electrics. These connection points will be live when the foundry is in use so they need covering to prevent electric shock. These metal electrical back boxes were a perfect ready-made solution. If I hadn’t had these, I’d have probably built similar sized boxes from sheet steel. These must cover the connection points but NOT touch them.

I enlarged one of the holes in one of the back boxes to take a rubber grommet. This grommet holds very snugly a three core heavy duty mains cable. The grommet is necessary to prevent rubbing on the thin box metal which could slice into the wires. How the rubber holds up with the heat of the foundry I can’t say as yet. So far so good. I don’t think it’s close enough to be effected but I’ll keep my eye on it.

The colour of the three wires isn’t at all important in this instance as polarity with a coil isn’t necessary, though I’ve stuck with the UK colour coding system for convenience. What is necessary is that the wires can safely handle the current you’re foundry will take.

To each of these wires I’ve added more heat sleeving, insulating for heat and electricity. Ring connectors are firmly crimped in place. Notice the yellow tape on the rear cable. It’s crucial to earth or ground all the metal involved for electrical safety and this marked cable is the designated earth lead.

Through the other small hole I placed a small bolt. To this I attached the earth ring connector.

When it came to the ring connectors, I didn’t have one large enough to slide over the 10mm threaded bar, so I took a washer, drilled a small hole in it, and made my own.

The earthing cable is daisy-chain connected to the second metal box and then on to the home-made ring connector.

There’s nothing inside the second box as it is just a cover, but it still needs earthing.

Over at the foundry, the large home-made ring connector slides onto a threaded bar. As this is in contact with all the metal framework, this grounds everything nicely, including the handle.

The other two ring connectors attach to the coil bolts. These are the positive and negative supply, though again polarity isn’t important here. I also screwed in the thermocouple and again hand-tight and a quarter spanner turn is snug enough.

It’s then just a question of fixing the boxes in place.

I used the same bolt and metal putty approach for this. It worked a treat. And that finished the electrics on the foundry itself.

I now had to concentrate on persuading the foundry to lift vertically and to start this I cut four lengths of 1 inch square steel tubing and drilled some 6mm holes in them. Using some corresponding bolts I was able to bolt together two side supports. These when fitted should sit vertically between the two lots of remain brackets on the upper and lower frames.

Using some flat bar steel, I made 8 L brackets. Now you could buy something like this off the shelf, but I was looking for sturdy - plus I needed the welding practice.

With a vice clamped onto my drill press and with repeat positioning, it was possible to drill some consistently placed holes.

When the L brackets and supports come together, they’re ideally spaced to accept a standard skateboard wheel. I got four of these cheaply on eBay. I found 8 washers either side of the wheel held it nice and centrally and I placed two wheels for each support bracket.

These wheel support are now fitted and these need to be carefully aligned to be nice and level. Remember those L brackets I made for the wheels? If the top hole is elongated slightly, the bracket can pivot before being bolted down firmly. This is particularly useful at this stage as the wheels.

I then realised that I’d left no connection points on these supports for the wire rope which was to come later, so I quickly fabricated and added these brackets.

 

At this point, I couldn’t resist a temporary test. In fact I hooked up the PID and ran the foundry for a week at 100 C to help things dry and finished off with a couple of hours at 800 C.

It was over the course of this week that a few cracks appeared in the mortar joins. Maybe it was poor mortaring technique. Maybe it was expansion and contraction. Heat didn’t seem to escape but it made me feel mortaring these levels was pointless, but that choice is yours.

TAOW mentioned in one of his videos that the outside of his foundry had reached over 100 C. I hadn’t noticed anything like that in my short tests, but I didn’t fancy losing that much heat. So in the interests of efficiency I decided to wrap the outside with this insulation material.

Now this claims to have none of the usual nasties associated with these type products, but I wore a mask whilst cutting just in case. As a belt and braces kind of guy, I also decided to contain the insulation within a material sleeve just in case any fibres decided to ignore the manufacturers claims.

This is fine cotton, the sort of thing your shirts might be made from. It’s strong and very tightly woven, so tight in fact that I’ve used it successfully to filter waste veg oil. This meant getting a needle and cotton out and I’m certainly no tailor – but it’s functional.

I will say at this point, if you’re concerned about the cotton being flammable, I placed this piece in my kitchen above at 150 C, which is 50 degrees more than TAOW experienced. As you can see it didn’t burn. I later experimented in 10 degree increments and noticed it starting to brown at just over 200C, so if I ever see it browning, I know I’ve got a problem.

At the ends I looped some string and sewed this is place to help fixing. Remember this is string, not chord. Chord will likely melt.

These insulation pads are certainly an added extra. They squeeze in nicely behind the threaded bar and cover every except the metal boxes at the rear (which I want to breath and keep cool) and the two side wheel supports.

Remember how the top two rows aren’t mortared together? I didn’t want them getting knocked off so I needed to keep them in place but NOT grip them rigidly, allowing for the expansion and contraction that the cracks suggest is occurring. Think of it like holding a frog – you want to hold it tight enough to contain it, but no so tight and to squash it.

With this in mind I made a crude jig from some brick scraps and by welding some flat bar, I made these simple corner supports.

When it came to holding these in place, I initially positioned them using masking tape, then took a long jubilee clip and tightened this. Unfortunately it was rubbish. It simply wouldn’t tighten. So I ended up making my own version with metal strapping, angle iron scraps and a bolt. That worked much better.

The strap was tightened such that it held the corner supports in place but didn’t do so harshly – just enough really. When this is coupled with the insulation blanket, I’m hoping I’ve got a contained but happy frog.

LIFTING ASSEMBLY

And that’s the foundry completely finished. What it now needs is a lifting mechanism and that starts with timber.

For these two main uprights I went with 4 by 4 timber. This may seem a little excessive, but I want the timber to be strong and hopefully stay fairly straight. They need to be relatively tall to give lift clearance and these were 1.8 metres or 6 foot.

To accommodate the rollerskate wheels it’s necessary to cut channel in one of the four sides of each post. This needs to be just a tiny bit wider than the wheels, to prevent binding, and around half an inch deep. Again I turned to my router for this job.

With that done it was just a matter of fixing the posts in place. I initially used a ratchet straps to hold the posts loosely in place whilst I added top and side supports until a rigid, level frame was completed. There’s no fancy carpentry skills here – just cutting and screwing.

The wheels need to rest within the channels in the posts. They shouldn’t be tight as some movement is expected. Ideally they should float free of the posts but look as though they’re touching – that’s how close they need to be. But if they’re fixed firmly against the posts, you can expect a lot of jamming rather than smooth lifting.

Don’t think of this wheel and channel arrangement as a restrictive frame. We want the foundry to rise nice a straight, without twisting or turning and hopefully without striking the posts. If it does strike a post, the wheels should keep this fairly friction free and hopefully aligned how we want it.

To raise the foundry I toyed with a few ideas, including counterweights, a ratchet and chain system and then block & tackle. It was this last idea that really grabbed me. The pulley is an amazing machine – so simple and yet so effective.

There’s lots of informative material out there on pulleys, so I won’t cover them in depth, but a very brief review might be helpful. So…

Here’s a heavy box that we need to lift. We’ve got to lift it upwards and you can think of the red arrow as being the amount of weight and effort involved in the lift.

So what if we use a pulley to help? Well this arrangement, with a pulley fixed to the ceiling or a stable structure is called a “Fixed Pulley.”

When the rope is pulled, the box can be lifted but it still weighs the same. It’s still the same amount of effort. Nothing has really changed. Yes pulling downwards is more convenient than lifting upwards, but that’s the only benefit of a fixed pulley – changing the direction of the effort. So a fixed pulley changes direction.

But what happens if take the pulley off the ceiling and put it on the box? This set up is called a “Movable Pulley” as the pulley moves along with the weight that’s being moved. This time when the rope is pulled, the effort is halved. It’s actually easier. This is because half the weight is being shared by the ceiling support and half the weight is being pulled by you. So a movable pulley reduces the effort – but we’re back to pulling in the wrong direction.

So let’s add back in a fixed pulley on the ceiling. Now we benefit from BOTH factors… the movable pulley reduces the effort and the fixed pulley changes the direction.

The really great thing about this is that we can duplicate this as many times as we like, adding in more pulleys. Here’s six in total. This set up dramatically reduces the amount of effort involved in lifting the box – in this case by a factor of 6. And that’s the set up I used to lift my foundry.

Fortunately rather than have all the separate pulleys and fixing, they can be added together into what’s commonly called a block and tackle.

And if you’re thinking you can’t get something for nothing, you’re right. There has to be a pay off – and that pay off is you just have to pull more rope. I don’t think that’s a bad trade.

You can easily buy pulleys online. Just make sure they’re large enough to handle the size of the rope you use. I prefer the metal variety and also prefer slightly larger pulley wheels.

Now I did conduct a few experiments and the configuration I eventually came up with is this. It’s difficult to show it in place, but I’ll describe it as best I can.

It’s important that both sides are pulled at the same time to keep things level and I achieved this using a loop of wire rope connected to either side of the foundry. The steel rope ends pass around a thimble to produce a stable eye and are clamped with appropriate fittings. These then link to the appropriate brackets. This loop of wire rope needs to feed through four pulleys – two singles and two doubles.

Starting on the left, the wire rope goes up and over a single pulley heading right. It then rests on the top of a double pulley, through a hole in the frame, over a second double pulley where it’s redirected downwards, does a 180 degree turn around a single pulley, back over the second double, through the frame, over the first double and down to the right side of the foundry where it connects.

This whole arrangement serves only to redirect the pull as I simply don’t have the height available above my foundry. The second single pulley is a floating, movable pulley that helps centralise the pull on the cable. The whole weight of the foundry is now redirected to this pulley – to this point.

Now it’s just a matter of using a block and tackle arrangement - but upside down from conventional set up – to lift this weight.

To lighten the load I’ve used two triple pulleys in a block & tackle set up. The top triple pulley system is movable the bottom triple is fixed to the base of the frame. The lifting effort could be reduced even further using four, five or six pulleys, but I could only find these triples and they did the job for me.

To raise the foundry, this bottom rope has to be pulled upwards. It’s actually not too bad – it’s not easy, but it’s much easier than trying to lift the whole thing by hand. At this point you could add counterweights to make lifting easier, or maybe a manual crank handle. Maybe you’d prefer to use a car engine hoist. But as I’d gone this far, I wanted to finish off with an electric hoist.

ELECTRIC HOIST

If you’ve seen some of my other videos, you’ll know I’m a fan of these electric wheelchair motors. They’ve got bags of power, have a fabulous gear set up and are readily available used online.

I decided to use this 24 volt motor as the muscle behind my hoist.

This one came with a bracket and a wheel.

I was able to use the bracket as a guide to drill these square bar supports. This enabled me to screw the motor firmly to the frame.

Originally I thought of using the hub from the wheel to collect the rope. But it was simply too large and the torque involved meant the wheel wouldn’t turn.

However I was able to remove the centre from this hub and fashion a rope spindle did work but – confession time guys – it got a bit twisted out of shape. This shows you the forces that are involved here.

This spindle was simply the hub, four lengths of M8 rod and an MDF stop end. But in use the pressure of the pull squashed and bent the steel bars. Now I could make another, but the squashed centre actually makes the rope centre on the spool, so it was a happy accident as the great Bob Ross used to say.

But I showed you what can happen and the choice is yours. I decided to reinforce this with a few welds. I then taped over the threaded rods to reduce wear on the rope and I also added a stop end to the hub as once or twice the rope has spilled off the end.

This spindle or spool is attached to the motor and the rope is firmly tied to it.

Now hang on – I said rope there didn’t I… not steel rope. So why the difference? Well again this a personal choice. I found the steel rope very inflexible, but it’s close proximity to the foundry made steel an obvious choice. But for the pulling mechanism, this rope is much more flexible between the pulleys and it’s far enough away from the heat of the foundry to not be affected.

To power the wheelchair motor I used a 24 volt LED transformer. This one can handle 10 Amps so it should have no problems here. When coupled with this momentary DPDT switch which can reverse polarity, I’ve got a motor moving forwards and backwards at the push of a button.

I’ve already shared a video with you on wiring up a DPDT switch to reverse polarity. It’s a very useful switch function to know about.

Now where you place your motor is up to you. I placed mine on the opposite side of the frame to the pulleys – purely for personal convenience. But this meant I hand to redirect the pull rope via two single pulleys up and over the foundry, dropping into the spool.

And sure enough this gutsy motor has no trouble lifting the foundry. It’s wonderful gearing also ensures that when the switch is released, the foundry is held mid-air, giving excellent access to the crucible.

 

- - - MORE COMING SOON - - -

If you want to see my YouTube video on the subject, simply click below:

Watch The Accompanying Video...




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