Resurrection of a CFEI 100 KVA Induction Furnace

[vtsteam]

Snap flasks. Cool. Do you have any photos of the pistons, Andrew? 

[mattinker]

Andrew,

I can see snap flasks as being really useful with lost PLA in silica sand Sodium Silicate molds! Burning out the PLA would be better without the flask! I use petrobond so it's not the same problem for me yet, I have just bought a really cheep 3D printer, which because it's cheep, is proving to be somewhat challenging to get together! I have a foundry supplier near me so I was thinking of going the other route, investment plaster for lost PLA, My kiln, which is vertical, "200liter oil drum gas fired) top opening will allow me to pour molds hot without removing them.

Cheers, Matthew

[vtsteam]

I'm wondering if those piston molds are baked or solidified somehow (sodium silicate?) because it looks like they are meant to be stood up from their present positions. Without a flask, that would seem difficult. Well, maybe the flasks were replaced for the turnng operation?

I'm guessing the cone ended hollows are giant sprues. Or if they aren't meant to be poured that way, and lie on their sides, what prevents the horizontal cores from popping out during the pour if there is no flask to hold them in place?

What's the scale of this -- maybe it's smaller than I imagine. I was thinking full size engine pistons, but if this is model scale, it would be easier to understand and the sprues might actually be small.

[awemawson]

Steve,

A/ They were for 1 inch finished diameter pistons

B/ The sand was silver sand and 4 % sodium silicate

C/ They were stacked vertically, several at a time, and clamped with a sash clamp

D/ The alloy was one of the LM series from a scrapped large Diesel engine piston

E/ Initial ingotting was a pain due to steel reinforcement in the original pistons

They turned out rather well. The white colour is parting powder. It must be 15 years since I did them!

[vtsteam]

Thanks, Andrew!

[awemawson]

Every now and again I start up the generator to warm it up and blow the spiders away, and often fire up the furnace for the same reason - but it gets boring just heating a bit of steel to a nice cherry red, and I'm still not equipped to actually decant any into moulding boxes (no boxes made yet and the pump up table that will hold my moulding boxes during a pour currently has a VAST transformer on it that I can't move single handed  )

Now kicking about at the back of my bench has been the remains of the die cast frame of a Dell Optiplex 'All in One' frame (PC and monitor all held together for desktop convenience - I just wanted the PC sleeve and it's mounting to screw to a wall by my desk!)

So rather than chuck the scrap out it got popped into the crucible during one of those 'spider clearing' sessions this morning. I reasoned that it is either a zinc or aluminium alloy, and if left to cool in the crucible it should shrink enough to shake out - just so long as there is no antimony in it, as that EXPANDS on cooling !

Sure enough hitting it with 30 KW for three minutes produced  one kg of molten mystery alloy and on cooling it was easily removed - so what is the alloy?

This question prompted me to dig out my "Analoy Portable Alloy Identifier" - I'm sure I've shown it here before but probably a few recently joined members won't have seen it. There has an 8085 (I think) embedded microprocessor driving it. Basically you strike an arc between a graphite point and an earth terminal and the device gathers up the emitted spectrum and works out what proportions of what metals  are present. (A predecessor to the XRF analysers of today)

Not surprisingly it turns out to be  85% aluminium, 7.5%  silicon , 1.27% copper,  1% zinc with traces of Magnesium and manganese but what did surprise me was the 3.64% of Iron. I'm not at all sure that that was a deliberate inclusion or maybe something dissolved into the mix during processing.

 . . oh and yes I HAVE ordered a new ribbon for the printer !

[hermetic]

Sounds like chinese aluminium! not enough copper for duralumin, nowhere near enough zinc for zamak/mazak type alloy, so it must be  mongrel aluminium! I like the look of that Analoy box of tricks. Clever stuff! How is the water level?
Phil

[awemawson]

I've no doubt that the die-casting WAS made in China - much Dell stuff is / was but it actually was a very well made item.

No doubt the Chinese Dell assembler would have subbed out the die casting and although the alloy would have been specified the correct specification material probably wasn't used.

Subbies not using the correct specification materials has happened before. The MOD had a new sniper rifle, developed by Accuracy International who were a small outfit. When many more than they could provide were ordered the manufacture was subbed out and the wrong steel was used for the firing pin resulting in dangerous jamming and breaking - the weapon firing when the bolt was closed and not waiting for the trigger to be pulled 
 Accuracy International brought manufacture back in house and re-designed the  pin so that it was visible at the rear of the bolt but of course if the right steel had been used it wouldn't have happened anyway .

[awemawson]

Sounds like chinese aluminium! not enough copper for duralumin, nowhere near enough zinc for zamak/mazak type alloy, so it must be  mongrel aluminium! I like the look of that Analoy box of tricks. Clever stuff! How is the water level?
Phil

No more major floods but still loads of condensation on  the floor the minute we go from cold to marginally warmer

[vtsteam]

I'm sure you know Andrew, the only practical remedy for that is to seal all outside air openings as much as possible. Unless we heat the space, or dehumidify, or insulate above the slab. Well, or wait for spring.

I feel your pain. I think it's a common experience for any of us with small shed shops, unfortunately whatever the slab is doing in a high humidity warming environment, anything massive will also do, even if the slab were covered. So equipment in that situation will also have condensation on its surfaces. Even metal stock.

If a shop is tight and insulated -- that is lessened because the shop goes through longer temperature and humidity transitions than the outdoors so it sort of averages out enough to make the temperature differentials of massive objects and the air non-condensing.

[awemawson]

Yes Steve, little chance of sealing it up and keeping it warm - the building was built to be drafty  - I'd intended to put a gas powered furnace in as well as the induction furnace so needed to loose heat !

I'm controlling the problem at the moment using a powerful squirrel cage fan blowing across the floor at low level, and as the weather gets better hopefully the slab will dry out a bit and lessen the issue now the external drainage has been installed. This fan is intended for drying out premises after floods - so highly appropriate !

My intention was to somehow shift the big transformer and get on sorting out the foundry infrastructure but I got distracted by having to sort out my Hydrovane 502 compressor - I knew it was due a service and was getting slower to build up pressure, but when I drained the oil from it and opened it up I found that the 'separator cover' was cracked around the housing for the minimum pressure valve. I managed to source a replacement which along with new O rings and oil has solved the problem, so back to the foundry !

[awemawson]

As I'm a bit more mobile now I thought I'd try and tackle that transformer, get it onto a small dolly that I used to use for oil drums, and release the pump up trolley for the foundry.

How hard can it be, after all gravity was helping as the dolly was much lower than the lowest setting of the pump up. Well, actually NOT that easy but no fingers or toes were lost and it's now on the dolly - phew. IF ANYONE WANTS a 240 volt transformer for goodness sake come and take it away. (I'd intended to make a very large 3 phase converter with it but now I have proper 3 phase)

So - to clear a bit of space I decided to initially concentrate on the 'tilting' furnace body and put the 'inverting' one in storage for the moment - it got tucked away in the generator room once I'd worked out how to roll it's not inconsiderable weight over the threshold strip that I'd installed to keep rain out (answer - sheet metal ramp and take a run at it  )

This allowed me to move the tilting body to close to it's final resting place, and offer up the pump up trolley. My intention is to make a stand to take a ring shank pouring tool for most pours, but the trolley will be used for simpler stuff direct to the mould.

. . . but that's in the future - at least a bit of progress after several weeks of enforced inactivity.

[RussellT]

I can't believe you haven't got a hoist somewhere that you could use to lift your transformer.

Russell

[awemawson]

Got got a blooming great fork lift but I couldn’t get it near enough due to clutter. 

I’ve got an old (actually new never used but old if you know what I mean) Haltrack engine hoist that was so tangled I gave up !

In the end I just did a highly risky tip and hope job !

[awemawson]

Today's Job - Find my ingot moulds ! I used to have two ways of producing ingots from scrap.

Firstly I had (have) several ingot shaped blocks formed from wood as patterns, and painted to lay on a board to make open moulds using sodium silicate sand. I've cast hundreds of ingots using these patterns and I've actually managed to locate them - but I'm not yet ready to mill sodium silicate sand (although I have all the materials)

Secondly I had a series of ingot moulds formed from inverted angle iron with plates welded on the ends - sadly these are long gone and lost in the mists of time.

So today, armed with a length of 3" angle iron left over from the Generator Room build, and a plate of 3 mm steel that originally was part of the CNC Plasma Table before I re-built it, I set to to make one at least so that there is somewhere to pour the left overs of melts.

Simple welding job, but of course you have to test it don't you 

First attempts didn't go too well - I was anxious not to 'stew' the melt (that bit of die casting that I melted yesterday) and when I came to tilt the pot to pour the metal out it solidified as I did it 

The good thing about foundry work is that you can hide your mistakes by melting them down again  - second time no worries about stewing - just wack some 45 Kw into it until it's jumping out of the pot, turn off the induction driver and pour it. No issues with flow this time but it did show the the floor istn't level !

Now I need to source some aluminium alloy scrap - I had  huge pile of ingots before I moved here - they all went to the scrap yard to avoid having to store them - so now I'm looking for clean engine / gearbox /  castings to replenish my stocks.

It's mighty fine just being able to start the generator and bore hole cooling system, kick off the Induction Furnace and produce molten metal on demand with very little fuss and bother and pretty quickly.

On the Generator I did notice a minor diesel leak on a fitting on the feed from the tank to the lift pump - just a drip but I need to sort it - don't want to return from a melt to find the generator on fire    Of course the tank shut off valve is stuck firmly open so I'll let everything cool down and probably tackle it tomorrow. It's the type with a taper core, so it probably just needs a tap in the right direction to free it but not while the engine is hot I think!

[hermetic]

Excellent progress Andrew, now if you had an old tractor radiator with an electric fan behind it, you could shove the cooling water through it and keep the foundry dry in winter!
Phil

[awemawson]

First thing this morning I gingerly applied a bit more force to the  generator diesel tank shut off valve and managed to close it without snapping off the delicate operating lever - phew ! It's ever so stiff but it's probably not been used in twenty years.

This means that I can dismantle the down stream plumbing towards the lift pump and re-assemble hopefully to cure the weep. Careful examination tells me that it is entirely possible that the leak is actually at the cover gasket of the lift pump. I presume that there is a mesh filter under it. Anyway I'll dismantle the cover and the gland fittings and put it back together with some loctite thread sealant.

The lift pump is by AC so I need to google drawings if any exist for this 1970's item.

But not just now - it's only minus 1.5 deg C out there but feels a lot colder. Being a wimp I'll do it when it warm up a bit !

[russ57]

it's just dropped below 30 here... Degrees c that is - at 9pm.
Expecting a low of 25 at 2am then 40 tomorrow.
(Melbourne, Oz)



-russ

[awemawson]

I'm on my way Russ, put the beers in the 'fridge !

Well it turns out that my policy of getting my hands on all documentation that I can regarding newly acquired second hand machinery has paid off 

One of my eBay purchases was a full manual for the engine - well for one very similar actually, and in it are three pages dedicated to the lift pump along with an exploded diagram. Rather over the top I reckon as the construction is entirely conventional - these lift pumps are all very similar. My Italian cold saw uses one for cutting oil off some Italian vehicle  and when it failed I was able to replace it with a spare that I had held for my JCB digger! In fact even the internals were interchangeable.

So as suspected there is a filter under the cover which I'll whip off when the wind changes.

(Photos attached at higher resolution as they are a bit detailed)

[awemawson]

This afternoon I pulled it all apart an hopefully have sorted the weep - time only will tell.

When I looked closely at the picture of the lift pump I realised that there were distinct signs of fatigue crystallisation of the solder joint retaining the ferrule onto the diesel pipe, now this is lower than where I saw apparent weeping but with an engine vibrating odd things happen with liquids.

To satisfactorily re-solder the ferrule involved removing the rather long and complicated fuel pipe - easy enough except that there are three spring clips retaining it that are fixed with self tapping screws into the engine casting. Every similar clip screw holding the wiring when I re-built it sheared off, so this time I carefully bent the clips to release the pipe. After that just two ferrules to unscrew. Blow the diesel out of the pipe, clean pipe and ferrule and re-soft-solder. I think fittings like this should be hard soldered, but it's lasted best part of 50 years so far and it's pretty well impossible to clean solder off sufficiently to let you hard solder / braze.

Then I opened up the lift pump and cleaned it up, unscrewed the inlet coupler, re-fitted it with Loctite Thread sealant, cleaned up the cover and it's rubber seal and re-fitted it with a smear of sealant.

Once the pipe was re-fitted (clips a bit of a pain!) I turned back on the tank stop cock, slackened off the lift pump inlet fitting bleeding diesel through, tightened it up again and crossed my fingers starting the eingine.

No dramas, engine fired up normally and I ran it for maybe five minutes to no apparent weeping. However I've just been out to check it and darn me if there isn't weeping from the lift pump cover gasket 

Not a major issue if I can find a replacement - it's domed - not sure if that is by design or by age - may be a flat one would work inwhich case I can make one 

[awemawson]

As I have  no model number for this pump, just Dorman’s part number, finding spares is not easy. I’ve measured the body of the pump it's about 58 mm but 'rebuild kits' on the web show a smaller diameter body.

I laser cut a pair of 0.4 mm fuel and oil resisting paper gaskets, but wasn't convinced that they'd have sufficient give. Also rather oddly the central pillar on the pump into which the cover retaining screw fixes protrudes a few thou higher than the out sealing rim - maybe the cover has been over tightened? Anyway I rejected the 0.4 mm paper in favour of some 2 mm nitrile bonded cork gasket that I had that claims to be fuel and oil resistant. Now I know from previous attempts this stuff doesn't cut on the laser - it just burns - so it was a scalpel job. But after all it's a dead simple shape.

Anyway I've fitted it, bled down the diesel again and run the engine for a few minutes, and so far no weeps - but I've been here before so I'll withhold judgement for a day or two!

[vtsteam]

I've had poor luck with my own made rubber/cork gaskets they seem to deteriorate fairly quickly. I don't know why. May be the quality of the material I've bought locally.

Andrew are you sure that's not meant to be more than just a gasket, ie a flexible diaphragm?

[awemawson]

Steve I’d had the same thought before I pulled it apart,  but the working diaphragm is in the next layer down and sound as far as I can tell. On the far side of that diaphragm are in inlet and outlet valves, this upper chamber being an inlet reserve.

If you look at the exploded diaphragm above it’s all explained I think. Part #10 is the working diaphragm. 

I went out just now to check, and it’s dry as a bone I’m glad to say. It’s pretty good quality gasket material with cork bonded together with nitrile. You can’t pull it apart by hand. It’s the same material that I used on the housing for the water jacket thermostats and that’s holding OK.

I’ll run the engine for a more prolonged period tomorrow. I’ve a feeling that I have a large Lorry piston tucked away that can be turned into ingots !

[vtsteam]

I'm thinking though not the pump diaphragm, it might be a damper diaphragm.

[RussellT]

I assume we're talking about part number 4 on the exploded diagram.

If it's just a seal why would the cover need to be that funny shape with an air space under it.  Could this be a diaphragm to maintain pressure while the working diaphragm is being pulled back?

Russell