Resurrection of a CFEI 100 KVA Induction Furnace

[awemawson]

Matthew I think that you are entirely correct - diesel HAS to have some lubricity otherwise the injector pump would sieze up, and this is why 'certain travelling folk' add oil to stolen central heating oils as it's "slipperyness" is much less.

Pekka, the oil 'should' remain at ambient temperatures when in use (barring disasters  ) so it's viscosity isn't going to decrease sadly. All my farming equipment uses ISO32 as it's rare that we get very hot here.

This morning I drained down the oil / red diesel mixture and re-filled with neat red diesel. Timing the rise (pour time)  it is now at 18 seconds which is about acceptable but I'd still prefer to be able to set it a bit faster.

Obviously this is as fast as I'm going to get without either:

a/ Raising system pressure (a pain as it uses my air distribution system common to many machines)

b/ Increasing hose bore

c/ Finding an incompressable medium more fluid than Red Diesel (unlikely)

[PekkaNF]

OK. Because that system has no pumps, tanks, filters etc. there is no real reason to use hydraulic oil. Unless there is no special seal/hose/componenet reason you could go down to 5W straight/mineral transmission oil. Multigrade engine oils has allready many (unnecessay on this one) additives, and the car 5W-something oils actually have higher viscosity than VG32 hydraulic oil at room temperature.

https://www.engineeringtoolbox.com/iso-vg-grade-d_1206.html

There noteworthy thing is viscosity at +40C, different grades are defined very different ways. They don't compare in simple relationship.

There are very low viscosity oils, but they are a bit special and have their own issues. Hard to get lower than that mineral base oils...needs to check too many variables....hydraulic system might work with PAO-base oils too. But where to get them in cosumer market? And they suck at fire resistance


https://www.machinerylubrication.com/Read/31106/polyalphaolefin-pao-lubricants

Interesting problem.

[awemawson]

Yes it has all sorts of ramifications Pekka. For instance the exhaust port silencer now puts out quite a bit of diesel vapour as the cylinders are discharged, so much so that I've put a plastic cup under it to catch the drips.

Obviously is not viable when actually pouring molten metals instead of testing. I am tempted to go back to 'straight air' and drain the reservoir again. I originally went to 'air over oil' as  I was getting rather too much bounce with just air, but maybe if I throttle it back it'll be OK? -

. . . I'll experiment if time permits tomorrow.

[John Rudd]

Dnot wishing to teach grany etc. etc.
 If operating speed is an issue whether pneumatic or hydraulic, cant you use speed restrictors to increase the operating time?

[PekkaNF]

Air tends to be bouncier than incompressive liquid...I understand the merit of the air-over-liquid, liquid throttless nicer.

I wonder if a simple viscous damper would work in addition of the orginal air system? But it involves additional mounting poins, a little calculation and experiment. Also it probably does not not work equally well with min/max loads.

I never used waterbased hydraulics...apparently algae growth is a problen there, glycol coolat based might work, but that one too needs special seals. I would use the original system with air and add separate damper cylinder with liquid throttling or viscous damper.

We used once a system that had two hydraulic cylinders to perform same "swing" because the weight sifted "over the centre" of the gravity. Simplest form was to laod one cylinder (one side) with a constat pressure to prevent load from sifting direction at the middle of the stroke (that would produce a major jolt). There are load lowering valves etc...but each solution has it's own set of problems.

I have seen very well dampened pneumatic systems, but they had servos....

[awemawson]

Dnot wishing to teach grany etc. etc.
 If operating speed is an issue whether pneumatic or hydraulic, cant you use speed restrictors to increase the operating time?

John, If you look 'up thread' you'll see that I have two one way valves (up & down) each followed by a flow restrictor

[awemawson]

Pekka, to be frank I doubt that any practical to use liquid, including water, is any less viscous than diesel, which is pretty free flowing.

Using a liquid as the operating medium has the advantage that it is theoretically incompressable hence no bounce.

BUT Raydne designed it to operate on air - so I'll see if I can temporarily revert to just air and play with the flow restrictors

[John Rudd]

Ahh...sorry Andrew, missed that bit...

[awemawson]

Pay attention John 

So I decided to revert to 'air only' tilting on the Raydyne furnace body as originally designed. I wasn't happy having the oil fumes in close proximity to the molten metal and the speed of tilting was a bit slow. It definitely was less bouncy, but at an unacceptable price in terms of other parameters.

I could put the oil system back relatively easily, but to plumb for 'air only' necessitated physically removing the reservoir (a cut down CO2 cylinder!) as the plumbing for the flow restrictors was screwed into a tapping in the cylinder wall. Just one pipe to remove and a somewhat longer one to make and it's done.

With the restrictors set full bore it now raises in 4 seconds and comes crashing down - just cracking them open gives about a 10 second rise and probably I could extend that a bit with careful setting of the valve. There is no longer a delay in raising the crucible, as that previously was caused by it taking time to pressurise the air over the oil in the  reservoir.

It'll take a while for the remains of the oil / diesel mix to flush out of the pipes and cylinders - already afer only a few cycles the exhaust 'air' is getting a lot cleaner and less fumy.

Meanwhile the more suitable pipe clips have arrived so I'll try and fit those today - not sure my back is up to all the bending down so I may try raising it to waist level with the forklift.

[mattinker]

Hi Andrew,
Are your molds going to be attached to the body?It would seem to me that you'll need to be able to adjust the speed on the fly to be able to have a full sprue to avoid taking in air. How did that work out in the past?

Cheers, Matthew

[awemawson]

No Matthew, with the tilting furnace body you either fill a ladle and pour from that, or arrange your moulds at a suitable height to pour direct, in which case it's a matter of raising the tilt sufficiently for the metal to start flowing, and reversing the lever to start descending to stop the flow when the sprue is full.

I managed to clamp the hoses - I can't say I'm over happy with the way they lay - flipping awkward stiff things !

[awemawson]

Gentlemen (and Ladies if present!)  I have a dilemma 

I've been wanting to power up the Radyne and use it, but at the moment I'm completely confused as to it's connections. I'm SURE that I used it previously after installing the new crucible, but the way it's internal plumbing is illustrated in the picture below it CANNOT have worked I think.

I had expected the terminals to map A, B, C, D from left to right and indeed on one photo the extreme right hand pipe has a D on it

As the photo clearly shows, Terminals 1 & 2 are connected ELECTRICALLY as are Terminals 3 & 4 - you can see the blooming great copper horizontal strap between them.

Now the actual induction coil  has a deliberate blockage where the nylon reinforced hoses from Terminals 2 & 3 come together.

So coolant entering 1 can ONLY exit by 2 (and vice versa) and coolant entering by 4 can ONLY exit by 3 (and vice versa)

BUT the electrically commoned terminals on the furnace driver are pairs "A & D" and  "B & C" with coolant flowing out of "B & C" and returning on "A & D"

So if "A & C" on the driver map to  "1 & 4" so that the top and bottom of the induction coil are connected correctly coolant has to come out of  "2 & 3"

On the tilting furnace body the terminals that are commoned at it's end correspond to the commoned ones at the furnace driver.

If I screw this up it could be curtains for the driver electronics 

So if any of you have been able to follow my confused ramblings - please go logically through this and tell me where I've gone wrong - or have I gone wrong - or did I plumb it up wrongly back in 2006 ? (I can see that if I swapped over the two internal nylon reinforced hoses within the Raydyne it might make more sense )

. . . my head hurts . . . .

[awemawson]

So in the absence of other suggestions, this morning I opened up the back of the Radyne Tilter, and lo and behold it seems that I'd done a second re-plumbing eliminating the welding cable current reinforcement by using heavier walled pipe. (It looks like I've used 3/4" air con pipe tailed with 15 mm) However the issue remains in that if connected up it would put a direct electrical short across the Furnace Driver - not good.

I 'think' by interchanging the nylon reinforced pipes I have a solution that 'should' work - certainly now no direct short across the driver !

I was able just to uncouple the threaded fittings and move the pipes, but I'm not happy with their lengths as they are touching the copper driver pipes, but I'm out of stock of 15 mm bore nylon pipe - they'll do for test purposes until I can get some more.

So now "A & D" are electrically commoned at both the Driver and Crucible ends, as are "B & C" but the order of connections on the base of the furnace body are a bit illogical reading "C B D A" left to right

I do remember having standard metal Jubilee Clips getting hot in the field of the coil and melting pipes and sure enough the ones on the outer connections of the nylon hoses are nylon clips to avoid this problem, but oddly the ones on the other end of these pipes are standard metal ones

[RussellT]

Hi Andrew

I'd just spent 10 minutes trying to understand this when you posted your latest update.  I think I agree with where you've got to.  Clearly the electrical connections have to take priority and that means the piping wouldn't have worked unless there was something strange going on at the connections on the side of the coil.  The other variable I was trying to get my head around was whether there was any significance to the direction of coolant flow - for example to keep the nylon pipes cooler than the copper ones - but I would hope that they would be kept sufficiently cool for that not to be a problem.

Russell

[awemawson]

Russell, now you see why my head hurt - thanks for your ten minutes - much appreciated !!!

One 'advantage' of this flow system is that cold coolant enters both sections of the coil at their respective bottom coils and leaves at their highest coil thus circulation is aided by thermal / gravity effects. Whether this is at all significant is debatable though!

Much search for 15 mm bore nylon reinforced pipe so far has drawn a blank. 13 mm no problem. 16 mm no problem. 15 mm no sign 

I am conscious that access to the centre connections on the coil is severely limited so struggling a pipe on would be an issue - the other end access is easy so no problem.

[charadam]

Any use?


https://www.hoseshop.net/reinforced-pvc-hose/pvc-reinforced-hose-18mm-od-x-13mm-12-i-d-15-mtr

[awemawson]

That's the sort  of stuff, but sadly they also only offer 13 & 16 mm o/d 

I've found a place on eBay that stocks 14 mm so I've ordered a bit (1 metre) of that, and also a metre of their 16 mm. Probably the 14 mm will be OK when warmed up a  bit, but as I said before access is tricky. (The adjacent side panel does bolt on, but it also holds the pivot that the whole thing swings on so not easy to remove)

[Pete.]

The 14mm hose will easily go onto a 15mm barb if you poke it up an exhaust pipe for half a minute. I've done this many times on site especially in winter.

Engine has to be running

[mattinker]

Andrew,

If your object was to give us head aches, you  succeeded! I couldn't see it from your explanation and diagram! Seems to me to be break out the ohm meter time! Good luck with the hoses! It's so near now!

Cheers, Matthew

[awemawson]

Matthew I knew that it was a difficult concept to get across - I struggled writing it coherently - but basically if connected so that the coolant flowed correctly it would have put a dead short across the driver output and if connected so the electrical drive was correct, no coolant would flow (I think!)

[mattinker]

Andrew,

I sort of understood your worry, I would have needed to see more to under stand it easily! The ohm meter is your friend!

All the best! Matthew.

[awemawson]

No point in procrastinating any further - get it connected up and try it !

. . . . so I did, but firstly I connected up the low power local mains feed - can't really start the big generator as the cottages are full of guests - and made sure all was working on the inverting furnace body before disconnecting it. Yes - all OK - so I removed the four hose / cable assemblies. Proved continuity where it should be, and connected up the Tilting body.

First test - does the coolant flow? Argh - NO  Oh heck NOW what's up? Intensive investigation and what do I find - those pair of flexible pipes that go to the centre of the coil do a little jig round the back and come out REVERSED ! So what appears to be the top of the lower half of the coil is in fact the bottom of the upper coil, and vice versa. So Russell you pretty well put your finger on the problem in you post where you said "unless there was something strange going on at the connections on the side of the coil".

This has been the issue all along - the pipes I moved were in fact in the correct places - there WASN'T a problem - it was actually correct in the first place.

OK, get over it, swap the pipes back, prove coolant flow - YES flowing in both circuits.

So, next test - put (low) power on the driver, let it come ready - yes it does - 'ping' the furnace body - whoopee yes we get a good result at 2.25 kHz - as expected a lower frequency than the other body as this one is a physically bigger coil so presumably markedly different inductance.

Now until I can get the place to myself and hence fire up the big generator that's about as far as I can go for the time being apart from tidying up and sorting out the safety shields etc for the pipe / cable assemblies.

. . . phew it seems to be working . . . thank goodness . . . it took long enough !

[RussellT]

 

Russell

[edward]

Andrew, I've enjoyed immensely following this trouble shooting and you getting to where you are now. Its the same with all your threads for me, the detail, analysis and skill in solving problems is brilliant to see.

I have a question, to which the answer might well be'because I can/want to/its there', but what will you do with it once its up and running? Do you do casting a some kind of business, for fun or just enjoy fixing up old machinery.

Its not a criticism at all, I'm just curious I get asked a similar type of question as to why if I have 4 bikes I need to build myself a 5th one, to which the answer is that I like bikes!

P

[awemawson]

Edward, it's a bit like the 'why do you climb mountains' question - it's not logical  but I enjoy it - that's fixing problems by the way not climbing mountains!

No there is no commercial thing here, and I really no longer need to make castings, but at my last place I'd set my self up and was determined to re-create the facilities that I'd lost in moving. It's only taken 13 years 

It all began when, many many years ago I was driving home from work through Peckham in SE London and spotted something 'interesting' in the far corner of a Taxi repair garage. After several days of rubber necking to see what it was I stopped to have a good look. It turned out to be a "Hoverair Hoverhawke" three engined hover craft in 'basket case' condition. Chap said that I could have it for peanuts if I took it away.

Back then I had no workshop or machine tools. Well it ended up on the back lawn on tressels needing comprehensive repair to parts of the box section chassis, and the engines and propellers re-assembling and missing parts sourced. One missing part was an aluminium casting shaped a bit like a pudding basin, that bolted onto an engine flywheel and coupled it to the propeller. This got me involved with a local (to me then) foundry and a machine shop, and this kindled my interest in casting and machining.

The rest is history - my workshop has developed from that project over the decades. I got the hovercraft back together and hovering on the lawn - it was pretty big with a three man enclosed cabin - but I never finished the cosmetics. I'd put a bid on an entire redundant computer network infrastructure in the city and my bid won. The kit was in a warehouse in Kew at a vast rent so had to be moved pronto into my dining room (floor to over the picture rail), three removal lorry fulls - about 7 tons ! and the powers that be put her foot down and said she wanted either the lawn or the dining room back - most unreasonable.

I sold the Hoverhawke to a chap in Essex, but now it is in the hovercraft museum:

 https://www.hovercraft-museum.org/collections/

The network kit - that financed buying my next house and ultimately the farm where we are today 

Now I'm sitting here willing my cottage guests to go out for the day so I can start up the big genny - I've sort of decided that if they'e not gone out by 11:00 I'm doing it anyway !!!!!!!