The Bucket Foundry

[Grumph]

Back to lost foam..
Ken, what you describe, biscuits, sounds very similar to how John Britten produced the patterns for his cylinder heads. What they did was put the design onto a cad programme and produce sections at 5mm spacing. They then produced solids of those sections by waterjet cutting 5mm MDF board. Some gluing and smoothing, add risers and job's a good'un.
i can see no reason why 5mm thick foam sheet can not be substituted and the encasing in suitable refractory material done as usual.

There's still a fair amount of hand work involved but the production of the sections is very rapid and won't involve the capital for moulds...
I know of an outfit in ChCh NZ who will do foam sheet in pretty well any thickness you want. I'm sure there are plenty around the world who will do the same.

[TZ350]

CNC DIY Hotwire Foam Cutter. http://www.instructables.com/id/Make...parts-availab/



and DIY handheld hotwire foam cutter

[husaberg]

CNC DIY Hotwire Foam Cutter. http://www.instructables.com/id/Make...parts-availab/



and DIY handheld hotwire foam cutter

A mate at work built one for making model planes I think he used a starter transformer I had on my desk out of a florescent light and some other stuff we had lying around.
My lady still hasn't got the light in the upstairs bathroom fixed on account of that.

[ken seeber]

Well, had a successful cast using plaster moulds. The moulds showed some external cracking at around 500 C prior to casting, however they kept together possibly cos we used a mesh surrounding the outside of the mould. Pics tell the story. Will do the rest, some the same and try a few alternatives as well. Anyway, irrespective of whether the things will actually work, the main thing, that I am sure you will appreciate, is the fact that the STRIKE "S" logo came out ok.



Grumph. You got me going a bit, as I looked into lost foam a bit more, particularly seeing one dude CNC machining the foams. Just to clarify, the biscuits I remember that Mercury used were specifically moulded to shapes, but with the part or join planes carefully chosen as part of the design process. See crappy sketch below. Maybe using thin layers one could build up a disposable pattern. Using something like Solidworks, one can easily do a series of sections, saving them as .dxf files that a CNC router/wire cutter man could easily make. The layered model that Frits posted of his FOS cylinder is a good example of this. As one would naturally have a series of contour steps at each interface, the biscuits would have to be carefully designed though to have additional material that would be available in critical areas such that they could be smoothed off whenever there is a curve, eg roof of a transfer port. One could even do a hybrid with traditional methods combined with foam.



Just to consume you for few hours, have attached some links that explain the process in a bit more detail.

https://www.youtube.com/watch?v=6fEU3fuQd9s This one has some amusing and quaint language interpretations.
http://www.lostfoam.com/content/lear...e_castings.php
http://www.lostfoam.com/content/lear...am_process.php

[Grumph]

Ken - good to know I may have helped. I'd love to look at those links but on slow dialup, I may not live long enough...

What little i know of solidworks and similar programmes suggests to me that the sectional pieces don't all have to be in the same plane. Careful selection of divisions both horizontal and vertical - even radial - could well pay dividends.

[Michael Moore]

You should be able to do wire cuts on your 3D model and slice it up any way that you need. In Rhino you can do a wire cut with a line or make cutting planes and do a Boolean split to get all the layers.

If doing layers of foam consider angling the wire where possible to eliminate using a lot of filler. If you want 7 degrees of draft, do it with the hot wire on the foam cutter.

If building up by slices the thinner the slices the closer you'll be to a net shape when using a 90 degree hot wire (laser, water jet, knife on a vinyl cutter, etc). But that does mean more cutter time which if you are paying by time means more money. Don't forget to have some way to register each layers to the others.

cheers,
Michael

[WilDun]

Things have slowed down a little on this thread again -

I don't have a lot to contribute right now as I haven't been able to do much with my "foundry" mainly because of the condition my body is in, (my left wrist gave up on me and I have had to nurse it back to health again) now almost better again, but I have been toying with the idea of using a microwave oven (fitted with the necessary ceramic containers etc of course) for melting ally, apparently they work well for small quantities.

I mainly want to try it because it will be big enough for the quite small quantities I'll be needing and easier for me to lug things around.
It would also mean I won't have to load things up and drive way out to Puke to do my first casting experiments! - a long way to go when I should stay close to home and be able to make any changes required in my home workshop.

The plan for the "proper" furnace is still on of course but I need to get some experience first, I don't want to go out there and make myself look like an incompetent 'tosser' - Of course, I may be just that, but I don't want to look like one!!

So I'm looking for a decent ie. cheap but powerful (and perfect) microwave on Trade Me for around $20

[Grumph]

So I'm looking for a decent ie. cheap but powerful (and perfect) microwave on Trade Me for around $20

Garage sales - you have the bonus of being able to bargain, face to face....

[WilDun]

Garage sales - you have the bonus of being able to bargain, face to face....

Yes, I'm not in a hurry so i'll probably get a bargain eventually, but it does seem the way to go for someone of my age and fitness, also for doing the small stuff which I hope to do and of course keeping the neighbours happy, (my wife had to drag me out of the garage at 10 pm last night because she said that i was making a helluva lot of noise - i didn't hear anything!).
Even working on the little lathe is a bit tough for me now! - but I like it and will try to keep going hopefully till i kick the bucket!

[ken seeber]

Small furnaces. We scabbed a couple of discarded furnace shells from the local university. We set up one on wheels with stand alone LPG bottle so we could wheel it outside when burning off wax & nasty plastics when doing lost "whatever" stuff. Also good cos it is really quick to do a melt with small crucibles and piddly melts, rather than crank up our main furnace. The little crucibles were scabbed from some brickworks that closed down, leaving some assay style crucibles that they also made, in their scrap pile....well, that's our story anyway. Seems like we do a bit of scabbing which in fact is the truth, but the real term is recycling.

Added a few pics of the furnace and the lost wax exercise, one using an investment slurry process. Broke away from the outside easily, but the internal stuff was really difficult, almost like cement.

So Willy, hang in there, we want to understand the microwave melting more. You're not the only oldie you know.

[WilDun]

So Willy, hang in there, we want to understand the microwave melting more. You're not the only oldie you know.

Interesting construction used in your furnace - food for thought!

I may not be the only oldie and probably not as old as a lot of them (71, but my body does tend to rebel occasionally) - oh and I can scab with the best of them - a hobby in itself, much to my wife's disgust!

Microwave ovens? well if it works, even if only for small quantities then I'm most certainly going to give it a go, it seems to me to be a light, cheap, clean and easy solution in my particular situation.

This weekend however I'm hoping to light up the original gas fired furnace I made and see how well it performs, it's just that it's a little difficult to lug everything around from one location and drive for nearly an hour to the other - I do believe it'll all work out just fine though, just need a simple solution (like a large workshop close by somewhere) - anyway, we'll see how it goes.

[F5 Dave]

We had Glen racing at 70, think he finally gave it away at 71, but he'd do the rounds with a fair bit of driving.

[WilDun]

We had Glen racing at 70, think he finally gave it away at 71, but he'd do the rounds with a fair bit of driving.

A guy who I knew quite well raced till he was 71, then he had a huge "off" at Pukekohe going into the left hander after the hairpin - that stopped him in his tracks forever!
Even if I had been fit enough to ride and even if bikes were my whole life, I would have called it off at least 10 years ago. Old bodies can't take the trauma the same as young ones! - then of course ......... there's Len Perry, but he needed someone to catch him when he came back in!

I have an oil drum which is a good size for constructing a furnace (courtesy of Flettner) and although I'm going to give the microwave a try, I would like to try his method of construction as it would be very handy for grabbing the hot crucible, also lighweight, making it much easier to load into my old Suzuki jeep for transporting - even though the lining will probably need to be replaced often.

[Kickaha]

A guy who I knew quite well raced till he was 71,

Alex MacDonald at 71 is still competing in the sidecar class and running at the front of the pack and will be for a year or two yet

[WilDun]

Alex MacDonald at 71 is still competing in the sidecar class and running at the front of the pack and will be for a year or two yet

He is an exception! and a very lucky man to be able to do that!

I had planned to be that active too but unfortunately I just had to accept the fact that it wasn't possible for me. I do actually have a push bike and I must be gradually coming right having had a couple of rides on it - couldn't do that a year ago!
However, even that is really quite dangerous for me nowadays, thank god I don't have to push start it and throw my leg over!

It's all a bit ironic when a large part of my life used to be spent pushing bikes around (trying) to get them going!!

Probably I'd be best to trade it for a microwave, much safer (I think).