Diesel Burner

 Since I built a larger furnace, I can still melt aluminium with propane, but bronze,not so much. So it was time for a diesel burner.

Based a lot on a youtube video: Building A Burner. Thanks to swdweeb for the video, and some additional help he gave me along the way.

* A power Supply

* A PWM Controller

* A fuel Pump

I used a Danfoss 2GPH 60 degree oil furnace nozzle, and drilled out some steel bar and tapped it to make a holder.

I have a 250watt blower for the air supply.

Some things I learned along the way. 

• The fuel pump needs more than 5 amps - my benchtop supply tops out at 5 amps, and it was not enough.
• The power supply and PWM are 30amp, because they are cheap, I think the pump runs about 8-10 amps, and I didn't want to be near the limit.
• The 2GPH is too much, at 30% pwm I am bounded by the air I can push in.
• The 40mm hole I left in the furnace for a propane burner is kinda small for diesel. I wish I had 60mm instead, then I could push more air at a lower speed.

I'm going to get a 1GPH nozzle with a 45degree solid spray pattern, and see how that works. It should allow me to turn down the furnace with a higher degree of control.

I'm going to shorten the air hose, to hopefully allow more air in.

The grey connector which joins the air hose to the burner tube is 3d printed PLA. The air blowing through it keeps it plenty cool, it does not melt. Because this is bent at an angle, my diesel run is just a straight hollow tube.

I welded up a trolley for all the electrics the fuel, the blower, etc. This keeps things tidy, and makes it a lot easier to set up for a melt. The grey box at the top is all the electrics, including a NVR stop switch - just in case.

I also need to try Cooking Oil. I can buy that for about half the price of diesel, and it might be fine for melting aluminium.

And some aluminium fell to the floor of the furnace while I was doing a melt. That aluminium never fully melted, it just got to that soft stage, so I think I will put in a taller plinth and move the crucible up higher in the chamber, the bottom is "cold".

Casting aluminium wheels from melted down aluminium wheels

 This was a real pita to mold. It took several attempts, eventually I added a little more water to the sand, and pushed 3" nails into the centers of the high spots to hold things together.

Here you can see one of the many failures. It was fine until I flipped it over to close the mold. By now I've learned to flip the cope above the sand box, rather than above the drag, a lot less cleaning up to do.

The nails helped a lot, but so did adding just a little more water.

I used steel pins to align the two part of the mold, a bit of trial and error on a small sample helped me to figure out the right sized holes. 3d printed pins are ok, but the tend to catch more on opening the mold.

The pour went well, it was a lot of metal probably the second biggest pour I've done.

It's always fun to see what comes out, this was done the next day when it was cold.

Not a bad result, they will need some cleaning up, and I'll need to drill out the hole for the axle.

You can see how much shrinkage there was in the riser, without such a big riser direct attached to the part, it would have had a similar sized shrinkage defect on the hub.

3rd time lucky

 This was cast with a length of steel rod embedded in it. I used a smaller length to make up the drag.

Then once I flipped it over, I pulled the short steel piece using a magnet, and replaced it with one that was slightly longer.

This let me locate the second part of the pattern.

I added a fairly large riser between the sprue and the piece, and it did the job, no shrinkage.

It needs a little cleaning up. The circle over the steel pin is not shrinkage, it is smooth and level, but you certainly can see that the metal solidified a little differently there. If I was doing it again, I'd have a shorter pin, so it didn't come as close to the surface.

Casting the gingery lathe Face plate

 I cast the face plate.

It was cast on a steel mandrel, which I had to drill out quite a bit before I could drive it out with a hammer and punch. 

After a few attempts at molding this, where the pattern lifted the sand in the slots, I tried just pressing 2 panel pins in to each of the slots and that worked.

That gave the slots just enough support to stay in place as I rapped and removed the pattern.

And yes this photo was staged after the event, I was in a hurry to get set up and cast, as the forecast was only good for the morning. The steel mandrel is missing from the pattern here.

I still have a fair bit of work to go before I am ready to machine the face plate.

Pullies and lead screw

https://youtube.com/shorts/6r-MS5sE5aU

I've replaced another 3d printer pulley with a cast one, and also added the apron for the cross slide. The cross slide moves about 0.2 mm for each rotation of the lathe l.

The 3d pullies were starting to fail where the bolt was placed to tighten them on to the spindles.

Shaking out, still no biscuit

 So I added the riser, and the shrinkage is sorted, but I have a small hole in the casting, where the metal didn't flow.

hotter pour next time, I time from when the last piece melts.

I also checked to see if the pattern is wrong. It turns out that this section should be thicker, 3/16, not 1/16. Doh.

At least the riser seems to have sorted the shrinkage.

Close, but no biscuit

The two halves of the pattern are held together by pins, if the pin is too tight, then the pattern won't separate when you split the mold, so you can get breakage around the edges. If the pins are too loose the pattern can slide to one side and things won't line up...

I think that I can clean this up well enough with a file, as it's for a slow speed pulley....