Building the JU-02 gas producer

[racket]

Hi Anders

Yep, never hurts to have a spare when doing our sorta work ;-)

Cheers
John

[mitch]

Anders,
Pretty sweet build thread so far, cant wait to see where the build goes!

A question about your free power turbine, what do you use for bearings for the free power stage? Are they hydrostatic/dynamic oil fed bearings or some sort of sealed ball bearing?

[Johansson]

Sept 30, 2015 17:38:52 GMT -5 mitch said:

Anders,
Pretty sweet build thread so far, cant wait to see where the build goes!

A question about your free power turbine, what do you use for bearings for the free power stage? Are they hydrostatic/dynamic oil fed bearings or some sort of sealed ball bearing?

I use hybrid ceramic bearings with stainless ball cages, they are lubricated/cooled with a 1mm oil jet nozzle pointing at each bearing.

[Johansson]

I have finally decided on the design of the diffuser plate rear side.



A pair of guiding pins will secure the two parts together when making the sand pattern.



Next up is to see if the printed pattern will release from the petrobond sand or if I need to make the surface smoother first, I hope that I can use an untreated pattern will work since it makes pattern making much easier.

Cheers!
/Anders

[Deleted]

Looking good, would soft wax help

[racket]

Hi Anders

Pattern is looking good :-)

Just one thing , have you considered how you are going to hold the diffuser casting for machining .

With the 5 bracing pieces you won't be able to machine the rear boss or hold it in a 3 or 4 jaw chuck , you might need to add a "sacrificial" cylindrical boss on top of what you have .

I normally accurately position the raw casting to a face place and turn the rear boss first, this can then be simply held in a 3 jaw chuck to machine the front of the diffuser , the diffuser is then fitted to a jig to machine off the sacrificial boss and turn the thrust bearing pocket and mounting face for the shaft tunnel .

Hopefully the pattern releases smoothly , it'll certainly save a lot of preparation time .

Cheers
John

[metiz]

If you dust your mold with talcum powder, it might seperate more easily

[Johansson]

The idea is to use the digital scales to find the center and drill the bolt circle with the cast part laying flat on the mill table, then make a mounting jig for the rotary table and bolt it to.

I did a quick and crude test with the petrobond sand last night, I could have rammed it better but still got pretty good results. A couple of edges that fell away when I pulled the pattern but I think better ramming and sifting the first layers of sand will help.

I tried talcing the pattern but the plastic is so slippery that the talc didn´t stick to it, promising!

[Johansson]

Here are the pics from the test with the raw printing in the petrobond sand.



The flasks (wooden frames) are much too large, I didn´t ram the sand hard enough and I should have sifted the sand closest to the pattern.



With a pair of wooden screws and some careful tapping with the backside of a screwdriver I pulled the pattern out of the sand with only a couple of minor breaks in the sand around the wedges.



I consider this a success, if I do things properly the next time I am sure it will turn out much better. First I need to make a pair of smaller flasks though since the 25 kg sack of petrobond sand won´t fill up both of these ones.

Cheers!
/Anders

[racket]

Hi Anders

Thats impressive :-)

Cheers
John

[Johansson]

It sure looks promising, with the electric furnace and the ability to 3D print casting patterns while sitting in the sofa scratching my ass I am one step closer to a 100% complete workshop.

[smithy1]

Oct 14, 2015 14:53:27 GMT -5 Johansson said:

It sure looks promising, with the electric furnace and the ability to 3D print casting patterns while sitting in the sofa scratching my ass I am one step closer to a 100% complete workshop.

Are you able to "3D print" yourself scratching your ar$e..??

Smithy.

[Johansson]

Arrrrgh! I forgot about this build thread and posted the JU-02 build updates in the landspeed bike thread instead, bugger!

Oh well, here is the interesting stuff so far:

Last night I made a pair of suitable sized flasks for the JU-02 compressor diffusor pattern and tonight I made the sand pattern.



I sifted the sand closest to the pattern to get a smooth surface finish for the casting.



I used copper tubing to form the downpour and the vents, the downpour fits to the thickest part of the pattern that solidifies last.



Baby powder is brushed on the surface so the sand won´t stick together when I ram the sand in the second flask.



Looking really good! A couple of minor cracks on the diffusor wedges but that can easily be fixed on the cast part. Time to pull the second pattern from the sand.



I am very pleased with how easy the 3D printed PLA patterns release the sand, I haven´t even bothered to smooth out the raw printed surface with sand paper.



The plan is to cast the part on Friday, keep your fingers crossed!

Cheers!
/Anders

-------------------

This morning I got up early to start the electric kiln, then I drank three cups of coffee and are a bunch of sausage sandwiches while it was heating up. With the crucible at 700°C I started loading it with aluminum and an hour later it looked like this:



I added flux to the melt to make it pour better and degassed it with gasseous nitrogen to pull oxygen from the melted aluminum, then I removed the dross and let the crucible heat up to 780°C before I poured it.



Exciting to say the least! I have had my share of more or less faulty casting attempts so it would be nice I could see some progress.



The result was very good, I cut the sprues off and heat treated the part in 180°C for 6 hours so it will be easier to machine later.



The only flaw is a small bubble on the mating surface to the bearing tunnel, but I can easily weld it up with the TIG welder so no big deal.



The 0.2mm layers from the 3D printing is clearly visible, very good details with the petrobond sand in other words.



I celebrated the success with a 31km running trip to a nearby hydro power plant and back and spent the rest of the day with my family, a Friday cannot possibly be much better than this one.



Here is the video from the casting:



Cheers!
/Anders

-------------

Why does this feel familiar? Luckily I won´t have to mill the diffusor from solid this time like I did with the last engine.



The diffuser was warped a bit bit it straightened out after I cut the support wedges that must have bent the plate during casting somehow.



Drilling the centrum hole and the bolt circle, a digital readout for the mill is a very useful tool for things like this.



I´ll use four M10 insex 12.9 bolts to hold the engine core together.



Here I have just finished countersinking the holes for the insex bolt heads.



I had to make a jig to fit the diffuser plate to for the next job.



It was past midnight when I had finished the jig so I called it a night after realizing that my lathe was too small for this job.



Today I used some spare time at work to machine the compressor wheel recess, my job is as a mechanic at a local heating plant so I have a workshop set up there as well with a slightly larger lathe.



After some turning the recess was made with a bit of extra clearance for heat expansion and bearing play.



The compressor wheel looks like it was made for this.



I can´t exactly complain about the casting quality.



Cheers!
/Anders

[jetjeff]

Amazing work!! Nice job!!

Jeff

[Chuks]

hi BOSS.... what a wonderful engine, I have been practicing how to operate latte and milling machine so I can start my building thread as you advised