Stuart Twin Victoria from scratch

[bouch]

Pictures, I have picture. This is the majority of the plugs for the first go around. Coffee cup for ref.

WFIW - I have a complete set of "Victoria" castings, still in the Stuart shrink wrap, aging down in my shop. I got them for a bargain price at a show 20+ years ago. If you want photos of the Stuart castings to compare against your work, let me know.

 

[Jack3M]

5% works as a shrinkage factor. Did a 'test' cast of some bosses yesterday, First time I have ever used Petrobond. WELL worth the money, easy to use and does nice job.

Anyway the pieces were supposed to be 1x13/16 and the are just over those specs leaving enough to machine. So the parts should all be the appropriate size. Waiting on Bronze ingots to arrive.

 

[Jack3M]

Having some issues with simple casts of a test item. Seems parts just don't come out well like the metal (brass) may be solidifying before the entire open space is filled. Possibly not hot enough on the brass, it isn't smoking yet and I read somewhere it should just be smoking at pour temp.

 

[Jack3M]

Was not sure whether to post here or in the Foundry Forum. Having a problem with solidification before the mold has filled. Am using multiple vents, 3 sprues on a 7" flywheel. Metal cooling before it makes it to the next sprue and then won't take more molten metal.

I must admit I don't know the temp at which I am pouring. I just ordered a thermocouple off Amazon due in 2 days. Anyone know a temp to shoot for with brass and with bronze to cast?

Should I somehow preheat my molds? Anyone know how if so?

 

[WSMkid]

Those who I've watched on YouTube do preheat. I'm betting you have done some looking but this guy has been having some success with brass and alu.
A little long winded but not bad.

[ame]https://m.youtube.com/watch?v=20iYekoQUUA[/ame]

Thank you for posting about your trials. I hope to start casting in a year or so once my shop/house is built and I'm settled it.

Following along in the back row,
GJ

 

[Jasonb]

Depends on the exact type of brass but 1750F would be a guide.

Should not need to preheat your petrobond, if your temp is right the sand in contact with the metal will turn into a black skin and need to be thrown away, sand that is not hardened by the heat can be reused. When I last did any fresh sand was sifted over the pattern to get teh best surface finish and then the older reused stuff used to fill the bulk of the moulding box.

 

[WSMkid]

Sorry, I automatically associated printing with investment casting.
Still a good video if you need to kill some time.

GJ

 

[Jack3M]

I don't know the type of brass. It was 12' rod that I cut up. The seller did not know the type so I got a good deal. I suppose I could take the mold and put it in the oven for awhile. But that is only a few hundred degrees. Ambient temp for my shop right now is upper 40's to mid 50's

It also looks like I am getting bubbles in the metal on the exterior, but supposedly brass does not need degassing.

So much to learn. Keeps me going

 

[Jack3M]

My mechanical engineer son was over last night and he feels that the sprues are not large enough, the pour funnel is too small and probably need to change how I am doing this. Now my problem will be I need a larger crucible to handle the larger amount of metal.

 

[Jack3M]

I have a picture!!!!
After many failures, I got several parts made today that are usable. Many things were causing my problems, but I think the most significant was that I was not continuing to heat the melt long enough to get the temp high enough to maintain fluid state during the pour.

It also helps to have huge spigots, passages, and sprues. But when it is right you know during the pour. (Learned that just today). These look in the photo more rough than they are. They will work just fine. Not visibly perfect, but ring true when hit or dropped.

These are bronze/gunmetal. Once my larger crucible gets here, will try the brass again on the flywheels.

 

[Jack3M]

I guess the photo really doesn't look like much with all the scarf and such.

Learned something new today. The better the coat of talc/baby powder (with petrobond you can use baby powder) the better the demold of the plug. Also wiggle the part a bit before pulling.

The plastic (PLA) needs to be as smooth as possible or the chances of a bad pull increase. I found that using a single sided type blade as a scraper works much better than sandpaper which leaves a fibrous covering. Using a combination of hands and rammers to pack the sand works better than just ramming. Hands early on, like on the first packing.

So the new crucible came today. I need to modify some stuff with the forge to hold it. I had just been using firebrick, now I do need to use the real forge. I am pushing the limits of propane with this one.

 

[Cogsy]

If you need your prints super smooth, it may be better to print in ABS then look at acetone vapour polishing them. I've heard you can get very smooth results from that. Myself, I've only just started printing in ABS and it has not been anywhere near as difficult as most online discussions make it out to be. I haven't even contemplated polishing yet though.

 

[Jack3M]

Thanks Al, I did consider that. I also considered an epoxy dip and drip dry. Did neither. Did as above and things are fine. AND I didn't stink things up with ABS.

 

[Jack3M]

Cool beans, had awesome day. Didn't like the way my forge burned with such a large crucible, so I made a new one and it is the best one I have ever had. Melted 8 pounds of brass in 20 minutes with propane burner (Harbor Freight weed burner). I think using the fire bricks works so much better than anything else I have tried. The bottle was even starting to show signs of low pressure and I was expecting to have to change out midway. Not so. Those bricks cost me about $5 each, took 22 + some other stuff to make. Best part is, it can be undone and resized to whatever the necessary size is AND be put away in a corner when not casting.


Then I actually had a flywheel turn out. Will be doing a lot of cleaning up, but it will machine fine. I waited until the brass was beginning to vaporize before pulling dross and pouring. (the spigots are 1" diameter.)


Regardless very pleased with the results. I must say I like the firebrick for kilns better, they are lighter than the type used in fireplaces but are still same size.

 

[Jack3M]

Forgot to show the input end. The distance the burner is out is critical. There has to be enough air movement to burn all the propane. That is a #6 crucible.

Cleaning up the flywheel I found a bad flaw and had to recast it. Looks like this one is okay. Also cast one of the bases in bronze. Got one flaw that I think will not be an issue as it will not be seen due to this being a twin version.

Will post pic of both when the sprues and such are cut off.

 

[Jack3M]

Well don't know if this shows well or not. Cleaned up a couple faces on the flywheel. I have pits. Considering using the TIG and brass rod to fill them, might be easier and more productive than constantly redoing. I still have to make another base and flywheel regardless.

If I were willing to just paint it, I could fill them no problem with body filler and then paint. I think the idea of some shiney brass for the outer rim is probably more visually appealing

 

[Jack3M]

I tried filling with the rod and TIG. It works, but each spot shows as a different color brass, so a no go. And, it was nasty trying to do this, the zinc would oxidize and make things splatter.

 

[Jack3M]

Cool beans. I got my flywheels. Moving to my last large pieces, the cylinders. These require a core to have the hollow part. I tried first just using the sand, but kept getting a void inside the cylinder above where the core is.

I guessed it was gasses escaping from the binder and such in the sand, so yesterday I made a core and burned it to a glowing crisp as I melted a bunch of dross/slag that still had quite a bit of metal in it.

So today I hope to see if this method fixes that problem.

Also, the tiny parts are really difficult to extract from the sand without damage to the mold. As one of the provided links was about lost PLA casting I researched that and will be giving that a shot in the next few days. Going to try using plaster of paris instead of real investment just for a try

 

[WSMkid]

Please document your findings with the lost PLA. I'll be following along.
Best of luck.
GJ

 

[Jack3M]

Please document your findings with the lost PLA. I'll be following along.
Best of luck.
GJ

Okay will do.