Author Topic: Casting a flywheel in ZL12 alloy.  (Read 1005 times)

Offline Alyn Foundry

  • Full Member
  • ****
  • Posts: 1480
  • North Wales, Great Britain.
Re: Casting a flywheel in ZL12 alloy.
« Reply #15 on: September 14, 2022, 04:24:33 PM »
Hi Lee.

Yes I did have to upload to YouTube. Iíll be interested to see how you intend to core out the passageways for your cylinder head. This is something that hasnít really worked out that well on small scale engines for me. We did have some success when my old foundry was working. They had a special Zircon sand blend that was resin bonded, very low fume. I used it for the Hornsby Akryod Oil engine hot bulb.

 :cheers:  Graham.

Offline A7er

  • Full Member
  • ****
  • Posts: 142
Re: Casting a flywheel in ZL12 alloy.
« Reply #16 on: September 14, 2022, 05:24:49 PM »
Graham.
I have made a mould to produce the core. It is small! It's all a bit of an experiment to see what I can do. The pictures show a water manifold I made some time ago. I cast it in zl12. the water passage is about 10mm dia but it gets very thin towards the left end, no more than 3mm thick, I had to use a piece of twisted steel wire (still less than 1mm in dia) to reinforce the sodium silicate/sand core. The core stood up to the casting even when used with ordinary aluminium poured at 730c. I could also try to produce the core with an epoxy resin/sand mix. That might be a bit stronger than SS/sand. The part was for my half size 1930 Austin Seven engine, which I have now decided should be one third size instead to make it easier to produce the patterns. The work I am doing on the castings should help with the A7 engine. Once I am happy with my casting abilities, I can think about buying a lathe and mill and start learning how to use them. It could take a while!
Lee
Thanks for the info about uploading a video.
Edit. I am also including two more pictures of a ss/sand core for a 30mm dia piston. You can just make out a piece of wire reinforcement in one of the arms which are 8mm dia. The arms make the gudgeon pin holes in the piston to be machined to size later. I have cast a few pistons this way just to test it works. One of the arms looks wonky, it isn't!
A 20p coin is included for scale.

Offline bent

  • Full Member
  • ****
  • Posts: 710
  • Wet side of Washington State, USA
Re: Casting a flywheel in ZL12 alloy.
« Reply #17 on: September 14, 2022, 05:29:55 PM »
Thanks Graham and A7r - I have watched several of Myfordboy's videos, and had not seen him do zinc castings, will go look for them when I get the chance.  I know he had some good videos on preparing your own green sand mix that I'd rewatch when I'm ready, and his demonstrations of the entire process (from patternmaking to molding to casting to fettling and machining) are very good.

Offline Alyn Foundry

  • Full Member
  • ****
  • Posts: 1480
  • North Wales, Great Britain.
Re: Casting a flywheel in ZL12 alloy.
« Reply #18 on: September 15, 2022, 12:00:31 PM »
Good morning Lee.
Nearly 60 years ago a highly progressive school teacher brought in a 1932 Austin 7 open top tourer for us juniors to fix. This was my induction to the world of mechanical restoration. Needless to say over the spring and summer terms we got to drive it on the school playing field. It was such an interesting project that I can still remember us removing the cylinder head, rather brutally, with two pieces of rebar poked through the plug holes!

In later years my good friend Vincent restored a Riley RME for which we made new pistons for using cast Iron dies and loose pieces. I think the die now resides at the Anson engine museum. We made the sprue as an extension of the piston crown to ensure good strength around it and the gudgeon pin bosses.

I wish I could step back in time a little, I would have bought a bag of the sand I used for the Ackroyd project. The resin was activated by heat, the core boxes were made from Aluminium and you just poured it in with a little jug.

 :cheers:  Graham.


Offline Jasonb

  • Full Member
  • *****
  • Posts: 8559
  • Surrey, UK
Re: Casting a flywheel in ZL12 alloy.
« Reply #19 on: September 15, 2022, 01:05:30 PM »
Bent, this one is with the zinc alloy, I put someone in contact with him that was after a 5 spoke flywheel and he did the pattern & cast it for them


Offline A7er

  • Full Member
  • ****
  • Posts: 142
Re: Casting a flywheel in ZL12 alloy.
« Reply #20 on: September 15, 2022, 01:22:27 PM »
Hi Graham.
I have three Austin Sevens. My car that I bought in 1975 and two others left to me by a late friend. I also have a spare engine that I measure to produce the 3D drawings and prints for the model engine I will build.
When I started to get into metal casting I went down the same route as many others did. Sand from B&Q mixed with ground up cat litter for the bentonite. I also used aluminium cans and extrusions for melting and a stainless steel pot as a crucible. I discovered the error of my ways thanks to a local engineer who invited me to watch a pour of 25kg of molten iron. I had proper sand, bentonite and aluminium from him. What a difference! As for core sand, I have a pottery supplier not too far away that I bought some very fine sand from, I think it was over £7.00 per kilo. It didn't last long, he also sold bentonite, again, very expensive. I still use paving sand for core moulds but I filter it through a fine mesh tea strainer, my cores are very small. If I want it a bit finer I will grind the sand with a pestle and mortar. I did wonder about using investment casting medium to make cores.

Offline bent

  • Full Member
  • ****
  • Posts: 710
  • Wet side of Washington State, USA
Re: Casting a flywheel in ZL12 alloy.
« Reply #21 on: September 15, 2022, 04:49:20 PM »
Thanks Jasonb, I just watched that one yesterday during a spare moment.

I'd been taught, or had read somewhere, that you have to pressure-cast zinc, because it has a low boiling point and will tend to develop gas porosity if gravity cast.  But, watching Myfordboy's videos again, I see that he uses tall feeds and risers to help keep the head up on his molds, and from his videos it's pretty clear that any porosity he suffers is minimal.  I do see that he also starts using clamped molds in later videos, to keep the flash and occasional blowouts to a minimum.  Good stuff.

Offline A7er

  • Full Member
  • ****
  • Posts: 142
Re: Casting a flywheel in ZL12 alloy.
« Reply #22 on: September 15, 2022, 11:28:10 PM »
The height above the casting and my pouring basin is barely 25mm, one inch, at the most. I do sometimes wonder if perhaps a bit more height would help. My sprue follows the Ol'foundryman design-ish. 7mm dia at the bottom with a one and a half degree draft to make it a bit wider at the top. Ol'foundryman videos are well worth watching. His pouring basin design is supposed to eliminate air getting into the pour, and his sand and ramming are both top-notch.

Offline bent

  • Full Member
  • ****
  • Posts: 710
  • Wet side of Washington State, USA
Re: Casting a flywheel in ZL12 alloy.
« Reply #23 on: September 19, 2022, 09:44:39 PM »
A7er,

Hmm, interesting.  Watching Myfordboy again, and he seems to use the same high risers on both Al and Zn castings - maybe 6 to 8" or more of height?

- Ben

Offline A7er

  • Full Member
  • ****
  • Posts: 142
Re: Casting a flywheel in ZL12 alloy.
« Reply #24 on: September 19, 2022, 10:07:41 PM »
Ben.
I did use a similar system as Myfordboy when I cast a small aluminium picture frame. It had such a narrow section that the mould wouldn't fill before the metal "froze". The aluminium I was using came from broken engine parts that were probably die cast 90 years ago, not the best metal to use. Myfordboys method got more metal into the mould quicker and it filled. I prefer to use a pouring basin like Ol'foundryman and Swdweeb and others use. Try both methods and see which you prefer.
The picture is of a small, 90mm dia, flywheel I cast recently. It shows the pouring basin and sprue still attached, and the feeder in the middle of the flywheel.
Lee


Offline bent

  • Full Member
  • ****
  • Posts: 710
  • Wet side of Washington State, USA
Re: Casting a flywheel in ZL12 alloy.
« Reply #25 on: September 20, 2022, 08:06:54 PM »
Interesting, will look up those videos too, once I'm ready to become a founder(?). :Lol:

Offline A7er

  • Full Member
  • ****
  • Posts: 142
Re: Casting a flywheel in ZL12 alloy.
« Reply #26 on: September 20, 2022, 11:51:39 PM »
Ben.
As I understand it, all flasks should be clamped in some way because the molten metal will try to "float" the top flask away from the bottom one. I always clamp my flasks. In the beginning of my casting journey I also weighed the top flask down as well as use clamps. I don't use weights now. I watched a Myfordboy video when he forgot to clamp and had spillage of molten metal. I had that happen once, so I sit my flask in a large steel tray just in case.
Lee

Offline bent

  • Full Member
  • ****
  • Posts: 710
  • Wet side of Washington State, USA
Re: Casting a flywheel in ZL12 alloy.
« Reply #27 on: September 21, 2022, 09:51:25 PM »
Yup, ok.  After watching quite a few of olfoundryman's videos, I am a convert.  The surface finishes on his parts are...well, amazing (compared to the run of the mill types on YouTube).  He also has a video where he critiques a lot of other Youtubers, from alloy choices to ramming techniques to...well, everything.  And gives good, cogent, scientific explanations on his whys and wherefores, with references to literature as well.  Low pouring basins with smooth transitions to narrow fill channels, got it.  And pick good casting alloys and don't overheat them.

Offline A7er

  • Full Member
  • ****
  • Posts: 142
Re: Casting a flywheel in ZL12 alloy.
« Reply #28 on: September 21, 2022, 11:14:54 PM »
His name is Martin and he has only recently started to post videos after being ill for a long time. He isn't in the best of health now, so we might not see a casting video from him for a while. Even though Martin pushes the correct way to do things, in his book anyway, he does sometimes display a few lapses. I have watched a few of his videos where he foregoes a pouring basin and just pours the metal down a large sprue. He also took his aluminium over temp to keep it liquid as it poured. What I take away from this is that there is a "right" way to do things. But sometimes the "wrong" way is OK.

I keep aiming for a finish as good as his, but my aim isn't very good!
Lee