Author Topic: Making the cylinder head, design, patterns and casting.  (Read 7790 times)

Offline ddmckee54

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Re: Making the cylinder head, design, patterns and casting.
« Reply #75 on: October 31, 2022, 07:07:27 PM »
Your head design is probably OK, but you might want to consider a large feeder in the middle of the head.  If your sparkplug is going to be on top, you'd be machining there anyway - so that might be a good spot?  That would allow the feeder to stay liquid and feed that big lump as it cools and freezes. 

I think you are gating into either the intake or the exhaust, then the feeder is on the opposite side.  I'm wondering if gating to both the intake and exhaust, might not be a good idea?  Most of the failures so far have involved the opening farthest away from the sprue not completely filling.  If you were filling from both of those openings, then where the fronts combine would be in that great big lump in the middle - wouldn't it?  You'd be feeding hot metal in from both sides so both of those areas should be able to fill before filling the rest of the head - I think?

Kudos on the finish.  I've got a small electric jewelry furnace and I've been debating whether to use the wheelium which I've got, or to get some ZA12.  I think I'm going to start looking for some ZA12.

Don

Offline A7er

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Re: Making the cylinder head, design, patterns and casting.
« Reply #76 on: October 31, 2022, 07:21:19 PM »
Hi Don.
It might not go by the name ZL12 in the part of the world you are in. If you are in the UK, like me, then it can be bought from Artisan foundry shop.

Offline ddmckee54

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Re: Making the cylinder head, design, patterns and casting.
« Reply #77 on: October 31, 2022, 09:05:01 PM »
I'm on the OTHER side of the pond, in Iowa.  I could probably buy it there to...  But to quote Peter Plunkett in High Spirits, "The number of stamps alone is mind boggling."

Offline Admiral_dk

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Re: Making the cylinder head, design, patterns and casting.
« Reply #78 on: October 31, 2022, 10:28:24 PM »
Quote
But to quote Peter Plunkett in High Spirits, "The number of stamps alone is mind boggling."

 :lolb:   :lolb:   :lolb:

I have never done any Casting - so I can't comment on that bit - but I following to see if I get any wiser  :cheers:

Per

Offline john mills

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Re: Making the cylinder head, design, patterns and casting.
« Reply #79 on: October 31, 2022, 11:50:23 PM »
would the centre where it is sinking ,would that be a place to use a chill make it start cooling  there      sooner rather than trying to feed it and keeping it hot .
john

Offline A7er

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Re: Making the cylinder head, design, patterns and casting.
« Reply #80 on: November 01, 2022, 11:32:12 AM »
Hi all.
I have been thinking about the gas bubble that has caused such poor castings recently. I think I have a culprit. My small bottle of CO2 has been running low recently and ran out before I could harden the last core I made. I let that core self harden overnight and used it the next day. The casting was very bad. So, maybe a small amount of sodium silicate, a liquid, was present in part of the core. The outer shell of the core had hardened, but maybe the middle was still wet? There is no real reason for a gas bubble to be produced by the pour. The metal was around the correct pouring temp, the sprue and gating into the mould was clear, and the riser gave metal a good exit point. The green sand was also good, hardly any moisture in it. In fact I felt it was too dry as I was ramming it, but it was OK.
I found some sodium silicate sand cores from an old casting yesterday. I didn't need them so I broke them up. They were at least 6 months old, and as hard as stone. I had to use a hammer on one of them, so maybe the ss/sand mixture hardens more over time?

Food for thought.
Lee

Offline ddmckee54

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Re: Making the cylinder head, design, patterns and casting.
« Reply #81 on: November 01, 2022, 03:34:40 PM »
I just looked up baking SS cores on the Home Foundry forum and found this in one of the threads, "Baking after gassing adds green strength and drives out water."

Looks like researching baking SS cores could be another rabbit hole to go down.

In the same thread that I got that quote from, HT1 provided a link to the Navy Molder's manual on Google books.  http://forums.thehomefoundry.org/index.php?threads/sodium-silicate-shakeout-additives.888/#post-20454
That could be an interesting read on a cold winter's night, LOTS of handy information.

Don
« Last Edit: November 01, 2022, 03:40:52 PM by ddmckee54 »

Offline vtsteam

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Re: Making the cylinder head, design, patterns and casting.
« Reply #82 on: November 01, 2022, 06:58:45 PM »
Hope the following observations are helpful.

1.) Zinc shrinks a lot.

2.) Upper horizontal surfaces like the top of your casting will generally show a shrink depression unless fed properly. It's the hottest location in the casting, so it ends up feeding the rest, unless fed itself.

3.) A useful riser needs to be more massive than the thickest section of your casting in order to retain molten metal to feed that area. Your head design puts the most massive section at the center of the top, which amplifies the problem, so shrinkage there will be greatest.

4.) The small risers on your cylinder head bosses look too small to feed anything, and may actually be a liability, drawing metal.
« Last Edit: November 01, 2022, 07:06:27 PM by vtsteam »
Steve

Offline A7er

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Re: Making the cylinder head, design, patterns and casting.
« Reply #83 on: November 06, 2022, 07:52:51 PM »
Hi all.

I took some time off from casting to re-think the situation. I am giving up trying to make an engine and falling back on my old hobby of vintage cars.
I am now in the process of re-arranging my garage/workshop to lose a bit of workbench and move an Austin Seven out that needs a lot of work, and an Austin Seven in that only needs a bit to make it driveable.

I think I was close to getting a good casting with all the advice you had given me, but ahead was a great deal more learning when it came to maching the casting etc. And also the expense was becoming a serious consideration. I would need to build a bigger foundry, buy a lathe and milling machine plus all the tooling, and dispose of at least one Austin Seven to make room for all that.

Thanks for your help.

Lee.
PS. If you are ever in my part of Cornwall ( Illogan) drop in for a cuppa!  :ThumbsUp:
PPS. My new pastime is to make 4 scale models of my Austin Seven in 1/10th scale (it's so easy to divide by 10). Display case only! One for me and one for each of my sisters. After that, who knows.



Offline vtsteam

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Re: Making the cylinder head, design, patterns and casting.
« Reply #84 on: November 07, 2022, 07:15:06 PM »
Darn. Wanted to see it come out pretty....
Steve

Offline jirvin_4505

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Re: Making the cylinder head, design, patterns and casting.
« Reply #85 on: December 01, 2022, 12:49:46 PM »
I’ve been researching cores.  Just re read through thread lots of good info even if the result didn’t turn out

Thought this might be usefull info for this thread

<a href="https://www.youtube.com/watch?v=_M0DxxlIK3I" target="_blank">http://www.youtube.com/watch?v=_M0DxxlIK3I</a>

Cheers Jeff

Offline bent

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Re: Making the cylinder head, design, patterns and casting.
« Reply #86 on: December 01, 2022, 11:36:08 PM »
Those molds look great from the outside.  It does look like the cores are giving you fits.

ZA12 is the 12% Alum. alloy?  Try ZA4 (4% Al) instead?  It's supposed to have near zero shrinkage...

Offline A7er

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Re: Making the cylinder head, design, patterns and casting.
« Reply #87 on: December 02, 2022, 12:36:02 AM »
Jeff. That is a video I watched a few times, his cores were a lot better than mine!

Bent. No more casting in the foreseable future. Nearly all my equipment/sand/metal has now gone. The model car is coming along nicely though.

 

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