Author Topic: Making the cylinder head, design, patterns and casting.  (Read 3205 times)

Offline A7er

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Making the cylinder head, design, patterns and casting.
« on: October 03, 2022, 09:05:50 PM »
This picture is a snapshot taken from my cad programme. It is the engine I will be making the cylinder head for.



I have left one of the flywheels off to show other psrts.
This is the pattern for the head on the left, the one on the right has a deeper water jacket.



This is the mould for the water jacket.



The mould has been assembled and filled with find sand with epoxy resin as the binder at 10% by weight. I tried to make the cores with sand and sodium silicate as the binder but I can't get the hang of it.



After several hours the resin had set enough to get the core out of the mould. It was a bit of a struggle, but worse was yet to come.



The middle part that forms the spark plug and valve guides had to be hammered out of the mould. Luckily the core and mould survived.

« Last Edit: October 04, 2022, 08:17:07 AM by A7er »

Offline A7er

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Re: Making the cylinder head, design, patterns and casting.
« Reply #1 on: October 03, 2022, 09:29:44 PM »
The mould and the core with a five pence piece for scale.



This is one half of the core that will form the combustion chamber in the head, with locating channels for the inlet and exhaust cores. Resin sand mix again.



The simple mould for making the inlet and exhaust tract cores.



I have filled areas of the middle section of the water core mould to try to make it easier to remove from the sand core.



This picture shows some of the reinforcing wire I used in water jacket core. The twisted piece hold the front section together, the wire sitting on the middle section is to hold the thinnest part of the water core together. This piece of wire and the sand can be removed (I hope) from the casting via the raised section of sand at the back of the core which should form a hole in the top of the head. This hole will be covered by the valve rocker post.



I hope to be casting the head soon.

Offline Jasonb

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Re: Making the cylinder head, design, patterns and casting.
« Reply #2 on: October 04, 2022, 06:57:07 AM »
It will be interesting to see how it comes out.

As a point of interest of all the open crank type engines I have made from kits none have water galleries and all the ports and passages are machined in. Only the Ball hopper monitor had some holes to be drilled for water to pass down from the hopper to the cylinder jacket.

Offline A7er

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Re: Making the cylinder head, design, patterns and casting.
« Reply #3 on: October 04, 2022, 08:16:47 AM »
Jasonb,
I did design the engine with a hopper but changed it when I realised that I would need a support for the water jacket. I might still return to the hopper and just blank off the water inlet with a plate. Making this engine with castings is my way of getting experience in the design through to casting process. I don't even know if it will work, but I am enjoying it!
Lee

Offline Jasonb

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Re: Making the cylinder head, design, patterns and casting.
« Reply #4 on: October 04, 2022, 09:12:56 AM »
I was just mentioning it as most models don't seem to need the cooling cavities in the head and seem to run OK be they hopper, tank or air cooled.

I've also just noticed that you have both water connections at the top. It's usual to have the incoming cooler water enter at the bottom and the heated water exit at the top which helps create the thermosyphon that gets the water flowing. Even if you are going to add a water pump the top out bottom in will give better flow within the engine.

Offline A7er

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Re: Making the cylinder head, design, patterns and casting.
« Reply #5 on: October 04, 2022, 01:41:28 PM »
Jasonb,
That's a good point about both water connections! I will cast the head as is, and look at altering the design. I would like to go back to a hopper, it's more in keeping I think. If I move the head connection to the bottom then I can just blank it off or maybe fit a drain tap. I also made a new water jacket this morning using 5% resin by weight. I still seems a bit saturated to me so I will drop it down to 1% with my next try.
Lee

Offline A7er

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Re: Making the cylinder head, design, patterns and casting.
« Reply #6 on: October 04, 2022, 04:42:23 PM »
I cast the head today using aluminium from a Renault car wheel. I poured the metal at 730c, but I think I should have let it sit a bit longer. But that wouldn't alter the fact that the casting was a failure! These two pictures show the head after cutting off the gating.




The picture above shows that a lot of loose sand fell into the mould when I closed it up.

I cut the head in two so I could see how the insides had cast.



In this picture the arrows at "A" show the water passages. "B" a pocket in the aluminium, I think it's called an inclusion. "C" shows where the metal didn't flow over the top of the inlet and exhaust tracts. That could be down to the metal not being hot enough by the time it got there. I will alter the mould so that the metal is at least 3mm thick. At the moment it is barely 2mm.



I have learnt a few things from this pour, so I am not too disappointed. A re-design is in order.
Lastly, should I make the pictures a bit bigger?
Lee

Offline crueby

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Re: Making the cylinder head, design, patterns and casting.
« Reply #7 on: October 04, 2022, 04:47:20 PM »
Great progress on a complex part.   :popcorn: :popcorn:

The picture size is fine, though a bit larger could help a bit on fine details.

Offline Jasonb

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Re: Making the cylinder head, design, patterns and casting.
« Reply #8 on: October 04, 2022, 04:50:01 PM »
Yes a bit bigger would be good 640 wide is often used for forums. White background can also make the subject a bit dark as the camera tends to read the background and adjust brightness to suit.

The cores certainly look to have worked OK.

Offline Vixen

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Re: Making the cylinder head, design, patterns and casting.
« Reply #9 on: October 04, 2022, 05:11:57 PM »
I cast the head today using aluminium from a Renault car wheel. I poured the metal at 730c,
Lee

Car wheels are usually a pressure die-cast alloy. When gravity casting, you may need a taller ingate header, to add more 'weight' to help with filling the mould cavity.

Mike
It is the journey that matters, not the destination

Oh! sod the journey, lets hit the bar and pool instead.

Offline Alyn Foundry

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Re: Making the cylinder head, design, patterns and casting.
« Reply #10 on: October 04, 2022, 05:33:11 PM »
Hi Lee.

Some good results considering it’s the first time with the pattern and cores.

I used to use a temperature of around 850 degrees to pour, metal degassed prior. A good covering flux is recommended to reduce gas absorption. How quickly are you getting up to melting your metal? The key is rapid heat to reduce the gas absorption, these gasses cause porosity.

As Jason pointed out earlier the use of cored water ways at scale can be very tricky. The stresses increase exponentially when you start using Iron!

I’ve been following your progress quietly and I would definitely recommend using taller sprues to increase the “ head “ which will improve the castings integrity.

 :cheers:  Graham.


Offline A7er

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Re: Making the cylinder head, design, patterns and casting.
« Reply #11 on: October 04, 2022, 08:38:10 PM »
Thanks for the comments everyone. I will increase the picture size which at the moment is 700 pixels wide by 525 tall.
With something as "tall" as the head it was near to the surface. I cast an aluminium flask when I got comfortable with casting, I should have made it taller. I could always try what Myfordboy does and use cans to get a bit more height, but it does mean pouring down the spout as it were rather than using a pouring basin.

I forgot to mention the way the epoxy resin sand performed. A lot better than I expected is the answer. There was a smell, but nowhere near as strong as spray paint for instance. My mix was 10% of resin by weight to sand. 60g of sand, 6g of resin, 1 and a bit g of hardener. So actually a bit over 10%. I didn't use all the resin and the set sand was very strong. I could drop the water core from a foot onto a hard surface without damage. After casting the cores all crumbled using a masonery bit in a battery drill, gently. But getting into all the nooks etc through the little access holes was a bit fiddly. A mistake I made was trying to wash out some of the crumbled sand. It would have been better to blow it out. Before I try another casting I will get some bowden cable. The flexible wire down the middle, not the outer bit. The middle bit works well in an electric drill. The brake cable from a bicycle should do. I am now redesigning the head to get an easier to cast pattern and cores. It will be roughly the same shape.
Lee

Edit.
Graham. I have a small home made electric foundry of about 1800 watts. I did the whole casting process in less than an hour. And that includes striking the mould, cutting off the sprues and cleaning out the cores. I rushed it didn't I. I should have left the aluminium for another 20 to 30 mins. I don't use any flux or degassing with my simple setup. I wonder if it would help? I am very pleased with the way the cores all seem to have lined up and stay in place. I expected the water core at least to float about a bit.
« Last Edit: October 04, 2022, 08:44:25 PM by A7er »

Offline Alyn Foundry

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Re: Making the cylinder head, design, patterns and casting.
« Reply #12 on: October 05, 2022, 12:48:37 PM »
“ Rushed it ? “ on the contrary, Aluminium needs to be dropped as quickly as possible. We used to have the moulds prepared before starting up the furnace. A well insulated metal tube and a large Propane torch were the tools. For small jobs we would use a proper Crucible but for larger castings we would use metal pots that had been painted with a Lime wash to reduce metal contamination. This isn’t really a problem for the amateur, backyard foundry but in industry metal contamination can be a serious problem.

Using sprue extensions can help greatly. Empty tin cans, with both ends removed can be set around the sprue rod and rammed as you’re finishing the Cope. Don’t forget to put a weight on the top. Pouring down the sprue directly into the mould is quick and ensures the metal is really hot. An extra detail is that the sprue drops onto a “ runner bar “ placed in the Cope with the gates and runners coming from it to the cavity. Any sand picked up by the pour will naturally rise to the top and be held in the main runner while the slightly lower gates feed the casting.

 :cheers:  Graham.

Offline A7er

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Re: Making the cylinder head, design, patterns and casting.
« Reply #13 on: October 05, 2022, 04:57:54 PM »
I will try the tin can riser on my next pour. I've re-designed the head with better location for cores, and the water core is easier to make too. Really looking forward to casting it.

Many thanks for the advice. Without giving any secrets away, which part of North Wales are you in? My late mother was born in Tonypandy in the Rhondda vally.
Lee

Offline Alyn Foundry

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Re: Making the cylinder head, design, patterns and casting.
« Reply #14 on: October 05, 2022, 05:04:39 PM »
A picture’s worth a thousand words….

Plate HA4. Grade M.  ( Iron )

Shows a half plate containing 2 piston and 2 crank discs for my half scale Robinson hot air engine. Last used in 2006.

Along side is my, personal runner bar for “ loose “ work. Note the bulky parts of the castings are in the Drag. The first picture is of the Cope side. The sprue would be “ tubed “ down to the oval shape. The second picture is the drag side. Showing the runners that intersect the runner bar. If you look closely you can see the runners are “ nipped “ down just before the casting. This helps to break away the casting from the runner without damaging the casting proper.

 :cheers:  Graham.

I see our posts crossed Lee.

That’s South Wales, I’m almost on the border of Cheshire, 12 miles West of Chester.