Total amateur, but learning!

[lee webster]

Hi all, My name is Lee and I live in Illogan, Cornwall in the UK. I have decided that I need a new hobby. My old hobby was Austin Seven vintage cars. I have three. 2 1930 based A7 specials and a 1932 A7 saloon. I will be selling them sometime and will attempt to make a working model of a 1930 A7 engine. I am designing the castings on my computer trying out some cad programmes. I use FreeCAD which can do almost anything, especially annoy the wosname out of me! I also use Solidworks. I have managed to crash Solidworks a few times, not as often as FreeCAD though. I wanted to make a 1/4 scale engine but soon realised that was super tiny (73.25mm long x 33.5mm wide for the head). I then went on to 1/2 scale, that seemed a bit big so I settled on 1/3 scale. I have now gone back to 1/2 scale for my first attempt with the option for 1/4 and 1/3 a possibility. I have watched many video's on Youtube about castings, mainly of aluminium, and some of cast iron. I would prefer to make the block and head from cast iron, but that might be for later on. I think aluminium will do for a start, with cast iron cylinder linings. Should I use a harder metal for the valve seats? It's not an engine that will be run every day, but I don't want to destroy the block (side valve). I am also looking at buying a small lathe and a milling machine (Chinese?) and also a 3D printer to help with making the moulds. I am lucky to have some full size drawings and a spare engine to measure.
Lee.

 

[tornitore45]

Welcome to the hobby or the obsession or the disease.
Casting iron is not for the timid, you will be the judge of your abilities.
Aluminum valve seat have worked fine in many model engines mounted on airplane. What in US is known as AL 2024 works even better.
Personally I prefer to press fit bronze valve cages for 2 reasons
1) Is easier to make a proper concentric seat
2) If I screw up I can remake the cage and avoid remaking a complicated head.

 

[Cogsy]

Welcome Lee. There was a member building a 1/3 scale A7 engine a couple of years ago although the thread hasn't been updated for a while. You can have a look at it here : https://www.homemodelenginemachinist.com/threads/1-3-scale-austin-seven-engine.19490/ . Looks like a daunting project for a first build! Good luck.

 

[lee webster]

I like the idea of bronze valve cages, I will look into that. With what I have learned so far I think I will put cast iron to one side for a while. Aluminium looks to be an easier metal to melt, and I can make a one piece mold using a 3D printer and investment plaster. It is a shame to loose the 3D print each time, but how many of these could I make!
Looking at the 1/3rd scale A7 engine has really brought home to me how much work I have ahead. When I more experienced in posting on the forum I will start a thread about my progress.
Lee

 

[Harry.]

Welcome to the forum. This forum and Youtube are great sources of information, 'business of machining' podcast is also interesting.
See you around the forum.
Harry

 

[abby]

Hi Lee and welcome to the forum.
You have obviously given some thought to your project but having run a lost wax foundry for several years I think you may not realise the problems encoutered burning out printed patterns.
Far better results can be obtained by taking silicone rubber moulds from your printed patterns then casting in wax to produce your production patterns.
This route allows for several castings to be produced from the one printed pattern.
The burn out process requires a kiln and carefully followed temperature regime to avoid destroying the mould.
Pouring cast iron into plaster based investment is not recommended,the maximum temperature for a gypsum based mould is 1250°C , you will need a higher temperature than this to run iron.
This means using phosphate based investment or ceramic shell.
If you are using plaster investment then gun metal or silicon bronze would be the best choice for the castings.
Dan.

 

[ddmckee54]

It is a shame to loose the 3D print each time, but how many of these could I make!

It's not how many CAN you make, but rather how many do you HAVE to make until you get a usable casting - with a spare or two in case there are any Boo-Boo's during machining. Some of these patterns will take many hours to print and you are NOT going to want to do that more than once.

There parts were sand cast originally and you already plan on 3D printing the patterns, have you thought about using a bonded sand for the molds and cores? This eliminates the need for the burnout kiln and complicated burnout schedules needed for lost wax, or lost PLA for that matter. Sodium silicate would be the simplest bonded sand, but there are others. There are a number of YouTube videos out there about using sodium silicate to make cores and molds.

Don

 

[bluejets]

We use a bonded sand at least for the cores.
Don't forget the "pills" when doing aluminium casting.
We usually use a high grade of scrap such as pistons or similar and the pills are introduced 1. to make the rubbish float to the top and the second to eliminate the hydrogen which causes holes in the casting.
I'd tend to steer away from cast head for that particular reason.
Nothing worse than putting in 20 hours or more only to find an irrepairable blow hole.

Bronze valve cages here also.........
Example from my little 4 cylinder 25cc engine.

 

[Cessnadriver]

Bluejets
What are you referring to when you mention “pills”. I haven’t started any casting processes yet but close.

Thanks

 

[bluejets]

Bluejets
What are you referring to when you mention “pills”. I haven’t started any casting processes yet but close.

Thanks

They're tablets literally that one introduces when the crucible has heated right up to temp and contains liquid aluminium.

As I said , one brings all the slag to the top for easy removal and the other, removes the hydrogen gas formed when aluminium is melted.
If not used, obviously there will be bits of rubbish in the casting, usually in an inappropriate place and holes within the casting from the hydrogen.

Can't remember the name of them just offhand. I'll get on to George, he'll remember for sure.

 

[TSutrina]

You can find a few youtube videos using a printable wax and PLA for investment casting. PLA leaves a residue in the casting. The printable wax is Moldlay by Lay-filaments.

 

[awake]

Bluejets
What are you referring to when you mention “pills”. I haven’t started any casting processes yet but close.

Thanks

Cessna, if you haven't yet, find MyfordBoy on YouTube and watch his casting videos - very, very informative. Initially he used potassium chloride and washing soda, each wrapped in a bit of aluminum foil, to act as flux and de-gassing agents. I'm guessing the "pills" are the commercial equivalent. I haven't yet tried my hand at casting, but very eager to do so ...

 

[master53yoda]

I have found that calcium Hypochlorite in spa shock works best for degassing aluminum. I had a problem with bubbles forming in a flywheel that I was working on and it resolved the problem. I was also using a SS sand mold using a catalyst as a hardener. this is the thread with the information. HT1 is the source of the Calcium Hypochlorite information.
http://forums.thehomefoundry.org/index.php?threads/gas-bubble-problems.77/
Art B

 

[bluejets]

Bluejets
What are you referring to when you mention “pills”. I haven’t started any casting processes yet but close.

Thanks

Sent George a message and below was his reply.....

Coveral 11 is a Foseco flux for aluminium and the degassing tablets are Nitral 10 again from Foseco. The degassing tablets are 200grms each and can be broken up into small lumps.

Cheers Jorgo

 

[Shopgeezer]

A metal casting group I belonged to many years ago used chlorine swimming pool tablets for degassing. They were doing large aluminum pours for homemade machine tools.

 

[werowance]

hmm, I am terrible at casting but I was shown to use urinal cakes. the smell good round things you put in toilets. break them up to pieces and put a piece or 2 to degass and bring the crud to the top. I was told only to use the white bleach smelling ones. can anyone expand on that?

 

[awake]

Well, if it helps keep the urinal clean, just think what a great job it will do cleaning up the molten aluminum!

But seriously, there is a common theme in the last several posts - potassium chloride, calcium hypochlorate, chlorine swimming pool tablets, bleach-smelling urinal cakes - sounds like chlorine may be a key ingredient. Of course, being a total neophyte with regard to casting, I have no idea if that is true, or if so, which compound of chlorine is actually best / safest / most effective ...

 

[Bazzer]

Hi all, My name is Lee and I live in Illogan, Cornwall in the UK. I have decided that I need a new hobby. My old hobby was Austin Seven vintage cars. I have three. 2 1930 based A7 specials and a 1932 A7 saloon. I will be selling them sometime and will attempt to make a working model of a 1930 A7 engine. I am designing the castings on my computer trying out some cad programmes. I use FreeCAD which can do almost anything, especially annoy the wosname out of me! I also use Solidworks. I have managed to crash Solidworks a few times, not as often as FreeCAD though. I wanted to make a 1/4 scale engine but soon realised that was super tiny (73.25mm long x 33.5mm wide for the head). I then went on to 1/2 scale, that seemed a bit big so I settled on 1/3 scale. I have now gone back to 1/2 scale for my first attempt with the option for 1/4 and 1/3 a possibility. I have watched many video's on Youtube about castings, mainly of aluminium, and some of cast iron. I would prefer to make the block and head from cast iron, but that might be for later on. I think aluminium will do for a start, with cast iron cylinder linings. Should I use a harder metal for the valve seats? It's not an engine that will be run every day, but I don't want to destroy the block (side valve). I am also looking at buying a small lathe and a milling machine (Chinese?) and also a 3D printer to help with making the moulds. I am lucky to have some full size drawings and a spare engine to measure.
Lee.

Are you the same Lee Webster asking about 3D printing over on the ME forum? If so I will answer your question here.

Regards

Barrie

 

[bluejets]

Well, if it helps keep the urinal clean, just think what a great job it will do cleaning up the molten aluminum!

But seriously, there is a common theme in the last several posts - potassium chloride, calcium hypochlorate, chlorine swimming pool tablets, bleach-smelling urinal cakes - sounds like chlorine may be a key ingredient. Of course, being a total neophyte with regard to casting, I have no idea if that is true, or if so, which compound of chlorine is actually best / safest / most effective ...

https://www.artisanfoundry.co.uk/product_info.php?products_id=317

http://www.ceraflux.com/ceraflux-11.php

Google helps....

 

[a41capt]

I can tell you, that as a Toxicology trained Firefighter/Paramedic and HazMat Technician, chlorine once inhaled is the end of your lungs. When in contact with water (the alveoli in your lungs), the chlorine gas liberated by the heat reaction will form hydrochloric acid and hypochlorus acid. Both agents have a pH in the 0 to 1 range, and tissue damage and non-cardiac pulmonary edema rapidly ensue.

Of course, if you are taking the usual precautions of excellent ventilation to protect against metal fumes, as well as other unknown agents in the pour, this shouldn’t be an issue. Be advised that even when heated, chlorine gas is approximately 2 1/2 times heavier than air sometimes making it hard to ventilate, and the US OSHA guidelines for an immediately dangerous to life and health value (IDLH) is only 10 parts per million. For all you math geeks out there, that is .001% in air...

Be careful please!