Brass or Cast iron

[Fingers]

Hi everybody I am reposting this question, if anybody can help me decide before I start making my piston and cylinder for Jan ridders Marc vertical flame eater. I will be starting these over the weekend. My question is this I am planning to make my piston from cast iron but I am still undecided on choosing brass or cast iron for the cylinder, I would like to use brass as it looks nicer but would cast iron for both work better ?
Cheers

 

[Ken I]

The one thing you must not do is run two identical materials against each other as they are far more prone to galling and siezure.

If you use cast iron for the barrel then a brass piston is the way to go - pretty much anything except cast iron. (ad vice versa...etc. etc..)

Regards,
Ken

 

[Jasonb]

As its a flame licker I would stick to CI as you need the graphite content as a lubricant.

CI on CI is OK just look how many engines with CI cylinders run CI piston rings.

Jason

 

[cfellows]

Virtually all older engines, pre-1950 or so, ran cast iron pistons in cast iron cylinders and used cast iron piston rings. I think a brass cylinder would work as well. I see a lot of flame eaters on youtube that use brass cylinders.

Chuck

 

[Fingers]

Thanks for all the help everyone it seems to me that either will work from what I here so I think i will make it from brass and see how things work out , hopfully tomorrow night I will make it, pictures to follow
Thanks again

 

[Generatorgus]

I've got to jump in here and ask about the same question. I'm about to get really into my Little Brother project and am on the fence as wether or not to use the alum. piston casting, and am thinking about making the piston from the cast iron bar that I left over from my 1/2 scale Henry Ford, which ended up with approx 5/8" bore. I built that piston without rings, just close fit to the steel cylinder, which worked very well. Will cast to cast without rings be OK for the 3/4" bore or is this what Ken was warning about? In my little world, it was easier for me to cut the piston to fit the bore without ring, than to go thru the trouble of grooving to the proper ID for O-rings, or making iron rings. Although, it would probably be a good exprience to do the rings.
GUS

 

[Jasonb]

As the size of the piston gets larger you need to consider its mass, an alloy piston will give a much smoother running engine. CI to CI will not give wear issues but you may have a job getting a suitable seal to give the right amount of compression without getting too much friction due to the whole side of teh pistom being in contact with the cylinder

I would go with the alloy piston about 3-4though under bore size to allow for the greater expansion, CI liner/cylinder and CI rings.

J

 

[Fingers]

Another spanner in the works, my bore size is 24mm should I make piston rings to reduce friction between the ci piston and brass cylinder ?
J

 

[stevehuckss396]

Over at the Model Engine News website there is a real good article about cylinder/piston materials. I could not link to the page but you can search for it. Here is a blurb



Cylinder/piston Material Selection for Model Engines
Created: Jan 29, 2005
Click on photographs to view in more detail


The cylinder/piston fit is one of the most important factors governing the success of a home-built model engine. Material selection wise, the home constructor has a number of choices (despite what the plans may say), but each have their own characteristics, advantages, and disadvantages. The most common choices, in ascending order of experience required, are:

Steel liner, Cast Iron piston
Cast Iron liner, Cast Iron piston
Steel liner, Steel piston
Steel liner, Aluminium piston, Cast Iron ring(s)


It goes on to explain the good and bad for all 4 combo's. If you are still undecided, give it a read.

 

[Fingers]

Thanks again the information from people here seems to be endless

 

[Fingers]

Hi all
Just to let you know I made my cylinder and piston I picked brass for cylinder and ci for piston, I bored out the cylinder and honed out the last .0005 , well pleased with the fit it falls straight thru but if I leave it on a flat surface it takes quite a while to fall to the bottom
8) pictures in my post 'coming along nicely' at the thread Work in progress
J

 

[Blogwitch]

Just a few pointers to your decisions.

The first is that this is a flame licker and any extra friction will stop it running, so don't even think about piston rings.

The other, and I warned you earlier about this, in other posts you raised concerning the same thing, hoping to get some sort of blessing for your decision, is that you have your materials a**se about face.
You should always make your piston out of the softer material if you go for dissimilar materials. It is much easier to replace a piston than a cylinder when they wear.

Jan quoted, I think, a steel cylinder with a CI piston. For your second choice, it must be CI cylinder with a CI piston. Purely on the self lubricating properties of the CI.

Then you asked if it could be made with other materials, and you disregarded all that was told to you by people who have experience of these engines, you went your own way because it looked prettier. Making engines isn't about looking good, it is about getting the right combination of materials together so that it will run. Only after it is running, can you make it more cosmetically acceptable.

How are people supposed to help you when you take no notice of what you are being told by people with lots more experience than yourself.

You might be lucky and get it to run fairly easily, but on the other hand, you might find that you can't get a continuous runner, which is what building an engine like this is all about. Then you will expect us all to give you pointers on how to fix the problems when it doesn't run correctly.

So please, we are trying to help, and there is a lot of experience on this site who CAN help you, but if you choose to go down your own route and not take that advice, then why ask the question in the first place?


Bogs

 

[Blogwitch]

Pat,

Be that as it may, the question was asked, good and correct answers were given, not just by me, and still the wrong way to do it was carried out.

Going by your way of thinking, we should go out of our way, giving up time and energy to give a good answer, and duly expect no notice to be taken of what you have said.

This raises two points, if the person had already made up his mind which way he wanted to go, then why ask, the other is, if that is the case, why should we be bothering to reply at all.

I don't like the word newbie, just a person with less experience than others. So when a person of less experience asks a question, then within reason I personally try to give that person the benefit of what I have been up to all these years, and at least expect that person to follow suggestions or to verify why he didn't actually do so.

I am trying to help, to give a little guidance. If people don't want that, I for one will surely refrain from posting where someone requires help. In fact, consider that now done from now on.


Bogs

 

[Ken I]

WRT my earlier comments on not running similar materials together, cast iron is an exception to this rule due to its self lubricating properties but even here I would refrain from running the exact same grades of cast iron together.

Bogs is right about the brass piston in a CI barrel - but then there is no accounting for taste.

I might also have chosen a brass barrel with a CI piston for appearances rather than endurance - especially in a motor that is mostly for show and seldom runs for apreciable lengths of time.

As far as flame licker motors go - I must confess my ignorance - I know nothing.

Regards,
Ken

 

[Fingers]

Thanks guys
First of all to Bogs if I offended in you by choosing aesthetics over function my apologies and i take it on board. My silly rational behind this choice was I considered what this little engine will do, If i do get it to run,In all honestly I can see this little "hobby" engine probably sitting on a shelf in my kitchen for most of its life,after i have all the fun building and making it, while the odd enthusiastic person wants to see it run for a couple of minutes.
In my opinion which is only my personal opinion i dont think i am building an engine that will run for so long it will wear out,but correct me if I am wrong as i proved already i can be ha,
While i did probably go against some of the advice try and just remember this is my first build like this .Next time i will choose form over function.
May i also take the time to thank Pat j who gave me a lift after reading the first grilling ha but in all honestly i can see why i frustrated him i did ask for the info while i received excellent info i went my own way ,but that is not to say i disregarded it. as you said i am a newbie and if it dose not work i'll just have to make another from cast iron. As they say some people like to learn the hard way.
It seems i might be learning the hard way
Regards J

 

[Fingers]

Thanks Ken i was writing that while you posted.
As you can see that was my thinking i can't see it running for a long period of time, lets hope i'm not wrong.
Regards j

 

[Maryak]

If you can't go:

Over it

Under it

Around it

Negotiation may achieve your aim.

Best Regards
Bob

 

[Fingers]

If everybody followed the norm wouldn't we all be the same :-\
Thanks bob

 

[lee9966]

Personally I treasure the help and suggestions given to questions that anyone asks. I try to learn the right way to do things, or at least why something is the right way.

There are, of course, times when the best advice is not followed for some reason or other. Capabilities of the user, of the available tools, or of available materials are a few that come to mind.

Just my two cents, I would really hate to see any of our experienced people stop helping me us.

Lee (going back to my cave now)

 

[TroyO]

I wonder, if one were to do brass cylinder/brass piston what about hardening the cylinder and annealing the piston so the hardnesses weren't the same?

I believe (But could well be wrong) that jewelers harden and anneal brass/copper/bronze exactly opposite the way you do steel. IE, heat and quench to anneal, heat and cool slowly to harden.

Just a thought.