Make a Crank Case out of Brass?

I'm thinking brass wouldn't shed heat very well either.
Ian bushed a case recently. https://www.coxengineforum.com/t5131-crankcase-upgrade-repair
Bob

If I were you, I would just stick to machining an aluminum crankcase and put a bronze bushing in the front

yep that would be best i guess

Brass also expands as its temperature increases. This is OK in a confined bearing and an advantage but for a crankcase - it would be a recipe for disaster!

It would look nice though!

ian1954 wrote:Brass also expands as its temperature increases. This is OK in a confined bearing and an advantage but for a crankcase - it would be a recipe for disaster!

It would look nice though!

All materials expand with heat.  Brass has a lower thermal expansion coefficient than aluminum, which has a pretty large coefficient of expansion.  Brass has a higher thermal conduction than iron, but less than aluminum so it should be fine for heat dissipation.

Weight is the real problem, yet brass is still less dense than steel.  

If you are making a 1-off or a very small run Brass is a good choice due to machinability.  It is generally considered better than steel and aluminum. You might not want to put it on an airplane though in brass.

Phil
http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html
https://en.wikipedia.org/wiki/Thermal_expansion
http://www.engineeringtoolbox.com/metal-alloys-densities-d_50.html

Well those are interesting reads Phil.

I am going to have to rethink why my prototyping with brass pistons resulted in seizures whereas aluminium didn't.

The aluminum pistons didn't last long though!

A Piston is not a crankcase.  

Phil

OK, editing...

Modern engines are hard plated brass cylinders with aluminum pistons. The plating is chrome or nickle. The cylinder is tapered. This works because the piston should remain slightly cooler than the top of the cylinder so a tight fit is formed the entire length of the cylinder after the engine is up to temperature. The plating is a wear surface, and when worn away the cylinder fails very quickly.

Brass or aluminum piston in a steel or iron cylinder is going to seize.

Old construction engines are lapped iron or steel cylinders with iron or steel pistons. The parts expand at the same rate, so the fit should remain similar as the engine heats up.

Cranks should be made out of the best material available, so a medium to high carbon steel that is quenched and tempered for the best properties is probably best.

I understand COX engines are leaded steel piston and cylinders for machinability.

Phil

if i built one it would be a shelf queen, it would look nice if i polished it up, mght be able to win one of those black lynx's  

@pkrankow,i race dirt bikes and the older machines have a steel piston liner with a forged or cast aluminum piston, they dont seize unless you dont warm them up properly. but they do have piston rings, so if he machined an aluminum piston to go in a steel bore, it would have to have rings. i usually run 2 thou clearance between the piston and cylinder, way more than a standard cox cylinder and piston

i hate to sidetrack my own thread, but i need to know when cox quit using tapered grind cylinders on there 049 AND 051 tee dees?

looperdude wrote:@pkrankow,i race dirt bikes and the older machines have a steel piston liner

I'd be VERY surprised if they use steel liners.  Cast iron is the norm, and there is a big difference.

Rings change the game considerably. You can have additional edge clearance on an engine with over sized rings and it will run fine, and have decent longevity. The ring is a cast iron spring seal, there is a gap in the ring. On larger engines there are 2 and sometimes 3, although a model size engine rarely will have more than 1. There are ringed model engines out there, the cost is high because the complexity is high.

I don't have any model engines with rings right now.

Phil

pkrankow wrote:The ring is a cast iron spring seal
Phil

Sorry to be a bit pedantic, but if you're going to discuss pistons, rings and bores you need to sort out the difference between cast iron and steel. They're very different and they bring different properties to the game. Yes, there are steel rings and cast iron rings, and the are probably some steel bore sleeves out there (somewhere), but the norm is cast iron bore and high carbon steel rings. They're that way for very important reasons.

Again, sorry, but if we're going to discuss a topic let's get the basics settled first.

dinsdale wrote:

pkrankow wrote:The ring is a cast iron spring seal
Phil

Sorry to be a bit pedantic, but if you're going to discuss pistons, rings and bores you need to sort out the difference between cast iron and steel.  They're very different and they bring different properties to the game.  Yes, there are steel rings and cast iron rings, and the are probably some steel bore sleeves out there (somewhere), but the norm is cast iron bore and high carbon steel rings.  They're that way for very important reasons.

Again, sorry, but if we're going to discuss a topic let's get the basics settled first.

You have a valid statement, and I am possibly out of date. Cast iron is still used, as is high carbon steel. There seems to be some change in the favor of materials.

http://www.federalmogul.com/en-us/eit/daros/pages/productdetail.aspx?productid=6192#.Uf7xORg7-P8
http://en.wikipedia.org/wiki/Piston_ring
http://www.grantpistonrings.com/products/rings/rings_MatCoat.htm

I was not aware that alloy steel had become so prevalent in piston ring technology as the last engine that I did rings on was in the back room of my parents house in the late 80's

Phil

some cylinders have cast in iron liners, and some have pressed in steel sleeves, the newer 4 strokes have a pressed in steel sleeve, their not cast iron.

Back to the topic, I think brass crankcases are doable, although the only problem is the weight. Try to put an aluminum crankcase on jewelry scale, and X 3.2,  machined it slightly thinner and you gain maybe 10 to 15 grams extra ?
I will check on aluminum crank case's weight by tonight.
This make me want to invest on an used milling machine !

i really want one of those sherline mills, it would be nice to get the lathe too, would be perfect for projects like this.

well, I just check out the price for complete, mini mill, lathe etc, seems too expensive for me.
maybe sell off some of my Cox engine collection ?