Why the minimalist cooling surface area?
fabian, how many times can i repeat this? im using the pieces of alloy i have handy.
until i buy some 100x100 billet, this is all im making. thats it. i dont have anymore alloy this size left. 3 heads i made. and it looks like i either have to buy billet from america and pay postage, or buy 6.5 metre lengths. which arent cheap. or find something at the scrapyard. its not too common a size...
http://www.ebay.com.au/itm/New-Alum...1248264900?pt=AU_Supplies&hash=item33836c9ac4
thats 2 heads... though it is overpriced.
or, from US... 3 heads! big ones! 5"x5"x2"! $40 each? before machining?
http://www.ebay.com.au/itm/5-5-000-...995?pt=LH_DefaultDomain_0&hash=item27bf1211c3
it would also be 50mm deep, not 30. so double the number of fins. larger fins. that i would consider making if people are interested. i need the volume to be worth while. a shaper would be best for cutting the fins en masse. another tool that would cost money. though they are cheap...
for performance? this thing is more a practising of my skills, a revision if you like. im not measuring, im not calculating, im just machining metal to look cool, ok? i have the machines. why not? i finally got the hang of sinking in a parting blade fairly deep. have you made a rotating toolpost for cutting hemispheres while dealing with reverse jaws on the chuck on a lathe that has barely any clearance in the first place?
every project i take on, my skills improve. my techniques get better.
i need the occasional break from everything else too. thats all this is.
anyways... a conservative calc on surface area is putting me around 3/4 of the stock head... not bad considering how small it is.
jaguar. the 48cc cylinder and piston just is not conducive to squish band designs.
heres a photo
i also took a video of it running, but for some reason it stopped recording after 10 seconds...phooey. ill try again later.
photo.
now, that was after todays running, around an hour or so now. interesting clean patch above the exhaust port. doesnt show in this pic.
but jaguar, as you can see, there is a dirty great chamfer on the edge of the cylinder.
that would require machining away to a flat true surface. this requires a jig to hold the cylinder true, as you cant just chuck on the bore on the lower end. its not a true machined surface to reference off. basically i need just a mandrel, slitted so it will expand slightly and grip the bore when a nut at the end is tightened. then i can mount it on centres and machine each cylinder PROPERLY.
as it is i dont have time or material. its on the list.
now, machining the cylinder chamfer away would result in the piston crown standing proud, so...
the cylinder would need recessing. the head would need a spigot to suit the cylinder, lapped so as not to need the gasket. also makes for easier measurements, better heat transfer, better sealing, all the good stuff.
then the head will need to be slightly counter bored to match the piston crown, that has that dirty great chamfer too.
otherwise, the squish band just isnt. you have a toroid shaped ring of fuel mix that doesnt get ignited. a not insignificcant volume, either.
defeats the whole purpose.
i might try a skyhawk piston, the one in mine is domed. but then ive heard the heights are different.
and, with the 1mm head gasket... i think i have a 2mm squish band
ha ha. squish was not my intention...at this point. i left space for when i do the aforementioned to a cylinder.
its still got more bang for the buck, enough so i swapped to a 36 rear. acceleration is up, much more zippy and responsive to the throttle. sounds like a two stroke should when the throttles blipped.
oh, and it really showed the extended intake to be the wrong length. it would just about stall at 6000. so probably best to start tweaking the piston skirt. still stock inside, havent gone past removing the head...
