First try


Hi all,
I've finaly got my very own lathe and a nice milling machine is coming soon
so i can finaly start my first model engine build (or atempt to...).
But for now i have a material question.
As far as i know, the recomended metal for making the cylinder and piston is
"pearlite cast iron" (i hope i translated that right?!?).
I know of one or two adresses here in holland where i can buy some nice
round bar, for a fair price. But my internal hippie always likes to use
scrap metal for projects wherever i can.
(You can probably guess where i'm going here)
Do you know of any machines/objects or something that is usualy made out of
pearlite cast iron, that is usefull to re-use in a model engine? And is
there a way to easily recognize the right kind of cast iron, from the wrong
ones?
I'm having trouble finding any info on the internet on this subject.
Thanks for any help,
OmeJozz
Reply to
OmeJozz
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Also known in the UK as centrifugally cast moly cast iron. Reeves used to sell it. Another source is large diesel engine valve guides. Old ones from tug boats have lots of meat on them. Any place that rebuilds largish diesel engines may have new obsolete ones that are a bit smaller.
Steve R.
Reply to
Steve R.
Its "Meehanite" also sold as grade 250 cast iron. Continuously cast as said above and a very fine grain good quality grey cast iron. All the model engineering outlets in the UK will sell it.
Jason
Reply to
jasonballamy
But what is Meehanite?
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Reply to
1501
Cast iron manhole covers are made from "ductile cast iron" which, as the name suggests, isn't brittle like the basic grey cast iron used for fire grates, etc and machines nicely. Many moons ago we were looking for test samples of a particular grade which had been used on some nuclear power station component, and found that it was still in use for manhole covers. Not only that, we found a foundry which let us have for free a couple of rejects off their scrap pile, which was fine for the postage-stamp sized specimens we wanted.
Reply to
newshound
"OmeJozz" schreef in bericht news:94d42$4ac3d553$3ec30c8e$ snipped-for-privacy@news.chello.nl...
Thank you all for your tips.
After reading your mesages, i think i should smack my internal hippie around a bit until he lets me buy the "good stuff" from one of the supplyers i know of. The tip on finishing a failure piece in stead of throwing it around the shed a bit souds like very good advice.
I think about building the "simple two stroke engine" from the next webpage.
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The dude who build this one (and designed it as far as i can see) has send me the complete drawings and suggested this model for me to start with. Do you think this is a good choice or should i start somewhere else?
OmeJozz
Reply to
OmeJozz
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It does look a really nice display piece.
For my first engine I avoided petrol / spark ignition and used a glo-plug instead to reduce the number of parts that could go wrong, I'm not shy of those things, just less to worry about with a first engine. May be worth asking Jan what he thinks.
The other characteristic of my first engine was that it was the basis of a detailed magazine articles that described how to make the parts as well as a plan of the parts. The when that wasn't enough, I asked questions of the guys here in this NG!
Best thing is to get started though - just like Bilbo Baggins said, "Nothing takes quite so long as the job that's never started!"
Goed geluk!
Steve
Reply to
Steve
How big are the bits you'll need for this? A good source is old car or truck engine crankshafts which have some fairly long solid bits at the flywheel flange end or the nose end. Car engine flywheels are also usually a decent grade of cast iron as are most brake disks. Camshafts are also often cast iron but usually chill cast so they'll be rock hard in places and unmachineable.
If you post some dimensions I'll see if any of the old cranks I have might suffice which at least will tell you which ones to look for over there.
You can get some fair sized chunks of cast iron from the main bearing caps on engines. Usually about an inch thick by two or three inches tall on car engines but bigger of course on truck ones.
For pistons it's more normal to use aluminium which has a high silicon content. Melting down an old car piston into a solid lump would be as good a source as any. You can't easily buy new bar in that sort of grade although HE15 has quite good high temperature properties and might suffice for a low output engine.
If the gudgeon pin is a floating one running in a bronze bush in the conrod then an old engine valve guide might give you the bronze you need. Most continental engines, Peugeot, BMW, Renault etc use bronze guides. Most diesel and English or American engines use cast iron.
Reply to
Dave Baker
At last someone else who uses scrap! I have no problems with material from scrap yards, either ex engine bits as you describe or aluminium or brass that "looks good". The fitting of stepper motors on my lathe was completed with scrap aluminium bought for pence. I have a good selection of bronze for bearings and valve guides all dirt cheap. Odd lengths of steel bar for next to nothing. Ok I do not necessarily know the spec but not exactly highly stressed in the stuff that I do, and if making a mandrel or plug gauge does it matter?
Richard
Reply to
Richard Edwards
"Dave Baker" schreef in bericht news:ha83c8$pcj$ snipped-for-privacy@news.datemas.de...
Thank you Dave, That will give me something to hunt for.
For the sizes i need, the cilinder for the first project i would like to try has an outside diameter of 50mm (if i'm correct that should be about 2 inch) and a length of 61mm. As i'm typing this it seems like a pretty big crankshaft to look for, but you never know. I hope you have something to put me on the right track.
the piston though, was advised to make out of the same material as the cilinder. So the expention (from the heating of the engine) would be the same in both parts. By using a aluminium piston, won't i be getting some problems with that?
The melting of an old piston shouldn't be the biggest problem for me, but i assume that you then cast it in a (sort of) round-bar shape. Do you have any tips on the casting part for me?
Again, thanks for your help so far,
OmeJozz
Reply to
OmeJozz
LOL, and I built a wedge mount for my telescope for a few Canadian dollars worth of scrap aluminium. The knobs started out as replacement furniture feet.
Steve R.
Reply to
Steve R.
Yes! Get a good book on foundry practice! Model Engineer used to publish one by Terry Aspin, if my filing memory serves me right.
Steve R.
Reply to
Steve R.
yahoogroups: "castinghobby" or "gingerymachines", alternaively,
Reply to
bigegg
Most car engines have main bearing journals about 2" to 2.5" so you should be able to cut a chunk that size from the back flange of the crank and the last main journal. The only problem would be any oil drilling in the journal but you'd have to measure up. I think you'd do it easily from any diesel engine crankshaft. I suggest you find your nearest engine reconditioner and see what they have lying around.
Ha! I've just been into the workshop to have a measure up. On a normal 4 cylinder engine with 5 main bearing journals the 4 big end journals are fed with oil from drillings in the outer 4 main bearing journals. However the centre main bearing journal has no oil drilling and a big counterweight web either side of it. On a 1600cc Ford CVH crank which is not a big crank you have a solid central chunk at least 63mm long by 58mm diameter so just the job for you. On that basis any largish car engine crank should do you and certainly any diesel engine one. You'd have to hacksaw the central journal and webs out and then turn the webs off in the lathe but that's no big deal.
You'd also get the piston material in the same way if you want to stick with cast iron. Material quality in any crankshaft should be excellent although some are cast steel not cast iron so be a bit careful.
Every car engine seems to manage fine. Obviously the cold clearance between piston and bore needs to take this into account and pistons are designed to have flexible skirts so they don't seize in the bore as they expand. The design of your model engine piston may be specific to cast iron and might need altering a bit for aluminium.
Yeah. Heat it up and pour it into a tin. :)
Reply to
Dave Baker
"Dave Baker" schreef in bericht news:hacer8$klr$ snipped-for-privacy@news.datemas.de...
Thanks again,
I'll have to look around a bit to find the right reconditioner around here, never actualy looked for them so i'm in the dark so far, but that will change (long live the yellow pages). There are some junkyards around but i'm afraid they wont let me go with anything less then the entire engine, seems like a bit overkill to me.
The engine design i will try building has a pistion without rings, so i guess that's why it has to be the same material as the cilinder. It has to be a tight fit and has little to non room for expention (i think). I'll get to piston-rings in later projects, then i guess i could use a alluminium piston.
Sorry about the slightly stupid question about the pouring of the alluminium but i was afraid i had to make a sand or clay model or something....
OmeJozz
Reply to
OmeJozz
"bigegg" schreef in bericht news: snipped-for-privacy@brightview.co.uk...
Thanks for the link, that will give me something to read through.
OmeJozz
Reply to
OmeJozz

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