L1418 steel?

[t.l.a.r. eng]

The last three I/C engines I made used 12L14 steel, aluminum pistons and cast iron rings. Compression is terrific on these engines, the more they run, the better it gets.

Doesn't matter if they run on glow fuel, or Coleman, very little wear and great compression.

 

[petertha]

Might be the appropriate time/place to ask this question about 12L14. It seems to be a consistant favourable choice for cylinders & liners because of its machining properties; attaining nice ID & finish, cutting cooling fin profiles, sufficently strong to hold bore dimensions etc. The only downside I've heard is it's propensity for rust/corrosion.

But I've noticed it doesnt seem to be called for as often for crankshafts & other (?maybe moving or internal?) engine parts over other material choices. Yet some of those seem not much if any stronger over 12L14 (other than 4xxx type series). The reason seems to be 'rust' again. So what is it about rust that makes it ok for cylinder liners intenals but not ok for crankshaft parts? Maybe the steel-to-steel nook & cranny places like bearing fits vs aluminim piston on 12L14 liner? I would think its machining advantages for more complex crankshafts & journals would outweigh its disadavantages. Maybe its moreso a material strength thing? I'm getting close to starting a project & this as been on my mind.

Also, in my RC experience, its pretty standard to store engines with a healthy dose of oil purely to protect from corrosion. Methanol fuels are particularly bad for sucking up moisture from air & making corrosion mess of teh inside. I used plain pneumatic oil, others have recipies mixed with transmission fluid etc. But the drill is" load it liberally with oil in fall for storage. Come spring, drain it out, flush with WD40, everything stays shiny clean &ready to run. Would a procedure like this help with 12L14 internals?

 

[jack620]

Tin,
Thanks for the cross-reference chart. I'll print that off and put it up somewhere in the workshop. The liner is 13mm OD x 10mm ID. I already have a length of 1" round 12L14. I may use 41L40 for the crankshaft.

Phil,
Thanks I've been following that article for the crankcase build.

Ramon,
You've convinced me to use 12L14. Since my last post I have also been looking on MEN and Ron also recommends 12L14, so 12L14 it is!

T.L.A.R,
thanks for confirming my decision!

Peter,
Ron Chernich doesn't recommend 12L14 for crankshafts because it isn't strong enough. He doesn't mention rust. Apparently the steel to use on cranks is called "stressproof". I gather that's a brand name used by a particular steel manufacturer and it is very expensive. I don't know if there is a suitable number grade steel to replace it. I was thinking of using 4140 or 41L40 if I can get it.

Chris

 

[GailInNM]

The generic version of Stressproof is 1144. It is not a lot more expensive than 12L14. Depending on the size it costs about twice what common 1018 cold rolled does. It is used in Swiss Automatic lathes a lot and as the OD has to be precise to work in them it is available ground and polished to +0/-.001 inch tolerance as well as just cold rolled. This makes it very nice for shafting. As the name implies it has very low internal stresses so very little warping when machining. I use it for lots of things including valves and crankshafts.
Gail in NM

 

[jack620]

OK, 1144. Thanks Gail.

 

[petertha]

Peter, Ron Chernich doesn't recommend 12L14 for crankshafts because it isn't strong enough. He doesn't mention rust. Apparently the steel to use on cranks is called "stressproof". Chris

OK thanks. This makes sense now. I see for example tensileyield of 12L14 is 60 ksi versus 105 ksi for 1144. I pasted properties below, both selected type cold drawn.

12L14
http://www.matweb.com/search/DataSheet.aspx?MatGUID=e4a48445c6994e629167c577d73df5fe

1144 stressproof
http://www.matweb.com/search/DataSheet.aspx?MatGUID=c06c517889d7488eb3ac85a5d8efc492

 

[Ramon]

Hi Guys - I've never experienced any form of rust on the leaded steel liners made so far nor indeed on those commercial engines owned that I now know have had similar liners.

The running surfaces of these small engines running on the usual castor based fuel soon acquire a coating of oil which helps protect the internals. However, this can become very gummy over a period of a long layoff if not oiled up after running. If left for long enough just as last run this can sometimes be so great as to give the impression the engine is seized. If that occurs I have found the best way to free them up is to attach a prop first then heat the engine with a fan heater or hot air gun. This is usually sufficient to be able to get the piston moving slowly by gently wringing the prop. A very - very- small amount of cellulose thinner is then dropped on the piston and a similar amount down the intake. This will soon break that gummy grip when plenty of parrafin and oil flushed through will soon have it ready to run - which is, without doubt, definitely the best way of all to free up an engine. Too much cellulose will however lead to ruining that oil 'varnish' built up in the pores of the running surfaces leaving the engine rather 'sqeaky' so don't over do it.

On diesels I usually flush them out well with parrafin and oil after running before storing, glow motors I use hydraulic fluid as an after run oil. Incidentally basic methanol/oil won't usually damage an engine but any run on fuel with a nitro content can corrode on the inside quite badly if not flushed out with an after run oil.

Re steel for crankshafts - so far all made have been from non heat treated En24t (4340 equivalent) which has proved more than ideal. Machines well, gives a superb finish with sharp HSS tooling and polishes well. I guess the smaller capacity engines won't need something quite as tough - it's the forces on the crankpin that has to be the biggest consideration but I think it fair to say it does need to be a mite tougher than leaded steel

Looking forward to seeing your end result Chris - I'm about to make a start on some more Eta's this week

regards - Ramon

 

[jack620]

Thanks for the data Peter.

Ramon, I'll add 4340 to my list of suitable crankshaft metals. Thm:

 

[oldlunns]

chris listen to Ramon [you only have to look at his work] don't know about 4340 ,but a lot of the fellows here use 4140 for crankshafts and 12l14 for cylinders .By the way you can get 12l14 and 4140 at a 'specialty metals 'place in Hallam st Hallam [melbourne] see Tony

[ps happy birthday for the other day Ramon]


den

 

[lensman57]

chris listen to Ramon [you only have to look at his work] don't know about 4340 ,but a lot of the fellows here use 4140 for crankshafts and 12l14 for cylinders .By the way you can get 12l14 and 4140 at a 'specialty metals 'place in Hallam st Hallam [melbourne] see Tony

[ps happy birthday for the other day Ramon]


den

Hi Den,

4140 and 4340 steels are mainly used for high stress applications such as automotive crankshafts, connecting rods, etc. Surely these grades of steel ( high tensile and hardened in their T form ) need to be precision ground rather than machined on a lathe or mill, I personally think that these are over kill for the application suggested and difficult to precision machine on a hobby lathe or mill or am I missing something here. I would be grateful if someone could suggest a way of precision machining these at home with basic equipment.
If a special steel is prefered then I would go with EN8, Us des 1039~1045
which is very easy to machine and can be heat treated to the desired hardness, these are used for axels and shafts , etc and so on and very easily available. In the final analysis the OP has to decide what application the engines are for, occasional short period runs for show or real use in powering a vehicle of a sort and then settle on a suitable material for the build.


Regards,

A.G

 

[Ramon]

You had me there Den - how the hell did he know that then I realised it's at the bottom of the page Yep a young 68 as of Friday - it was this time last year I was gearing up for a visit to the sawbones - that seems a long time ago now

I have made several crankshafts now not just for the 5cc versions but quite a few for worn commercial engines too. All have been made using En24T (4340) and none have proved difficult to machine - tough? Yes, cuts have to be much lighter and speeds much slower but the real benefit of using this is it is prehardened and in a tempered state which is machinable at home without recourse to grinding. Definitely - in an ideal world - the later would be preferable but like most of us that facility is unfortunately not available.
Personally I dislike using carbides and have found that using HSS shallow 10 thou cuts at a fair feed rate (applied by hand) with the speed a tad faster than usual soon reduces a piece down to shaft size. I was given a tipped tool to try on the last engines and this helped reduce the roughing time but I would never use it for finishing to such tolerances as are required here.

Why I particularly like using En24T is because of the weak spot - the crankpin - but I agree that a slightly less tensile material could be used for smaller engines or pressing in a crankpin of suitable material though I have as yet to try that method. I have a good friend who makes some exceptional diesels in the 2.5/3.2 class the latter used at top competitive level for 'combat' C/L flying. His crankpins are made from the rollers for needle roller bearings - very hard skin but tough core. Incidentally he uses En24t for the shafts and - despite having a small Myford cylindrical grinder - actually prefers to turn and hone his shafts to finish size.

The one thing I would say to anyone machining this or most tough materials for the first time using HSS is that the tool has to be really sharp for those final finishing cuts. Certainly En24T exhibits a property of the skin glazing/work hardening on very fine cuts if the tool is rubbing in the slightest. This usually leads to nothing coming off so another thou or so is put on - same thing, another thou on the dial and whoops too late you're undersize. I always have a freshly sharped tool set up ready for that last five/ten thou leaving a thou or so up on dia for polishing with 4/600 wet and dry stuck to a parallel with double sided sticky tape.

My work experience involved a high degree of heat treatment - despite that I'm reluctant to go down that route if avoidable because of the potential for distortion which only grinding will take care of. There are parts that get HT'd but that worry is always present.

In the end 'yer pays yer money' etc

Regards - Ramon