2014 is the usual choice which was the old HE15 or “Dural”. Better properties than 6082 T6 and as it also contains copper is a bit more self lubricating.

Any particular reason for preferring that Bernard. Just about every IC engine drawing I have specifies H15 or if more recent 2014 with the Americans going for 2024 which seems to be more easily available over there. A Couple of the more recent German ones go with AlMgSi0.5. But I don’t recall any specifying a 7000series alloy.

Certainly all the engines I have built with Aluminium use it and I’ve not had a rod fail.

He must know something the likes of Westbury, Sparey, Whittle, Mason etc don’t. Even our own Ramon who makes and competes with Diesels used 2014 and again Nick Lickfold uses it in his competition engines as mentioned in this thread where the question was last asked, seems most there also suggest HE15 or 2014. Is he running with or without bearing shells?

I suppose at the end of the day do you want to risk a failed conrod in an engine you have spent many hours making from a less commonly used material or play safe and use what has done the job for100 years which is how far back some of my drawings go.

Oh dear

Julie, do the pro engine makers run the aluminium straight on the crank pins as a lot of small model diesels do or use bearing shells? As I had always understood that the old Dural, HE15 and now 2014 and 2024 ran better straight on steel than the stronger 7075 T6 due to the copper content rather than 7075s zinc content.

2014 is also said to be more free machining which as a lot of hobby users don’t have flood cooling also makes it a better hobby option. Also stocked by several of the ME suppliers so easy to by an inch or two for a conrod

As I said the ME suppliers do it. Both M-machine and College Engineering have 1/4″ and 3/8″ and Noggin have it from 1/2″. M-machine may be cheaper if you go down a page ortwo and buy rectangular section as that is sold by the inch. Some list it by old numvbers which is HE15

Oddly enough none list 7075, must be a reason why?

Most race engines run with shell bearings. The rules in F1 have changed but when I was working in motor racing, mostly on Indy cars, the engines were completely rebuilt after every race. So wear was a moot point, as long as the engine kept going for the duration of the race. According to the datasheets 7075 does contain copper, albeit a bit less than 2014.

Forces are significantly higher in full size engines and many race conrods are forged and finish machined rather than fully machined from stock.

I would agree that 2014 is more readily available than 7075. Most commercial aluminium stockists list 7075 but it will be expensive.

Julie

The Copper content in Aluminium or Duralumin causes “Age Hardening”. There was if my 70+ year old memory is correct a 5 day window for machining after heat treatment. Again if I remember correctly part of the pre-machining heat treatment involved keeping the parts in cold storage, but I may be wrong there.

After machining the parts start to get harder with an improvement in UTS.

Regards

Gray,

So it depends on the metal a lot in terms of the age hardening, but can vary from 5-10 days depending, and this normally ends you at T42 temper state. (The T is temper, the first number is the state and the second number is the amount of solution heat treatments it’s had)

to get to T6 see you would artificially age at a lower temp normally around 190*c ish depending on metal and for anywhere from 8-16hrs. Again varies on type of alloy.

the first treatment is SHT solution heat treatment where is high temp (like 500*c) for a shorter time (30 mins varies on thickness) and is then immediately quenched (this is very time critical)

the metal is then as soft as an annealed peice for a short period of time. It age hardens quickly. You can hold this state by freezing it. And then depending on what T state you want, begin your Precip…..

I could bore you for ages on this. We do a lot of sheet metal work on aircraft and do a lot of this. Many variables depending on metal and thickness and what you want to do with it….