Aluminium for conrod

[Dougie SwanParticipant @dougieswan43463]

Hi

Can anyone tell me the best grade of aluminium for ic engine con rods?

Thanks

Dougie

[Roderick JenkinsParticipant @roderickjenkins93242]

H15 aka 2014 aka L168 is the stuff I use for con rods.  A search on Ebay will probably come up with someone selling offcuts.

Rod

[bernard towersParticipant @bernardtowers37738]

Im just doing a Sparey 5 and have made the rod from 7075

[JasonBModerator @jasonb]

I aways use 2014, the copper in it also helps when there are no bearings and the alloy is running straight on the crank pin as you tend to find in model aero engines. It also has the strength for when you do have bearings.

M-Machine’s ebay shop often has 2014 offcuts but they also sell from their main site.

[samuel heywoodParticipant @samuelheywood23031]

Forged Aluminium rings a bell, but as presumably you wish to make yourself, i guess that’s not terribly helpful?

Seem to remember Dad’s BSA A7SS had aluminium con rods & they were prone to failure~ probably aided the demise of the British Motorcycle industry.

& My recollection of taking 70’s /80’s Jap bikes apart was that the con rods were a golden colour~ some sort of bronze?

[JAParticipant @ja]

If it is for serious work – steel.

This may be a glib answer but having owning two Matchless twin bikes with forged aluminium rods ……… One went through the crankcase when doing 85mph at night on the M4.

JA

[Ramon WilsonParticipant @ramonwilson3]

Well it does depend on the size of the engine of course but not knowing anything about motor cycle engines I’ll abstain on that front.

A model I/C engine however is a different matter and using He15 -2014 as others have suggested is ideal. I did have a supply of very tough aluminium called Alumec 89 which is around the 7075 grade as Bernard has used and this has proved successful too. Alas the supply for that has now ceased 🙄

Unless the rod is very small at the big end I usually fit a bush made from drawn phosphor bronze. Though it is recognised that this material should only be used if a ‘shaft’ is hardened due to the potential of ‘pick up’ I have found no issue with it on EN24T in it’s as machined state in the engines built to date.

If the rod/section is small or slight then steel can be used but it really ought to be bushed if running on an unhardened steel crank pin

Tug

[samuel heywood]

On samuel heywood Said:

Forged Aluminium rings a bell, but as presumably you wish to make yourself, i guess that’s not terribly helpful?

Seem to remember Dad’s BSA A7SS had aluminium con rods & they were prone to failure~ probably aided the demise of the British Motorcycle industry.

& My recollection of taking 70’s /80’s Jap bikes apart was that the con rods were a golden colour~ some sort of bronze?

On my A10 it was the crankshaft that failed and the alli conrods were fine.

I don’t think it was conrods that did for the industry – it was insufficient readiness to invest in efficient production methods and experiments in product design, plus a government with little interest in preserving it and cheaper overseas labour.

[samuel heywood]

On samuel heywood Said:

 

& My recollection of taking 70’s /80’s Jap bikes apart was that the con rods were a golden colour~ some sort of bronze?

Copper plating, this masked the areas of the rod that did not need case hardening.

[John HinkleyParticipant @johnhinkley26699]

Malcolm Stride, in his book, “Miniature Internal Combustion Engines”, suggests HE15 aluminium for higher revving engines and states that it makes satisfactory bearing material in combination with a good finish on a steel crankpin, as has already been said, otherwise steel in conjunction with bronze bearings.

John

 

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