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Best aluminium grade for con rods

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Dougie Swan29/03/2022 16:31:25
235 forum posts
53 photos

Hi

As the title suggests I'm looking for advice regarding the best grade of aluminium to make con rods from

I'm also looking for a UK supplier of flat bronze bar

Thanks in advance

Dougie

Emgee29/03/2022 16:36:05
2426 forum posts
290 photos

HE15 is suitable for conrods and other highly stressed parts, 7075T6 may be an alternative.

Emgee

Edited By Emgee on 29/03/2022 16:40:15

bernard towers29/03/2022 16:38:38
619 forum posts
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I think HE15 is used for that. new number is 2014 T6

Edited By JasonB on 29/03/2022 16:52:41

JasonB29/03/2022 16:51:47
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I always go for 2014 which is the old HE15

M-machine do bronze flats or cut from sheet as well as doing 2014. I usually e-mail Lynn a list of what I want and se sends back an invoice then I phone her with card details.

Dougie Swan29/03/2022 17:12:13
235 forum posts
53 photos

Thanks for the replies and thanks Jason for where to get it

Regards

Dougie

JasonB29/03/2022 17:16:47
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Sometimes cheaper to get round 2014 than rectangular.

Andy_G30/03/2022 10:58:16
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Is there any problem using 6082 / HE30 for conrods?

(In T6 condition)

Edited By Andy_G on 30/03/2022 11:00:01

Emgee30/03/2022 11:58:45
2426 forum posts
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Posted by Andy_G on 30/03/2022 10:58:16:

Is there any problem using 6082 / HE30 for conrods?

(In T6 condition)

Edited By Andy_G on 30/03/2022 11:00:01

Andy, check the material data sheets for a detailed answer, then decide if you want to risk using 6082T6 in an engine that has taken many hours to make.

I have no doubt there are some running engines with HE30 con rods that perform well over a period of time.

Emgee

Andy_G30/03/2022 12:21:13
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Wow, I didn't realise that 2014 was so strong - especially in T651 condition. Question answered.

JasonB30/03/2022 12:52:11
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There is a risk of 6082 stretching and the holes going oval.

Also if it is a design where there are no separate bearing shells as you often find in small model IC engines then the copper content of the 2014 makes for a much better wear surface.

Andy_G30/03/2022 20:07:44
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Thanks Jason.

Bill Pudney30/03/2022 22:47:59
612 forum posts
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The chart had a fairly common types of Al Alloy, with the types of material for small conrod. ..........

Bill Pudney30/03/2022 23:54:30
612 forum posts
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Sorry, I seemed to have lost the chart.

Somewhere.

I will try and find it.

cheers

Bill

Ron Laden01/04/2022 07:57:08
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Would aluminium bronze be a good conrod material I think it is known for being a strong alloy..?

Andy_G01/04/2022 11:25:11
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Posted by Ron Laden on 01/04/2022 07:57:08:

Would aluminium bronze be a good conrod material I think it is known for being a strong alloy..?

With my recently refreshed knowledge of the aluminium alloy properties, I offer the following:

Generic data on aluminium bronze seems to suggest that the yield strength is of the order of 250 MPa.

(Source)

6082 T6 yield strength is ~240 MPa in sheet form and up to 270 MPa in bar form (depending on size).

(Source)

2014 T6 sheet has a yield strength of ~380 MPa and bar in the T651 condition >420 MPa

Note that 2014 in the T4 condition is back at ~250MPa

(Source)

Obiously this is generic data for the aluminium bronze, and there may be specific grades with higher strength. However the other down-side of aluminium bronze is its density: circa 7.6 vs ~2.7 for aluminium alloys, so an aluminium bronze conrod would be almost 3 times the weight of an aluminium alloy one which in itself will increase the loading on it (and the rest of the engine!) and probably give rise to balancing / vibration problems.

£0.02p

Edited By Andy_G on 01/04/2022 11:32:01

David-Clark 101/04/2022 12:07:28
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220 forum posts

When I used to machine two stroke con rods professionally, there was a half bearing shell in the main body and the rest of the big end was just aluminium. The designer calculated the load as not requiring a full bearing.

Neil Lickfold02/04/2022 02:42:36
862 forum posts
195 photos

A very good grade is 2024. It can be used without bushes in the small end and the big end. It used to be used for conrods for control line speed engines. I still use it for F2A conrods, but now leaded bronze2 is used in the Big end, but these engines are revving up 41krpm. The small end is left un bushed and works very well.

JasonB02/04/2022 07:11:04
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America tend to use 2024 and UK 2014 as they are the commonly available grades.

"Bronze" is quite often used in model engines, look through the various casting kits available and you will find the conrods supplied as castings as they can be produced without the need for heat treatment and provide a good bearing surface. Several of Wesrbury's IC engines use it as did the 2 & 4 Stroke engines from Wall in the US

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