Stoopid question

[Kevin Garrod]

Apart from saving weight, what advantage is there in ally heads? The disadvantages I know.

[stustag]

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Hi Kevin

Apart from weight saving which is negligible due to a cast iron block! The main saving is the cost of machining as aluminium is much cheaper to machine due to the use of PCD tooling which has a huge tool life compared to the tool life on Grey cast iron using carbide tooling.

I would have thought you can cast a thinner walled component out of aluminum as well so the engine can be made smaller.

Stuart

[Kevin Garrod]

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Thanks Stuart!

So there we have it, all our head problems are down to penny pinching. Well I'm shocked

[Rubce]

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Or they could have save all the development costs etc and simply fitted the 3.5 litre Rover V8:shock:

Bruce

[stustag]

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Rubce wrote:

Or they could have save all the development costs etc and simply fitted the 3.5 litre Rover V8:shock:

Bruce

that would of meant shipping an engine from Solihull to Coventry! No No No definitly not the done thing at all!:P

Anyway that would of be far to easy and uncomplicated etc.

It would of also kill Rover overnight as Triumphs out sold them 2:1 anyway if Triumph had the Landrover V8 they would of put it in the MK2 as well and Rover would of been nomore!:shock:

Stuart

[Rubce]

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Hmm, I thought they were all part of the same nationalised junket by then?

Bruce

[stustag]

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I work for a group with 6 companies in it doesn't stop them working as individuals!

Stuart

[al-stag]

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stustag wrote:

Hi Kevin

Apart from weight saving which is negligible due to a cast iron block! The main saving is the cost of machining as aluminium is much cheaper to machine due to the use of PCD tooling which has a huge tool life compared to the tool life on Grey cast iron using carbide tooling.

I would have thought you can cast a thinner walled component out of aluminum as well so the engine can be made smaller.

Stuart

This is an interesting question...


I would guess a pair of heads would weigh approximately 210 lbs in Cast Iron, and only70 lbs or soin aluminium, so there is a very substantial weight saving, because aluminium weighs exactly 1/3 of the weight of iron. (If someone has got a head off can they weigh it and report back?). With such a lumpy engine in such a small chassis I think the designers would be looking for every weight saving they could get.

With respect I would have thought the tooling cost would be microscopic in comparison to the rest of the costs. The heads were possibly gravity or low pressure die castings and although that would use very complex cores its a more convenient method of manufacture than those employed on iron castings. Cast iron is a fantastic material for creating complex shapes, it remains liquid longer and flows more easily than aluminium, which tends to chill quickly and require heated dies. It also suffers from porosity problems and often requires impregnation to seal it.

I think the heat dissipation properties of aluminium lie at the bottom of this puzzle as well as the weight saving. Ally conducts heat better and the wisdom at the time said that it was a better way of dissipating heat with the higher surface temperature,, coupled with the weight issue. Remember that slightly later engines changed to all aluminium construction, but that would involve expensive wet liners.

The execution of the design was obviously cr*p, and left Stag owners with so many other problems (distortion, corrosion, those stupid angled studs), the mind boggles. BL bean counters obviously didn't give a toss and just wanted to see the Stag dead and buried without further expense. When you read up the design history of the Stag it was so full of compromises its a wonder it ever got built.

Al

[mad cyclist]

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Rubce wrote:

Or they could have save all the development costs etc and simply fitted the 3.5 litre Rover V8:shock:

Bruce

apparantly there were not enough to go round!! when the stag was developed, they were having problems making enough for the rover production.

rgds Nick

[mad cyclist]

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al-stag

i often come across the alloy is lighter than steel argument in the bike game , what is not always considerd that there are poor allys and good steels and vice-versa.

sometime you need more alloy to make something than steel, so making something of alloy dosen't equate to a pro rata weight saving...........i need to lie down now ..

nick

[StagnJag]

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mad cyclist wrote:

Rubce wrote:

Or they could have save all the development costs etc and simply fitted the 3.5 litre Rover V8:shock:

Bruce

apparantly there were not enough to go round!! when the stag was developed, they were having problems making enough for the rover production.

rgds Nick

They would have had to tool up to make the Stag engine, why not tool up for the Rover engine instead?

Dave

[mad cyclist]

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stag engine was tooled and in production when bl took over triumph, when bl took over they did not want the project and spent little on it including not paying the foundry to clean out all the casting sand and the rest is history!!

[al-stag]

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mad cyclist wrote:

al-stag

i often come across the alloy is lighter than steel argument in the bike game , what is not always considerd that there are poor allys and good steels and vice-versa.

sometime you need more alloy to make something than steel, so making something of alloy dosen't equate to a pro rata weight saving...........i need to lie down now ..

nick

Engineers often have this debate too. Steel is 3 times the weight of aluminiumbut has 3 times the Modulus of Elasticity. Thus, you might need three times as much ally as steel to get the same stiffness on the same section. But you can extrude ally into stiffer, non round sections easily, and this is why its so popular on bikes, as such sections can put the metal where its more effective. Personally, on a bike, I much prefer the live feel of steel rather than ally. My steel 1971 Dawes Galaxy is a pleasure to ride. It has brazed lugs which are incredibly strong. Most cyclists forget that shaving off a lb by having ally or carbon bits is much more painful on the wallet than losing a lb of flab. I find that amazing. There is an awful lot of guff talked about ally alloys. If you weld it you fill it full of microscopic cracks (just like steel). Its the quality of the post weld heat treatment that does the business.

The killer on heads is surely ally's unfortunate habit of creeping at relatively low temperatures, which is why its so important to avoid overheating because the tension and thus clamping pressure on the gaskets will be badly affected by the material around the studs losing its elasticity due to creep and taking on a permanent set. The properties of aluminium can be drastically changed by exposure to temperatures around 200 degrees C. This was potentially a big problem with the Concorde airframe which was subject to kinetic heating from air friction, which is why the hot skin of the airframe was cooled so it didn't creep, by pumping the fuel around.

I'd dearly like to know what was going through the Triumph Engineer's minds though.

Al

ps Don't get your black ally bike too hot in the sun because it might start to collapse! ;-)