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Marzak

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Marzak

Posted by ken_campbell at August 05. 2017

Anyone out there know if the marzak used in the oil pump bodies is the same as what is used in Amal carburetor bodies?

Re: Marzak

Posted by richard_payne at August 05. 2017

It's certainly a zinc alloy and the pump bodies can distort and delaminate as they age if storage conditions are not ideal.  Whether it has exactly the same composition as Amal used would require an analysis...but as a 1930s die-casting alloy, I'd think that there was a good chance it's fairly similar.

Re: Marzak

Posted by David Cooper at August 05. 2017

(deleted - sorry. )

Re: Marzak

Posted by richard_payne at August 05. 2017

Were the twins always iron / steel ? The Commando certainly was and Andover's new singles pumps are too... but the pre-war and wartime SV / OHV pumps were definitely monkey-metal.

They are less prone to seizing than the pumps in BSA M20s but they can go a bit stiff if dry-stored. The alloy 'expands' with age.

Re: Marzak

Posted by ken_campbell at August 06. 2017

Previously richard_payne wrote:

Were the twins always iron / steel ? The Commando certainly was and Andover's new singles pumps are too... but the pre-war and wartime SV / OHV pumps were definitely monkey-metal.

They are less prone to seizing than the pumps in BSA M20s but they can go a bit stiff if dry-stored. The alloy 'expands' with age.

 

Thanks Gents

When you say Andover's single pumps are steel, are you including the type of pump used in Manx and Inter?

The reason that I am asking about the similarity with carb bodies, is that I want to cast a lump of Marzak and machine a new pump body. I believe that although the monkey metal has a bad reputation, it expands a little more than magnesium and aluminium, so the pump body will actually get tighter and seal better in it's bore when the engine warms up. This is why you should never heat a Manx/Inter case in the oven when removing the original type pump... only when installing it. Never heard of it expanding with age... perhaps that has to do with them oxidizing? I always have them stored in a warm dry place covered in oil and tightly wrapped..... especially when I see the cost of replacements.

 

Re: Marzak

Posted by john_hall1 at August 06. 2017

Hi,

Isn't it called MAZAK, just was looking it up for composition and the spelling changed to the one without with "R"!

 

 

Cheers

 

John H

Re: Marzak

Posted by David Cooper at August 06. 2017

Wikipedia has a very comprehensive article on Zamac (also Mazac - one of the UK market versions).

Some of the it was well known for falling apart if the individual metals were not pure enough.  Many prewar Hornby train wheels fell to pieces.   But I don't remember ever seeing even the most worn out carburettor in the jumble bins at Kempton suffering.

I'd be tempted to cast a pair of bars - one from each alloy - and put them across each other in a vice and squeeze.  Then you'd be able to find out if they have similar yield strength.

400C is quite hot...and I'd be very wary of breathing metal fumes!  Wikipedia again maybe?

Re: Marzak

Posted by David Cooper at August 06. 2017

Wikipedia has a good article on Zamac (or Mazac as some was marketed in UK).

Prewar Hornby train wheels often fell apart due to poor alloy, but post war ones seem to be OK.  I've never seen a carb body do that - not even in the bins at kempton jumble.

Melts at about 400C (rather hot), and I'd be very wary of breathing metal fumes.  Some are very poisonous.

You could get two similar pieces and place them across each other in a vice.  Give them a good squeeze to see if one is much softer than the other.

Re: Marzak

Posted by ken_campbell at August 06. 2017

Previously john_hall1 wrote:

Hi,

Isn't it called MAZAK, just was looking it up for composition and the spelling changed to the one without with "R"!

 

 

Cheers

 

John H

 

 

Yes, you are correct. Don't know where I came up with the R. In elementary school when there was a spelling bee, I was usually the first one to take a seat. My spelling hasn't improved with age....

Re: Marzak

Posted by ken_campbell at August 06. 2017

Previously David Cooper wrote:

Wikipedia has a good article on Zamac (or Mazac as some was marketed in UK).

Prewar Hornby train wheels often fell apart due to poor alloy, but post war ones seem to be OK.  I've never seen a carb body do that - not even in the bins at kempton jumble.

Melts at about 400C (rather hot), and I'd be very wary of breathing metal fumes.  Some are very poisonous.

You could get two similar pieces and place them across each other in a vice.  Give them a good squeeze to see if one is much softer than the other.

Thanks. I had a look at Wikipedia. Seems there are different versions of it. Maybe I should collect a few knackered pumps and melt them down just to make sure I have the correct material. (I have a decent respirator)

 

Re: Marzak

Posted by David Cooper at August 08. 2017

Hi Ken

I guessed you probably knew what you were doing - but I thought I'd mention the possible dangers just to avoid reading an obituary!  I don't even know how hazardous it is.  I've witnessed casting white metal into wire rope sockets and I don't remember the men taking very strict precautions although they were in a very big factory shed.  It's not like cadmium.  Although I seem to remember back in the early 1970's that steel erectors on our site were given milk to drink when they were flame cutting galvanized (i.e. zinc plated) scrap steel - so their systems would be flooded with calcium to reduce possible uptake of zinc.  No idea if that's worthwhile or even necessary.

25 odd years ago there were two (possibly three) small foundries within half a mile of my house in the suburbs.  All gone now.  I've no idea how many such remain - nor what they'd charge for a one-off if I provide the pattern.  More than Andover Norton would charge for a new iron pump, I'm sure.

Re: Marzak

Posted by ken_campbell at August 08. 2017

I wouldn't go so far as to say that I know what I'm doing, but I generally try and avoid fumes and refrain from setting myself on fire. Always good to caution folks....

Some of the things they did back in the day were a little strange, like getting the coal miners to inhale Mcintyre powder.

I'd love to have a little back yard foundry, but I best try and stay focused on finishing the current projects.

I found a place close by that sells zamak 3 and it is probably close to the mazak used for pumps. I'm still trying to confirm that though.

Re: Marzak

Posted by robert_tuck at August 08. 2017

I remember being warned not to angle grind or torch galvanised tanks in lofts ,something about cyanide fumes!.

Re: Marzak

Posted by Dan Field at August 08. 2017

How do you make cyanide from zinc plate?!

Re: Marzak

Posted by George Phillips at August 08. 2017
I think zinc cyanide is used in plating the metal, Dan. When I was an apprentice we were warned that welding galvanised pipe was a no-no unless a pint of milk was available. Before you ask - I don't know! george

Re: Marzak

Posted by Dan Field at August 08. 2017

True but I thought galvanising was dipping it in molten zinc, not electro plating? But I'm not a metallurgist or a plater!  I do know that welding galvanised should be done with respiratory protection because of zinc toxicity.  I used to hold my breath, as when we cut asbestolux board! 😱

Re: Marzak

Posted by Barry Carson at August 08. 2017

 me mate ended up in hospital some years ago after welding some galvanized plates to his landrover using gas bottles. his face swollen like a cabbage patch doll and feverish. he told them what he had been doing. a chap with a knowledge lump told him it was due to the white fluff that floats off when galvanize is heated up that caused the problem.

Re: Marzak

Posted by Dan Field at August 09. 2017

Yep, that's why I held my breath! No idea what the white fluff is tho?!

Re: Marzak

Posted by Barry Carson at August 09. 2017

i forget what he said the technical term was for it Dan but it floats around in the smoke of the weld when the galvanize is burnt off.

Re: Marzak

Posted by david_evans at August 09. 2017

Without going back into my long forgotten apprenticeship notes, I thought that the zinc along with antimony was incorporated to make the castings sharper, like car door handles for instance.

One of our branch members has smashed up a MGF engine and cast a manx barrel and head from the bits, His next plan is to break up a Ferrari wheel for a set of magnesium alloy crankcases. He says the local foundry that used to dabble in this sort of thing used to catch fire every couple of weeks.

Re: Marzak

Posted by Dan Field at August 09. 2017

Well magnesium does burn quite well!

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