Author Topic: SRM oil pumps?  (Read 1633 times)

Online BSA_54A10

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Re: SRM oil pumps?
« Reply #15 on: 24.12. 2018 23:02 »
Over the last 30 years I have accumulated a few A10's.

I have had two of the original (Mazak) housings fail (crack and break away) in the thinner drive spindle area.

Others have shown signs of the metal crumbling away.

Not surprising that a 70 year old material,that was specified more for cost saving, than metallurgical quality (ie material was cheap), suffers fatigue failure.

I work in the fluid power industry; the only application of this material in a gear pump I have ever seen, is by now defunct manufacturers of British motorcycles.

All of my machines have a replacement high quality pump: some SRM, some cast iron).

Richard
Total & utter crap.
The zinc based alloys used were metallurgically  a very sound decision.
The EXACT SAME ALLOY has been used for decades in carbs, injection pumps & turbos.
Even today the tonnage of Zn based alloys is nearly 2/3 the tonnage of Aluminium/\.
Mazark by the way is a trade name for around 20 different zinc based casting alloys, and not a specific metal.
It is the perfect material for pressure tight cast to size high precision castings and is still used for that purpose today.

The simple fact is BSA did not factor in a 70 year service life. THIS IS NOT A MATERIALS FAILURE .
Your A 10's had a 90 day warranty in the USA and 12 months in Australia so the minimum service life of any part was the 12 month warranty period.

BSA knew what the average service life of a motorcycle was back then ( around 25 years from memory ) and so they designed the bikes to go that distance.
Remember that in the day it was new rings & big ends at 30,000 miles for BSA's but 50,000 miles for Triumphs because they used better slipper materials.
However no one puts Schit on the slipper material.

And by the way, MAZARK was not cheap. It was a branded alloy so BSA had to pay royaltities for using it.
It was however easier to machine and suffered substantially fewer machining failures than making them from cast iron.
So if you consider using a material that had a better than 90% acceptance rate over one that had a 30% quality failure rate then yes it was a cheaper option than the cast iron pump.

Oh and by the way just about every automotive oil pump, the one in your car right now is made from the same
DEFECTIVE CHEAP & METALLURGICALLY UNSUITABLE MATERIAL
so you better go out right now rip it out and toss it  in the scrap bin.
Bike Beesa
Trevor

Online Greybeard

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Re: SRM oil pumps?
« Reply #16 on: 24.12. 2018 23:33 »
Whispers: happy Christmas!

Online orabanda

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Re: SRM oil pumps?
« Reply #17 on: 25.12. 2018 00:57 »
Thanks Trevor,
All of your points appreciated; I have learnt a lot.
Merry Christmas
Richard

Offline Colsbeeza

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Re: SRM oil pumps?
« Reply #18 on: 25.12. 2018 01:22 »
What a great discussion. I recently dismantled my original Marzak oil pump, and found it a bit stiff, not being able to rotate it by thumb. I found the main shaft tight due probably to corrosion due to standing about for 20+ years. I probably did not assemble it properly 25 years ago.
In the process, I dropped the gears and of course had no idea where each had been fitted.
I inspected the casting, and found no defects, polished the end plate with oiled 1200 Wet-n-dry on a glass plate, and re-assembled it. On tightening the screws, the gears locked up fairly tight. It took several iterations of the gears to find the best fit to reduce friction. Finally I found a combination which worked well.
The pump works well, gives 60psi cold and 40psi hot.
I may eventually get a new pump, but until I get trouble, will stick to the original.
Col
Colsbeeza
Australia

Online BSA_54A10

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Re: SRM oil pumps?
« Reply #19 on: 25.12. 2018 01:45 »
And a merry one to you.

Sorry to jump off the pan handle but I was a metallurgist and even taught it for a long while after I left the industry.
Way back , illiterate wafes got a job as a copy runner in a printing works.
They ran around all day clutching galleys of type in their grubby hands to hopefully be delivered to the correct copy reader then eventually back to the sub editors then to the comp shop to be pasted tgethe to make a page then back down to the foundry to be set in metal.
Eventually these urchins got to do some menial writing then eventually reporting and finally graduated to journalist if they could manage to convert the bumf the factories supplied into words that the factories approved of and Joe Public found plausable.

From the pens of these totally engineering illiterate came all sorts or rubbish, like picking up on the term "Pot Metal".
Pot metal was a foundry slang term applied to everything that was melted in a crucible rather than in a "real " furnace like a blast furnace, cupola or rotary hearth.
Naturally all of these were superiour to melting in a pot so by vitrue of this all "pot metals " must be inferiour and there fore make inferiour parts.

There is a big difference between selecting the best metal and the right metal.
Rolls Royce used the best metals and were perpetually on the verge of and in bankruptcy .
Ford chose the right metal and made a fortune.
Pilgrim pumps were piston pumps and long considered the state of the art in pumps.
They were made from cast iron because the pistons needed a fine hard & strong surface to run against.
Some were made from bronze but initally all were fitted outside the engine and plumbed in.
Thus any pump not made from cast iron or bronze had to be inferiour, to a 4 year olds understanding.
Thus it went into print and got repeated & repeated till by the face book principle it has to be true.

In a gear pump. the actual pumping is done by the gears so what is important is the fit of the gears into each other.
And yes excessive side clearence will allow the pump to leak, but that is not the critical part, the gears are.
The body just needs to maintain the position of the gears relative to each other and be pressure tight so must be rigid & be able to be cast without porosity defects.
Zn is a bearing metal ( yes others are better ) and is pressure tight through very thin wall thicknesses so fits the bill quite well.
IT also has an expansion co-efficient close to aluminium and can be made to almost exactly replicate that of the Al-Si used for the crankcase casting.
Thus is does not leak, will warp & contort to comply with crankcase movements, is easy to machine WITH THE PRODUCTION TOOLING OF THE DAY and takes a fine finish.

Also we have to remember that it was deigned to be used with strait 30 or 40 oils, not multigrade oil which is full of aditives some of which can attack the pump chemically.

Even in the day of computer controlled carbide tooling that is accurate to .000001", SRM chose to machine their poump from extruded alloy to get the pressure tightness & rigidity necessary to work reliabily.
Bike Beesa
Trevor

Offline bsa-bill

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Re: SRM oil pumps?
« Reply #20 on: 25.12. 2018 10:09 »
Well said Trevor

I've no doubt SRM pumps are everything  they are said to be, but hey the majority of us are riding around on 70 + year old machines designed for commuting with much original stuff in them, my high tech 1/lt 3 pot fiesta is great for commuting also but I  doubt it will be 70 odd years from now.

Merry  Christmas all
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online Rex

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Re: SRM oil pumps?
« Reply #21 on: 25.12. 2018 11:46 »
Trevor, what's your take on BSA original pumps stiffening up when unused (all models) and that stiffening being attributed to the Mazak "swelling"?

Offline ellis

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Re: SRM oil pumps?
« Reply #22 on: 25.12. 2018 13:53 »
BSA_54A10

Always send your copy to the proof reader before it goes to print so that any spelling mistakes are corrected.

ELLIS  ex stereotyper.    *beer* 

Online BSA_54A10

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Re: SRM oil pumps?
« Reply #23 on: 25.12. 2018 21:55 »
Trevor, what's your take on BSA original pumps stiffening up when unused (all models) and that stiffening being attributed to the Mazak "swelling"?

My initial thoughts would be bollocks.
Oxide growth certainly but swelling of the alloy at room temperature not top on the list of possibilities .
Zinc based alloys do not adsorb much hydrogen from the atmosphere as aluminium alloys will.
And even if they did, energy has to be applied to allow the trapped gas atoms to travel through the lattice structure then bump into each other and for a hydrogen molecule.
Then you need thousands of these events to put enough strain on the lattice to cause the layers of atoms to slide over each other and cause the item to grow.

OTOH it does not take any energy for the surface of the metal to oxadize, in fact it takes energy to prevent this happening.
The corrosion product of zinc based castings can have a variety of structures depending upon how many water molecules get included.
If there is little water the corrosion layer is translucient and as such quite hard to see with the naked eye .
You do not see the oxide layers that have formed on your carb body & slide on concentric carbs but it is sufficient to lock the slide in place then rip lumps of zinc off the surface of either the carb or slide. The process is called stiction ( joining together ) & gauling ( ripping surface atoms off )
Now this happens between a body & slide where the space is around .005".
It will also happen around the hole in a pump body where the running clearance is in the order of 0.0005"

The number 2 culprit would be plain old slump.
Nothing that we think is solid is actually solid and over time nothing greater than gravity will cause everything to go "pear shaped".
It is just some, like glass & lead will do it faster than others like steel & titanium but they all do it
So if stored for long enough not properly supported I would expect pump bodies to distort over time.
Even the Platinum-Irridium bar which used to be the standard meter distorts over time which is why it got replaced with an atomic measurement, and even that has found not to be as stable as we had hoped for so was reciently upgraded again.
Bike Beesa
Trevor

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Re: SRM oil pumps?
« Reply #24 on: 25.12. 2018 22:05 »
BSA_54A10

Always send your copy to the proof reader before it goes to print so that any spelling mistakes are corrected.

ELLIS  ex stereotyper.    *beer*
Ellis.
I was a 75wpm typist at 60%.
Spell checkers slow this down massively particularly when they seem to be getting more & more American every day.
I am dyslexic so reading for fun was & is a painful process.
Then having spent 20 years training in science /engineering where you have to read for content, you skim & scan rather than read words thus the more educated I got the worse my spelling got.
However you are more than welcome to proof & correct any galley of mine should you feel inclined to do so.
If it is any comfort to you, the humanities students used to experiment on students to see if there were similarities in eye movement, reading speeds, short & long term retention & spelling within disciplines.
My spelling was smack in the middle for engineering students and in the lower 20% or science students
Science & Engineering students were way above humanities students in speed, retention & comprehension
Bike Beesa
Trevor

Offline Colsbeeza

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Re: SRM oil pumps?
« Reply #25 on: 25.12. 2018 22:31 »
As regards swelling, I mentioned earlier that the main gear shaft was tight in its fit through the alloy. I measured the shaft diameter and ran the appropriate drill gently through the alloy casing. The material removed looked like corrosion to me, not swelling of the alloy. This pump had not been used for 25+years, but was installed.
I also forgot to mention that I was not happy with the seal of the end plate - I could see leakage happening, so used the slightest smear of red hermetite, being well aware that I did not want any sealant in the oilways. Sofar so good!
Cheers Colin
Colsbeeza
Australia

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Re: SRM oil pumps?
« Reply #26 on: 26.12. 2018 01:20 »
hey trevor some very interesting stuff on this metals subject and breathing as well, I was gifted some plastic packed grease nipples years ago which were for use on aircraft-RAF old stock. they had use by dates on each pack , I often wondered and still do as to why a grease nipple has to have a use by date?

Online BSA_54A10

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Re: SRM oil pumps?
« Reply #27 on: 26.12. 2018 03:41 »
Everything that goes into aircraft has a use by date.
There is a small spring behind the ball which like a valve spring will eventually loose tension.
Bike Beesa
Trevor

Offline ellis

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Re: SRM oil pumps?
« Reply #28 on: 26.12. 2018 12:24 »
BSA_54A10

That was just an observation and not a criticism. Please accept my apology i didn't mean to offend.

Merry Christmas to you all.

ELLIS   

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Re: SRM oil pumps?
« Reply #29 on: 26.12. 2018 14:51 »
cheers trevor never thought of that, everything has a reason . it struck me as being odd but now explained *beer*