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May 8th, 2022
Thread Like Summary
Allan G, Beach, Chip H, gavin eisler, joe czech, kommando
Total Likes: 15
Original Post (Thread Starter)
by joe czech
joe czech
i'm installing a new SRM oil pump in my 66 Spitfire. in with the kit is a new, pump drive "worm" gear that threads onto the crank drive gear (timing side). there are 4 parts - flat washer (install first), the worm gear w/ LH threads, an indexing washer, followed up by a retaining nut. QUESTION - any kind of torque requirements on the worm gear? figure it would be the same as the stock A65 gear, but not finding any details in the service manuals. guessing since it's LH threads it's probably self tightening. nothing in the instructions that came with the kit.
Liked Replies
by DavidP
DavidP
Watch out for scoring on the piston of the SRM OPRV. Using stainless for this piston is insane!
2 members like this
by Allan G
Allan G
I keep this piston on my desk from the stainless oprv that I had on mine, it’s been on there for a couple of years now so please excuse the small dents etc, but the lines “rash” marks are from how it came out of the body.

The bike had frequent oil changes, oil filter etc etc etc. I only checked mine after it was mentioned to me as an issue by someone else, my mate kept getting the oil pressure light on his unit and we decided to check his (his looked the same) fitted a ball type one from Lyford Classics and it’s been fine ever since and no oil light on when running. So that’s on 3 units.

It’s your money and it’s your choice. But as the subject was raised I’m putting my 2c worth in.

I also believe the term is stitachion (although I cannot spell it or get close enough for my phones dictionary to work out what I’m trying to spell, so I stick with galling as I can spell that laughing )
Attached Images
2 members like this
by Tridentman
Tridentman
Kommando has summarized the situation very well IMHO.
Running the same materials against each other is an engineering no-no.
It is the the sort of thing that you give an apprentice a bollocking for if he does it.
There is no excuse for any half competent engineering company doing that.
It is not as though there is a shortage of other materials to use and the unit is running in a very easy situation with oil all around it.
SRM have no excuse and should be rewarded for their incompetence by people not buying the product.
Just my two cents worth of course.
2 members like this
by gavin eisler
gavin eisler
The book figure for this, oil pump worm LH thread, 35 ft lbs, from the 71 manual. 1970 manuals have28 / 30.
its important to fit the washer between the worm and nut, the worm will chip if it is left out.
1 member likes this
by Beach
Beach
Originally Posted by joe czech
Originally Posted by DavidP
Watch out for scoring on the piston of the SRM OPRV. Using stainless for this piston is insane!
is this a common SRM OPRV problem? not that i'm well versed in OPRV's but first time i'm hearing of issues with the SRM assembly. ???? haven't opened up the part, but i was assuming it was of a conventional ball/spring design. ?????
Seems to be a common problem with them. Stainless has a tendency to gall, causing scoring, allowing oil pressure to bypass. Good looking kit but originals work well enough for me not to take a chance.
1 member likes this
by joe czech
joe czech
Chip - thanks for the reply - figured it would be the same as the stock OE drive gear. got an email in to SMR, but hope to get the bottom end back together today. hope an on-line answer would be quicker. anyway, see you're from Sharon Pa - had a few meals at Quaker Steak and Lube - one of my favorite places for wings!
1 member likes this
by KevRasen
KevRasen
Agree SS on SS might not be the best practice for mating materials but I've got 3 SRM OPRV in sporadic, regular service over a period of 10 years for the oldest and haven't noticed any scores of concern, scores are just as likely to be from contamination in the oil as "galling" SS. Considering the SS components are pretty much submerged or at least permanently coated in oil then I don't see galling as a concern.
I am familiar with SS galling in my previous life as a steelwork fabricator/erector and most times it would be galled threads which in turn only galled because they were damaged in some way, often hardly visible, or over stressed which would soon end up as a locked solid arrangement. i.e it takes some sort of surface defect to initiate the galling , which on 2 machined mating components covered in oil shouldn't be an issue, but that's just my experience.
1 member likes this
by Kev Ev
Kev Ev
Originally Posted by Allan G
Originally Posted by KevRasen
Agree SS on SS might not be the best practice for mating materials but I've got 3 SRM OPRV in sporadic, regular service over a period of 10 years for the oldest and haven't noticed any scores of concern, scores are just as likely to be from contamination in the oil as "galling" SS. Considering the SS components are pretty much submerged or at least permanently coated in oil then I don't see galling as a concern.
I am familiar with SS galling in my previous life as a steelwork fabricator/erector and most times it would be galled threads which in turn only galled because they were damaged in some way, often hardly visible, or over stressed which would soon end up as a locked solid arrangement. i.e it takes some sort of surface defect to initiate the galling , which on 2 machined mating components covered in oil shouldn't be an issue, but that's just my experience.

I see your point, Just seems odd when the SS item will gall and also stick, and yet the original one does not. Also those oil contaminants would make it into the timing side bush and big end shells and with that level of wear the journals will be toast in no time.

I've worked with Stainless Steel, mainly 304 and 316L, for the past 40 years and the problem that people have with it is mainly due to a lack of lubrication.

Stainless work hardens if you allow it to 'rub' against anything without lubrication. I found this out many years ago as an apprentice when I tried to ram a 3/4" drill bit through a piece of St/St round bar in a Colchester Lathe without using coolant. I was too inexperienced to realise that all the effort it was taking and the rumbling noise was because the HSS drill bit was being totally obliterated by the hardened stainless steel, caused by the lack of coolant/lubricant. I got a right good rap on my knuckles with a 12" rule (my mentor at the time used to rap me on the knuckles with it when I called it a ruler too, shouting a ruler is a King or Queen not a measuring instrument! Good old days) and a detailed explanation of how to work St/St. Slow speed, heavy feed and plenty of coolant. If you let your tools dull, or rub too much without cutting, expect them to disintegrate.

Stainless is fine as long as you use it correctly and lubricate it.

Use the correct grease on all threads, when assembling.

Cheers, Kev E
1 member likes this
by kommando
kommando
Galling is at its worse when the 2 rubbing surfaces are made from the same materials, its an engineering no no that is ignored too often. It happens at a molecular level, the molecules of both surfaces fuse on contact and as both molecules are the same size then it happens more when the materials are the same. For the sake of using brass instead of stainless for the plunger its easily overcome but there must be a big advantage to SRM that I cannot fathom. Amal Concentrics have the issue which after years has finally been cured by anodising the slides.
1 member likes this
by DMadigan
DMadigan
The galling problem is probably worse on a Triumph with the plunger pump where the pressure rises and falls with each rotation of the pump so the piston is constantly moving. Unless both piston and bore are polished there will be peaks in the surface that will hasten the scoring.
Differing materials is why the pump body is either mazak or iron and the shafts and gears steel.
1 member likes this
by Allan G
Allan G
Originally Posted by joe czech
Originally Posted by Allan G
I keep this piston on my desk from the stainless oprv that I had on mine, it’s been on there for a couple of years now so please excuse the small dents etc, but the lines “rash” marks are from how it came out of the body.

The bike had frequent oil changes, oil filter etc etc etc. I only checked mine after it was mentioned to me as an issue by someone else, my mate kept getting the oil pressure light on his unit and we decided to check his (his looked the same) fitted a ball type one from Lyford Classics and it’s been fine ever since and no oil light on when running. So that’s on 3 units.

It’s your money and it’s your choice. But as the subject was raised I’m putting my 2c worth in.

I also believe the term is stitachion (although I cannot spell it or get close enough for my phones dictionary to work out what I’m trying to spell, so I stick with galling as I can spell that laughing )

the piston photo from your unit is definitely a cause for concern. did you contact SRM over the galling issue? i've read the term, "common problem with them" -- any statistical data out there? no flames, but i'd like to hear SRM's side of the story.

To be honest Joe, I checked it, found what I found and changed it. That was probably 7 years ago now, its probably 4 years since we checked my mates and found the same. I'll add also that I have never had any issues with SRM, they have been a great company to deal with and I praise every other product that they are selling, their pumps are great and I haven't found any other valves that are as good as their plasma hardened ones. Unlike some vendors they do supply the correct clearance bearings (the A65 gearbox bearing seems to be a tricky one to obtain, but these sell the correct C3 clearance bearing (others sell the CN/C2 clearance under the same PN), price wise they are also very comparable with other sellers, maybe a pound or two more but for a much better version of the item.

So I have no intention of rocking the boat with SRM, this just happens to be their only product that I won't use again.
1 member likes this
by BSA_WM20
BSA_WM20
In theory the PRV should not gall because it should always be oiled and the oil should prevent the oxides on the surfaces from growing into each other.
It actually worked fine in Amal carbs where the petrol gets adsorbed into the porus zinc oxide and both lubricates the slide & prevents galling .

The problem is we don't use the bikes the way the designers intended.
From age 13 to 30 I rode almost very day & never had a problem with a slide galling in the carb body.
Now days when I can go for months or even years between starting an engine, galling is a problem.
Same story for wet sumping , never happend when the bikes were ridden regularly .
Now it is a perpetual problem.

HAving said that, I would agree that making prv in all stainless now days when SRM know the average useage patterns was not good engineering .

The other thing that has to happen is the oxides have to be very strong
Steel does not gall because it's room temperature oxide ( rust ) is very weak so breaks way from the surface.
However if it was hot formed and has a layer of mill scale ( FeO) covering the surface it will gall .

And FWIW Stiction is simply the resistace of two surfaces to slide over each other from a stationary position .
It is actually the "static friction" as comparred dynamic friction which is the resistance of 2 surfaces to continue to move over each other and is generally substantially lower.


So lucky you can not spell Stiction .
1 member likes this
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