Waqas, Michael and Thomas,
That's great, guys; the cause is furthered. Waqas' data jogs my memory and Michael's website gives us an excellent product offering in metric specs, something I didn't find in my searches. (Must keep in mind that only a few of the sizes are given in metric in our TM; the tricky ones -for some of us, at least- are in British Standard and/or MB part # --and those are the ones costing close to $25 each when available from MB.) My notes reflect the chase down those rabbit-holes, ending up in inch-fractional because that's what the supplier in Maryland works from – it’s even the way the O-rings I bought are referred to on the purchase invoice: no part #s or other reference. But of course our pumps are metric and pretty much have to use metric 'rings, and in whole-number sizes for the most part. Now the pursuit turns to the metric....finally.
Waqas, it looks like you picked out a page of notes from part-way through my earlier odyssey, most likely looking to have specifications in metric notation. But those numbers reflect precise equivalents to specifications in other conventions and I think are likely not available as product in those exact sizes. Now that Michael shows us what's available in metric O-ring product; we can verify with measurements from actual pumps and hopefully someone will eventually put the authoritative seal on it with the factory specs from some arcane MB reference materials. Meantime, although I think the inch-fractionals will serve to build a pump, surely all would prefer our O-rings in metric specs.
The material in the O-rings I bought from Maryland Metrics is Nitrile 70, the industry standard for service in petroleum-exposed applications, with specific mention of fuels. The premium material most readily available is Vitron, which is apparently a bit less convenient to get in all sizes, more expensive and considered by most --including our TM-- to be unnecessary overkill. (The originals went 30+ years, after all.) The 5mm sealing O-ring on the impeller shaft of the old/tall pumps might be one place where Vitron could add, since failure at that point on those pumps seems to be pretty much the only cause of pump failure save for gelled fuel crud in the impeller chamber. I really don't know anything of Vitron's possibly enhanced performance as a seal on spinning shafts, but it would be interesting to know.
O-ring sizing convention is by inside diameter. The smallest number -- given second in many cases, first in others-- gives the diameter, or cross-section, of the material itself. (I haven't been using 'cross-section' but think it's better for clarity, will start now. Another bit of help from Michael's O-ring West site.)
In order of disassembly as dealt with in the TM: Old Pump [5mm shaft seals at the end.]
* Largest 'ring, located inside the cover of the impeller chamber. 2mm cross-section ("CS" on O-Rings West charts) and an inside diameter of (most likely) 70mm. The article in our latest Pagoda Notes (George, Abbas and Eugene) refers to this one as being 70mm in the new style pump and gives an MB part # as well.
Note: our parts list needs to become two lists, as the old and new pumps call not so much for different sizes of 'rings' --I think-- as differing numbers of each. Sizes 67 through 73, etc. are available in 1mm increments. Seems likely to be 70mm for both pump styles.
[PN article also refers to another large 'ring which appears only on the newer pump; on p.3 it refers to both large 'rings, giving one the 70mm size and the other 71mm. I’m surprised to see these O-rings vary by just 1 mm; normally you’d expect them to be identical absent any outside influence requiring variation.]
NOTE: this is certainly a learning curve for me. I had been focused on the old/tall pump because mine leaks. The PN article treats the new/short pump. It becomes apparent that the old one has a cap/lid on the motor chamber while the newer model's motor does not, coming away from the impeller 'department' as a closed-ended "can". It appears that old/tall pumps will need just one of the large 'rings and the newer/short style takes 2 of them. Please forgive my being over my depth here, and recall that my original intent was merely to equip myself with 0-rings for going into my own leaky pump -- which sits, leaking still, and I, far removed from it, can only infer and extrapolate. Oh sigh.
* In the older pumps there are 2 middle-sized O-rings sealing the motor area, between the pump and motor section and between the cylinder containing the armature and that cylinder's end cap. These are the 53.67mm 'rings in Waqas' list. The "O- Rings West" site lists 54mm x 2 and its neighbors as available in 1mm increments. The Pagoda Notes article identifies the one on that new-style pump as 57mm x 2 (between the motor 'can' and pump areas). Here we may have a problem. My dimensions for these 'rings on the old/tall pumps come from the TM rebuild (Bob Smith), given as a British Standard coding and developed by me through inch/fractional dimensions to the metric equivalent --54mm, unless I messed up somewhere in the process. (I can review that process, but not for weeks.) It seems reasonable that the dimension here might change with re-design of the motor, but a little odd if the change is to a larger diameter for a pump in which the field winding is no longer present; not impossible, just non-intuitive. I found no dimensional information on this 'ring in the recent Pagoda Notes article, though certainly much other good info.
This area is the most problematic in terms of getting to the exact specs we're seeking and points up the need for someone with a metric caliper and disassembled pumps of both styles -- and/or loads of experience with them -- to contribute from empirical knowledge by verifying all these diameters against the pump’s hard parts.
* Smaller of the major-sized 'rings. Applications: inlet and outlet covers, totaling 2. No drama here, one hopes. 36.27 x 2 as posted by Waqas. Michael's referral shows O-rings from 35.50mm through 38.00 by half-mm steps. I’m guessing 36mm for these; 36.5mm is also available. (The newer pumps break down differently in this area and may well require a different-sized pair of ‘rings at their ports. I haven’t found any mention of what dimensions are required here – and perhaps they use a different type of seal altogether.)
* Inside the top cover, 2 small O-rings are found on the studs. O-Rings West offers 2mm by 3.00 through 4.50 and beyond in half-millimeter increments. Looks like a toss-up between 3.50 and 4.00. Apparently none of these on short pumps.
* Shaft seal, 5mm x 1mm Just one is required, and only in the old-style pump. This is what the bellows seal works against, and some of our fellows have written of custom-sanding these 'rings for a better fit. When my supplier’s site offered another 5mm 'ring of a very slightly thicker cross-section I thought it might be useful for such custom fitting. 5mm x 1mm is given in our TM.
*? Shaft seal, 5mm x 1.5mm The O-Rings West site offers this thicker cross-section alternative. [the increase in the inch-fractional ‘rings I got was much less than the 50% bump available in metric.]
The 2 square cross-section seals at the electrical connections don't seem to be applicable to the old/tall pump. They do seem to be a challenge that will plague us increasingly in future newer-pump rebuilds.
O-Rings West imposes a $50 minimum charge per order of each metric size, so we still need a supplier as well as more precise and well-organized specifications. My Maryland Metrics supplier imposes $10 minimums, both for shipping and complete shipped orders; much better. And I can avoid that with pickup at their walk-in order desk.
But first I've got to get to the bottom of an apparent contradiction: how is it that a business named "Maryland Metrics" can only supply O-rings in English/inch specs? Surely there has been some failure to communicate. I’ll check it out.
Thomas, how goes it with you? Good heavens man, look what you’ve started. Actually, of course, it’s all been going on for some time; you just stirred it, which seems timely and welcome. Hopefully we can subdue the beast shortly, and you and I can enjoy our refurbished pumps……next spring?
)
I think I can contribute little more to this quest, at least for now. And I’ll be offline for a little as well. Regards to all.
Denny
