O ring posts from the lube tread.

hey guys, quick background on my situation:-

So I took apart my Lumintop Tool yesterday and cleaned all the threads of the previous lube (was using NiteCore silicone lube before). so I took out the oring with a tweezer, being careful not to damage it, cleaned it then rolled it between thumb and forefinger with some superlube. Then I placed them back using my thumb as leverage while slightly stretching them to get it back into the groove. So basically a straightforward cleaning.

Today I noticed that on both oring there are some marks, like very slight cuts and nicks , the oring is still whole, not split or broken.

https://www.dropbox.com/s/qe6gaszmv38tcdu/IMAG2773.jpg?dl=0


and my questions:-

Any ideas how this happened?, I did happen to tighten it a bit hard a few times after the above cleaning job so I'm not sure whether that was the cause.

Also, should I just replace the seals with the spares or is it still serviceable as it is...reason im hesitating is because I don't know where to get more spares just in case the included ones are used up.

In addition, was planning to clean my other lights, obviously on hold now until I figure out what went wrong. I'm pretty sure it's not due to lube compatibility since superlube is basically ok with almost anything aside from natural rubber, which I'm pretty sure those are not what oring are made of nowadays (is it?).

Re: Comprehensive Grease and Lube Thread

Not sure what damaged your O ring, but I would not be concerned about using your spares as O ring are that cheap you can just get some more.

Re: Comprehensive Grease and Lube Thread

you're right, a quick search on fasttech revealed 50 pc/pack of orings at about 2 dollars.

Re: Comprehensive Grease and Lube Thread

xzel87 said:

you're right, a quick search on fasttech revealed 50 pc/pack of orings at about 2 dollars.

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Happy New Year to all of you
know your compound,
Buna N should be used generally with no affliction with 99 percent of lubricants out there and their happen to be the least expensive being an hydraulic seal compound and are only vulnerable to ozone during storage, once in service little chance to be exposed to such.
if any one of you come to Las Vegas for the Sho Show or Candle forum parties, please stop by booth 6112 in Tactical area for a visit and a little gift ot light waiting for you.

--
Christian StClaire NasaTech Create the Future "2 Stroke Engine 4000 To 1 Gasoline/Oil Mix Ratio" www.Nano-Oil.com

Re: Comprehensive Grease and Lube Thread

xzel87 said:

you're right, a quick search on fasttech revealed 50 pc/pack of orings at about 2 dollars.

Click to expand...

My post was double posted for some reason so I removed dup content
--
Christian StClaire NasaTech Create the Future "2 Stroke Engine 4000 To 1 Gasoline/Oil Mix Ratio" www.Nano-Oil.com

Re: Comprehensive Grease and Lube Thread

okay guys need some help here, where do I buy orings from?, All that I can find from oring kits seems to be too thick?, especially those set kits.

I ordered just one pack 12mm outside diameter to try on my AAA light..turns out it was too thick (1mm cross section)...I know that for bigger diameter lights we can just pick a smaller oring and stretch it over, but it doesn't work for thin lights like AAA lights.

Re: Comprehensive Grease and Lube Thread

If you are in a pinch, try home depot. They have a half way decent array. If not try the OEM of the light to get the exact size and then search.

Re: Comprehensive Grease and Lube Thread

No home depot at my place, have to order everything online for better prices, locally some stuff are sold at cutthroat prices

All is not lost though, turns out the pack i bought fits my MT21A better than it's original o-rings, so I have plenty spares for those. Guess I'll have to look for smaller diameters and try to stretch to fit.

Re: Comprehensive Grease and Lube Thread

I too was going to ask about o-rings. Specifically, I need to replace the one for my Sunwayman D40A, but could do with some spares of common sizes. The only website I know of that sells them is cnqualitygoods, and I've seen them on eBay. Home Depot is no use to me either, as it doesn't exist in the UK.

My biggest problem is that I'm not sure how o-ring measurements are specified, so I don't know what I should order. I've noticed that there is sometimes a huge difference between the diameter of the ring "at rest" compared to the size it is stretched to fit, although I suspect the manufacturers are often choosing the wrong size themselves. The D40A ring was actually the opposite. It was quite loose and as a result, got sliced after getting caught on the head, within the first month. Since then I've just been using it with no o-ring.

Taking the D40A example concretely, how would I go about deciding what size of replacement to order? I can measure the gauge with a calliper, that's easy. Measuring the diameter isn't so easy. Are the measurements usually based on the at-rest inner diameter of the o-ring itself, or the size of the barrel it's intended to fit around when stretched? Measuring where the o-ring goes with a calliper, I get 37.7mm, so do I need a 37mm o-ring? Or do I subtract a few mm so that the o-ring will stretch to fit more securely. If so, how much?

Also, are there different rubber compounds to worry about? I would imagine that a gasket intended to seal an engine or for use in plumbing would require a much higher force to compress and thus, even at the same diameter, could make the seal on a light a bit too tight.

Re: Comprehensive Grease and Lube Thread

most orings can be stretched a lot without breaking, mine for example, were 12mm outside diameter orings with 1mm or so gauge, I was able to fit it to my MT21A (had to stretch it a lot though) and it actually seals better than the original orings. I will upload the pic of the original and smaller orings for your reference. I'm now looking for oring kits that come with assorted sizes and I suppose it'll be trial and error till I get a suitable one for my Lumintop Tool.

Re: Comprehensive Grease and Lube Thread

robert.t said:

I too was going to ask about o-rings. Specifically, I need to replace the one for my Sunwayman D40A, but could do with some spares of common sizes. The only website I know of that sells them is cnqualitygoods, and I've seen them on eBay. Home Depot is no use to me either, as it doesn't exist in the UK. ... Also, are there different rubber compounds to worry about? I would imagine that a gasket intended to seal an engine or for use in plumbing would require a much higher force to compress and thus, even at the same diameter, could make the seal on a light a bit too tight.

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Good observations. In layman's terms, loose is bad. I believe many manufacturers are oblivious to the AS568D and ISO 3601 standards. Therefore they not only choose the wrong o-rings but also bugger the gland dimensions entirely. It's less of an issue on a flashlight than it would be for say a hydraulic system on a dredge but it is still deplorable nonetheless.

I used your measurement of the gland diameter to calculate the ID (inside diameter) of the o-ring. The ID should be 37.33mm-35.90mm or ~36.96mm ideal according to AS568. However, since I don't know groove width, piston dia, bore dia, etc... that's is the best I can do. A rule of thumb is that the maximum volume of the o-ring should never exceed the minimum volume of the gland.

To find a replacement you're going to need to estimate the CS (cross section). If I had to take a guess, the proper o-ring size would be AS568 -127 (CS is 3/32") since it's a big light. Also, the calculated ID falls between -028 and -029 sizes. The -0xx sizes have 1/16" cross section, a common CS for flashlight applications. If you do end up experimenting with different sizes do not go above the maximum calculated ID 37.33mm, otherwise you won't have a proper seal at all.

As far as buying o-rings, The O-ring store is the best place I've found. I don't know if they ship to the UK though... If not try to find a place that sells proper AS568 or ISO 3601 (metric) sizes. Kits and hardware shops aren't bad but a lot of that stuff comes in non-standard sizes and you might not know what material you're paying for.

Edit: there's always a chance that Sunwayman follows a standard other than AS or ISO (or doesn't follow one at all). Some of the other standards are mentioned here. Buna-N (aka Nitrile), EPDM, and Viton are the some common materials. (Personally I prefer fluorosilicone, same ones Jason of Prometheus Lights uses.) For hardness, stick with duro 70.

xzel87 said:

most orings can be stretched a lot without breaking, mine for example, were 12mm outside diameter orings with 1mm or so gauge, I was able to fit it to my MT21A (had to stretch it a lot though) and it actually seals better than the original orings. I will upload the pic of the original and smaller orings for your reference. I'm now looking for oring kits that come with assorted sizes and I suppose it'll be trial and error till I get a suitable one for my Lumintop Tool.

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While it is true that they can stretch quite a bit, the integrity of the seal is only preserved within the standard specified range of stretch. A tight seal may actually be a poor seal for a variety of reasons.

It's always important to replace an o-ring with one of the same AS568 (or metric) size. O-ring gland calculations take into account volume swell, squeeze, compression, stretch, the extrusion gap, etc... If the flashlight maker followed the SAE standard for o-ring gland design(currently AS568 revision D) then using the wrong size o-ring can cause seal failure.

Re: Comprehensive Grease and Lube Thread

Thanks Isaac, that's about as comprehensive an answer as they get! Apparently it's even more complicated than I thought. A simpler answer would be nice, but I like knowing this kind of stuff. Slightly confused by the term "gland" though: just another word for the groove that the o-ring sits in?

I suppose I also forgot about taking the inside diameter of the head - using the terms on your diagram, that would be the "bore". The 37.7mm measurement I took earlier would be the "groove". I'll need to read the links later when I have more time and make sure I'm understanding it all properly.

I tried the calculator and got a CS value of 0.38, which seems a bit wrong as I used an estimated bore of 39 on the basis that I already measured the CS of the old o-ring at ~1.25mm. 0.38mm wouldn't create a seal if the gap is 1.3mm. I must have made a mistake somewhere. Had no idea what the CS tolerance should be, so I copied your figure of 0.08 as a hopefully sensible default. I'll try it again with a correct measurement later, but hopefully you can point out where I went wrong and how to calculate (or find out) the tolerance figure - is that dependent on the o-ring manufacture specifications?

Re: Comprehensive Grease and Lube Thread

You're welcome and I'm sorry for the confusion mate. I included the technical stuff in case anyone was interested (I should not have included that calculator). No need to read the links it if you don't want to. Truthfully, the technical info is more relevant to the design of the flashlight and choice of seal. Don't worry about all the other measurements, the groove/gland diameter and the o-ring ID and CS are all I really need to know.

If I understood you correctly, the original o-ring CS is about 1.25mm, right? That's a highly unusual size. CS 1.78mm is the smallest for both AS568 and ISO 3601 (besides the three smallest o-rings: -001,-002, and -003). CS sizes generally change in large increments (i.e. 1.78mm, 2.62mm, 3.53mm, etc...). That makes it easier to estimate the proper size for a replacement.

Correct, gland is just the engineering term for the groove.

Let's get the numbers straight and I'll try to find you something that will fit. Here's what I have so far:
Gland/groove diameter: 37.7mm
Original o-ring cross section: 1.25mm?
O-ring internal diameter (calculated): 35.90-37.33mm

Re: Comprehensive Grease and Lube Thread

Any Scuba Diving shop will carry a nice selection of Buna N O-Rings + EP- Ethylene Propylene aka EPDM

EP is over twice as expensive then Buna N and is not compatible with Hydro Carbon based Lubricants, it will inflate proportionally to the amount of fluid it is exposed to.

Re: Comprehensive Grease and Lube Thread

IsaacL said:

You're welcome and I'm sorry for the confusion mate. I included the technical stuff in case anyone was interested...

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Thanks again - don't worry about the information being too technical, it's very welcome. Although I still haven't had time to read it all yet, I definitely will and I'm sure others will find it interesting and useful.

Your numbers look about right and sensible. 1.25 is roughly what I measured, but between squisiness and caliper tolerance it could just as easily be 1.5mm to spec. I took some more careful measurements and I'm getting 1.37mm. Cnqualitygoods have 1, 1.5 and 2mm cross-sections listed, each available in lots of diameters. They don't say so, but I assume that is the inner diameter, as that seems to be the standard measure. Not sure why they are so different to ISO, but maybe they are rounding off the sizes and 1.5 is actually 1.78. That said, mine is definitely not that thick. It is indeed pretty thin compared to its diameter, unlike those on many smaller diameter lights.

Inner diameter is harder to measure, but based on length/PI I get 37.24 which is very close to your calculated 37.3. Bear in mind that my length measurement might not be too accurate given that it's stretchy rubber that doesn't like staying straight to be measured!