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British Mk7 helmet - everything you need to know

Article about: Guys, First of all, thank you for deciding to read this thread....I was gonna throw in an "SS" or "FJ" into the Thread name but thought better of it.... I'm starting this

  1. #101

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    'picked up a nice been-there example.....

    A purpose-made scrimmed-up net, reversed brow pad (foam side outer), shortened chin-cup strap (only one press-stud) and under the cover/net stuff the shell's been camo'd. I'm finding that a number of these have been de-horned ie the rubber liner retention rivets have been sliced off and I'm wondering why this is...can it simply be because they get in the way when covers/nets are applied...or was it a "thing"?????

    British Mk7 helmet - everything you need to knowBritish Mk7 helmet - everything you need to knowBritish Mk7 helmet - everything you need to knowBritish Mk7 helmet - everything you need to know

  2. #102

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    Quote by Composite View Post
    I'm finding that a number of these have been de-horned ie the rubber liner retention rivets have been sliced off and I'm wondering why this is...can it simply be because they get in the way when covers/nets are applied...or was it a "thing"?????
    Maybe more pertinent is exactly why NP/Morgan quite clearly and deliberately left several mm untrimmed protruding beyond the surface of the shell, on ALL models, completely across the range. The rivets have obviously been trimmed, but never flush to the surface, which would have been just as easy as the general cutting-back process applied. There has to be a sensible reason for this. Does it affect the security of the liner fitting, perhaps?

  3. #103

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    I think they HAVE to extend beyond the shell as it's the shell hole which the wider part of the rivet pulls back against...or have I missed your point? The long part of the rivet is pulled (or pushed) through the liner and the shell and then pulls back to the shell...the long sticky out part (sorry for the technical term) is then trimmed (roughly!) down

  4. #104

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    No, you've missed my point. I know how these things work (ie just as you described) as I have removed and fitted them myself. The stalk of the raw rivet is significantly longer than what is seen on a finished helmet. See pics on that old abandoned website, for example.

    What my question was is why the OM (this applies to them all) chose NOT to trim the rivets flush to the shell, as you say you are seeing on used Mk7. None of the Mk6, or any of the other helmets using this liner retention system, have flush-trimmed rivets off the shelf.

  5. #105

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    Perhaps the right word is “shorter” instead of “flush”? Flush would remove the flange which locks over the shell hole....and if it was very much shorter the flange would be too weak and could pull/pop out....I think there needs to a sticky-out-bit......it’s just a matter of how short it can be cut to ensure the line stayed in place. The bigger question is why did their commercial (and some “special”) helmets replace their rubber rivets with Velcro......

  6. #106

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    Quote by Composite View Post
    Perhaps the right word is “shorter” instead of “flush”? Flush would remove the flange which locks over the shell hole....and if it was very much shorter the flange would be too weak and could pull/pop out....I think there needs to a sticky-out-bit......it’s just a matter of how short it can be cut to ensure the line stayed in place. The bigger question is why did their commercial (and some “special”) helmets replace their rubber rivets with Velcro......
    YES! Of course. I was quite forgetting the flanged section which is what actually holds the liner securely. As we know, Professor, one actually has to cut the rivet flush (this removing the flange) to withdraw it and inspect whatever may be beneath the liner.

    As regards the velcro issue, I dunno boss, but given that most commercial NP products - all those in the AC range anyway - have few components in common with the 6/7 and CT and so on they're clearly the result of a different design philosophy altogether. If only someone actually knew something about all this...

  7. #107

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    Quote by Composite View Post
    Perhaps the right word is “shorter” instead of “flush”? Flush would remove the flange which locks over the shell hole....and if it was very much shorter the flange would be too weak and could pull/pop out....I think there needs to a sticky-out-bit......it’s just a matter of how short it can be cut to ensure the line stayed in place. The bigger question is why did their commercial (and some “special”) helmets replace their rubber rivets with Velcro......
    I think that is exactly the point that a certain mass is required in what is effectively a barb. The short answer is that these rubber retainers/rivet are cut after assembly and presumably with a cutter that automatically places the cut at the correct length.

    I know from my own experience when I managed to order replacements through the stores system (including the green plastic hole blanks, nuts and screws plus chinstraps and chin strap bales) that the rubber retainers are considerably longer before use to enable the assembler to grasp it and pull (ooer, sounds a bit rude!) to stretch and engage in an easy movement not requiring a tool.

    If I recall correctly as well as all the individual bits being in the catalogue there was also a re-furb / repair "kit" that contained all the small parts for one helmet. The liner was also available as just the inner "shell" and as "liner complete" which included all the small parts as well.

    I wish I had the foresight to have ordered more than I needed as they were accounted for as "expense" or expendable items but at the time there was no point and the whole helmet was not really a collectible either.

    Regards

    Mark
    Last edited by Watchdog; 05-03-2021 at 02:32 PM. Reason: Typo
    "War is an ugly thing, but not the ugliest of things. A man who has nothing for which he is willing to fight, nothing he cares more about than his own personal safety, is a miserable creature with no chance of being free unless made and kept so by the exertions of better men than himself."

  8. #108

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    Quote by Greg Pickersgill View Post
    YES! Of course. I was quite forgetting the flanged section which is what actually holds the liner securely. As we know, Professor, one actually has to cut the rivet flush (this removing the flange) to withdraw it and inspect whatever may be beneath the liner.

    As regards the velcro issue, I dunno boss, but given that most commercial NP products - all those in the AC range anyway - have few components in common with the 6/7 and CT and so on they're clearly the result of a different design philosophy altogether. If only someone actually knew something about all this...
    I did find when I tried it once (only once as it was rather fiddly and not too easy) that with persistence it is possible to use two suitably rigid implements ( I used tapered wooden dowels cut from a clothes peg) to push the rubber from two sides at once and gently coax it into the hole then push it the rest of the way with a drift of similar size to the hole. It was even harder getting them back in but string wrapped around the barb and washing up liquid did it. As I say, I didn't feel the urge to do it again but it is possible!

    I think the answer to the velcro thing is nothing more than simplification of manfacture (time and cost economy) by removing a mechanical process ie drilling and the tooling to do it. Velcro is vastly cheaper and it is a non-skilled process especially if the shell is pre-marked with where it is to go and the velcro is adhesive backed. Just a thought.

    Regards

    Mark

    PS As for slicing the rubber rivet off flush to the shell this is because of the aforementioned effect of wearing out the cover and "Toms" attempt to correct this. Sadly the average "Tom" is not known for his knowledge of physics or even mechanics and the "Flange principle" which makes this a kind of interferrence fit. So it would not occur to him that the annoying "sticky-out bit" was not due to the incompetance of the fools who designed the helmet but was actually required to hold the liner firmly in place. His logic would be reinforced by the fact that the liner does not immediately fall out. Also, it would seem less of an issue because the chipstrap is attached to the shell not the liner and when the helmet is on your head with the chinstrap fastened how on earth could the liner come out?

    "Tom" is an absolute marvel when it comes to improvisation and making something out of nothing but just don't let him "improve" anything already factory made. Trust me, I have seen the phenomenon at very close quarters
    Last edited by Watchdog; 05-03-2021 at 03:03 PM. Reason: ps
    "War is an ugly thing, but not the ugliest of things. A man who has nothing for which he is willing to fight, nothing he cares more about than his own personal safety, is a miserable creature with no chance of being free unless made and kept so by the exertions of better men than himself."

  9. #109

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    For those who have no idea of what this is all about, or have inadvertently lost their bookmark to that old abandoned website, here are some interesting pictures of 8415 99 130 6035 Liner Rivet Retention, the second picture being a comparison of a complete example against one removed from a helmet after fitting.

    British Mk7 helmet - everything you need to know

    British Mk7 helmet - everything you need to know


    The rivets are black flexible rubber (?), overall 1+3/4 inches or 45mm long, the head 3/4 inch or 20mm across, length from head to midpoint one-way collar is just over half an inch or 15mm. They appear to be excluvely an NP Aerospace spare part, used only for their helmets, as no trace of them as a commercial product available to the public has been found.

  10. #110

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    Quote by Greg Pickersgill View Post
    The rivets are black flexible rubber (?), overall 1+3/4 inches or 45mm long, the head 3/4 inch or 20mm across, length from head to midpoint one-way collar is just over half an inch or 15mm. They appear to be excluvely an NP Aerospace spare part, used only for their helmets, as no trace of them as a commercial product available to the public has been found.
    Thanks for the pics Greg, it can take an age to describe them and the listener would still not know what they look like!!

    I think they are the same as used in the Mk7 (?) which might explain why they don't seem to have appeared as surplus with the demise of the Mk 6 and Mk6a because they would surely have been produced in the tens of thousands.

    From handling these I suspect that they are made of a high carbon silicone compound as they are not "spongy" but do stretch and seem resistant to perishing. They look to be to me produced in a split injection mould and would come out of the mould on a sprue. Being such an uncomplicated (albeit multi faceted) shape a pattern maker of average skill could reproduce that in a comparitively short time so production cost would be low. I suppose it only takes the right demand to motivate an "aftermarket replacement". Anyone know a friendly rubber injection moulder who is into militaria?

    As for who made them, I imagine it was a sub-contractor and I would bet on a company such as Avon Rubber who made the S6 and S10 respirators amongst other defence equipments.

    Regards

    Mark
    Last edited by Watchdog; 05-03-2021 at 04:11 PM. Reason: Typo
    "War is an ugly thing, but not the ugliest of things. A man who has nothing for which he is willing to fight, nothing he cares more about than his own personal safety, is a miserable creature with no chance of being free unless made and kept so by the exertions of better men than himself."

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