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MrE

Member since Apr 2012 • Last active Jul 2015
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  • 388 comments

10 years coal mining, 25 years teaching, 10 years Head of Faculty, now retired...

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    This is purely speculation, based partly on troubleshooting badly abused cheap cameras in a school environment - TVEI Photography probably didn't make it to Berlin...

    With time and use, the seals will suffer permanent set, i.e. deformation that does not recover when pressure is removed, which will compromise it's ability to conform to the lip around the edge of the back.
    If the back is distorted by having a twist to it, modest hand pressure could hold the top edge in full contact with the seal and allow a gap to open at one side of the bottom edge. Similar pressure at the bottom edge would cause this gap to close but a similar sized gap to appear at the top edge but on the other side - imagine the back rocking on opposing diagonal corners. Potentially there might be a mid position where the back 'just' seals all round, and any light leakage will depend on how you are holding the camera and the temperature of the back and the body (curvature of ribbed plates being a function of thermal expansion - had any hot days this year?)

    Some play is to be expected in the hinge, but it might be worth opening the back and looking for signs of the free edge (side with the catch) being at an angle to the axis of the hinge pin.
    If you're going to run a test roll, try applying deliberate pressure to the back at top left, then top right, bottom left, and bottom right before taping one edge at a time - and keep notes on what you did, in what order, so the results can be interpreted correctly and you gain more information than 'it leaks' or 'it doesn't'.

    Equally, I could be talking a load of (overly verbose) rubbish...

  • in Miscellaneous & Meaningless
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    A leak that coincides with frame spacing suggests the issue is with the camera not the processing.
    Full width of the film suggests the leak is from the back, not from the front (not shutter, lens mount etc.)
    That it moves relative to the frame implies that it does not originate from a single source such as a hole or crack in the body or back.
    I would inspect the back, looking for distortion (twisting?) of the back itself or play in the hinge - something that might permit slight movement when the camera is handled. The impression of closing tight may be caused by the seal being highly compressed in one area but barely touching in another, giving intermittent sealing?
    Are there any common factors to the frames with leaks? Hot weather? One handed operation? Case on or case off? Tripod?

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    Boyle's Law?
    Some assumptions needed regarding air temperature in the tire - say 50C (273+50=323K) for example - and that the internal volume of the tire remains constant.

    likely pressure when hot = 140x323/293 = 154psi
    or
    starting pressure to give 140psi when hot = 140x293/323 = 127psi

    The flaw in the argument is an assumed temperature - the real answer would be to check the actual pressure this afternoon. An even bigger problem is I've just noticed the time - you're probably not going to see this until you get back, in which case you'll know the answer...

  • in Miscellaneous & Meaningless
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    I'm pretty sure the ratios are 4:3, 1:1, 3:4 giving uneven steps between gears (epicyclic gear box).
    It might be worth checking the maths - 46/19 should give 87 65 and 49GI which could be quite usable, depending on the full implications of "a girl who isn't a very good cyclist".
    I'm finding 91 69 and 51GI about right (55 yr old / 85 kg male on the Clee Hills) but given how cheap and easy it is to change the sprocket (search YouTube, disconnect cable, remove wheel, remove spring clip, take old sprocket off, place new sprocket on, replace spring clip, replace wheel, reconnect cable, adjust cable) I'd be tempted to leave the front end and tinker with sprocket sizes until your girl is comfortable and approves - there's little point in gearing you think is correct if it doesn't get used (voice of experience - Mrs. E and myself disagree significantly over ratios and correct use of gears)

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    https://www.lfgss.com/comments/12045470/­
    https://www.lfgss.com/comments/12046613/­
    And yes, Dammit had eyelets glued on. For a time.
    https://www.lfgss.com/conversations/2230­68/?offset=3225
    I think there was a solution involving other people and other adhesives?

  • in Miscellaneous & Meaningless
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    Lighter fuel? - may be a bit less 'assertive' than meths and perhaps less likely to take the paint off.

  • in Bikes & Bits
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    "Look more ratty" or actually be more ratty?
    The patina that comes with use takes time, wear, and probably an oily rag.
    sprayonrustpaint.co.uk/ if you're in a hurry...

  • in Bikes & Bits
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    Many years ago- in the last century even - I sent my technician to scrounge a couple of shopping baskets as part of an' A' level product design exam - every school offering the exam needed at least two, but couldn't tell anyone why. Needless to say it was difficult, and the main reason for the local shops not co-operating was the cost of a shopping basket. I gained two important bits of information: AQA Product Design was run by idiots, and shopping baskets cost over £25 each in the late 90s.

    tl;dr yes they're expensive.

  • in Miscellaneous & Meaningless
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    Moped / autocycle panniers are suitably cavernous and weight is not an issue: I carry a small bottle of sanitizing hand gel as part of the tool kit - used frequently for hand cleaning after roadside 'maintenance' and theoretically* might act as an alternative lubricant. Drum brakes front and rear means I shouldn't have to worry about lubricating the braking surfaces.

    *one of my many unproven theories - as yet untested given to the lack of punctures so far, and if I'm wrong my insurance includes recovering the bike to home...

  • in Miscellaneous & Meaningless
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    Read this yesterday with interest. My difficulties are with 2-19 moped tyres on 60 year old chromed steel rims - clearly different to TB14s, but much the same problem of a 'tight' tyre.
    Entertained myself for a few hours yesterday evening, comprehensively failing to fit a tyre, even after following all the advice I could find.
    Decided the biggest problem was getting the tyre to move in and out of the 'well' in the middle of the rim.
    Lubricated with diluted washing up liquid this morning - went on easily with a pair of plastic tyre levers...

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