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Robert Cracknell

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Posts posted by Robert Cracknell

    First Aid at the flying patch?

    in All Things Model Flying

    Posted

    If I am injured and someone comes to help I sure as hell won't worry about risk, procedures and protocol!

    As someone who has been in that position twice in my life I can assure you that I was very grateful for the help I received and would think that anyone in the same position would be the same.

    Imagine a scenario where a club disregards first aid provision for the sake of responsibility, potential litigation or other red tape issues and an accident occurs what would the victim think when looking for help?

    First Aid at the flying patch?

    in All Things Model Flying

    Posted

    Putting any perceived legal obligation aside I would have thought it can only be a positive thing to have first aid cover at a flying site. As a sales rep with many years experience our standard issue car kit included first aid kit, space blanket and fire extinguisher. As lone travellers 95% of the time it could only be for the occasions when we came across a casualty. We had basic training to cover any eventuality we would likely encounter. I would have thought that anyone proposing that first aid provision be provided at a club site would be welcomed as it is only common sense after all.

    First taste of the sky

    in Beginners

    Posted

    My quiet disabled neighbour recently passed away and the young couple who moved in seem to think that letting their 2 screaming offspring play 6 feet from our lounge window (shared drive) is the thing to do, despite having a garden equipped with swings and trampoline!

    • Like 1

    Mystery four stroke engine

    in IC Engines

    Posted

    I sold a pair of Magnum 91's about 8 years ago. They were bought by a friend who was going to fit them in (I think) a Brian Taylor Mossie. He passed away before he completed it. IIRC they had quite good performance and were quite quiet.

    Battery Capacities?

    in Batteries and Chargers

    Posted

    Since my original post about cycling Rx packs I have bee experiencing some rather strange problems with my Overlander D100V2 charger.

    I was cyclng a 4 x AA Rx  square pack and the display showed ‘D’ for discharge and a start voltage of 4.14V. As the cycling went on I noticed that the pack voltage began to rise. From a start of 4.14V it slowly rose to 4.23V. As I had set the cell cut off at 4.0V (1.0v/Cell) I thought there is no way this is going to finish so I cut the process short. I recorded the latter part of the rise by videoing the display.

    A couple of days later I was cycling a 4 x AAA 800mah flat pack with a discharge of 1.0A and a charge of 0.5A and, foolishly, went into the house to make a cuppa leaving the pack discharging. When I came back about 10 minutes later I could smell something hot and within a few seconds one of the cells on the pack split open and was extremely hot. I am sure it was still on the discharge part of the cycle but even if it wasn’t 0.5A is below 1C and should not have caused the cell to rupture,

    I raised this with Overlander Support (the charger is just over 3 years old) about 2 weeks ago and apart from being told that they have reported this to the manufacturer I have no answers.

    Given the volatility if LI-Po cells I am not going to risk putting any of these near this charger!

    Has anyone had any similar experiences with a D100V2…?

    Battery Capacities?

    in Batteries and Chargers

    Posted · Edited by Robert Cracknell
    Spelling

    I have been cycling some of my Rx packs to check on their condition and capacity and I have come up with a few points which I feel could warrant input from the forumites.

     

    The packs in question are all 4.8v, 2600mah Rx square packs made up from welded Vapex AA Ni-mh cells. They range from less than a year old to some at 6 years old.

     

    The charger is an Overlander D100V2, and the settings for this exercise are;

     

    Discharge Rate 1.5A

    Charge Rate      1.5A (57% C)

    Cut off voltage   4.0v (1.0v per cell)

     

    The first point is that none of the cells took anywhere near the rated capacity of 2600mah, The best I could achieve before voltage cut off was reached was 1960mah. The others varied between this figure at best at 1550mah at worst. The discharge figures more or less mirrored these.

     

    Secondly, discharge times varied as well with the newer pack discharging the fastest. This was not measured but simply an observation from the side by side display on the D100V2

     

    This raises a question or two….

     

    The full capacity of the cell clearly cannot be extracted unless the 1.0v/cell limit is breached, i.e. the remaining capacity is only available by taking the cell to damagingly low levels. How do we assess the working capacity of these packs? Maybe we should be looking for ‘Real World’ ratings, perhaps expressed as a percentage of the claimed maximum.

     

    The voltage drop  was also noted and at a 1.5A load the voltage dropped quite quickly to around 4.3/4.5V. What is considered to be the minimum operating voltage? The voltage would hold at this for much of the discharge cycle.

     

    All input and comments appreciated….

    Servo tester

    in Gadgets and Electronics

    Posted · Edited by Robert Cracknell
    Addition

    I have a number of Ni-Mh cells that I would like to check out more thoroughly. Sure, they seem to charge OK but you are correct in that they might collapse under load.

    What is the consensus on what the load should be and the best way to apply it? Has anyone designed a simple circuit that will apply a constant load while the voltage is checked? What can be used as the load - bulb, resistor..?

    What is your favourite method?

    Smart phones; a discussion

    in Chit-chat

    Posted

    Geoff, I had that problem but I bought one of those gadgets that sends the Internet signal round the household ring main. You had a plug in device which could be moved from room to room or you purchased as many as you wanted. Even worked in the garage at the bottom of my drive!

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