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  1. #26

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    RE: letmo 0.06 diesel



    'As for the 0.6 tank itself, I never noticed any problems-but it remains a tight push fit, so potentially could loosen. Actually, with my new found tank making skills it would not be difficult to make a translucent replacement tank, which might be a lot more practical than the existing metal one...................'

    ChrisM
    'ffkiwi'


    Hi Chris, Irecently boughtan Emco 5 and would like to try making replacement tanks. What are you making them from?
    Has there has been a forum discussion on making replica tanks?


  2. #27

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    RE: letmo 0.06 diesel

    Winston-you won't regret buying the Emco-Rolls Royce quality........unfortunately the accessories you need to make it really useful are both scarce and have Rolls Royce prices as well...........

    I generally use Delrin (also known as Acetal) for making tanks and replica tanks-this is available in both sheet and rod (rod being the more useful for most of our work). It comes in two colours-white and black. The white is generally quite white-but I have a couple of pieces in my stock box that would be more correctly described as 'cream'. The black is obviously not relevant if we're talking about tanks where you want visibility of the fuel level-but useful for venturi inserts, bushings, bearings etc. The main thing about delrin is that is is an engineering plastic rather than a commercial one-it is dimensionally very stable, relatively inert, relatively resistant to chemicals and fairly strong. Its biggest advantage is it is absolutely glorious to machine. It can be turned milled drilled, tapped, knurled etc. On the debit side, it is difficult stuff to glue.
    Randomly grabbing 2 pieces of bar stock from my bin, both 1" diameter and weighing them, I get (you can see I've got far too much spare time on my hands!) for density 2.76g/cc for aluminium and 1.41 g/cc for Delrin-so you can see its virtually exactly half the weight of aluminium.

    In terms of uses-I've used it for: (i) rubber model propblock bushings, and bushings for folding prop pivots (ii) C/L bellcrank pivot bushings (iii) wheel bushings to suit K&S wire sizes (iv) IC engine prop bushings
    (v) sleeves and guides for DT line on FF models (vi) IC engine venturi inserts (vii) grips on rubber model rear pegs (knurled for finger gripping) (viii) finger nuts for securing removable model stays in my F1A model box-and tanks!
    Yet to be attempted-but on the list of jobs-custom low drag, low profile wheels with O-ring tyres.

    Tanks-well a lot of my engines are either missing their original integral tank, or the original has deteriorated by warping/cracking/crazing (sometimes all 3!) to the point where it is unusable-so either for aesthetic purposes or practical ones I've started making my own replacements. Now you have to decide whether you want a 'replica' tank or one that will simply do the job. [ie a simple parallel closed flat ended cylinder with a filler and fuel tube hole, retained by a central screw will work, but won't necessarily look much like the original. This only requires simple parallel turning and boring,plus 3 holes drilled] However I generally make mine to closely resemble the original in everything but colour-which requires shaping of the external and internal contours- quite a lot more challenge. I still haven't got fully on top of the internal contouring bit yet-mainly because I have zero experience in grinding custom tool shapes-and these are required-to get the inside end curvature right-you need a 'form' tool. I've managed reasonably well by using ball ended mills-but this becomes an expensive option when you only want to make one tank. [that being said-there are some quite useful Chinese made ones available on Ebay-I'm waiting on a 25mm one to arrive at present!] Equally-since you're not milling hard steel, but soft alloy or plastic, the ball end mill should last a lifetime!
    Other possibilities arise-the venerable ED Comp Special, Mills 1.3 and similar have tanks that are much too big for FF use-so you can make a custom tank from Delrin of smaller diameter and capacity that still fits the existing tank top (think of an upside down 'tophat' shape)-to give say a total 30 sec running capacity-which allows time for starting and adjusting-or whatever running time you need. Conversely you can increase the tank capacity from the original, for R/C use, by making a deeper/taller tank-and within limits the same can be done with the cylindrical backplate mount style of tank as well. The limit here may well be the length of 8BA,7BA or 6BA tank retaining screw you need-or can obtain. 8BA is virtually impossible to find in sizes longer than 1" threaded length. 7BA is damn near impossible to find in any length!

    Anyway attached are some of my efforts to date-including a repro DC Spitfire/Sabre tank made for Bill Hanshaw who is a member of this forum.

    ChrisM
    'ffkiwi'
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  3. #28

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    RE: letmo 0.06 diesel



    Many thanks Chris for the information on tanks. My Emco is a tidy 'made in Austria' that came with a lot of accessories and the milling attachment. But there is a lot to learn and I am only getting started. I have some Delrin that I haven't tried yet but expect it is not difficult to work. I realise thatbeing able to grind custom tool shapes would be very useful and plan find suitable steel for this. Once started down the engineering road who knows where it will end?

    Winston.

  4. #29

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    RE: letmo 0.06 diesel

    "Delrin....not difficult to work" is an understatement Winston-it is an absolute joy to work-the nicest material to machine that I've ever encountered-vastly superior to any metal as regards machinability.

    ChrisM
    'ffkiwi'

  5. #30

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    RE: letmo 0.06 diesel

    I cut this mount for my Letmo 2.5 cc from 6 mm 'T' section alloy. It weighs 25 g. (1 ounce).opWin('galleryItem.cfm',750,770,237736,'PhotoGalle ry');" style="font-size: 10pt">





  6. #31

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    RE: letmo 0.06 diesel


    I clamped the Letmo into my small 'Mecoa' mount to run it in. It had very little viabration.

    (I am trying to find a better way to upload photos.)


  7. #32

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    RE: letmo 0.06 diesel

    I used three threaded aluminum rods for electric motor mounts to mount the Letmo 2.5 cc diesel. It did vibrate with this mounting set up. A fellow machined a mount for the Letmo 2.5 cc from aluminimum and reduced the vibration a lot. But the mount is a bit heavy. Jack
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  8. #33

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    RE: letmo 0.06 diesel

    Jack-that's exactly the style I had in mind for the Letmo 2.5-though I plan to make mine from Delrin (at least initially) to save weight-if it holds up in use, well and good, if not I'll go to aluminium.

    ChrisM
    'ffkiwi'

  9. #34

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    RE: letmo 0.06 diesel

    Chris, Delrin should make a great motor mount with less weight than aluminum. The heavier aluminum mount would work well on a model with short nose moment and/or long tail moment. One problem I had with the Letmo 2.5 cc diesel was the front plate unscrewing while running. I cleaned the threads with a degreaser and used Loctite threadlocker blue 242. Problem solved. Jack

  10. #35

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    RE: letmo 0.06 diesel

    I will get around to doing the mount one day Jack-on my little Emco it will be a hard day's milling! Agree that you want a short nose model-I've always envisioned mine ending up in an original 60" Simplex, which should suit it-but I also have several ED Comp Specials and a couple of ED Mk2's which would also fill that role admirably-and beam mount not require any adapting of the plan. I too have had the front plate unscrew whilst bench running-which I put down to the fairly hefty vibration-as I haven't had the problem either with the smaller Letmo 0.6 or the even smaller Kalper .32-both of which utilise the samestyle of screw in front bearing housing.
    I too used thread locker, and made up a pin spanner to tighten things up.

    I don't intend to try it in the near or even medium term future-but trying to improve the balance on the Letmo shaft might yield some benefits. The only practical way I can see of doing this would be to insert tungsten slugs into the crankweb-(which is pretty thin anyway) opposite the crankpin-to increase the balance factor. Retaining these in location in such a thin crankweb might be an issue though. Lightening the piston might also help. I wouldn't want to try this sort of thing though without spare replacement parts at hand in case it all went pear shaped.........

    ChrisM
    'ffkiwi'


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