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Ashnook

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Posts posted by Ashnook

    Electric Twin

    in General Electric Flight Chat

    Posted

    Many thanks for your inputs, the 4-Max sheets look interesting. I think I will go for a separate battery for the receiver/servo's rather than tie off the LiPo's. Interesting throttle connections Chris, I assume your transmitter can configure this arrangement!.

     

    Thanks for the help, Brian

    Peggy Sue 2

    in Peter Miller plan builders

    Posted

    Yes, my Ballerina is electric too, again, battery through a removable top hatch. The PS-2 will also be electric. Not got round to studying the plan yet.

    Would be interesting to see someone who has done an electric conversion. Currently building another Lyra, 1990's bi-plane plan. Had one for years and really liked it, cannot remember what hapend to it!

    Brian

    3s vs 4s Comments please

    in Power System Selection

    Posted

    Posted by Dave Hopkin on 31/12/2014 12:11:51:

    Ashnook, I agree you will lower the current on a higher voltage by adjusting the prop load to get the wattage you want, but dont assume that increasing voltage will reduce current (if nothing else changes) it wont, on the same prop current will increase

    Its a triangular balance, voltage/current./prop load - where we can influence only two factors, voltage and load

    Increase either of them and current and wattage will increase...

    Be wary of going too low on your ESC I think its better to have plenty of current headroom on an ESC rather than take it closer to its limits - I think they will probably last longer that way

    All points well taken Dave. In most cases (except the experiment with a friend on Monday I am designing the setup from scratch using the desired power as the starting point. I have read where one should allow an excess of 15-20% on the esc.

    3s vs 4s Comments please

    in Power System Selection

    Posted

    Yes Dave I agree with all you are saying. As well as taking the KV into account (I work on 800-1000kv for my type of aircraft) I use the watt-meter as my bible in terms of atcheiving the desired power-to-weight balance for my setup. I haven't just swapped a 3s for a 4s but rather decided I want, say, 500W for this model and used the watt-meter to get that with the right prop, the only thing I don't check, and perhaps I should, is the RPM of my setup. I do know that for my 500W the current flowing through the setup is lower than for the similar 3s setup and that makes me feel better and posibly be able to use a smaller ESC.

    All this discussion is useful to me as I still am learning about Electric power as I am like many 40 year IC guys trying to get to grips with this new capability.

    3s vs 4s Comments please

    in Power System Selection

    Posted

    Hi Dave, yes a friend flying on Monday on 3s tried a 4s pack in his high wing sport plane and was amazed at the extra power it gave him. He also said it flew much better with the added weight up front - another 4s convertee

    Yes Andy, a power meter was the first bit of 'kit' I bought and I do several prop combination tests before I decide what prop to go for.

    Monday was very cold but clear sunny skies here and we both agreed that messing around with IC on a day like that would not be so much fun. Plug-and-fly seemed a better plan. I still like IC for the better feeling of real power and the noise of a 4-stroke!

    Brian

    3s vs 4s Comments please

    in Power System Selection

    Posted

    I am about 50% IC and 50% Electric now and leaning more towards electric. I have converted some planes and kits to Electric with, I think, good success. I have decided to primarily use 4s batteries instead of what seems to be a general preference to 3s, here are my reasons, am I wrong or am I missing something?

    The mail reason is one of current, that is for the same power you need less current with 4S than with 3S. This effects both the speed controller and the motor in a positive way. Almost all motors and speed controllers are rated up to 4s and above.

    There is more battery power available for what seems like little extra weight. Also I have found in a couple of cases that the whole electric setup (battery, motor, leads, mount, esc) are generally lighter than the equivalent IC setup (motor, mount, tank, servo, receiver battery) and the extra 4s battery weight goes a long way to compensate for this, why add lead instead of extra battery power.

    So, am I OK in this way of thinking or am I missing something (important?)

    Cheers, Brian

    Eager Beaver

    in RCM&E Plan Builders

    Posted

    I agree, Tim's effort looks great, I wish I had thought of covering the fuse bits before gluing together! Too late now.

    Thanks for the battery info David. I have put two small dowels in the fuse (with thin lite-ply strengtherners) to use bands on the wing. I want to take it with me in the Motorhome so the wings need to be removable.

    Brian

    Eager Beaver

    in RCM&E Plan Builders

    Posted

    As with Jeffrey I have just got the mag and will start building this week. Where is the battery located? Also not too keen on gluing the wing to the fuse as I like to be able to get at stuff, alternative? Bands I suppose.

    Thanks

    Brian

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