G-JIMG Posted March 30, 2020 Author Share Posted March 30, 2020 As I said at the start, this is my first excursion into an all electric model so I've produced a wiring diagram for it. Hopefully it will prevent me making wiring errors as the build progresses! Quote Link to comment Share on other sites More sharing options...
fly boy3 Posted March 30, 2020 Share Posted March 30, 2020 Yes please carry on this interesting build. I too am an ic fanatic, but interested in your power conversion when available. Cheers Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 30, 2020 Share Posted March 30, 2020 Jim That wiring diagram looks sound enough to me. The only query is the UBEC providing power to the lighting when it appear the power is also connected via the red wire from channel 7. Is there a reason for using a battery for each motor? There is an argument that a reducing power on one motor in a twin can be more serious than both failing. I have a twin set up like this for structural reasons. I specifically keep the flight time shorter than necessary to avoid the risk of taking a battery down too low and not being able to spot it in time. In hind sight I would have added a battery cross connection. Quote Link to comment Share on other sites More sharing options...
Martian Posted March 30, 2020 Share Posted March 30, 2020 Simon it looks to me as though that ubec powers the rx and the lighting is teed Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted March 30, 2020 Author Share Posted March 30, 2020 Martian, you are correct, that UBEC powers the Rx and the lighting. Simon, the Motor/ESC/Batt configuration was arrived at by George of 4-Max. I sent him the approximate weight and wing area of the model, along with one of the 4 blade props, and he tested various combinations to get the right set up. The hardware consists of: Motors: PO-3547-800 ESCs: PP-TESC45AU Batts: PPL-40C4S-3700 Jim. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 30, 2020 Share Posted March 30, 2020 Jim Ooops! Should have spotted that UBEC is powering the rx, servos as well as the lights. I was not querying the power itself but only if for any reason one battery runs down before the other you will have asymmetric thrust. Not a problem as long as you spot it is happening. Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted March 31, 2020 Author Share Posted March 31, 2020 It's occurred to me that not everyone will know what a heavily modified King Air 350 looks like, so here's a few pictures of a professionally made model. Jim Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted March 31, 2020 Author Share Posted March 31, 2020 Being a scratch build, one potential problem is the manufacture of the fibre glass parts such as the Engine Cowlings. Fortunately I have access to a 3D Printer so I was able to print out the relevant part in two halves. The print included the exhaust stub but I will have to remove that in order to make the cowling mould. Jim. Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted March 31, 2020 Author Share Posted March 31, 2020 Printed the other half of the cowling using a different plastic but the end result was still pretty rough (it's only a hobby level printer). The finish was certainly not good enough to make a mould with so I spent a lot of time today filling and sanding. Jim. Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted March 31, 2020 Share Posted March 31, 2020 Hi, Nice long nacelles so should not have too much of an issue getting the C of G although I would construct the nacelles/fuselage with the option of moving the batteries around when the time comes to check + they are close to the fuselage which has its benefits. A couple of electric and IC Mosquitos have everything as far forward and some lead to achieve C of G where as my Dual Ace needed nothing. I have another twin tricycled which was sitting with 700g nose wheel weight and I am currently engineering as much back to the tail as possible. My point is that the model may not reflect the full size with respect to weight distribution. Regarding your RDS, are you providing access panels to adjust the aileron RDS grub screws, only asking as sometimes its easier (if you have the option) of putting the ailerons on different channels and thus you can adjust their centre points separately? Are the flaps fuselage to nacelle or extend to the outer side of the nacelle - just interested Quote Link to comment Share on other sites More sharing options...
Martian Posted March 31, 2020 Share Posted March 31, 2020 I am certain that you will do it justice Jim Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted March 31, 2020 Author Share Posted March 31, 2020 Hi Chris, The main undercarriage rotates forward, so there's not enough room in the nacelle for a battery. Fortunately the aircraft has an under-fuselage pod that is large enough to house both batteries. At some point I will have to figure out how to make it easily removeable whilst still secure in flight. Regarding the RDS, there will be underwing access panels for both servos. Unfortunately I only have 7 channels available, so putting the ailerons on different channels is not an option. There are two flaps each side. One extends from the fuselage to just outboard of the nacelle and the other extends from there until the aileron. The real aircraft has Fowler Flaps but that's a step too far for me at this stage. Designing and building them into a new wing is a project for another day. Jim. Quote Link to comment Share on other sites More sharing options...
David Hall 9 Posted March 31, 2020 Share Posted March 31, 2020 I noticed that your UBECs are wired in parallel (even more if the ESCs are supplying power too). This is something that I plan to use when I next need to supply more power than one BEC can provide. Not all BECs will do this happily, I understand. Have you tried this on the bench? Edited By David Hall 9 on 31/03/2020 16:55:40 Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted March 31, 2020 Share Posted March 31, 2020 David, Where does it show the BEC's in parallel? The upper BEC powers the U/C only, notice the red wire cut to the RX. This is standard practice when using U/C as if it jams then the BEC will burn the U/C motor out or its inbuilt safety will function but it will not brown the RX out. I don't think its ever good practice to parallel BEC's, if the ESC BEC is not large enough then put a separate UBEC/BEC in that can handle the expected load. I had an interesting chat with George at 4Max regarding my Laser 180 YAK and his advice was keep it simple and have one 20A UBEC (It does not have U/C) but in the event of a servo failure the UBEC voltage will not drop below the RX min voltage as it clears the fault. Edited By Chris Walby on 31/03/2020 17:07:42 Edited By Chris Walby on 31/03/2020 17:08:16 Edited By Chris Walby on 31/03/2020 17:13:24 Quote Link to comment Share on other sites More sharing options...
David Hall 9 Posted March 31, 2020 Share Posted March 31, 2020 I see your disconnect now... in the red lead. Edited By David Hall 9 on 31/03/2020 17:49:18 Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted April 1, 2020 Author Share Posted April 1, 2020 I retrieved my Son's Lego from the attic and made up a box large enough to take the cowling. I lined it with cling film (to stop leaks) and made a silicon mould of the cowl. After thoroughly mixing the silicon I liberally coated the cowling with the mixture to minimise air bubbles against the surface. I then suspended it within the Lego box and slowly poured in the remaining silicon mixture from a height (the idea is to get as thin a stream as possible to reduce the amount of air in the mould). The mould was left to cure overnight before the plastic cowling was removed. Jim. Quote Link to comment Share on other sites More sharing options...
Chris Freeman 3 Posted April 1, 2020 Share Posted April 1, 2020 Very nice project and you have some great equipment to help with the build. I am following the progress with interest. Quote Link to comment Share on other sites More sharing options...
Nigel R Posted April 1, 2020 Share Posted April 1, 2020 "Not all BECs will do this happily, I understand." I'd be surprised if you can find a single hobby BEC that will be happy when paralleled up. Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted April 2, 2020 Share Posted April 2, 2020 Jim, messaged you a couple of days ago, hope you are well. Chris Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted April 2, 2020 Author Share Posted April 2, 2020 To make the first engine cowl I left the mould in the Lego box, so it wouldn't deform, and started by coating the inside of the mould with a Finishing Gel Coat. Once the gel coat had gone tacky I applied resin and started laying in strips of fibre glass. (Sorry, forgot to take pictures). The cowl was allowed to cure overnight before removing it from the mould. The upper edge was trimmed using the drill press and the spinner ring trimmed using a Dremmel. Jim. Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted April 3, 2020 Author Share Posted April 3, 2020 No progress today, swmbo decided there were gardening jobs to do . However, I have had an opportunity to think about Elevator control. Being a T-Tail there is a potential issue with Elevator operation but fortunately the aircraft in question has a Radome mounted on the tail. This means I can conveniently hide the linkage within the hollowed out structure. Jim. Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted April 4, 2020 Author Share Posted April 4, 2020 Managed to do some work on the wing today. The model will have lights fitted, including wing tip Nav lights, so I needed to make the covers. I shaped the wing tip and then carefully cut out the relevant section. This was then stuck on a piece of dowel and fibre glassed to strengthen and harden it. To make the cover I made a wooden frame and attached a piece of acetate sheet. I used a heat gun to warm the acetate to the point it became flexible and then pressed the mould into it. While pressing the mould in with one hand I used the other (gloved) hand to press the acetate against the sides to maintain the correct shape. Jim. Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted April 5, 2020 Author Share Posted April 5, 2020 I can't speak for anyone else but personally, once the model is built and flyable, I tend to stop working on it and move on to other projects. As a result the model rarely gets the scale finish I originally planned. To prevent this from happening this time around I decided to make the fiddly bits now. As you can see from the pictures earlier in this thread, the aircraft has a host of antenna. Fortunately the antenna manufacturer's web sites provide dimensioned drawings of their products. All I had to do was divide by 10 and copy the shape . I also made the two pitot probes from some brass tubing and rod. The chrome spray finish is not perfect but looks better in the flesh than it does in the picture. All I have to do now is put these somewhere safe and remember where they are when it comes time to fit them . Jim. Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted April 5, 2020 Author Share Posted April 5, 2020 The King Air has quite distinctive propellers, so I decided to do those now as well. First I trimmed the 11" APC props down to the scale 10.5" by removing 0.25" from each tip., shaping it to match the King Air tip at the same time. I then balanced the props in the normal way. I then spray painted the props using rattle cans and placing masking tape in the relevant areas. The real props are made by Hartzell and each blade carries their logo. I managed to scale the logo down and printed it out on some transfer paper. After spraying the prints with some clear varnish they were transferred to the prop. You obviously can't read them at that scale but I'm pleased with the overall effect. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted April 5, 2020 Share Posted April 5, 2020 Every single build Jim, I would put something away safe and mislay them but now I use those 4 for a £1 boxes with lids And a label. The chrome spray looks chrome by the way. You are spot on with finishing the job as you do end up flying an unfinished model in the future. We all don't like knocking bits off in the long grass though. Those props look real Edited By Denis Watkins on 05/04/2020 15:31:49 Quote Link to comment Share on other sites More sharing options...
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