Here is a list of all the postings PeterF has made in our forums. Click on a thread name to jump to the thread.
|Thread: Peterf's 1/4 scale Falcon Models Tiger Moth|
Out flying again today and I have settled on a pseudo tickover of 1950rpm set by trial and error. This is the first electric plane where I have the need to have a tickover set. The landings are much more predictable now and no more nosing over as there is always enough air flow over the elevator.
I wanted to build the Falcon Models kit but I had something else on the board so I kept putting off the purchase decision. Then when I came to buy it, Chris had stopped selling the kits so I bought an unstarted Duncan Hutson kit but did not have the time to start building it. Then Chris started selling his kit again, so as soon as he was back in business I snapped one up and sold the Duncan Hutson kit, luckily selling it for what I paid. However, I did buy wheels and tyres from the Hutson Kit as they are scale items, unlike the ones offered with the Falcon Models kit.
Anyway, in terms of the CoG, I am slightly forward of the required point because the location on the plan will be for an empty fuel tank so with the batteries in I can go forward slightly. When I set out converting it to electric I did a proper force balance around the CoG by calculating the torque of each component around the CoG using the weight and distance from the CoG. I summed the torque of the full fuel tank, throttle servo and Laser 150 compared to the electric motor, ESC and flight batteries, which then fixed the flight battery location, because I fixed this before I had completed the build to then arrive at the flight battery location by trial and error. And I can say it has worked out.
It may be that in fact I was bringing the model in at a higher throttle setting than I thought I had because of a nervousness to go too slow. Now I have done the stall test I have found quarter throttle needs up elevator, which means that the plane will sink of its own accord, I was probably not going this low to start with. I have now added a tickover switch at 1,500rpm using the idle down function so that I can not actually go too far and know I will always have some prop wash for the final flair out and landing. Being more confident about the low end performance will mean bringing it in with less throttle, which I believe will help the approach.
I also want to check the motor mount I constructed to see if I have got accidentally added some down thrust, but I am going to leave this one alone until I have built up some more time in the air..
Here are some still taken from a friend's video camera, I'll get the video added later. These are after the hinge lines had been sealed
The control throws are not on the plans, they are on the 4 pages of construction notes.
I have used the elevator and rudder throws as quoted. However, I have used the scale throws for the ailerons which I translated to 2 1/4" up and 1/2" down. Chris Stewart quotes the ailerons as being soft, however, in my test flying with my model, which has a lot more up aileron, I have found a positive aileron response which at full stick gave a good but not fast roll rate. Of course, mine also matches the full size in that as the stick goes to full travel, the down going aileron starts to return to the neutral position, so at 2 1/4" up aileron one side, I have very little down aileron on the other. There is lots of stuff on the design of my ailerons around pages 12, 13 and 14.
Edited By PeterF on 16/05/2018 13:50:03
Edited By PeterF on 16/05/2018 13:51:14
The RX is between the control box sides in the front seat foot well with both the antennae mounted in that location at 90 degree to each other. I use Hitec radio gear and although this is a 4 channel model, I have used the Optima 9 channel receiver that has two antennae for extra signal security.
The small box near the dummy exhaust is the telemetry sensor station, I have monitors on flight battery voltage, radio power voltage and current. See photo below.
I have not said much about the electrical side of my model other than the motive power side. On the Hitec receivers you can power the receiver separately to the servo power bus which with the advent of 2.4GHz and digital servos means that I always power the Rx function direct from the flight battery (it can handle about 35 Volts) and the servo bus from the BEC function in the ESC or from a separate BEC and you could never brown out with Hitec. You also get telemetry of the flight battery voltage without any other sensors. When 2.4GHz was new, this was quite an advantage, but it is now of course old hat. For larger models such as this, I install a back up battery supply, 4 cell Nimh, and have diodes between the back up battery, the BEC and the flight pack so I have dual power sources to both the RX function and the servo bus. I added the telemetry module so I can monitor both the flight pack voltage and the servo bus voltage. If I have a problem with the BEC, then the voltage drops from 6.0V to below 5.5V and I have a low voltage alarm. After 5 flights, I had used 200mAh from the 2500mAh back up battery. There are several threads on RC Groups about using diodes to create a back up system, I use 40Amp rated low voltage drop power diodes.
As the model is electric, there are no switches, everything is plugged in prior to flight. The right hand side cowl is fully removed and the cowl top is rotated open, still attached by the left hand side hine. I add the batteries and connect them onto the power harness, this power up the RX function but not the servo bus. I have an arming plug on the ESC supply and this is not in line at this point so no chance of the prop turning. I then connect the back up battery, which powers the servo bus, the ESC still being disconnected. I then put the top of the cowl down and replace the right hand side Cover and clip it down with the side catches. I check that the throttle is closed and the throttle hold is set. When I am ready, I then reach under the cowl with my arm outside the prop disc and fit the arming plug, only now does the ESC go through its arming sequence. There has been a discussion about arming plugs on this forum recently, very good and it made me decide to add one. This is especially because once the batteries are in and connected, there is a lot of work to do to close the cowl, all within the prop arc, hence leave arming the ESC till last. I had though about doing some work on the cowl top so that this was held on differently so it could be removed by itself to make this easier, but the arming plug was the easier choice.
The cowl sides are indeed held closed by spring loaded catches. These are made from 2mm threaded end push rods with a small washer and nyloc nut to hold the spring in place. I made the P shape ends on the catches and silver soldered them closed, just in case. I filed the grooves into the cowl to make sure that they latch closed securely and in fact I have to have a small tool I made up, piece of dowel with a hooked piece of piano wire in to open and close these catches. Old photo before I electrified all my models.
to be continued (due to post limits being exceeded).
I have put sealing strips into the elevator and aileron hinge gaps, I had some of the Solartex rib tape material left over, just the right size and set up nice and slack has not impinged on the control surface movement. The plane needed a bit more trimming afterwards, but it is hard to notice that it made much difference to the handling, as noted on the initial flights, the controls were powerful beforehand. However, the largest difference is the visual aspect, no more large gaps visible in flight. We tried to take some more photos today, much better light and blue sky but my camera just will not hack it, have added a couple anyway, on this flight, the rear cockpit doors were left open inadvertently and they did not flap around.
I explored the flight envelope:-
Edited By PeterF on 15/05/2018 21:03:57
Thanks for the comments and suggestions.
The model may have a larger than scale hingeline gap on both the ailerons and the elevator and it is only seeing the in air photos from directly below that this is appreciated, I have to agree that they are very noticeable and now I have looked at some full scale photos I see that they are not visible. I will look into adding some sealing strips as I have found some full scale photos showing the seals.
At the moment I will keep the springs as supplied, the landing that was filmed was not the best one, the next flight was an absolute greaser as I learned more about landing it. The filmed landing was a bit heavy and ended in a nose over, suitably edited out. The Tiger Moth did have quite softly sprung undercarriage from what I have read.
Regarding the engine sound, after converting completely to electric powered flight, this is only the second plane where I have noticed the lack of sound as being an issue, I have a Flair Taube which used to put put around on a 4 stroke at 1/4 to 1/3 throttle and after swapping to a motor has lost something in translation. I may look into a sound module. Certainly, when flown at scale speed with a good 4 stroke at low throttle certainly adds something evocative.
I flew the plane for the first time today, the wind was a bit more than ideal to start with but not too high and calmed down later in the day. The plane flies very well indeed and I am very pleased with it. I found that the controls were very powerful, I had not put any exponential on for the maiden flight but I certainly needed some just to calm things down. The scale aileron mechanism has also resulted in quite a good response to aileron. It can fly nice and slowly and looks just the part in the air. I flew circuits and figures of eight for today's flights only getting the model trimmed and learning how it flew, nothing adventurous. It needed a little bit of down trim on the elevator as it just wanted to climb and a bit of aileron and rudder trim but not much at all. When I throttle back it seems to want to keep flying level, I have found that I really need to fly it down to the landing, which is odd for me, this is the first plane where I have had to consciously do this, it may be that I am still wary of throttling back too much and I need to explore the flight envelope at low throttle a little more. I have had flights of around 8 minutes and this has used around 3,000mAh of the 7,400mAh I have on board so I have plenty of energy reserve. There is no shortage of power for take off and I have a feeling that with 1,500W (2 hp) on tap that I will be able to indulge in mild aerobatics. The other thing I am thinking about would be too save a bit of weight and swap to a single 6S 5,000mAh battery as that would have enough duration and also move the CoG back a little to the correct position. However, in flight the slightly forward CoG has not had any negative effect so far. See below for some flying pictures and video. The video can also be found at Youtube directly at this **LINK**
Edited By PeterF on 12/05/2018 22:22:33
|Thread: Forum members' new models: Let's see them.|
Lovely plane and congrats on the successful maiden flights. As John said, lovely colour scheme.
For those of you who have not followed my Tiger Moth Build log, here it is after 3½ years since I first started and closer to 4 years since I bought the kit. It is the Falcon Models kit, which is now no longer available. The kit is one of the closest to scale kits for the Moth and a lot of the functional details mimic the full scale quite closely, for example, the wing attachment method and absolute requirement for flying wires. I have added a lot of scale detail onto the some bought as parts, some hand built. During the build, I swapped over to all electric powered flight, so this started out as Laser 150 powered and is now powered by an electric motor drawing some 1500W. More info can be found on the thread Peterf's 1/4 scale Falcon Models Tiger Moth.
|Thread: Peterf's 1/4 scale Falcon Models Tiger Moth|
The wind has been unkind this week so I have not been out with the Moth. However, I put it together in the garden for a final check a few days ago, the last thing to do was to check that after the covering and rebuild, the ailerons were still set correctly and the control wires on the servo actuation arm and return arm all worked OK. I needed to rejig the wires a little and the rods between the servo discs and the ailerons, obviously, things had moved slightly during dismantling and rebuild. Here is the model after all the scale detailing has been completed.
The pitot tubes are from 1/8 inch, the larger diameter end of the lower tube is 5/32 inch, which slides over the 1/8 tube ( K&S). The vertical impulse tubes are from 3/32 inch. The brass hexagon used for the compression fittings is 5/32 inch. All sizes worked out by measuring a photo.
I had a couple of joints part company but not too bad. Ideally you could buy a series of slightly different solders and use increasingly lower melting points as the build progresses.
The pitot tubes are made from brass tube plus 0.3mm and 0.15mm brass sheet along with some 3/16" brass hexagon all soldered together. As I looked into making the pitot tubes, it dawned on me that there is no such thing as a standard pitot tube layout and many moths have had slight changes made over the years. Therefore, I looked closely at the full scale I am modelling and it followed the most common pattern, however, it has 90 degree compression fitting type unions connecting the pitot tubes to the impulse lines which is unusual. I do not have a drawing of the pitot tubes, hence I used a photograph of the full size plane and printed this out suitable scaled to give a template to make the pitot tubes against. This allowed the tubes to be bent correctly and the side plates to be cut out.
I made the compression fittings from the hex bras with grooves cut in using the parting tool to simulate full size ones. They look OK, although one might complain that it is unusual that the flats on all of the nuts line up with each other, which would not happen in reality. Everything is soldered together, which has meant some judicious use of the iron to stop everything falling apart if I allowed the whole assembly to heat up too much. The pitot tubes were bent to shape, end pieces made and soldered on then the 0.15mm sheet was used to attach the two tubes together as one assembly per scale. The sides were then attached with 10BA nuts and bolts and soldered where they wrap around the pitot tubes. This impulse lines were added along with the compression fittings and bent to shape. The assembly was painted and attached to the interplane strut and the usual 0.5mm aluminium and rubber straps added. The brass tubes stop short of the wing surface, I did not want to puncture the Solartex.
Another update split over 2 posts due to limitations on the size / content of a post.
I have added three additional scale details, the exhaust, a small wind driven generator and the pitot tubes.
The exhaust is simply a piece of ABS tube with the end curved with a hot air gun, to stop the bend collapsing, I put a piece of silicone tube inside the ABS tube. I glued a length of hardwood dowel, split length ways into the tube so that I could screw this to one of the plywood frames in the engine bay to simulate the exhaust, it looks OK, but is not true scale in that it does not have the pipes in from each cylinder and is uniform along its length.
The full size plane I am modelling has had an air driven generator added at some point. This sits between the undercarriage legs. I have made up a reasonable facsimile of this using the rotor out of a 30mm EDF, it is not truly scale but represents what is on the full size plane. The rest of the generator is made up from 0.3mm brass sheet soldered together. Yes, the EDF rotor does rotate, the shaft sits in a length of brass tube.
Pitot tubes in the next post.
I have also reset the rigging wires so that I can assemble the wings properly onto the fuselage, after the rebuild everything was in slightly different positions and the wings would not fit back properly. I have checked the GoG and with the batteries in it is marginally nose heavy, about 15mm in front of the plan Cog. However, the plan CoG is for IC engine in the dry condition, when the fuel tank is full the CoG will be forward of the marked location, so I believe I am OK. I have weighed the plane and this comes in at 8.2kg = 18lb 1oz with batteries, which I am happy with given the amount of detailing that has gone on.
I have a couple of final jobs to do on the power side, I need to add an ESC arming plug because it is quite convoluted fitting the batteries and getting the cowl back on, hence a final arming plug next to the exhaust will safely make the plane live after all the fiddling about is done.
Therefore, as far as I am concerned, I have completed the build of the plane, I have no more detail to add and I should be able to Maiden it during May.
The aerial tube is 8.85mm OD and the plastic tube is 8.05mm OD. I was originally going to use 8.0mm OD aerial tube but when I found the plastic tube in the scraps box it was too good to be true, so I went up on the metal tube one size. If I had stayed with the smaller metal tube I would have had to make the sight glass from rolled sheet.
I have completed all the scale fittings on the fuel tank. These are representative details, they may not be mm perfect. There is the level gauge, vent, link pipe under the front cabane bar, the drain valve, main fuel valve complete with actuation rods and the pipe to the engine. The compression fittings were turned from hex brass, the valves from aluminium and the actuation rods were piano wire with clevises turned / milled from aluminium. The level gauge is made from the scrap box contents, the metal tube is a section on an old 35MHz transmitter aerial, the sight glass is from a tube that some brass came in. I milled the obround slot in the thin wall tube whilst I had a piece of dowel inside the tube so that it did not collapse or tear.
The plane I am modelling still has the slots and slot control cable installed, hence I wanted to replicate the cabling around the cabane. There were a few straps to attach wire guides, made up as the other straps. At the top of the cabane strut there is a pulley assembly where the cable direction changes through 90 degree. The pulleys were made from bar turned on the lathe and the mounting bracket dimensions worked out from photographs and cut from 0.5mm aluminium plate, it is reasonably authentic. I have attached my patterns if someone else wants to use them. The turnbuckle is from Mick Reeves Models, it is probably slightly over scale in length. The one thing I have added is a small bracket to hole the left hand wire in place when the wing is not there, otherwise the wire and turnbuckle would flop about. I will add holes on the ends of the wings with mock leather covers. When the wings are attached, the ends of the cable will pass into the wings.
The clips between the double rudder wires were a piece of cake in comparison to the above 2 items, being simply 0.5mm aluminium sheet with the ends rolled over.
Edited By PeterF on 17/04/2018 22:31:29
The last few days have seen more scale detail added, namely the air speed indicator (ASI), the slot control cabling and the clips between the double rudder wires. This has been split over two posts because of forum limitations. Most of this has used the same 0.5mm aluminium sheet I have used for much of the other detail and some items turned on the lathe.
The ASI is based on some drawings Manish put on his build log for the DH60 model. The main difference I noted when I started was that the Tiger Moth I am building had less pronounced radii at the corners, so I took account of that. I printed the drawings off at reduced scale until I had them the right size. Glued them to the aluminium sheet with double sided tape and cut them out. I cut the slot in the angled plate by putting it in the milling attachment on the lathe and running a 1.5mm end mill along the plate, much better finish to the slot than doing it by hand. The speed scale was drawn up in PowerPoint and then printed out on inkjet vinyl, cut out and glued in place. The file is attached. The wire was from 0.9mm piano wire suitable bent around a former of the right diameter.
The straps to mount it to the interplane strut are cut from the aluminium sheet and backed with 0.4mm rubber per the full scale. A trick I developed to cut long strips of rubber accurately was to put a piece of masking tape on one side of the rubber, then hold it down with a steel ruler and cut strips off with a sharp scalpel. No worries about floppy rubber stretching and cutting with a jagged edge. The rubber was glued to the aluminium with UHU Por before bending to shape. These are clamped onto the struts with 10BA bolts, entirely functional.
It was when I came to attach the straps to the ASI that I realised I had missed the other key differnece between DH60 and DH82, namely thee struts are not vertical, so the lower mounting hole was in the wrong place. To late to change so I drilled another hole and filled the wrong one a bit, I was not going to make a whole new ASI. Some of the full scale ASI was attached together with rivets, so I made up some 1.2mm dia aluminium flat head rivets from 3mm rod in the lathe. Another difference is the Moth I am building only has one bolt in the plate that is attached to the spring, the drawing has two.
Here is the drawing I used for the luggage catches, the dimension stated as 5mm, I actually made them closer to 6mm.
Manish, my luggage door does not open, but the catches could me made functional if made from steel or tinplate, the aluminium is too weak.
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