Free flight electric

[boffin]

Yet more FF timers for electric flight………….

Nick Leichty : This is a PIC chip based US imported digital timer offering motor speed and run  time control for a brushed motor using a rotary pot and a screwdriver. The output stage features a MOSFET driver of 4 amps capability. The power unit shown in the graphic weighs in at 7.5 gms and is thus a possible for an indoor peanut  in the weight range 12-15gms. This PU  will appear next in an aatoolbox FF Smiley.

The specification of the test setup was……….

1. Didel 7mm orange brushed pager motor
2. GWS 2.0 x 1 propeller cut down from a 2.5 x 1
3. 90 mah Fullriver 1s LiPo
4. 1 way 2 pin SMD DIL switch Rapid 80-0319 on/off
5. Current draw 550ma, thrust 7.1gm, thrust/weight ratio 0.94

KPAERO : Designed by Steve Glass and marketed by Derek Knight, this timer is again PIC based and offers control of motor speed and motor run time duration. A third control offers motor speed decay control to ease the motor down on cutoff. The controls are again set via rotary pots, a method pioneered by the Atomic Workshops Zombie. The output of the device is a logic level signal for input to a brushed or brushless ESC and motor. The current capability of the KPAERO controller is limited ONLY by the selection of ESC and motor. The power unit in the graphic was the lightest  brushless power unit that I could afford and weighs in at 11.7gm. I have a feeling that the PU would be too quick for indoors so will probably see light of day in an outdoor  FF Gee Bee. There is no reason why you should not power much more powerful setups with this timer.

The specification of the test set up was…………..

1. Micron 2gm brushless outrunner
2. Micron Turnigy 3a ESC 1s LiPo
3. Indoor Flyer 2.5 x 2 black propeller
4. 200mah FullRiver 1s LiPo
5. KPAERO controller
6. SPDT slide switch Rapid 76-0114 on/off
7. Current draw 1.45a, thrust 16.8gm thrust/weight ratio 1.43

In operation, both timers ran faultlessly, were nicely linear in response and were a delight to operate. If you want an entry level no fuss timer, these will not disappoint. The only mild criticism was that neither timer offered an ‘on the board’ on/off switch, so the battery had to be disconnected and reconnected for a second flight. This would not be acceptable for my models and the test rigs were set up with switches from Rapid. These were chosen with care as it was easy to specify switches that were heavier then the timer board.

Regards Ian

[boffin]

Gentlemen,

The choice of timers for FF sport electric are now many and varied and more emerge from the woodwork on a regular basis. I have, therefore, tabled the timers that  I have used over the past 2 years and have compared their prime capabilities in the hope that this will avoid confusion and help the newbie to make a choice.

All timers listed have value and there are no 'clunkers'. Each timer has a range of applications dependent on the model you want to fly.

If you want a specific recommendation for a FF electric conversion, please PM me with the model specifics and I will try my best to get you in the air with the functionality you require. My model knowledge is not infinite so I will need as a minimum, the target AUW weight, the airframe weight (finished) , the wing span, and wing area. A graphic would be most useful. My preference is for LiPo  and brushless but I have a good database of thrust/current capability of 6/7mm pager motors.

If you want to power your model with KPXX gear and 50mah NiCad, ask someone else, I do not use this equipment.

Regards Ian

[boffin]

Another timer hits the market, primarily intended for indoor free flight for brushed motors of up to 2 amp current draw and single cell LiPo.  The timer is actually a controller as it both times the motor run and controls motor power. This a digital timer running a PIC chip with an IRML2502 MOSFET output stage.

The device  is unique in that it is programmed and controlled via a standard TV Infra Red (IR) remote. I will not bore you with the reprogramming details , access the link below if you are interested. The graphic shows the ‘irfftimer’ amongst some other rigs in the top right hand corner,  with a 7mm red pager and a GWS 2.5 x 1 running a 90mah Fullriver 1s LiPo.

http://www.bobsworkshop.co.uk/

The functionality offered is ………

1. Multiple power phases with each phase individually timed
2. The ability to kill the motor run if the model is in the rafters or wall
3. The option of calling up a repeat flight before the model has landed !

In conclusion, the controller behaved impeccably on test first time and was very easy to reprogram. It has unique functionality and I suspect it is going to be my favorite indoor controller.

The second graphic shows the model built for the irfftimer first airborne test.
Watch this space.

Regards Ian

[CHE]

Very clever !

[boffin]

CHE,

Glad you like it, Bob Blackburn has done a great job on this. A very innovative way of controlling a pager motor for indoor and perhaps light wind outdoor sport FF.....I am full of admiration for the cottage industry developer who is prepared to push the boundaries and offer the modeller new challenges.

Guys,

Taking this controller a stage further, this is the schedule I will run in my Smiley at the Oundle indoor on the 16th of this month:-

12345678(5)76(5)54(10)3210

This is my unofficial shorthand to programme the controller. The black numbers are key presses. The red numbers are are the time to hold the preceding key press down. In the absence of a red number, the controller will assume a time interval of 0.5s.
The motor ramps up from Power 1 to Power 8 in 3.5s, ramps down to power 6 for 5s, ramps down to power 4 for 10s and then ramps down to stop in 2s. This uses less than half of the available memory. A graphical representation of this schedule is shown in the graphic.

It seems technically possible that a twin IR controlled FF P38 or Lightning with independently controlled motors could run a figure of eight flightpath with a touch and go and subsequent climb out......its on the build list (about 7th).

Regards Ian
 

[boffin]

Gentlemen,

The IRfftimer now renamed as 'The Zapper' was run at the Whittlesey Indoor meet on the 23rd Jan with some success. Two models were used, Smiley and Juf both being free flight variations from the aatoolbox/prop planes site, run with 7mm pager motors and 120 mah single cell Lipo. The Zapper was taped underneath the fuselage so that flights could be terminated  if the ceiling was approaching.

Flights were easily programmed for climbout/cruise/descent with no problems. With some care on the timing, flights could be repeated before touch down. The only issue of note is that the model must be trimmed with  carefully for a tight initial climb such that the cruise power setting(s) do not put the model into the wall as the turn opens out.

In conclusion, an innovative highly functional controller which challenges the modeller to run other than a turning climbout and land.........my favorite indoor controller. I will be treating myself to a few more.

Some while ago I spent some time trying to achieve a 10 min indoor electric flight using a FET timer and a 90mah LiPo. The trick was to trim for about a 1m/min climb which was not easy . I failed miserably with a paltry 3m 32s as I had forgotten that the LiPo loses about 3% energy/min, so an initial slow climb turns into a gradual slow descent. What the Zapper could do would be to compensate for energy loss by moving to new power levels...........but alas only 64 secs of run time, unless one argued for a x 10 timebase multiplier.........achieved in software?

Regards Ian

[mike]

Ian,

Many thanks for the post.  Nice to see someone doing development.

I'm sure I have seen a reference to the covering/colouring technique on the models illustrated but I can't find it quickly.  How is it done?  Can you point us at a link?

Best regards

Mike F

Edited to remove a question that was answered on a closer reading of Ian's post.

[boffin]

Mike,

The following notes are a precis of the methods used to produce ink jet printed tissue applied to Depron using Johnsons Klear floor polish.

1. Create the graphics for the design using Corel or DrawPlus. You need a graphics package that does 'Bezier' a method for getting super smooth curves. I use MS Powerpoint as I know it inside out having flogged thru' many presentations in a previous life. It also has 'Wordart' and 2 colour merging to make things pretty.

2. Get some Modelspan type lightweight tissue, do not use Esaki as it has no wet strength. Lightly dust an ordinary A4 printer sheet with 3M spray mount. The one I use comes from Tesco at £5. Leave to dry for 60s to get most of the tack from the paper. Stick the tissue down to the paper and insert it into your printer. The latter is the most unnerving part of the process as one assumes that the printer will jam.....it does not. I use a cheap Epson DX4850 with 90 degree feed but am careful to use pukka Epson inks which are colour fast. If you use commercial cheapie cartridges, then the ink WILL run when you apply the Klear. Hit the print button to print the graphics, leave to dry for 10mins and remove the tissue.

3. Get hold of your Depron blank and lay the tissue over it. Brush thru with Johnsons Klear (Morrisons...a floor shine product) as you would for dope. The carrier is water , so you can do this in the house (Hurrah) as it does not smell. It does expand the tissue (Boo) and you have to ease the wrinkles out in the usual way. I have tried Pritt stick and 3M spraymount as alternatives to Klear but the Klear gives the best finish. Weight gain on a 3gm 11"span wing is 0.2-0.3gm.

4. Leave to dry, cut out the bits and assemble the model using UHU Por. The Smiley airframe can be completed in 3-4h for a cost of about £3 but you have to be accurate with the graphics layout and you cannot make things fit with the sanding block as the bits are pre-finished.

5. There is an option to the above to give the absolute minimum weight. This uses Durobatic foam (Micron) at about £4.50 a sqft treated with Inkaid (I have a supplier) and printed directly onto the foam using a printer with a straight thru feed path. I have not tried this as yet as the cheapest Epson straight thru is the wrong side of £250 and uses a 6 colour cartridge array...........I cannot justify this outlay for knock about fun models.

If you would like some sample graphic tissue files to experiment on, please PM me and I will send then on.............these are really simple techniques that many at the Pboro MFC have tried with success........makes finishing Depron very easy. The hard part is making a decent tissue file. BTW, I have tissue files  for Ki61 Tony and Me109 for indoor 7mm pager.

You will probably find a full treatise on tissue printing in the SFA forum, a search on Gordon Johnson will do the biz. But prepare for a long read.

Regards Ian

[JefO]

Hi Ian / Mike / anyone else interested

Tissue / Klear / Depron seems to be a possible method for home grown DLG tail-feathers for those without the tools/time/inclination to produce Kevlar / epoxy  / blue foam items.

Costing very little, being able to do it all in the kitchen without upsetting SWMBO, completing the whole job inside 4 hours, not requiring certain temperatures and easy enough for the average numpty to produce a reasonable job are just a few of the myriad benefits of the method.

The TKD fin pictured has more rigidity than an equivalent (size and weight) KEBF fin (6.7g). Colour is down to personal choice, rather than the standard boring 'sort of greeny yellowy beige' which seems so popular.

As you can see from the pic I am in touch with my feminine side 

Jef

[boffin]

Gentlemen,

Herewith an outdoor application for Bob Blackburns  Infra Red (IR) Zapper controller for brushless electric power trains…..see post 32. This is in Bernie Nichol’s Caudron entered in the electric/CO2 section of the 2009 Free Flight Scale Nationals representing the Peterborough MFC . The model won its class being the only electric model to complete a qualifying flight in the rain and gusty 10-14mph wind.

The specification was……………….

Waypoint E2205-36 brushless outrunner, 1770 rev/min/volt
350 mah 2s1p LiPo
12 amp Budget ESC
6” x 3” electric prop

The motor was selected primarily on weight to get the CG correct and was a budget 28gm/28mm device rated at a modest 9amps on 2s but was deliberately run way under rating with a 6” prop to minimise the torque reaction on the airframe to ease trim sensitivity. The Zapper + controller allows 128 0.5 sec steps with unique power and rudder settings at each step. The controller also offers a DT signal, which was not used on the Caudron.

The power scheme adopted for the Nats 3rd qualification flight was as the graphic, with separate settings for initial climb, final climb, cruise and landing. The 2 sec blip at the start of the motor run was an assurance that the run sequence had started. The subsequent 10s with motor stopped allows the flyer to place the model on the runway for ROG. On this occasion, an ROG was not attempted as the wind would have blown the model over before the motor would have powered up. The Caudron was hand launched at 10 sec with 62% of available power…….about 4 amps.

With practice, this controller can be reconfigured in less than 30 secs and offers high functionality. The ablility to speedily reconfigure and adapt for prevailing conditions was a good part of this models success in the less than perfect conditions.

After the motor has stopped, a casual retriever cannot restart the motor as it needs a coded 16 bit IR signal of the correct frequency from a TV remote control to return the software to the beginning and another different 16 bit IR coded signal to restart the sequence. …..a very good safety feature. There are no buttons to press inadvertently. Should the motor stall out on contact with terra firma the ESC shuts the motor down on current high and you need to kill the  power to the ESC and controller to get a re-start. We have not, as yet, had any surprises or nasty incidents with this device.


Regards Ian