Hi all:
Well, my electric twin project is back on the front burner. I put this project aside for a while until I could get assurance that a proper timer that would both control both motors and retract the landing gear in proper sequence was available. Now it is! Will Hubin has developed the timer that I need for this project and so it’s full speed ahead on it.

The first two photos show the beginnings of the cooling tunnel in the molded fuselage top shell. The only cooling air that this tunnel has to handle is from the battery. The new Hyperion batteries that we are using just don’t get hot. They come down barely warm in even the hottest weather conditions, and that’s in situations where they are mounted aft of the motor. In this configuration they should come down almost cool to the touch! This tunnel will be sealed with a thin coat of finishing resin and then two strips of balsa will be added to fill in the around the bottom of the area where the splitter is installed. There will be two outlet holes; one on either side of the fuselage and they will be louvered. They will be styled to fit up against the back of the painted on canopy that will be added during the finishing process.

The second photo shows the molded top shell taped in position to illustrate the cooling tunnel as it will look when finished. The fourth photo just shows the overall project – sans flaps and elevators – at the point where it stands now. I’m hoping to get the top shell installed permanently by Sunday (12-19-10) and start working on fitting the bottom front molded shell and cut the retract openings. Then comes the removable top front molded shell that covers the battery and the electronics. The nose cone will be carved and hollowed and it will have an air inlet hole in it. Being in clean, undisturbed air, it should bring in plenty of cooling air.

The last thing that will be built and installed will be the nacelles. I’ll make profile “dummy” nacelles and mount the motors, props and spinners to them. I’ll make them longer than necessary and keep cutting them back and checking the balance point until I have a just slightly nose heavy condition. When I'm satisfied with the CG, I'll make built-up nacelles that have the main gear retract mounts and front-mount motor mounts. More finish will be applied aft of the desired CG point, so that will, hopefully, bring the CG to the exact right point without the need to add nose or tail weight during the trimming process.

Hopefully I’ll be able to complete all the woodwork and get into finish by the end of January.

Later – Bob Hunt  

Looks great Bob!!!! 

Hi Bob
Can you talk a little about the retracts?  Are they off the shelf R/C retracts, are they electric or air driven retracts?  As I get more into electric planes it seems that retracts are a natural addition and I would like to leverage off your work.  I am also interested in how the Hubin timer will work in this plan.
Andy Borgogna

Hi Bob
Can you talk a little about the retracts?  Are they off the shelf R/C retracts, are they electric or air driven retracts?  As I get more into electric planes it seems that retracts are a natural addition and I would like to leverage off your work.  I am also interested in how the Hubin timer will work in this plan.
Andy Borgogna

Check the other build threads - I suspect an alterior motive. Using Retracts would let Andy avoid carving those monster signature wheelpants for his outstanding new CONTINENTAL!   

Glad to see the project bubbled up to the top of your work pile.  Looking good

Thanks Bob for the information on the retracts.  Dennis you are right I would have put this setup in the Continental if I had known about it, but it's too late for the Continental. BUT the next project in the schedule is a Walter Umland Spitfire that I have had for a couple of years.  It will get retracts and I will use Bob's technology for the installation.  I have already contacted Will about the FM-9 timer and will order a couple of them both with the retract option.  This is really exciting, a Spitfire with retracts Oh Boy! 
Andy

 Great pics and info Bob, glad to see you back on this one.

 I'm trying to get a visual on some of the outlines and small details. Do I notice a slightly defined "step" in the top toward the nose where the leading edge of the windshield meets the nose? I really like the subtle ventral fin too, small details like that can really add to "The Look".

 Just a "two cents" idea here. When you do the nacelles I imagine you'll need to have cooling exit holes somewhere. Maybe design and place them to look like the big turbine exhausts on a turboprop plane? That would add realism and also add to the cool factor, no pun intended.

Glad to see this project back on the front burner. I've been running Hyperion batteries all this last year. They have been great batteries!

Rob

Bob,
This note triggered a thought.  On your suggestion, I tried a Hyperion battery.  Same specs as the TP battery I have been using. It worked the same, although it may have run cooler than the TP battery. The only difference is that it weighed about 2 ounces MORE than the TP battery. That's 2 ounces that I don't want to give up.  I already have that 2 ounces scheduled for something else in my new plane.  I'll post pics when far enough along.

Paul Walker

C'mon Howard ... it must be invisible feet!

Needless to say, this project has been dynamite looking since the first sketch
Regards,
Dean P.

Hi Bob,

Magnificient looking twin, great job as always. I thought I would chime in since I just received a new custom timer Will designed for me to allow for the E-Flite .10 to .15 electric retracts. I had been trying to get these retracts to work with my Z-Tron Z.4 timer, but ultimately found out this timer will not work with these specific retracts even though there is a retract channel built into this timer. After speaking with Mike Palko and Sergio, it was determined the cause was probably an insufficient sized BEC. These retracts operate in the 4.7 to 7.4 volt range and draw 5 milliamps at idle and 150 milliamps in operation. There is only one BEC that will work with the Z-Tron Z.4 timer and it is only sized to power the actual timer and one retract servo. These retracts do not use a servo, the motor is housed in the retract assembly and the only BEC available for the Z.4 is not large enough to power these retracts.

I ordered a 10 amp Castle BEC to pair with the new Hubin timer and anxiously waited for it's arrival. Here is the test report I sent to Will earlier today with the results. Hopefully this may save someone a bit of time sorting this whole electric retract thing out. I know Will sells a timer with an included BEC built in, but I did not test that one, I tested one which requires an internal BEC. Not sure if the timer with the built in BEC will work with these retracts or not, perhaps Will might know.

"Hi Will,

It was kind of cold and a bit windy last Sunday, but Wayne, Sam and I went flying anyway and we got a chance to check out your new timer with the retracts. Everything performed flawlessly though I might certainly tell you a funny story about the first takeoff. We programmed the timer and ran it through a few dry runs on the ground without powering the motor and the retracts worked perfectly. OK, get the lines rolled out, plug in a new battery and give it a go.

We had programmed the RPM for the Plettenberg 25/12 at just over 9300RPM as a starting point. Wayne wanted to get a tach reading so we would have a reference for the timer though I protested a bit due to the 10 second retract sequence. Well, it did seem we could check it for a second or two and still have time, so I said OK, let's try it.

Wayne's grandson Sam was holding the plane while Wayne plugged in the arming switch and then activated the timer, tach in hand. The motor started and quickly came up to RPM for Wayne to get a tach reading whereupon I immediately motioned Sam to let the plane go just as soon as Wayne had exited the immediate area. Sam let it go smoothly and it could not have rolled more than two feet on the ground when I noticed the gear starting to retract. Lucky for us, the small concrete pad we take off from only rolls about 10 feet before the slope takes a severe downturn. I was holding all the up elevator I could and luckily she went airborne without so much as even scratching the APC prop. Gear was completely retracted at about a foot of altitude.

You should certainly caution anyone purchasing this timer as is they cannot monkey around on takeoff. As soon as you feel the first pull of the prop spinning up, it is time to let this baby go. The longest distance we could get that day before the wheels retracted was just short of a full lap. While I think this is perfect and just what I would like for competition, it leaves no room for tach readings or any delay once the motor starts.

The three burp warning was excellent and it could not be missed. The 5 second delay after the burps was perfect for the gear retraction and using the Schulze ESC provided the immediate brake after motor shutdown. Couldn't really give much feedback on the slow start to RPM since we don't have a long paved takeoff area.

These are the E-Flite .10 - 15 size electric retracts and they worked perfectly with a 10 amp Castle BEC and your timer.

Plan on doing some more testing, but overall I am very satisfied with this timer. If I were to make a wish list of things I would like to see integrated in future models, here are a couple of items.

If it were possible to program both the retract delay time from start-up and the speed of the actual retraction itself, those would both be positive. I am not an engineer, but it seems these could likely be controlled through the timer. Another feature I think would be nice though certainly I don't know if it is possible is the brake feature. If this function could be set through the timer, might make life easier for Castle ESC's.

Going over to Waynes' tonight to set up another plane for electric conversion - we were thinking a Castle 75 AMP ESC and another Plettenberg 25/12 (since we already have those). Will look to find a way to use a brake with this controller, but I know you said this might not be a good match. I only have one Schulze 18.61 which is in the retract ship. I could borrow this Schulze 18.61 or get another one, but wanted to get your opinion on this. Please let me know if you know of anyone else successfully using a Plettenberg with a Castle ESC.

Thanks for the great job and the quick service, you made our weekend. It was so impressive seeing that gear come up and surprisingly, we were amazed at the difference it made in this particular aircrafts performance. It is a lead sled of the highest order, probably tipping the scales at close to 80 ounces, but many of the weight related issues with cornering and wobbling seemed to smooth right out. Man, it looked good in the air as well, when I cut those four foot bottoms on the inside squares it looked like I had a mile of clearance

Thanks again and Merry Christmas !

Jim Smith (Smith Brothers Stunt) "

I am happy to relate our experiences with retracts to any who are interested. These retracts allow you to remove the coiled wire gear to replace with standard wire (without the coils) which we will do on the new Tracers we are about to build. They are very robust and I think on initial inspection and trial they will more than meet our strength needs - uses with 1/8 or 3mm wire, haven't miked yet. We all flew it a few times and Sam even got to try a nice bounced landing for a good stress test (it was very windy and cold). No problems so far. Will probably take a few photos next weekend to post here if the weather cooperates since most of us have never seen a ukie stunter flying with retracts.

Merry Christmas to all

Not sure if the timer with the built in BEC will work with these retracts or not, perhaps Will might know.

[/quote]

I can tell you for a fact that it does NOT work with two or more retract units. It will drive ONE only .  That's how the FM-9R with external BEC came into existence.

I also have thought about removing the wire with the coil, but for now have decided to leave it with the coil to minimize the shock loads on the retract unit.  Time will tell on this subject.

Paul Walker

Jim,

Thanks for the informative, good news report on retracts and yet another great timer from Will. :-)

I would guess that your Battery Eliminator Circuit adds very little weight to the system. Do you have an estimate on how much the retracts added to the weight of the plane, compared to the weight of using the standard fixed gear? TIA

OK, I am new to all this, but I just ordered a FM-9 retract timer and if I understand correctly I will need an external BEC to provide enough power to drive the retracts.  No problem there, but who makes the external BEC and which unit should I get.  I am serious about going down this path with the Spitfire.
Andy

OK, I am new to all this, but I just ordered a FM-9 retract timer and if I understand correctly I will need an external BEC to provide enough power to drive the retracts.  No problem there, but who makes the external BEC and which unit should I get.  I am serious about going down this path with the Spitfire.
Andy

Hi Andy,

From what Jim says, it looks like his retracts pull around 450 mAh (if each gear is at 150 x 3?). So it looks like a small separate BEC will work. Here is a good selection from Hobby Lobby:

                  http://search2.hobby-lobby.com/psearch/svc/search.php?uid=2&q=bec

Maybe Jim will step in here and give us the exact make and model he uses in his setup. I'm sure any of the smaller ones from HL will do the job.

I too am interested. With all the extra power we have available, the drag of the fixed LG is not a big problem, but I think retracts will be worth the effort and weight just because it will look so cool!    There may even be some aerodynamic advantages, like the smoothness that Jim talked about. I seem to remember someone else using retracts with their wet power CLPA plane and they had similar improvements in smoothness. That would be a nice bonus. 

They sure would look awesome on your E Spitfire! 

Paul has been using the FM-9 timer with an on-board 7805 regulator to provide the 5 volts to run the timer and provide the signal amplitude. The 7805 is rated for up to 1A when heat-sinked, but it wasn't heat-sinked and clearly wasn't up to the job. The 7805 is a linear voltage regulator and so it is quite inefficient when used with a battery voltage as large as 18.5 volts, but that is not a problem with the very small current demands of just the timer. So, rather than trying to heat-sink the 7805 for the extra demands of the servos, it seemed advisable to design a new printed circuit board that had a connection for an external (switching) BEC, and this has proven to work well.

would be good to start a new topic on retracts - I am very intersted in getting some setup and I am sure others would appreciate a "how to" type post on this - including the wiring setup with BEC etc.

The easiest/fastest attempt to make it clearer is to attach the photo I send with the instructions. This first photo shows the retract circuit board for a setup where the ESC has enough current capability for both the timer and (especially) the retracts (ESCs like the ICE and JetiSpin). The microcontroller is programmed by connecting to the 6 pins at the top. Then it is detached and the 3-wire connector from the ESC is connected to the left-most three pins, with the ground wire oriented as indicated. The gear servo is connected to the 3 pins on the left side, observing the ground wire. If there is just one 3-wire connection coming from the electric retracts, it is connected as shown. If there are two separate 3-wire connections from the retract servos (perhaps a nose-gear in addition), they must be combined into one, using a "Y" connector (one example is the Mpi/Maxx Stock No. 3265, which combines two male 3-pin connectors into one female 3-pin connector). The "Y" connector sends the same signals to both servos through the white or yellow wire and it powers the servos through the inner 5-volt wire and the black or brown ground wire. (The circuit board routes the 5-volts and the ground from the 3-pin ESC connection to the 3-pin servo connection.)

There is a complication with using two motors with two ESCs that each provides a BEC; it is important to cut the center (+5V) lead for one of them so that the one with a slightly greater voltage doesn't try to charge the other one. And if neither ESC has enough current capability for the servos, cut the center lead on both 3-wire connectors from the ESCs to the timer and use this second circuit.

The second photo shows the circuit board for ESCs that do not provide enough current for both the timer and the retract servos (such as the Phoenix ESCs, especially with the higher battery voltages), or do not provide any BEC at all (Schulze). The only difference is that there is another 3-pin connector for the external BEC, for example the 10A BEC offered by Castle Creations and available from most retailers; only two pins are actually used, the center pin for +5 volts and an outer ground pin. The circuit board routes the +5 volts and ground to both the timer chip and the servo(s).

With all these words, I think maybe you're right about a block diagram being needed...

Hi Guys,

Only have a few minutes now, but I'll get you some exact specs and photos when I get home from work today if I can. Have a little family Christmas party to attend later as well. I can give you some rough parameters on the weight and set-up of these E-Flite Retracts and their successful use to date.

I am not using a trike gear set-up, I am using conventional gear in a T-Rex we bashed into an electric T-Bolt. I then bashed some more once I ordered the retracts and started to install them. My brother Wayne helped out as two great minds are always better than one:)

For any who have not used retracts in either R/C or control line applications, one must spend a bit of time insuring the construction around the spar where you will mount your wheel wells is carefully considered. Control line applications also must deal with your lead out wires on the inbound wing. The "angle" of the gear must also be considered for placement (I think most recommend 12 - 13 degrees forward sweep in a conventional gear set-up). Let's just say these are all important factors to getting your ship back on the ground in one piece, so use care when planning the installation lest your wing retract instead of your gear. There are lots of good construction articles and plans for R/C aircraft which can help you here.

I have not yet weighed the Castle 10 amp BEC though it is not significant to much degree anyway. Think the wires and connectors hanging out both ends weigh as much as the actual BEC.

The two retract assemblies weigh about an ounce and a half each, probably add 3 ounces to your total weight compared to just wire gear.

A Schulze ESC, whether the discontinued 18.46K F2B or the newer 18.61K F2B do not have built in BEC units.

I'll include some pictures of the installation and show everyone how everything fits together. I will start a new thread here specifically on electric retracts since it seems retracts have a certain appeal to the masses (and the judges too I hope

Thanks again,

Jim Smith

And here's the circuit when an external BEC is needed (as for the Schulze or for other ESCs that don't have enough current capability). Incidentally, Castle Creations gives the weight of their 10A BEC as 11 grams (0.39 oz).

Oops! Thanks, John. (Sometimes I think I could learn to like computers...)

Howard,
I have tried in vain to affix my stamp to my monitor, but when I hit send, the dang stamp stays here,,
Please advise,,
thanks

Even the extra battery capacity required, which is the number I'd be concerned about, is not a big deal.  Also, the drag of an imperfectly fitting fairing for the retracted gear may offset a significant amount of fixed gear drag.  If anybody would like to see how much drag his round-wire, exposed-wheel gear has, he could send me a stamped, self-addressed email message. 

  Here's a preview - it's A LOT.

    Brett

I admit i have not read every post but i am curious where the engines will be ?

Hi Jim,

Not sure if Bob posted pictures of the nacelles or not.  Lots of posts to go through! LOL!!  I have seen them "somewhere" and it will look sharp when all together!

Wow, drawing on paper with a pencil ... a man after my own heart.

Looks very cool, Bob. Electric twin with retracts. Going after the whole enchilada. I like that.

Quaint CAD system.

Okay Gang ...
show of hands here: how many of you working in CAD find that the swoopy curves you draw are somehow limited by what is easy to do with your drawing package?
later,
 Dean P.
 

Hi Mark,

That looks almost like an A-6 Intruder that I have been wanting to build as a stunter since 1969! LOL!! Really!  Haven't even tried to draw one up.......  Would like a 650-660 size plane.  Maybe make it an electric ducted fan job!  With everything else that electric can do, that seems possible!  Would do one of the A-6's that served on the Enterprise while my Dad was on board..  I don't think the planes in the Squadron that he was M&M Officer for would make a stunt ship! (E-2B Hawkeyes   )

My heart lies with Scale stunt, but I haven't done one in over 40 years.  I have gotten a P-51"B" (modified from Mr. Hunt's P-51D) almost ready to paint, though.  Just need to replace the compressor.  

My only real "foray" into "design" was taking Bob's Saturn and making it look like Billy's Juno!  But that one has worked out real well!  

Wouldn't know how to boot up a CAD system, but Aaron does.