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Flying electric in the days before LiPo, NiMh, ESCs and foam!

quorneng

Well-known member
#1
Electric flying actually goes back a long way (Col Taplin converted a Radio queen to electric in 1954) but it was rather specialised and even more expensive than the then substantial cost of IC engines and RC equipment!
Like many young lads in that era I learned to build and fly (poorly) simple rubber powered models but living in the UK suitable days of weather condition for such lightweights were few and far between - and they still are!
At about that time the first of the cheap small lightweight Japanese (Mabuchi) motors appeared but without suitable batteries any form of electric free flight was no nearer. The only solution available to my budget was to fly electric was 'round the pole' and space limitation required short (6 foot!) lines as well which in turn meant the planes would have to be small and light.
Initial experiments did get things to fly but using 12 Volts on 3 Volt motors meant they did not last long. With the motors weighing more than the rest of the air frame it was not long before some form of elevator control was considered beneficial.
As a DC motor requires two wires why not make them act as 'control lines' as well.
With such short lines this required the control line mechanism to be operated from outside the flying circle.
The result of elevator and fully variable power allowed quite a range of lightweight 'balsa and tissue' planes to fly 'control line'.
A peanut scale Andreason A4b.
Peanut1.JPG
A slightly bigger Keil Kraft Fairy Gannet
SC-Gannet.jpg
A free lance transport 'twin'.
SC-Yellow_Brick-1.jpg
A sort of Liberator.
SC-Liberator.jpg
All the above direct drive with home made balsa props.
In fact control line RTP proved to be a very 'gentle' form of flying so even super light air frames could survive.
The rise of slot cars meant that small (1oz) powerful 12 V motors became available and suitably geared they could generate several ounces of thrust.
A true scale 20" Sopwith Pup.
rtpPUP.jpg
The wing section is scale so the cotton rigging is fully functional. The geared motor drives a scale carved balsa prop. It weighs just 2 oz and the motor accounts for 1 of that!
It flew well enough but that thin under cambered wing section meant that like the original any stall was to be avoided.
With lessons learned next was Fokker Triplane built to the same scale it has (I still have it 45 years on!) an 18" span.
SC-Triplane-1a.jpg
With its 'horse shoe' cowl the scale engine is rather more visible so it goes round with the prop!
To be continued!
 
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quorneng

Well-known member
#2
The object with the Fokker Triplane was make full use of the delicate nature of RTP control line flying to make it as scale as possible both inside and out by copying virtually every piece of wood and rigging of the original.
This is the only picture I have of it under construction. Triplaneconstruction1.jpg
The fuselage is 1 mm round balsa to emulate the steel tubing of the full size. The sheet balsa is just 0.5 mm thick. The rigging is cotton thread.
The slot car motor and the Oberursel rotary that is geared down 2.3 : 1.
SC-Triplane-2.jpg
A neat touch is the scale pull/pull lines (cotton thread) from the elevator to the control column in the fully detailed cockpit. The control line bell crank is simply linked to the stick!
The cowling is spun from a sheet of aluminium over a hardwood mandrel. It does help if your Dad is also very competent model engineer!
Decorated in the colours of a Triplane flown by Werner Voss it weighs 2.25 oz and flies very nicely. The slot effect of the three wings with their relatively thick section allows it to 'hang on its prop' as high angles of attack just as did the original.
Now over 50 years old it is no longer flown but it does still run.

Having built scale models of 'wood and canvas' types I wondered if it would be possible to build an all sheet plane that would be small and light enough to be flown in the same sort of way.
What I needed was a plane that had a relatively small wing span along with a big propeller.
The elegant Martin-Baker MB5 seemed to fit the bill.
M.B.5proto.jpg
And with a motor driving each contra rotating prop it would in effect become a twin!
To be continued.
 

quorneng

Well-known member
#4
Being all sheet covered (except the rudder and elevator which were fabric) my main concern was to keep the weight within bounds. My super scale Triplane came in at 2.25 oz. The MB5 would have a bit more wing area but using two motors and a great deal more balsa I feared the wing loading would result in a flying speed (if indeed it had the power!) that would require a line length well beyond the indoor space I had access to.
So the target was to built entirely in 1/32 balsa as a stressed skin monocoque. I reasoned that for the forces involved provided the skin was sufficiently supported it would have more than enough strength and stiffness.
One saving grace was the MB5 had true flat sided fuselage over most of its length and i had a diagram showing the profile of the major fuselage formers. As a result the construction was almost 'conventional' although rather delicate.
These are the only construction pictures I have. Could only afford black and white film in 1969!
MB5fuse2.jpg
The 1/32 ring formers had inner flanges to give the necessary rigidity.
MB5fuse1.jpg
The 'curved' parts of the fuselage had to be planked. Each plank had in effect be to shaped to fit' along its length, glued and pinned in place, To prevent the stress of bending the planks creating a 'banana' fuselage the planks had to laid on alternate sides. A technique not dissimilar to carvel boat building but as a young man I had time and eye sight on my side!

By comparison the wings and tail were relatively simple with straight tapers. No spar anywhere just ribs and the 1/32 balsa skin.

My Dad very kindly cut me a pair of alloy gears that gave an 7:1 reduction to the high reving "slot car" motors.
By mounting the motors side by side each could drive its own gear fixed to concentric shafts (steel inner, alloy outer).
MB5motor.jpg
The motors are wired in parallel. The nose of the fuselage is quite rigid enough to carry the front bearing.
The spinners are solid soft balsa with individual carved balsa blades glued into them.
As there there are some nice period photos to work from a fully detailed cockpit was added.
MB5ckpitS.jpg
The complete MB5
MB5frontS.jpg
As I had no opportunity to test fly it I felt it was appropriate to complete all the decoration un flown, not something I normally do!
Does it fly?
Yes it does although I had to build a special raised flying 'circle', with safety netting, so it could have its maiden flight at a school open day!
With straight cut gears its hollow structure makes a wonderful sounding board so it has an impressive sound even if its more like a turbo prop than a Griffon!
'Retired' as it is now 45 years old so only a rather poor quality ground run video.
 

Headbang

Well-known member
#6
It has been said I was born with a soldering iron in my hand. So it made sense my first plane would be a goldberg electra. 550 can motor, servo to a toggle switch for throttle, 1200mAh 6 cell nicad batteries. That was in the late 80's. I still have the wing in my garage. Next was a midwest aero-electric. Same motor and setup. I just converted that one to modern electrics and recovered it last year. They flew heavy, and slow, but I loved them. No dead sticks, no messing with fuel, more reliable then my cox .049's, started in the cold unlike my OS 40 on my kadet mk2. The best part was I was the only one in my club running electrics back then!
 

Piotrsko

Well-known member
#8
Nobody?

Ok that is a Phil Kraft "REEDS" system so called because there is a mechanical comb that vibrated like a saxophone reed when you move one of the control sticks. There 10 "channels" or 2 per servo. The servos are full movement one way or the other and slow typically 3 seconds left to right @ 5 lbft of force and 2 inches of travel. You fly by rapidly blipping the sticks one channel at a time however by trick tuning you can get rudder and elevator to work together on harmonics. Obviously you want a slow stable and BIG airframe. I have flown an aerobatic plank wing glider with a 6 ft span and about 1200 square inches of area on the Esplanade in Redondo Beach Ca.
Flying weight is 2 pounds, the battery is nicad and runs the system for about 1/4 hour. You have to tune the reeds to the transmitter at the start of each flying session.
This was state of the art in 66, with the exception of galloping ghost. Also since there are 10 combs You can play songs
 
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quorneng

Well-known member
#9
Going back over 50 years (I was 16) I did try electric free flight.
My Dad suggested using a bi-chromate cell which I had never heard of so being a serious model engineer he made me one.
The bi-chromate cell uses carbon and zinc plates in a solution of potassium bi-chromate and sulphuric acid!:eek: and delivers about 2V.
The first twin 3 plate cells in a 1"x1"x1" perspex case.
3platecell.jpg
I would deliver over 1 A for about nearly a minute before the bi-chromate was exhausted.
The second battery was the same physical size, a bit lighter and had 5 plates per cell. The threepenny bit shows how old the picture is!
5platecell.jpg
This produced a good 2 A for about 30 seconds and weighed just over 1 oz (29 g). It could deliver more current but the electrolyte would start to boil!
Nevertheless the performance was adequate for the very small 3V motor and I judged 30 seconds was plenty long enough for a free flight plane. Interestingly this cell had about the same energy density as a LiPo.
I built a very light weigh 48" span glider with a geared motor to house it all.
Flyer.jpg
It weigh just under 3 oz ready to go.

Of course it would require the very calmest of weather (and an isolated site!) to even attempt a flight and such days are few and far between in the UK.
Perhaps fortunately for all concerned it was never flown as I started making the much safer "round the pole" electric models I described earlier but an interesting exercise none the less.;)
 
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Piotrsko

Well-known member
#11
Today's oldie mouldie: mechanical mixers because NOBODY made electrical mixers. You want flaperons or V tail rudder functioning? Had to use one of these or hold your radio at a 45 degree angle. The center post or outside frame went to the elevator servo, the two outside parts went to the other servo and or the control surface. The big one was called a Vector Director, and came in a kit called a "Toadie" or a "Javelin" flying wing
 

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