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Round the pole

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gary davies-jones12/03/2012 10:14:24
89 forum posts

Hi Jono,

we 215 City of Swansea are flying RTP. Got a feeling Llanelli are also still RTPing not sure about anyone else in the wing. Where are you based? Are you RTPing?

Fortunately we are a large squadron (over 120 on the books) and have reasonable resources for this sort of things. I do however agree that the price seems a little high. With two C.I.s as members we can supervise 8 cadets but that cost us over a ton.

During the Lees inspection last year we pulled our RTP demo for insurance reasons. One of the inspecting officers was not sure if we were insured as technically the aircraft is not flying as it is tethered and indirectly in contact with the ground. Interesting thought I know, however in this increasingly litigeous society we are taking no chances.

Gary

Jono14/03/2012 10:59:06
10 forum posts

Hi Gary,

I'm over at 2499 in Berkshire.

We haven't done much RTP recently as I just haven't got round to it really. I now find that it's no longer on the list of insured stuff (along with ten pin bowling).

I'm a BMFA Country Member myself, but I don't really see the need for the BMFA insurance for RTP. Especailly as a Sqn of 40 odd cadets it is an occasional activity for us, mainly in the summer. (We use our Spooner Hut which means the main hall is out of commission to anything else).

I think I'm going to contact BMFA and see what their stance is. Will let you know.

Not sure why promoting an interest in aviation is so hard these days!

Cheers,

Jon

gary davies-jones15/03/2012 12:32:05
89 forum posts

Hi Jon,

let us know how you get on, and perhaps we could have an interwing flyin/combat daysome time. PM me if you fancy a go at that.

Gary

(C.I. Davies-Jones)

Simon Chaddock13/05/2012 11:22:52
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5692 forum posts
3026 photos

Jono

When I did school fete indoor displays I did eventually erect a 6' high fence around the circle, well actually just around the bit people stood around. A very light weight open mesh, the sort of thing fruit growers use to keep birds off.

I did it as much to keep people away (there was always somebody who wanted to see how close they could get!) than for their protection. It was covered by the school insurance (so the head told me!) but under the circumstances I felt a demonstration of "reasonable care" would not go amiss.

If the BFMA insurance covers conventional control line I would have thought electric RTP was very tame in comparison.

Alan Cantwell13/05/2012 11:43:07
3039 forum posts

i have a fair bit of RTP stuff, its on the list to be thrown out, never used it, it was part of a job lot i came by once upon a time, their are several scalextric type controllers, a yellow kiel kraft transformer thing, and whats left of a pole--the pole may take some finding though, but it only bearings and attachments, so not too bothered about it, if anyone wants it, just yell, collect only form oldham, lancs

Cyclicscooby13/05/2012 12:18:16
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874 forum posts
531 photos

Well.. Never heard of RTP before this post, and i'm 40.. !!

My initial thoughts, were that it's like flying scalextrics.. A lesser cousin to control line.. Like a DIY cheapy plastic Mattel game from the 70's.. Whats the point in that today, when RC is so cheap... !?!?!

Then I started reading the replies, and realised it's alot more than that.. Building and experimenting at that early age obviously ignited the spark in many of you..

So, I take back my initial thoughts,and wish you the best with the cadets..

Luv

Chrisie.. xx

gary walker 112/01/2015 21:50:07
1 forum posts

wow i came across this forum looking for an "easy" way of introducing my nephews to rc planes as they love the cheap helicopters and it brought back memories of when i was a cub scout in the 80s in chichester

we had a leader called ken murch who being ex raf was nuts about planes even to the point of building a fullsize glider for the CCF at chichester high school for boys and yes it carried the pupils! i never saw the glider just photos of it unfortunaty

anyways he built his own version of RTP and can remember the hours of fun i had building the planes in the scout hut and flying them in the field my best memory was the model of a hercules ken built which included the ability to drop a bomb while flying? dunno the ins n outs of how he did it but would love to hear from anyone who remembers ken kenneth murch?

sorry for the long thread lol

Robin Colbourne28/03/2020 14:01:04
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552 forum posts
17 photos

With all this lockdown of flying sites and being grounded at home due to Coronavirus, my thoughts have wandered back to electric Round the Pole.

Until earlier this month, the last time I flew RTP would have been in the 1980s at RAE Farnborough. Before that we flew in the Scout hut and on the lawn at home. I even remember my cousin from Canada buying a Harry Butler set from Ray Brown Models in Portsmouth, and flying in my gran's dining room, which couldn't have been more than about ten foot square.

At our club meeting, earlier this month, one of our members bought his set up along and flew several models including a KeilKraft Ercoupe with a geared motor, a Britten Norman Islander from an old Harry Butler kit, and a single rotor autogyro.

Eyeing up the current lawn at home, I reckon with a few plant pots being moved, I could fit a small circle in, although it may need hand launches unless I give the lawn a 'US marine recruit' haircut.

Does anyone else fancy having a go?  Please share your experiences old or new.

Here is the RTP Hut page. I'm awaiting a reply to establish if they are still trading and have stock, but its a good source of ideas and info nonetheless.

Electric Round The Pole - The RTP Hut

Edited By Robin Colbourne on 28/03/2020 14:19:19

Robin Colbourne28/03/2020 14:53:29
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552 forum posts
17 photos
I've just had an email from Phil at the RTP Hut. He is very much still trading, and dispatching orders all the time the Royal Mail is still taking them.
He also added that he will be re-releasing the Harry Butler Pitts Special Kit and also has Gloster Gamecock prototype which has just flown.
Cliff 195928/03/2020 16:15:56
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477 forum posts
76 photos

I think it was at the Ally Pally Model Engineering Exhibition in the early 70's when I saw RTP, they had huge circle above the stands, I remember a Lancaster 'doing the rounds', it blew me away. I came away with a Harry Butler profile Spitfire which flew about 30 years later when I had a garden.

See my just-uploaded video for a sort of RTP Lol.

'Corona Lock-Down Microaces Combat'.

i12fly28/03/2020 23:16:20
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632 forum posts
22 photos

If you use the Keil Kraft yellow transformer box as power source, make sure you put a fuse in the line to each output.

If you don't, when (not if) you get a short on the electric lines it will blow the transformer windings. Can't remember what size fuse I used but it was appropriate for the motor draw.

Andy Stephenson29/03/2020 00:28:26
137 forum posts
21 photos

A while ago I designed a simple electronic RTP controller that used a resettable over current trip...

oxrtp1.jpgoxrtp2.jpg

Robin Colbourne29/03/2020 02:24:11
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552 forum posts
17 photos

Andy, Thank you for posting your power supply circuit diagram. Three questions:

1. At risk of appearing totally thick! Do the hand controllers go in line on the motor outputs shown?

2. Can you use standard Scalextric hand controllers with this speed controller?

3. How do you vary the input voltage to suit differences in line length?

Phil Green29/03/2020 02:30:05
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1582 forum posts
318 photos

As teens we used to do a lot of club slot-car racing and one of the competitions I came up with was racing two cars per slot, and I was thinking the principle might be useful for RTP scale functions like swing-wings, retracts, bombs etc instead of a third wire.

We fed the controllers with AC, and for each slot, one of the two cars would have a diode in series one way, and the other car with the diode reversed, then a 100uF cap across the motor. The two controllers for that slot also had opposing diodes, so one car ran on positive half of the AC and the other on the negative half, giving completely independent control of the two cars through the same slot.

We ran two or four slots, ie 4 or 8 cars, which would start exactly half a lap apart and the aim was to catch and nudge the other car. It was brilliant fun with 4 cars, hilarious with 8.

Its not directly relevant to the topic but maybe a similar system could be used for auxiliary RTP functions?

Cheers
Phil

Edited By Phil Green on 29/03/2020 17:14:33

Dale Bradly29/03/2020 06:54:12
14 forum posts
5 photos
Posted by Phil Green on 29/03/2020 02:30:05:

We fed the controllers with AC, and for each slot, one of the two cars would have a diode in series one way, and the other car with the diode reversed, then a 100uF cap across the motor. The two controllers for that slot also had opposing diodes, so one car ran on positive half of the AC and the other on the negative half, giving completely independent control of the two cars through the same slot.

That is a brilliant idea! So simple, but effective.

Andy Stephenson29/03/2020 12:01:28
137 forum posts
21 photos
Posted by Robin Colbourne on 29/03/2020 02:24:11:

Andy, Thank you for posting your power supply circuit diagram. Three questions:

1. At risk of appearing totally thick! Do the hand controllers go in line on the motor outputs shown?

2. Can you use standard Scalextric hand controllers with this speed controller?

3. How do you vary the input voltage to suit differences in line length?

Robin,

I think you misunderstand, this IS the controller, you need a DC power supply to feed it. The power is applied to the rails, positive and zero(-ve) and the motor is connected to where it says motor o/p. The speed is controlled by the potentiometer labelled VR1 on the schematic.

No need to use any other controller as explained above

The input voltage needs to be enough to overcome the resistance of the lines so using a variable power supply is the best solution.

We have been using the same controllers since I made them 25 years ago and they are still going strong. They were built into small plastic project boxes with slider pots some with spring returns. We have had them on really long lines at the Model Engineering Exhibition and short lines at club meetings in a village hall. The power supply we use is one in yellow case with various output voltages, I'm not sure who made it. It looks like Harry Butler isn't selling RTP kit any longer so it may be necessary to get a laboratory style bench power supply for this application.

Robin Colbourne29/03/2020 16:18:56
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552 forum posts
17 photos

Thanks Andy, That clears things up. I was looking for a something variable but missed VR1. I'm more mechanical than electronic!

Phil at the RTP Hut does some variable voltage transformers. See here: RTP Hut Power Supplies

If you click on the image it gives more detail. For instance the description of the large one is:

Large Mains Power Supply Unit 4524

pu_4524
 
 
£ 150.00 each

Suitable for single or dual model flying on line lengths from about 3 metres to about 10 metres. Rated outputs are:- 24 volts, 30 volts, 38 volts, 46 volts and 54 volts at 6 amps. Unit consists of Heavy Duty mains transformer, bridge rectifier and smoothing capacitor housed in a plastic case. Voltage selection is by 5 position break before make rotary switch. Three pairs of D.C. outlet sockets are fitted.

Unit size: 175W x 110H x 150D

Weight: 5kg approx.

Edited By Robin Colbourne on 29/03/2020 16:19:16

Phil Green29/03/2020 16:55:32
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1582 forum posts
318 photos

Those seem very expensive for what they are. A proper 30v switch-mode current & voltage controlled bench PSU can be had for much less, and is a versatile tool for other purposes.

Our modest RTP setup used swapped-out car batteries, the weight helped tether the pole too, and kept voltage drop to a minimum by only extending the pwm pot wires outside the circle, rather than the power wires.  PWM speed controllers can be as simple (555+mosfet) or as complex as you like (processor controlled with envelope shaping etc) all very cheaply, theres absolutely no need to spend that kind of money !   smiley

In fact if you have a spare car battery, an old brushed speed controller and one of those £1 servo testers from ebay, plus a few bits & bobs to make up a pole, you're already good to go without spending a penny!

 

 

Edited By Phil Green on 29/03/2020 17:21:24

Simon Chaddock29/03/2020 18:59:57
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5692 forum posts
3026 photos

I first did indoor round the pole in the early 1960s using 3V early Japanese motors. Marginal flight and the motors did not last long with 12V transformer supply.

Much more success with later proper 12V motors which allowed more realistic planes to be built.

Given there were always two wires my big step was utilise them as a control line function as well. The centre pylon gets a bit more complex to not only move the wires but also to lead the control to the pilot outside the circle.

With elevator control RTP flying became rather more gentle allowing for very intricate models to be flown successfully.

Always a keen scale builder there was attraction in building small and very light yet with a reasonable prospect of it actually surviving. First a Sopwith Pup built late 1968 in classic balsa and tissue style.

RTPpup

20" span with a geared slot car motor driving a hand carved balsa prop. Just under 2 oz (40 g) but the motor alone accounts for nearly half of that!

Even on short 6' lines it flew well and at almost a true scale speed!

It prompted me to build a matching Fokker Triplane.

SC-Triplane-1c.jpg

18" span and modelled on one of the planes flown by ace Wernher Von Voss. It weighs 2.25 oz (64 g).

Built in 1969 to almost perfect scale inside and out. This is the only picture I have of it under construction.

Triplaneconstruction1

The fuselage with full internal bracing (cotton thread) is made from medium 1/32 round balsa to simulate the steel tube of the original.

A similar geared slot car motor and the Oberursel URII rotary actually goes round with the prop.

SC-Triplane-2.jpg

Just to confirm that control line RTP can be quite 'gentle' I still have the Triplane in the loft although at 50 years old it is firmly retired. wink 2.

That's quite enough of my reminiscing!

 

Edited By Simon Chaddock on 29/03/2020 19:00:54

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