Researching the ancient Ripmax Futaba M6

[NK Guy]

Hi, everyone!

I apologise for being an interloper here. But I'm researching the Ripmax Futaba M6 RC transmitter from the 1970s, and I'm wondering if anyone here with long memories might be able to help.

Why? Well, basically I'm researching the R2-D2 props used in the original Star Wars films, and the M6 was the transmitter used back in 1976. It was used to control the sole radio-controlled R2-D2, and also some of the other droids such as the wheeled "Treadwell" robot.

Here's the R2-D2 site:

https://sites.google.com/site/3dsfinfo/astromech-pages

Now, what I've found so far is:

- this was a product produced by Futaba of Japan, cobranded with Ripmax, a UK reseller/retailer.

- The M6 was a 27MHz AM radio with 6 channels. (hence the 6 in M6) Were any of them 35MHz? 27MHz meant a lot of potential interference from radio communications, such as CB radios imported illegally into the UK.

- It shipped with rechargeable NiCad batteries in an internal pack. You had to unscrew the bottom to swap out dead batteries if you didn't have time to recharge.

- It had a small panel for interchangeable crystals. No PLL capabilities.

- The removable aerial had optional coloured pennants to indicate the channel in use.

- The box had an attachment point at the top centre for an optional neck lanyard for hands-free operation.

- The transmitter had override capabilities - a socket and press and hold switch so a "buddy" or "trainer" could take over control when a novice is flying a plane.

So a few questions:

- Were the devices proportional? I see conflicting information about that. Not that it matters particularly for Star Wars, since they used a simple multi-position switch driven by a servo at the R2-D2 end with 3 discrete motor speeds.

- Were they digital in any meaningful fashion? I've seen references to digital, but it really looks to me that they're basically analogue devices. There are no ICs on the board. There's certainly nothing useful like error correction!

- What did it list for in 1976? It seems maybe around £200 with servos and receiver?

- Any suggestions on a good similarly-coloured spray paint to redo the casing? I have a particularly filthy old transmitter that I'd like to clean up somewhat. It's a sort of strange metallic beige colour - a plastic overlay over a sheet aluminium chassis.

- Apparently there are people who have done full-guts conversions of these devices to talk to 2.4 GHz devices. (ie: just keeping the sticks and the chassis) Anyone have any information on this?

Thanks in advance for any comments or memories about this product!

- NK Guy

[gangster]

Hi I am surprised that no one had been back to answer your question so I will start the ball rolling

They were a lovely set of radio well built and reliable

They were not digital as we know it today but used a protocol that was common to other makes. So much so that you could use receivers of another make Basically that used a 50 hz clock. The encoder output was 6 pulses 1-2 ms wide the pulse width was controlled by the sticks with nominal 1.5mS centres. A long rest pulse and it started again. So yes as you said they were analogue not digital . I am sure they were never on 35 MHz. Later models were Frequency modulated and I think the FM ones were either available on 35 or were convertible The FM version as far as I remember was in a brushed aluminium case
They were rechargeable as you said and the battery was effectively built in.

Edited By gangster on 08/09/2020 21:58:29

[Jonathan W]

Yes, the later ones were available in FM, both 27 and 35 MHz. They also changed at some point to black open gimbal sticks instead of the chrome bezel type. However, the basic circuit board with discrete analogue components carried over to the FM versions, only with the RF section updated. The FM ones did have a brushed aluminium case, as mentioned by gangster. They were good quality and a well preserved one should easily still be in working order today.

I have a few spares at home and might be able to supply you a better condition case, but I'm away until towards the end of the month.

[J D 8]

I still have my Futaba M series from 1979 in working order. The were very nicely constructed with brushed aluminium case and very tidy soldered boards inside. You are right with cost of close to £200 . Proportional 4 channel is mine . [ Yoda speak ]

CB was not a major problem until it became a fad in early 80's

Conversion to 2.4 is possible with a " hack module " leaving all original boards in place although part is disabled by removal of crystal.

[NK Guy]

Thanks for the information! Very much appreciated.

The transmitter I have is really quite filthy.

From production reports in 1976 the operators had massive problems with reliability, unfortunately. Star Wars' effects coordinator apparently would angrily blame "taxis" when a robot failed to respond properly - even when out in the middle of the Tunisian desert, miles from any passing British taxi! I'm wondering if the receiver aerial was blocked by the metal casing of the droids - but you'd think they would have thought of that and stuck the aerial outside...

- NK Guy

[NK Guy]

Here's R2-D2 being controlled by John Stears, effects supervisor for the film. The middle leg drop mechanism for the robot was damaged and the team are struggling to get it to cooperate.

Note the Futaba M6 in its full glory!

- NK Guy

[Simon Chaddock]

NK Guy

45 years ago as a young man and as I was not on a film budget I could only afford a 'budget' Ripmax Futaba 2M.

35 MHz and I did use it in a glider.

I still have it with its box.

Much later I did pick up an M5 at a car boot sale. Rather older and on 27 MHz it used weird 5 wire servos.

It did still work at the time but I have never used it in anything.

[Phil Green]

Hi, our little group specialises in flying old radio sets from that era, some we restore back to original working condition and some we internally convert to modern electronics - either way this is done with the intention of getting these sets back down the flying field where they belong, usually in an appropriate 'period' model. You'll find that the M6 is a very common conversion, they were mass-produced and are not at all hard to find in clean condition.

For cleaning everyone has a favourite method, I use 'Barkeepers Friend' in solution which I've found very effective, thinners used carefully will remove engine-oil that has set to a varnish, unfortunately we havent found a way to economically restore chromed stick bezels, but metal polish used sparingly will improve them. The stick pots will benefit from a squirt of Electrolube and a workout.

Besides the propo section of our own forum, there is a dedicated thread on RC Groups you should check out:
Vintage-Old-Timer-Radio-Control-Systems - in fact your query rings a bell, have you asked there previously?

Posted by gangster on 08/09/2020 21:57:04:

Basically that used a 50 hz clock. The encoder output was 6 pulses 1-2 ms wide the pulse width was controlled by the sticks with nominal 1.5mS centres. A long rest pulse and it started again.

Sorry no, thats not quite correct. The M6 was a six channel set, so the encoder outputs seven pulses. These pulses are not 1-2ms wide, they are around 300uS, the actual value isnt important as each stick position is represented by the time between two pulses, edge to matching edge, rather than the width of the pulse itself. Between the last pulse and the repeat of the first there is a syncronising delay of a few milliseconds, typically 6-10ms and again this value is not at all critical - in fact it can vary depending on the stick positions - basically it pads out the time remaining after the stick pulses to 20ms giving 50 complete frames per second.

Cheers
Phil

[FlyinFlynn]

You might want to email Phil Green . Phil and Shaun run a museum of vintage radios and have an immaculate M6 in its box. I am sure they will be a mine of information for you.

Edited By FlyinFlynn on 09/09/2020 10:27:34

 

opps ...too late!

Edited By FlyinFlynn on 09/09/2020 10:28:18

[mal brewer]

Posted by Simon Chaddock on 09/09/2020 00:28:41:

 

Much later I did pick up an M5 at a car boot sale. Rather older and on 27 MHz it used weird 5 wire servos.

It did still work at the time but I have never used it in anything.

. Ah, the Futaba Digimax 5, my first proportional radio. I bought mine with three servos,I couldn't afford to buy 4 ! I bought the extra servos a few weeks later. I seem to recall it cost me about £130 with three sevos,a lot of money at the time. Yes it did have five-wire servos, I think they were FD 11's, a linear servo, two with a red label, two with a black label for reversed travel ( no servo reversing then ). It was a very good radio, very reliable,and came with a full set of 6 frequency crystals and flags. The only weak point was the servos were prone to stripping the gearing on the ouput racks on a heavy landing, but it was a 2 minute job to strip and re-assemble the servo,and spares were cheap and readily available. Yes an excellent radio, I've used Futaba ever since.............Mal

Edited By mal brewer on 09/09/2020 11:28:32

Edited By mal brewer on 09/09/2020 11:43:37

Edited By mal brewer on 09/09/2020 11:46:03

[Peter Christy]

The digital vs analogue argument is not completely clear cut. Many early proportional sets were genuinely analogue, and operated in a variety of ways. One common method was to transmit two audio tones alternately. The frequencies of the audio tones provided two channels, the mark/space ratio between them a third channel, and the rate at which they alternated a fourth.

Other systems used a sequence of four different audio "tones".

At the receiver, the signals were decoded into a varying voltage that was fed to the servos as a control signal, eg: 1V = left, 3V = right.

Analogue systems provided very good interference protection, but suffered terribly from drift, poor resolution and slow response. It was also difficult to re-use circuitry for different channels, and almost impossible to implement more than four proportional channels.

The first digital system (designed by Don Mathes and Doug Spreng) was an attempt to overcome these issues. It was digital in the sense that the signal was either "on" or "off", but sort of analogue in the sense that it was a pulse width that represented the control signal. However, even in the servo, there were no varying voltages, the drive to the motor being either "on" or "off" (0 or 1, so in a sense "digital".

Some early digital systems did convert the "digital" signal to a true analogue one, as at the time, the digital servo amp devised by Doug Spreng was a spin-off from military technology, and some manufacturers were worried about being prosecuted by the government! This didn't last long, though, and after short time everyone adopted the Spreng design. It was so successful that it is still in use today!

The original Mathes/Spreng Digicon did transmit the full control pulse of 1-2 mS per channel. However, back in the days of AM rather than FM, this caused problems in the design of the Automatic Gain Control - AGC being an essential part of an AM receiver. It was Frank Hoover of F&M (a major American manufacturer at the time) who is credited with suggesting that rather than transmit the whole pulse, it would be better to transmit a short "marker" pulse to indicate the beginning and end of the actual control pulse.

With the introduction of digital integrated circuits a few years later, this had the added benefit of making a "digital" decoder extremely simple in the receiver.

So you see, the digital vs analogue argument is not clear cut! Early "digital" systems were neither truly analogue nor truly digital. However, the fact that we still use the same system to this day to drive our servos, added to the fact that the control signal is either "on" or "off" (0 or 1) leads me to believe that it is more digital than analogue!

--

Pete

[Mike Etheridge 1]

interesting , I still have my boxed M4 set which is 27mhz and bought new in the 1970's. I last used it for slope soaring about 6 years ago with my second hand Micro Mold Colt glider bought 1976. It is pictured here, receiver only in my Micro Mold Sprite which I bought with the radio from a model shop at Crown Point in West Norwood. I have used it in a number of my early radio planes and a boat, but on the first flight of the Sprite the radio suffered interference from CB Radio and the Sprite which had been bungee launched piled in nose first, and the plane although repaired still looks somewhat tatty. I am sure the radio will still work.

[J D 8]

My M series, the set is easy to open up by just pressing in the backplate at the bottom.

[NK Guy]

On a related topic, does anyone recognise this thing? Was it a commercial product?

R2-D2 controller during the filming of the Empire Strikes Back in 1979.

[Former Member]

[This posting has been removed]

[Brian Cooper]

WOW, a Futaba M6 radio.... that takes me back to my more youthful days.

I had two sets in the 1970s, and they were fabulous radios. Very reliable but basic by today's standards. . No rate switches or computer mixing, etc, etc.

The servos came with two different colour identification stickers on them for different rotations, so if your installation needed a servo to go the other way, you simply swapped it for the other colour. . . Alternatively, you opened up the servo and swapped some wires around to make the thing go the other way. . . . Happy days.

B.C.

[Cuban8]

As a teenager I used to look on in awe at the flyers and boat operators with their Futaba M series radios. It's hard to fathom it today but they really were top of the range gear and expensive for what you got. When I stared to earn reasonable money I eventually saved up for the later 'Gold' system in 1982 - only five channels rather than the very posh seven - the five was almost £200 then so something like £600 now (according to a money website). lasted me for years until the early 90's when I eventually got a computer radio - FF7.

I was in the electronics industry and saw the insides of a lot of gear used in industry and the build quality of the Japanese Futaba radios of the 70s/80s was superb, as good as anything with very high quality and consistent soldering. Don't know how they made any money from them despite their price although they did cheapen things a bit over time but their reputation still remains.

Still have the TX in my workshop.

[NK Guy]

Hmmmm.

I posted an image but it appears as a broken image icon, and I can't edit the post. I can't seem to upload photos to this site at all.

Here's a link to the Empire Strikes Back radio remote photo.

https://40bc6f4f-a-62cb3a1a-s-sites.googlegroups.com/site/3dsfinfo/esb-rc-controller.jpg

Edited By NK Guy on 10/09/2020 09:58:52

Edited By NK Guy on 10/09/2020 09:59:17

[Former Member]

[This posting has been removed]

[Former Member]

[This posting has been removed]

[Former Member]

[This posting has been removed]

[NK Guy]

Posted by Barrie Lever on 10/09/2020 10:29:23:

That link is to a photo of a Futaba 'J' series.

Awesome! That looks totally right.

Actually, a correction. That photo was taken during the filming of Return of the Jedi in 1982.

There's also this radio in the background of another photo. Would anyone recognise this one?

**LINK**

- NK Guy

[Alan Gorham_]

That picture came up as a very pixellated image but to me it looks like a McGregor Digimac set.

[NK Guy]

Posted by Alan Gorham_ on 10/09/2020 12:51:24:

That picture came up as a very pixellated image but to me it looks like a McGregor Digimac set.

 

Yes! I think you're right. Thank you. It looks like McGregor made radios in a couple of different widths; that being a wider one.

I found a number of photos finally which show the radios used in filming the Empire Strikes Back, but they're all pretty low-resolution and terrible.

https://40bc6f4f-a-62cb3a1a-s-sites.googlegroups.com/site/3dsfinfo/various-esb-radios.jpg

 

Edited By NK Guy on 10/09/2020 13:11:04

[Former Member]

[This posting has been removed]