WELCOME TO JETEX.ORG
Jetex.org was set up in 2004 and, with its active forum, quickly became a comprehensive online resource for free flight jet modellers all over the world.
The original Jetex.org site covered the historical and technical aspects of small rocket motors used in model aircraft, hydroplanes and cars, of which the British post-WWII Jetex motors and modern Rapiers are the best known.
The original Jetex.org site is well and happy, but in retirement. It can still be accessed at: archivesite.jetex.org.
Building on the old website's success, the present Jetex.org site includes lots of new information, a model gallery, links to other relevant sites and a growing online store.
The active forum discusses everything from how to build and fly small model jets, to reports of meetings and collecting vintage motors.
We welcome contributions from fellow modellers, rocket scientists, historians and micro rocket enthusiasts.
We hope you enjoy looking around the site.
Do join the Jetex Forum or contact us if you have any questions or would like to contribute.
And please visit our About Us page – why we're here, how we got here, who's behind it, and, most importantly, how you can help Jetex.org become even better!
A recent and very welcome addition to the small team of fliers of rocket powered free flight models is Martin Lambert. Martin is a superstar of reaction powered model flight as he is the designer and manufacturer of a range of miniature gas turbines, the Kolibri range. These units are engineering which masterpieces generate up to 5 kg of thrust and, of course are intended for large radio control models. Last year I paid a visit to Martin’s workshop which is rather north of me here in Munich and a little south of Frankfurt.
Kolibri (humming bird)
When I visited him Martin demonstrated one of these turbines in his test area. He has a grown up version of the thrust test rig that I use for testing the Tendera motors and a very well appointed workshop and test chamber.
Martin also has a collection of model aircraft piston engines some of which have been modified by him for radio control. I recall, I think, a Frog diesel which has had an R/C throttle added to it.
Martin also showed me a video of another one of his brainchildren, this was a hybrid rocket motor using nitrous oxide, which is available as a propellant for whipped cream, and I think celluloid as the fuel component of this hybrid motor.
However, in recent times Martin has been talking to us and sharing his experiences with Tendera powered free flight models. He’s produced a Jetex Wren modified for Tendera L1 power and a beautifully executed Graupner Temco Pinto which is also modified for Tendera power.
I’ve included several of Martin’s excellent photographs by way of illustration.
Martin is a master craftsman and modelling custom canopies is but one of his skills.
The model featured is a Graupner Temco Pinto 420mm span, 400 mm long.
All up weight 28gm with an L2 motor 38gm.
Covered with Japan Gampi paper 9gm/square meter. Then coated with nitrate dope and finally airbrushed with Revell Aqua Color acrylic.
2021 has seen the most widespread marketing of miniature, sustained thrust, solid fuel reaction motors since the days of Jet-X. And about time too, that was in 1986. For this we have to thank Piotr Tendera who has taken on significant expense and effort to get the CE mark for his Tendera motors. And while it might be argued that this has resulted, due to the mandated use of the wider green fuze, motors with a lower overall Specific Index. But, for myself the widespread availability of the CE marked motors is a price worth paying. Already we are seeing signs of interest from people who are outside the usual demographic of the vintage modeller. I expect to see some novel and interesting Tendera powered creations appear over the next months.
Additionally, I think, we are likely to see the most interesting developments using the larger of the motors in Piotr’s range. The L3 and L4 both offer some new possibilities and on these fronts I’ve been making (rather slow) progress.
Radio Control is of course one possibility. Indeed, one of my correspondents from here in Germany (Frank Schwellethin) has been flying R/C with the more usual short duration motors from the Estes range and he will now, I think, have a go with the Tendera type.
Frank sent me several videos of his R/C rocket gliders in flight and inspired I was moved to complete a Klima Me163 and fit it with an Tendera L4. (This is intended for a D3 model rocket motor.) I haven’t had the chance to fly it yet as I’ve been awaiting the delivery of a miniature receiver, a Lemon Stability + from the USA. This, as its name suggests, is not just a receiver but it also includes additional hardware to build in a modicum of pitch and roll stability.
Electronic stability is the second possibility and it has long been an interest of mine. Since I started hardware that weighed over 50 Kg can now effectively be replaced with modern electronics weighing just a few grams. Luckily for me, the principals, and the maths, remain the same.
Now R/C receivers such as the Lemon and the Spektrum SAFE range include the ability to re-establish hands-off level flight at almost no additional cost. And configurations such as quadcopter, that have no inherent stability, and even helicopters without the stabilising fly-bars are feasible. But what about fixed wing free flight and specifically scale, reaction powered flight?
Seeing a recent copy of the Aeromodeller I feared that once again I'd prevaricated too long. The byline, ‘Low wing FF stabiliser’ caught my eye. The article, by Steve Glass, sounded something like what I had in mind. In fact Steve is using an add on stabiliser, the A3S3, designed to work, downstream as it were, from a conventional RC system. Steve has added some circuitry to simulate the pulse stream from an R/C receiver and, it must be said, this is pretty much purely a wings levelling system. What I have in mind is something more specific for reaction power. Additionally, the A3S3 has a setup facility that must be installed on a PC or mobile phone. Not, I fancy, something that will find favour with everyone.
For me what is required is something that can be set up on the flying field. The user can set the glide angle manually and adjust the rate of ascent. The controller consists of a solid-state gyro accelerometer board, a micro controller, battery and two miniature servos.
One would go to the field with the model with controller installed, switch on and first sort out the power off glide with a used motor installed. When this is satisfactory, select (guess) an angle for power-on ascent. This could be done by holding the model at the desired pitch angle. This is saved in the controller with a button press.
The model is then loaded for powered flight and hand launched with the motor building up thrust.
The controller detects an X axis acceleration from the thrust which it can integrate to approximate airspeed. The appropriate pitch up is wound in on the elevator/elevons. (The board would need to be capable of managing elevator and ailerons or elevons). Perhaps a potentiometer is used to preset the power on flying speed. The controller would start to wind in pitch once this airspeed is achieved.
We should now see the model climbing to best altitude. The controller detects the end of the thrust phase and changes the pitch trim to that for best glide. We might also have a gentle turn trimmed in!
Sounds simple and maybe all this is justified as a means to achieve that perfect scale, no dihedral, rear mounted motor Lockheed U2.
But what class of model would this be? It’s not R/C, it’s not C/L and its not quite F/F either. I leave that philosophical question as an exercise for the reader.
Looking forward to doing some flying in 2022.
Hello from Terry and Tendera developments
|Type||Thrust mN||Duration Seconds|
Page 1 of 2