参观Jets Munt工厂

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Jets Munt Visit
RCJI gets the opportunity to visit and look around the Jets Munt factory
作者：COLIN STRAUS
图片：COLIN STRAUS
原载《Radio Control Jet International》2014年2-3月

参观Jets Munt工厂

One of the engines produced in Jets Munt’s factory a short distance from Barcelona

History
     During a recent short break in the beautiful Spanish city of Barcelona, I was lucky enough to be allowed to spend one afternoon visiting Jets Munt SL, manufacturers of the renowned Merlin turbines, as well as the incredibly successful VT80, which has proved to be equally popular with beginners and experts alike.
    Based in the small and very pretty village of Arenys De Munt, which is some 45 kilometres from Barcelona itself, it took us around 50 minutes on the coastal train to arrive at the station, having passed some eye-catching sights along the miles of sunny beach!
    Although the factory is relatively close to the station, Gaspar Espiell, one of three partners in the company, was kind enough to be there waiting as our train arrived, transporting us the last couple of kilometres to the factory.
    Jets Munt SL was formed in 2003, and is a joint venture between Roca Lazaro SL (formerly known as ARMEC SL), which specialises in producing high-precision,mechanical components and who produced the parts for Artés until Artés ceased production in 2002 and Gaspar Espiell, who carries out the engine design and produces the electronics,both hardware and software. Since the most recent changes in 2009, the other two partners in the business alongside Gaspar are Xavier Sanchez and Josep Roca, whilst there are also a number of production staff.
    The origins of the company date back to 1996, when business commenced with the supply of Artés turbine components to both manufacturers and direct to self-builders,during this period thousands of parts were supplied, and at least nine turbine companies used some of these parts in their turbines.
With the formation of the Jets Munt company the first of their own design turbines was developed, although I was shown one of the much earlier engines that was originally built in 1997 to the very successful KJ66 design, and which is still running well today.
     Currently the range consists of the extremely popular VT80, Merlin 100, Merlin 140 and Merlin 160, the figures signifying the maximum thrust level in Newtons.

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参观Jets Munt工厂

Production
    With all of the staff being very welcoming we were able to look at everything that was going on, including assembly of production turbines,repairs to crash damaged engines and development, both of new engines and associated electronics.
    One fact I was surprised to learn is that all the engines have their main cases machined from a solid block of alloy, not being a pressing or by machining from a tube or casting. This method of production results in a very light yet stiff case, which is exactly what is needed to give a very stable engine with a long life,but is of course much more time-consuming and expensive!
    Another point of interest is that all the combustion chambers are manufactured from Inconel, which due to its incredible heat resistance can be thinner than the stainless steel material some other turbine manufacturers use, this use of a thinner material improving the efficiency of the engine and thus reducing its fuel consumption and weight, whilst also allowing a much longer lifetime, in fact the combustion chamber should not need replacing during the life of the engine.
    Also produced from Inconel, although this time in the form of a casting, are the turbine wheels, which are produced for Jets Munt in Germany, every batch coming with a full technical report along with individual X-ray images of every single turbine wheel.
    As the ECU’s and electronics are designed in-house along with the software, owners can be assured that their turbines will perform to their maximum, as the engines and electronics will be perfectly matched. This side-by-side development also allows improvements to be added immediately to engines in production,there is no delay waiting for an outside company to develop either the electronics hardware or software.
     As well as software development and supply of the electronics for Jets Munt turbines, the Xicoy company, which is solely owned by Gaspar, also offers the same services to other turbine manufacturers, with a number selling their turbines complete with Xicoy supplied ECU’s and software.
    This of course brings benefits to all concerned, as the increase in volume reduces the unit cost of both the hardware and software, resulting in a lower cost of a turbine package, whilst the parameters of each ECU can easily be tailored to a specific turbine design.
    Whilst talking about the electronic side of the business a new development is the production of electric retracts and controllers,at the time of writing this was restricted to the electric motor/gearbox and electronics for fitting to existing air operated retract units, but complete electric retract systems will be available soon.
     Although there was some information that was so commercially sensitive that it cannot be mentioned here, we were surprised that so much was made available to us, including the interesting fact that the end section of the turbine combustion chamber is secured in place by nothing more than some small but heavy-duty compression springs. The reason behind this being that a solid combustion chamber will come under significant thermal
stress as the engine heats up during operation,which over time can result in distortion of the chamber and poor running characteristics.
     Using spring pressure allows just enough movement between the component parts of the chamber to eliminate this thermal stress and the resulting distortion.

参观Jets Munt工厂

Every turbine is tested before dispatch, with all the parameters being monitored via this display within the test cell

参观Jets Munt工厂

Detailed performance data is listed out second by second, and is stored for later use if required

参观Jets Munt工厂

An engine set-up for testing, the exhaust is ducted out of the building to ensure that only fresh air is drawn into the intake

参观Jets Munt工厂

Just a few of the various components that are held in stock, ready to be selected as engines are being assembled

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Gaspar Espiell, our host for the visit to Jets Munt, with one of the earliest engines, built to the KJ66 design back in 1997, and which still runs well today

Looking Ahead
     On-going development is constant, one example of this being a change in the way that the kerosene start igniter is fitted into the engines, this now being simply slotted into place, which means that it can be quickly and easily replaced if necessary, even by the end user, and as only the front cover etc. needs to be removed from the engine, no re-balancing is required.
     Having said this, I have had many, many flights with the two Jets Munt turbines I own and have yet to have an igniter failure. The VT80, Merlin 100 and Merlin 140 have all now adopted the use of easily replaceable fuel and kerostart valves under the front cover of the engine, this being useful if ever unfiltered or poorly filtered fuel causes a valve to jam due to dirt build up, in that the end user can very quickly remove, clean and re-install the valves.
     A world first for Jets Munt was the use of a brushless motor on their fuel pumps, which commenced with the latest versions of their Merlin 100 and 140 turbines, and which will be rolled out across other engines in the future. Each brushless pump is run at the factory for 30 minutes to ensure totally consistent running and thus turbine performance, the use of a brushless motor ensures that there will be no variation in how the engine runs and no need to adjust any of the ECU parameters as motor parts wear-in.
    The vitally important balancing of the turbines is carried out on a very neat balancer,which uses multiple accelerometers allied to Jets Munt’s own software to precisely indicate any imbalance in the compressor, turbine main shaft or turbine wheel, whereupon fine machining takes place to obtain perfect balance. Getting this exceptionally fine balance is critical for all turbines, but none more so than the new baby Merlin 35, which as its name suggests is a 35 Newton thrust turbine that is expected to become available during spring 2014.
     Developed from an original design by John Wright, the engine has been comprehensively redeveloped to allow for volume manufacturing, so much has been changed in fact that only the turbine wheel and EGV (Exhaust Guide Vanes) are the same as John used, the engine being both shorter and lighter as well. The Merlin 35 utilises a brushless starter motor and brushless fuel pump, the fuel pump being the only ancillary item to be installed in an airframe, as the ECU and fuel/kerostart valves are incorporated under the front cover, making for a very quick and simple installation.
     Although not finalised at the time of going to print, the target is for the engine to be sold for less than 2000 Euro’s including VAT, in which case it should become a very popular turbine for small jet models.

The front section of the combustion chamber is held in place with the heavy-duty springs that are visible, this allows for expansion as the internals of the turbine heat up, avoiding thermal stress to the chamber

The kerostart igniter is simple to replace if required, importantly this does not require the turbine to be returned to the factory, or any form of rebalancing when the engine is reassembled

The very neat twin valve assembly is simple to remove should cleaning due to dirty fuel be required, or in the rare event of a valve failure.

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参观Jets Munt工厂

Engines that have come back for service are held here after the work has been completed and they have been test run, ready to be returned to their owners

Experience
     Every engine once complete is given at least three test runs in the in-house test bay,checking that the performance is fully up to specification. Occasionally, a couple of additional runs are required should an engine not be performing as it should, and it is here that the in-depth experience of the Jets Munt staff comes into its own, with only very delicate adjustments often being needed to get the engine to meet all the required parameters.
     Servicing and repairs to crash damaged engines are carried out by the same staff that assemble the turbines in the first place,ensuring the consistent high quality and repeatability needed for maximum performance and reliability.
     Whilst at the factory we saw a number of engines ready for dispatch back to their owners,it being explained that this side of the business tends to be much busier during the northern hemisphere flying season, with a significant drop off during the winter period when little flying, and thus fewer crashes, take place.
     We would like to thank Jets Munt for allowing us to visit and take a look around their facilities.

Contacts：www.jets-munt.com

参观Jets Munt工厂

The advanced balancer gives this visual indication of the exact positions on the compressor and turbine wheel where any balancing work must be carried out

参观Jets Munt工厂

Jets Munt have developed their own automatic welding machine, which is both much more accurate than manual welding, but also much quicker, keeping costs to a minimum

参观Jets Munt工厂

An engine being run in the test cell, note the very solid door, which helps reduce the noise level within the rest of the building

参观Jets Munt工厂

Jets Munt hold a number of master moulds such as these for a turbine wheel so that absolute accuracy and repeatability can be ensured

参观Jets Munt工厂

All of the turbine wheels are cast from Inconel by Würth in Germany

参观Jets Munt工厂

Every turbine wheel comes complete with its own X-ray image, as well as a full technical report,ensuring the highest quality and thus engine reliability

参观Jets Munt工厂

Just one of the large CNC machines that are used to machine parts for Jets Munt

参观Jets Munt工厂

A pair of VT80 compressors, the one on the left having been fully machined and balanced,whilst the one on the right is as supplied from the factory

参观Jets Munt工厂

Examples of new undercarriage legs, wheels and brakes being developed by Xicoy