FAQ - Online-Shop der Fa. CAD+Modelltechnik Jung

CAD+Modelltechnik Jung
Go to content
Some recurring questions are compiled in this list
Topic model engines
(the topics model helicopter and CNC milling machine can be found below)
How many pieces can the model motors be manufactured? Is it possible to manufacture in small series etc.?

Sometimes we receive inquiries from private individuals / companies whether it is possible to manufacture the model engines in small series or in larger numbers according to our construction plans? All drawings for the enignes shown are the intellectual property of "CAD + Modelltechnik Jung". Manufacturing in large quantities is generally prohibited without consulting "CAD + Modelltechnik Jung". Larger quantities mean the production of more than 3 motors of the same type on CNC manufacturing machines. If you are planning larger production lots, please contact us or send us an email to cad-modelltechnik-jung@web.de. We will then find a solution together!
We also hereby reiterate that duplication of the construction plans is expressly prohibited (copyright). You need e.g. larger quantities of the construction plans for training courses, apprenticeships etc. please contact us. For larger quantities, you will of course receive a corresponding discount.
What is the principle behind the motors shown?

All the engines shown work according to the 4-stroke process and have valves for gas control that are controlled via camshafts (or cam drums). Model engine fuel is drawn in with the air via a carburetor (Otto engine principle). In contrast to the petrol engines like those installed in cars, "normal" model engines do not have a high-voltage ignition system. Rather, the ignition process is initiated by a glow plug, which is once heated to the glow temperature by a battery and continues to glow by catalytic reaction after the engine is started. This means that after starting and running the engine independently, the voltage source can be removed. The advantage is the simple ignition system which, in addition to the actual glow plug, only consists of a 1.5 V battery and a plug system. It is disadvantageous that the ignition timing, which is not precisely defined thereby, theoretically costs power. The ignition timing is rather determined by the choice of glow plug, compression ratio and choice of spray composition.
Nonetheless, very high liter outputs are possible with model engines, which can only be achieved by normal car engines with great design effort. Therefore, please also observe the safety instructions when operating the fashion motors in our construction plans!
What fuel do the engines run on?

Model engine fuel is used as fuel, i.e. a mixture of methanol, oil and possibly small amounts of nitromethane. Due to the design, the amount of oil in the engines shown can be reduced to 7-10% by volume (the normal model engine fuel has about 16-17% oil). If the fuel is mixed itself, additive synthetic oil (polyglycol oil) must be used as the oil. Model motor fuel with castor oil may only be used to run in the motors. The polyglycol oil is a special oil and has nothing to do with the motor oil in our cars, as it is not miscible with methanol. The addition of nitromethane results in better ignition behavior with a low admixture and thus a lower adjustable idling speed. Higher admixtures result in an increase in performance.
Methanol and especially nitromethane are highly toxic and may only be stored in special containers. Model motor fuel does not belong in the hands of children and may only be stored and traded in well-ventilated rooms.
The Rossi No. 02 have proven themselves as glow plugs. These are much cheaper than the special 4-stroke glow plugs and still show better results with low idling and throttle response of the engines. And without additional annealing!
What is the ignition principle of the engines? Is gasoline operation possible with spark plugs?

All engines work with standard glow plugs (model building trade) and model engine fuel (see note on this above).
Operation with spark plugs and normal petrol station petrol is possible in principle. However, it has the disadvantage that the motors run hotter due to the principle. It is therefore important to ensure that the engine is properly cooled during operation. With the engines shown so far, there is only some experience with gasoline operation, see also information in the gallery.
Suitable ignition systems can be ordered from the following provider: https://www.justengines.co.uk/
In general, a gasoline operation is associated with the use of a pump carburetor (e.g. Walbro carburetor). However, this is only possible with the model engines presented here if the gasoline supply is ensured by means of an additional petrol pump (with return). The background is that these pump carburettors are controlled via the pulsating over / under pressure in the crankcase. However, this is not possible with the multi-cylinder engines shown here.
Suitable Walbro carburettors can also be found on the aforementioned website.
Which machines are needed for metal processing?

In addition to a lathe, a simple milling machine or a milling attachment for the lathe is required. Some motors require a 4-jaw chuck and / or clamping plate for the lathe.
A grinding device is required to manufacture the camshafts / cam drums. Various designs are found in the literature. Alternatively, you can grind the cam base circle with a simple grinding device and then work out the cams with a file.
The camshaft or cam drums must be hardened. If you have no way of doing this, you can certainly have the parts hardened accordingly at a metalworking company. Subsequent grinding of the parts is not necessary. Apart from some small parts, no other parts need to be hardened. (i.e. no hardening required when manufacturing the crankshafts. Exception: 1-cylinder four-stroke engine). The small parts are hardened with the gas burner and the components are then quenched in oil.
What documents consist of the construction plan shown?

In addition to the individual part drawings for each component to be manufactured, Assembly drawings, sectional drawings and exploded drawings included. A multi-page construction manual with the most important processing steps, a parts list and proof of delivery complete the plans. All drawings are in A4 format. Large-format A4 color prints complete the construction plans. Please refer to the individual construction plans for the page size of the plans (approx. 45 to 75 pages, depending on the construction plan).
The individual part drawings show the components in a 3-side view and in an isometric view. You can download sample drawings from the respective motors.

The matching carburettors are not shown in the construction plans. It is not possible to manufacture the very difficult carburettor yourself. These can be obtained from the model dealer or used on Ebay. When buying, make sure that it is a 2-needle carburetor for a two-stroke model engine, in which the idle and full throttle range can be set separately. Concerning. In terms of size, a carburetor is used that is approx. 1/3 smaller than that intended for the individual displacement. I.e. a carburetor for a 10cc two-stroke fits a 15cc four-stroke. For the offered engines with an individual displacement of 15 - 20 ccm per cylinder, e.g. following carburettors are used:

Especially with the 9-cylinder radial engine it can make sense to use the next larger carburettor, since here only one carburetor is used, contrary to the large-volume boxer and V-engines from our range of construction plans:

Are material kits also offered?

So far, no material kits are offered. If there is a corresponding demand, these can be offered in the future. Consisting of all raw materials and all necessary standard parts such as the rolling bearings, screws, etc.
Are the blueprints also in data form? What types of data are possible?

Upon request, 2D drawing files and 3D component files of the individual parts can also be provided in various data formats.
Converted 2D data formats such as B. * .dwg and * .dxf.
In addition, converted 3D data formats such as * .step, * .dgn and * .igs can be obtained (other formats on request).
We send the data as a download link. Other data carriers on request.
The actual 3D construction files or assembly files cannot be purchased.
Topic CNC milling machine
General questions about the CNC milling machine

See detailed description for the CNC milling machine
Topic RC-helicopter
What is the advantage of the coaxial rotor system? Is this why the system is easier to fly than conventional model helicopters?

This special type of model helicopter was therefore designed to come as close as possible to the original from Kamov Ka-52 etc. It is no exaggeration to say that one of the most remarkable and extraordinary models in the world was created. This is confirmed by dozens of emails addressed to us as well as forum entries in the Internet forums. In addition to the size of the model with a 2.4 m rotor diameter, the precise manufacture of the individual parts of the complex rotor system in semi-scale design and the coherent overall concept are emphasized. Despite its size, the model is very agile, fast and agile to fly. Light aerobatics is also possible. This aircraft is generally not suitable for complex aerobatics and 3D flight figures.
Rather, it must be said that the coaxial rotor helicopter presented here is no easier to fly than a commercially available model helicopter in the main and tail rotor configuration with a stabilized 2-blade head. This fact is due to the fact that this coaxial rotor helicopter has non-stabilized rotor heads (corresponding to the original). Rather, this coaxial rotor helicopter flies just like any other model helicopter with unstabilized multi-blade heads.
The actual advantages of the coaxial rotor system, such as maximum performance and thus the max. Specific lifting capacity with the same rotor diameter as a standard model with main and tail rotor is still fully given. The total efficiency loss of up to 20% of a tail rotor can be fully implemented in the two main rotors. Likewise, the non-existent tail rotor has good hover characteristics since there is no lateral drift due to the non-existent tail rotor (see also report in the magazine "ROTOR", edition 1, 2008, "Technology and function of coaxial rotors" by author Gunter Winkle.
Because of its size alone, it cannot be compared with the small and smallest cheap coaxial rotor model helicopters made in Asia. These are mostly only to be used as indoor models and are very easy to fly due to their extremely stabilized rotor system.
The coaxial rotor model helicopters with turbine or gasoline engine drive offered here are rather a highly specialized high-tech aircraft that can only be flown by an experienced and prudent model pilot. Appropriate experience in operating model helicopters with unstablized rotor heads and experience in operating turbines should also be available. In the hands of an experienced model pilot, this model can take full advantage of its special flight image.
Are special receiver-side or transmitter-side mixers required for the coaxial rotor helicopter?

In contrast to the tandem screwdriver etc. on the market, this receiver does not require mixer electronics on the coaxial rotor helicopter.
Only standard mixers are used on the transmitter side. It is important, however, that the transmitter has the "virtual swashplate rotation" function. As is usual with multi-blade heads, this ensures that the linkage rods run in a straight line from the lower swashplate to the blade holders of the lower rotor head. It is not possible to operate the helicopter without this function.
Reprint only with the permission of the author. All statements without guarantee.
Back to content