Beetleweight Arena Part 1

Those who are long term readers of this blog might have noticed, that I have not competed in any (combat) robotics competitions lately. This is largely due to the fact that in 2016 NO german events have taken place. This in turn is the result of the usual event location being unavailable due to restoration works. There was only one bigger competition which took place within the FACTS faire in Gent / Belgium. Sadly, the very large distance prevented me from participating in that event. Even competing at the biannual Mad Metal Machines comes along with a total of 1600 km car travel and 3 to 4 days (1 day driving there, 2 days competition, 1 day driving back) of time invested. Since there are no competitions available closer to Austria so far I was left with no choice. However, this precondition is subject to change. Without further ado let me introduce the prototype of our new beetleweight arena (well, the CAD Mockup at least 🙂 ):

As the name already suggests the arena is intended to be used with the newly established beetleweight class (1.5 kg). The main reason behind the decision for the beetleweight class was that antweights due to the weight limit of 150 g are very small and present considerable challenges for the new builder. However, raptor weights (6 kg) require already a considerably strong arena, since they are capable of quite some destructive power. Furthermore, the availability of commodity parts which can be easily reused in beetleweight builds provide a considerate cost advantage to bigger combat robot weightclasses. Also the establishment of high power spinners make Hardox (or any other steel which properties are similar to those of Hardox) armour a must-have for (raptor)/featherweight robots. This requires the ability to manipulate and process though steel types which exclude many of the aspiring robot builders.

Since I have spent quite a few words on the reasons behind choosing beetleweight as a suitable weight class it is now time to elaborate a bit on the arena. The arena is comprised of individual blocks which hold together by means of strong neodymium magnets. This concepts allow a fast and easy "plug-n-play" assembly of the arena while still providing a strong connection. The arena floor consists of 10 mm thick transparent polycarbonat - the colour is provided by paper mounted between the polycarbonat plate and the frame of the block. The dimensions of one individual block are 270 x 270 x 180 mm.

The prototype built to demonstrate the concept consists of 3 x 3 = 9 individual blocks and has a size of 0.81 x 0.81 m. The final arena should consist of 7 x 7 = 49 blocks which leads to an arena size of 1.89 x 1.89 m 🙂 . The current prototype consists only of so called passive blocks. A passive block is a block which just provides a piece of arena floor. There shall also be active blocks which provide arena hazard functionality to the arena such as automatically rising spikes, flippers, saws, turntables, ...

Since building such an modular arena comes with quite a bit of expense we are currently looking for sponsors helping us in our adventure 🙂 If you, dear reader, are someone who could imagine contributing to such a project or works for a company who might be able to help us please do not be shy to contact me at office AT 🙂


Featherweight Schnauzer Part 19

Although the last update on Schnauzer has been posted just a little while ago I am happy to announce yet another update about Schnauzer's progress. Some free days due to the public holiday on 8th of December (Immaculate Conception) have provided me with a much needed break which in turn allowed me to finalize the top plate including the device toothed belt tightening device. For reference the next picture displays Schnauzer before the start of the operation.

As one can see from the next picture, the toothed belt on the right side is very loose and can be pressed down by applying a little force with the trigger finger.

Since I can not keep my finger there while running the bot (what a silly idea indeed 🙂 ) the toothed belt must be tightened in another way. Here the toothed belt tightener described in the last blog post appears on the scene. On the next picture you can already see the tightener mounted to the top plate.

After mounting the top plate to the robot it can be seen that the tooth belt tightener fulfils its purpose and creates the necessary tension which prevents the toothed belt from getting loose from the cogged-belt pulleys in case of rapid load changes.

Here you can see a picture of the whole robot with the top plate mounted. Currently only battery and receiver are missing, otherwise the robot is fully functional. (About time - Redesign/Repairs are going on since the last Mad-Metal-Machines Event in Fall 2015).

A glance at the undercarriage of Schnauzer reveals that all screws are countersunk. This is a lesson learned from the very first version of Schnauzer where the screw heads kept getting stuck in small gaps between two consecutive arena floor sheets.

Next steps are finalizing the robot by selecting and purchasing a suitable battery and installing remote control equipment. Stay tuned 🙂


Featherweight Schnauzer Part 18

Quite a lot of time has past since the last update about the status of my featherweight combat robot Schnauzer but finally there is some progress to report. Building a combat robot one can clearly observe Pareto's Law in action. Parato's Law simply states, that 80 % of the result can be achieved with 20 % of the effort. However, the flip side of this rule implies that finalising a project (doing the last 20 % of the work) will consume 80 % of the effort. And with a combat robot, you do want to go for the 100 % solution because everything else might leave you with a pile of rubbish in the arena. That being said I'd like to switch to the main purpose of this post which is to describe the latest updates on Schnauzer.

In the new version of Schnauzer only its rear wheels are directly powered by electric motors. The front wheels are powered by toothed belt which transmits the power from the rear wheels via an cogged-belt pulley(s) and tooth belt to the front wheels. This can clearly be seen in the next picture which displays the drivetrain of the left side of the robot.


In the picture above the considerate reader might have observed some shiny things at 1/3 and 2/3 of the lower tooth belt. Those are DIY deflection sheaves built from ball bearings. Their purpose is to lift the tooth belt up and over an angle bracket which is connecting the base plate with the hardox (side and front) armour.


Unfortunately the purchased tooth belt was a bit too long and therefore is not sitting tense enough on the two cogged-belt pulleys. Loss of traction in the heat of combat might be result. In order to circumvent this the design of a tooth belt tightener was necessary. The tightener was designed utilzing Autodesk Fusion 360 which is a very powerful tool and also has a startup license 🙂 Here is the finished design:


Upon completion of the design process I called up my reliable supporter of 3D prints and sent the design files to him. On the next picture you can see the printed belt tightener (well the part that is printable at least).


The next step was to insert the belt guide (which will later on press against the tooth belt) which consists of two ball bearings plus three washers. The tooth belt tightener is supposed to be mounted on the top plate of the robot facing downwards. When the top plate is closed and firmly connected with the rest of the robot the belt tightener should press against the tooth belt and  eliminate any belt play.


Next up: Integration with Schnauzer and finalizing the top plate (need holes for screws, removable link, ...).


Dornier Museum Friedrichshafen Part 2

In my last blog article I was discussing the Dornier Museum in Friedrichshafen, with the main focus on the VTOL transport jet plane Dornier Do31. However, the museum contains many other interesting exhibits which I would like to share with you.

Dornier Do B Merkur: This plane was designed as a passenger plane which could pack up to 8 passengers plus a crew of 2. A BMW V1 engine with 680 PS allowed for an maximum airspeed of 175 km/h. The Dornier Merkur had a range of up to 1000 km. Its virgin flight took place on February 10th, 1925.


Dornier Do J Wal: The Dornier Wal was the most successful flying boat developed by Dornier. More than 250 pieces of this machine were built whose prototype Dornier Do Gs I virgin flight took place on July 31st, 1919. Two six zylinder Maybach Mb IVa engines with 260 PS each were used in the  Dornier Do Gs I to power two propellers with a diameter of 3 m.


Due the treaty of Versailles and because the airplane had a advanced concept the allied forces demanded extradiction of the plane. In order to avoid handing over the plane it was sunk in the Baltic Sea on April 25th, 1920. To circumvent further problems with the treaty a construction office in Italy (Marina di Pisa) was founded were the successor Dornier Do J Wal was developed.


Interesting fact: On May 21st, 1925 the polar researcher Roald Amundsen started with two Dornier Wal planes from Spitzbergen towards north pole. On plane had to perform an emergency landing due to motor problems. The other plane was landing too and suffered severe damage. The researchers repaired the first plane (and a runway, which took them 3 weeks) and managed to fly out to the north coast of Spitzbergen where they were rescued by a sealer ship.


Dornier Do 28 Skyservant: The Do 28 was a reliable dual-engine plane mainly used by the german armed forces and possesed STOL capabilities. During the whole 20 years time of service within the german military only 3 planes (out of 121) were lost.


Dornier Do 29: The Dornier 29 was developed during the 1950s as an experimental platform for testing a tilting-propeller system for STOL aircrafts.


Two planes of the Do 29 were built and the virgin flight of the first prototype took place on December 12th 1958.


During testing the new aircraft concept with two tiltable pusher propellers proved highly successful and allowed for a stall speed of only 24 km/h.


Despite this great success the aircraft was not pursued further at the end of the flight test program.


Only one of the two Do 29 prototypes survived the program and is now exhibited at the Dornier museum in Friedrichshafen.


Alpha Jet: The Alpha Jet was the result of a cooperation of the Dassault Aviation (France) and Dornier. The plane was intended as a light attack jet and advanced trainer aircraft. A total of 480 planes were built and the plane was used in the air force of several countries e.g. French Air Force, Belgian Air Component, Cameroon Air Force, Royal Thai Air Force, Portugese Air Force.


Dornier Do33 KAD: The Do33 KAD was developed as a reconnaisance drone which could penetrate up to 150 km of enemy territory while flying at Mach 0,85.


Various sensor payloads could be used with the drone such as an optical camera, a infrared line scanner and a high resolution side-looking-airborne radar.


Dornier Do 34: The Dornier Do 34 Kiebitz was designed as an unmanned military reconnaissance drone.


Dornier Zieldarstellungsdrohne: The drones pictured below served to simulate a target for interceptor planes and anti-aircraft artillery.


The drone is powered by a gasoline engine and resembles modern drone designs quite eerily.


Bachem Ba349 "Natter": The Bachem 349 was a world war II german rocket powered interceptor which was designed to prevent the devastating bomber attacks of the allied forces against german industrial plants. To my best of knowledge it has no connection with Dornier and the reason behind its exhibition in the Dornier museum remain a mystery to me. However, it was great to see this very unconventional plane whose design reflect the desparate situation of the german army by the end of world war II.


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