Since the first blog post announcing the start of my adventure into the world of ham radio a couple of months have passed in which I have tried to come up with a creative solution to my main problem: I do have two QTH's and whilst the reception is great at my secondary location (OE3) reception is miserable at my primary location (OE5). Since I spend most of my time in OE5 the only solution is to go mobile.
Now this is were my other problem arises: I do only have one radio which I am carrying from QTH OE5 to the car, from the car to QTH OE5, from QTH OE5 to car to QTH OE3, ... The front panel of my Kenwood TM-D700 is not connected with the transceiver which means I have to carry a lot of sensitive equipment around everytime I move the radio. Since I am also starting to look into SOTA participation I have realised the need for a rugged setup for easily carrying around my radio. Let's begin ...
The basic chassis for the portable ham radio rig consists of CNC milled aluminium plates connected via 3D printed connectors:
The transceiver part of the Kenwood TM-D700 is mounted in the middle of the chassis:
In front a 10 mm macrolon plate is mounted to serve as a base plate for the display which is glued to the macrolon plate.
On the bottom of the chassis rubber feet are applied to prevent scratches when keeping the radio rig on smooth surfaces such as your dining room table 🙂
On the next picture you can actually see the portable ham radio rig happily sitting on the dining table:
On this picture you can clearly see that the display mount is glued to the macrolon plate. No external glue was applied since the display mount is delivered with an extremely adhesive base.
A handle was added on top to have an easy way of picking the radio up and move it somewhere else:
Side view of the complete portable ham radio rig with handle
It works terrific 🙂 Setting up ham radio in my car takes now less than half of the time previously needed. I could only further reduce that time by buying a second radio but I'd rather not amass too much different radios this early on my ham radio journey 🙂
Since the work on all the mechanical components of Schnauzer is complete the focus now shifts on the completion of the electrical parts. Since the ESCs and the power wiring is already installed the next step is the integration of the batteries into the system. Two 2-cell LiPo batteries with a capacity of 1800 mAh each are used. Those two batteries are connected in serial providing one 4-cell LiPo battery for the ESCs.
Because of the tight space situation in the robot the battery cables need to be shortened down a bit. This is done by cutting off the power cables and soldering a new EC3 female power plug to the cable. Attention: If you ever work with LiPo batteries make sure that the bared red cable touches the black cable at no point during your soldering process - otherwise sparks (in the best case) and an explosion (in the worst case) will ensue. At least one of the two cables needs to be fully insulated.
The next step was to manufacture an adapter which allows to create a single 4-cell battery from two 2-cell batteries. Such an adapter can be seen in the picture below and consists of two EC3 male power plugs. Those plugs are connected with the two batteries while the other end of the cable if connected to Schnauzer's power distribution system.
Since the frame of the robot is made out of Hardox (which makes it really tough to drill holes into it) I had to think of a new method to mount the batteries to the frame. Luckily I do have some spare strong neodymium magnets lying around from the beetleweight arena build.
Two of those neodymium magnets are placed on a rectangular piece of foam material (to provide some sort of cushioning from hard hits against the robots frame). Good old duct tape is used to mount everything together.
The next pictures shows the assembled battery completely covered in duct tape.
In the next picture you can see the two batteries mounted at the rear end of Schnauzer. Since each magnet has a holding forvce of ~ 110 N the batteries are held firmly against the Hardox frame. I am confident that they shall not come loose during a robot battle.
Last but not least a close up shot from the adapter which creates a single 4-cell battery out of the two 2-cell batteries. Also to be seen: The 80 A fuse 😉
Schnauzer is now ready to go 😉 Well nearly, I am still working on a last electronic component which should provide Schnauzer with an edge in the arena ... more details after the event 😉 Speaking of an event: The German Roboteers Assocation is holding a full contact featherweight competition on April 8th, 2017. More details here.
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 🙂
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, ...).