Sketch Bot Project Update

I am in the very beginning stages of design so there are still a lot of things that can change. I started with the initial physical design of the Bot. So, pieces such as the base, linkages, and the motor extensions are being drafted in Solidworks. After much thought the base of the Sketch Bot is going to be redesigned for more support and stability. The linkages of the Sketch Bot will uphold the original design that we have. It is imperative that the linkages of the Bot are a light-weight design. This helps with the mechanical stress that the motor would have to endure. The theory is that the less mechanical stress the servos must endure, the more accurate the drawing or picture will be.

Project Summary

The Sketch Bot would be able to draw any image that would be uploaded to Microsoft Paint. The Bot would be controlled via arduino, and the arduino would be coded with an algorithm that would be able to read the paint file of the user’s choice. All of the physical components of the Bot would be made out of PLA plastic that would be made by a 3D printer. Arduino programming and Matlab would be used to construct the code for the algorithm to be uploaded to the arduino unit. A long term goal for the Sketch Bot would be able to draw any image on different surfaces.

Project Outline

1. Drawing and Design

2. Wiring and Electronics

3. 3D Print Assembly

4. Create Moving Model

4. MATLAB Code and Arduino

5. Perform Final Tests

Project Materials

Arduino Uno
Servos (3)
MATLAB Code Transfer Tool (Arduino)

Project References

Operating Voltage: 4.8- 6.0VDC
Operating Speed: 0.20sec/60degree (4.8V), 0.16sec/60degree (6.0V)
Stall Torque: 5.3kg*cm (4.8V), 7kg*cm (6.0V)
Temperature Range: -20°C ~60°C
Dead Band Width: 4ms
Servo Deluxe HD Ball Bearing Servo Motor


Up-Cycled Weather Vane: Final Thoughts

Build was successful in that it rotates smoothly in the x and y and is visually playful. I like how the bicycle parts look covered in vinyl. The "flower" stem and  face came out as envisioned
rolling resistance was adequately low but could be lowered further. I think I want to build some wheel having investigated this topic as part of the project and as a commuter cyclist who always wants to go faster.


I need to rethink blades to better capture wind. The vinyl on spokes approach is better than the saran wrap I tried but hardly a resounding success. Comments bellow on other approaches would be appreciated. Current improvement that occurs to me is tacking  pre cut blades sheet metal to the spokes.

The weld fit up /tacking was challenging. If I were to repeat might jig. Might notch where I cut off fork tine to improve fit.

Finish of vinyl was good but could have been perhaps better. I had never applied vinyl before and getting it to stick to curved/uneven surfaces was very challenging. I didn’t mind that there was some cracking/bubble lines but probably not the cleanest aesthetic. Might sandblast and powder coat next time to create a more even finish.

Overall was fun and interesting getting used parts and turning into a budding piece of sculpture for a new sculpture artist. Hope you enjoyed!


Up-Cycled Weather Vane: Pt. 2

Build was originally envisioned with sketches and dimensions. I based the height off of sculptures I had seen in the sculpture park on Mccormick ave in Skokie IL.
Parts were cut and fit was adequate so that parts could be welded square to each other.
Testing of functionality for spinning of wheel and of fork so it could move freely with wind. I used a box fan to test ease of spin. This testing led to additional functionality of leaf tail to fork.






This leaf was added so as to be more stable in wind (built from tin snipped half of the bicycle chain guard). Bearings were swapped to lower rolling resistance. I am glad the frame I used was a very solid steel Schwinn frame as the gauge of the walls on all of the parts was nice and heavy limiting heat warp and allowing for beefy welds.

*fun fact Chicago was once known as the bicycle capital of the world in part because of the manufacture of Schwinn bicycles in the city*

Finish was determined and installed (green vinyl with blue accents to give a flower like appearance of  (I like forget me nots and will likely color the hub yellow in the future). The green vinyl was a fun pickup. I thought about going with something more natural but decided for a more distinct color combination. I initially tried to use saran wrap for the blades on the spokes but then went with sections of vinyl. I applied all of the vinyl in sections to make it easier to apply. This was much less time consuming than painting. All parts had been previously cleaned for welding so prep was fairly minimal except for cleaning the welds and heat affected zone/additional spatter.









Possible improvements to wind blades/petals in future to improve wind capture. Perhaps swap hub and steerer tube bearings in future.Site of install to be determined.

Up-Cycled Weather Vane: Part 1

I chose dimensions based on the bicycle fork I used and wheel as well as a 4ish foot section of gray tube I had. I planned on this being a outdoor sculpture rather than a rooftop piece so I wanted something human height.  The final build comes in around 6 ft.

All of the parts being used was both a blessing and a curse. The wheel hub was in ok shape but the bearings were a bit pitted (nicked so as to no longer able to roll smooth). I hope to replace with ceramic bearings/races in the future both because they have low rolling resistance and because they are less susceptible to the elements. Rolling resistance for those who don’t know is the friction the bearings (little balls in the races (the holders that spin: experience when rotating. Less rolling resistance means less force needed to move/spin the thing with bearings  ( Cyclists spend a lot of money on reducing rolling resistance. Getting awesome bearings with low rolling resistance is one of the easiest ways of buying speed for a racing bike.

Build initially was cutting and fitting  the bike fork pieces to the tube pieces. I cut off one of the bike fork tines because it was impeding the spinning of the wheel.



This was because the crashed wheel was very very out of tru (no longer consistently round).  Initially I thought I would just weld the steerer tube to the long section of tube but this proved impossible as it would have impeded the rotation of the fork.


I then went with the second option of mounting to steerer tube face where the fork tine had attached. I grinded surfaces of fork /prepped for welding.

Initial fit up test showed that there was some overlap with moving parts so I ground down.


I then fitted scrap flat stock to seal openings so as to limit water getting into steerer tube and for aesthetic completeness. I mig welded the different elements after marking and clamping.


Welds were adequate but hardly structural. Mig welding can sometimes be used like a hot glue gun for metal. If you prep the two surfaces so there aren’t contaminants like paint and oil you can get things to join nicely with the heat/introduction of new metal.

As you can see the outer race is no longer gnarled.

Welds had nice heat affected zones.

Afterwards I ground welds to create a more aesthetic appearance.



Up-Cycled Weather Vane: Introduction

Up-Cycled Weather Vane

My name is Joseph Prosnitz and I am undertaking a Weather Vane Build as a Bocca Bearings project

There is a long history of weather vanes as you can read about on wikipedia

*Fun fact they are often called weather cocks because they are in the shape of a rooster on top of churches.*


These wind measuring devices are both ornamental and indicate the general direction of wind. I have always liked that they catch the eye on a windy day. This will be my first build of one. I researched how they are traditionally constructed and discovered they are fairly simple. I decided to reuse a bicycle I had lying in the shop as it had been crashed. The greatest difficulties I foresee are the weight considerations as a vane that is too heavy won’t track the wind at low speeds. I hope to offset this by minimizing rolling resistance. More on this later.

My goals for this project :

1. build a weather vein
2. up-cycle a used bike
3. create a piece of outdoor art
4. experiment with bearings

Primary tools used: 

angle grinder

bench grinder

mig welder (you don’t need a spool gun like the one pictured)
welding table
bench vice

Parts: used bicycle wheel


used bicycle fork
bicycle races 

metal tube

Scrap metal


Pi Zero Drone: Part 9

Quad Post #9: Calibrating ESC Manually
Each of the ESCs (Electronic Speed Controllers) on the quadcopter has to be calibrated to the RC transmitter signal so that the full range can be read on the quadcopter. To start the calibration procedure first ensure the following steps are done prior to ESC calibration
  •     Bind RC transmitter to receiver and calibrate the transmitter using the steps from blog post #8.
  •       Disconnect ALL propellers from the quadcopter.
  •       Disconnect any external power source i.e. USB cables from computer and Li-Po battery.

    This method of ESC calibration is referred as the “All At Once” method. Here are the steps:
  1.       Turn transmitter on, and set the throttle to maximum.
  2.       Plug in Li-Po battery.
  3.      Wait for the 3 signal LEDs on the PXFmini to start light up in sequence
  4.      Once the LEDs illuminate, disconnect the battery. (Keep throttle at maximum!)     
                     The ESCs are now in calibration mode

            5 .       Reconnect the battery and wait for LEDs to light up in sequence and buzzer will sound.
            6.   Once buzzer and LEDs light up in sequence, move the throttle to minimum
            7.   You now have full control of the motors with new ESC calibration. 

Pi Zero Drone: Part 8

Pi Zero Drone Post 8: On board Instrument Calibration
From the on screen response to tuning PID controllers, APM Planner 2.0 software can give a newbie quad user (myself) a deep understanding of what it takes to control this quadcopter. The software is capable of display real time response of the IMU, RC controller and other instruments you wish to fly with. This post aims to give a brief introduction and how to calibrate your instruments while I wait for new ESC to come in from Amazon.
The APM Planner 2.0 has a very interactive GUI that can be used for multiple vehicle types. A full in depth tutorial of the software can be found on First step is to download the software onto your computer and follow the instructions on the screen. To connect to the quadcopter, first plug in the battery and wait for the buzzer to sound. This time you can connect to your quadcopter using the 5 GHz Wi-Fi signal.

Steps to configure the Wi-Fi signal can be found in blog post # 6.

After you have connected, the on screen altitude indicator (Very similar to one on an airplane) should start responding to the onboard IMU. Now the calibration can begin. In the APM Mission 2.0 tool bar select ‘Initial Setup’ >> Mandatory Setup. From here you can pick the frame type, this drone uses the first X-style frame type.

Select Compass to start the calibration. The Compass will need a live calibration by rotation the quadcopter in the air slowly around all axis (front, back, left, right, top and bottom). This will be done for 1 minute. Calibration offset will be created and stored for future missions.  

Selected Accel Calibration and the calibration wizard window will appear. Be sure to have the quadcopter on a flat surface and select Calibrate Accelerometer and follow the prompts on the screen. It is important not to move the copter immediately after pressing continue for each process, this may lead to skewed stored parameters.

Radio Calibration
Remove all propellers and bind the RC transmitter to the receiver.
Select Radio Calibration and start the calibration by pressing the Calibrate button. Move the sticks and switches to the maximum positions. When you feel that all the movements are correct, press End Calibration and the offsets will be stored for that radio controller.
Attach “RC_Calibration.jpg” here
Flight Modes
This setting can be used to assign switches on your transmitter to modes like loiter or stabilize. You can set your own settings based on what you wish your quadcopter to do.