Introduction: RufRobot45

RufRobot45 was built to apply silicon/caulk on a difficult to access 45° pitched roof


Rainwater leaking through a cracked wall in our house caused damage to the paint and the wall, which worsens after heavy rain. After an investigation, I was able to see a gap of 1 to 1.5 cm (around ½ an inch) gap for the length of a section of the roof of 3M/9.8 feet. This space channeled rainwater from the 45° (pitch roof 12/12) roof onto a side panel and down through the cracked wall. See Image 1 below.

I called a few roofers/leakage experts, to get their advice and to assess the cost. The overall cost to repair/stop the leak would be a minimum of $ 1200. The quotes included charges for rigging ropes, safety anchors, and insurance to cover the roofer while they inspected and fixed the leak on the difficult to access steep 45°roof.

The estimated cost of $1200 for something as simple as applying Silicone/Caulk of a $20 tube, it was too high, however when you are desperate you would pay the amount to stop the ongoing damage.

Before accepting any of the quotes, I decided to use free time during the Covid 19 lockdown to attempt repair, first of all, I had to inspect the roof to see if it's going to be a feasible repair I can do on my own.

Inspection Robot

For the risky inspection, a tether attached RC tank volunteered to go on the steep roof. The RC tank (Image 2) is a prototype for the final design. Built from old Vex robotic parts ( image 3) I had lying around. Vex 393 motors, tank tread tracks, RC controller, and PVC tubes for the chassis to inspect the roof.

Although this Instructable is not about the inspection robot, I have included an image for those who are interested. Through images from the GoPro a long gap is visible where water could flow towards the sidewall. see image 1.

Automated caulking gun design process

This design process could be applied to silicon, glue, or another type of Caulking application that is applied through a tube and nozzle. Then you need a caulking gun, a simple metal frame to hold the tube and a plunger, a spring to apply pressure, a frame around the tube, then hold the caulking gun and position the tube nozzle against the gap.

Place the nozzle upwards, downwards, rightwards, forwards backward (axis X, Y, Z) to follow the contour and angle of the gap. Knowing all this makes it easier to decide what a caulking robot would have to do. The process was iterative, after many trials, trials, and errors, I was able to completely cover the gap and stop the leak.

To better illustrate a design process that others can reproduce I modeled, animated, and rendered the robot images with Blender 3D. Faster rendering was possible by choosing Nvidia Cuda and a 1080TI GPU instead of the CPU on my old system. The following are the steps in the construction of the robot.


Vex parts for step 1

  • 1x Rail 2x1x25 1x 12" Long Linear Slide Track (for plunger).
  • 1 x linear Slider outer track
  • 4 x Rack Gear sections
  • 2 x Angle Gusset
  • 1 x Vex 393 2 wire Motor and 1 x Motor controller 29
  • 1 x 60 tooth High Strength Gear (2.58 inch diameter)
  • 1 x 12 tooth metal gear 3 x Shaft collar
  • 1 x Rack Gearbox Bracket
  • 2 x High Strength 2 inch shaft
  • 3 x Bearing Flat (Cut one of them into 3 pieces and use them as spacers)
  • 2 x Plus Gusset 3 x .5 inch Nylon Spacers
  • 1 x .375 inch Nylon spacer Non Vex parts
  • 2 x 4 inch hose clamp( to keep tube in place).

Vex parts for step 2

  • 2 x Angle 2x2x15
  • 1 x Vex 393 2 wire Motor and 1 x Motor controller 29
  • 1 x Worm Bracket 4 Hole
  • 1 x 12 tooth metal gear
  • 1 x 36 tooth gear
  • 2 x High Strength 2 inch shaft
  • 2 x Shaft collar
  • 1 x 12" Long Linear Slide Track
  • 3 x Rack Gear sections
  • 1 x Linear Sider inner truck
  • 2 x Bearing Flat

Vex parts for step 3

  • 1 x steel plate
  • 5x15 ( Cut with metal snip or hacksaw to 3.5 x 2.5 inches) This will be the base for the silicon tube assembly.
  • 1 x Vex 393 2 wire Motor and 1 x Motor controller 29
  • 1 x 60 tooth High Strength Gear (2.58 inch diameter)
  • 1 x 12 tooth metal gear
  • 4 x Shaft collar
  • 1 x WormBracket 4 hole
  • 2 x High Strength 2 inch shaft
  • 4 x Bearing Flat
  • 2 x 2 inch standoff
  • 1 x Angle gusset
  • 1 x .5 inch Nylon Spacers

Vex parts for step 4

  • 1 x Vex 393 -2 wire Motor and
  • 1 x Motor controller 29
  • 1 x 60 tooth High Strength Gear (2.58 inch diameter) Rendered imagesshow a 36 tooth gear for step 4, after some testing, this was replaced with a 60 tooth gear to provide more torque needed to push the weight of the silicon tube mechanism up the 45˚ incline.

  • 1 x 12 tooth metal gear
  • 4 x Shaft collar
  • 1 x Rack Gearbox Bracket
  • 2 x High Strength 2 inch shaft
  • 3 x Bearing Flat (Cut one of them into 3 pieces and use them as spacers)
  • 2 x Plus Gusset
  • 7 x .5 inch Nylon Spacers
  • 2 x Angle 2x2x25 Hole
  • 4 x 1 inch standoffs
  • 1x 17.5" Long Linear Slide Track
  • 2 x linear Slider outer track
  • 5 x Rack Gear sections
  • 1 x Steel C-Channel
  • 2x1x35 or Steel C-Channel
  • 1x5x1x25 (depends on the length of the track). This C-Channel is attached on the edge side of the track closer to the silicon tube. It supports the weight of the tube mechanism. Otherwise, the track will tilt out of the plastic linear slider.

Vex parts for step 5

  • 2 x Vex 393 2 wire Motor and 1 x Motor controller 29
  • 2 x 3" High Strength Shaft
  • 6 x Bearing Flat
  • 2 x Rail 2 x 1 x 16
  • 2 x Rail 2 x 1 x 25
  • 8 x Shaft collar
  • 1 x Tank tread kit
  • 4 x 1 inch stand offs
  • 1 x Vex Pic Controller

I used the Vex AA 6 battery holder for the PIC controller that provided enough voltage and current during
the build-out process, however, I found that the AA battery pack could not provide the current to power 6 x motors 393 especially when the torque is required to force the plunger into the silicon tube. To provide appropriate power I connected two 18650GA NCR batteries (3500mAh each) in series to provide ~8volts, with 2 additional batteries wired in parallel for increased current. With this battery setup I have plenty of current to operate the robot covering 3 m of caulking. I also used an 18650 4 x battery holder as shown in image 14.

Step 1: Motorize the Caulking Process

The first step to confirm vex parts would be enough to replicate the function of a caulking gun without using the existing

caulking gun which would be heavier and more complicated to automate. The design includes a vex linear motion kit, 393 motor and various parts to build an actuator of sorts that could push silicon out remotely with the RC controller. I used the high strength 36 tooth gear to add more torque which is needed to push the plunger in the silicon tube with more force. Image of the design is below and the vex parts used are listed below.

Step 2: Build Forward Backwards Mechanics

Now that the plunger mechanism works, we can add the mechanism to control the silicon tube position with the plunger forward and backwards, this will help compensate for the limited movement of the tank robot on the steep roof.

Step 3: Build Up or Down Assembly

In this step we build the mechanism to move the plunger platform up and down which now includes the weight of the silicon tube, two vex motors two linear motion kits one for the plunger the other for the forward, backward motion and other associated parts basically components in step 1 and step 2.

Step 4: Bu Left and Right Mechanics

The tank bot covers 3m/9.8feet on the pitched roof, moving the silicon tube down to inject the silicon up to scrape the silicon. The plastic tank treads have no limited traction on the 45˚ incline they provide enough control to position the tank slightly left or right. Moving the tank up and down the roof is possible by a retractable tether (a lockable dog leash).

Once the tank is positioned in place the silicon tube mechanism can slide on a 30cm/12 inch track that is built into the tank. This means the bot can cover 30cm of caulking at a time before moving the tank via tether to caulk a new area and so on.

Step 5: ​Build Tank Base With Controller Electronics

I used a tank base because vs wheeled because it provided a stable platform with a possibility of some traction, while the plastic treads have poor traction its enough for the current design. Parts for

Step 6: Step 6: Attach and Connect the Tube Platform to Tank Base

The tube platform is then attached to the edge of the tank, the edge position provides the best clearance from the tank tracks and reachability for the silicon tube. adding ballast or any heavy metal object at the opposite side to the tube platform will provide the counter balance to keep the both tank tracks firmly grounded.

Step 7: ​Connect Motors to PIC Controller, Fine Tune RC Controller

In Image 14 the 6 motors are connected to the IO ports on the Pic controller in the Lock&Lock container. Each IO port is mapped to a channel in the transmitter. For the motors that require finer control like the horizontal slider motor as in step 4 and the Left right tank tread motors.

A GoPro is attached and positioned on the tube assembly pointing at the nozzle. The camera is there mainly to record the process, and to provide a Point of View back to my iPhone, although I ended up not using the POV capability, it was easier to physically sit at edge of the roof so I could see and control what the robot was doing.

This project can be replicated using Adruino or other microcontroller, and appropriate WIFI or radio remote controller. Vex mechanics and parts are great and easy to prototype, newer motors and control system in the Vex V5 range have major improvements, another alternative is they carry a range of motors, rails, brackets etc everything you need to build the mechanics.

Next a cleaner and more streamlined design with sensors and the ability for a tube assembly to deliver silicon on a high wall. Real images of the robot above, I will upload videos shortly.