Here is what to do and what not to do while building bumpers.

Do Not Make Reversible Bumpers: The main reason to make them is so they can be mounted strong but still be easy to change. However, they are harder to make and down in the mounting section there is a way to mount the bumpers that is easy to change while still being strong. Therefore, there is no point to reversible bumpers.

Materials needed

Materials are minimums for 3 sets of bumpers. and there are left overs so check quantities of what’s in stock before ordering more. Most items can be found at Menard’s. Also confirm that bumper rules have not changed before ordering all the materials. Quantities are suggestions so review how it will be used before buying.

  • Fabric
    • Fabric in Blue, Red, and Black
  • Numbers
    • Numbers (See below for how you want to do numbering)
  • Wood/Fastening Wood
    • 72” 2x2 1/8” angle
    • 72 1/4-20 3/4” bolts (any kind of flattened head will work)
    • 4’ by 8’ 3/4” Plywood cut into 5” strips
    • 72 1/4” T-Nuts
    • 3/4” x 1/16” angle (This is an optional item)
  • Pool Noodles
    • Pool Noodles (~6 per bumper set but is based on frame perimeter)
  • Mounting
    • 72” 1x1 1/8” angle
    • 40 3/4” wood screws
    • 72” 2” by 1/8” plate
    • Wood screws couple inches long (We have a lot of these and they can be kind of anything as long as the heads are a small width)
    • 2 1/2” pins to 3” pins (These are reused from year to year but we can always use more)
  • Repairs
    • 2 rolls Red, Blue, and Black duct tape

Fabric

Fabric should not rip and should last an entire season. We have found two fabrics that are relatively cheap and capable of this.

AndyMark Cordura fabric is durable but it is very rough. This makes it difficult for the robot to slide by other robots. Numbers also have more problems sticking and need more care. Only available in blue and red so practice robot has to be different material or red.

Sports Twill is a slicker material. Our team used these for practice bumpers in 2019, so application to competition robot is unknown. The fabric held up well to the stresses of practice. Numbering can be easier but the more time put in to the numbers the longer they will stay. Suggested colors for ordering are red and royal blue. Practice bumpers can be in any color but Black generally looks pretty good.

When stapling the fabric to the wood, make sure to pull it tight. The fabric looks best if you line it up then staple the ends. After stapling the ends staple along all the flat sides but leave some room on corners. Fold the corners in so they look nice and uniform, similar to wrapping a present. Then staple down the corner so it will stay nicely wrapped. Cut inside corners as needed to make sure the bumper is flush. While stapling be aware of where people’s hands are so you don’t staple them. There are some safety features but staples will come out the side of the wood so give a bit of space.

Numbers

For 2018 and the beginning of 2019 we used vinyl this worked for smooth fabrics such as the sports twill. However it peels a lot on rougher fabrics like the AndyMark fabric. If it is peeling hot glue can be used for repairs.

In 2019 Connie suggested using Stich witchery this was used on the AndyMark material for worlds’s bumpers. A white cloth would have to be bought to be stuck to the fabric. This is very time consuming because of the stitching that needs to be done around the border to secure it.

Wood

Wood should be cut into 5” strips as long as the bumper rules don’t change. This number can easily be found in the bumper section of the rules. If you would like the fabric attached more securely you can router the edges so that there is an indent. The indent is for angle brackets to be attached to the edges. This allows for flat mounting and secure fabric. However we did not do this in 2018 or 2019 and did not have issue with the fabric coming off so this is not really necessary.

When cutting the wood and pool noodles draw out the bumpers with wood and noodles including thickness. This allows you to do the math to figure out how the wood will fit in the angle an make sure everything is long enough and fits on the robot.

Pool Noodles

Pool Noodles can really be anything as long as they are around 2.5 inch thick. The standard size is 2 3/8” and this works fine for the bumpers. 2 are needed in each bumper and they should be consistent through out the bumpers.

Pool noodles are fairly cheap in bulk and since they are needed every year it is easy to get mentor approval for large orders. They are cheapest to order right at the end of summer just don’t wait too long or they are out of stock.

Corners of the pool noodles can be done in many different ways. The way that seems to work the best is making the noodles angled and meet in the middle. Tho corners should just be packed to make sure they are full. This just requires patience and make sure the numbers for length on both sides are correct. A separate pool noodle for the corner works fine. The corner does get beaten up and may not last as long. Having one of the pool noodles hang into the corner seems to have the same problem.

Mounting

What was done for mounting in 2018 and 2019 was a flat bracket on the bottom and an angle bracket on the top of the frame. This mounting works well but can be dependent on what the bumper zone is and wheel size. Angle brackets can be used on both sides but then adjust the shopping list accordingly.

The plates on the bottom were cut to be 1 3/4” long. Two holes are drilled about 1/2” away from the 2” side and at least 1” away from each other. These holes will be used for mounting with the long screws and may need to be countersunk depending on clearances with the field. Make sure the screws fit through the hole but do not slip all the way through.

The angles have two holes on one side of the angle about 1 1/2” away from each other. These are for the 3/4” screws so make sure they have clearance but the screws won’t pull through.

After all your brackets have screw holes you can put them on the bumpers. To put them on the bumpers drill a pilot hole and put the screw in one at a time. After the bottom brackets are all attached where you want them. Put the bumper on the robot and drill through the frame so all your holes line up. The top bracket works in the same way just with no pilot holes. To line up the top brackets use the special bumper bar with the correct spacing of gussets. This will insure that the distancing is good and that the bumpers will fit on the robot. After all your brackets are on the bumpers you can drill through the bottom and make sure all your pins line up.

Assembly Order

  1. Cut out wood
  2. Attach wood at the angles
  3. Put on the pool noodles
  4. Numbers on fabric
  5. Attach fabric to bumper
  6. Mount bottom bracket
  7. Drill bottom bracket hole
  8. Mount top bracket
  9. Drill top bracket hole
  10. Check pin alignment
  11. Recheck pin alignment at the competition
  12. Repair as needed