Bicycle Blender Imperfections

There are many ways to improve the current bicycle blender.  Areas form improvement can be categorized into three main groups; the pitcher, the axle, and general structural support.

PITCHER

• Requires a lot of glue
• Blade can not chop ice / hard/ large items
• Blade shape often misses chunks
• Difficult to secure the nail to the blade
• Rubber sealant on the top of the cap does not hold well
• High potential for accidentally gluing the ball bearings and inhibiting rotation of the blade

AXLE

•            Fixed length
•           Transmission wheel
•           Should consider that axle may need to be removed

SUPPORT / STRUCTURE

•          Location of rear axle requires you to cut most rear racks
•          Wooden donut is very specific
•          Bungee cords are not entirely reliable / secure & look somewhat sketchy
•          Doesn’t work if the wood plank is loose
•          The blender attachment to base is not consistent

Bike Tire to Axle Transmission

The current design of the transmission wheel is a strip of bike tire coiled into a circle and held together with a mixture of Epoxy and bike repair glue.  However, the design is not very durable and uncoils frequently, requiring immediate repairs.  Furthermore, the only glue strong enough to hold the wheel together is not readily available in Nicaragua.  So, although the wheel worked well for short-term blending, if it is to be used daily for multiple hours at a time, we need to find a more secure solution sticking with the bike tire method.

            SECURING THE END OF THE COIL

We had a very difficult time figuring out a way to secure the end of the coil, so that was the first place I chose to focus on when designing a glue-free design.  Initially, we glued the inside of the tire so it behaved more like a single, flat piece of rubber rather than a tube, and found that we even needed duct tape to secure the end.

                          Somehow weaving the end of the tire back into the coil presented its self as the most promising solution.  There were a few different ways to weave the tire.  One possibility was to have multiple cuts and “basket weave” the outer layer of the tire.  Another idea was to cut two slits in the tube, the top half at one location, and the bottom half at the other, and join the two.  The last idea was a latch design, where the end of the rubber would have a single, secure weave that effectively latches into rubber it is on top of.  The basket weave proved to be very difficult to construct even using duct tape, so it did not seem likely that it would be the most practical approach, and although it was easy to construct, the slit method was not very secure.  The latch method proved to be both secure and simple to construct.  After making a duct tape prototype, it was possible to address other problems with the wheel design. 

PREVENTING UN-COILING

The layers of the original wheel that were not glued together slipped out of the coils, resulting in a dysfunctional wheel.  All that was needed was a simple support system to keep the wheel structurally sound.  The first idea tried was a piece of piano wire across the bottom of the wheel that was connected to the outermost rubber layer.  However, having only one strip of wire on the bottom did not hold the wheel together properly.  To add additional support, two more wires were added to the top of the wheel, on either side of the axle.  At all locations, the piano wire was threaded through the outer layer of rubber and bent at the ends to keep the wire from coming loose. 

Original wheel design, held together with glue and duct tape

slit method (uncoiled)

slit method (coiled)

weave method (uncoiled)

weave method (coiled)

latch method (uncoiled)

latch method (coiled, outside)

latch method (coiled, inside)

piano wire base support

piano wire top support

Final Report for the Spring Semester

 

On the day of our public presentation, we were able to successfully blend smoothies for all of our customers! The ingredients we blended included: strawberries, bananas, mangoes, raspberries, yogurt, and fruit juices. The blending apparatus was able to function hands-free, so the process only required one person, who was pedaling the bike. This met our design specifications in that it was hands-free and blended fruits. Furthermore, our blending attachment is detachable from the bike and can be adjusted to fit on bikes with differing rear rack arrangements. Future testing would include blending beans, though we expect our blender to do this easily. We had successful blends when the pitcher had only a small amount of contents in it, and also when it was completely full. Each round of smoothies only took about 30 seconds to 1 minute to make, depending on how much fruit was in the pitcher and how full the pitcher was. People were attracted by our project, and after hearing about our design and construction process, they got to walk away with a refreshing smoothie! (Some people even blended their own!)

In terms of follow-up with Grupo Fenix, we have sent them our final documentation, pictures, videos, and instruction manual. We expect to discuss our design with them this week.

As for the future, we hope to develop a working prototype of our stand design. In addition, our current design will need to be tested on different bikes. Through further testing, we hope to improve the ease with which we attach the blender attachment to the rear rack, as well as the structural integrity of the blending apparatus (specifically the rubber wheel and the blade).

One of the goals of our project this semester was to document the steps we followed and materials we used to create a working bicycle-powered blender.  By an instruction manual, we hope future groups can spend the majority of their efforts improving an existing design rather than figuring out how to simply create a working blender.

Instruction Manual

Making the Blender - Materials

• 1 pitcher with top
• 1 plastic water bottle top (cap and neck)
• 1 plastic rod (~ 1/3 inch in diameter) ( ~ 1.75 inches in length)
• 1 metal bar (~0.06 inches in diameter)
• we used the midsection of a cut nail
• 1 0.625 inch steel plated ball bearing
• 1 circular piece of rubber with a hole in it to fit around the plastic rod
• 1 piece of thick sheet metal
• width ~ 1 inch
• length ~ 5 inches
• thickness ~ 0.0315 inches (or greater)
• strong piano wire
• ~0.06 inches in diameter
• ~ 2 inches in length
• epoxy glue

Making the wheel attachment / base - Materials

• 1 complete front bike axle including:
• 1 axle (threaded rod)
• length ~ 6 inch
• 1 hub shell
• 2 sets of ball bearings (one one each end of the hub shell)
• 1 cone shaped nut
• 4 lock nuts
• Properly greased
• 1 piece of bike tire (or any form of rubber) ~1.25 feet long, to make a wheel that is ~1.7 inches in diameter
• screw eye hooks,
• screw length 0.3 inches, can be longer, but shouldn’t exceed 0.5 inches
• hook diameter 0.2 inches, can be larger or smaller
• 1 wood platform (L x W x H) = ~(9.25in x 5.75in x 0.75in)
• 1 wooden donut
• outer diameter 4.6 in (does not have to be specific)
• inner diameter 1.84 in (needs to be specific, must match the diameter of the flanges on the hub shell)
• 2 screws ~0.1 inch in diameter
• 2 aluminum standoff 6-32 x ¾”, ¼” round

Procedure:

Making the blender:

Cut the bottle cap at the red line

1. Find water bottle and cut off top including cap (make cut about ½ inch below the base of the cap, or at the location where the bottle starts to curve outward)

2. With cap removed, place ball bearing such that the bearing fits snugly inside of the cap (it may be necessary to sand the inner plastic in order to have a tight fit).

3. Drill a hole through the cap that is slightly larger than the diameter of the plastic rod

4. Screw cap onto bottle neck/ball-bearing piece.

5. Drill a small hole through the plastic rod (approximately 0.06 inches in diameter) approximately 2 mm away from either end. 

6. Insert midsection of nail into one of the small holes. 

7. Insert rod through hole in ball bearing fitted in bottle neck such that the nail is at the bottom of the bottle’s neck. The nail should not touch the edges of the bottle cap when rotated (trim as necessary).  

8. Cut out rubber washer with an outer diameter that matches the diameter of the bottle cap, and an inner diameter that is slightly smaller than the diameter of the plastic rod (so that it fits snugly). Place this washer such that it rests on the bottle cap.

9. Insert approximately 2 inches of piano wire into other small hole that is above the bottle cap/ rubber washer. 

10. If the rod moves vertically, carefully apply a thin layer of epoxy glue to the inner side of the ball bearing. Ensure that the ball bearings can still freely rotate. 

11. Glue the rubber washer with epoxy glue to the top of the bottle cap.

12. Obtain a a 1 in x 5 in x .03 in (or slightly larger) piece of sheet metal. 

13. Drill a hole of the same diameter as the plastic rod in the center of the metal piece.

14. Sharpen the length of the blade on both sides by sanding the edges. 

15. Using a rounded surface, gently bend each end of the metal piece into a c-shaped curl (refer to blade

picture).

16. Place blade, with c-shaped curl facing down, on plastic rod and allow it to rest on the piano wire. 

17. Bend the piano wire around the top of the blade so that it is hugging the top of the blade. The blade should not move independently of the rod. 

18. Using a step drill bit, drill a hole in the center of the bottom of the pitcher that matches or slightly exceeds the diameter of the bottle neck.

19. Apply a thin layer of epoxy on the bottom of the lip of the bottle.

20. Insert the bottle cap/blade piece into the hole at the bottom of the pitcher. Allow glue to set.

 Making the wheel axle:

1. Remove lock nuts on one end of axle.

2. Make a slit at one end in the 1 foot long piece of rubber and insert the axle through this slit. Refasten lock nuts to the axle such that they are on either side of the rubber.

3. At the other end of the axle, remove both lock nuts. Cut rod such that the top of the axle is approximately 1/4 of an inch below the top of the bottom nut (the one that sits closer to the ball bearings). Reattach bottom nut.

4. Using a dremel tool (or a hand saw), cut a channel through the middle of the nut (along the diameter) such that the nail used in the plastic rod can sit in the wedge: 

5. Fully extend the length of rubber and flatten such that there are two distinct sides. Apply epoxy to one side and tightly wrap the full length of the rubber around the lock nuts, forming a wheel. Clamp the wheel in this arrangement until the epoxy dries.

 

 Securing blender and wheel axle to rear rack of bike:

1. Insert axle to rear rack such that rubber wheel sits against the middle of the bike’s rear tire . It may be necessary to cut a hole in the rear rack in order to fit the axle through.

2. While the axle is correctly positioned (step 1), cut U channel in wood platform so the axle can rest in the channel. 

3. Secure axle to channel using approximately 5 eye screw hooks.

 4. Next, prepare the wooden donut to support the blender with correct dimensions.

5. With the wooden platform- wheel axle arrangement aligned correctly, insert 2 screws on the opposite side of the wooden platform such that they rest against the outer rim of the rear rack.  Once screws are inserted, place aluminum standoffs on the screws.

6. Wrap two small bungee cords, positioned on both sides of the wheel axle, around the rear rack to secure the platform in place. 

7. Fit blender in wheel axle (ensuring that the nail in the plastic rod fits in the channel in the lock nut) and secure by wrapping a large bungee cord from one side of rear wheel axle to the other side of the rear wheel axle, making sure to pass the bungee cord over the top of the pitcher as seen in picture A

 8. Hop on the bike, blend, and enjoy the fruits of your labor!

PICTURE A

Final Post!

This will be our final post! We feel as if the last part of the semester spent working on this project has flown by. Looking back on the entire experience, some challenges we had were:
1. UNDERSTANDING THE PROBLEM. Until we talked to our community partner and saw photos of their current product, it was very difficult to approach this project; even after having our conversation and looking at their photos, it was still difficult to truly understand the problem and how to come up with a better solution that wouldn't just create different problems.
2. ORDERING THE CORRECT PARTS. In essence we were trying to replicate a blending apparatus that had been used and implemented in Tanzania. Despite having the physical product in our hands, it was difficult to replicate due to the fact that we had limited documentation. Therefore, in ordering the parts we needed, we did a lot of measuring and estimating, and hoping for the best!
3. SIMPLIFYING AN EXISTING PRODUCT. Jodie Wu's stand is extremely functional. However, it has a lot of parts, so we wanted to simplify her design. Rather quickly we learned that  while it is extremely difficult to come up with an entirely new product or design, it is almost harder in a sense to take steps backwards and make an existing design more basic.
4. DECIDING WHERE TO ATTACH THE STAND. Attaching the stand to the bike frame (chain stays) or to a wheel spoke attachment was a difficult and time-consuming decision for us, as each has its benefits and challenges.
5. DETAILS REALLY MATTER! There were countless times during our process where we'd say "Shoot, we should have done that before this." We learned the importance of thinking ahead and building strategically, as it is difficult to do certain things once pieces are already attached-- especially when working with machinery! In addition, we learned that drilling a hole or cutting a rod one centimeter too small or too big makes all the difference, and that getting to the precise measurement you need is painstaking, requiring lots of trial and error.

While we may not have had the opportunity to accomplish as much as we were hoping to due to time constraints, the goal is that this blog and our final write-up (with a step-by-step instruction manual) will serve as a foundation for the next team who takes on this project.

After our bike blending apparatus was completed, we realized it was wishful thinking that the pitcher would sit and stay attached to the wheel axle during blending without support. We went through a number of different ideas and trial runs of support mechanisms, but ultimately we came up with the following design:

We constructed a wooden plank (made up of multiple wood pieces to get the correct height) to elevate the wheel axle so that our rubber wheel comes into contact with the bike wheel at the right place, as pictured below:

We attached the wheel axle to the wooden plank using screws:

The next step was the make a platform for the blender (pitcher) to sit on in order to increase stability. We decided to go with a ring shape, mimicking the shape of the bottom of the pitcher. First we constructed a styrofoam prototype, then Professor Banzaert helped up make a wooden one using the laser cutter. It has a large hole inside for the wheel axle to sit in:

 While we knew we would secure the larger, square wooden platform to the bike rack using small bungee cords, we needed to prevent the platform from moving horizontally across the bike. Therefore, we screwed in metal rods to serve as stoppers, keeping the platform at the correct location for maximal wheel contact:

Our last step in securing our apparatus was securing the pitcher. We decided to be as simple as possible and use a bungee cord, going from one side of the rear rack (near the tire spokes) to the other, up and over the blender. We strategically used the handle and spout of the pitcher as holsters for the bungee:

Here is a video of our second test run (in class), in which we blended raspberries, strawberries, and water:

On the day of our public presentation, we are pleased to report that our bicycle blender was a huge hit; more importantly, it worked without fail during the entire exhibition!!! We were able to concoct numerous smoothies catered to our customer's tastes! Ingredients used included bananas, strawberries, raspberries, mangoes, plain and vanilla yogurt, and a variety of juices. Some of our customers even hopped on the bike themselves and blended their own smoothies! It was a lot of fun, and satisfying to see that our work paid off. Here we are blending an extremely full pitcher of smoothies on the day of our public presentation:

*Please note: the bike stand we used was Jodie Wu's stand. We have a prototype of our design (a simplified, easier-to-build version of Jodie's), but unfortunately we were unable to construct a working product due to time constraints.

Thank you for reading, and happy blending!!!