a brake lever
Stopping a runaway pram from rolling helplessly all the way
into a pit of crocodiles/trouble and ultimately saving the day! Around two weeks after graduation I was witness to a lady tripping, letting go of a pram and the pram rolling down a hill. Luckily the pram and baby was caught meters into its adventure and a project had revealed itself to me. I wanted the solution to be realistic for the market but also retro-fittable to other prams. I envisioned the product being supplied to pram manufactures but also the public in the same way shimano market and supply their products to the cycle industry, ie separate to the pram brand itself.
Naturally any solution would have to be attached or be part of a pram and therefore compliment the pram’s aesthetics. Ive assembled a selection of contemporary popular prams and pushchairs that I feel would be the target prams for such a device. The Silvercross Dazzle to the immediate right is the exception but I feel its super clean aesthetic is going to influence other prams heavily in times to come and as such needs to be appreciated. The key aesthetic components of all the prams are clean bold “primary” shapes with an utilitarian look and finish. The dazzle adds an extra layer of cleanliness and subdues the utilitarian feel, I feel.
Context
At first I was thinking about a system that was integrated into the body of the push chair that utilized a normal brake lever. When activated the part would clamp the brake cable in place and then rotate around another point like shown to the left. The next idea consisted of altering the path the brake cable took within the brake lever. When the cable is pulled below the handle pivot point the effect of the lever changes to suit the results required.
Ideas
I was aiming for a bold, friendly form that didn’t look too engineered like most brake levers. After a few “ish� forms I rather like the form to the left. Its became apparent that I needed to use bold simple forms assembled into a clean profile. I used illustrator to bash out a few silhouettes.
The concept
I did begin to think about a another method of routing the cable so that the cable enters the body closer to the handlebars. I found that it gets too complex though as the cable needs to pivot around the handle pivot point before it does anything else so that when pulled back for the secondary routing it activates the brake.
Cable play
For the design and idea to work the plunger needed to be pulled back, locked into place and released easily. Whilst mechanisms found in retractable pens would be nice I don’t think its inherited problems outweigh its functional worth. I was also thinking about integrating the whole mechanism into the molding of the body and having the body in two parts but I came to the conclusion that it also created more functional problems than it solved.
Insides
The handle connects to the body of the brake lever by two nipples on the inside of the lever. Small springs sit around the nipple and locate in both. At first I thought about using a metal insert that slipped into a hollow lever. Bit too hard to manufacture and naturally push’s the price up. The other solution would be to manufacture the whole piece in solid high grade abs in 2 or maybe 3 process’s.
Brake lever
A subtle aesthetically friendly inoffensive dead mans brake lever perfectly suited to modern prams and pushchairs. The form is designed to compliment prams for such brands as phil & teds.
The concept
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When the brake lever is in normal mode the cable pivots on the plunger above the rotational point of the handle. When in deadmans mode the brake cable is pulled back to take up any slack and the amount of cable movement needed to activate the brake. When the handle is pulled back the brake is deactivated. When the handle is released the brake is reactivated by the pull of the springs around the rotational point of the handle.
How it works
Illustrator linework superimposed on studiotool models.
Iterations
Naturally being an Industrial Design project I paid alot of attention to how the object would be manufactured. The majority of the parts would be injection molded in multiple part molds. I do have some reservations concerning how ive designed the insert and handle to be assembled but if it turns out to be unfeasible the design could be easily modified to assemble in a more traditional method but with detriment to the aesthetic.
Manufacturing
The main body/shell of the brake is manufactured in a abs plastic. The part would be injection molded in a 7 part mold, 4 parts each entering from the front, back, left, right. 1 part for the bottom screw hole and the two other parts for the holes on the bottom half of the main cylinder. My concern is that injection molding requires a draft angle, especially on that main internal surface due to shrinkage. In a perfect world I would want that surface flat so it interfaces with the insert well. This could be possible by some secondary machining, more parts to the mold or from a different perspective applying a mirroring draft angle to the insert.
The body
The part would be manufactured from a abs via injection molding with 5 parts to the mold. 2 parts of the mold would be used to mold the majority of the levers front, top, bottom and back surfaces. The linework overlaid on the image shows the location of the other parts of the mold. After the part has been molded the internal cavity ive labelled “a� would be machined out using the opening to the left. The surface finish or tolerance of this internal cavity isn’t too critical.
The Lever
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The yellow cylinder in the cutout below is a tube of foam that sits around the shaft and sits between a ledge on the shaft and a ledge on the insert. Its there to cushion the movement of the shaft. When pulling the ball back, resistance is offered by the springs in the actual brake. When the ball is rotated off lock position when in the mode below all the springs in the system are going to make the rod snap back into the lever which could trap/hurt etc. The foam offers resistance and stops fingers getting caught etc. It does restrict the effectiveness of the lever though. One other solution would be a rubber seal as found on bike pumps possibly. Ive played safe with the foam for now but both options need to be tested before I can defiantly choose one or the other.
Foam
The most expensive part of the product to manufacture undoubtedly would be this internal cylinder that houses the plunger and connects the lever to the body. Due to its cost the part is suitable for use in both the right and left handed versions of the handle by rotating it by 180° along the length of the part to save on tooling costs. As I hope you can see the part has alot of internal surfaces, some of which require that no draft angle is applied. All the internal surfaces are easily reached from the outside via no undercuts or the like. In terms of process’s, investment casting is perfect. Fitting the lever onto the insert I hope is achievable via the two parts flexing. Firstly the brake lever flexing due to the material its manufactured in and the secondly the insert flexing due to the pronged form of the front. If this isn’t feasible its easily remedied by removable axles between the two.
Insert
As modeled on a cosatto budito hopfully imply its scale and posistioning. One of the features of the design is that the brake lever could be mounted upside down undernieth the bars with no adverse effect to its function if the user wished.
Setting the scene, dad decides to take his daughter out in her pram for a little walk. 1. After a while the two arrive at the top of a decent into the park. Dad always eering on the side of caution decides to engage the deadmans brake. 2. Dad pulls in the brake lever to disengage the brake and starts the decent. 3. Dad uncannily slips on a banana skin, slipping over and inadvertently releasing the pram. As he releases the brake lever, the springs inside the lever reapply the brakes stopping the pram rolling down the hill and into a pool of crocodiles. Another instance of its use would be within a shop, busy city or theme park where the parent and pram are continuously stopping and starting. In that instant the deadmans brake becomes a convince over the current brake systems.
In use
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One of the large advantages of the design is that all the components apart from the outer body/shell are standard across all the different versions of the lever. Three versions to accommodate the different profiles of handle bars and two versions of each of the three versions to accommodate left or right handed operation. Handle 1 is suited for prams made by phil and teds, silvercross. Handle 2 is suited for prams made by quinny and boogaloo. Handle 3 has a fabric adjustable strap for handle bars unsuited to the others.
Options
1. all the above needs testing but Im unable to do so due to having no resources capable of the task. Whilst im confident that the decisions ive made will be justified after testing it needs a prototype to offer it some creditability. 2. I haven’t added any branding to the object but there’s clear suitable positions on either side for a name printed in silver or the like. Thanks for looking through the book and I hope you’ve enjoyed this little journey. Feel free to contact me at; bobeeb@gmail.com
Points to note/the ending