How to add suspension to a food trolley to prevent spillage of food and tea?

I am an A level Product design student and I am designing a food trolley for a person with grip and stability issues. 

One of the biggest problems with current models is that when they go over the slightest bump or carpet runners/plates e.g. and they will spill and tip whatever is on them. This is a massive problem if the user is carrying hot tea or their dinner, increasing clean up work and generally reducing the quality of life of the user. I cannot think of a relevant method for stabilising the food tray/drink holder without drastically reducing the overall function and massively increasing cost while still allowing the trolley to support the user while they take their food from the prep area/kitchen to the eating area. 

A few Ideas I have had:
 large pneumatic wheels (solid rubber in most other examples), Some sort of spring suspension, Pistons, A counter weight... I have tried researching stabilisers for cameras but they don't seem to be relevant. Help with research keywords would also be useful as its difficult to know what to look up.

Another problem I'm addressing is the aesthetics of the product as most examples just look like hospital equipment not everyday furniture. Currently I am siding on wood as the main material for the frame, If anybody has suggestions that would be better than boring tubular steel I am still in the early stages of development and would appreciate inspiration!

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Kiteman2 years ago

As well as the various comments about suspending the bottom of the trolley, try adding suspension to the top tray - hang it from some sort of damped pendulum to absorb the sway of the top of the trolley.

bcavaciuti (author)  Kiteman2 years ago

Yea This is the aproach I have chosen for it now. An inner tube suspended tray...being tested over the next few lessons!

Sweet, keep us updated (and remember, failure is always an option!).

bcavaciuti (author)  Kiteman2 years ago

Haha as long as I can write enough about it!

bcavaciuti (author) 2 years ago

I have decided to concentrate only on the stabilising mechanism and scrap making the trolley due to practical and time constraints. I hope to create a tray insert that can adjust to fit onto many current trolleys but can also be carried as a tray.

Currently I am testing an aluminium angle rectangle with inner tube straps supporting a pine tray in the centre. Hopefully this will dampen the jolts and wobbles associated with trolleys and unstable people. It will be suspended from two pivots so it can swing to help keep liquids in their containers.

seandogue2 years ago

A pad of tempra foam between the tray and the trolley might help,along with _possibly) a modular "tray" that allows sections to move quasi-independently. The foam is not cheap, persay, but it's far cheaper than fast hydraulic or active-control dampers.

In case you don't recognize the term, think rich people's mattresses, or the material's progenitor, NASA. (actually, it's far less expensive than it was during the early 1990s when I was using it a lot)

bcavaciuti (author)  seandogue2 years ago

Nice Idea, you can get mattress covers for relatively cheap(I nicked my grandparents spare for my bed :P). I also know a bed shop keeper that does a large amount of memory foam stuff so hopefully he will have some scraps/damaged stuff, Its only a prototype so doesn't have to be 100% sanitary otherwise id obviously use new stuff.

Im slightly worried it isnt sensitive enough to prevent little bumps, Also I found it can be permanently compressed if left folded or suspended over a chair :/ . Doubt it would be a problem...TESTING :D the only way forward now!

"Testing: the only way forward..."

Yep, that's the ticket! Good luck. I suspect that while the foam may not be to 100% surety you desire, it may go a long way towards remedying 99% of the issues. My concerns wouldn't actually be the small bumps, but the large ones. there's only so much one can do when enough impulse is delivered.

bcavaciuti (author)  seandogue2 years ago

Its mainly the everyday stuff that just makes life more difficult.

Wired_Mist2 years ago

Pneumatic tires are a must; The larger the better. Just as a person who is 6Ft tall can climb stairs faster and smother then someone who is 5Ft tall. Would also be easier to push. Perhaps some Children's bicycle wheels? You could hide them inside the walls of the trolley if you overlap the front and back tires. Two in front set just inside the two in back. Would leave a nice cubby in the middle for storage.

You may want to make a suspension system, Personally I woudn't for such a low speed vehicle. Mabey concider custom cups and plates that can be sealed to prevent spillage?

bcavaciuti (author)  Wired_Mist2 years ago

The problem with large wheels (relatively) is the base gets smaller so it could become quite unstable because the points of contact with the floor are so close together.

Is there a method to increase the area in contact with the ground whilst still keeping as many parts in contact with the floor as possible.

A pneumatic caterpillar track :D with individual balls or innertube of air or foam filled wheels. Problems start with ease of use, may become very difficult to push.

Sorry, How much do you plan on spending? :P

Simplest way to increase the surface aria of a pneumatic tire is to lower the air pressure.

bcavaciuti (author)  Wired_Mist2 years ago

I dont really know yet but its the design that has to be cheap and easy to manufacture for people who are old or disabled so it cant be too expensive the current basic trolley available is around £60 so maybe maximum £80-100 retail but by using recycled pieces in the prototype it wont cost near that.

kelseymh2 years ago

A solution that has been used many times for rough terrain is to have either six or eight wheels, paired on independent bogies. Take a look at the Mars rovers, for example. The idea is that a pair of wheels on one side can pivot over an obstacle while the other wheels remain on the ground.

The difficulty with suspension systems is their response time may not match the speed of the vehicle: hit a bump slowly, the suspension will take up the deflection; but hit it too fast and the whole vehicle gets pushed up.

Wood, or anything more elegant than food-grade stainless steel, would be awesome! You probably want to do your prototypes in something like slotted aluminum, to make adjustments easy.

bcavaciuti (author)  kelseymh2 years ago

Sounds good except for cost and time issues, got 30 hours too design and make this! and complete the coursework. I'm guessing they require suspension, maybe in conjunction with the memory foam springs this could work.

bcavaciuti (author)  bcavaciuti2 years ago

Slotted aluminium is a good idea thank you, will have to see if college can lend me some or ill have to buy it, or maybe I can raid an old bit of furniture from a charity shop or skip.

petercd2 years ago

Another idea is a trailing link suspension like the front wheel on a vespa but instead of the spring n shock, use pvc tubes filled with air sort of like an air cushion.

If you insert a tyre valve in the top section, then you can pump it with a standard foot pump to 1kpa for the rough terrain or whatever rough terrain needs.

rickharris2 years ago

Big wheels, Elastic bands, Some kind of damping to prevent oscillations. Magnets, Soft tires, Parallel arm mechanisms, low centre of gravity, Gimbals, LOOK at other situations where this an issue - Sea going cooking, Non spill Cup holders for cars,


iceng2 years ago

Years ago (20) I saw an unusual mechanical suspension system developed at NASA Alabama that may be helpful to you, Regrettably I have no idea how to find it amongst the millions of NASA docs.