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# Any Engineers? Need shock absorber/suspension help

After reading an article a few weeks ago about a man who had made a bicycle with a triangular & pentagonal wheel & started doing some reading on the shapes.

Made a model of it but would like to try & make a full size one as we realised that it needs some parts that I couldnt make out of plywood in a little model.

Been thinking how to make it stable & came up with the idea of putting a roller on top of the wheel which is always in contact & fixed to the headstock. This will move the front of the bike up & down.

Next, the bike forks would be mounted on a hinge allowing free movement. I would weld some sort of shock absorber inbetween the fixed roller & the hinged forks which I would aim to make to be able to counteract the up & down motion of the wheel/frame if it is possible.

Any ideas whether this concept might work & any ideas for a shock absorber would be appeciated as I have no expecience with this sort of thing.

Currently doing AS physics in college & my teacher challenged me to make a model which has made me want to make a real one so I can try & overcome the problems.

Starting work on how to make the back stay level now as the article & pictures didnt give much of an insight.

Want something good to put on my personal statement too as I am applying for a physics degree this year.

If I could get it made, the aim then would be to put some dynamos on the wheels to charge a powerpack & make some sort of dashboard with lights, speedo etc on haha! Really getting into the subject & want to try some projects.

Any help is appreciated.

Thanks alot

James

It sounds like you are trying to solve a mathematical problem with brute force, i.e. letting the force happen and then using a damper to mitigate against it. That isn't how the bike works really, but instead relies on Reuleaux triangles (en.wikipedia.org/wik…gle for the want of a better reference...). I haven't looked into the bike but I imagine that the pivot changes when you reach the end point of each corner, thus setting a new pivot length.

Edit: Your pivot would have to move through using a second Reuleaux triangle, I am guessing that is the trick.

Original Poster

Yeah this principle is a reuleaux triangle & a pentagon of the same principle, ie, made from equal sectors of circles. And you are right that the pivot changes as each new arc is in contact with the ground.

From the look of the photos of the bike we concluded that it looked as it it used some kind of suspension in the forks, my teacher said it looks like the same principle as something they used to use on yamaha mopeds, this is just an assumption though as we only had the photos to look at.

The article it here..... technology.timesonline.co.uk/tol…ece

With the photos here.... china.org.cn/chi…htm

it looks like there is rollers above the wheels to keep it level?

It doesn't look like suspension to me, it looks like the way it controls the pivot.

Draw yourself a template wheel, a fixed con rod and the roller. Basically it is just a cam and follower. Rotate the wheel, at a high point on the top (low point on bottom, the one that matters to the rider) the con rod pulls the axle down, lifting the bike up, thus fixing the radius to the end of the tyre (and ground). The same is vice versa. It is a very simple idea and pretty silly unless I am missing something, a drag roller would have worked nearly as well on a round wheel.

Original Poster

Year there are rollers, they looked fixed which would make the handlebars move.

Could you expand on the way it controls the pivot please? Really interested in how it works so if you could it would be great thanks.

Off to the cinema now so might not get chance to reply until later.

Cheers
james

Original Poster

pghstochaj;5477185

Draw yourself a template wheel, a fixed con rod and the roller. Basically … Draw yourself a template wheel, a fixed con rod and the roller. Basically it is just a cam and follower. Rotate the wheel, at a high point on the top (low point on bottom, the one that matters to the rider) the con rod pulls the axle down, lifting the bike up, thus fixing the radius to the end of the tyre (and ground). The same is vice versa. It is a very simple idea and pretty silly unless I am missing something, a drag roller would have worked nearly as well on a round wheel.

I've got some made out of plywood already, trapped it between two fixed objects to prove the constant diameter part. Will have a think about the rest later but have to go out now, thanks alot

James

Well look at its axle, the fork acts as a pivot and is connected to the rollers using a rod of fixed length. The otherside of the pivot arm acts as the wheel axle centre point. When the rollers are pushed up, the con rod is pulled up, pivots on the fork and then changes the actual axle for the wheel.

Your main problem is then getting the pivot length between the end of the fork and the wheel axle correct to match the changes in the con rod position up to the roller.