Thoughts on design - bit long I'm afraid!

[adnomev]

Guys,

The Tr1ke is probably my favourite design out there at the moment - simple, elegant, different, etc.

I've been thinking about anything I'd want to change if I bought one, and there's remarkably little, but I did have one thought about the swingarm.

(SORRY if this is a long paragraph, it might be easier with a diagram, but I can't draw!)

On the bike, as it leans into a bend the centrifugal force (horizontal) is combined with gravity (vertical) to make a diagonal force, which matches neatly with the leaning bike, so that the force goes pretty much straight down through the bike (centre of gravity straight through the centre of the bike/shock/swingarm to the tyre) so the only force on the swingarm is up & down.

However, the car can't lean, so while the same forces are applied in a corner (i.e. the horizontal one) they will apply in a different direction, which applies a sideways force to the chassis & swingarm.

I know you guys do analysis on loadings of chassis nodes, materials, weight, strength, etc so have you thought about any stress to the swingarm or the pivot it swings on, and how the design deals with it?

It may not be an issue, but I like how people solve engineering puzzles like this, so I'd be interested how it works.

Thanks,
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[tr1kerfozzy]

The kit uses standard swingarm pivots/bearing and stock wheel bearings.

Don't forget road going swingarms and bearings are designed with a huge factor of safety and are strong enough to carry two fully grown adults and luggage.

I haven't done any calculations about anything, but I'd guess you'd lose tyre traction before bending a swingarm laterally. When bikes cartwheel in a crash the frame will often bend and the swingarm will still be straight!

If I had to guess a weak point it would be the wheel bearings.

[adnomev]

Thanks Fozzy.

That's a good point about the passenger sitting right on top of it. I also thought last night if you had a rider really getting his knee down and hanging his butt off the seat, then the bike will be more upright, so it would get a bit of lateral force.

You're probably right about the traction giving first, and the over-engineering, I was just curious about how you work that stuff out when designing it. I'd thought if it was needed you could fit a simple brace to it to effectively widen the swingarm, but it's probably way stronger than needed.

Hope the build's going well, love the photos & story!

Cheers,
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