Anyone for geometry? I need a mechanism to allow a structure to pivot around an instanious centre which cannot itself provide an attachment. It's for a pedal assisted electric trike which will lean when cornering thus behaving like a bicycle rather than a trike. The point about which it leans must be at road level and remain on the centre line of the vehicle at all angles of lean. Why a leaning trike rather than a bike? 'cos the regs. allow a more powerfull motor and more mass of battery! Regared Jim Lugsden.
Since (presumably?) at all three wheels are going to remain in contact with the ground, the system must pivot about the contact point(s) with the ground as the trike leans. Not what I understand as an instantaneous centre of rotation. Where do we go from there?
Hi Mark, I sold my Ariel 3 last year. They were the disaster that finished Ariel. If you hit anything with a rear wheel it caused the engine/seat unit to tip sideways but the pivot on the handlebars stopped you correcting for it.
It's been done already and looks like becoming a huge craze. Piaggio MP3. The three wheeled scooter that leans as you go round corners. All the road tests are raving about it.
Thanks for all the links chaps. The arial 3 did a bit of steering at the rear end which is a bit more complication than I can cope with. Cant see much point in the Piageo scooter, it may be designed for Celebrities. What their Vespa needed ,as I found to my cost ,was an antilock front brake rather than more front wheels! I don't think I can pick anything out of the design as I need both rear wheels to remain upright but theaks for the link anyway, it was interesting. Jim
I have seen a few recumbent bikes (homebuilts) that had all their steering duties managed by means of a swivel joint mounted under the seat. Don't think it would work so well for the trike, though.
On Tue, 15 Aug 2006 20:56:16 +0100, "James Lugsden" scrawled in the dust...
theaks for the link
Very rusty memory here, but if you want both rears to remain upright the "roll centre" will be fixed at the height of the hub from the ground. There was an excellent book from the Daily Mirror about building a racing car using BMC mini parts. Same ethos as getting you to build the Mirror dinghy. It must be 40 odd years ago, and I borrowed it from the library much later (hence the rust in the memory). It was rear-engined with double wishbone f&r suspension. It dealt with suspension geometry in great detail, not the usual saloon bar stuff, to the point of making the "string computer" to get the roll centre height to stay where it was needed under any roll condition. I taught me to fully appreciate the virtues of the 2cv which I drove exclusively for a 10 yr period in later years, the roll centre stayed on the ground and gave it the peculiar look, frightened the passengers but was predictable and fairly kind to tyres.
Wish I could find that book again, no title sticks in the brain, but the author's car was called the TerrapinMin and took sprint records at Elvington (?)
Actually, I think the specific book you meant must be "High Speed, Low Cost: The Story of a 140MPH Mini Engined World Record Breaker and How to Build It" which is also still available from Amazon.co.uk at
On Wed, 16 Aug 2006 17:30:47 +0100, Boo scrawled in the dust...
That's the fella! Good read even if you never actually build one. Covers rose joints and making special taper reamers for ball joint attachment as I recall. Possibly 21st century regs would ban the thing in competition, but the thought processes are there and the mistakes he made along the way. Good discussion on brazing v welding of lightweight chassis.
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