Mopetta workings

[noah19]

I've been trying to make a car similar to that of the mopetta using vespa parts but can't figure out if it's one wheel drive or not. If it is, wouldn't the car spin out of control? thanks in advance for any answers. (a chassis layout would also help a lot)

[Stuart Cyphus]

 Sounds intresting Noah! Any pics of this creation to see?  A Mopetta is indeed one-wheel-drive, with the engine powering whichever wheel the engine is directly in front of. Much the same as a motorcycle as after all a Mopetta is bassed around scooter mechanicals; the second rear wheel being puerly "trailing". A Mopetta is only 50cc so there just isn't the power for the "tail to wag the dog" as it were. If the engine was something like 350 or bigger, then it MIGHT wag, but if the vehicle is set up correct from the outset, no ammount of raw power should affect the handling. Much the same as motorcycles & sidecars.

 Plus, bear in mind in "proper" automotive terms, that ALL vehicles fitted with a differencial in the driven axle is in effect only single-wheel-drive as the drive will be transmited always to the side of the axle which offers least resistance, no matter how slight.

 Funnily enough, I've often thought for years that a good Mopetta subsitute could be built out of a Watsonian Bambini sidecar bodyshell......   

[noah19]

Do you think a 150cc would be overpowering?

[Bob Purton]

Hi Noah and Stuart, I think 150cc would be too far too much , as Stuart said, the Mopetta just about gets away with it because of its tiny engine, one wheel drive vehicles of this layout tend to suffer with adverse effects to the steering, sorry to disagree Stuart but motorbike and sidecars also can veer across the road under acceleration leaving the rider wresting with the handlebars. A lot of the early microcars made on the cheap had this one wheel drive like the Gordon for example plus some French cars not to mention IC's. Most suffered with the "crab effect" . As Stuart said, lets see some pictures of your build Noah. Bambino sidecar? What a good idea!

[AndrewG]

I suspect with any more power than 50cc would give, it might be sensible to include at least the ability to copy some of the geometry that has proved successful for motorcycle sidecars:
- lead (undriven rear wheel further forward than driven rear wheel);
- toe-in (pointing the whole motorcycle in towards the sidecar).

Motorcycle outifts sometimes also use lean-out (leaning the bike away from the sidecar) but that probably isn't as relevant to a Mopetta.

Incorporating lead might look wrong, but I think there is a case for making the attachment of the scooter powerplant able to be adjusted for toe-in.

Andrew