swingarms when doing bike engine conversion

[tonydevon]

apologies if this isnt in the right section, I had a look and couldnt work out where to put it??

anyways, I have looked and seen the great converisons that are around that end up utilising a very short swingarm, with a whats similar to the bike engine cradle replicated under the panels to mount the engine

Im not saying theres anythign wrong with that method it obviously works. but I like to question things

now Im new and was just wondering if I could, or perhaps why I shouldnt...

with a small bike engine, ie a 125, 200cc etc, create a swingarm/mount that the engine fits onto and sort of creates a scooter engine setup.

the engine and exhaust all move with the back wheel

my thought being that this will allow a better arc of travel for the suspension and probably easier to get that working better, as well as giving constant chain tension from engine to rear wheel.

I thought about the sprung and unsprung mass situation, but surely it cant be that much different weightwise twixt a complete lammy engine and a small single cylinder bike engine, probably lighter bike engine????

I await being shot down in flames

[sean brady scooters]

that sounds good to me
I think OZ did it that way on his rotax engined vespa 50

[RICSPEED]

IFi was gonna do a scratch build frame i would be tempted to take the frame tube down rather that up at the bridge section then passing under the engine and then up the back mounting the swing arm from this point if you follow me

[sean brady scooters]

bit like an LD frame ric

[RICSPEED]

sommat like this ....



save p1551ing around with cradles(could keep orriginal frame numbers too)

yes sean..... just like an ld ...pity ld iwould be too weak i think

[RICSPEED]

[RICSPEED]

going over your first post again i dont think i fully answered it ,my thoughts on this are that in Oz's case the kart engine had no gearbox and only a small centrifugal clutch to get moving ,as i recall from the right up in scootering it took a while to get going and come on song as it were but back to my point here that the motor used was pretty light and as such diddnt pose much of a problem regarding unstrung weight ,
i think you would soon find the ride a bit strange to say the least also fitting the motor conventionally allows the exhaust to have more fixing point too not to mention stuff like rear sets should you wish to


have look round here - http://www.hostingphpbb.com/forum/index ... =seriessix

few lads on there building 350 ypvs scoots and the like and might be able to put you mind at rest re the short swing arm

[Speed Demon]

I think it will work mounting the engine on the swinging arm as long as the donor engine is light enough. As soon as it gets heavy and you have a lot of inertia you will get into all sorts of handling problems (e.g. early Piaggio X9 500).

[byron]

Twinny should really post some pics of his KR1 powered series II
the whole engine along with the pipes swings on a pivot just below the bridge piece, this has a scratch built tubular chassis to hold the engine, and the original seat loop bolts on top of this.
It's a tidy job. [as are the electrics now ]

[tonydevon]

now that sounds like what I was thinking, but mines lighter and far less power

just realised that maybe Im missing something very simple here, if I build my own frame, then hardtail it, stiff frame, put more power to the tarmac and easier...

I build enough bike frames like that, so why not a scooter.

this site is great, such a wide range of scooters, styles and powerplants etc.