69 CB350 - Modern Suzuki Front | Ducati Rear - Cognito Moto
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xb33bsa said:
That center tube supporting the swing arm is 7" long. I can not go wider than the swingarm allows. The Ducati swing arm bolts almost identical to the stock cb350 swingarm. The inside is the frame mounting (pivot point) and the outsides mounts keep the shaft from walking.
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50gary
Under the Limelight
I would use just the single caliper and rotor up front. Save a lot of weight and rotating weight.
In the rear I would run a near vertical tube from the sub-frame down to the horizontal swingarm support tube. Vintage XS650 Yams. (racing) have a similar town tube problem and can crack the frame just below the big curve. The bike already looks cool.
Cheers, 50gary
In the rear I would run a near vertical tube from the sub-frame down to the horizontal swingarm support tube. Vintage XS650 Yams. (racing) have a similar town tube problem and can crack the frame just below the big curve. The bike already looks cool.
Cheers, 50gary
SpeedBump said:
That raises two issues. It suggests that the Ducati frame is a single tube which it isn't, and it raises the real issue that teh Duc ties teh ends to something to stop them moving.
The forces that will tear the frame are not simple straight up and down hitting a bump, but cornering when laid over at an angle. In that situation, the forces are sideways on the middle of the frame trying to push the bike out against the friction between tire and road.
The easy way to think of it is to imaging clamping the motor and the center of the frame in a jig and apply a sideways force to the bottom of the rear wheel. The wheel will tend to twist vertically and the center frame tube will tend to just rotate and act like a big spring. That is exactly how our old Triumphs reacted - like a ratchet going around corners. It would wind up until the force in the frame tube was greater than the friction at the wheel and then it would skip sideways and repeat . With a stiffer swingarm and stickier rubber, side forces will resolve through the frame.
Fortunately not a whole lot of power to deal with but still enough to cause a problem going round corners potentially. I'd like to see FEA showing stresses and deflection in that frame.
50gary
Under the Limelight
That's what I was suggesting in reply #28. I would also drill a large diameter hole in each of the two lower plate gussets. Eventually cradle frames always end up or tend towards a version of the Featherbed. Single tube backbone frames are an economic "solution" IMO.
Cheers, 50gary
Cheers, 50gary
