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Dilemma

Old 08-17-19, 12:53 PM
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VtwinVince
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Dilemma

My next project is an aluminum Softride Powercurve, and I've just noticed that the down tube took a hit right at the braze-on for the shift cable guide, and it has caused a creased dent in the down tube. Now I'm thinking maybe I should just bin it? It's cosmetic damage, no apparent cracks.
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Old 08-17-19, 01:37 PM
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I'm not sure why you're posting if you aren't going to post a picture.
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Old 08-17-19, 01:45 PM
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Damage is often cosmetic, until it isn't. IIRC Softrides have only a single frame member between the headtube and the seat tube/bb. Unlike a failure in a normal diamond frame where the break is supported by the "other ends" this down tube's complete failure will leave only a handful of cables holding the front and rear together. Andy
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Old 08-17-19, 02:16 PM
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Assuming you are referring to the frame with two tubes between the head tube and the BB then a crease that is
transverse across the tube would be much more concerning than a longitudinal crease. Aluminum does take
well to bending and sudden failure is a higher risk than with a steel or Ti frame. A pix would help.

One other thing, a few friends have had softrides and there can be resonance at certain cadences with the
seat beam resulting in a lot of bouncing. Kind of weird when you are behind such and it occurs.
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Old 08-17-19, 10:54 PM
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Kind of hard to photograph, but you can sort of make out the crease running parallel to the tube, right down the middle. There is also a crack in the paint.
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Old 08-18-19, 07:00 AM
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By the looks of the frame, it looks like it has a conventional downtube, with the leaf spring mounted along the top tube, like this. Is that the style of your frame? If so, you have a little more margin for safety with regards to what Andy said above. With the paint still on the frame, it's hard to know exactly what the impact looks like underneath. I imagine the Softride bikes put unique stresses on the frame; I imagine something like that would be "fine" on a traditional frame with the rider's weight on the seat tube, but the Softride design may be more sensitive to something like this (I don't know for sure).
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Old 08-18-19, 10:15 AM
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If anything I would think that the swinging seat, that Softride has, will lessen the force peaks in a traditional down tube and possibly increase the forces in the top tube. I have only worked on a few dozen over the years and saw issues with seat beam pivots and the frame right about the pivot "braze on".

The few tandems I've come across with beams have a curious reaction from the riders. Stokers really likes the suspension, captains liked that their stoker was happy but some disliked the added body movement. Andy
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Old 08-18-19, 11:14 AM
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Thanks for the feedback. I feel that structurally the frame is OK, and it appears that the paint cracked when the tube flexed inwards.
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Old 08-18-19, 11:44 AM
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That damage would be much less worrisome to me, mostly cosmetic, but a stressor that eventually,
probably years from now may crack.

As to the resonance bouncing of the beam with certain cadences I have seen this on both a singleton
and a tandem. As Andy noted, stokers kind of like it but the pilot can find it disconcerting.
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