Join Date: Jan 2007
Location: Hobart, Tasmania
Bikes: Frankenbike road transporter; Cannondale F500; Xtracycle + Wheeler 5800; Columbus Fixie; IronHorse SS MTB
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fixing the frame flex
so i've got an xtracycle hooked up to a Wheeler 5900 mtb (i got it second hand, i'd say it is mid 90s mid range level)
now most of the time it's totally fine but the other day, hauling a big ol' monitor and pc box home from the tip shop i noticed more flex then normal. fine, i had more weight then normal, plus it was pretty badly balanced.
so i had a better look at the whole setup, and althopugh im sure the xtracycle itself is giving me a bit of flex, a substantial part of it seemes to be coming from the rear triangle of the donor bike. at least, it is when i grab the bike and twist it!
the wheeler is by no means overbuilt compared to a lot of mtbs out there - i see my issue mostly related to my donor frame, not the xtracycle although obviously it puts a lot of un-designed for forces through the frame)
so my real question is this: how could i got about stiffening up this rear triangle, bearing in mind i dont haveto worry about the wheel in there.
my two main thoughts have been: a 'high' tension cable with p-clamps or brazeons in a zig-zag kind of pattern along a section of the seat stays. i wouldnt know how many zigzags id need or how far along the seatstays i should extend my addition
a solid plate of some kind (eg some aluminum sheet) somehow similarly attached firmly between the stays. again, i wouldnt know how big it would eed to be, nor how thick. perhaps i could drill out lightening holes, but then again, maybe if my holes were in the wrong spot for the tension produced it could be bad.?
actually, having written that I guess the middle option would be tension straps (like in the building industry) but i think they'd be a bit hard to get proper tension on in this case.
so, any ideas? i guess im searching for a strength-weight ratio here, in a method that will be effective!
(2 hours searching hasnt helped yet!)