Building my first Pinion frame (for myself) and messing around with creating a bridge. My default option is the cast steel bridge available from all the usual places. My design goals with a custom bridge are to save a little weight and build in extra width on the bridge for the chain stays to attach to. Don’t have access to a good brake right now, so designing/building this as individually lasercut pieces. Photos of the first quick and dirty prototype below. I immediately have some geometry tweaks to do, and probably need to build in some reinforcement on the chainstay attachment plate. Anyways, curious if anyone has immediate impressions/advice. Think this idea has legs, worth pursuing further?
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One thing I would pay close attention to is the width and contact zones for the pinion mounting points. The tolerances on the width are +/-.3mm and the center mounting width is different from the other two by .5mm (see page 17 of the OEM guideline). I designed a cradle closely based on the Archibald cradle using laser cut and turned parts. Assuming you tacked and welded with the gearbox in place yours will probably work just fine, maybe some gussets where they will fit
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Here’s a view of what I’ve made several times, at the beginning I was just bending the top part in the bench vise… The top and sides have some crenels (sorry if it’s not the right term ?) to attach them together.
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That looks great! What material and thickness were you using for that?
Thanks ! I used 5mm S355 for the sides and 1.5mm for the top (S355).
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Nicely done!
Here’s my second iteration. I feel pretty good about it. Main piece is slotted and bent and welded to the plates that have the bolt patter, plus little gussets welded on the “wings”. Goal was to have a wider place to attach chainstays to avoid using a yoke – trying to keep wheelbase relatively short and accommodate 2.6” tires.
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