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PostPosted: Thu Apr 05, 2012 12:09 am 
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Joined: Mon Aug 18, 2008 11:23 am
Posts: 295
Location: London, UK
I'm sorry to say I'm with JeRkY on this one, there is so much to cover before committing to spend any time or money making a design real. I also don't want to heap negativity on this project, but to encourage you to keep researching and looking at what's worked (and not worked) elsewhere, and why.

If you're definitely after a one-legged design, how about a large very stiff monocoque-style single chainstay with a pivot just above the BB and a shock either above the swingarm or inboard, inside the main frame. I'm thinking along the lines of motorbike rear ends... although that does then present a problem if you have a rear hub with one attachment point - the rear wheel needs to be driven, and also to brake.

It's late and I'm waffling, but do stick with it - this is an interesting project and it has potential! All the best.


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PostPosted: Thu Apr 05, 2012 3:41 am 
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Joined: Sun Mar 27, 2011 2:47 am
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Location: Cleethorpes
One thing I've made a (possibly) major mistake with is, the geometry I've used is for a hardtail. I'm looking through a lot of FS designs now and will change mine accordingly.

When I mentioned the tubing sizes I meant I've not seen toptubes that are atleast visibly larger than 28.6mm.

Monocoque is probably the next step so I'll try a few things.


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PostPosted: Thu Apr 05, 2012 12:17 pm 
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GT had a single-sided swingarm bike at a show once, it had some completely barking brake arrangement. I'll see if I can find a picture :)


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PostPosted: Thu Apr 05, 2012 12:21 pm 
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Tube sizes -- the nearest aluminium bike I have to hand has a ~35mm top tube and ~42mm down tube. It's not even a mountain bike, let alone a full-suspension one, and it's pretty skinny looking really. Most modern aluminium bikes have seatposts fatter than 28.6, never mind frame tubes :)


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PostPosted: Thu Apr 05, 2012 5:58 pm 
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Made a 2-piece swingarm, haven't changed the seat angle yet but I think it should be ok, not too sure.

Image

I haven't done the pivot in this one yet but it will be in the same position as the Orange 5.


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PostPosted: Thu Apr 05, 2012 6:35 pm 
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Joined: Mon Apr 03, 2006 5:11 pm
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Pondering:

Make the swingarm as beefy and stiff as an Orange 5: connect the two halves ahead of the seat tube, and use a bolt in rear wheel.

Then you could use a single fork leg in the position you have it, but have half a fork crown in front of the tyre with the steerer ging to a pivot at the ST / TT junction.

This might be an improvement, as you are effectively replacing a short stroke shock (e.g. conventional air shock) with a long stroke shock (from a fork leg) which should make it more supple and suffer less from seal stiction (although kashmina coated RP23s are very slick).

Would have to choose the mount point along the chainstay (therefore the angle of the shock) carefully to get the desired rate.


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