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new dually
NB: Originally posted elsewhere on the Global Riders Network and appears via syndication.
Made a new Ti dually. Can anyone see what is going on here? More photos added 27th.
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Can we see details of the BB and chainstay pivot arrangement?
I will leave that until tomorrow. Just gotta guess at the moment....
Is it different size wheels I spy?
Very nice! Is there a pivot between the seat & chain stays? Or is there a brace hiding behind the rear tire? More pics!!!
The lower shock pivot, is it stabilized by a flexing plate from the top and seat junction?
Pretty close browndog
just by looking at it..... that shock aint gonna compress. it will just pivot fore and aft.
unless I am missing something
EDIT:
Just had a look at the pic again. is there a strut that runs from top tube/seattube joint to lower shock mount. in that case..... that shock ain't gonna move at all. Not now, not ever.
LOL You make me laugh Jaredp.
Another great effort Crispy Have you weighed it yet?
Does it have any bearings or are they all fixed joints?
Is it so Heavy you need a forklift to move it?
Like Browndog says but I think you are using a flat spar/flex plate mounted on the seatpost/toptube joint to direct the forward movement of the swingarm into an arc that pushes the shock.
The design relies on the flex of the chain stays rather than use additional pivots & the spar adds lateral rigidity. It also keeps the weight down.
The Yeti flexing carbon stays are the nearest I know of to this but they use a dogbone with bearings.
Oh, and I think you've used Titanium because of it's various good properties and because I know that you can work the stuff.
Very nice, how does it ride?
T
Photos added to the OP.
Dual Ti flex plate. 11.5 kg total build atm. My guess with the saint cranks. Tricon rear wheel. Frame and shock about 2 kg.
Ps thanks to Kd's for bits an pieces and parts.
You and your single speed bikes Crispy. Well done mate, it looks like it's going to be a beauty.
How does it ride?
And if it rides well, how much for a copy?
Interesting, so it has no swing arm pivots at all? Good from a maintenance perspective with no bearings to replace. Given the fatigue limit for Ti is about 40% of UTS and is very dependent on surface finish and stress concentrators I'd be a bit concerned that you might get failure over time if that fatigue limit is exceeded.
How much springing do the flex plates provide without the shock fitted? I guess you just run less air in the shock to compensate so it would work, just a bit of a head twist
So is the rotation of the chainstay provided by the flex of the lower plate only, or does the chainstay itself contributes some, because the plate looks mighty short to be entrusted with such deflection?
At least the upper flex plate's got some length to it to tackle the job.
Trying to work out which bit will do the skewering of what part of the rider's body, if it does give...
Maybe wear a helmet on your bum as well as your head
I hope I'm all wrong!
Technical Info
HA 68.5
CS 420
Travel 110 (designed)
Pivots are 3mm grade 5 Ti
Bottom one is 35mm long and 75mm wide
Top is 130mm long and 50mm wide
Yield was at 18deg at 35mm
110 travel was about 15.5deg
Plates where welded in at 30% of travel.
So 5deg travel up and 10deg down to designed bottom out.
From my research grade 5 ti has infinite cycles at anything less than 50% of yield.
Should be fine. But we will see
The only issue is the pressure required in the shock to push out the 30% makes it pretty stiff it the rear end. I had trouble reaching 70% of the travel bouncing around the car park. But good for single speeding.
the whole bike is very stiff and responsive as a whole.
The top plate being nearly 90deg to the bottom one creates the lateral stiffness.
I will be racing it at turners
I think I answered everything.
Nice softail. That sort of flex rather than pivot idea was big(ish) in the 90s
You need a suspension stem like the old softride power wings to finish it off.
Some purple ano would also increase the awesome
Sorry Flynn, I am not really old enough to be retro yet haha.
In a way it was based on a softail idea. Just better pivot placement to stop pedal bob, more travel and modern geometry.
Just my thinking is if I can make a bike why buy one and why make one that I could buy?
Going with that I am pretty sure a design like this has never been done before. Maybe there is a reason, and I have not found it out yet.
You may even see me carrying out two parts of a bike from the back of turners hill on sundays race. Lol... maybe. Haha
Hey Crispy,
Well done mate, looks great!
Angles look better on this on, but still no gears. Hope the goatee beard is comin' along nicely?
Linds
Old frank the first is going to turn into a retro 26inch dh bike. No photos tho... too ugly.
to you old guys out there yep 26inch wheels are retro now haha.
Btw thanks for all the positive feedback. Cheers.
How did you go racing it on Sunday? Did not see you after the finish! But looked really cool at the start line!
Bike rode well, but.. as I finished the first lap and started the second, the bike was starting to make some interesting crunching sounds...
Taking it easier for a bit and then my chain dropped of the rear...
Problem was the derailleur moved over during the race.
And the adjusting screw was not long enough to get it back over the cog...
So finished at the end of a slow second lap.
Thats what you get for not test riding your new race rig hey haha
Besides that bike road well, but I do still prefer the rigid over full squish for xc racing. I think it will become my fun jumpy geared bike.