ITR060
INTO THE RIDE #60
A Crankforward for the Taller Rider
and
Proposal: A New Standard Recumbent Seat Mount
by Randy Schlitter
A Tall CF
We have started test riding a tall-rider version of the Dynamik. The bike has a 3” longer wheel base over the Dynamik (52.5” Note: The Fusion is 53.5”). With a longer seat tube by 3” the inseam range extends to 30” – 38.5”. This should accommodate most riders in the above 6’ or greater range. You will have to subtract 3” to reflect the correct setting. Example: if your inseam is 32” set the post to 29”. The wheel base was increased to keep the front wheel more weighted, even when the seat is at maximum extension. For a rider my size (32”) the bike feels very balanced, and much harder to pop a wheelie. Cornering is excellent, another component of the front loading, so overall the handling is excellent. The only down stroke is less crank clearance, a natural outcome of longer wheel base. That will show up on the trails, and from my experience with CF on trails, it is manageable by bunny-hopping over obstacles, instead of hoping you have clearance.
Ric, our Purchasing Agent, is 6’3”. The bike fits him perfectly, and he reports excellent cornering, traction in steep climbs, and quick turn response, even with a more dampened feel in steering.
The frame features other subtle changes, such as the seat stays, and top tube placed higher on the seat tube. This increases the stiffness of the cantilever seat tube portion, and may contribute to the ride feel being very solid. The tall version of this CF should be available in limited production starting in late March or early April. The project has been dubbed the Sequoia (after the tallest trees on the planet), and may or may not be the final product name. The first issue will be steel frames, meaning about a 33-pound bike with Dynamik spec, and an aluminum version will follow late 08’.
A Standard Recumbent Seat Mount…the Cross Pin System
How about making the standard spacing for mounting a recumbent bike seat 2.75 in width, and use .375 diameter mounting pins, and cross pin to them? A standard spacing alone would help, but if everyone adopted the pin-attach system we are going to be using on the F-5 and future bikes, seat swapping and aftermarket seats would appear and blossom.
We call it the Cross Pin system. The concept features two attach angles or tabs that are thick enough to boss a 3/16” quick pin. This means easy on and off seats. It also means your seat clamp can stay in place. The seat clamp itself is whatever you need to attach to a given frame shape, and as long as you use 2.75 spacing and have the attach pins mounted to the clamp, you’re good to go. The beauty of this system is how easy it is to design the pins into a bike seat clamp, and it allows for seat tilt. For example: we will be offering a conversion kit for the Bacchettas Euro Mesh and standard mesh seats. The kit comes with two angles, two bushings and takes only a few minutes to install. You can see a video of this on youtube at www.youtube.com. The kit will be available in a few more weeks direct from ShopRANS. For Bacchetta (and others with similar mounts) to make this standard would be peanuts, just a simple change to the existing mounting angle, and either make special longer-headed round head bolts or use bushings. On the test bike Brother John loaned us, we used the existing bolts machined down in diameter with bushings. Our system will eventually use the long head bolt at the right diameter to serve as the mount for the slotted angles. We will be happy to vend this to the industry. The current seat mounting angles are costly since they are machined from solid bar, but we will eventually forge them to drive down cost. If everyone uses the same one, it will also create common bolt patterns on the seat bottoms in most cases other than composite seats.
At ShopRANS you can order a kit to convert your Bacchetta, fits on the standard and Euro mesh seats, and if enough call for, we will make it work on the composite seats.
This is the prototype system used on the Xstream. It has been working great; fits tight, even after many an uncoupling.
We have applied for a patent on this system but will be happy to share it for a very small price, since our main interest is to promote a standard seat-mounting system.
The tall CF is an exciting project, which we hope will allow many more people to enjoy the fun we’re having on the CF’s. And to be able to create a standardized seat attach system, well, that can only add to the fun of cycling too. In either case we hope it helps you stay into the ride!
