Continued development

[Bikewer]

Of my home-built. I realized that the derailleur-cage chain guide wasn't going to cut it; it was noisy and I didn't trust the plain bushings on the rollers. So, I constructed this:

http://im1.shutterfly.com/procserv/47b5d827b3127cce925d3bb088bb00000016108AcNGzhu3bNn

Using the roller-blade wheels and a fabricated aluminum cage. At about the same time, I decided to do away with the dual-chain, dual crank setup. Not only unduly complex and heavy, but I couldn't get the gear ratios where I wanted em'. (too low overall)

So, as you can see in the pic, I routed the top run of the chain through a 1/2" tube, after reading up on this dodge on the homebuilt recumbent database. Seems to work very well; quiet too. At present, the original crank is only functioning as an idler. I plan to remove the whole thing and use either another tube, or another skate wheel.
The original skate wheels, obtained from a pair of cast-off 'blades, proved too soft. (74 durometer) The drive-side roller failed after about 20 miles. I have since obtained a pair of 88+ durometer wheels, which are the recommended hardness. These have proved much easier to "machine" as well, using my jury-rigged drill arangement.
Right now, using all three front chainrings, I have a pretty useable gear range. I think I can refine this further with a compact crank, if I can find one.

All this is functioning as a test-bed for version 2.0, which will use an aluminum Y-frame as it's basis. I already have that frame, but I have to strip off all the junky steel parts.
I have my eye on an old Raliegh "technium" roadster, which may furnish the boom assembly. Refining the unduly-heavy seat and stem assembly should bring me into the 30-pound range.

[johntolhurst]

Hi Bikewer,
glad to hear you are going to the y-frame on the next one, it will put your seat down just a bit lower and give you better braking ability and lower centre of gravity. Will you go for the front shocks?

When you pedal will the chain tend to compress the suspension spring, giving a pogo effect and absorbing precious energy? Maybe the drive side chain can be routed over an idler positioned near to the pivot point of the unified rear triangle?

Good luck with your building! :)

John
cruzbike.com
building bents from Y frames

[Bikewer]

I will probably, as on this one, junk the heavy, cheesy "suspension" forks on the frame I just got. They are absolute junk. Hopefully, the Cro-Mo forks I have on this one will fit. The only problem is the front brake, I may have to shop around for a long-reach dual-pivot caliper.

I was a little leery of the suspension rear end. That "shock" is, of course, little more than a spring holder; there's no damping whatever. Still, it does seem to work pretty well, and I havn't noticed any pogo effect under hard pedaling.

Still, On version 2.0, I may make the rear end rigid (by means of a solid spacer to replace the shock) so as to use the rear-dropout eyelets as a support for the seat I have planned. The seat assembly on this one is really heavy, though suprisingly comfortable.

[johntolhurst]

Hi Bikewer,
the seat and the rear suspension are connected, I've found. With the shock working, your seat will be surprisingly comfortable as its not having to cope with any real jolts. If you cancel out the rear suspension, you will be asking for more performance from the seat. The cruzbike seat weighs under 2 kg, including fixings and performs well on the y frame bike. On a bike with no suspension it is still comfortable but the large bumps do force you to tense up. The seat does not require the usual stays, but is directly supported by the seat post via the usual seat post clamp and a long pair of saddle rails. This means the rear unified triangle is free to provide the suspension http://www.cruzbike.com/seat/index.html

On these cheaper y-frames, I agree the shocks are not the best - however I bet they work better than the pantour suspension hubs (apart from their weight). For a road bike, I've found they work quite well enough and allow you to use 100 psi tyres without getting such a harsh ride. We put 100 psi tyres on the front and back of our cruzbikes.
John

[Bikewer]

Thanks for the info! I have the Cruzbike page bookmarked, in fact, and I didn't realize you marketed the seat as a seperate item.