Charles Brown: Thoughts on recumbent bicycle design

By Charles Brown, Southfield, Mich. 

      I started building recumbent bicycles in the early 1980s.  Back then, everyone was building long-wheelbase recumbents, and I became enamored of the design. 

      I think most unsuspended short wheelbase recumbents have too rough a ride.  I built three SWBs with front suspension; all climbed hills slower than unsuspended bikes. 

     The pedaling motion seems to activate the suspension, so not all power goes to the back wheel.  Some people claim to have overcome this, but don’t seem to have measured it. 

     It seems to me a front wheel that moves straight back when you hit a bump might work. That is, it would take longer for the bike to rise up over the bump, smoothing the ride without a real suspension. It would give a smoother ride by acting like a bigger wheel, yet not be affected by pedaling forces. But I haven’t tried it yet. 

     Tom Traylor’s moving bottom bracket designs also give a good ride with short wheelbase.

     Having pretty much given up on suspension, I worked on modifying the usual long wheelbase bike.  I raised the bottom bracket to get the rider in a more aerodynamic position.  This also gave some room under the cranks to push the front wheel back, shortening the bike and getting some much-needed weight on the front wheel.  The resulting bike isn’t too much longer than a short wheelbase.

       This drawing shows what it would be if I did it over again.  (As a serial HPV builder, I can tell you the next one is always going to be perfect!)  (Editor's note: This drawing does not depict the bike under construction, shown in the final photo.The drawing shows what will be the bike after that, which will incorporate additional changes and a different front wheel.) 

       I’ve built many generations of this design.  Earlier ones used the front fork from a 27-inch wheel road bike, and I always wondered why the steering was never quite right.  It turns out that even though there’s less weight on the front wheel, the shallow steering angle puts more stress on the front fork, causing it to flex.  

      This was cured by using a shorter, stiffer fork.  I give mine more rake by sawing notches on the top, bending them, and welding them back together. 

Charles Brown at the 2022 Michigan HPV Rally. Look close at the front fork and you can see where he modified it by cutting and bending to give it more rake.

       The drawing shows how I’ve been making all my steel frames lately.  A main tube, only about 1-1/2 inches diameter, handles all the torsional and lateral loads.  Some very light truss work underneath adds strength in the vertical direction.  If you put the tube that goes from the head tube to the bottom bracket at just the right angle, the tube bends neither up nor down under pedaling forces.  More information on this and related topics in my articles posted Dec. 3, 2015, on www.recumbents.com.

Here's Charles' latest, under construction, which will use components off his 2022 bike, but is 3 pounds lighter than that bike.  He plans to race it at this year's Michigan HPV Rally.

       I believe a narrow, high pressure front tire improves the steering on a long wheelbase recumbent.

       I’ve built over 50 different recumbents, and like to delude myself into thinking I’ve learned something over the years.  This isn’t a bad design.