[hpv] 2WD Deltas

[Mark Stonich]

In a different thread - On Dec 22, 2013, at 8:51 PM, John Tetz wrote:
> I'm working on a Delta trike design and would like to incorporate a two 
> wheel drive.

My winter trike has a 2WD system where the outer shell of an 8/9 speed freehub body is rigidly attached to the middle of a jackshaft. BMX freewheels on the ends of the shaft transmit power to the rear wheels. When turning, the freewheel driving the outer wheel freewheels. when one wheel slips, the other gets the power.  

Due to the lightly loaded front wheel, (20-40-40 weight distribution) and the fact that the inside wheel gets the drive in turns, I expected the front wheel to plow in tight, low speed turns. It does so on clean lake ice or a rink but street ice is never as slick. The reason it grips so well I attribute to the 54 degree head angle, which causes the tire to be banked into the turn. A bike tire leaning into a turn will always grip better than one that's perpendicular to the surface.   

I was on a tight budget at the time so built it almost entirely of stuff I had lying around. Wheels are just conventional MTB wheels with rim brakes. So I had to support both sides.   

If I were doing another winter trike I'd use 700 - 32 rear tires to better cut through the snow, either cyclocross or studded. The jackshaft would be much shorter and single sided wheels mounted on half shafts with inboard disk brakes.  Frame could be much simpler and lighter.  For a summer trike, smaller, right wheel drive and 20"x2.35" Big Apples at 30 PSI

http://bikesmithdesign.com/MyBikes/2wdTrike/jackshaft3.jpg  Half size

http://bikesmithdesign.com/MyBikes/2wdTrike/jackshaft2.jpg ull size


Freewheels mount on fittings I bought from Lightfoot Cycles. Just bolted through holes drilled in the 3/4" x 0.120 jackshaft. Lightfoot must have liked the idea because they came out with 2WD a year later.  Right wheel has a single cog mounted on a cassette body that had been locked with a bit of welding.  There is a 3rd bearing behind the cassette.

http://bikesmithdesign.com/MyBikes/2wdTrike/fairingside.jpg

66" wheelbase is to limit weight transfer off the front wheel and to get it out in front of the fairing.  54deg. head angle and 5-3/4" of rake gives 3/4" of trail. I would never have that much trail on a 2 wheel 'bent, but I wanted feedback to let me know how much grip I have. Front tire is a 20"-1-1/8" knobby.

Inner skirts on the fenders keep salty snow off the secondary chains.

 Mark Stonich;    BikeSmith Design & Fabrication
   5349 Elliot Ave S. Minneapolis, MN 55417 USA
      Ph. (612) 824-2372   http://bikesmithdesign.com