Jackshaft Advice on IGH as a jackshaft 4 my bikee e2 recumbent, already with GX35 and Nuvinci?

Discussion in 'Transmission / Drivetrain' started by bigoilbob, Sep 1, 2013.

  1. bigoilbob

    bigoilbob Member

    Soliciting advice, and candid comments on practicality. My overlong videos and explanation of my bikee e2 with a GX35 and a Nuvinci Developers kit are linked.

    The bike has been great, taking my wife and I all over south St. Louis this summer. It's fun squeezing thru traffic at crowded summer outdoor events and parking close to the action. What I would like, in addition to the hill climbing ability and automatic transmission is an overdrive and underdrive. Even though the bike is heavy (well over 100#) and poorly powered (GX35 thru a Staton trihybrid gearbox and Nuvinci hub), it has very little drag or wind resistance. So, even with 2 aboard, on level roads we rev out at ~19 m/h and the tiny engine spins freely. I think if I had the 33% overdrive of, say, a Sturmey Archer 3 speed IGH, acting as a jackshaft, we would be safe at ~25 m/h. I could also winch up ~24% grades, up from ~18% grades now, with 2 aboard, in the "underdrive" low range. I have a great IGH mounting point on my heavy outboard motor mounts (visible in videos), and the Nuvinci hub freewheels, so no problems there.

    I would like forum input on;

    * What would be the best IGH? The SA seems strong, especially if I transmit the power at a higher r/m. But the Shimano 3 speed has an available electric shift, and I have a constant 12 volt power source.
    * Does the 90-95" distance from my left hand grip (preferable shift point) to the IGH mounting point make the installation impractical?
    * Are there any kits or other cheats a non welder could employ to install the second sprocket?
    * Post mortem assessments from anyone who has tried this, on any MB.

    Not that worried about $. I have about the same brains/money ratio as Jay Leno, if at a much, much, lower level.

    Thanks, and don't hold back if it's a really stupid idea.


  2. bigoilbob

    bigoilbob Member

    No response, so I think I might have done a poor job explaining myself. Let me try this. Has anybody installed the sturmey archer/station hub kit http://www.staton-inc.com/store/pro...RIKE_HUB_CB_CONV_KIT_STURMEY_ARCHER-84-0.html on a bike. These, on trikes, are functionally "jack shafts".

    The idea would be to cruise most of time in "2" (1/1 input/output ratio), using the NuVinci auto shift, with it's ~3.6/1 low/high spread. When I was on smooth, level road, go to high (0.75/1 input/output ratio), and when in San Francisco and the need arose, got to low (1.33/1 input/output ratio), admittedly torquing hard on the Nuvinci hub.

    Interested in opinions, experiences. Anything would be appreciated.

    Separately, a FYI tip. Do NOT buy a Staton gearbox without the available ~3/8" diameter high strength mounting pin. This is not well explained in his product descriptions - unusual for him. Took me 2 sheared pins to write Staton and get wised up. I even dug my 35 year old mechanics of materials text out of the basement and did the arithmetic from a free body diagram ('member them?). "Duhhh, that Dave Staton ain't so dumb after all....".
  3. LR Jerry

    LR Jerry Well-Known Member

  4. bigoilbob

    bigoilbob Member

    See your point, LR. 70% more torque, 60% more power, for less than 5# extra. I had thought about it, but was concerned about over twist on my NV171 hub. At 1.3 lb.*ft. of engine torque, 18.75/1 Staton gearbox reduction, a 13 tooth gearbox sprocket, and a 27 tooth hub sprocket, I am at ~51 lb*ft hub input torque. Doesn't account for losses, but they are not big when just starting the gearbox turning. The NV171 hub is rated for 48 lb*ft steady state hub input torque, and I am often close to that. But going from a 13 to about an 18 tooth gearbox sprocket would keep me "sort of" in the safe zone. A little harder on the clutch, but probably ok, as it now engages at less than 3 mph. Best part of your idea is no increase in moving parts.

    Leaving for a couple of "post retirement" month on/month off rotations in Kurdistan as soon as the visa comes thru, and the lovely Ms. bigoilbob let's me keep some of those $ for blow money. Thanks 4 a great me gift idea!
  5. LR Jerry

    LR Jerry Well-Known Member

    Here is my current ratios. Gearbox 18.75, GB to shiftkit 18-44, SK to rear freewheel. 34 (34, 28, 24, 20, 16). I use a Robin Sabaru EHO 35 engine at 1.2 ft/lbs at 5000 rpm. So my current reductions are (45.83-21.57):1 at 55ft/lbs in low gear. When I upgrade this will be my ratios. GB-SK 22-44. I'll change the 18 gear to a 22. This will be my reductions (37.5-17.65):1 at 70 ft/lbs in low gear.

    I use 26 inch wheels so that's why I need the lower reductions. In your case you have smaller wheels but much more weight. I'm just happy to see others building autoshift systems.
  6. bigoilbob

    bigoilbob Member

    LR, since we're in the weeds with torques and such, I feel the need to brag about the one thing I have (and need to have), push. In addition to my input hub torque of ~50 ft.*lb, I have an additional starting reduction of 2/1 through the hub, giving me about 100 ft.*lb. Since my powered wheel rolling radius is a puny ~9.6", I get pushed at ~125# to start. Would be interested in others with comparable starting thrust.

    Now, point well taken about weight, especially with 2 aboard. And I'm indeed a slow poke, maxing out at 19-20 m/h. Not even mentioning that my efficiency is 5-10% less than yours. All told, I like my bike, but your system is (1) way under appreciated, and (2) the wave of the future.