Sturmey-Archer jackshaft setup

[Michael Fox]

I just finished converting my bicycle to a homemade jackshaft with a sturmey-archer 3- speed transmission and I love it. I bypassed the pedals and use them for foot rest. I geared it for the motor gear 10T, 24T on the jackshaft input, 10T on the jackshaft output, 18T on the rear wheel gear. My calculations show that first gear is equal to running a 58T rear gear, 2nd gear is equal to running a 43T rear gear, and third gear is equal to a 32T rear gear. First gear at 6000 rpm should give me 20mph, 2nd gear 27 mph, and 3rd gear 36mph. I love how smooth the bike rides without the necessity for a chain tensioner and pedals. The bike freewheels until the rear gear speed surpasses the rear wheel speed. The bike pulls very good from a standing start and pulls hills real good. I am able to get around comfortably and fast without screaming the engine. I am not sure how reliable the transmission will be but I have three transmissions that I got off of old bikes and I am going to become an expert at rebuilding the transmissions if necessary because I can't go back now. One thing I didn't consider was when the bike rolls it freewheels so it will not jump the motor off. I had to install a pull rope but it works well so far.

 

[Sidewinder Jerry]

Gears are great. Mine shifts 5 gears automatically.

 

[BarelyAWake]

... I am not sure how reliable the transmission will be but I have three transmissions that I got off of old bikes and I am going to become an expert at rebuilding the transmissions if necessary because I can't go back now...

The 3sp SA IGH makes for a great jackshafted multspeed, I've run the SA X-RD3 for thousands of not-so-gentle miles without any issue. I greatly prefer the IGH over the cassettes for nice, clean shifting every time with little to no maintenance

There have been some few, scattered reports of older, reused hubs failing... but I suspect that's simply a case of unknown previous use & abuse - jus' don't "slam" it between gears (speedshifting/not matching RPM) and it outa serve you well.



You may well be aware of this but you needn't forgo the pedals or spend big money on commercial setups, if you've already built a DIY jackshaft you're likely pretty close to something like this anyway: http://motorbicycling.com/showthread.php?t=12284 (chk whole thread, it evolved). I adapted the concept for another build, it's essentially just 5/8" keyed shaft, a coupla bearings, stop collars, sprockets & a "BMX" style freewheel cog - there's no specialty parts & it's pretty straightforward;

http://youtu.be/U10xLqTekOw

...as that one is on a tadpole trike, I could use the rear stays' bottom bracket with sealed bearings pressed in, Russell's (linked first) is the same thing just with pillow block bearings.

Welcome to the place BTW

 

[Michael Fox]

Thanks
That looks great and I appreciate finding out that the 3-speed has given good service. Attached are some pictures of my setup.

 

[BarelyAWake]

Very nice! I love the vintage touch & that's exactly the DIY jshaft type I love so much lol

...and if you're interested, a freewheel BMX sprocket looks like it could be incorporated between the jshaft to hub chain & outside pillowblock, a chain added from the freewheel to a crankset - though admittedly there may not be quite enough enough room as-is.

Here's a coupla links, no worries if it's not something you're interested in - I jus' like havin' a back up drive/pedal assist & don't much like bump starts;

freewheel/shaft adapter: http://www.staton-inc.com/store/pro..._sprockets_1_10_wide_2_set_screws-986-25.html

freewheel: http://www.amazon.com/Odyssey-13t-BMX-Freewheel-Threaded/dp/B000VT3ZCU

 

[bigoilbob]

Thanks
That looks great and I appreciate finding out that the 3-speed has given good service. Attached are some pictures of my setup.

Great lookin', and I can't stop thinking about doing this myself. I would only use 2/3 ranges, as an overdrive for my GX35/18.75/1 Staton/NuVinci 171 Developer's Kit set up I have on my Bike E2 recumbent. This is in spite of the better, common sense suggestion by LR Jerry that I just buy a GX50 and resprocket.

But ONE problem I would have would be sprocket placement. (1) How are the output sprockets mounted, in general?, and (2) would it be possible to mount the output sprocket just 2+ half chain widths from the input sprocket?. Not asking for spoon feeding, but I clicked all the links (and checked other threads) and have not yet found any welding free work processes for this.