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Old 03-23-2014, 02:36 AM
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BarelyAWake BarelyAWake is offline
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Join Date: Jul 2009
Location: Maine
Posts: 7,212
Default Re: How weak is Your weakest link?

Originally Posted by Going2Hell View Post
Yeah, I was looking into a jackshaft for this bike. When I was putting together my parts list, the jackshaft for the Huasheng was a questionable part to me. I've seen the modifications required to get some to work with a Chinese shaft. A few months later SBP came out with it.

How does your jackshaft do? On a scale of 1 - 10 where would you put it in reliability and helpfulness in pulling a load?
On a scale of 1 - 10 I'd put this jackshaft square on "null vote" in that you've inadvertently asked a trick question, it's not actually needful with this particular build. Due to the torque characteristics of both a four stroke & an electric assist I hardly ever shift the thing at all & if I do, it's with the Lifan's primary 3sp autoclutched gearbox, a real internal transmission known for durability & longevity - designed by Honda & copied by Lifan, I can't take any credit lol

This particular jackshaft setup is specifically for fine ratio adjustments to maximize efficiency - but not like you'd shift a car or motorcycle. It's for either setting up for major changes beforehand like trails vs street, high speed vs low speed cruise and trailer & cargo vs unladen (3sp primary) or extremely minor "in flight" adjustments in ratio to decrease cruise RPM (7sp final).

Here's a quick vid of the jackshaft itself:

So the Lifan's 3sp is like the high/low range in a 4x4, the final seven gears of the rear cassette only to set cruise RPM, at most I may shift those twice on any particular run, to fine tune cruise or to adjust for extremely hilly terrain & back again - but usually as it's already set in the cruise ratio from a previous trip, so I'll pedal assist some on take off & just leave it be. Having the jackshaft also allows me to use any 26" rim w/cassette as a replacement rear wheel should the hub fail or I taco the rim, unlikely but I've also left the rim brake bosses on the stays when I converted to disc, also enabling me to use just about any wheel & brake combo I can find.

The components are nevertheless still being used all the time whether actually shifted or not yet they've proven quite reliable, some of the critical differences between this DIY jackshaft & the commercially offered shiftkits are also with this in mind. With this all the components are inexpensive & commonplace, for example the pedal chain freewheel is a BMX part, responsible only for the pedal drive and on a round 5/8" keyed shaft, sealed bearings pressed into the cylinder of a bottom bracket, all assuring proper centering. I had no end of difficulty with the long-term reliability of the commercial shiftkit's pedal crank freewheel, expensive with limited availability when it fails you've no drive at all, pedal or engine. This DIY jackshaft was also designed so all chains are properly & automatically tensioned regardless of suspension compression or chain wear, so there's little to no maintenance and no adjustment required. As the jackshaft is housed in what used to be the bottom bracket for the rear stays, it's so rigid & sound there's no movement at all, the side plate flex of the aftermarket shiftkits another issue I experienced, the fatigue & strain causing additional long-term reliability issues.

Don't get me wrong, the "shiftkits" are fun & an easy way to get gears, they're just fine for many bikes - but for this build the demands are greater in torque & cargo weight and given it's for long distance use, reliability & redundancy is of paramount importance. Should there be a failure I also need to be able to get a replacement part easily from the local bike shop or hardware store, I don't wish to wait two weeks or more for shipping at some random rest stop somewhere lol

Originally Posted by Going2Hell View Post
Looking forward to seeing more of this Hybrid tech in the future. As soon as you can charge your batteries from the motor, I'm in too...
This build does trickle charge the batteries both from the Lifan's lighting & charging coil as well as regenerative from the rear hub - while still technically a "plug in" hybrid, I've not managed to run the batteries dead yet, even during a three day camping trip & associated use without external power. I'm sure it's possible as all I'd have to do is not use the four stroke & run around on electric only - I sometimes do this anyway, but not till the batteries are dead lol

The Lifan has a tiny 12v SLA (starter) & the hub drive's batteries aren't particularly huge, it's just a 36v 10ah LiFePO4 pack in one of the two front trays (other tray has chargers, converters & associated electronics) but both the charging systems & batteries (12 & 36v) maintain each other's charges if they've the voltage to spare, this also means my lighting will work even if a battery fails as it's all through the 12/36v converters anyway. The converters haven't enough amperage for the Lifan's starter motor, but I've also a kick start and I can pedal start... so yea, that redundancy thing "again" heh

LiFePO4 pack;
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