Thoughts on Internal Shifting Hub?

Discussion in 'Transmission / Drivetrain' started by LRSimons, Oct 12, 2016.

  1. LRSimons

    LRSimons Member

    I've been running a shimano 8 speed hub on a setup I got a few months ago. I try and baby the thing, but I know at some point its going to blow up on me. I think that the higher speeds its forced to deal with would be the death of it before engine torque, but I could be wrong. Wouldn't mashing on the pedals put more torque through the drivetrain than a china girl? I know most upgrade car drivetrain parts are rated for torque- but some have horsepower ratings as well.

    Isn't the nuvinci rated for 7 horsepower? I wonder if a cvt style would be stronger or weaker than a planetary gears. The engine connected to my hub certainly isn't making 7. Id be happy with 3 lol.

    Has anyone been running one of these for a while? Reliability?

    Hope my ramblings make sense.


  2. panmines

    panmines Member

    I am glad that you ask this because I had a brand new 34t 8-speed cassette bend on me in its highest gear. Cog sets definitely have their limits.
  3. lazylightning@mail.r

    lazylightning@mail.r Active Member

    Hi! Are you guys running jack shaft kits that send power to the right side and through the bicycle chain and cogs? I'm thinking of trying a jackshaft setup. Did a cog on your 8 speed cassette bend or did the whole set of cogs go crooked? Maybe there are certain brands and makes of cogsets that are known to be better?
  4. panmines

    panmines Member

    Yes, my bike is jackshafted. It was only my largest 34t cog that bent and folded outward over the smaller ones. It was actually more of my fault because I took it up a super steep hill that I really shouldn't have and my bike being close to 100 lbs. probably didn't help it either . Interesting enough, I managed to bend it back straight with a pair of vice grips and you almost can't tell that it's bent. I do think the brand makes a difference because before this cassette (Sunlite brand), I was using a different wheel with a 7-speed Shimano mega range (14-34t) freewheel, and that thing lasted a long time and never faltered on me. Another thing I noticed is the 34t cog on the freewheel was more of a solid piece than the one on the cassette. One thing I know that would help prevent this is adding more space between the small and large chainrings in the chainset assembly. That way, the small chiainring will be closer to the center of the bike and hence more inline with your largest cog on the back wheel. Plus, spreading the two apart is something you generally want to do to avoid the chains from rubbing in your highest gear.

    A jackshaft is definitely worth the money and you shouldn't worry to much about destroying your rear cogset unless you are looking to gear it way down like I did.
  5. LRSimons

    LRSimons Member

    I'm running a jackshaft- think it's the middle priced shifter kit. As many others have said before, the jackshaft is a huge upgrade and reduces compromise. However, it is expensive and with the ~$200 (and knowledge) you can build a single speed to the same top speed/acceleration. Heck, with 200 bucks you can have whatever pipe you want, a fred head if you're so inclined, jag cdi, maybe just scrap the china girl and put a engine actually made of hard aluminum on. But IMO, the shifter bike will always be more refined.

    panmines- Wondering about how your sprocket/ cogset broke as well. Was your gearing putting a ton of torque through the thing? Any teeth shear off, or just bent side to side?

    Edit- posted a couple of seconds after yours went up. Questions answered.

  6. panmines

    panmines Member

    I was a real bummer to. Had just bought it the day before. If I money was no issue, I would put this thing on it:
    It is a 11-48t 8-speed cassette made for e-mtb. It says in the description that it was made to handle the high amounts of torque of an electric crank motor. It is kind of cost prohibitive though. With this cassette, special derailleur and trigger shifter, the whole setup come out at $580 before tax.
  7. LRSimons

    LRSimons Member

    Wow, that's expensive. Seems like the sprockets would be weak except for the largest and three smallest. Is it an electronic shifting setup? I remember seeing that on Top Gear, before Hammond stuffed it into railroad tracks.
    panmines likes this.
  8. panmines

    panmines Member

    Ha, I wish is could have saw that episode. And yes, I think this is an electronic shifting setup (motor is at the cranks, not in the hub). You're right, the in between cogs look very flimsical. I guess bike engineers want to keep the weight down on all components, but the cassette strength should not be compromised. I imagine that I would have to use the small cogs for cruising and only the largest one for serious hill climbing while using the in between ones for light duty off roading.

    Do you (or anyone) know if there is a "one up" cog for an 8 speed cassette? The only ones I see are for 10 speed and above. It would be much more worth it to use a 11-34t cassette with a 40t one up cog rather than paying $390 for this one.
  9. Gino Pi

    Gino Pi New Member

    the expensive one is made out of some material that wont bend, bottom line. too expensive for most of us, though.

    theshimaino internal hub is said to be warrantied for life, i think. supposed to be stronger than the 3 speeds. its made with hard hard steel, i think. sealed for life. the shimano... not sure which one though... but 8 speed yeah.

    i want to make a jackshaft bike. or... make what? i can do anything right now. dont like the width, though. i have a pk80 already. do i go JS.... get a 4 stroke kit?? put on a 50cc ktm clone??? i like good mpg. i wouldnt mind being able to push 50 on long flat runs... like by the beach... you know? and, i guess with the JS kit, you can start out without pedaling??? would be nice.

    the cvt... should be strong like the 8 speed. from what i heard. one of the things i dont like about both of them, is twist shifting... not sure about other types of shifters avaialbility... but i have no space for a twist shift on my bar. cvt is supposed to be ideal... im not sure. i know for sure, its expensive as heck.

    any feedback to help me understand what this JS kit all about, please let me know.... im trying to imagine... i want light. i want to make it quiet. quick enough that i wont be killed by every car. great mpg. what do you guys think??? i have the 26 inch steel frame, the pk80. need wheels... JS kit... or... what???!!
  10. panmines

    panmines Member

    I think the Jack shaft can help you get most of the things you want. You will get better mpg because the engine will be spinning at a comparatively lower rpm in high gear than it would using a stock sprocket at the same speed. For example, if your going say 30 mph with a stock 44t sprocket, your engine is turning over at about 7000+ rpm . On the other hand, in your highest gear using a jackshaft, the engine is turning over at about 5000 because you'll be at a lower gear ratio. The lower rpm the engine is at, the less gas it will use, therefore, you will get better mpg. For the same reason, you'll be more quiet because your engine is not screaming at high rpm.

    The main advantage of a js is you can get massive amounts of torque out of them while not giving up your high speeds. It is for when you want to go trail riding and a cruising on the open road with the same bike. Also, you don't have to worry about sprocket truing with the typical tag joint

    The main disadvantages of them is they can be pricey and hard to install for 2 strokes.
  11. Steve Best

    Steve Best Well-Known Member

    Hey Gino,
    I've souped up my Grubee Skyhawk with enough power to see 44mph on a single speed. I have no doubt it would have broke 50mph with proper gearing. I also had a jackshaft kit on my 50cc bike working through a conventional 7 speed derailleur. Here are my impressions:

    A properly ported and rechambered China Girl (PK80 or Grubee) will easily make more than enough power, especially with a tuned pipe (I have not even started with tuned pipes yet) to achieve 50mph with the right gearing.

    The jackshaft plates, shafts and sprockets are all heavy steel. With the chains, I found the jackshaft kit added a lot of weight to the bike, more than 10 lbs, almost as much as the motor. I kept the sprockets in close so while I did widen the pedals slightly for mine, but I could have kept the original pedals if I really wanted.
    I didn't like:
    1) having to "kick-start" the bike, but got used to it.
    2) the extra weight of the jackshaft kit,over 10 lbs.
    3) extra complication and chains to set tensions on extra chains
    I did like:
    1) no pedal start-away on hills, just release the clutch in low gear
    2) quiet cruise at low rpm
    3) noticed an improvement in fuel economy
    4) no hill too steep even with a stock 50cc

    If the jackshaft kit plates were made of aluminum and shaft kept short and the sprockets lightened and drilled you might get the jackshaft kit down near 5 lbs. The kick-start will still be required

    I am riding mostly street with my 50cc so I removed the jackshaft and am running single speed again. With a little porting and head work it does 30+mph with the 50cc and that is plenty fast on a light bike. I like that I can lift it over fences and carry it up stairs.
    Last edited: Oct 30, 2016
  12. gary55

    gary55 Well-Known Member

    I have the shimano nexus 4 speed internal on this bike. It came with the bike used, and has performed well for 1500 miles so far. I used the SBP heavy duty j shaft kit. I also bought one that was built by someone else with a 4 stroke j shafted to a strumey archer 5 speed internal. The 4 stroke looks really nice, but is a complete dog on hills. The 2 stroke bike is super heavy, but it does everything I need in a MB.
  13. Street Ryderz

    Street Ryderz Well-Known Member

    im going to try doing the pedal chopper set up for jack shaft and my own devised gearing! i just ordered form Stanton inc, 15 tooth 415 chain gear for left side,16 tooth z72 free wheel for right side.12 tooth z72 drive gear for right side,10 inches 5/8 keyed shaft,shaft collars,free wheel adapter,keys,and bearings for under 100 bucks! and here is my proposed gearing 1st just slightly higher than a stock 44 at 4.5,2nd is 3.8,3rd is 3.5 ,4th is 3.1, 5th is 2.8, 6th is 2.5, 7th is 2.4, my thinking is these ratios will give the best all around performance for acceleration,speed,mileage,longevity the only thing is im not sure how the smaller z72 chain will handle the load
  14. Street Ryderz

    Street Ryderz Well-Known Member

    how does clutch start on hills work doesnt the free wheel prevent that?
  15. gary55

    gary55 Well-Known Member

    Trying to start going up hill is a chore with a j shaft. You have to kick start it with the pedal while the clutch is out.
  16. Steve Best

    Steve Best Well-Known Member

    I edited that line to: no pedal start-away on hills, just release the clutch in low gear
    I meant moving the bike with a running engine, not starting the engine.
  17. gary55

    gary55 Well-Known Member

    Hay Steve.Been thinkin a lot about that squish band stuff. Checked out how the piston relates to after market heads.. From what I could round out with using h/2+w2/8xh=r it worked out to the piston being at a radius of 3.60" and the head cut at 11 deg.. The piston marked with a sharpie would only touch at the half way point on the squish band which led me to this wonder why. A radial surface and a straight cut surface. See what a picture of sand paper glued on top of a piston leads to. It's all your fault. Watch out for them bobcats.
  18. Street Ryderz

    Street Ryderz Well-Known Member

    Hey Gary you use a jackshaft kit do u use a regular bicycle chain on drive (right)side? and has it held out out well ?
  19. KCvale

    KCvale Motorized Bicycle Vendor

    Good single speed 410 chain works well for internal shifting hubs, 7-speed chain works but you need to use some finesse when shifting as a bad shift can break the thin chain.
  20. Steve Best

    Steve Best Well-Known Member

    I've used regular 410 chain for both the jackshaft kit sprockets and for the primary drive off the motor.
    I also use it for the single speed kits. As you know, the final drive takes the most torque.
    If the thin 7-speed chain can handle the final drive, there is no problem with 410 chain.

    I suspect the guys using 415 and 41 chain are compensating for inadequacies in other areas! :)

    Seriously, the 410 chain offers significant advantages in economy, weight, centrifugal effect and wear on other components. I like KC's analogy of using a ship's anchor chain for a dingy. 410 (BMX or single speed bike) chain is available at any bike shop ($10) and more than strong enough for our application.

    Like KC mentioned, a rough shift with a derailleur shifter can damage the chain and sprocket teeth.
    I had a few rough shifts where it jumped as I opened throttle and could see the effect on the rear sprocket teeth.
    More power causes more damage.