New Build Question Sturmey Archer/Jackshaft

Discussion in 'Frame Mounted Engines' started by Mike St, Jun 3, 2011.

  1. Mike St

    Mike St Member

    I'm thinking about a new build, combining a Sturmey Archer hub/internal brake with a jackshaft and 2 stroke shyhawk gt5 engine. The hub has three gears. Here it is:
    The question is would this setup have better low end power from a standing start than the grubee g4 or q-matic automatic? I wish to pull away without pedaling.I can't find any videos with this drive train. Mike

  2. wheelbender6

    wheelbender6 Well-Known Member

    Some have said the 3 speed Sturmey isn't durable under engine power. I have no personal experience with it.
    IMHO, avoid internal gear hubs (Sturmey, Sachs, Nexus, Sram) and use a derailleur with your motor and jackshaft. It's must cheaper to replace the worn or broken parts on a derailleur setup.
    If you do not have a derailleur hangar on your frame, you can go with an axle mounted gear changer.
    I do dig the internal geared hubs (I have a Nexus on my pedal powered beach cruiser). I just question their durability and repairability when used under engine power.
    Last edited: Jun 3, 2011
  3. Mike St

    Mike St Member

    WB, I appreciate your opinion. Mike
  4. Mike St

    Mike St Member

    I'm slowly turning off on the Grubee Gt5 66cc 2 strokes as I have read too many complaints about finicky carbs, starting, throttlling problems, blown engines, all having to do with the changes grubee made in the latest 2010 line of his 2 strokes. My HS 142 4 stroke is perfectly reliable, easy starting on one pull with no carb problems at all. Why would I take a chance on a 2 stroke?
  5. rustycase

    rustycase New Member

    SA vs CVT


    There is NO WAY a china 2 stroke will put out the torque that a healthy pedaler can apply to the drive of a bicycle. No way, No how. NOT gonna happen!

    Conventional wisdom declares that if you wish to pull away from a stop with enthusiasm, a HF 4 cycle engine with a Comet Torque-A-Verter is the ticket.

    We're in the fun zone...
    I've got three Sturmey-Archer hubs here and WILL play with them, because I HAVE them. And I'll look forward to seeing the posts on your build !
    Next time I see a couple hundred bucks to spare, I shall get the CVT drive system for my 6.5 greyhound, because that IS the way to go.

    Don't take MY word on it, review Cobrafreak's thread, and others!

  6. Mike St

    Mike St Member

    Well of course a 6.5 4 stroke with a cvt gets the job done. CVTs are the best solution but they are difficult to mount inside a bicycle frame. I've only seen rear mounting with them. They are also too wide for in/frame mounting, so I don't see cvts as a practical solution for motorized bicycles unless you're happy with a ton of weight sitting on the back fender.
  7. pbeggs

    pbeggs Member

    i run a S/A 8 speed internal gear hub with a jackshaft
    works well
    drum brake is very good,.. works well

    one advantage of the internal gear hub is a static chainline,.. and no need to downshift as you slow (to goes from 8th to 1st in one twist) also you can run heavy chain to the rear wheel
  8. 5-7HEAVEN

    5-7HEAVEN Guest

    There's more than one way to skin a cat, and more than one way to pull away from a stop with enthusiasm.

    You don't need a 6.5 hp engine, either. It's all about mechanical advantage/leverage/low gear to harness engine or leg power. That is why a healthy pedaller easily pulls away from a stop.

    From how my friend Hawaii Ed operates his china 2 stroke engine with shift kit, it is easy for him to pull away from a standing start.

    I have a 2.8 hp Tanaka 47R engine with a shift kit. It makes as much power as a healthy China engine. I seriously doubt that a bicyclist will beat me from a standing start to the top of first gear.
  9. 5-7HEAVEN

    5-7HEAVEN Guest

    I've never ran a 3-speed hub under power. The hub mentioned has gearing which range from 22t to 13t. The eight-speed cassette ranges from 34t to 14t. The 22t in the cassette's cluster is about third gear.

    Therefore, using a 3-speed hub is like starting out in 3rd gear with an 8-speed cassette. However, gearing on an SBP shift kit can be as low as 34.49 at the chainring. First gear with a 34t cassette is a stump-pulling 32.57:1

    A China engine with this gear would leap off the line at a standing start.

    With your 3-speed hub and SBP gearing, first gear with 36t chainring and 1.33:1 = 28.03:1, second gear = 21.07:1, third gear = 15.81:1.
    With a 30t chainring, first gear = 33.63:1, second gear = 25.28:1, third gear = 18.96:1.

    You will have excellent power from a stop with 33.63:1 and okay power from a stop with 28.03:1.

    My new cassette and derailleur cost less than $80. It is not a heavy-duty, bulletproof, top-of-the-line model. I have broken many chains until I solved that issue.

    However, the Shimano cassette and derailleur have endured through powershifts and abuse for over a year. I inspect them regularly, and they show no signs of abnormal wear.:detective:

    I am simply amazed by how OEM drivetrain components live reliably under the abuse of motorized power.:bowdown:
    Last edited by a moderator: Jun 4, 2011
  10. I have a 5-1/2 hp Chinese industrial engine, Jiang Dong, on a Monarch bicycle driving through a S/A jackshaft and it seems up to the challenge. It used to do 42 flat,41 uphill,41 downhill on the governor at 3100 rpm. I replaced the carb with one from a Lambretta scooter and went with a straight exhaust and junked the tank, replacing it with a Hodaka one and did away with the governor. The thing is a lot faster, but speedo quit, so dunno. Gobs of pullaway power in grass in low. No peddles anyhow. I did have to run a 2nd jackshaft due to the wrong drive direction of the tranny. It also freewheels. I use the rope starter. That brings me to why I even got into this forum in the first place. I have a couple of ho hum China Girls and got a wild hair to play a creation game by mounting a couple 1" tubes on an engine and adding until it looks like a motorscooter with 20" bike wheels. I need a rope starter for a China Girl. Seems like there was such a unit available. I was kinda impressed with a 50cc Honda scooter I saw yesterday. Open frame thingy. Kinda cute.
  11. rustycase

    rustycase New Member

    Of course you are right, 5.7, Many ways to skin a cat, and that's part of the fun of it.

    Certainly do not need the 6.5hp. But for $75 I could not pass it up.
    I figgered if it's got that much in it's powerband, it should do well for normal MAB use when at lower rpms.
    ...I was real pleased to see the general reviews on the engine have been quite good, almost everywhere I've looked.
    With a CVT, I think it would be optimal for reliability, and response.

    5.7, I looked for a sprint record but couldn't find one, so far. :)
    I think it would be a fun race!
    Your low cog would probably zip out real fast, right?
    I was hoping to find a 100yd sprint time for a bicycle racer, but no luck.
    I did find a 83mph record for undrafted on level ground, though. There's a bunch of crazy records in the wikipedia... like downhill off a volcano at over 100mph ! LoL

  12. 5-7HEAVEN

    5-7HEAVEN Guest

    LOL, I know what you mean.

    I bought a new 6 hp Robin engine on ebay for $100. I just couldn't pass it up, and it'll be one of my projects in the future.

    I'm swapping the 63t chainring to a 72t sprocket, as we speak. That'll lower first gear from 32.46:1 to 37.09:1
  13. rustycase

    rustycase New Member

    Wow! 37:1 !

    That's gonna pull tree stumps, 5.7 !

    Actually I know very little about proper ratios for a specific effect. Must read through all the threads on that topic, soon.
    One thing I considered is that it's probably possible to rip the spokes right out of a rim, or hub.
    I did read the thread where a fellow named CAM fastened his driven sheave to the rim itself using a bunch of bent-up brackets he fabricated and screwed directly to the rim. He's built a replica BTR with belt drive.

    Anyhow, since I've got these Sturmey-Archer SA hubs, I'm considering if I should weld ears directly onto the hub to fasten the sprocket to. I'll need to take them apart for inspection, anyway, before making any decision about actually running them... I could weld on them when they are cleaned out.

    Does anyone know where to get that cute little chain that is used to shift the gears??? :) I could use a foot of it.

  14. Mike St

    Mike St Member

    5-7, I studied your response on gear ratios and what I get from it is, although the SA 3 speed can work, it doesn't have enough gear ratios, so I would buy an SA 5 speed or eight. I'm more bothered by using a 2 stroke engine, which I have read nothing good about, too many problems, very finicky whereas my 4 stroke HS 142F is perfectly solid, reliable. So what is the solution here? A four stroke with the jackshaft and SA? Appreciate and comments. Let's find the best power system.
  15. rustycase

    rustycase New Member

    Which of the selectable hubs is the most robust? I think that's the main question...
    I recall skipping in and out of a gear when I was a pedaling kid!
    We didn't like 'em then, for that reason.
    Now that I've seen the fix, in repair threads, maybe that's OK, but I'm concerned they will get damaged too easily when under power.

    I've got to read through the jackshaft threads to find out which is best way to go.
    Seems it could mediate the need for a chain tensioner by shortening the final drive run.
    If the jackshaft is a Sturmey-Archer hub, that's good, too!

    Anyone have comments on that application?

  16. 5-7HEAVEN

    5-7HEAVEN Guest

    The low gear is on the bike. I'll know how well it works soon, when I ride to town today.

    I have absolutely no problems with my wheelset, which I inspect after every ride. They are aftermarket aluminum rims w/32-spoke, 14g stainless steel, still true, aluminum rims, which I've used for a year. No signs of wear and tear.

    Three-speed hubs will work, theoretically. However, the gear spread will be wide.

    It's like installing a three-speed transmission, compared to a one-speed tran or an 8-speed transmission.:detective:
  17. 5-7HEAVEN

    5-7HEAVEN Guest

    Unsure how strong SA 3-speed hubs are. However, it's like having a 3-speed transmission versus a 1-speed sprocket versus an 8-speed transmission. The SA will have a wide gear spread. If you have a very low first gear, you will also have a comparatively low third gear too. With an 8-speed internal hub or cassette, you can have a stump-pulling first gear and a freeway-flying overdrive 8th gear. Heck, you might not even need to use several high gears. On my present setup, I only use the first 5 gears.

    If I were me, I'd set up for a shift kit and an 8-speed cassette.

    Mike, since you have the HS 142F, use what you have. If you have the SA, go for it. If you have a cassette, use it, whether 5/7/8/9 speed. I really enjoy the 8-speed. It is cheap, durable and dependable. If you feel you have too much power, be gentle with your drivetrain and find the engine's "sweetspot". You want it to work in its power range. My engines like to twist and whine. Your 4-stroke might be a workhorse with power down low. Keep the revs where they should be.

    You don't need a tach. Your engine will tell you where it wants to be working. Listen and be in tune with it.
  18. Mike St

    Mike St Member

    5-7, I like your comments, but the HS 142F is already on my first bike. So I am weighing another 4 stroke or a 2 stroke, and leaning towards another 4 stroke. So the final configuration might be a 4 stroke with a jackshaft and an 8 speed SA hub with brake.
  19. 5-7HEAVEN

    5-7HEAVEN Guest

    Thanks for compliments, Mike.

    Good luck, sir. I am unfamiliar with 8-speed hub's reliability. I like the fact that you can shift gears at a stop, with internal hubs. With the cassette, you need to be in the correct gear BEFORE coming to a complete stop.

    Mental note: shift to first gear before coming to a complete stop! If centrifugal clutch is disengaged, blip throttle to ensure gear change.:detective:
  20. pbeggs

    pbeggs Member

    im running a 2 stroke 80 cc (66,.. whatever) i have the jackshaft geared for hill climb (30 tooth input instead of 17 as sick bike parts kit) i have waaaay huge amounts of torque (ripped the dropouts out of my frame) but the 8 speed s/a with drum brake is still working (i dont shift under power and tend to take it easy on my drive train (im out in the country,. no traffic to try to zip through, no need to speed shift)

    gear train is as follows

    motor output 11
    jackshaft input 30
    jackshaft output 10
    large sproket crankset 48
    small sproket crankset 30
    hub sproket 25
    26" wheels

    tops out in 8th at about 30

    havent found a hill i cant ride up

    i have this geared about as low as possible much higher speeds would be possible with more standard gearing

    i would suggest the matching drum brake front hub,..