Mechanical efficiency of chain drive vs roller drive

Discussion in 'Transmission / Drivetrain' started by mifletz, Dec 31, 2009.

  1. mifletz

    mifletz Member

    The road surfaces in N.Israel are so poor that my chain drive threw its chain three times too often. So I've gone back to friction drive for the moment. Although less power, friction drive is much more sturdy and reliable and tolerant of bumps. Having changed to semi-slicks has also helped considerably. I await to read a proper review of Staton's new axle kit before considering going back to a chain.

  2. mifletz

    mifletz Member

    This is my sprocket





    Is my sprocket amenable to changing to a freewheeler
    like this one you mentioned?

    Last edited: Jun 6, 2010
  3. loquin

    loquin Active Member

    The spline on the gearbox shaft is the issue. (Dimensions below.)

    It's very difficult to find a matching coupling, (at least in the U.S.) The simplest approach would be to sacrifice a drive sprocket. If the existing sprocket 'barrel' is greater than 1.375 inch in diameter, you could get it turned down, then cut 1-3/8, 24 TPI threads into it, to form a freewheel adapter.

    Or, turn it down to 3/4 or 7/8 inch diameter, then get one of Staten's adapters.

    Or, simpler yet, you could buy a 1/2 inch shaft adapter from Staten, bore it out to 14mm, and mount it to the shaft, using the setscrew to lock it into place. (You should also be able to machine (or file/grind) the key so that it will fit the now slightly shallower 1/8th inch key way in the adapter, but also fits into one of the 6 slots in the shaft...) If needed, the amount of material removed would be very small (between one and two tenths of a millimeter) from the setscrew face of the key. Plus, a small amount would need to be ground or filed from the corners of the key inserted into the spline side of the key. (ref the modified key cross section, below)

    Attached Files:

    Last edited: Jun 7, 2010
  4. loquin

    loquin Active Member

    Note that these freewheel sprockets use chain with a half inch pitch. So, you would probably need to replace the rear sprocket as well. Since the sprocket teeth are also longer, this chain size may be less susceptible to jumping the sprocket. You should also make sure that the chain is snug, using an idler sprocket.

    Edit: Staton apparently doesn't sell 1/2 inch adapters. So, you would need to use the 15mm metric version, and shim it with .5 mm shim stock, or the 5/8 adapter, and shim it with shim stock totaling about .94 mm. The 15mm version uses 4mm key stock, which you would need to obtain, and file to fit. The 5/8 inch inch version uses 3/16 inch key stock, which would need similar filing (on a larger scale,) to fit.

    While the 15mm metric version has two thumbscrews, it is longer than the 5/8 inch version, and may be too long to fit on the splined shaft of the gearbox. On the positive side, you should be able to easily find shimstock in exactly 0.5mm thickness...
    Last edited: Jun 7, 2010
  5. mifletz

    mifletz Member

    For what purpose are these expensive little freewheeling sprockets used for apart from on a few motorised bicycles?!
  6. GearNut

    GearNut Active Member

    It will ratchet freely and reduce the effort required to pedal the bike when the engine is not running. This is because all of the associated transmission components from the clutch to the transmission sprocket will not be forced to turn with the rotation of the chain.
    Also, when traveling downhill, if the speed of the bicycle exceeds the normal operating speed of the engine and transmission, the freewheel will act as a safety clutch of sorts and free spin instead of forcing the engine and transmission to spin faster then they were designed to. It also makes casual coasting easier. You do not have to let the automatic clutch slow down to it's stall speed before the clutch shoes disengage from the clutch bell.
  7. mifletz

    mifletz Member

    Have you a photo of your bike with a freewheel sprocket?

  8. donutguy

    donutguy New Member

    I have the Mitsubishi TLE 43 friction drive kit from Staton. I use the 1 1/2 inch roller and after it was broken in- I get close over 35 mph on flat ground.

    That's fast enough for me!

    I went with the friction drive kit for a few reasons....

    -It's very easy to transfer between bikes

    -It quite a bit easier changing flat tires

    -It is somewhat less conspicuous then a frame mounted motor- the less attention I draw from the authorities-the better.

    -It can easily be disengaged if I have motor issues and be pedaled home.

    -I use a large 2.4 inch tire for maximum roller contact.

    The main disadvantage-it doesn't work for **** in the wet....but unless I get caught in a rain storm-no biggie as I mainly ride it for recreation.
  9. mifletz

    mifletz Member

    Last edited: Jul 11, 2010
  10. GearNut

    GearNut Active Member

    My daughter has a pocket bike that uses that exact transmission and #25 chain size. The freewheel is on the rear wheel instead of the transmission. I have yet to see a freewheel that mounts on this type of transmission.
  11. mifletz

    mifletz Member

    Last edited: Jul 11, 2010
  12. GearNut

    GearNut Active Member

    The upper one looks like your best bet, but it is not made to fit a splined shaft like your transmission has. It would be way more work than it is worth to get it to fit.
    I read it's description on the site you linked and it fits over a smooth shaft and is held in place with a single pin.
    None of the other sprockets I saw at that site look suitable to me.
  13. mifletz

    mifletz Member

    Last edited: Jul 15, 2010
  14. GearNut

    GearNut Active Member

    I saw none with a splined inner diameter. You may need to have a freewheel adapter custom made.
    The only other option I can think of right now is to hand fit a typical keyed freewheel adapter so you can use the key in one of the splines on the transmission output shaft.
    Not exactly desirable but still do able.
    Here is one type of keyed freewheel sprocket that does not require an adapter:
  15. Bonefish

    Bonefish Member

    I like the looks of your set up better than Staton's axle mount. Your engine sits higher and looks like it would be better protected than the axle mount he has. His 5:1 gearbox maybe superior than the Pocket Bike tranny that you are using, but If you are considering ponying up and getting the axle mount. I would first look into if you could run a set of freewheeling cranks. This would make your drive ratio variable, rather than fixed.

    You/or your buddy's seem pretty ingenuitive in making that mount, you might be able to mount that engine on the top tube of your frame and run a chain down to a set of freewheeling cranks and utilize that cassette you have on the back.

    It would cost less than a Staton Axle Mount, and you would have greater range/use out of your bike. It would allow you to throw it into low gear to climb hills, then you could throw it in high gear to cruise the flats.

    I have a similar setup. It took alot of work, but, I love mine.

    Check out: Scooterguy Tanaka Mount in Frame mount setups, to get an idea of what I'm speaking about if you don't understand what I'm saying. He is using the same 5:1 gearbox you are using.

    Loosing the extra chain on the back wheel, will make your drive train more efficient, and utilizing your back cassette will make it more effective.

    Less is more,
  16. loquin

    loquin Active Member

    Again, you need to be able to get an adapter which fits. The adapter mounts on the splined shaft (14mm x 11mm x 6) on the gearbox, and the freewheel threads on to the adapter. As I mentioned earlier, you could use an adapter designed to fit a larger shaft, IF you use the appropriate shims.

    I found 1 company in the U.S. which sells spline couplings which fit the splined shaft on the gearbox, but, they wanted over $30 per 2 inch coupling on single-unit sales.

    I believe your best bet may be to take the existing sprocket, get it turned down to 3/4 or 7/8 inch, and have a key-way cut into it - essentially, turning it into a very short shaft for mounting the adapter.

    The threads on the standard freewheels are 1-3/8 inch, 24 TPI (threads per inch.) (Offhand, I don't know the thread specs on the metric version.)

    The size of the existing sprocket on the gearbox and the size of the freewheel sprocket appear to be similar; you just need to make sure that the total reduction ratios are correct (the new sprocket will be on a 1/2 inch pitch. The old sprocket/chain are often metric, #25 (0.25 inch pitch,) or #35 (0.38 inch pitch) chain on pocket bikes & scooters.

    As far as Staton's freewheels; the White Industries freewheels are the best you can buy. They're expensive, but, they really are top of the line, manufactured to tight tolerances, and have a very strong racheting mechanism. The others are a lot less money, (but, are also not as reliable,) so, when setting up the system, you might want to use them initially, until you're sure that the sprocket ratios are correct. THEN, order a White Industries unit.

    One final note. When using a freewheel on the DRIVE end of the chain drive that spins a sprocket on the left side of the wheel (when facing forward,) you use standard freewheels. But, when the freewheel is on the DRIVEN end (with a chain on the left side when facing the front of the bike) use a left-hand threaded freewheel.

    However, if the chain is on the right side of the bike, reverse this, and use left-hand freewheels on the drive sprocket, and standard, right-hand threads on the rear.

    If you don't follow this approach, your motor will be trying to unscrew the freewheel from the adapter (or hub.)
    Last edited: Jul 15, 2010
  17. sparky

    sparky Active Member

    It sucks that Staton changes his site so often that links never point to the intended target for longer than a few months.

    Anybody got a link to this freewheel adapter??

    Or... better yet... does anybody know if either that freewheel adapter or the couple that GearNut posted will actually fit the 5:1 gearbox???

    I'm determined to find a way to attach the lightweight 5:1 gearbox to the fixed-gear Nuvinci... but I don't want to do it without a freewheel somewhere in there.
  18. loquin

    loquin Active Member

    Last edited: Oct 17, 2011
  19. rawly old

    rawly old Member

    Ahh, ta heck widdit, no more gas, no electric, no friction, no chain; I'm
    goin' totally retro.:jester:

    Attached Files:

    Last edited: Jan 6, 2012
  20. rawly old

    rawly old Member

    Oh, and dissun too

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