Working on a Dual Range add-on
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  1. #1
    Junior Member t556's Avatar
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    Hey Guys, I'm new here and haven't purchased my TW200 yet. I'm still trying to decide between an older one that needs some TLC an a newer model. However while thinking about what type of riding I want to do and if it would require a sprocket change I started working on a project for the TW200. I can't tell you the details because I hope the idea will be patentable.



    I can tell you the goals of the project. I would like to hear if you would be interested in such a product.



    The modification would allow for 2 ranges of operation. The standard speed would be the stock speed, and the other would have about a 1.5:1 gear reduction. Meaning (with the reduction you would be traveling about 40 MPH instead of 60 MPH). One option would be to combine this modification with the a smaller rear sprocket, then you would have the advantage of higher road speeds, and still a low range that provides lower speeds than stock.



    The modification would allow you to change easily, meaning drive to the trail in high range and in a few minutes switch it to low range for trail riding.





    Look forward to hearing your thoughts.



    Thanks!

    Clay

  2. #2
    Senior Member lizrdbrth's Avatar
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    If it were streetable for the life of the bike I'd probably be in. Otherwise we have already scienced out less convenient (but utterly reliable) dual sprocket setups.



    Speaking for myself that would limit it mostly to a direct-driven gearbox. Not into jackshafts, multiple chains or swingarm-mounted gearboxes.



    A lot of us are fairly familiar with most of the prior art. Might not be a bad plan to get some input.



    Regardless of design, we'd all dig seeing it.



    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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  3. #3
    Senior Member tw200sgp's Avatar
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    I hope you're aware that this concept has been around for a long time - the most common version was (is) on the Honda 90 Trail (CT90). If your version could be switched on the move (via cable or a level or something) you'd have one up on the CT90 though (which had to be stopped and parked to be switched by hand).

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  5. #4
    Senior Member mhomadness's Avatar
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    I really enjoyed having that option on my Honda, If it were a flip of a lever with the near bullet proof strength of the Honda trail eng/trans combo, I’d give it a try.



    The thing about many of this kind of idea, & hopefully, eventually, working prototype, is that it should be something you want to do to prove to yourself & have the satisfaction of knowing you can do it! That’s the only way you will ever feel good/justified by the amount of time & effort it would take to accomplish such a mod. If you can market it after that, that’s cake! If it’s novel, & performs well, there will be a market for it, among TW enthusiasts, you get the idea.



    So go out & make it, ‘cause I’ll probably want one. m.
    1997 TW with some modsHidden Content Pike'n the Boont region since 1989!

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  6. #5
    Senior Member Gerry's Avatar
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    Good for you Clay. Being kind of an inventor type myself I know how exciting/frustrating it can be trying to bring a new product to market. I know only to well how wonderful it feels when folks seem to be in support of your project. My opinion has always been that patents are only as good as your willingness to pay an expensive lawyer. I believe as well that you can secure your initial development date and intention by getting some detailed drawings, perhaps photos of prototypes and send them to yourself registered mail. Then store them unopened while the patent is in process. Others may have more current information or corrections to what I had understood.



    Given that you are inclined to be fairly 'secretive' it is pretty hard for anyone to give much feedback. The setup that a few of us have now is simple does not require spending much money (TW owners tend to be very cost conscious) and as well only takes a 'couple' of minutes to switch ranges.





    I liked the 'flip of the lever' on my Honda Trail 90's but when in the low range, I found the gear noise unpleasant at anything over a walking speed.





    I too am working on some new super duper idea (I hope) but will wait until a have a real good prototype before I bring it forward for discussion. My project has nothing to do with drive systems. Best of luck to you. Here is a picture of what I believe one of the previous posters was referencing. Suspect this fellows patent has looong since expired. Gerry



    Take care my Friend.........

  7. #6
    Banned qwerty's Avatar
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    Such a device would certainly be handy, but just about any affordable type of gearbox/transmission/jackshaft will draw too much power from an already underpowered bike. Low-loss reduction systems tend to be too expensive. If you could figure a way to prevent power loss at a reasonable price, well, you'd deserve a patent.



    The solution planned for the upcoming 6=speed stroker build is dual sprockets front and rear that take the same chain length. A dual sprocket system was wishful thinking when planning began, because no 428 chain was deemed adequate for the planned power output. The new premium o-ring 428 chains have a tensile strength of 7000 pounds--certainly equal to many larger chains of conventional materials, and certainly adequate for twice the TW's original torque output.



    For ease of figuring, set the final drive ratio so that the new 6th sees the same rpm at a given speed as the original 5th with OEM 14/50 sprockets. The new 1st will provide a 9.1% reduction compared to the original. Now, suppose we swapped to a 15/53 sprocket set, just a tad taller than stock. With almost no change to the stock 22.3-inch centers distance of the stock sprockets and chain we can fit a 13/55 sprocket set, and use the same chain with the same adjustment position for an additional 19.7% drive reduction, for a total 28.8% reduction in total drive ratio. By using about 25mm of the chain adjustment travel, we can fit a 13/63, which yields a 31.2% reduction from 15/53, that for a total of 40.3% total drive reduction ratio.



    That's the best I can figure without having to break chain and with minimum gains in powertrain drag. Still 20% shy of your proposed reduction ratio, very expensive parts (primary drive, clutch, side cover, complete XT trans and shifter less countershaft, second sprocket set), significant gain in unsprung mass of the rear wheel assembly, and superior (expensive) mechanical and machine skills to pull off (split the engine cases, remachine the TW output shaft).



    There is definately room for improvement. I'm of the mind that the wide TW trans ratios will actually be more convenient when in your proposed low range than the closer ratios of the 6-speed gearset in the upper gears. The rpm drop with the stock TW trans between the top 4 gears is 35.7%, 26.7%, and 26.7%, compared to the XT (or TT-R) rpm drops of 27.0%, 21.5%, and 16.8%. It is the progressive ratios of the 6-speed that make the gearset a much better choice for highway use, and the wide ratios of the 5-speed that give it the edge in the dirt.



    Any 2-speed can be actuated by a cable or selenoid and shifted while riding. A synchronized mechanism would allow a selenoid-activated shift simply by letting off the throttle and flipping a switch in that unloaded moment between drive and driven. Probably not a good idea to do so with a 50% reduction--the effect would be even more drastic than cruising along at speed, chopping the throttle, downshifting to third, and dumping the clutch with the engine at idle.



    With practice, a non-synchronized gearset can be downshifted while moving with double-clutching and/or rev/speed matching. I've gone from 2nd to first in several vehicles ranging from VW-based single-seat buggies to semis that had non-synchronized 1st gears, some with compound lows, without even touching the clutch just by matching engine rpm to road speed. I've even been known to go from 4-hi to 4-lo without stopping and without touching the clutch. Such skills are really handy in mud or hillclimbs when good speed is necessary to begin, grunt is necessary to end, and momentum is necessary throughout. A rider will do well to master rev/speed matching.



    I'd say avoid the complexity of synchronizers and use the saved mass for robustness.



    Good luck!




  8. #7
    Senior Member Stromper's Avatar
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    Fond memories of my Kawi 100 with dual range in the gear box

  9. #8
    Senior Member Phantom99's Avatar
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    Back in the 60s I bought a Honda 90 trail for my wife. It had the dual range tranny. It worked OK, but to change ratios you needed to get off and switch the little lever on the bottom of the engine.



    In the 70s Husqvarna brought out a 360 Enduro which had the dual ratios with a bar-mounted control, something like the enrichener controls on many Japanese bikes. A buddy of mine had one and I rode it quite a bit. It worked well. They did not sell many, so it was discontinued after a couple of years.



    When I talked to my buddy a few months ago he still had it.

  10. #9
    Junior Member t556's Avatar
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    Could someone please tell me the diameter of the stock rear sprocket on a TW? Thanks!

  11. #10
    Senior Member lizrdbrth's Avatar
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    Stock 50T is 8.25" (approx., plus or minus a few freckles.) Let me know if you need the freckles.



    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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