CHEAP Belt drive tranny Camshifter

[XLerate]

Hey, guys!

Another cheap and simple thought on power transmission for some of your projects could include a selectable vee belt drive. An arrangement of progressively larger-sized pullies arranged on a single free-turning shaft, with that shaft having one more pulley driving via a vee belt to another rear or driven wheel pulley could be used.

Engine drive output is connected to a shaft with multiple pulley sheaves of various diameter along its length. Another shaft has pullies all of the same diameter so that there's different ratios depending on which pulley is selected. Normal condition is that all vee belts between both shaft's pullies are slack until one is selected for drive.

Another selector shaft somewhat similar to a camshaft is used to shift gears: where this selector's 'Cam-shift' shaft's lobes are instead arms with idler pulley/rollers at their ends, these being just above the vee belts of the other 2 shafts. The roller pulley arms on Camshifter shaft are arranged somewhat like spokes or like the points of a star protruding outward from shaft, with position of each arranged for a particular vee belt. For a 4 speed Camshifter the various ratio's tensioner rollers are arranged on arms at every 90* around shaft, down length of shaft, with each arm/roller directly above a particular ratio of belts already mentioned.

As the straightline 'Shifter' lever or pedal [with position detents or locking notches] is actuated this 'Cam-shift' shaft rotates CW or CCW as desired, thereby moving its arms with roller/pullies to apply pressure to a chosen ratio vee belt while leaving the others slack. This motion selects the next ratio pulley in ascending or descending progression, either to upshift or down shift, by causing roller pulley to apply pressure to chosen vee belt. This would allow choosing a gear by having Camshift's chosen idler pulley depress a vee belt for a particular drive pulley, thereby taking slack out of belt and applying pressure as needed to engage chosen vee belt drive to driven pulley.

It may be necessary to rotate this Camshifter shaft with a latching 'geartooth' mechanism that's also easy to envision and build. Depressions in a star wheel attached to Camshifter shaft's end are used, where a lever with a pin will drop the pin down into a notch in star wheel to pull or push wheel forward or backward 90* at a time for 4 speeds.

No clutch mechanism is needed as there can be either/or an 'in between' disengaged position for shifter or a secondary idler shaft with a similar arrangement of slack/tightened vee belt such that normal mode is with pressure applied to drive this shaft and 'clutch' action disengages this vee belt's tension to cause free wheeling or non-powered mode to shaft and pulley. The 'clutch' action could be controlled by a lever, foot pedal or the same shifter with a bit of ingenuity. Something similar to the 'reverse lockout' found on some floor shifters comes to mind but some lever mechanical advantage may be required to engage.

It's possible to 'blip' the throttle between shifts as Camshifter shaft is rotated to match engine speed to next ratio.

A similar slack vee belt and idler roller-tensioner mechanism is commonly used on roto-tillers for gardening, where it engages or disengages power to tiller tines, though only one speed is found there. Single vee belt drives are currently used on some fairly large horsepower bikes in the 100+ HP range with accompanying torque. This system is an easy 'Build at home' project that could be applied to anything with an engine and wheels that needs a selectable multi-speed power transmission. Overall a very small investment in materials considering the going price of transmissions and yet it gives all the features needed in a multi-speed transmission with outstanding reliability and very cheap upkeep or maintenance for many years of use.

This is a free gift in the spirit of Christmas, when the greatest Gift of all time was given!

Brought to you by JimmieD - XLerate

ps: I ask that you include my name if you copy this simply because it was my idea, thanks!

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[XLerate]

2]

In case some of that was not clear to understand, here some more explanation:

There's a Primary jackshaft with multiple driving pulleys of various diameters. There's a Secondary driven jackshaft with multiple driven pulleys all of the same diameter. These are free standing jackshafts supported by bearings. There's a third shaft, the Camshifter, which has the protruding arms with idler rollers for selecting desired ratio.

Primary jackshaft is driven from engine. The drive from engine to Primary shaft could be 2:1 ratio so that smaller speed selector pulleys may be used on the Primary shaft. The Secondary shaft has an end pulley that drives to rear wheel. Vee belts transfer power from engine to Primary shaft and from Primary shaft to Secondary shaft, and from Secondary shaft to rear wheel.

The Camshifter shaft takes the slack or slippage out of a selected vee belt to provide drive power to rear wheel. So, a Primary driving shaft, a Secondary driven shaft, a Camshifter speed selector shaft with idler rollers, with all these supported by and running in roller bearings.

Camshifter shaft has the notched star wheel on one end. There's a Shift Lever or pedal that's connected to a Shift Rod at 90* angle. Shift Rod has a yoke at the end with a cross-pin in yoke. Yoke sort of straddles star wheel perimeter. Moving Shift Lever pulls or pushes Shift Rod so that yoke pin can drop down into notches in outer rim of Camshifter star wheel to turn it 90* per motion.

The Shift Rod requires a lifter mechanism to disengage yoke & pin from starwheel notch for next higher or lower speed selection. Lifter may be accomplished in part with a ramp, where initial motion of Shift lever mechanism on ramp lifts pin and further motion drops off end of ramp to allow pin to drop into next notch. Lifter ramp disengages yoke and pin out of notch where further motion of shifter & lifter then drops pin back down into next chosen notch. This movement of shift lever in one direction or the other upshifts or downshifts by turning star wheel which turns Camshifter 90* at a time.

It's possible to make this system work with up to 6 speeds so that reference to 90* in both both these pages isn't directly relevant. It was given more for sake of explanation.

Hope that helps explain the system. It's easier to see or imagine if you scratch out some drawings as you read.
JimmieD - XLerate

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[XLerate]

Another option for Shift Rod yoke and pin is to have mechanism spring-loaded so that yoke pin is lifted out of any notch at normal running position. Upon movement of Shift Lever the Shift Rod is then forced down out of lifted position by a ramp in linkage to engage notch in star wheel. The downard force can be done with a simple ramp designed into Shift Rod mechanism. A little head scratching there with a drawing helps one to imagine or envision it.

No, I do not have pictures and no, I do not have drawings, sorry! It works though
JimmieD - XLerate

[Rhynri]

I think I see what you are talking about in my head, but wouldn't this burn the loose belts when the alternative gear selections are made? Also, are you actuating the camshifter directly as the rider, or how is that working. Even the rototiller version of this requires significant pressure to work (relatively speaking).

[XLerate]

I think I see what you are talking about in my head, but wouldn't this burn the loose belts when the alternative gear selections are made? Also, are you actuating the camshifter directly as the rider, or how is that working. Even the rototiller version of this requires significant pressure to work (relatively speaking).

There's literally millions of pieces of equipment in service out there everyday around the world that use a slack-belt drive system. As one belt is selected for drive the other belts are slightly looser and by this they move freely on pulleys. This motion prevents one single spot on a belt from heating up to cause damage.

In addition it's possible to incorporate a 2 stage setup, that the Camshifter selects a particular 'speed' and another connected system applies the pressure to the slack belts through applied leverage, a basic mechanical principle.

This could be done as part of a separate leveraged slack belt clutch system, to engage or disengage and for free wheeling or stopping. May try to write that out but anyone that can understand this part so far would have no trouble building the other part.

"Also, are you actuating the camshifter directly as the rider, or how is that working."

Of course the rider selects the gear, who else could do it? I explained the whole operation twice hoping to make it understandable. I can answer any question about a particular part or aspect but don't want to go back and explain it all over again from start to finish. Okay, I'm grouchy this morning because I'm hurting all over, sorry. I'll try a short explanation. If that isn't clear please ask about specific areas and not the whole system.

Move Shift Lever forward or backward - Shift Lever moves Shift Rod - Shift Rod yoke pin engages Star Wheel - Star Wheel turns Camshifter shaft - Camshifter shaft motion selects a single pulley ratio as 'driver' as Camshifter shaft rotates and Camshifter roller tensions belt - selected Primary Shaft pulley becomes Primary drive pulley to change drive ratio - Primary drive pulley connects to Secondary driven shaft pulley by tensioning vee belt - Secondary shaft's end pulley drives rear wheel - Lifter mechanism may be needed on Shift Rod yoke to engage/disengage yoke pin to Star Wheel - Spring pressure lifts shifting yoke in default mode - further movement fore/aft causes Shift Rod mechanism to impinge a ramp - ramp pressure forces yoke pin back down into next chosen Star Wheel notch - forward or backward around circumference of Star Wheel - Yoke pin turns Star Wheel - Star Wheel selects gear ratio - separate slack belt mechanism may be used as clutch.

I didn't describe all possible details because so many here are of a very inventive mind and will think mechanically. Mainly I wanted to get the concept published so that others could apply their own inventive thoughts to it, this here being just enough to get folks started with their own mental gears spinning so to speak.

I most often think about cycles in terms of trikes or sidecar rigs, where a person can use more foot controls like say a clutch pedal etc. so some stuff is more difficult with a 2 wheeled rig.

I once owned a 2 speed system that had separate driving shafts end to end that were externally splined on the ends. An internally splined driven coupling was in between shaft ends, moved by a fork engaging a ridge on the coupling. Shifting splined driven coupling to left engaged low speed shaft and to right engaged high speed shaft. There were splines on the driven coupling exterior and its driver pulley's interior so that its pulley could stay centered to prevent belt misalignment. It was incredibly simple and foolproof, no problems and almost zero maintenance required beyond new belts and a dab of grease here and there.
JimmieD - XLerate

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[XLerate]

I apologize for the tone of my last reply! I don't do pain well and this morning is a real standout, one to write down on the calendar! My own stupid fault because I'm all busted up and other health issues but I decided to spend 3 hours digging, raking etc. on my dirt driveway yesterday. Pure genius on that one...

Anyways, sorry to be a grouch this morning!

[Rhynri]

I understand completely. I still am having a little trouble visualizing the system (they keep changing the dosage of my epilepsy meds, and it's messing me up.) But my question was specifically if the rider had some sort of force multipication from their foot to the system to keep the shift effort low, from your post I see they do:

Move Shift Lever forward or backward - Shift Lever moves Shift Rod - Shift Rod yoke pin engages Star Wheel - Star Wheel turns Camshifter shaft - Camshifter shaft motion selects a single pulley ratio as 'driver' as Camshifter shaft rotates and Camshifter roller tensions belt

That was what I was looking for, so thank you, the rototiller version I am used to actuates the roller tensioner directly, and takes a lot more effort than I'd be comfortable doing with my foot, hence my question. Sorry I was not more clear with the phrasing!

As for the pain and grouchyness, I have fibromyalgia and a lot of spinal damage (thank you Army!) so I understand completely.

[XLerate]

Ah, yes, your basic slammed spine along with fibromyalgia, I know it well. You truly have my sincerest sympathy! Often the strongest pain meds available won't even touch it. Sorry, hoping the best for you! Thank you for serving!

Yes, some of those old rototillers took 3 men and a boy to engage the chopper lever!!! I had one like that and found that they had completely cancelled the lever advantage in their hokey design. Once it was engaged it was just as hard to release. Built like a tank though...

I don't have any pictures now but wanted to throw the design parameters out there so that guys could get a start and puzzle out the rest, which is the pretty easy stuff of dial-in and refinement. I may build another in the not too distant future and if so will post a bunch of pics.