New vari speed tranny build

wayne z · Dec 22, 2011

OK, I've decided to try a variable speed tranny for the Predator 99cc engine.
Gonna try a cent belt clutch on the engine and a spring loaded compensating pully from Mcmaster Carr on the jackshaft output, driving a wizzer pully on the wheel.

I will have an idler wheel connected to a clutch lever on the handlebars. Squeeze the lever to tighten the belt and make the comp pully open up to about 14:1 ratio. Release the lever and the pully closes up to change to 10:1 total ratio.
The pully was just delivered. 60 bux plus shipping. It looks good, much smaller and lighter than i expected.

Cold bent the cranks last night on the Huffy, getting it ready. Just waiting for the Wizzer sheave and some snapring bearings now.

rustycase · Dec 22, 2011

Good luck Wayne!
Really appreciate you posting the engineering notes in detail, here on the forum.
What is the physical OD of the variable sheave you pictured?
Best
rc

wayne z · Dec 22, 2011

OD is 3 1/4"

cannonball2 · Dec 22, 2011

Now were talkin Wayne! I assume you are probably going to use a Maxtorque pulley clutch? If so its pulley is 3.2 to the varis 3.25 basically a 1/1 in high to the final reduction. That ought to really move! My Cranny with the Lifan runs a Gen 2 Whizzer sheeve. As I remember it is 15" in dia. I believe it is driven by a 2.5" pulley, the minimum dia. I felt would get enough belt. That yeilds a 6/1 final. Where are you getting the rest of the reduction? My primary a 3.2/6" to a secondary of 2.5/15" gets a 11.25. Dont doubt you one bit on your figures, just figure youve got something innovative in mind.

wayne z · Dec 22, 2011

Hey CB, I'm using a Comet clutch that has dual 2.5" pullies. Gonna use 1 belt to drive a 5" pully on the jackshaft. The vari-sheave goes from 1.95 to 3.15.
The ratios I stated earlier aren't exact, Rounded off somewhere around what I remembered from fooling around with gear calc.

I'm gonna use the vari pully to drive the Wizzer sheave.

If I need more reduction I can go larger on the driven jack sheave.

cannonball2 · Dec 22, 2011

Gotcha. Figured you had a plan. Never thought about the vari on the final. Thats quite a range on the vari. This should wotk out great. Pulley is really not bad at all on cost. Is there much spring tension to overcome with the hand lever?

wayne z · Dec 22, 2011

I wont know about tension and clutch lever for control until i try it. I can squeeze the pullies apart with my fingers fairly easily.
If the clutch lever don't work out, I'll go to a gated jockey shift on the left side and maybe switch to a idler clutch then.
Was tryin to keep all the controls on the handlebars. A few times I've been jockyshifting my current build when I realy needed both hands on the bars.

silverbear · Dec 22, 2011

Looks like it's going to be an interesting build...
SB

killercanuck · Dec 22, 2011

Cool. If you can open it with your fingers, a handlebar clutch handle won't be a problem. How many people can hand operate their HT clutch? lol.

wayne z · Dec 22, 2011

killercanuck said:
Cool. If you can open it with your fingers, a handlebar clutch handle won't be a problem. How many people can hand operate their HT clutch? lol.

I can barely operate the HT clutch by hand, this pully is easier than that.

Not sure about handlever control yet. Most handlevers only pull the cable about 5/8". The idler must have sufficent travel for the varipully's operating range, which is unknown to me right now. With the leverage involved to get enough movement of the idler, a handlever may or may not work.
Can't wait to get on with the build and find out!

curtisfox · Dec 22, 2011

Boy I got to watch this, I have been wanting to do something like this............Curt

Good luck and hope it works well for you

WayneC · Dec 23, 2011

WayneZ,

If the handlebar lever fails to move the idler enough there is a pulley/multiplier that works to move the cable further. It's called the Travel Agent.
Problem Solvers Travel Agent Silver with Silver Roller @ eBikeStop.com

They also make a straight line one that may work in your case.

Or you could try a rotary index shifter. They move more cable than a trigger type with the added bonus of locking in multiple positions.

WC

wayne z · Dec 23, 2011

Thanks WC, for the travel agent tip. I might try one of those, especialy if I have tight bends in the cable run. Thanks also to everyone else for showing intrest.

I can prolly get enough travel for the idler by choosing placement of the cable on the idler pivot lever. The thing I need to find out, is how stiff the handlever pull will be when leverage is enough to get adequate travel for the varipully's range.
I could also prolly build one of those overcenter spring/lever mousetrap things like old Harleys used to assist clutch pull.
Another option might be a twist shift lever from a 2 speed Puch moped. I think the clutch lever and hand lever move in unison on these, giving plenty of leverage for pulling the shift cables. I could then use an idler clutch, my preference, instead of the cent.

KCvale · Dec 23, 2011

wayne z said:
OK, I've decided to try a variable speed tranny for the Predator 99cc engine.
Cold bent the cranks last night on the Huffy...

That sounds like a nice shifting setup, I look forward to seeing how it goes, but just one question...

Is your Huffy a restored and strengthened solid old school steel one with a good solid new back wheel?
Or are you planning on dropping that big 3HP 26 pound 4-stroke and your shifting tranny on a POS Wallyworld $85 bicycle that barley holds up as just an adult pedal power bike?

I only ask because I have had 4 motorized Huffy's through my shop for repairs, all 4 just 2-stroke direct drive, 3 were 48cc motors and 1 a 66cc, every one had a trashed back wheel and two show fractures in the key frame welds, one of which was actually broke half way through from just a speed bump so the customer said.

There is much to be said for building DIY on the cheap like your Harbor Freight $100 motor and own 'kit' type parts, but to me the very last place to cut corners is on the bike itself if you want it safe and reliable.

Just something to think about before you put all that time and effort in to making it some high power racer is all.

silverbear · Dec 23, 2011

What interests me about this build is the prospect of an affordable and reliable 5 stroke engine, the variable speed transmission making it capable of cruising without winding out the engine and gearing low enough to handle hills with ease. The topping on this cake is a quiet belt drive to the rear wheel. I've also come to the conclusion from my own builds that around a hundred CCs is just right.

Wayne, aside from wheels, bike frame, brakes and peripherals like spiffy seat or lighting...

for the engine, sheave, belts, comet clutch, variable speed pulley and jack shaft makings, what kind of budget do you anticipate? I think your idea has a lot of potential.
SB

cannonball2 · Dec 23, 2011

While I agree to an extent about the cheaper bikes. The HF engines in my experience are very smooth. Its is probably more of a manifestation of vibes that weight. My experience with the HT engines (3) was given time they would vibe just about anything a part. I do agree on the wheels, especially if using an HT as the starting loads are pretty harsh. A recoil start engine with an auto clutch is pretty easy on the drive line. I am curious to see how my Pacific bikes Schwinn aluminum frame holds up with an inframe HF 99cc. My guess(and hope) is it will. Still you offer good advise, especially if using an HT.

silverbear · Dec 23, 2011

silverbear said:
What interests me about this build is the prospect of an affordable and reliable 5 stroke engine, the variable speed transmission making it capable of cruising without winding out the engine and gearing low enough to handle hills with ease. The topping on this cake is a quiet belt drive to the rear wheel. I've also come to the conclusion from my own builds that around a hundred CCs is just right.

Wayne, aside from wheels, bike frame, brakes and peripherals like spiffy seat or lighting...

for the engine, sheave, belts, comet clutch, variable speed pulley and jack shaft makings, what kind of budget do you anticipate? I think your idea has a lot of potential.
SB

Opps, got an extra stroke in there... that would be really interesting!
SB

wayne z · Dec 23, 2011

Thanks KC, for the advice. Yea, it is a cheap ol Huffy. I'm using it as a cheap testbed for this new tranny idea mostly cuz it's here. I know that all parts of it are of dubious reliability and will have to be watching for and expecting issues.
I do have a new set of chromed wheels with 12 guage spokes and city slicks that I plan on using,along with some suspension forks with brakes.
The fenders are going. As long as I drive mildy on the smooth country roads here, and watch the frame, Ill be OK.
While Im working out the bugs, I'll be lookin for the right bike.
I've got this 40's Rex, but It would just feel wrong to change anything about this one.

Russell · Dec 23, 2011

First of all I would like to say I follow your postings and enjoy them.

However on this one I have a question: when the lever is released, what keeps the sheave from opening due to the load on the final drive belt. Seems that it would tend to open until a balance vary sheeve spring load and wheel sheeve slippage balanced.
Just a thought!

curtisfox · Dec 23, 2011

Do you have the part number? If this is going to work ( and i am sure it will )I want to order one. THANKS............Curt

New vari speed tranny build

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