Double Variation Questions

I'm all about the e50s and am a super noob to variators. I totally get how the variation part works, but I've never gotten very intimate with any variated bikes so I have a couple questions.

1) How does starting work? Do all CVTs have a centrifugal clutch, and a lever on your handlebars somehow engages it to turn things over, just like on an e50?

2) What is the gear ratio range on some double variated setups? Honda, Vespa, Derbi... Just from looking at pictures it seems to go from about 2:1 to 1:2. Maybe 2.5:1 to 1:2.5?? Like if the variator were stuck in "low gear" (low speed) what would the final drive ratio be around?

3) If (extra hypothetical) I were to try to copy a Derbi transmission, where would I get the boxed things in the picture, including the clutch bell? It looks like the variators sold on treats are like only half of one of those.

(edited)

Derbi variator.jpg

Re: Double Variation Questions

there are centrifugal starter shoes in the clutch bell and then the clutch is under the bell taper fit on the crank. you just either pedal or push to start. there is a decomp lever for... decomping. you won't have an easy time finding the CVT pieces sorry to say... better to copy a hobbit setup as far as parts availability goes...

Re: Double Variation Questions

If you are making custom shit then use a honda, moby, or pug front vario to get clutch function (I think honda has the clutch in the front ?). Use a honda or scooter rear vario for the back.

Re: Double Variation Questions

As stated the majority just use a centrifugal starter clutch that engages once the drivetrain has reached a certain speed, locks itself to the engine, and turns it over to start. No levers involved unless you use the decomp. The starter clutch is a separate assembly from the main drive clutch.

As far as seeing half the parts online that would be because one face of the front variator is actually part of the clutch bell and maintains a fixed position. The moving face is the outer half and is the part that has moving pieces (weights) inside concerning gear ratio change. The outer half is the more important piece for modifications unless you are concerned with clutch engagement as the inner bell is just an immovable object with an angled face that the outer half compresses against to drive the belt higher in the groove.

The rear pulley also has moving parts but not weights. The rear end has the spring that acts against the weights in the front and returns the bike back to low gearing as the rpms decrease. Generally this part is not tuned, nor does it generally wear out as quickly as the parts of the front pulley so you are less likely to see it for sale new.

Re: Double Variation Questions

Tracy Meade /

gearing on a single variator returns in the vicinity of 4x the starting gearing. In the vicinity of 16x for dual variation.

Re: Double Variation Questions

anybody know the variator ratio for a derbi? Hobbit isnt that much, it only changes between .34 and 1.02x stock depending on the model. Puch za50 gearing is 4.38 and 2.91 for a change of 1.47. Unless if I am way off.

Re: Double Variation Questions

This is a dead thread. Make your own. And the service manual for a hobbit states tha tit is not nearly that limited, you forget though that the bikes have a final drive reduction after the pulleys no matter what. Generally pulley ratios are symmetrical, meaning that if you have a 2:1 ratio to start, you will gain a ~1:2 ratio to end if you have pulleys with the same ramp angle.

Re: Double Variation Questions

Snowmobiles seem to be just about the only CVT with no centrifugal engagement clutch. They use belt slack to to stop driving, not a centrifugal clutch. Snowmobile Clutches (variators) start around 3:1 and end up with a ratio near 1:1.

The CVT system I am working with for my KLM70 goes from 2.341:1 to 0.852:1. The gearbox in the rear is about 7:1.

It is based on snowmobile clutches but Olav Aaen’s Clutch Tuning hand book is the best information you can find on the CVT.

Re: Double Variation Questions

Dirty30 Dillon /

peter heid Wrote:

-------------------------------------------------------

> Snowmobiles seem to be just about the only CVT

> with no centrifugal engagement clutch. They use

> belt slack to to stop driving, not a centrifugal

> clutch.

Doppler variator for moby also does this. If your tune your variator well and have an alternate means of starting the bike, you really don't need one.

Re: Double Variation Questions

I had a clutchless variated gokart as a kid.

It was pull start and no clutch.

The front variator would open so wide it the belt would slip at idle, and when you hit the gas the variator would squeeze together and grab the belt.

Re: Double Variation Questions

If I am not mistaken, gas powered golf carts are similar.

Re: Double Variation Questions

I have a dual variated moped using two scooter variators. One variator increases its circumference by four times. The vars are the same size so working together the circumference increases 8X. That's 1:8 and more range than a 70cc engine can really make good use of.

Re: Double Variation Questions

I forgot how to divide fractions or something, stock hobbit transmission changes about 2x, which is about the same as french bikes, and more range than za50. derbi is probably close to hobbit.

Re: Double Variation Questions

#CrazyWayne™ rocks. #CrazyWayne /

peter heid Wrote:

-------------------------------------------------------

> Snowmobiles seem to be just about the only CVT

> with no centrifugal engagement clutch. They use

> belt slack to to stop driving, not a centrifugal

> clutch. Snowmobile Clutches (variators) start

> around 3:1 and end up with a ratio near 1:1.

>

> The CVT system I am working with for my KLM70 goes

> from 2.341:1 to 0.852:1. The gearbox in the rear

> is about 7:1.

>

> It is based on snowmobile clutches but Olav

> Aaen’s Clutch Tuning hand book is the best

> information you can find on the CVT.

I have that hand book it rocks.

The toque spring is like like having a ato-lonch lever.

Re: Double Variation Questions

Mikey Antonakakis /

If both pulleys have a ratio spread of 4 as you say, then together they have a spread of 16, which I think isn't likely. I could be wrong about the scooter you are referencing, but most belted CVTs have a total spread of 3 or 4, no where near 16.

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