How to figure out gear ratio

[jmaack]

I know there are calculators online and makes sense with clutches. My question is how tonfigure out ratio when using a torque convertor? Anyone got a link? Thanks.

 

[karl]

I have not heard of a calculator for such. But the torque converter has a range it operates in.
Starting ratio is about 3 to 1 reduction. Top end is 1 to 10 overdrive.

The starting ratio is not very critical, it will take off 3x better that a standard centrifugal clutch ,
that's all you really need to know.

Top speed is how I determine if the gear ratio is adequate for my needs.

So just using the sites handy calculator,

https://www.diygokarts.com/speed-calculator.html

Punch in the drive sprocket and rear, ect, like normal. But adjust the motor's rpm by 10%

So 3600rpm with a centrifugal clutch = 3240 with TC
6500 rpm CC= 5850 rpm TC = same top speed.

Now once you start hopping up the engine and pushing the rpms past 6k, overdrive becomes an issue.
The belt cannot handle this , it will start slipping, wearing fast, and preventing the motor from spinning up all the way.

You can either shim the clutch driver so it cannot enter overdrive, with a slightly larger diameter bushing than
the factory bronze spacer, to limit sheave travel. Or you can buy the torquezilla? or juggernaut driver that eliminates
the overdrive allowing the same unhampered high rpms, with a more refined weight pack/ spring design and better balance.
So when calculating for either modded torque converter, top ratio is 1 to 1, so treat it as a normal clutch.

 

[Kartorbust]

Are you using a smart phone or tablet? This one works quite well, itsid (Alex) created this one. Only works on smart phones and tablets, does not work on PC or laptops yet. http://app.kartcalc.net/#home

Just give it the usual info for it, tire size, estimated weight of kart plus driver, estimated HP of engine, 20 series, 30 series, 40 series or 40/44 series TC or centrifugal clutch, tooth count, axle sprocket tooth and whether or not you are running a jackshaft. You put all that info in and it'll give you estimated speed and whether or not gearing is good to have prolong belt and/or clutch life.

 

[jmaack]

I have not heard of a calculator for such. But the torque converter has a range it operates in.
Starting ratio is about 3 to 1 reduction. Top end is 1 to 10 overdrive.

The starting ratio is not very critical, it will take off 3x better that a standard centrifugal clutch ,
that's all you really need to know.

Top speed is how I determine if the gear ratio is adequate for my needs.

So just using the sites handy calculator,

https://www.diygokarts.com/speed-calculator.html

Punch in the drive sprocket and rear, ect, like normal. But adjust the motor's rpm by 10%

So 3600rpm with a centrifugal clutch = 3240 with TC
6500 rpm CC= 5850 rpm TC = same top speed.

Now once you start hopping up the engine and pushing the rpms past 6k, overdrive becomes an issue.
The belt cannot handle this , it will start slipping, wearing fast, and preventing the motor from spinning up all the way.

You can either shim the clutch driver so it cannot enter overdrive, with a slightly larger diameter bushing than
the factory bronze spacer, to limit sheave travel. Or you can buy the torquezilla? or juggernaut driver that eliminates
the overdrive allowing the same unhampered high rpms, with a more refined weight pack/ spring design and better balance.
So when calculating for either modded torque converter, top ratio is 1 to 1, so treat it as a normal clutch.

Overdrive is what is causing my issues. I am going to spin a collar on a lathe to lock the driver in a lower gear to help some. Might look in to the juggernaut. I'm honestly getting tired of these converters and what it takes to make them work at high rpms.

 

[Denny]

CVTs ain’t perfect, but it’s the best we got. Same for sleds and side by sides. You should design an automatic or manual transmission that will work without breaking and is around a hundred bucks. I’ve thought about using a fluid coupler but they are a couple of grand and are only rated to 3500 rpm. Not user tunable is another big downer. High heat is another big problem.

 

[Kartorbust]

Would be easy if there was a known list of divorced transmissions from motorcycles that we could use.

 

[Denny]

Would be easy if there was a known list of divorced transmissions from motorcycles that we could use.

But cost would be a big problem and you would still need a manual clutch.