Gear Ratio Help

[aeriojunkie]

Okay, so I am getting ready to build up the 2-seater rolling chassis that I just bought used for $50! I am trying to build it for my son and daughter to ride on, so I don't want it going too fast because of quite a few obstacles in the yard and I don't want them going too fast either. The kart has a jack shaft setup on it already. It has a 60 tooth sprocket on the axle going to a 12 tooth on the jack shaft. The other end of the jack shaft currently has a pulley, which I am going to change to a sprocket so that I can get a new clutch locally and inexpensively.

I know that I currently have a 5:1 ratio, which is pretty good all around ratio, but I want to slow it down more. I just don't want to set up something that just creeps around at the same speed as a powerwheels toy.

Now for my question. If I set up a ratio between the clutch and the jack shaft do I add the two ratios together or do I multiply them? for instance, would a 5:1 and a 2:1 create a 7:1 final ration or a 10:1 final ratio? Thanks in advance for all your input!

 

[ironman]

Just add on a 12 or 11 tooth on the jackshaft this is what i did to mine .works fine i went with a 11. so my clutch is 12 jackshaft for that side is 11 other side is 12 and sprocket is 48 works great little slow on take off but it flies on top end but i have the govener off to.

 

[Kenny_McCormic]

Sounds like it has half a comet torque converter on it. Put up some pics. How wide is the widest inner point of the pulley? If its 5/8" you cant get a new drive pulley, if its 3/4" you can get a new drive pulley and have an automatic trans(climb walls power).

 

[aeriojunkie]

The guy that I bought the cart off of bought it and took the motor off and put it on his rototiller. I asked him if he had the clutch that he pulled off it when he put it on his tiller but he said "No, what you see is what you get". Oh well I guess.

I am pretty good when it comes to mechanical devices and all, but I am new to all the details of go-kart options. I looked at the torque converters online, but can't afford to spend that much right now for a new one. I thought that both pulleys changed diameter on a converter setup, so correct me if I am wrong. Here is a picture that I have of the jack shaft setup though. I will go ahead and post all the views I have of it.

 

[Kenny_McCormic]

Yea, thats not a CVT its set up for a belt style clutch, just change the pulley to a sprocket and put a normal clutch on it.

 

[aeriojunkie]

That is what I thought too. You had my hopes up there for a little while though! So any input on how to figure the speed if I have two different geat ratios?

 

[ineed2fly]

Can't you just get a v-belt clutch on northern tool? That seems alot easier.

 

[aeriojunkie]

I could, but then I would have to pay more for it than a chain clutch locally, and then pay for shipping too. I also thought that a belt driven clutch was less desireable because the belt will wear and stetch over time. The biggest thing that I wanted to know was how to determine the sprocket size I needed to get the speed I wanted.

 

[Kenny_McCormic]

Do the math for what the jackshaft will be turning at with various sprockets on the engine side when the engine is at 3600rpm. Use this calculated RPM for the RPM in the speed calc.

 

[aeriojunkie]

Thanks Kenny! I don't know why I didn't think of that. Oh wait a minute, yes I do too. It was too simple of a solution. I always have to over analyze everything! Thanks a bunch though. Now I just have to see if I can find the gears that I need.