A new project is starting! (And a little question)

[BerlanBBM]

Hey boys and maybe some girls!
I am Moritz from Germany and in the following weeks I´m gonna to show you the go-kart project of me and my buddy. We almost got the engine and the next weekend we´ll probably get the chassis for the vehicle. Our kart is going to be a half street/ half cross kart, because we´re living around of many forests so we can drive a little bit cross Our engine is a Berlan BBM 196-6,5 with 196ccm and 6,5 hp. It gots enough power to drive through forests.
But before I end this post I got a question:
#
How many teeth on axle and how many teeth on clutch?
Hope you help us (P.S.: We wanna drive ca. 43 mph.)
Next post when chassis is here!
Greets from Germany, Moritz

 

[qtband]

What size are the tires?

 

[OzFab]

It depends on what clutch you can buy. The "average" ratio is around 6:1 but that depends on other things, starting with tire size.

Welcome to the forum.

 

[Doc Sprocket]

Welcome, Moritz!

I do not think you are going to acheive 43 MPH, unless your engine has a lot of performance modifications.

We need to know how big your rear tires are, if it is a 1 or 2 person kart, approximate weight. Pictures will help, too.

 

[landuse]

Welcome to the forum

 

[BerlanBBM]

The tires are 26 cm tall. We wanna take out the governor of the engine and short a little screw which blocks the throttle.
@ Fabroman Means this for example 60:10 teeth? Whats if I take 18:36?
Sorry we only got the engine until yet so it wouldn´t be useful to post any pictures
Greets!

 

[BerlanBBM]

Ouuh nearly I forgot My weight is 65 kg and its going to be a 1 seat cart

 

[BerlanBBM]

@ Fabroman The clutch is this a round thing you put on the crankshaft? Because we dont need so what. Our crankshaft gots a rabbet were we can put on the gear. If you are oother oppinion, tell me

 

[landuse]

The tires are 26 cm tall. We wanna take out the governor of the engine and short a little screw which blocks the throttle.
@ Fabroman Means this for example 60:10 teeth? Whats if I take 18:36?
Sorry we only got the engine until yet so it wouldn´t be useful to post any pictures
Greets!

18:36 means a 2:1 ratio. You will NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER even get moving with that ratio, and your clutch will be fried in minus 10 seconds flat. Even though you do have small tyres at 10" (26cm), a 2:1 gear ratio is just plain impossible. You are going to have to gear for AT LEAST 6:1 (maybe slightly higher at 5:1, but I would not recommend it).

Please read THIS sticky regarding governor removal

You are going to need some sort of clutch. If you don't, your kart will never be able to stand still with the engine running. You can imagine it being like your car having no neutral. If you turn the car key while in first, the car wants to go forward. It is the same with a kart without a clutch. If you start the engine it will immediately want to go forward.

 

[OzFab]

 

[BerlanBBM]

Well, for me it´s no matter to get a clutch only because the cart is running then forward. The other side is-how fast does it drives forward without a clutch. And now comes the point where I am maximum confused: A owner of a kart track in near of me gots a 6,5 hp engine too. I called him on phone to ask some regular questions e.g. the transmission. His karts got a transmission of 18:36 and they drive ca. 60 kp/h. How can this be? And the karts there got a really good acceleration. Why then 5:1 or 6:1?
Greets!

 

[soggycrashed]

Well, for me it´s no matter to get a clutch only because the cart is running then forward. The other side is-how fast does it drives forward without a clutch. And now comes the point where I am maximum confused: A owner of a kart track in near of me gots a 6,5 hp engine too. I called him on phone to ask some regular questions e.g. the transmission. His karts got a transmission of 18:36 and they drive ca. 60 kp/h. How can this be? And the karts there got a really good acceleration. Why then 5:1 or 6:1?
Greets!

You need a clutch.
What is the max RPM on the motor?

I don't think a 1:2 ratio (18:36) is possible, but maybe with an electric motor.

 

[jman231994]

I called him on phone to ask some regular questions e.g. the transmission. His karts got a transmission of 18:36 and they drive ca. 60 kp/h. How can this be? And the karts there got a really good acceleration. Why then 5:1 or 6:1?
Greets!

That is a very good question haha. Its possible that he uses gearboxes on them to give multiple gears, in which case it may be possible to use that gear ratio. Maybe he just doesnt even know how his own karts work

 

[anderkart]

Well, for me it´s no matter to get a clutch only because the cart is running then forward. The other side is-how fast does it drives forward without a clutch.

_______

And now comes the point where I am maximum confused: A owner of a kart track in near of me gots a 6,5 hp engine too. I called him on phone to ask some regular questions e.g. the transmission. His karts got a transmission of 18:36 and they drive ca. 60 kp/h. How can this be? And the karts there got a really good acceleration. Why then 5:1 or 6:1?
Greets!

A go kart would have the same top speed using a centrifugal clutch, or a solid drive-gear, (with the same number of teeth) Because after the engine/clutch reaches a higher RPM, the clutch locks-in and acts exactly like a solid drive-gear.

The big advantage of using a clutch is: you dont have to push-start the kart, and you can stop without shutting the engine off. The clutch would also help the kart accelerate better, because it slips at lower RPM just like a Torque Converter in a cars automatic transmission.

_______

If the 6.5hp. karts at your racetrack have 18:36 gearing, to achieve 60 kp/h (37-mph), that means their engines are equipped with a 2:1 gear reduction box installed on the output shaft. Those gear reduction boxes look like the picture I've posted below.

If your engine is not equipped with the (optional) gear reduction box like that picture, but you wanted the same top speeds on that track:
I'd suggest you use a 12-tooth clutch (or solid drive gear) on the engine. And a 53-tooth axle sprocket. (thats if using a #35-pitch chain/sprockets)

Because that gearing combination would give you an estimated top speed of 60 kp/h (37mph), with 11-inch (or 279.4mm) tall rear tires, and an un-governed engine running at 5000rpm.

 

[BerlanBBM]

@Benny
The engine gots a rpm of ca. 4600


@anderkart
Where can i get those gearboxes and are they easy to install? Thx for ur great post!

@jman
Thx!

 

[anderkart]

Your welcome, but you dont need (or even want) an expensive reduction box like that anyway...

Those extra gears would just add additional friction, (reducing-acceleration and top speeds...) and besides that, you could always achieve any gear ratio you'd ever need (for different race-tracks) by carefully selecting/replacing your clutch/drive-gear and axle sprockets...

 

[landuse]

Post a pic of your engine for any further help. We are getting confused

 

[BerlanBBM]

@ anderkart Also i dont even need a gearbox but a clutch would be useful?

@ landuse Gimme ca. 3 days then pictures will come

 

[BerlanBBM]

This are the pics of the engine Quite earlier!

 

[landuse]

@ anderkart Also i dont even need a gearbox but a clutch would be useful?

@ landuse Gimme ca. 3 days then pictures will come

A clutch would be VERY useful. Without one you would never be able to stop without your engine dying. You would also not be able to start the engine with it taking off on you.

Seeing that you do not have that reduction gearbox on your engine, you are going to have to gear for approximately 6:1. This will mean getting a clutch with 10T and axle sprocket with 60T, or a clutch with 12T and axle sprocket with 72T etc. 18:36 will not work. Period!!