Newbie

[waikikigirl]

Hey Im from South Africa and..... NO we do not have lions as pets lol

Im studying mech. eng at Uni (one of the few girls) and work in HVAC industry.
Im currently busy doing a project on different drive systems of karts:
Chain, drive and direct - which of the three perform better,cost,etc etc

and i stumbled across this forum while doing research.

I wanna get feed back from the guys that actually drive them and not just the theory behind it all...

Thanks

 

[landuse]

Hey Im from South Africa and..... NO we do not have lions as pets lol

Dangit!!! Don't tell them that! It has taken me years to convince them that I ride an elephant to work.

Welcome to the forum!!

There are a few drive systems that are used on karts.

1) A centrifugal clutch with a sprocket on it going directly to the axle sprocket. This is chain driven. You can also get a centrifugal clutch with a pulley instead of a sprocket. Tis would use a belt that would go to a pulley on the axle.

2) A torque converter, or CVT (continuous Variable Transmission). The most common make is Comet (you can google it for pics) It uses a driver and a driven, which are belt driven. You then have a sprocket going from the driven to the axle. So here you have a combination of belt and chain.

3) Direct drive would be from a sprocket on the engine shaft, directly to a sprocket on the axle. This is not so common, because it means that the engine will stall each time you stop. It would be like stopping your car without pushing in the clutch pedal. Some racing karts (not too many IIRK) use this system, cos there is no need to stop during the race

Costs?? Direct drive would be the cheapest. A centrifugal clutch would be the next in line. Next would come he TC. The higher the HP your engine has, the more expensive the TC becomes to handle the power

I am pretty sure other members will give you better info than I have, but I hope this helps for a start.

 

[waikikigirl]

awesome thanks...
Basically Ive gotta design a 10hp = 7.5kW drive system @ 1000rpm
for chain , belt and direct with the sprocket sizes,gear ratios etc
and then compare them

 

[landuse]

awesome thanks...
Basically Ive gotta design a 10hp = 7.5kW drive system @ 1000rpm
for chain , belt and direct with the sprocket sizes,gear ratios etc
and then compare them

Just remember that tyre diameter and kart weight will play a big role in final gear ratio. Especially the tyre size.

Will this be electric or petrol driven? I see you mention kW, that why I ask

 

[Doc Sprocket]

Paul, (landuse) my whole image has shot to crap. Thanks a ton, my man.... LOL

Welcome, waikikigirl!

The info above pretty much covers it in a tidy little package. We can give you futher information as you go along.

 

[landuse]

Paul, (landuse) my whole image has shot to crap. Thanks a ton, my man.... LOL

She doesn't know what she is talking about

 

[itsid]

..AWESOME I've been waiting for you

...
Im currently busy doing a project on different drive systems of karts:
Chain, drive and direct - which of the three perform better,cost,etc etc
...

That's great and I'd love to see the results!

What I've found so far on information was that a CVT belt transmission
has an efficiency ratio of less than 80% (average of 77 IIRC)
Some power is always converted to heat (belt slip)

A cent.clutch typically runs above 80%
(depending on the exact spring&shoe setup even above 90%)
again the rest is heat.

while as a direct driven kart is running at 100%.
which in fact is the main reason for small race karts to be direct drive if the class allows it..
10% more power on the wheels

I'd really love to see that being tested by ONE person and ONE engine in a scientific manner to verify the values.

every bearing will eat on the efficiency as well, but I'd expect no more than 1-2% loss on race kart 2-3% on a yard kart
for the rear axle and maybe the same if a jackshaft is needed
(which adds two more bearings).

If you don't mind I'd like to PM you about that topic.. I really would like to know your results

'sid

 

[waikikigirl]

lol yeah i dont

Its a petrol engine, the drive shafts loaded by 2.5kN
12" tyres (im guessing)

 

[OzFab]

Wait a minute, by my understanding, the term "direct drive" involves nothing between the engine PTO shaft & the wheel; am I missing something?

 

[firemanjim]

 

[Poboy kartman]

Paul, (landuse) my whole image has shot to crap. Thanks a ton, my man.... LOL
.

Well. ...he only bent the truth a little. ....better to be seen as a guy riding an elephant to work. .....than an automotive dinosaur !!!!

They're both big and slow......
Ugh
One's a gas guzzler....the other a grass guzzler.....

And you don't want to be behind either of them when they emit exhaust gas. ...:lolgo
EDIT: BTW: Welcome Wackigirl..!!!!!!!

The New Orleans Saints have a saying for their football team:...." Who dat?"

I think Hawaii ought to have one too....."Hula be coming to the luau?"....

 

[landuse]

Wait a minute, by my understanding, the term "direct drive" involves nothing between the engine PTO shaft & the wheel; am I missing something?

That is also how I see it. Maybe Waikikigirls should explain to us how she sees it, just so tha we all have a clear idea

 

[itsid]

direct driven go karts are not engines with a wheel attached to it, they're still geared.. there's just no clutch.
Book: Bob Bondurant on Race Kart Driving

'sid

 

[machinist@large]

That's great and I'd love to see the results!

What I've found so far on information was that a CVT belt transmission
has an efficiency ratio of less than 80% (average of 77 IIRC)
Some power is always converted to heat (belt slip)

A cent.clutch typically runs above 80%
(depending on the exact spring&shoe setup even above 90%)
again the rest is heat.

while as a direct driven kart is running at 100%.
which in fact is the main reason for small race karts to be direct drive if the class allows it..
10% more power on the wheels

I'd really love to see that being tested by ONE person and ONE engine in a scientific manner to verify the values.

every bearing will eat on the efficiency as well, but I'd expect no more than 1-2% loss on race kart 2-3% on a yard kart
for the rear axle and maybe the same if a jackshaft is needed
(which adds two more bearings).

If you don't mind I'd like to PM you about that topic.. I really would like to know your results

'sid

Wiki, I'd like to add my as well....

Alex, you usually blow me out of the water on the numbers side when it comes to the deep foot notes, but based on what I have seen on the commercially available side, I'm guessing that your 80% rating for CVT setup's is probably the upper end, perfect world scenario. Look at how many RFA's we get for belt drive help... Otherwise, I bow to the better researchers.....

 

[itsid]

Wiki, I'd like to add my as well....

Alex, you usually blow me out of the water on the numbers side when it comes to the deep foot notes, but based on what I have seen on the commercially available side, I'm guessing that your 80% rating for CVT setup's is probably the upper end, perfect world scenario. Look at how many RFA's we get for belt drive help... Otherwise, I bow to the better researchers.....

yupp, that's why I said less than 80%
I can't recall the exact min or max-number I've read..
since that wasn't too important for me (I can't even recall the source ATM to be honest)
but the higher the internal ratio the worse it gets

Torque converters are great.. but they wouldn't sell ONE if they would print their efficency on the box
NEW: efficiency now as low as 40% in low gear
... nah, that doesn't read too well

So I'm pretty curious about what waikikigirl will come up with for kart transmissions specifically.

'sid