Brand new Kart , 2nd clutch !!!!

[Athenryeng]

Hi Guys , Finally got kart finished , burnt out 1st clutch after half an hour ! Got some smaller diameter rear wheels , burnt out second clutch after half an hour !!! Have 10 teeth on clutch , 50 teeth on axle and 15 inch dia wheels . Kart goes real fast on roads ( too fast really ) but on grass where we intend to use it it is really struggling . Have decided to bite the bullit and get a Torque converter , thinking of a comet 30 , engine is 6.5 hp . Has anyone got any good links to show photos of these on a kart ? Also does anyone know of a supplier that will ship to Europe at reasonable cost ? Thanks Guys

 

[Athenryeng]

Photos added

Sorry Guys , Thought i had photos attached

 

[r_chez_08]

Cool kart
you have 2 options:
1. regear
2. install a comet torque converter.
If you are happy or nearly happy with your current acceleration, then I would regear. Your current top speed is approx 32mph with stock engine configuration.
That is a little high. If you could find a 60t or higher sprocket and install it your clutches would last a lot longer. What chain are you running? this will cost you 10-40 euros (you work in euros, right?) for the sprocket, depending on how common they are in ireland.

If you want more low end and clutch life, and 10% more top speed you could buy a comet 30 series for about £200 (dunno in euro) from geminikarts.com. Yeah it is expensive, but they are very good.

In you're situation, if you find your kart is going too fast, then I would gear as low as you can with a top speed you are happy with, e.g. if you are happy with 20mph, then gear for 20mph, not for 32 mph because you are wasting torque!

 

[the-cyborg]

Cool kart
you have 2 options:
1. regear
2. install a comet torque converter.
If you are happy or nearly happy with your current acceleration, then I would regear. Your current top speed is approx 32mph with stock engine configuration.
That is a little high. If you could find a 60t or higher sprocket and install it your clutches would last a lot longer. What chain are you running? this will cost you 10-40 euros (you work in euros, right?) for the sprocket, depending on how common they are in ireland.

If you want more low end and clutch life, and 10% more top speed you could buy a comet 30 series for about £200 (dunno in euro) from geminikarts.com. Yeah it is expensive, but they are very good.

In you're situation, if you find your kart is going too fast, then I would gear as low as you can with a top speed you are happy with, e.g. if you are happy with 20mph, then gear for 20mph, not for 32 mph because you are wasting torque!

I say no matter what you do you still need to re-gear.
5:1 ratio is way too steep, you's be better off somewhere around 6:1 to 8:1 ratio 72/10=7.2:1 would give you decent top end, and powerful low end torque.

 

[Russ2251]

I'll say it again...rear sprocket (with centrifugal clutch) should be within 2" of tire diameter.

 

[supermanotorious]

I'll say it again...rear sprocket (with centrifugal clutch) should be within 2" of tire diameter.

given a #35 vs #40 chain you'd have a pretty large difference in ratios

 

[Athenryeng]

Thanks for all the advice , im actually machining up a new sprocket at moment it will be 60 teeth , just because i had a piece of steel that dia ( 276 mm ) handy and also the length of chain should still fit by pulling the engine right back . The torque converter definetly sounds way to go for sure . Whats confusing me though is sometimes people talk of teeth ratios on torque converters ?? is it not just a pulley and belt and looking at the diameters of the pulley for the Comet 30 i will have to do a fair bit of rework with the set up of existing axle .

 

[Athenryeng]

Chez , just checked out the Gemini website , dont know how i didnt find that site before , they have a Max Torque complete unit for £ 126 , what do you think ? Thanks Andy

 

[Russ2251]

Should be closer to 100 teeth for #35 or 120 teeth for #40.

 

[Athenryeng]

Thanks Russ , the chain im using is a 420 , i just copied the pitch and circumference of the 50 tooth sprocket and worked backwards to get 60 teeth , have only machined 3 teeth so far but it looks about right.

 

[Bluethunder3320]

a torque converter with that 50T will be fine. i have a 50T on my mini bike with 10hp and 19" tire. it has insane torque i could even gear it higher because the engine doesnt break a sweat at all.

 

[r_chez_08]

given a #35 vs #40 chain you'd have a pretty large difference in ratios

A bit of a difference,
e.g.
smallest redily available teeth on a 3/4" clutch
#40 = 10t
#35 = 12t

2" smaller than 15"= 13"

13" #40= 82T
13" #35= 109T

#40 ratio=8.2:1
#35 ratio=9.1:1

I'll say it again...rear sprocket (with centrifugal clutch) should be within 2" of tire diameter.

Is this even with a bigger motor?

I say no matter what you do you still need to re-gear.
5:1 ratio is way too steep, you's be better off somewhere around 6:1 to 8:1 ratio 72/10=7.2:1 would give you decent top end, and powerful low end torque.

I have 6:1 and 18" tyres with my 6.5 and a tc. Its a little steep but since he is making a 60t he should be fine.

Chez , just checked out the Gemini website , dont know how i didnt find that site before , they have a Max Torque complete unit for £ 126 , what do you think ? Thanks Andy

£126+ 20% tax.
It does not come with a backplate or jackshaft, so you would have to make or buy a jackshaft, sprocket and bearings.
for the extra £25 (£30 inc tax) I would take the tav2 made by comet. It is easier to mount, and you can easily spend £30 on a jackshaft, two bearings and a sprocket.

When people talk about the number of teeth on the torque converter, they are talking about the number of teeth on the jackshaft, coming off the driven. This is similar to talking about the teeth on your centrifugal clutch.

 

[landuse]

If it was me I would try the 60th sprocket out first with your cent clutch. If it works fine then leave it like that. A TC is an expensive piece of equipment to buy if you don't really need it.

Just my 2c worth......

 

[Athenryeng]

Thanks for all the advice , you start to get a good understanding of things when they dont work !!!!! Made a new 60 tooth sprocket today and think i have managed to salvage at least one of the cheap clutchs , ( polishing & tighting spring ) will just have to remount engine so i can keep original chain and try here out . Will let you know how it works out , also i have much better grasp of how the tc works now !! i thought it was just a pulley and no chain at all !!! Once again thank you all.

 

[Athenryeng]

Chez , just reread your reply , with the comet TC , i wouldnt need jackshaft etc ??? I thought i was just starting to understand them , now im confused again !

 

[r_chez_08]

a go kart torque converter consists of two pulleys and a belt. As you increase rpm, the driver pulley "expands" and grabs the belt, turning the driven pulley. In lowest ratio, this is around 2.43:1, which id obviously not low enough to mount the driven pulley on the axle, because your motor would not have enough torque. Instead it is mounted on a shaft, the jackshaft, usually 5/8" or 3/4". you then secure the driven with a keyway. you then mount a sprocket on the jackshaft. this is usually a similar number of teeth to a centrifugal clutch, 10t -20t or so. You then have your normal axle sprocket.

In your case, you would have a 10t on the jackshaft and 60t on the axle.

back to the tc. as you rev up and the load decreases on the engine, your driven pulley expands, and your driver continues to expand also, leaving you with approximately a 1.1:1 ratio- 10% overdrive, or 10% more speed.

The comet tav2 tc has a jackshaft and a backplate, bearings and a sprocket, all in a neat little package. the maxtorque requires a jackshaft for the driven to mount to, then a sprocket and 2 bearings. it also may require additional fabrication.

here is my comet 40 in action. the maxtorque would have to be set up similarly. Please ignore the wobbly wheels and exhaust, they are all sorted.
http://www.youtube.com/watch?v=yl4ohC9pKJ0

Here is the driven of an older comet 20 explained
http://www.youtube.com/watch?v=SA89rve8Bn8&feature=related

Here is a video of a fake comet tav2. The genuine are a lot better. You then clip the cover on, protecting the unit.

http://www.youtube.com/watch?v=Cig3nN0IPEo&feature=related

Hope that helps

 

[Athenryeng]

Makes sense now thanks , have e-mailed Gemini karts on delivery for the TC you recomended , Thanks

 

[r_chez_08]

I would definently try the centrifugal clutch first, because the tc may be an unneccesary expense.

 

[landuse]

I would definently try the centrifugal cllutch first, because the tc may be an unneccesary expense.

X2

 

[Athenryeng]

Thanks for all great advice , a picture really is worth 1000 words ! Im kind of confident new sprocket will work out and am starting to think of a track to drive it on . I have an old bit of overgrown weed filled field about 2 acres and am planing on spraying weed killer onto in the shape of track . Here is the question , it will be my kids riding kart and i was thinking of something very twisty and turny to try and slow them down abit , but after all the stuff i have read about cluches recently , im thinking that lots of power on -off -on etc wouldnt be to healthy on the clutch . So i may just go for a big oval track and just reduce speed of kart so kids dont kill themselves ( wife wouldnt be happy with me then ! ) What do you guys think ?