Centrifugal disk clutch capabilities

[J.S.@SMS]

I am in the planning stage of a kart that I will be building over the summer and I am not sure what clutch to use. It's a carter 2575 that I will be trying to keep under 150-200 pounds. It will have a stage two predator 212 with an upgraded intake, 22mm mikuni carburetor and an open header. I'm hoping for about 20-25hp. I will also be using 11 inch tires on racing wheels.

The clutch that I would like to use is the bully 3 disk 6 spring clutch which is rated for 30hp.
https://www.gopowersports.com/bully-3-disc-6-spring/

My question is, Is it possible to gear this setup for 60+ mph or would that put too much strain on the clutch.

PS: I do not plan on driving the kart at 60 miles per hour, but I would like the extra speed for drifting. And this kart will likely be used off road for drifting in an open field that's flat, mostly level and covered in grass as well as on road.

 

[landuse]

60mph? Those speeds are not that easy to reach at all. What gearing are you thinking of?

 

[J.S.@SMS]

I was thinking of a 12 tooth sprocket on the clutch and a 53 tooth sprocket on the axle, which is a 4.4:1 ratio. I ran the numbers on kartcalc and it seems to think that with a 300 pound overall weight a 4:1 gear ratio will work, so the 4.4:1 should work. But my question is will that clutch hold up well enough with this ratio.

Another question that I thought of is whether to use a 1 1/4" racing axle or a 1" steel axle. The racing axles only come in lengths of 32" to 40" in 2 inch intervals, however I know where I can get a piece of 1" steel bar, in any practical size, cheap and my dad has a friend who works at a machine shop who can mill the key-ways.

And as I said before I don't plan on driving it at 60 mph on the road. It would be too difficult to control since I will be using the smallest amount of caster that I can (probably 2-3 degrees). About the only on road driving that I will do is drifting in parking lots in the early morning or late evening (if I can find a place that will let me drift in their parking lot). This kart will mostly be used off road in a field at up to 40 miles per hour. The reason that I want the extra speed is so that I can drift easily.

 

[ezcome-ezgo]

I also hope you achieve 20-25hp out of a 6.5 hp industrial engine. But alas, I know that you will not. A solid target is about 9hp.

 

[J.S.@SMS]

So by removing the governor, adding a billet rod, billet flywheel, 292 cam, upgraded rockers, larger intake valve, upgraded exaust valve, 36lb valve springs, upgraded push-rods, upgraded lifters, an open header, a 24mm slide carb, and an air filter, with shaving the head (for a 12:1 compression ratio), and porting and polishing the head the engine only gains 2.5hp, whereas a stage two kit (rod, flywheel, 262 cam and 22lb valve springs) produces 15 hp? I do believe that you are wrong (unless you are talking about a stage 1 kit, in which case you are right. Stage 1 = 9 hp).

These parts can be found here:
https://www.gopowersports.com/racing-performance-parts/performance-engines-parts/

 

[ezcome-ezgo]

As I said I hope you succeed, but even at the GPS page you linked, 11hp is the top of the curve. Doubling the stock hp of an engine is very impressive. By all means, prove me wrong and have fun doing it.

 

[Joe-405]

I actually have most of the stuff you listed with the carb exception and mine makes 12-14 hp. Off the box stock project dyno.

 

[dman]

Someone can correct me if I'm wrong but unless you're planning on only one powered wheel you would want a torque converter (cvt) to have the sudden torque to start the slide it sounds like you want for drifting. With a centrifugal clutch you want smaller tires and you still might but though faster that you should. Aim for higher torque in your build

 

[Joe-405]

If he’s gonna use pvc sleeves he will be fine. But if he’s not it will be hard to make enough off the line power to actually drift the tires with any small engine anything. I would think you would need at least a 250cc bike engine or bigger to achieve that goal without some kind of add on to aid in spinning the tires easier.

 

[itsid]

I was thinking of a 12 tooth sprocket on the clutch and a 53 tooth sprocket on the axle, which is a 4.4:1 ratio. I ran the numbers on kartcalc and it seems to think that with a 300 pound overall weight a 4:1 gear ratio will work, so the 4.4:1 should work. But my question is will that clutch hold up well enough with this ratio.
...

uhm
KartInfo by kartcalc.net:

[FONT="Verdana"]
[B][U]KART[/U][/B]
[INDENT][I]RW diameter[/I]: [B] 11 in | 27.94 cm[/B]
[I]Total weight[/I]: [B] 300 lbs | 136.08 kg[/B]
[/INDENT]
[B][U]ENGINE[/U][/B]
[INDENT][I]Original HP[/I]: [B] 7[/B]
[I]Asummed HP[/I]: [B] ~7.81[/B]
[I]Torque[/I]: [B] 10.21 ft lbf | 13.85 Nm[/B]
[I]RPM[/I]: [B] 5500[/B]
[/INDENT]
[B][U]TRANSMISSION[/U][/B]
[INDENT][I]Final ratio[/I]: [B] 4.42:1[/B]
[/INDENT]
[B][U]PERFORMANCE[/U][/B]
[INDENT][I]Max Wheel Torque[/I]: [B] 45.15 ft lbf | 61.22 Nm[/B]
[I]Top Speed[/I]: [B] 40.72 mph | 65.53 km/h[/B]
[/INDENT]
[B][U]PROBLEMS[/U][/B]
[INDENT][B]You might burn your clutch/belt![/B]
[B]Gear ratio too high![/B]
[I]Suggested final ratio[/I]: [B] at least 6.02:1[/B]
[/INDENT]
[/FONT]

just sayin'

'sid

 

[J.S.@SMS]

ezcome-ezgo, Honestly doubling the stock hp of these engines inst too impressive, as a predator 212 is 12.93 cubic inches, and twice the stock power is 13hp (about 1hp per cubic inch).

dman, I do not think that a cvt will work at speed that this engine will be turning. And I'm not planning on using torque to start the drifts, I'm planning on using the braking system.

Joe-405, I am thinking of using a different gear ratio for on road use, But I plan on using this kart mostly in open fields.

And itsid, Those numbers are for a stock engine. Run it again with 14hp (it will assume 11.51) and 8000 rpm.

PS: I can get my Ken Bar Streaker DD9 with a 12 year old Tecumseh 6.0 a 6" driven and 6:1 gearing with 22" knobby tires to slip the rear end slightly where I'll be riding.

 

[itsid]

torque converter benefit on the KenBar..

anyways.. sure, if you HAVE 14 horses.. and CAN rev up to 8k under load.
I wouldn't be too sure about that tbh.. but yeah if, then yes...

Just one minor concern: std cent clutches are still going to have a very rough time with such gear ratio..
the problem is that you will have a fairly high full lock speed with 16.3mph
(road speed where the clutch can fully engage and stops slipping;
usually at the engine speed of 2200 rpms)
with that little torque on the wheels (due to the ratio),
you will have a hard time reaching that speed quickly enough for your clutch not suffering eventually.
Keep in mind if you go any slower than 16.3mph the clutch MUST slip
and thus create heat and wear out..
not to mention it's also not transmitting all the power to the axle of course
which in turn lessens the torque to accelerate quickly enough even further

It's not impossible to make that work (assuming your claimed power is correct)
but personally I'd say you should at least get a racing clutch that's more resilient
than say a Hilliard Inferno or a MaxTorque SS.

'sid

 

[J.S.@SMS]

That claimed power is not correct. I used a lower rating than the engine should put out. Also the clutch that I was planning on using is linked in the first post.

Is it possible to use a 40 series with a 44c driver, or a 780 with a 3/4 bore driver for the carter? (I was just using the ken bar as an example of the traction conditions (and I do have the parts that were needed to fix the gearing issues.)

 

[Joe-405]

I used the 44c magnum driver with a 40 series driven on my mini dragbike build from last year.

 

[J.S.@SMS]

How high did that engine rev? I would like to have a TC but I don't know if a 44c driver can handle the rpm.

 

[Joe-405]

6240 consistently was ok. I added a billet flywheel for faster revs and more timing for more rpm and it melted the internal rubber pucks.