Ted Hamilton
Helmet Painter / Racer
Can I get by with a 2 disc on a 100cc 2 cycle piston port? Engaging somewhere around 9,000 engine RPM.
TIA,
~Ted
TIA,
~Ted
2 disc or 3 disc - 100cc Limited UAS
- Thread starter Ted Hamilton
- Start date
Ted Hamilton
Helmet Painter / Racer
Thanks guys....on jackshaft. Now to browse the classifieds or call Shannon Halbert...
I've been going with 2 disc on pretty much every 100cc build for awhile now. No bigger than a 3 disc. Testing a single disc using parts from the new clutch design coming out, should be the fastest of the bunch
-Shannon
alvin l nunley
Site Supporter
More details!
Dry clutch wet clutch? Exhaust? Track?
With our Horstman tDXL, wet clutch, we were very successful with a 3 disc. I can see no compelling reason to go with a 2 disc.
With a pipe, assuming a KT100, it reaches peak torque at 10,300, plus or -100 RPM. With a 4 hole can, about 9300 RPM. That's where I would set my clutch.
We always set the carburetor, WB 3, at about 1/4 top and 2 – 2 1/2 on the bottom. 2 1/2 on the bottom is fully open.
A good KT100, will pump it's about 160 psi compression pressure, very important. We used a Snap-On gauge.
Ted Hamilton
Helmet Painter / Racer
Al -- on jackshaft. Dry clutch. 2 disc. I got my answer, though I'll be curious to chat with Shannon about his 1 disc solution....that's a lot of torque for a single disc...
alvin l nunley
Site Supporter
Single disc with a Jack shaft!!! I've considered switching to a 4 disc, from a 3 disc, without a Jack shaft! It's my theory that the harder a disk has to work, the more heat it will generate. Heat is a power loss.
My main concern would be generated heat!
We won't be using traditional clutch discs. These discs have 2.25 times the surface area as a regular kart style clutch disc. Testing so far using our Single Disc clutch with the standard clutch disc on a stock KT100 at 9800rpm engagement has provided 5 wins in 5 weekends on 2 different karts. Heat is exchanged from the discs, to the extra thick pressure plates, then out of the aluminum basket. Slipping the clutch the proper amount helps with heat incredibly as well.
We have been testing different theories one at a time for several months now. This new clutch will not be an adapted current clutch with something a bit different. I am designing it from scratch, starting with a blank sheet and plenty of ideas.
-Shannon
Pete_Muller
Moderator
Ted,
The two things which probably determine what kind of abuse a clutch needs to withstand -- gear ratio and weight of the complete kart (or more precisely: a combination of the two).
Put a piston port on a 400 pound road race kart with a ridiculously tall gear ratio (like one might run at Daytona), and it's unlikely that even a 3-disc engine oil clutch would hold up very well (why axle clutches are popular for that form of racing).
Run the same engine on a lightweight or junior class kart, at a small track with a crazy low gear ratio, and you could probably run a single disc clutch for a season without touching it.
My guess is that you're closer to my second example than the first.
PM
rainman
Member
You are so right, Pete. My P51 on a sprint trach with a very light chassis has a dry clutch, low stall, and it lasts forever.Ted,
The two things which probably determine what kind of abuse a clutch needs to withstand -- gear ratio and weight of the complete kart (or more precisely: a combination of the two).
Put a piston port on a 400 pound road race kart with a ridiculously tall gear ratio (like one might run at Daytona), and it's unlikely that even a 3-disc engine oil clutch would hold up very well (why axle clutches are popular for that form of racing).
Run the same engine on a lightweight or junior class kart, at a small track with a crazy low gear ratio, and you could probably run a single disc clutch for a season without touching it.
My guess is that you're closer to my second example than the first.
PM
Ted Hamilton
Helmet Painter / Racer
Requirements for limited UAS are: 350# I'll have a Comer P50 on gas (for now), no fuel tech. I guess I could add some nitro? 19:53 jackshaft ratio, for around 2.79. To engage at 9000 engine RPM puts the clutch engaging at 3200.
After reading Shannon's post, I may have to try his new single disc. My concern is primarily longevity, with minimal rebuilds and minimal maintenance, to allow me to focus on tires and driving.
19:53 jackshaft ratio, for around 2.79. To engage at 9000 engine RPM puts the clutch engaging at 3200.After reading Shannon's post, I may have to try his new single disc. My concern is primarily longevity, with minimal rebuilds and minimal maintenance, to allow me to focus on tires and driving.
Ted Hamilton
Helmet Painter / Racer
@Pete_Muller -- Speaking of axle clutches, I've designed a new axle clutch -- basically an overgrown Bully-style that is a dry axle clutch using Harley friction discs (or Ducati, but.....cost.) Just haven't had a good reason to actually prototype it yet. Would allow for easy change of ratio / engagement, but it's a lot of spinning unshielded stuff...
Pete_Muller
Moderator
I should have added one more item to my post above -- which rainman eluded to: the exhaust pipe.
So let's change my previous post to: a combination of weight and gear ratio, PLUS the power characteristics of the exhaust pipes.
Be on the "wrong" side of all those, and keeping a clutch alive for any length of time is a challenge at best. Be on the good side (light kart, low gear ratio, and an exhaust pipe with a broader/softer powerband), and a light, possibly single-disc clutch will last a long time.
- - - -
Ted,
Something to possibly consider is that friction discs for a motorcycle may not have the characteristics that are ideal for a kart. The key thing is the difference between static and dynamic coefficient of friction. If that "spread" is too wide, the clutch may tend to "drop-in" a bit much (rpm drop at engagement) and possibly not "unhook" very well as revs drop. Both of those issues can be solved (or "tuned") by adding more spring and more weight, possibly changing material/hardness of floaters, etc., but it could still be something to think about.
It's all tunable with some creativity, no doubt.
Would love to see your design!
PM
So let's change my previous post to: a combination of weight and gear ratio, PLUS the power characteristics of the exhaust pipes.
Be on the "wrong" side of all those, and keeping a clutch alive for any length of time is a challenge at best. Be on the good side (light kart, low gear ratio, and an exhaust pipe with a broader/softer powerband), and a light, possibly single-disc clutch will last a long time.
- - - -
Ted,
Something to possibly consider is that friction discs for a motorcycle may not have the characteristics that are ideal for a kart. The key thing is the difference between static and dynamic coefficient of friction. If that "spread" is too wide, the clutch may tend to "drop-in" a bit much (rpm drop at engagement) and possibly not "unhook" very well as revs drop. Both of those issues can be solved (or "tuned") by adding more spring and more weight, possibly changing material/hardness of floaters, etc., but it could still be something to think about.
It's all tunable with some creativity, no doubt.
Would love to see your design!
PM
alvin l nunley
Site Supporter
Pete, looking at this from a different direction, do you have any thoughts on the negative and/or positive side of running either 2 or 3 discs? Maybe 4?
My personal (unsubstantiated) feeling is more discs have more positive benefits versus negative.
My personal (unsubstantiated) feeling is more discs have more positive benefits versus negative.
Brian Montgomery
Member
My personal experience with dry clutches has never been good. I’ve ate up disk and even have snapped hubs before. I’ve run Birky’s most the time and never had an issue. Reliability is a huge factor for me. Jhmo
Ted Hamilton
Helmet Painter / Racer
@Pete_Muller -- Msg. me your email if you don't mind, and I'll send some JPGs of the clutch. I've been designing it in SolidWorks...
@Brian Montgomery -- was that using the clutch on a j/s?
@alvin l nunley - More discs and floaters = more weight = more to stop and start. Whether the "Flywheel effect" helps or hurts you probably depends on your powerplant and track type.
@Brian Montgomery -- was that using the clutch on a j/s?
@alvin l nunley - More discs and floaters = more weight = more to stop and start. Whether the "Flywheel effect" helps or hurts you probably depends on your powerplant and track type.
Al,
I've been moving toward the idea of Less is More with these lower powered engines. The less mass we are moving, not necessarily centrifugal force, but the movements of the clutch as a whole, the less energy we are consuming. Efficiency as we know is energy in/ energy out. What I see by reducing the number of moving parts in this dynamic system for one is reducing the number of parts that must align as the clutch packs go from open air gap, to closed. The friction discs aren't held in by anything but the basket tabs, and the floaters aren't aligned to anything other than the friction discs and the front and back pressure plate once it's closed. Slow motion video we can watch the floater and discs move quite a bit during on and off throttle usage and at idle. Every time the clutch engages, all of these pieces must come into alignment each time. Until it's fully engaged everything kind of bounces around in there.
The new design is less moving parts with larger surface area. The basket assembly will not accept a snap ring style drive sprocket to wear out and provide excessive slop. The drive plates will contact the basket in a way (which I cant discuss yet) that will provide 360 degree support. There is plenty more, but I've went off topic a bit.
A thought.... A formula 1 car uses a 3.8" diameter clutch containing 4 discs that can transfer 1000nm of torque. There is an incredible amount of knowledge we've not yet explored.
Second though..... There is a good amount of effort to make sure the pressure plates are flat and parallel, how many folks are checking the friction discs to see if they are perfectly flat also ?
-Shannon