Track Tac

calling clutch pros

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subbietjw

Member
lets start with the short story first... taking the step out into the adjustable drum clutch... I've stuck with my maxtorque clutches for a long time!!! gave my norm a try once be for but burnt the shoes up n set the build and clutch in the bad motor box... so now its back out so I need the "drum clutch theory" run down in simple form... so heres what im looking for... first I run sprint course not oval track...I need this clutch to be like my max torque but with a lil quicker pull off the corner... I picked the norm for 2 reasons.. 1 it has the hard lock up setting and springs that run the from next to nothing to 5,000+rpm...

with all that said I know the hard lock up is just too aggressive after testing.. so I know I need to run the middle to soft setting.. I have a rough set up working now.. with the middle setting, light shoes, and red springs.. but im getting a lot of heat off the clutch and its got a lot of drag (if that makes since?) im wondering if im better off going to the soft setting with a light shoe? or if im better off going to the heavy shoe with soft setting? I just don't know the fundamentals of clutch tuning... I get rpm sends out the shoe the shoe rubs the drum tell its fully pushed into the drum and fully locked up... that's a bout it... lol
 
If a clutch is holding the engine at peak torque, and isn't producing a lot of heat, (more than the other clutch) there's no difference in pull off the corners. Pete Muller used to have an article on his site that explained how a clutch with heavy shoes and strong springs locks up tighter on the top end, better than a clutch with light shoes and weaker springs. Centrifugal Clutches never lock up 100%, but heavy shoes with stronger springs get closer to 100% than light shoes with light springs. The increase in force exerted against the drum, as the clutch spins faster, is a square function. If the light shoe is exerting two pounds of force, the heavy shoe will be exerting four pounds of force. It's not really a good explanation but it will give you the idea.
 
alvin l nunley said:
If a clutch is holding the engine at peak torque, and isn't producing a lot of heat, (more than the other clutch) there's no difference in pull off the corners. Pete Muller used to have an article on his site that explained how a clutch with heavy shoes and strong springs locks up tighter on the top end, better than a clutch with light shoes and weaker springs. Centrifugal Clutches never lock up 100%, but heavy shoes with stronger springs get closer to 100% than light shoes with light springs. The increase in force exerted against the drum, as the clutch spins faster, is a square function. If the light shoe is exerting two pounds of force, the heavy shoe will be exerting four pounds of force. It's not really a good explanation but it will give you the idea.
Click to expand...

I get the last part but I don't get the first part... "If a clutch is holding the engine at peak torque, and isn't producing a lot of heat, there's no difference in pull off the corners." so it should be hot as $hit? the drum is blue and rainbow... in my eyes that a hot chip coming off the lath... blue is too hot... wouldn't it be too hot in this case too?
 
Just the opposite. Heat is a power loss, if the drum is getting blued, that's too hot, way too hot. The cooler the clutch, the better. As long as it's holding the engine at peak torque, and not producing a lot of heat, they're all the same. That is they're all transferring similar amounts of torque to the rear axle.
 
I would want the clutch that is transferring the most amount of torque to the rear axle.

Once the clutch is locked up, it is essentially 1:1. Up to that point, there is a great difference in how efficient a clutch transfers that torque. More heat = less efficient. Cooler is better (Al's right on that one.)

On a Noram GE series clutch, you've got two different weight shoes to choose from (light = 150g & heavy = 200g.) I prefer the heavy shoes and white springs for a 3800-4000 rpm lock up. Your current set-up of light shoes and red springs is about the same lock-up.
You'll notice that the 3 slots in the shoes of your light shoes are symmetric -- that is, you can reverse the shoes and you still only have 3 choices for engagement. Now, look at the heavy shoes. There are only 2 slots, but they are not symmetric, so if you reverse (flip over) the shoes, you've actually got 4 different choices for installation. I ALWAYS preferred to "pull" the shoes so that they swing out behind the driving dogs on the hub. If you "push" the shoes, they will be very aggressive with lots of chain jerk, chatter, rebound, etc.
When this was one of the more popular clutches in 4 cycle racing, we would spend extensive time blueprinting these clutches (machining the drums concentric (perfectly round), machining the shoes and weight matching them, matching spring pressures, etc etc.) Since those days, Gil Horstman revolutionized karting by introducing the MDC disc clutch and clutches have gotten better and better ever since. They're not all created equal. Some are just plain better than others. Sure, they all "can" and "do" work, just some work much better than others.
Interestingly, I still use a Noram GE clutch with heavy shoes and the lightest springs on our dyno here in the shop. It allows the engine to be started and idle, but once it is locked up, it is no longer slipping "measurable" power away. It requires very little maintenance, stays consistent, and has lasted for many years.


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Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
26 years of service to the karting industry
765-339-4407
bcarlson@CarlsonMotorsports.com
 
that was vary help full! heres my next question... so far with this clutch im seeing this... when I take off instead of it holding an rpm (example) 3500rpm and as I give it gas it hold that rpm.... it will keep going up in rpm to say 4300... then theres a point where the wheels and motor start to reach that 1 to1... the motor will start to loose rpm then theres a jerk... and its locked up... what is that all a bought?

cause in this setting (middle engagement) I tried the black then the red spring... the black spring was too low of an rpm setting it was trying to engage at an idle or a hair off idle... (idle for this motor is around 2000-2200rpm)
 
All these clutches slip past the desired engagement, then rpm drops when full lock-up is encountered. The first time that your rpm drops is your actual engagement rpm. It's very easy to see visually with the bar graph on your Mychron rather than watching it numerically. Further, you may see the rpm climb a second (or third) time and drop back to the engagement rpm before it stays fully locked up. This engagement/slipping/rebound/chatter is generally not desirable.
 
If your clutch does not slip, then one or the other or both rear tires must slip, or the engine must get lugged down absorbing power in excess of what is needed for maximum slip ratio at your LR tire.

_________________

If your clutch cannot hold the power of your engine and burns up, it's only because you could not slip your tires.

If it can then you can make a trade off between the amount you lug the engine down and slipping your tires.

Peak torque is just a definition of when your engine is putting out maximum turning power.

If you have a clutch able to lock up when the engine is putting out maximum power, then your able to use maximum power to go forward, putting any power your not able to use into winding up your rear tires to the point of slipping and lugging down the engine.

It's a balancing act between wasting power lugging down the engine, heating up the clutch a little or trying to spin your tires a little, all to cause your rear tires to operate as close as possible to their maximum slip ratio. If your in a low hp situation, your not going to spin your tires on the start getting rolling. Because of that your going to either lug your engine down, slip the clutch a little or engage your engine somewhere outside of peak torque.

The endless argument is about if it's best for the initial lets get going; to engage at peak torque with a solidly locked up clutch and tires which do not spin, lugging the engine down; or to either slip the clutch a little or solidly engage the engine somewhere other then at peak torque. If you do not have the hp to spin the rear tires, then it's always going to be a trade off between lugging the engine or not using the engine at it's best output, and slipping the clutch.

I think most will recommend throwing a little heat into the clutch to start bringing in additional acceleration and then lock up after the start of acceleration. You can be either already rolling when acceleration occurs or you can be stopped when acceleration occurs.

If I bring in now the first paragraph I wrote, even on a rolling start you will want to be on your LR tire and have the RR tire either slipping or ready to slip at the slightest acceleration. That will allow you to start your acceleration on your low gear smaller LR tire. If not, then all possible problems are magnified, because your going to be starting in high gear. If you can't slip either rear tire or wind up the RR a little more then the LR, when you start your acceleration, it's back to square one with the only things you can do being lug the engine or slip the clutch.
 
I don't have a mychron.. I just have a cheap o that shows rpm and max rpm... so whats causing the jerk? just slip then lock up?
 
You might try something I found many years ago. I had the same problem one day with my two cycle 101 McCullough. I started opening the low speed needle, and the more I opened it, the less the rpm drop. (Very small adjustments) I kept doing that until the rpm drop went away completely. I set fast time that day and won the race. One of the guys I beat won the nationals that year.

Now I wasn't running a dry clutch, it was an oil bath clutch, but it was a centrifugal clutch. Hartman I think. This was before the disk clutches came out. 1975 I think. God!! Has it been that long. And I remember it like it was yesterday.
 
ok so im going to be making test hits most of the day trying to get this right... so youll see me posting findings questions and settings most of the day... heres my first question... a max torque clutch with black spring is what I was used to... loved it but it had a lil more slip off the corner then my liking... so the max torque would be witch of these settings? 1-rapped engagement low inertia 2-moderit rapped engagement average to low inertia 3-smooth gradual engagement and high inertia starts 4-verry smooth gradual engagement high inertia? im guessing it would be #4? so im going to start with #3 on the heavy shoes and red springs and see what that does? youll prob hear back from me in an hour or so with my findings... lol
 
so I got a test hit in and it felt better... but my idle was too low... when I came up to a good idle the kart started to leave with out me... lol and the engine and the clutch didn't seem quite connected... think I need the #2 setting listed above with the white spring... that should get the 2 connected and have enough leeway for a good idle...hope that jerk doesn't come back? if not then I think that "should" be the setting for this motor..
 
In a nut shell, if you make it not hit hard. you have to make it slip and slip makes heat.

If you can make either work, use the heaviest weight and the strongest springs.
 
Tim how you set up those clutches also is determined by how fast you are rolling when the race starts, at your track. Some tracks have the karts very slowly rolling until the start line then the race begins, while other tracks have them rolling a little faster by letting the pole holder set the pace. Setup #4 would be for when your rolling a little faster on the starts and dont have to lug the engine much. #1 is more for when your taking off or starting from a very slow start or almost a standing start, see what im saying? #3 would most likely be where you need to be and is where we ran ours at with the heavy shoes. With light shoes, i used #2
 
Here's what always work for me. Set the clutch so that it engages at peak torque!! Tune the carburetor so that the clutch doesn't suddenly lockup and the engine loses RPM. The point of clutch engagement should almost not be felt. There should be a very smooth transition from slipping to not slipping. If you feel a very distinctive lockup, and the rpm's drop substantially, you're probably too lean on the low speed.

I'm not one hundred percent sure with a four cycle, but that is exactly what my two cycles did.
 
im working with a bunch of un known stuff here... 1 the motor has never been on a dyno... from testing my max torque is in between 3000 and 4000 rpm... my max torque had a lock up of 3200ish... and was too low... and 4500 was too high and burnt the shoes last time... so im shooting for a lock up around 3500 to 4000... im on the right track... I just have to keep testing... the starts aren't my worries running a sprint course is the low rpm off corner that's the killer... when I make a test hit its almost like a drag run... I make 1 hit from idle... and 1 hit from just under lock up...
 
i got that last test hit in with the #2 setting and white springs... felt good next to no heat out of the clutch not a real high rpm jump and min bog... I think that's the set up tell I can get to the track... if the bog/chain jerk is bad ill have to go to the #3 setting and white springs... but I think that'll do... thanks for the help guys
 
You're trying to get the Noram to work like a disk clutch where is slips in the tight turns. I wish you luck but, these clutches wern't made for that. They can slip at top end if you're running light shoes and springs. I set mine to lock about 2000 and be direct drive everywhere on track and the shoes still burn from the parade lap @375.
 
My local track has mandated the noram for a long time. You don't want to use the light shoes in anything as some have already mentioned before. You also want the smoothest setting possible. If I remember right, purple springs should get you the correct engagement. I know we used white springs for restricted engines.

If you have a choice I wouldn't run the noram at all. The premier stinger or Hilliard flame are much nicer
 
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