RPM questions
- Thread starter TylerS
- Start date
alvin l nunley
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If the clutch is holding the engine at peak torque, that torque is transferred through the chain to the axle. With peak torque at the axle, you have peak horsepower at the axle. So you want the clutch to hold the engine at peak torque coming off the corner, or on the starts. Depends on what kind of racing you're doing. I don't think there are many dirt tracks where the clutch will be slipping during a race. On the starts for sure. The more horsepower, at the axle, means a faster start.
alvin l nunley
Site Supporter
For many years I've been telling people to put a bathroom scale between the front of their kart and a strong wall. In all those years no one has ever said it doesn't work, or even if it does work for that matter. That scale will tell you at what RPM you should set the clutch. Apparently it's just too much trouble for most.
JPMKarting
Site Supporter
It's a lot of effort and a fantastic way to burn up a clutch.
When clutch manufacturers and engine builders have already done the homework for you, why waste your time?
alvin l nunley
Site Supporter
I totally understand what you're saying, but I don't agree. For all the truth in your statement, why is there always that one guy up front. I'm not saying it's just because of the clutch, what I am saying is that guy tries different stuff, probably all the time, trying to get that little bit of an edge. I have a lot of ways of doing things that are maybe different from some, most of those ideas came from testing something when I think it should be tested. I'm not right, all the time, obviously, but I learned a lot of stuff. I learned what ideas didn't work for me, but some small portion of those ideas help me go faster. That guy who's upfront most weekends, didn't get that way doing what he was told necessarily.
JPMKarting
Site Supporter
There's always that one guy up front, because he's making the right decisions at the right time, 99% of the time. That's what makes him run up front consistently.
The technology in karting has evolved to the point where we all know the components and processes to make speed. It's a matter of using the right ones at the right time.
The days of "secrets" and having edge are long gone with the progression of technology and communication.
I think I’m gonna side with Al on this one. Last years great clutch debate is a perfect example of someone going the extra mile and thinking out side the box. I can guarantee, if I didn’t make a setup on my dyno where I could test my clutch, there’d be bathroom scale duct taped to my wall..
Pete_Muller
Moderator
Testing a clutch with a bathroom scale against a wall will provide accurate comparison data at one point in the speed range: 0 mph.
Clutches are very dynamic. The coefficient of friction is constantly changing as a kart accelerates (speed delta between shoe and drum is falling) and as the clutch heats up. How the clutch pulls from a standing start is rarely important these days, as almost no races are started that way. My guess would be that timing a kart from 15mph to the point of full engagement would provide more useful data.
Clutches are very dynamic. The coefficient of friction is constantly changing as a kart accelerates (speed delta between shoe and drum is falling) and as the clutch heats up. How the clutch pulls from a standing start is rarely important these days, as almost no races are started that way. My guess would be that timing a kart from 15mph to the point of full engagement would provide more useful data.
alvin l nunley
Site Supporter
I once had a dyno, I learned a whole lot of stuff, some proving me right, some proving me wrong. It was a major expense for me. The bathroom scale, for setting your clutch stall RPM, solves one of the problems you have a dyno for.
alvin l nunley
Site Supporter
I can think of a lot of tracks were, in a turn, maybe up the hill, where the clutch is slipping in your speed is not increasing. Turn 11 Sears point, up the hill at Laguna Seca, around the Monza at Kerman. Just 3 of the places I remember offhand. Just remembered, up the hill at Willow Springs. In all 4 of those instances, your clutch is slipping and you're not gaining speed. If it's slipping at peak torque, considering the amount of time it takes to get through these difficult places, I think you'd have a distinct advantage if the clutch is slipping at peak torque.
The last time I was at a road race, we all started from a dead stop, has that changed? It takes a long time to get up to speed where the clutch is fully engaged. That period of time, if your clutch is slipping at peak torque, this has got to be an advantage.
The last time I was at a road race, we all started from a dead stop, has that changed? It takes a long time to get up to speed where the clutch is fully engaged. That period of time, if your clutch is slipping at peak torque, this has got to be an advantage.
CarlsonMotorsports
Site Supporter
I'd go one further, Pete, and suggest that many karters already have access to a great data acquisition unit called the Mychron (4 or 5.) With the My5 with GPS, you can do acceleration tests back to back just as you suggested.
We've done exactly this even with the old Digatron 6E gauges: from standing start to full lock up and watch the tach (or better yet, video tape it with the old VHS or BetaMax camera,
to see where the clutch was coming in. Somewhat akin to monitoring 60' times in drag racing.We'd also simulate rolling starts and measure time over given distance (2 cones in a parking lot.)
Today's technology just makes things so much simpler (and more accurate.)
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Thanks and God bless,Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
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Linden, IN
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bcarlson@CarlsonMotorsports.com
alvin l nunley
Site Supporter
In all the years that I was driving, there was no 4 stroke. Not on the West Coast at least.
Alvin you didnt even answer the mans question.