- This topic has 100 replies, 28 voices, and was last updated 19 years, 1 month ago by
.
- Posts
Pretty much a ditto on everything Richie just said! :cheers:
Richie – Front brakes are considerably more expensive than an extra rear brake because you’re buying two extra calipers/rotors, plus new uprights, spindles, and a bit more for brake line. I’ve looked at the upgrade cost for fronts before – over $1000, all told. At that point, it’s probably easier to go sell your frame and buy a shifter frame in the same or better shape.
I pretty much agree with everything else, except that bicycle racing is waaay cheaper (except for maybe the road rash expenses).
What do the enduro guys do? I thought they had redundant systems on the rear in some classes.
There’s certainly an opportunity here for smart engineers (like those Shockwave guys) to come up with a safer rear system for the sumo class. I know that we’re diameter-limited, but there’s a ton of brake technology out there for bikes, cars, and trucks, and I don’t think we’ve used 20% of it yet.
And I certainly hope that some manufacturers are paying attention to this discussion.
Oh, and Greg – While you’re out there doing an excellent job of gathering actual data, don’t forget to factor in the extra weight for Masters. Less brake fade over 20 laps could be more advantageous than any individual lap time.
If you want to set up a statistical “design of experiments” plan, just let me know – there are a few Six Sigma savvy engineers/karters that would love to help out.
Kurt,
You thinking of running Tag?
Garrik, I am an EE with a lot of mechanical and aerodynamic experience. While the primarly relation is linear, karts have high drag aerodynamically. I don’t have the front plate drag figures but I’ve heard that the drag is higher than that of a motorcycle and a lot higher than a bicycle. When you look at all the stuff hanging off a kart it is pretty understandable. Now consider that even a bicyclist exerts a large percentage of energy 70-80 to overcome aerodynamic drag above 20 mph and the aerodymaice factors start taking priority. (which is why all the Tour De France riders spend so much time in wind tunnerls) We are almost never going below 20 mph. That increases required force as a squared term. Regardless of the math, weight has a huge factor on acceleration.
With dual rear brakes the heat dissipation should be similar to current systems because the heat dissipated is related to the braking force required. Given two rotors that would halve the force and heat for each brake and would provide greater surface area to dissipate the heat. I would think you could use thinner, lighter rotors as a result, keeping the rotating mass about the same. If you are not going to bolt your middle bearing cassette down then I guess you’d have a problem.
But what I don’t understand is, if you loosen up the middle cassette, why use it at all?
Sorry double post
Many take the middle cassette out of the Tag to free up the chassis, this would not happen on a shifter ever.
Just a note to some of the new guys, if you do get your rotor real hot, please check for small hairline cracks, if you find these replace the rotor. A hot rotor coming apart can seriously injure you or your driver. It is something you may not think to look for. Ask any of the big team guy’s like Barry, Jim, JB, Brad, Tim, Stacey, AJ or whoever. Most of those has seen the aftermath of a rotor explosion. It’s not pretty!
I am not an engineer but have been racing since an early age and am not qualified to engage in a technical battle here but do feel qualified to engage my skills competing on the track with any of you. Thinner rotors don’t seem to be a realistic answer. It’s hard for me to belive a motorcycle has less drag than a kart or less parasite drag for that matter. But again, not the engineer. My opinions are from racing experience and my mind can be changed if proven there is a better way.
If Roman is kicking a$$ with front brakes, I’ll take them off. If he is still kicking a$$, I’m putting them back on for safety reasons. He is still growing and I have little reason to believe our challenges with heat are going to go away.
Lets just race!
Rick
Rick – Nope, still planning on running a shifter, just a few club races. I still have a Leopard sitting around, though, so you never know.
Mostly I’m just playing engineeer. There’s got to be a fairly simple solution to this one. Pads that last 10 laps and exploding rotors is unacceptable. I like the dual-rear idea (both on the left side) but haven’t looked at the clearance issues, or things like axle key location and whether you can make an extended caliper mount that’s stiff enough.
Kurt Freiburg Posted:
Mostly I’m just playing engineeer. There’s got to be a fairly simple solution to this one.Thank God you came along when you did Kurt! Some of the people I know in the karting biz really don’t have a simple solution for the “Sumo” guy brakes. Would be nice to use your background on this.
I like the dual-rear idea (both on the left side haven’t looked at the clearance issues, or things like axle key location and whether you can make an extended caliper mount that’s stiff enough.
I’m sure the axles could be machined and drilled, (that wouldn’t affect the integrity of the axle would it?) we primarily only use 3-4 axles in the Tag. Machining those wouldn’t be too bad. The caliper bracket would be tricky as it would have to mount on the cassette bracket, clear the outboard caliper and not flex it enough to bind brake pad to caliper alignment. That would not twist the cassette bracket with the additional leverage would it?I’m also curious about heat build up on that side of the axle / bearing. And the heat between the two calipers. Maybe some kind of safe heat shield? Another by product would be heat on the back of the seat on the left side. The brakes are hot enough at The Track that Romans seat gets hot, he can handle it but it is definitely very hot, even through is driving suit. Two calipers are only going to build and retain the same heat as one?
We can certainly use your Six Sigma Savvy (try that 10 times fast) to help solve the heavy guys on rear brake only issues Kurt. Any help is appreciated.
Thanks in advance,
Rick
I vote to stop beating this dead horse…..
Mikey
P.S. In the end, the best DRIVERS will still win!!!!!!!!!
@jj wrote:
Garri(c)k, I am an EE with a lot of mechanical and aerodynamic experience. While the primarly relation is linear, karts have high drag aerodynamically… Regardless of the math, weight has a huge factor on acceleration.
… And I’m a PE Mechanical who did terribly in the one Circuits class I had to take. 😳
What you said originally was, “Acceleration is related to the square of the weight.” I still contend that statement justifies the :bs: flag. Now I think you’re trying to equate increased weight with increased aero drag. That’s not unreasonable. However, even if you assume a heavier driver has more frontal area (which might not be true when comparing a squat, compact driver with a tall, lanky one), the effect of weight is nowhere close to a second-order function. Drag is proportional to frontal area (to the first power), and frontal area does not increase with the square of volume (in the case of an upright cylinder, doubling weight or volume by making the cylinder “fatter” increases frontal area by 41%).
OK, I’ll hop off the soapbox now (and the sound of my club hitting the dead horse ceases). In the end, when you consider ALL of the effects of decreased mass: Increased acceleration, decreased tire loading, decreased polar moment of intertia (possibly), improved transient response, less heat generated by the brakes for a given speed change, etc., etc., the reason for designating a minimum weight is clear. But it’s about much, much more than simply straight-line acceleration.
OK so the first order is linear. My lapse was in doing a direct translation of airplane weight with respect to take of distance and correlating that to karting. 😳 apples to oranges. Regardless, front plate drag, and the uncovered, open wheels are significant, especially combined with radiators that are shaped like air brakes.
Simple way to work this out is to find a Real long straight and step on the gas. Then do the same thing carrying an extra twenty pounds. Readout from the mychron will tell you the real story. Do the same thing on a dyno and you have the wind drag factor nailed.
But lighter means much faster due to a number of factors.
@jj wrote:
especially combined with radiators that are shaped like air brakes.
No wonder our kart pulls to the left!
Correct m if I am wrong but wouldn’t putting a second rotor on the axle then change the center flex of the axle. Thus making people buy softer or different rebounding axles?
Doug, step in here if you would. You are the expert on chassis setup and axles. Would you agree or disagree?
I am just saying that everything you do to change the kart is going to cost you money. If you do not carry 3 or 4 different axles and change them as the track changes throughout the weekend then you are not doing everything to get the maximum out of your chassis.
There is a reason that shifters run front brakes. Safety. I have been in a shifter a few times that either the fronts or rears fail. You can not stop. ASK AJ Noud about rear brake failure at a test in California (Moran). He hit turn one at over 85 miles an hour, flipped over the fence, and landed on the hay bails. NOT PRETTY.
Now with that said about shifters, I see horse power increases every year on TAG engines. Brad, would you agree that the power of 2007 tags are better then 1997 engines?
Then, look at the weight ran 10 years ago compared to now. Karting has evolved into a sport that is attracting an older crowd of drivers. With age sometimes comes more weight. God knows I am a bit heavier then I was at 16 years old. At 16 I was 4’10 and wrestled the 98 # weight class. I eat more then 98# in a day now.
I am not an engineer. In fact, I am not educated. I was kicked out of the school district before I could graduate. But I do know that more power + more weight = more inertia. (SP?)
I also know that you will never make everyone happy. Every decision that is made will make some happy and piss off others. This is motorsports. If you think front brakes will make you faster then pony up and buy them. In fact, we used to take the fronts off of some of our 125 chassis for heavier tag guys. I have about 15 complete sets sitting in a box. I would be willing to sell complete sets cheap cheap. This will help anyone that thinks they will go faster with them.
The point has been said over and over here. If you are fast without front brakes you will be fast with them. If you ran up front last year you will be in the same boat this year. If you were a back marker last year, you should be testing and getting driver and chassis together and improve this year and not worry about adding things to your kart to go faster.
I have a test for you. Go out and run 25 laps straight. If you can do these laps as hard as you can and your times are within 1 to 1.5 tenths of each other from start to finish, then you are ready to worry about more engine, front brakes, nitrous, studded snow tires, blinker fluid, whatever. But, if you can not consistently run within a tenth EVERY LAP, work on your kart and driving then get back on here and protest front brakes.
I hope this comes off the way I am hoping. I am not trying to stir up anything rather point out that there are more ways of getting faster without spending more money at this point. I promise you, every karter in the world, Kyle Ray, Alan Rudolph, Greg Welch, David Fore, etc etc will be faster this year then they were last. Because they test, make changes, and perfect their skills. This is what makes champions. Not more HP or front brakes.
Gotta go make money now so I can buy new front brakes for the year.
RB
- You must be logged in to reply to this topic.