Wheel flex
- Thread starter BlewBYu
- Start date
BlewBYu said:
I had a similar question a day or two ago. I am trying out 1.4g wheels and felt they could possibly distort while mounted in the traditional fashion. John noted they are fine to run in the standard or reverse mount, but of course 1.1g wheels would have a better chance of flexing. I'm sure others will respond who have run 1.1 wheels or lighter, but I'm not certain there is an exact cut-off of flex or no flex.
My thinking is a car with 2.25 oz riding on each rear wheel might very well flex a 1g wheel running down a Best Track. Another car with 2 oz riding on 1g rear wheels running down a Freedom Track may be just fine. I don't think there is a definitive quantifying answer.
Another thought , might there be some benefit to a modest amount of flex in a wheel.Perhaps acting as a shock absorber through the bottom of transition curve, and releasing flex ( stored energy) through the flat. It might be possible to have less overall steering and quicker times with a very small amount of wheel flex. I would love to see a controlled test done with a high speed video showing varying amounts of wheel flex and its ultimate consequences or rewards.
Momentum-
It should vary with WHERE the weight is removed, but from my understanding, the Dynasty Nitro wheels John sells at 1.4g should be fine, but the Nitro Mid America wheels, at 1.2g have a little too much flex to be run in back where the weight rests on them. Knowing what I know now, I would just get the regular Nitros and not the Mid Americas. One of my scouts had a Mid America wheel break at the pack race.
Guys, it says on Derby Dad's site that the Nitro Mid America cut wheels are ok to run conventional or reversed at 1.1-1.3g.
...Another thought , might there be some benefit to a modest amount of flex in a wheel.Perhaps acting as a shock absorber through the bottom of transition curve, and releasing flex ( stored energy) through the flat. It might be possible to have less overall steering and quicker times with a very small amount of wheel flex. I would love to see a controlled test done with a high speed video showing varying amounts of wheel flex and its ultimate consequences or rewards.
The best this magic process could do would be no net effect- all the "stored energy" of the flex comes from somewhere, and at best you only can get 100% of it back. But if you think about it- try dropping a ball off a smooth surface, it can store energy as it compresses, and then release energy as it bounces back- but it never gets back to 100% of the height you drop it from. Where does the lost energy go? Heat- noise. Same with a flexing wheel. flex will lose energy. Car will be slower than a wheel of equal weight and moment of inertia that does not flex. Hard to say if a wheel so light it flexes will still beat a heavier wheel with no flex. I think as long as flex does not permanently deform wheel- lighter still wins.
The best this magic process could do would be no net effect- all the "stored energy" of the flex comes from somewhere, and at best you only can get 100% of it back. But if you think about it- try dropping a ball off a smooth surface, it can store energy as it compresses, and then release energy as it bounces back- but it never gets back to 100% of the height you drop it from. Where does the lost energy go? Heat- noise. Same with a flexing wheel. flex will lose energy. Car will be slower than a wheel of equal weight and moment of inertia that does not flex. Hard to say if a wheel so light it flexes will still beat a heavier wheel with no flex. I think as long as flex does not permanently deform wheel- lighter still wins.
Hey guys, just to add on, the car that my daughter raced in the 2 videos I posted had 1 gram wheels that did have alot of flex to them, the girl scout race ran fine and I ran the boy scout race I actually ran the wheels with 5.5 oz of weight and moved all my plates to the back of the car and we made it through the race without issues.
Not saying that it is a good idea, but it can be done
Not saying that it is a good idea, but it can be done
txchemist said:
Hi Tx....I agree we are dealing with a finite number that at best will achieve a 100% return. However, I'm theorizing it could factor into the cars performance as to when the loss occurs, and when the stored energy actually gets reapplied. It could be possible that even with a return of perhaps 98-99%, the car could be faster due to when the stored energy is ultimately applied, thus allowing something like less steer, ultimately netting in overall performance gains.
On a track that is sloped from start to finish it would have no effect, on a Freedom track it could have a very minimal effect, and on something like a Best track it would be the most pronounced.
The MOI of the wheels is only part of the equation, MOI doesn't factor in a car running straight down the track. A small block 350 with a tuned suspension will outrun a big block 454 that cant get its power straight down the track. When you think about it it's very similar to rail running.Rail running goes against conventional wisdom as it actually induces friction into the equation, but the net result is positive.
The ultimate question is, could a car that loses 1%-2% of its potential energy to its "suspension", actually be quicker due to it possibly running smoother and requiring less overall steer ? This of course assumes the loss would be a product of dampening forces on the car through the transition curve, and the possibility of less steer being required .
TRE said:
TRE, did you keep the steer the same between the lighter "flex" wheels and more rigid wheels?
Ouch- so many problems- let's start with the first
It could be possible that even with a return of perhaps 98-99%, the car could be faster due to when the stored energy is ultimately applied, thus allowing something like less steer, ultimately netting in overall performance gains.
sorry- this is a type of magical thinking. Take away the magic of needing less steer ( we will get into that later) and just imagine a car loses 2% of it's energy when the wheel flexes right at the max force in the curve. Now if that car can roll all the way up to the last foot of track, and then get all that 2% back- it's overall time is slow all the time the wheel is flexed so when do we wish the wheel stopped flexing and gave back the energy? the correct answer is as soon as possible so we get back to max speed for the longest time. So now we do not need magic, just a bit of work to see if a flexing wheel needs less steer.- but it needs less steer for a few nano seconds at one little spot, all the rest of the time- we need our steer. If you watch many videos you might see more than a few cars make it all the way to within a few feet of the finish and start wiggling.
One could conclude the car had good steer at high speeds, but needed more steer when it slowed near the finish. Now you imagine a car that just lost 2% of it's speed needs less steer?
It could be possible that even with a return of perhaps 98-99%, the car could be faster due to when the stored energy is ultimately applied, thus allowing something like less steer, ultimately netting in overall performance gains.
sorry- this is a type of magical thinking. Take away the magic of needing less steer ( we will get into that later) and just imagine a car loses 2% of it's energy when the wheel flexes right at the max force in the curve. Now if that car can roll all the way up to the last foot of track, and then get all that 2% back- it's overall time is slow all the time the wheel is flexed so when do we wish the wheel stopped flexing and gave back the energy? the correct answer is as soon as possible so we get back to max speed for the longest time. So now we do not need magic, just a bit of work to see if a flexing wheel needs less steer.- but it needs less steer for a few nano seconds at one little spot, all the rest of the time- we need our steer. If you watch many videos you might see more than a few cars make it all the way to within a few feet of the finish and start wiggling.
One could conclude the car had good steer at high speeds, but needed more steer when it slowed near the finish. Now you imagine a car that just lost 2% of it's speed needs less steer?
txchemist said:
Honestly there is nothing magical about my premise, or the physics applied to it. It's not a zero sum calculation of the wheel flexing and un-flexing, or at what exact point this all takes place. It's a question of if it's possible the net result of this phenomenon results in faster times ? Can the small loss of energy expelled during compression be positively offset by the car running smoother.
I have seen many videos of cars getting loose near the end of the track.However, your conclusion of the cars initial steer completely misses the point. If car A with rigid wheels requires 4" of steer to keep it straight 90% of the way down the track, Car B with flex wheels may only require 3" of initial steer to keep it straight 90% of the way down the track.... is the 1" less steer and and lower frictional losses enough to compensate for a 1-2% loss in initial energy, I have no idea.
Now again this is just a theory, I have no knowledge of a flex wheel car needing more or less steer. It is however a valid premise that can be proved or discredited with a modicum of empirical data. Have you any to offer along with your conclusions?
I got a track a timer and all i know is the thinner flexible wheels are slower..thats the bottom line
TRE said:
They are slower than when running reversed, correct? They still are faster than the 2g wheels...
Okay, Here is another question on those wheels.....
I have one car that has 1.7 gram wheels
4 3/8th wheel base with wheels pushed back in rear
front and rear fenders (no trailing fenders)....
4" in 4'
The other car has the 1.2 grams on it
5.25 wheel base
leading and trailing fenders
3" in 4'
They are both getting almost exactly the same times on a 35' best track,
Witch one would be best to run on a 42' track given the above specs?
Both are fast in 35'.
and both have more than 4oz weight added.
Any help appreciated on what car to run.
I have one car that has 1.7 gram wheels
4 3/8th wheel base with wheels pushed back in rear
front and rear fenders (no trailing fenders)....
4" in 4'
The other car has the 1.2 grams on it
5.25 wheel base
leading and trailing fenders
3" in 4'
They are both getting almost exactly the same times on a 35' best track,
Witch one would be best to run on a 42' track given the above specs?
Both are fast in 35'.
and both have more than 4oz weight added.
Any help appreciated on what car to run.
plhiatt said:
I would guess the cars are not equal at 3/4 track, one car will be gaining on the other catching it right around 35', and passing it by 42'. If they are getting identical times at 35' , I would choose the car that is behind at 32-33'
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