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Post by Quillen Racing on Apr 25, 2007 18:53:06 GMT -7
We just got done with our dis. and council race. One thing winning cars always seem to have was the fastest starts. What are some thing's I can do to have better starts? We can not run lighten wheels.
In our infinite wisdom, I think sometimes we tend to overlook the simple solution, and over analyze things. There has been some great discussion on this point, and I think most opinions have some validity.
However, we have possibly overlooked some simple answers to the original question.
I have yet to see a question on whether he was running a 3x4, or a 4x4. Running 3 wheels down is a definite 25% reduction in the overall moment of inertia vs 4 wheels down. Simply put, the car will get off the peg faster. (not that I'm trying to start another debate)
Another answer might be, that the faster cars he was referring to, got through inspection with lightened wheels... but, we all know that doesn't happen, right? 
Well, there is my 2 cents... ;D ;D |
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Post by F.A.S.T Racing on Apr 25, 2007 19:02:31 GMT -7
If this is true though, why are "H-tread" wheels supposedly faster than stock, and the claims are "less surface contact" when the same theory should be true.... the outer H-treads are supporting the extra weight and really dont reduce friction? Thanks RC (Changed my sig to something more important than a Mustang) Well a couple things come to mind.... H or V shaped wheels almost always weigh less, so they have a lower Moment of Inertia . Plus they are normally made with a lathe,so they are very round & true. Second don't confuse Rolling Friction with Journal Friction both are very important but different. RC, you picked one of my favorite verses. Excellent choice !! |
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Post by 94 GT Laser RC on Apr 26, 2007 7:19:26 GMT -7
Well a couple things come to mind.... H or V shaped wheels almost always weigh less, so they have a lower Moment of Inertia . Plus they are normally made with a lathe,so they are very round & true. Second don't confuse Rolling Friction with Journal Friction both are very important but different. RC, you picked one of my favorite verses. Excellent choice !! Above Data Makes sense!! (I was "re-reminded" of that verse Wed night at Bible Study, then I realized HOW TRUE!!Thanks RC |
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Post by Young Guns on Apr 26, 2007 22:49:42 GMT -7
All cars had to run 4x4 on 32' wood tracks. About 10 to 15 different tracks are set up in the mall for your dis race. Some tracks are not in the best shape. For the most part they are not into to bad of condition.
Being on a smaller track would the start be more important then the flat? Cars did not have the time to pass before the finish line. They closed the gap but did not pass. I was thinking this is a weight placement issue not wheels and axles.
Thanks
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Post by 94 GT Laser RC on Apr 27, 2007 3:32:57 GMT -7
All cars had to run 4x4 on 32' wood tracks. About 10 to 15 different tracks are set up in the mall for your dis race. Some tracks are not in the best shape. For the most part they are not into to bad of condition.
Being on a smaller track would the start be more important then the flat? Cars did not have the time to pass before the finish line. They closed the gap but did not pass. I was thinking this is a weight placement issue not wheels and axles. Bold Statement: Our local races used to be on a 48' track...cars that were not built with good alignemnt were passing each other back and forth on the last 8' panel. As the cars slowed, the poor alignment was evident. The shorter 32' regional track did not reveal the problems in ALL the cars. I did notice on the 32 ' track that in almost ALL cases, the car that came through the curve in the lead finished first...very rarely did they "fall back" As far as your 4x4 rule...I have never yet seen it where they actually inspect the cars on the track to make sure they ALL touch. There could be a mm separation on one front tire which is not noticeable unless the cars are actually being "inspected" Then again, one could always apply light pressure to make the wheel appear as though it is touching. THanks RC Thanks |
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mrdeb
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Post by mrdeb on Apr 27, 2007 4:35:43 GMT -7
If groved axles cause more weight at the contact point thus causing more friction then why does running 3 wheels not cause more friction like 25% more seeing how 5oz is distributed on 3 wheels instead of 4?
3G's of force? how did you determine this as I am curious??
would'nt the force be different depending on track design?
this friction thing also brings to mind - bearings. Lets see 5 little balls of steel supporting at a miscule point on each ball. less contact area = more friction??
I think we are missing something here concerning contact area vers friction.
yea lets call Myth Busters.
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Post by King Of Hearts on Apr 27, 2007 6:49:05 GMT -7
If groved axles cause more weight at the contact point thus causing more friction then why does running 3 wheels not cause more friction like 25% more seeing how 5oz is distributed on 3 wheels instead of 4? 3G's of force? how did you determine this as I am curious?? would'nt the force be different depending on track design? this friction thing also brings to mind - bearings. Lets see 5 little balls of steel supporting at a miscule point on each ball. less contact area = more friction?? I think we are missing something here concerning contact area vers friction. yea lets call Myth Busters. No need to call myth busters,we just need to look at the physics involved and open our minds a little to what is actually taking place not what we believe.As Joker and Fast have noted the physics of the matter is all that really matter,once you have an understanding of what the science is telling you than you can try to figure out why. There are many people involved in this hobby with the engineering and science backgrounds that are necessary to explain with equations, why certain things we observe in these Little wooden wonders take place.I have found that the more I understand the science behind these things the easier it becomes to come up with new ideas to try and exploit one of the many variables in an attempt to go faster.All one has to do is spend some time reading some of the work of the scientist and engineers that have taken the time to run test in a controlled fashion to come up with results that prove or disprove what we believe to be true.Just my .02. KOH |
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Post by JOKER on Apr 27, 2007 11:03:00 GMT -7
If groved axles cause more weight at the contact point thus causing more friction then why does running 3 wheels not cause more friction like 25% more seeing how 5oz is distributed on 3 wheels instead of 4? This friction thing also brings to mind - bearings. Lets see 5 little balls of steel supporting at a miscule point on each ball. less contact area = more friction?? I think we are missing something here concerning contact area vers friction. - 3 wheels take less energy to move than 4 wheels
- It is not more friction - It is the same
- The force of friction is independent of surface area
- Static and kinetic friction are independent of the area in contact. However, the part of rolling friction that is caused by adhesive forces is very dependent on the area of the surfaces in contact. (mod-wheel vs. stock wheel)
- The friction between the wheel and axle is not rolling friction. It is sliding friction. When the car rolls down the track, the tread surface experiences primarily rolling friction. At the same time, the lower part of the inner bore is sliding against the bottom of the axle. The hub may also be sliding against the car body or the end of the axle.
- Here is the deal boys.........The fastest cars at PDDR are using both grooved & ungrooved axles. Proving it on the track & winning is the best way to prove a point. Experiment with your own personal car set-up & see what works best for you.
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Post by Quillen Racing on Apr 27, 2007 16:45:31 GMT -7
Gees guys... Hey Emerson, Leo, RailHugger, A-line, are you guys Physicists, Scientists, or Mechanical Engineers? Just curious?  ;D |
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Post by 94 GT Laser RC on Apr 27, 2007 16:45:59 GMT -7
If groved axles cause more weight at the contact point thus causing more friction then why does running 3 wheels not cause more friction like 25% more seeing how 5oz is distributed on 3 wheels instead of 4? This friction thing also brings to mind - bearings. Lets see 5 little balls of steel supporting at a miscule point on each ball. less contact area = more friction?? I think we are missing something here concerning contact area vers friction. - 3 wheels take less energy to move than 4 wheels
- It is not more friction - It is the same
- The force of friction is independent of surface area
- Static and kinetic friction are independent of the area in contact. However, the part of rolling friction that is caused by adhesive forces is very dependent on the area of the surfaces in contact. (mod-wheel vs. stock wheel)
- The friction between the wheel and axle is not rolling friction. It is sliding friction. When the car rolls down the the track, the tread surface experiences primarily rolling friction. At the same time, the lower part of the inner bore is sliding against the bottom of the axle. The hub may also be sliding against the car body or the end of the axle.
- Here is the deal boys.........The fastest cars at PDDR are using both grooved & ungrooved axles. Proving it on the track & winning is the best way to prove a point. Experiment with your own personal car set-up & see what works best for you.
 Great Write up!! Clears up a few things. I know for sure when I have a nicely prepped grooved axle, it seems to me that I only need to "nudge" the wheel a bit for some smooth spinning, but like you said, the TRUE results are seen on the Wizard! |
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Post by F.A.S.T Racing on Apr 27, 2007 18:21:40 GMT -7
If groved axles cause more weight at the contact point thus causing more friction then why does running 3 wheels not cause more friction like 25% more seeing how 5oz is distributed on 3 wheels instead of 4?
3G's of force? how did you determine this as I am curious??
would'nt the force be different depending on track design?[/size] this friction thing also brings to mind - bearings. Lets see 5 little balls of steel supporting at a miscule point on each ball. less contact area = more friction?? I think we are missing something here concerning contact area vers friction. yea lets call Myth Busters.[/quote] Now this makes my head hurt....But here goes:
An object traveling at 16 ft/s on a curved path of 4ft radius (Best Track curve)
is subject to a centripetal acceleration of v2/r=162/4=64 ft/s2.
The acceleration of gravity is 32 ft/s2 so there are 2 g's of centripetal acceleration
pushing down on the object. To this add the 1g gravitational acceleration to get a
total of 3g. A 5oz car will momentarily weigh 15oz during the curve (3 x 5oz = 15oz) Almost a pound !
Yes track design effects g-loads. A more gradual curve will have less g-loading.
"I reject your reality, and substitute my own!"[/size] Adam Savage-Mythbuster[/font] |
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Post by 94 GT Laser RC on Apr 27, 2007 18:26:21 GMT -7
Now this makes my head hurt....But here goes:
An object traveling at 16 ft/s on a curved path of 4ft radius (Best Track curve)
is subject to a centripetal acceleration of v2/r=162/4=64 ft/s2.
The acceleration of gravity is 32 ft/s2 so there are 2 g's of centripetal acceleration
pushing down on the object. To this add the 1g gravitational acceleration to get a
total of 3g. A 5oz car will momentarily weigh 15oz during the curve (3 x 5oz = 15oz) Almost a pound !
Yes track design effects g-loads. A more gradual curve will have less g-loading.
"I reject your reality, and substitute my own!" [/size] Adam Savage-Mythbuster[/font][/quote]  |
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Post by JOKER on Apr 27, 2007 18:51:51 GMT -7
Gees guys... Hey Emerson, Leo, RailHugger, A-line, are you guys Physicists, Scientists, or Mechanical Engineers? Just curious? ;D Let's see.........a structured cabling engineer, a welder, a professional cabinet maker............not sure what Leo does. |
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Post by Quillen Racing on Apr 27, 2007 19:12:50 GMT -7
Gees guys... Hey Emerson, Leo, RailHugger, A-line, are you guys Physicists, Scientists, or Mechanical Engineers? Just curious? ;D Let's see.........a structured cabling engineer, a welder, a professional cabinet maker............not sure what Leo does.
I guess there is still hope... ;D |
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;D
