The Transition

[The Iceman]

Can you guys help me through this, I'm trying to figure out the play by play of our cars through the Tranistion. For BASX/SS

1. When the weight of the car and the weight of the NDFW pushes down
2. the DFW would steer harder into the rail?
3. and lift the DFW Rear wheel up?
4. therefore would it make the rear slide toward NDFW?

Thanks

 

[LightninBoy]

Can you guys help me through this, I'm trying to figure out the play by play of our cars through the Tranistion. For BASX/SS

1. When the weight of the car and the weight of the NDFW pushes down
2. the DFW would steer harder into the rail?
3. and lift the DFW Rear wheel up?
4. therefore would it make the rear slide toward NDFW?

Thanks

I don't think 3 and 4 happens through the transition.

If you are wondering what cause instability through the transition then in my mind its caused when the front wheels have reach the flat and the back wheels are still on the transition and thus still experiencing the g forces of the transition. Between that moment and the moment the rears hit the flat is when the weight on the DFW is minimized and the weight on and behind the rear wheels is maximized. If your car is going to wheelie, this is when it will happen. During this time, the rear wheels are dominating the steering so if the rear alignment is off or if the car isn't oriented correctly, then wiggles ensue.

That's how I think of it anyways.

 

[TRE]

Thats why the drill has to be spot on

 

[GravityX]

1. When the weight of the car and the weight of the NDFW pushes down

I'm not so sure that I understand, what does the NDFW push down on? Is it not lifted and off the track surface? I don't believe at any time does it ever touch the track surface, even through the transition. If it does, this would mean the opposite rear wheel has come off the track. I just don't see this happening.

 

[Guest]

I've been under the impression that roughly a pound of force is exerted on the rear of the car at that critical moment. When running SP cars with non- reversed wheels they compress a bit and snap back to shape, zapping speed.

Also, I was taught that the moment of transition slightly alters the rear alignment causing them to "slightly toe out" while the car is being moved from one flat plane(the hill) to the level part of the track. If this actually does happen, the DFW may momentarily lose it's contact with the rail? Not sure if this theory holds water and if my memory does it justice.

 

[The Iceman]

Well the the weight of the NDFW i would think pushes downward when it hits the transition therefore canterlevering the opposite wheel upward. Throwing it out of balance??? So the less weight the NDFW the better control and the more even your rears can be???

 

[GravityX]

I know this doesn't directly relate to these pinewood cars, but it sounds like sprung and unsprung weight on race cars.

 

[GravityX]

An article I pulled from the archives of google's library. Might help explain some things??? I do realize the article talks about cars going in circles but I think some of the info could "transition" over into this topic.

 

[Guest]

I would think the force being exerted on the rear would cause the NDFW to have less chance of touching the track..

 

[B_Regal Racing]

On some of my cars, the NDFW does not even spin; it's just pressed against the body and is being used simialr to a guide pin. If mine touched, I would see a huge drop off in speed. I'm fairly certain that the NDFW will not touch if drilled 1/16" to 1/8" inch higher than the DFW, especially since the DFW has positive camber.

 

[GravityX]

I would think the force being exerted on the rear would cause the NDFW to have less chance of touching the track..

This I can believe.... The rear should have enough "counterweight" to prevent the NDFW from exerting anything great enough to have an ill-effect on the opposite rear wheel.

Where's txchemist at anyhow?

 

[LightninBoy]

Well the the weight of the NDFW i would think pushes downward when it hits the transition therefore canterlevering the opposite wheel upward. Throwing it out of balance??? So the less weight the NDFW the better control and the more even your rears can be???

I think I kinda see what you are driving at. You are thinking about the moment when the front wheels are on the transition but the rears are still on the incline.

I just did an experiment with one of my cars. I set the car on a table and started loading the front with weight (centrally located on the front area between the front wheels) to simulate G forces. At 2.8 ounces the NDFW touched the table and the dominate rear lifted.

With some crude assumptions about the car design and crude calculations, that translates to about 6.5 Gs on the front during the moment described above in order to lift the rear dominate side wheel. That seems like a lot of G forces.

 

[GravityX]

Well the the weight of the NDFW i would think pushes downward when it hits the transition therefore canterlevering the opposite wheel upward. Throwing it out of balance??? So the less weight the NDFW the better control and the more even your rears can be???

I think I kinda see what you are driving at. You are thinking about the moment when the front wheels are on the transition but the rears are still on the incline.

I just did an experiment with one of my cars. I set the car on a table and started loading the front with weight (centrally located on the front area between the front wheels) to simulate G forces. At 2.8 ounces the NDFW touched the table and the dominate rear lifted.

With some crude assumptions about the car design and crude calculations, that translates to about 6.5 Gs on the front during the moment described above in order to lift the rear dominate side wheel. That seems like a lot of G forces.

That's a lot of weight, 2.8 ounces. Another thing to consider, the down force of air riding over the car's surface. Tough to measure, but again, I don't think there is enough force here to upset the dominate rear wheel (RDW). Does it "lighten" the RDW, I'm sure to some degree that it does. But is it enough to even consider the effect? I don't know. It's hard to see because the only things that move on the car are the wheels. The forces in action on the car are like magnetic lines of force, you know they're there but you can't see them.

 

[txchemist]

Gravity is not that clever. It has a center. If that center is within the three down wheels, they all stay on the track. The curve is as if you added a bunch of weight RIGHT at the center of gravity. Yes, NDFW gets heavier, but so does DFW and so do both back wheels. The car does not change where the COG is at all. The migrating of the car back wheels into the rail with added weight is an alignment issue if it happens. Now, if you just barley have the COG within the triangle, it will be less stable and a tiny bump of dust under the light back wheel could tip it and send it into the rail, but that can happen anywhere although the most force would occur at the fastest speed- the bottom of the hill.

 

[LightninBoy]

Gravity is not that clever. It has a center. If that center is within the three down wheels, they all stay on the track. The curve is as if you added a bunch of weight RIGHT at the center of gravity. Yes, NDFW gets heavier, but so does DFW and so do both back wheels. The car does not change where the COG is at all. The migrating of the car back wheels into the rail with added weight is an alignment issue if it happens. Now, if you just barley have the COG within the triangle, it will be less stable and a tiny bump of dust under the light back wheel could tip it and send it into the rail, but that can happen anywhere although the most force would occur at the fastest speed- the bottom of the hill.

But the G-forces I'm referring to are not due to gravity. The force I'm referring to is caused by changing direction. And that force is not equally distributed when the car is just entering the transition (only the front wheels are changing direction) or when leaving the transition (only the rear end is changing direction).

 

[LightninBoy]

Gravity is not that clever.

Oh and, BTW, that's not a very nice thing to say about GravityX.

 

[Guest]

I think if the COM/ alignment is right on the money then:
The rears take a bunch of G's and the DFW wants to almost lift off the track.
The guide rail acts almost like a handrail at that moment to keep the front end down. This is the way to get the maximum potential energey.

 

[txchemist]

I of course was not referring to GravityX, He is clever- and fast.
I understand the idea, but if both wheels, the NDFW and the DFW go through the same direction change, they both get equally more heavy at the same time. You can not get the wheel in the air to magically get heavier without the wheel on the track also getting heavier. Now for this instant, it only can take place when the front of the car enters the curve, but it is not deflected much before the back of the car starts to go through the same change in direction, then the car is on a circular section and the change in direction is equal for everywhere on the car until it ends the curve with the nose getting light again slightly faster than the rear. By the time the big increased force due to change in direction is taking place, the entire car is changing direction. We are not entering a black hole where the nose gets to warp out before the rest of the car can go through it. Let's imagine that is is a big deal, and your COG first moves forward a bit to the top off the arrow, and then back the other way to the bottom of the arrow, and then goes back to X

Now in the orange set up, we lose car stability due to the back right wheel lifting and car can wiggle because COG goes past the stable triangle. In the red set up, the front wheel gets too light when we come out of the curve because we get the COG too far back for a moment and we lose steering and wiggle. The just right black set up is the most stable, but do we not find set up black when we move that last bit of tuning weight around??

 

[LightninBoy]

Yep, we are thinking the same way now. I agree these moments in time are fleeting and are not equivalent to an event horizon. ;-)

 

[Guest]

I of course was not referring to GravityX, He is clever- and fast.
I understand the idea, but if both wheels, the NDFW and the DFW go through the same direction change, they both get equally more heavy at the same time. You can not get the wheel in the air to magically get heavier without the wheel on the track also getting heavier. Now for this instant, it only can take place when the front of the car enters the curve, but it is not deflected much before the back of the car starts to go through the same change in direction, then the car is on a circular section and the change in direction is equal for everywhere on the car until it ends the curve with the nose getting light again slightly faster than the rear. By the time the big increased force due to change in direction is taking place, the entire car is changing direction. We are not entering a black hole where the nose gets to warp out before the rest of the car can go through it. Let's imagine that is is a big deal, and your COG first moves forward a bit to the top off the arrow, and then back the other way to the bottom of the arrow, and then goes back to X

Now in the orange set up, we lose car stability due to the back right wheel lifting and car can wiggle because COG goes past the stable triangle. In the red set up, the front wheel gets too light when we come out of the curve because we get the COG too far back for a moment and we lose steering and wiggle. The just right black set up is the most stable, but do we not find set up black when we move that last bit of tuning weight around??

Oh man!
Thanks TX Chemist,
That explains the lift up front very precisely.