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Discussion Starter · #1 ·
My problem with anglewinders is symmetry. Or lack thereof....

I would have thought that cars would need to be as symetrical as possible to provide consistant handling. Therefore inlines are the clear winners in keeping the chassis completly symetrical, with sidewinders following (just the endbell and pinion & contrate which aren't on both sides), but anglewinders just aren't symetrical at all.

I'm not saying that they are not the best handling cars, but why are they?

Another problem is that the torque from the engine (when chassis is laid out with gear on the left, when looking at the chassis from the back) will constantly try to lift the front left wheel under acceleration, and the rear right wheel under braking. This is obviously not good when accelerating through a left hand bend, or braking through a right hand bend.

So do you have to drive the chassis differently through opposite corners or what?

Just wondering and wanted to provide some good technical discussion


McLaren
 

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Graham Windle
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andy you witnesed my porsche challenge car at preston before the motor blew .
the advantage of an anglewinder is that you can use smaller wheels and gears and use a longer motor in a small car also the pendulum effect of a sidewinder is reduced and the torque reaction of an inline is removed
 

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Discussion Starter · #3 ·
Yes, I saw your Porsche, but I don't think you can claim all of it's speed as a benefit of it being an anglewinder
. I'd just like to know why you didn't have the scaleauto motor in it from the start....

So that's it then?

Smaller wheels means a lower chassis - But an inline could be lower...

Pendulum effect reduced - But an inline would reduce it further...

Torque reaction reduced - But a sidewinder would remove it completly...

So really it's just a big, fat compromise.
Not the answer I was looking for, but I suppose if that's all....

McLaren

PS. Cheers for speedy reply...
 

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Al Schwartz
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I have been a fan of sidewinder (and, by extension, anglewinder) layouts since I first grafted a Pittman 703 (this was the forerunner of the 704,5,&6 motors built for slot car applications) into a Merit D type in 1959. At that time, and for many years after, in the context of a small, clasic rubber Scalextric track, cars so powered simply outran anything that I could build with an inline (usually Pittman) motor. They did not do this on speed - but the handling was so far superior that any deficit in straight line speed was easily overcome - again - in the context of the track that I was running on.

If you look at a sidewinder from the right side, you will see that the armature is rotating in a counter clockwise direction. The torque reaction i.e., the force applied to the chassis, will be in opposition to the armature rotation and will be clockwise.
This will act to force the front of the car down, not up and will oppose the reaction around the rear tires which will tend to lift the front. An in-line motor will always exert the reactive force around the longitudinal axis of the car and thus, depending on the position of the driving gear, will "lift" one side or the otherbut will provide no opposition to the lifting effect of axle torque.

In addition, I have long held the belief that there is no connection whatsoever between the physics governing the handling of a slot car and the real thing. The front of a slot car (barring, perhaps, ones fitted witha laterally swinging guide) follows a fixed locus of points and cannot slide. The rear, as we all know, can slide but lateral movement of the rear wheels cannot be countered or controlled by counter steering the front! Thus, it seems to me that the design objectives sought in real cars, centralization of mass and reduced polar moment of inertia, are the opposite of those most desirable in slot cars. Anything, of course, can be carried to extremes and a large weight hanging far aft of the rear axle can cause problems but an approach that concentrates one mass as close to the rear axle as possible for optimum downforce on the rear tires and sufficient weight near the guide to avoid the slot car equivalent of understeer, i.e. deslotting, is the most effective way to provide maximum traction with minimum mass.

Of course, current "production" slot cars typically use magnets instead of mass to achieve similar results. An interesting experiment to perform on current cars is the following: Take a current Scalextric F1 car and run laps on a (magnetic) track. Open the car and move the magnet from the as-delivered rear position to the forward one. re-run the trial and compare lap times. In my experience, the rear position is significantly faster.

I do not have a solid history of recent winning performances to lend credence to this postion but then, look who is driving!

EM
 

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Graham Windle
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QUOTE . I'd just like to know why you didn't have the scaleauto motor in it from the start.
I had tested it with both motors prior to the race and the slotit was just so much more drivable .I didnt think I needed the power of the scale auto as last year at pendle my car had similar performance and I lost out when the track got slippy . However watch this space and see what happens at pendle
 

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Discussion Starter · #6 ·
I'll be there....

Anyone ever tried a Fly Joest Porsche before?

I'll probably be running the Carrera GT, 'cos I want to be different. It's only while I learn the track, next year I'll be competing properly.... hopefully...

McLaren
 

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Senior Slot Car Mechanic
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QUOTE If you look at a sidewinder from the right side, you will see that the armature is rotating in a counter clockwise direction. The torque reaction i.e., the force applied to the chassis, will be in opposition to the armature rotation and will be clockwise.
This will act to force the front of the car down,

Sorry,not so.The motor is(er,s'posed to be anyway)solidly mounted to the chassis,and there fore any torque reaction will be absorbed/canceled out by the chassis itself.The ONLY torque that the motor could generate,would be to actually bend the chassis(probably very minute at best)in a downwards direction at the front,and would have absolutely no useful reaction that would force the nose down into the slot.I think possibly the centrifugal torque reaction might apply,but would be so weak over the length of the Lever(arm centre to guige flag pivot)as to be very small indeeed.

Whereas the lever action of the tires in relation to the torque generated by the motor,is quite huge by comparison.Ie,half the diameter of the pinion over half the diameter of the spur,as it tries to climb the spur gear.This force will be trying to lift the car out of the slot long before the other force can apply any modest presure in the opposite direction.
 

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Al Schwartz
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BWA, I will cheerfully and prudently yield the field to you on invention and machining, but not on physics.

Here is a thought experiment: Assume a motor with infinitely flexible leads. Hold the shaft fixed and apply power. the motor will rotate - in the case of the point of view noted above, in a clockwise direction. Hold the motor and the shaft rotates counterclockwise. Simply because the motor does not move relative to the chassis does not negate the force. In point of fact, there is a torque exerted by the motor case which is exactly equal to and opposite in direction to the torque exerted by the shaft. That torque acts on the front of the car. A countervailing torque is exerted by the rotation of the rear axle. The magnitude of this force can be seen in the case where the rear axle is held and the motor operated - the chassis will lift. If we consider the case of zero tire slip, the ratio of those forces can be expressed , where Tm is the motor torque in arbitrary units, Rt distance from the rear axle to the guide, Rg is the distance from the center of the motor to the guide and M is the gear ratio (and the gear set is frictionless):

T clockwise= Tm/Rg (downforce on guide)

T counterclockwise = Tm X M /Rt (lifting force on guide)

Clearly, the counterclockwise force will be greater but the clockwise force is not eliminated. Although the torque applied to the axle is multiplied by the gearing, it is also acting through a longer lever arm.

As a practical example, consider a chassis with a 3" wheelbase, 0.6" between the motor shaft and the axle and 2.6" between the motor shaft and the guide and a 3:1 gear ratio:

T clockwise = Tm/2.6

T counterclockwise = Tm X 3 / 3.2 and the net "lifting" torque is

(Tm X 3 /3.2) - (Tm/2.6) = 0.55 Tm - in effect, about a 35% reduction

In the case of an inline motor, there is no "T clockwise" term

Of course, any loss in the gearing or tire slip will reduce the "T counterclockwise" term and increase the proportional effect of the sidewinder motor.

EM
 

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Brian Ferguson
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I love it when physics and slot cars meet.... especially when there are engineer-types present!
And yes... I find it very interesting! What does that say about me?
 

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Senior Slot Car Mechanic
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OK,ya just blinded me with science.COUNTERVAILING,what the heck kind of a word is THAT.


S'cuse me for flunkin out of grade 12.

Time to get PRACTICAL.I'll try and come up with an empiracle method of proving/disproving our positions.I am always ready to be proven wrong.

I believe,and this is just from my own practical experience of the way mechanical stuff works that the difference between the two forces will be closer to the order of 100:1 than the 35% you calculate it to be.

Asumption 1 that I make,is that the forward reactive force you are talking about is purely the reaction/opposite reaction generated by the energy put through the motor.In my mind,I can only see the Arm versus can/chassis being involved in this,and not the gearset/wheels/tire/road contact.Do you concure?And,the lever measurement would be from the centre/motor shaft to the centre of the guide contact patch.

This should be able to be measured by suporting the chassis at the motor shaft(as the fulcrom of the Lever)and measuring the resultant load on the pickup when said motor is given the juice as it were.I don't think contact with the road is necessary to measure this part of your force field.

I'll stop here,and get your ideas on my ideas first before we go too much further.
 

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Senior Slot Car Mechanic
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QUOTE In the case of an inline motor, there is no "T clockwise" term

Actually,I believe you are wrong here also.The T clockwise will be trying to put the car on it's roof in a sideways barrel roll when power is aplied.

Now this effect,I can actually feel in some of my inline cars,as they slide far easier in one direction than the other,depending on which side of the pinion the crown gear is.Due to the fact that the torque loads one tire harder and unloads the opposite tire by an equal amount less gravitational effects.

The reason it has more effect in an inline situation is because the lever is much shorter.IE from the motor centre line to a point about midway on the rear tire contact patch.And is applied directly through the gear train rather than just the reactive torque generated between the motor and the guide flag in the SW setup.
 

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Al Schwartz
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QUOTE OK,ya just blinded me with science.COUNTERVAILING,what the heck kind of a word is THAT.

S'cuse me for flunkin out of grade 12.

When you grow up without televison (age, not poverty) you spend a lot of time reading!

I'm studying your comments - I think we are running into both class 1 and class 2 levers - will take some sorting out.

EM
 

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Al Schwartz
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QUOTE Actually,I believe you are wrong here also.The T clockwise will be trying to put the car on it's roof in a sideways barrel roll when power is aplied.

This is correct. I was applying the " T clockwise" term only to forces acting along the axis of the chassis to offset the "wheelie inducting" "T counterclockwise" term. What I should have said was that the torque reaction around the axis of the motor still exists but it only serves to prodcue a rotational force across the chassis and will not offset the rear axle torque.

EM
 

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I am just wondering how this net torgue changes dynamically at different amounts of motor acceleration. Am I right that one moment (torgue applied over a distance) is coming from the motor armature and two others are coming from 1) the tires and axle rotating and 2) tire traction on the track? At different amounts of acceleration the traction will shift, reducing the larger moment in the short term. Since force at the gude shoe is critical at turns, when acceleration or deceleration will be applied. I thought this might need to be considered too. Although...I think it's more of a challenge to measure.

As a newcomer to this site, just want to say how much I am enjoying it here!!

John
 

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No comment on this subject from me but welcome John, I'm glad you are on the forum and look forward to you posting some of your excellent scratchbuilding and conversions.

Back to anglewinders.

David
 

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Al Schwartz
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QUOTE At different amounts of acceleration the traction will shift, reducing the larger moment in the short term. Since force at the gude shoe is critical at turns, when acceleration or deceleration will be applied. I thought this might need to be considered too. Although...I think it's more of a challenge to measure.

Let me add my welcome as well and yes, you are quite correct, it is a dynamic situation and the theoretical explanation I proposed and the experiment that BWA suggested are essentially static "snapshots" of the process. Unfortunately, my supply of 1/32 scale strain gauges and load cells and 1/32 telemetry gear is a bit low at the moment! At the end of the day, I fear that the answer still lies in " cut, try and check the lap times"

EM
 

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The best and only effective slot racing telemetry is a race distance and what the driver thinks about the car he is driving. Most of the skill of driving these things is in the head.

It is a fact that the first anglewinder I built was considerably easier to drive quicker over a race distance that its inline predecessor of the same wheelbase. It had better traction, better acceleration, better corner entry speed and slid more progressively. It must have suited my driving style, brake late and slide the tail, as I found I was running in the top 4 at open meetings rather than the top 12.

The early examples were crude with significant assymetry, but as the back end got neater they got quicker.

Don't think too hard about it or else somebody might convince you that they can't possibly work.
 
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