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Old 11-12-2011, 12:47 PM   #3301
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Someone is going to have to explain this pod-balancing obsession to me...

The pod is a solid structure, with no joints. Whatever weight is put in it will even out across both wheels. It is connected to the chassis by a single, central point so can have no effect on the balance of the chassis.

Once the dynamics kicks in, then a severe imbalance could conceivably cause the car to unweight one wheel more than the other, but it would have to be severe. It could be countered by setting the axle slightly offset, thus sharing whatever dynamic imbalance exits across the contact patches. This clearly is not the case, since those doing the balancing do not run their axle centre-line any different to those of us who don't.

It's a concept that has apparent merit in theory, but in practice it doesn't stand up to a basic mechanical engineering analysis. Unless someone can explain it better...
first, let me say i have not estimated the relative magnitude of these effects, but the potential impacts that i see are:

1) increased binding(or friction) in the pivot links. during acceleration or braking a lateral imbalance in the pod will induce a yaw moment about the pivot, and this will load the links asymmetrically to take out that yaw moment. more load in the link means more friction in pivot ball(s)

2) increased tweak spring forces. if you set tweak on a balance beam to get equal loading on the rear wheels, the lateral imbalance must be carred by an imbalanced preload in the tweak springs.

while it is true that balancing the complete vehicle avoids an overall tweak imablance, there are still internal pivot ball and spring asymmetries created.

it would be instructive for someone with more sensitive driving skills (than me) to intentionally increase or decrease this internal imbalance and describe the results.

i suspect that the asymmetric tweak spinrg setting is less significant, but the friction might be a noticeable handling impact.
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Old 11-12-2011, 01:12 PM   #3302
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first, let me say i have not estimated the relative magnitude of these effects, but the potential impacts that i see are:

1) increased binding(or friction) in the pivot links. during acceleration or braking a lateral imbalance in the pod will induce a yaw moment about the pivot, and this will load the links asymmetrically to take out that yaw moment. more load in the link means more friction in pivot ball(s)

2) increased tweak spring forces. if you set tweak on a balance beam to get equal loading on the rear wheels, the lateral imbalance must be carred by an imbalanced preload in the tweak springs.

while it is true that balancing the complete vehicle avoids an overall tweak imablance, there are still internal pivot ball and spring asymmetries created.

it would be instructive for someone with more sensitive driving skills (than me) to intentionally increase or decrease this internal imbalance and describe the results.

i suspect that the asymmetric tweak spinrg setting is less significant, but the friction might be a noticeable handling impact.
Except that...

There can be no more friction in the pivot balls than that applied by the load of the chassis. And, as far as I am aware, you cannot exert any moment into something that has no pivot for the moment. Since there is no pivot in a single ball joint, how do you get a yaw?

Nothing connected to the springs is connected to the rear pod! The springs can only influence the level of the chassis, not the level of the pod. There is no load from the springs onto the pod, only the load of the chassis as it rolls relative to the pod.

I think we have about 30 examples of people with more sensitive driving skills than you or me - the top 30 at every international event! None of them has ever made any minor adjustment to motor position to balance the rear pod in the 30 years I've been racing. So where's the noticeable handling impact?
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Old 11-12-2011, 01:17 PM   #3303
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Aw heck. You mean I've been messed up all this time and still manage to break the track record for 1/12 17.5 open two weeks in a row.

I checked my tweak and it is right on. I checked my side to side balance since I neglected to do so after the LiPo conversion and it's 22g light on the electronics side.
Meaning no disrespect, and hoping you said that with a smile on your face, but anyone's track record would last about as long as it took Mike Blackstock, Josh Cyrul or Brian Wynn to turn up and race... with their imbalanced rear pods!!!
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Old 11-12-2011, 01:43 PM   #3304
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Meaning no disrespect, and hoping you said that with a smile on your face, but anyone's track record would last about as long as it took Mike Blackstock, Josh Cyrul or Brian Wynn to turn up and race... with their imbalanced rear pods!!!
Of course Sir, but until they do visit our humble little track the top spot shall remain mine even with my unbalanced rear pod.
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Old 11-12-2011, 02:41 PM   #3305
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Of course Sir, but until they do visit our humble little track the top spot shall remain mine even with my unbalanced rear pod.
lol...I think both you guys are saying the same thing

I mean anyone who can tell if their car is tweaked would have awareness of an imbalance but usually at track for me I'm attempting to find the spring, damping and various adjustment balance

Perfection of an 12th car can't be invalidated though just an extreme measure to have an perfect car which 12th scale drivers have been known for having if possible

I even remember people using pins to balance Jaco's but on the track again how much do these extreme measures matter

I think in general tires win races in conjunction with correct spring rate and dampning

Driving well with a a good rolling car also helps...lol
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Old 11-12-2011, 05:16 PM   #3306
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Here is what happend to me on the whole balance the pod thing.. I noticed the pod was off balance with the motor so i added 3mm worth of shims and the pod was correct. Then i went out and practiced and the car was horrible. So i took the shims out and ran the car again and she was back to good. So i am not sure it really matters and i will not be doing it in the future..

The last few races my car has been the best driving car i have had since 1s lipo's have come out.


Again this is all my opinion.

Mike Blackstock
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Old 11-12-2011, 05:42 PM   #3307
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Here is what happend to me on the whole balance the pod thing.. I noticed the pod was off balance with the motor so i added 3mm worth of shims and the pod was correct. Then i went out and practiced and the car was horrible. So i took the shims out and ran the car again and she was back to good. So i am not sure it really matters and i will not be doing it in the future..

The last few races my car has been the best driving car i have had since 1s lipo's have come out.


Again this is all my opinion.

Mike Blackstock
Ancient Chinese proverb:

If it ain't broke don't fix it

Oh wait that's just common sense ...lol
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Old 11-13-2011, 07:32 AM   #3308
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Except that...

There can be no more friction in the pivot balls than that applied by the load of the chassis. And, as far as I am aware, you cannot exert any moment into something that has no pivot for the moment. Since there is no pivot in a single ball joint, how do you get a yaw?

Nothing connected to the springs is connected to the rear pod! The springs can only influence the level of the chassis, not the level of the pod. There is no load from the springs onto the pod, only the load of the chassis as it rolls relative to the pod.

I think we have about 30 examples of people with more sensitive driving skills than you or me - the top 30 at every international event! None of them has ever made any minor adjustment to motor position to balance the rear pod in the 30 years I've been racing. So where's the noticeable handling impact?
you misunderstood both points. the imbalance acts on 2 axes, roll and yaw. (roll left to right, and yaw nose left to nose right). the yaw axis effect induces pivot friction, while the roll axis induces an asymmetry in the side spring preload.


you stated:
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Originally Posted by SlowerOne View Post
you cannot exert any moment into something that has no pivot for the moment. Since there is no pivot in a single ball joint, how do you get a yaw?
consider the vehicle under acceleration, the vehicle's total cg is at or near the centerline. if the rear pod is off center, then the main chassis is off in the opposite direction. to see this, you need to do seperate free-body's on the rear pod and main chassis.

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Originally Posted by SlowerOne View Post
Nothing connected to the springs is connected to the rear pod! The springs can only influence the level of the chassis, not the level of the pod. There is no load from the springs onto the pod, only the load of the chassis as it rolls relative to the pod.
you need to remember that if the main chassis is imbalanced (to offset the pod's supposed imbalance) then the
there is a change in rear spring loading.



regarding better drivers experience:
Quote:
Originally Posted by SlowerOne View Post
I think we have about 30 examples of people with more sensitive driving skills than you or me - the top 30 at every international event! None of them has ever made any minor adjustment to motor position to balance the rear pod in the 30 years I've been racing. So where's the noticeable handling impact?
if you re-read my earlier post, i only indicated that i suspected the roll term is less significant than the yaw term, this was not a judgement that either term was significant to car handling in general. Please note that i am not arguing how significant these effects are, but only trying to correctly describe the mechanics involved.


a second try at describing the mechanics,
the yaw term:
during accel or braking an imbalance will cause a yaw moment about the central pivot. this moment is resolved internally by the links, one in tension and the other in compression. during acceleration, the compression is shared with the central pivot, during braking the tension is shared with the central pivot.

so the imbalance creates a moment, which increases load on some of the pivot balls, and increased load means increased friction.

the roll term:
when you balance the complete car, the main chassis must be laid out to have the oppposite imbalance that the rear pod has.
so when you set the tweak, there must be an asymmetric preload on the side springs in order to get the complete vehicle to stand straight.
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Last edited by avs; 11-13-2011 at 07:55 AM.
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Old 11-13-2011, 07:58 AM   #3309
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Here is what happend to me on the whole balance the pod thing.. I noticed the pod was off balance with the motor so i added 3mm worth of shims and the pod was correct. Then i went out and practiced and the car was horrible. So i took the shims out and ran the car again and she was back to good. So i am not sure it really matters and i will not be doing it in the future..

The last few races my car has been the best driving car i have had since 1s lipo's have come out.


Again this is all my opinion.

Mike Blackstock
that is a very interesting experience. if you turn it around, one could conclude that a 3mm change in balance is significant.

just curious, when you shifted the pod, did you rebalance the whole car?
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Old 11-13-2011, 08:54 AM   #3310
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that is a very interesting experience. if you turn it around, one could conclude that a 3mm change in balance is significant.

just curious, when you shifted the pod, did you rebalance the whole car?

My car is balanced.

Like i said my opinion it is a non issue. Just worry about setup and the car is awesome.


Mike
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Old 11-13-2011, 12:01 PM   #3311
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My car is balanced.

Like i said my opinion it is a non issue. Just worry about setup and the car is awesome.


Mike
This guy wins races without any yaw problems - I think I'll "be like Mike"!!!
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Old 11-13-2011, 03:36 PM   #3312
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Quick question guys, Do the Xceed/Enneti carbon rim tires fit this car? And are the offsets what they should be? Thanks.
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Old 11-13-2011, 05:07 PM   #3313
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Default #4690 CONVERSION KIT

Any feed back on before and after results using the inline conversion kit. Did you like disslike and why. What were your setup changes?
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Old 11-13-2011, 05:46 PM   #3314
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Any feed back on before and after results using the inline conversion kit. Did you like disslike and why. What were your setup changes?
If you are asking would you notice enough of a difference to warrent spending $100 the the answer is no. Since the conversion changes where everything is located and you still need to set up the car it may be worth it. Did I notice a big improvement, no.

I did notice that it turns in a little better and exits a little better than I can remember from last year on a track that was changed from last year.
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Old 11-13-2011, 06:42 PM   #3315
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Any feed back on before and after results using the inline conversion kit. Did you like disslike and why. What were your setup changes?

The lipo upgrade is alot easier to drive and stays flatter in the corners then the reg 12r5.1.. The setup changes are we run much softer side springs then before and more front camber.
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