Associated RC12R5
11-12-2011, 12:47 PM
#3301
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...
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...
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.
11-12-2011, 01:12 PM
#3302
Tech Fanatic
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.
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.
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?
11-12-2011, 01:17 PM
#3303
Tech Fanatic
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.
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.
11-12-2011, 02:41 PM
#3305
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
11-12-2011, 05:16 PM
#3306
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
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
11-12-2011, 05:42 PM
#3307
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
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
If it ain't broke don't fix it
Oh wait that's just common sense
...lol
11-13-2011, 07:32 AM
#3308
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?
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 stated:
there is a change in rear spring loading.
regarding better drivers experience:
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?
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.
Last edited by avs; 11-13-2011 at 07:55 AM.
11-13-2011, 07:58 AM
#3309
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
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
just curious, when you shifted the pod, did you rebalance the whole car?
11-13-2011, 08:54 AM
#3310
My car is balanced.
Like i said my opinion it is a non issue. Just worry about setup and the car is awesome.
Mike
11-13-2011, 12:01 PM
#3311
Tech Fanatic
11-13-2011, 03:36 PM
#3312
Quick question guys, Do the Xceed/Enneti carbon rim tires fit this car? And are the offsets what they should be? Thanks. 
11-13-2011, 05:07 PM
#3313
#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?
11-13-2011, 05:46 PM
#3314
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.
11-13-2011, 06:42 PM
#3315
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.