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Old 06-14-2009, 03:24 AM   #121
McCardigan
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Yep got that Andy.

No wucking furries.

Any chance you can predict next weeks $40m Tatts Lotto numbers?

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Old 06-14-2009, 03:30 AM   #122
Clancy
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Quote:
Originally Posted by chris McArdle
Yep got that Andy.

No wucking furries.

Any chance you can predict next weeks $40m Tatts Lotto numbers?



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Old 06-15-2009, 01:13 AM   #123
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Ask "Getback", aka Shaun, about his sway bar on his super narrow enduro rig with lots of travel. Wouldn't have worked with out one. When are we going to start using electro-magnetically adjustable spring units like Corvette's and Cadillac's ? That would change the ball game all over again too! Glad to see this post has brought about change for the better, lets keep it going!
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Old 06-16-2009, 03:40 AM   #124
Andy-Gadget
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The influence of rider and passenger mass on the static centre of gravity.

Adding the rider to the vehicle changes the centre of gravity of the outfit.
This change is towards the added mass, the rider, and can be calculated relatively easily, but as the rider is "dynamic", that is the rider centre of gravity can be moved intentionally through the application of "body English" to assist the handling of the outfit.
This means that the calculated new CG is of limited use practically, but the rider’s knowledge of the change in CG is helpful, and the cornering dynamics of the outfit can be calculated to at least give some performance parameters for the outfit.

Having used the beam reactions system to calculate the position in three dimensions of the static CG of the outfit, there are a number of way of integrating the two CG's together, the easiest being the use of vectors, so that is what I propose to use.

Some notes on vectors first, there are two ways of representing a force, a scalar (a magnitude but NO direction) and a vector (both a magnitude AND direction).
All groups of forces acting on something can be resolved to one vector, and any single vector can be broken down into any number of separate forces, so long as all directions are known.
These vectors can be added and subtracted using simple rules.
Marine navigators use vectors constantly to find the resultant direction and speed of a vessel when acted on by a current.




If the addition of all the vectors acting on a point makes a closed loop, then there is no resultant vector and the point is stationary.

Tony Foale has looked into the solo motorcycle version of this in his book "Motorcycle Chassis design", and I will borrow some of his research and apply them to sidecars.
The first assumption I will make is where the CG of the rider is located, and this is slightly ahead of the riders lap, and just above the thighs.



To use vectors to calculate the new CG, the riders CG needs to be broken down into vertical and horizontal components, this sounds scary but is easy.

The vertical component is the difference in height between the static CG and the riders CG, so measure the riders CG from ground level and subtract from that the static CG height, if the result is positive then the riders CG is above the static CG, if negative then below the static CG.
The mass of the outfit is the sum of the three reactions from the calculations for static CG, remembering to apply the multiplier appropriate to the second-class lever proportions used.



The horizontal change in CG is on the line between the static CG and the riders CG and the distance it moves is again proportional to the difference in masses and the horizontal distance between the masses (the vertical difference has already been calculated).



The calculations so far have been for one additional mass, to add more than one mass is relatively simple.
The horizontal components for the masses can be added together to make one resultant vector that the above calculations are used with.
The horizontal components are measured from the static CG as follows.






The vertical change in static CG is calculated in a similar way, with the differences in vertical CG now being a single mass (the sum of the two masses) acting at a point along the difference in vertical height between the masses proportional to the two masses.
Here it is assumed that the sidecar passenger’s CG is lower than the rider’s CG.



The result of all this is a CG for the outfit with added masses, but as stated earlier this doesn’t take into account any “body English” involving these masses.
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Andy-Gadget screwed with this post 06-16-2009 at 02:15 PM
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Old 06-16-2009, 06:51 AM   #125
claude
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Okay so we have a center of gravity that is really influnced on a sidecar rig by driver and passnger. It (The CoG )can also be moved around by body english of the driver and passenger.
Wider track widths will create more stability as would a lower CoG.
I think all of these are pretty much 'givens'.
The thread began with info on sidecar wheel lead. I think tip ovcer lines were mentioned also.
We have writen about rigs with swingarm suspensions and it was stated that the Roll Centers on them will remain at ground level.
So with this being said what do we have to work with?
Suspensions on all wheels, rake a trail and it effects in cornering apart from just steering, front end designs (teles, leading links, center hubs), swingarm lengths, swingarm orientation on sidecar (front or rear pivot) and of course antiswaybars.
Of course there are rigs with a frame type suspensions on the sidecar and even on the rear of the bike which can open up more discussion when and if we wish to get into it.
Where do we go from here ?
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Old 06-16-2009, 11:55 AM   #126
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Utopia ?

Surely, the beauty of sidecars is the relative unique flavour of each and every rig. This lack of uniformity is part of the attraction. Whilst some degree of science and mathematics potentially offer some solutions to severe problems such as mishandling and inadequate engineering, there is much to be said for the outcomes of personal preference.

However, even if a sidecar outfit doesn't appeal to my needs, I still admire and respect the vast array of vehicles in the sidecar world. Long may it continue for it represents something that no "Volksrig" could ever satisfy.
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Old 06-16-2009, 07:31 PM   #127
Nemo DeNovo
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All this engineering is an interesting diversion for the winter days when there's no riding (and you're stuck in the house with the female nattering away about something or other), but if the road is free of ice I'd rather just get out there and tweek the rig & ride it. Seems the "seat of the pants" method satisfies the masses best. "If it feels good, do it!" If it weren't for that, the human race would have become extinct long ago....we're all to damned lazy to fuck if it didn't feel so good
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Old 06-24-2009, 04:26 AM   #128
Andy-Gadget
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Bringing it all together, after all the maths.

The goal I had in my head at the start of all this was a set of operating parameters that would describe the way a given outfit would behave, like standing ¼ mile times for an indication of the performance of a car or bike.

But before I could do this, pertinent information about the outfit, such as the location in three dimensions of the Centre of Gravity, had to be determined, hence the maths.

The Physics is needed so vectors are understood, as it all comes down to vectors in the end.

Now that we know roughly were the centre of gravity is, its height above the ground and the distance to the wheel contact triangle horizontally can be measured.
The height above the ground determines the scale of the vectors, and this scale is then applied to the horizontal component to determine how much cornering force (lateral acceleration) can be applied before the sidecar wheel will lift.



As an example, for turns towards the sidecar, if the CG was at 1 meter height, and the bike pivot point was 500mm from the CG, as the acceleration of gravity is 1 gee, the lateral acceleration of ½ a gee will cause the sidecar to lift, 1000 / 9.81 = 101.9 mm per 1 meter per second squared.



This lift is much more controllable as any acceleration / deceleration vectors are along the axis of the tyre contact patches, and so have very little affect of the stability, hence the fun of “flying the chair”.

The other lift, the back wheel in the air, pivoting on the line between the sidecar wheel and the bike front wheel, requires more lateral acceleration to achieve the lift, but when lifted, is much less stable, as the acceleration / deceleration vectors are off the line of pivot.
An example, the bike is acceleration around a turn towards the sidecar, the CG moves outside the tyre triangle and the back wheel lifts, the wheel can’t drive in the air, and so the acceleration vector disappears, this moves the CG even further outside the triangle, and generates the rapid flip some have experienced.
I have taken the distance from the CG to the sidecar to bike front wheel pivot line as the shortest distance, rather than as it actually is, being much closer to the sidecar wheel, and hence longer, as I wanted the value arrived at from the two lateral accelerations to be the worst case.
I would like the towards the sidecar turn lift point to away from the sidecar turn lift point to be a performance figure of the sidecar.
If we take the away from the sidecar lift lateral acceleration vector to be 1and the away from the sidecar lift vector to be the multiple of the first vector, this figure is a direct value of the lateral stability of the sidecar.
The above example would be something like 2.5, so the back wheel lift vector is 2.5 x 0.5 so 1.25 meters.
As the centre of gravity is moved towards the sidecar, through intelligent placement of fixed components such as extra batteries, then the figure will reduce, indicating that the sidecar wheel lift point is closer to the back wheel lift point, it is debatable as to how good an idea this is, but the rider would then know an important parameter of the cornering capability of the bike.

The simple example I have shown is to show how it all works, but is slightly more complicated in practice.
The vertical height of the CG would be divided by the value of gravity, 9.81 for we metric people, being 9.81 meters per second squared.
The metric challenged can apply whatever value they are happy with, it will all work out in the end.
The result is the scale to be applied to the horizontal, mm / meter per second squared, or whatever.
This scale is then applied to the horizontal distance to the pivot point, and the result is the lateral acceleration required to reach this point in meters per second squared, or whatever.

I find that I tend to be symmetrical in my cornering speeds, if I have compromised clearance on one side, it is applied by my mind to both sides.
I ride sidecar outfits sort of the same way, it is the sidecar wheel lift point that is determining the cornering speed in both directions, unless you are much more bold than I, which is very much possible.
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Old 07-09-2009, 12:53 PM   #129
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I couldn't remember where I had seen this but while I was looking for some R100 stuff I came across it so I figured it might fit in here pretty well where I'll hopefully remember where I put it.

http://www.rbracing-rsr.com/advchoppercalc.html
and
http://www.rbracing-rsr.com/rakeandtrail.html
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Old 09-16-2009, 09:06 AM   #130
grafikfeat
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Thumb Yeah but...

How does suspension, rider weight, sidecar weight to motorcycle weight ratio play into that math?

I see a lotta guys w/ Harleys and a velorex plastics tied on.
Clearly too light a tub for the bike.

Me? I ride within my limits.

I know jets fly. I'll even get in one to travel. I don't care how it does it... Just so it does it w/ out crashing!
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Old 09-16-2009, 05:59 PM   #131
Andy-Gadget
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Quote:
Originally Posted by grafikfeat
How does suspension, rider weight, sidecar weight to motorcycle weight ratio play into that math?

I see a lotta guys w/ Harleys and a velorex plastics tied on.
Clearly too light a tub for the bike.

Me? I ride within my limits.

I know jets fly. I'll even get in one to travel. I don't care how it does it... Just so it does it w/ out crashing!
Less weight on the side car wheel, in proportion to the total weight of the outfit.
It moves the C of G closer to the bike centre line, with the ease of flying the chair that that entails.
It also raises the C of G as well, generally not a good thing.
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An investment in knowledge always pays the best interest"
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'95 Sport 1100 Guzzi,'84 Cali 2 Guzzi, '95 Guzzi mille, '84 R65LS, '84 R100, '82 R100RS, '05 DL650, '72 Bultaco Sherpa T 350, '78 Montessa 348, "00 XR650R
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Old 09-17-2009, 07:22 AM   #132
dbarnes180
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I KNOW Nothing!

Quote:
Originally Posted by Andy-Gadget

I KNOW Nothing! And to prove that I have a question. Can the sidecar be hinged to keep it on the pavement instead of being lifted into the air?

I have never owned, driven, seen a sidecar in person. So I just have to show my ignorance and ask this.

take
care
a
friend
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Old 09-17-2009, 11:28 AM   #133
DirtyDR
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Quote:
Originally Posted by dbarnes180
I KNOW Nothing! And to prove that I have a question. Can the sidecar be hinged to keep it on the pavement instead of being lifted into the air?

I have never owned, driven, seen a sidecar in person. So I just have to show my ignorance and ask this.

take
care
a
friend
http://www.advrider.com/forums/showt...hlight=leaners
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Old 09-17-2009, 07:44 PM   #134
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thanks

Quote:
Originally Posted by DirtyDR
very interesting
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Arkansas to Alaska, 2010 ride report
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Old 09-20-2009, 08:34 PM   #135
grafikfeat
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Quote:
Originally Posted by Andy-Gadget
Less weight on the side car wheel, in proportion to the total weight of the outfit.
It moves the C of G closer to the bike centre line, with the ease of flying the chair that that entails.
It also raises the C of G as well, generally not a good thing.
I understand that...
I meant all that calculation works in a perfect world/set up.
Although... It does establish a good baseline.

There are too many variables. IE a Road King w/ a plastic velorex.
That's just plain dangerous.
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