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Old 06-04-2009, 02:51 AM   #106
Richard-NL
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Quote:
Originally Posted by Nemo DeNovo
I don't know if this has ever been tried, but I have no doubt that it would work. My knowledge of hydraulics tells me that the best choice of cylinders would be ones with the smallest possible rods in comparison to cylinder diameter, to keep the differential as small as possible. I don't have the $$ or the facilities to build a setup to test this, but I bet Richard or some of you other "well connected" FF's can find a willing and worthy test bed for this. I want a ride report, that might be a billion dollar patent I just gave away
Strange enough I’ve been walking around with a similar idea in my head, one time. (and maybe Claude can tell what he made in the past).
It came out of the idea of using a lot of cheap car parts for a new outfit. (cheap wheels, tires, suspension etc).
This hydro pneumatic system was used the first time on a complete car in 1955 on the famous Citroën DS 19.



I myself was thinking then of using parts of the (newer) BX from the eighties, still some scrap heap parts available and they don’t have the electronic high tech parts of the newer models. This (gas/fluid) suspension should give comfort, height would be adjustable (street versus off-road ground clearance), no wear of springs, loading the outfit full of stuff, would not have any effect on the set-up of the outfit etc and should (??) have some influence reducing the roll-effect. The roll-control wasn’t the first thing, I was thinking about, however. Difficult to built this on to an existing outfit and it was just an idea. (One time when I get rich and find time, I’ll may give it a go and see what it brings, maybe). Dunno



Are we still on-topic? A lot of stuff happening here……

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Old 06-04-2009, 06:00 AM   #107
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Quote:
Originally Posted by Richard-NL
Are we still on-topic? A lot of stuff happening here……

Richard-NL
A lot of stuff! A lot of knowledge!

This thread is the best one yet in the Hack forum. Fabulous!
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Old 06-04-2009, 07:43 AM   #108
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Here's a tip I've been wanting to post, and this is the best place to do it. I work on snowmobiles in the winter, and the shocks used on the front of the older ones (pre-'90s) were great for all kinds of custom uses. They are small, lightweight and available in black or chrome. They can be used as shocks or steering dampers and are easy to mount. Average center to center measurements are 7.5 inches compressed and 10.5 inches extended. They are damped 50/50, both directions. They are still available from aftermarket suppliers, or I have a couple of sources for NOS units. If anyone wants these, PM me and I'll get you a price and exact measurements.

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Old 06-04-2009, 08:22 AM   #109
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Sure is good to see that there is a lot of good company outside the box. Keep it up and maybe I will not feel so alone...lol. Good thread.
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Old 06-04-2009, 08:27 AM   #110
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Quote:
Originally Posted by Nemo DeNovo
Here's a tip I've been wanting to post, and this is the best place to do it. I work on snowmobiles in the winter, and the shocks used on the front of the older ones (pre-'90s) were great for all kinds of custom uses. They are small, lightweight and available in black or chrome. They can be used as shocks or steering dampers and are easy to mount. Average center to center measurements are 7.5 inches compressed and 10.5 inches extended. They are damped 50/50, both directions. They are still available from aftermarket suppliers, or I have a couple of sources for NOS units. If anyone wants these, PM me and I'll get you a price and exact measurements.


Cool Nemo.
Another 'in a pinch' option:
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Old 06-04-2009, 08:46 AM   #111
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Quote:
Originally Posted by claude
Cool Nemo.
Another 'in a pinch' option:
Isn't that a shock from an old MG? We restored a '51 MG "T" at the machine shop last year and it had shocks like that. Very cool

Snowmobiles are also a great source for other suspension stuff. Some have ball joints like the ones used in BMW front ends and the tie rod ends are great for all kinds of uses like sway bar links etc. And the newer ones have nice hydraulic disk brakes that could be adapted to a hack wheel.

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Old 06-04-2009, 10:08 AM   #112
claude
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Quote:
Originally Posted by Nemo DeNovo
Isn't that a shock from an old MG? We restored a '51 MG "T" at the machine shop last year and it had shocks like that. Very cool

Snowmobiles are also a great source for other suspension stuff. Some have ball joints like the ones used in BMW front ends and the tie rod ends are great for all kinds of uses like sway bar links etc. And the newer ones have nice hydraulic disk brakes that could be adapted to a hack wheel.
It was on a British car , not sure of the make. Similar lever action shocks were used on many cars even some American made ones. Kinda neat as the oil can be changed to different weights and the lever action can be modified if run through a bell crank system.
We have used shocks off of a john deere ( I think a gator) a few times. Small short etc like the shocks you pictured.
I did run a swaybar off a snowmobile once. It worked well but fatigured after time. Finally knocked the mounts off by hitting a raised manhole in a construction site somewhere in Chicago about 3 in the morning.
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Old 06-06-2009, 04:45 AM   #113
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Andy GADGET WROTE:
>>Interesting set up, but I can't see how it can have any influence on roll centre, as it is the suspension pivot points that determine this<<<

Yes, Andy you are correct. I have been wrong although there is something to be said for where the suspenion pick up points are located witin the area between the roll center and the center of mass in the big picture.
Maybe we shoud get more into double a frame suspension stuf on these rigs and see what kind of discussiosn we coudl get into.
Shoudl I delete my earlier posts?
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Old 06-09-2009, 11:35 AM   #114
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I found this while digging through my "archives," don't remember where it came from. It's a pretty good illustration of rake & trail, just keep in mind that it's talking about solo (2 wheel) bikes and not sidecar rigs. Less trail than what is considered safe on a 2-wheeler is what's considered preferable on a hack rig.

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Old 06-12-2009, 01:17 AM   #115
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Centre of roll, centre of gravity and how it affects motorcycle and sidecar handling.

Both of these terms are symmetrical vehicle suspension terms, and there in lies the problem, as when they are applied to asymmetrical motorcycle and sidecar suspension systems, the differences change the interrelationship of the two, and causes confusion.
One source of confusion is the direction the motorcycle suspension pivots in, and from this the length of its "Swinging arm", a car term.
This "swinging arm" is not to be confused with the trailing arm, that is the car term for the standard motorcycle rear suspension, what motorcyclists call the swinging arm.
The "swinging arm" referred to is the actual or imaginary suspension arm that connects the wheel to the chassis of the car, and is measured perpendicular to the centre line of the chassis, the virtual length can extend a long way past the physical limits of the chassis.
A pure trailing arm, the rear suspension arm of the motorcycle, is said to have an infinitely long "swinging arm" as there is no component of the suspension movement that isn't in the fore and aft plane of the vehicle.


An actual swing arm, where the term comes from.


A virtual swinging arm.


The front suspension of old VW beetles is an example of a pure trailing arm suspension.





The sidecar trailing arm has a small component of movement out of the fore and aft plane due to the toe in, but can effectively be considered to be infinite in length as well, as the other arm it has to relate to is infinite, so the intersection occurs at infinity.
The simple trailing arm suspension system has the huge advantage of being very compact relative to almost every other alternative.

Note that all suspension pivot points are square (or very close to square) to the centreline of the sidecar.

So why is this important?

It has to do with where the "centre of roll" (RC) of the vehicle is.
This in turn is important as the relationship of the RC and the "centre of gravity" has a great influence in the handling of the vehicle.

Centre of roll.

On a symmetrical vehicle (not a sidecar) the RC is the point where the line drawn from the tyre contact patch to the virtual swinging arm pivot point for both sides of the vehicle cross.
With the vehicle at rest, the crossing point (the "centre of roll") is on the centre line plane of the vehicle, but can vary greatly in height.
This point can be calculated using geometric techniques and is greatly influenced by the type of suspension, but can also be found by experiment, using the following definition.

The RC is the point that a horizontal force passes through, that, when this horizontal force is applied to the body of the vehicle, produces no body roll.

So a horizontal force can be applied at differing heights, until no body roll is observed.
Try this on a sidecar, and the only point that will not produce body roll is at ground level, so the RC of a trailing arm suspension system with "infinitely" long "swinging arms" is at ground level.
A vehicle can have a RC at ground level at one end, and a RC above ground level at the other, an example being early VW’s, and give rise to their name for quirky handling.


Centre of gravity.


The "centre of gravity" (CG) is the single point that the entire mass of the vehicle can be considered to be acting through.
If the vehicle is suspended from any point, the CG will be directly below the point of suspension.
On motorcycle and sidecar, a vehicle of low mass to start with, the mass of the passengers represents a large percentage of the total mass, but the presence or absence of the passengers, and the individual mass (weight) of the passengers, will move the centre of gravity, and in a way that isn't possible to calculate accurately.
If the added mass is above the CG the height of the CG will rise, if added below the CG, the CG height will fall.
The CG will move towards an added mass, and away from any removed mass.
“Body English” from the rider and passenger can greatly help the sidecar stability, but requires knowledge of how the forces on a sidecar outfit act together.
This knowledge can come from education, but is much more likely to have come from experience, a sidecar rider as passenger is educational, as the rider as passenger is applying weight transfer based on their experience as a rider.
Due to the low mass (relatively) of the motorcycle and sidecar to the mass of the passengers, the CG is very high, as the rider sits high on the motorcycle, passengers sit less high, but still raises the CG, which has a huge disadvantage as it takes less lateral force to move the effective CG outside the triangle of tyre contact patches the higher the CG and hence loss of stability.
A lesson that is often learnt the “hard” way is that as the sidecar wheel, or bike rear wheel, lifts, meaning the CG is outside the triangle of tyre contact patches, the stability is decreasing the higher the wheel lifts, thanks to the high CG and is an area of control that repays experience gained by practice.

CG to left of front wheel to back wheel line.


CG ahead of front wheel to sidecar wheel line.

Roll lever arm.

This is where the whole "centre of roll" thing comes together, at least from a car point of view.
If the CG and the RC are the same point, then there is no body roll as the vehicle corners, but as with all things engineering, it is a compromise.
The problem being that to have the RC high enough to be close to the CG on most vehicles requires the "virtual swinging arm" to point upwards drastically, which has some nasty effects on the suspension when cornering, known as "jacking", where the cornering forces act on the suspension to make the outboard suspension raise when loaded laterally.
A suspension system of this type would also change wheel track radically as the suspension is compressed, which trailing arm suspension doesn’t do.
The greater the distance between the RC and the CG the more body roll a given side force will produce, as the lever arm between the to points is greater.
Hence the disadvantage of the sidecar high CG
On F1 cars, the RC is often below the ground surface to prevent "jacking", and the CG is maintained very low by close attention to weight distribution on the rest of the car and drivers position. Which puts the two in perspective, in my opinion.


F1 racing car suspension, RC below ground level.

How this effects sidecar cornering.

On vehicles with more conventional suspensions, the relationship of the road contact patch with the tyre attitude, known as camber, is either maintained or intentionally changed as the suspension moves.
On motorcycle and sidecars (and old VW front suspension) the camber is not maintained as the sidecar rolls, so the tyre contact patch is reduced as the roll increases.


Tyre camber change in trailing arm suspension systems.

It is from trying to achieve this that the desire for a "no roll" sidecar suspension comes from, but it can't practically be achieved by suspension changes alone.


The change in tyre camber generates a turn cone in the opposite direction of the turn generating the camber change.

Anti-roll bars.

The only alternative still available to the sidecar is the anti-roll bar, now popular on some Australian built outfits, to make the sidecar roll laterally in a minimal manner, through simple constraint of suspension movement through the anti-roll bar alone.
An anti-roll bar works by resisting any asymmetrical suspension movement.
It will allow free movement of both suspension elements through their full travel, just so long as the movement of the suspension is the same.



As soon as one side of the suspension moves further or less than the other side, the anti-roll bar acts as a torsion bar spring and transfers some of the unbalanced forces towards the other side, hence resisting asymmetrical suspension movement.
By controlling the roll of the sidecar, the CG already high, stays more within the tyre contact patch triangle than if roll were unrestrained.
An anti-roll bar mounted transversely is already accepted practice in Australia, but the next step is to look at fitting an anti-roll bar between the back and front motorcycle wheels, which will need some clever engineering to link it to the front wheel, so it has minimal effect on steering, interesting dynamics are involved.
By fitting an anti-roll bar fore and aft, the roll of the sidecar, especially in turns away from the sidecar, it controlled and the tendency of the back wheel to lift is reduced by restraining the dip of the front suspension.
The anti-roll bar acts in this case to transfer some of the load transferred to the front suspension through weight transfer, to the back suspension, causing the back suspension to squat as the front suspension compresses, but this is in the nature of a parallel squat, and aids stability through restraining the CG within the tyre contact triangle.

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Old 06-12-2009, 09:13 AM   #116
claude
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Excellent post Gadget!
We have mounted anti-swaybars to a lot of diferent combinations. They can indeed make dramatic differences in the handling.
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Old 06-12-2009, 04:47 PM   #117
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<----considers moving to Middleburg, PA
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Old 06-12-2009, 08:03 PM   #118
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Andy, an exceptional post, thank you.

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Old 06-13-2009, 05:35 AM   #119
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Quote:
Originally Posted by Nemo DeNovo
<----considers moving to Middleburg, PA
The light is on for ya....could use help in the shop
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Old 06-14-2009, 12:58 AM   #120
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How to determine the location of the static centre of gravity of a motorcycle and sidecar.

The handling characteristics of a motorcycle and sidecar, in as far as the rate of turn that will lift the sidecar wheel (turning towards the sidecar) or the motorcycle rear wheel (turning away from the sidecar) is determined by the location and height above the ground of the centre of gravity (CG) of the motorcycle and sidecar.

To find the location of the static CG, that being the CG with only the motorcycle and sidecar, not with the rider or passengers on the outfit, requires some measurement and calculation, both are simple in essence.

First the simple application of high school physics that makes it all work.
It is using “beam reactions” that allow us to find the location of the static CG.
Some basic physics, Newton’s Third law, "To every action there is an equal and opposite reaction".
So the weight of the motorcycle and sidecar is acting on the ground at the tyre contact points, and the ground is pushing up with equal and opposite reactions at each of the three contact points.
The force acting on the ground is the total mass of the motorcycle and sidecar multiplied by the acceleration of gravity, F = M x A, Force (N) = Mass (Kg) x Acceleration of gravity (M/sec squared).
The sum of the three reactions equals the total mass of the motorcycle and sidecar.
The magnitude of the reactions is determined by their distance from the CG of the motorcycle and sidecar.
The easy way to measure these forces is to assume that gravity (G) is a constant acceleration, and it is common to all, we can take it out of the equation, so only the mass part remains, measured in Kg (it can be in pounds, but I am a metric person, so I will be working in Kg’s, it is all ratios in the end).

As the easiest way to measure weight is a set of scales, that is what we will use, bathroom scales, but as most don’t go far past 120 Kg, we need to play with levers to reduce the measured weight.
To achieve this an inverted Second Class lever is used, see, high school physics wasn’t wasted after all.
I use 50mm 1.6mm wall thickness RHS, and 50mm angle iron to fabricate the following.




It doesn’t matter how long the beam is, but the longer the better, as the result will be slightly more accurate, particular attention needs to be made that the top (wheel) angle iron is in the centre of the two lower angle irons.

This apparatus shows how beam reactions work, as the action (tyre, and so weight on the tyre) is in the centre of the beam, the two reactions add up to the action, but are each half the action.
If you have a very heavy outfit, with axle loads more than twice the max reading of the scales, then make the top angle iron 1/3 of the way from the end away from the scale, and multiply the reading by 3 rather than 2.
We are going to use the difference between the reactions to calculate where along the beam the action is acting, simple really.

To calculate the height of the CG as well as its horizontal position, we need to take six readings, the weight on the three wheels with the sidecar level, and the three readings with the sidecar at an angle to the ground.
The angle reading is easiest done by lifting the sidecar wheel by about 250mm.

We are going to have six beam reactions, one reading for each condition for each of the three beams.
The beams are, the front wheel to the back wheel of the bike, the back wheel of the bike to the sidecar wheel, and the sidecar wheel to the front wheel of the bike.
We need the lengths of all three beams, centre of tyre contact patch to centre of tyre contact patch.
For the angle reading, we also need the wheel track of the outfit as well.




Draw two triangles to a scale that suits of the three beams, use the floor at full scale if you like, (R1) = reaction one.









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