What does CARC refer to?

[Huzo]

WTF are you talking about Pete? I think you and I are talking about 2 different things.

So let's go back to one thing.
Does the rear wheel move up and down in a circular arc, or some other path of motion.
That.... is (or was), the question.
And the correct unambiguous answer, without a blanket of "humour" was given.

[beetle]

Not telling.

[tris]

Let me have a go

The distance from the swing arm bearing to the centre of the wheel must be a fixed dimension as it is defined by the swing arm casting

So the bearing centre to bearing centre must describe an arc as the swing arm goes up and down

However, the torque provided by the engine/bevel box is reacted by the reaction rod.

Ito do that it uses essentially pin joints in 4 locations (2 on the reaction rod and one at the swing arm to frame bearing and the rotation inside the bevel box PLUS as sliding joints either end of the drive shaft

So the CARC mechanism can't change the way the wheel travels but it can change the way bike reacts reacts to applied torque

Just my 10p

[Huzo]

The distance from the swing arm bearing to the centre of the wheel must be a fixed dimension as it is defined by the swing arm casting

So the bearing centre to bearing centre must describe an arc as the swing arm goes up and down

' Never said otherwise.

[Huzo]

I will not. There will be shouting, however. I think you and I are having a failure to communicate. It cannot move the way Mr Orange says. Impossible.

Well in that case we are agreed.
I can still hear crickets in North America !

[Orange Guzzi]

I will not. There will be shouting, however. I think you and I are having a failure to communicate. It cannot move the way Mr Orange says. Impossible.

Some parts do, some parts do not.  There are a lot of moving parts in the set up.  Some parts are even rotating at high rpm's at a right angle. 



One test I did, I removed the shocks, dropped the swing arm down until the u-joints started binding and then raise it until they started binding.  The total range of motion as measured at the axle was around 8 inches.  With shocks mounted, the axle is 1 inch below center line of the output shaft.  Magni does not have any specs on this min/max.  Just a warning not to bind the u joints. 

Magni called the system Parallelogrammo.

So what good is all this?  The torque arm pushes against the frame if mounted on the bottom of a Magni swing arm and pulls if mounted on top the swing arm.  This pushing or pulling compresses the suspension rather letting the wheel drive under the bike and raising the back of the motorcycle. 

The Magni uses snap rings on the splined ends.  Bellville/springwashers are stacked up between the rear u joint and rear snap ring to push the splined drive shaft forward and keep some pre load on it.  It rattles.   The pictures of the carc appears to use a coil spring to push the drive shaft on direction. 

I recently came across an article regarding changing the length of the torque arm to change the swingarm geometry.  I did not read it yet.  Moto Guzzi has a spec. on the ball eye end mount distance.  The Magni is fixed as an equal distance as the swing arm.  It would be interesting to see what affect changes in this distance would have on the rear end.   

Carc, it work, rattles and still needs chain lube.

[oldbike54]

Well in that case we are agreed.
I can still hear crickets in North America !

 This is an Ozzie argument , us Northerners have learned not to get involved , well , except for Tris . You never know about the Brits , although he is correct .

[Huzo]

This is an Ozzie argument , us Northerners have learned not to get involved , well , except for Tris . You never know about the Brits , although he is correct .

There is no argument.
This started as a response to the statement that the rear axle moves up and down in a straight line, and I said it is in an arc.
All the trudging down side tracks to muddy the waters won't change a damn thing. It's a tactic often used when you realise you've been wrong, so you keep talking about something else until you stumble onto something that's correct and then dwell on that.
I highlighted the topic in question a couple of times. The Guzzi set up in question is not a parallelogram and never will be.
(EDIT):
For the axle to move vertically with slight lateral displacement, there would need to be vertical struts on each end of the horizontal swingarm and torque reaction arm, those two would have to be the same length and parallel as would the swingarm and reaction rod, and each corner must be pinned.
Similar in appearance and function as a draftsmans drawing apparatus.
THAT ! Is a parallelogram(o)...

[oldbike54]

There is no argument.
This started as a response to the statement that the rear axle moves up and down in a straight line, and I said it is in an arc.
All the trudging down side tracks to muddy the waters won't change a damn thing. It's a tactic often used when you realise you've been wrong, so you keep talking about something else until you stumble onto something that's correct and then dwell on that.
I highlighted the topic in question a couple of times. The Guzzi set up in question is not a parrallogram and never will be.

 You got no argument from me on that now did you ? Sorry if you missed my attempt at humor , always thought you Ozzies saw the absurdity of life the same as me 

 Dusty

[Tom]

Can't Always Ride Correctly.

[Huzo]

You got no argument from me on that now did you ? Sorry if you missed my attempt at humor , always thought you Ozzies saw the absurdity of life the same as me 

 Dusty

Hi Dusty.
I'm happy to put my sense of humour side by side with most run of the mill souls, and history will decide where I placed on the scale. It wasn't your attempt at humour that was under the microscope.
What irks me, is when I'm given a one word response to a question like post #17 with a response like #18 and metaphorically dismissed with a wave of the hand, and subsequent responses from here and abroad answering the question that wasn't asked, using "humour" to replace sound geometric knowledge.
The one and only point that I had any interest in arguing centres around #17 and #18. Although I have confidence in my train of thought, there will be some on this forum that would like to know the facts, versus the opinions of a smattering of semi informed luminaries, (some of which are actually "revered", I've been recently informed)...
I'm fortunate that Pete decided to post on the subject, that got most of the Wolves off my back..(most).

[Huzo]

Now that is a worthy and relevant question. Trust a Kiwi to keep focus on the issues!

What do/did you see as the issue/s ?

[oldbike54]

 Huh ? Oh , someone was wrong on the internet 

 Dusty

[Idontwantapickle]

Here, direct from N.A.

The wheel moves in an arc as Huzo noted.
The CARC doesn't rattle unless it is broken. It's the transmission.
But y'all keep "discussing" it. 
 

Hunter

[Idontwantapickle]

Huh ? Oh , someone was wrong on the internet 

 Dusty

Wait! What? NOOOOOOOOOOO!!!!!

[oldbike54]

Wait! What? NOOOOOOOOOOO!!!!!

 On Wild Guzzi no less , I am still reeling 

 Dusty

[Huzo]

Here, direct from N.A.

The wheel moves in an arc as Huzo noted.
The CARC doesn't rattle unless it is broken. It's the transmission.
But y'all keep "discussing" it. 
 

Hunter

Having fun ?
I sure as hell am...

[Huzo]

Nothing wrong with being incorrect, I'm sure it must be possible to get over it !
If it ever happens to me I hope I accept it in good, ummmmm....Humour!!!   

[oldbike54]

Nothing wrong with being incorrect, I'm sure it must be possible to get over it !
If it ever happens to me I hope I accept it in good, ummmmm....Humour!!!   

 Would you like a list so we can all have a good laugh Peter 

 Of course I am only kidding , being a bit of a freak for accuracy myself ...

 Dusty

[Idontwantapickle]

Having fun ?
I sure as hell am...

But of course!! Fun knows no continental boundary!

 

[Huzo]

Why oh why can't we settle on a location (Mandello 2021 ?) and bring a list of each other's major mistakes on the forum and slang it out on the shores of Lake Como...I've got mine written on the back of a postage stamp so I'm ready.
I would just love for that to happen, imagine the sparks !!! FANTASTIC
I'll be there for sure and would love to re ignite some threads at Monte's Cafe' and the biggest tosser can be thrown into the lake over the road..
Priceless !

[Orange Guzzi]

I made a prototype of the Magni swingarm to full scale.   I am going to lay it out in auto cad also to get the exact results.  But in the mean time, I was surprised with the results.  There is a lot going on and much I would assume to be negative secondary affects. 

I found that the axle does not move in an continuous arc or a slope, but a sideways bell curve.  The axle does not rotate around the swing arm pivot point in a concentric circle.  The axle does not move at the same speed as it goes thru the range of travel.  The axle does not maintain the same distance from the front swingarm pivot point.  Depending on where the center line of the rear gear box spline shaft is located relative to the transmission output spline shaft, several things can change.  If the axle is below the transmission spline shaft with the shock fully extended, the axle will slow down as the two spline shafts reach alignment and then speed up as the axle rises above alignment.  Then I found that the distance between the swingarm pivot point on the frame and the axle changes nearly 1 inch in 3-1/2 of shock compression.  This again depends on the starting point of the axle.  If the axle is below the center line, the swing arm will get longer as the spline shafts align and then get shorter as the shock fully compresses above the center line.  This can make your bike get go from short, to long, to short.  This shortening and lengthening along with the changing speed of compression and rebound has to affect the dampening function.  The shock speeds up and slows down at various points of a full stroke.  Not just at the beginning or end.  Changing the length of the torque arm affected the speed of the shock at different points along with raised or lower the rear of the frame. 

While the concept stops the driving of the wheel under the frame, the raising and lowering of the axle affect the speed thru the stroke and the dampening function of the shock.   There is a 1 inch or more change in the distance between axles. 

I have been wanting to dig into this geometry question for a long time.  You all got me motivated.  In my mind, I knew there was much more going on.  One of the test I did,  see how a 1 piece swing arm of the same length move thru the range of travel of the shock.  The shock speed changes as it moves thru the range, the distance between the pivot point and axle stay the same.  The amount of change in the length of the bike is about half of the Magni swing arm.   I found the function of the shock speeding up and slowing down to be related to how perpendicular the shock is to the swing arm.  The lower shock eye moves forwards and backward more, the further the top of the shock is moved in front of the bottom eye.  The range of motion of the axle is also more than the range of shock travel if the shock is not perpendicular.  Over 1 inch on the 3-1/2 travel  shocks on my bike or 4-1/2 inches plus.   Keep this in mind when slamming a bike with shorter shocks or moving the lower shock eye back to lower your bike.  The clearance between the fender and tire needs to be more than the maximum shock compression. 

Any corrections welcome, I am about learning new things and being corrected when wrong.  Spelling, grammar and punctuation, that is another issue. I need lots of help in that area.   

[Muzz]

What do/did you see as the issue/s ?

Huzo, as I understand it, (and I could be wrong) part of the problem with a shaft drive set-up is the UJ. Although it is not the crux of your original post it does have a bearing on the solution.

My Breva has the drive shaft running through the swing arm which acts as a torque tube. A UJ (as I understand it) does not actually revolve at a constant speed and actually speeds up and slows down. This would mean that although the reactive forces, and your CARC is a much more refined version of what is on the Breva are dealt with, there is still the problem that there is not a constant force being exerted on the joint in question. Normally, this is solved by using two UJ's in the drive train and cancelling out this effect. A CV allows the shaft to tun at a constant speed, and using a CV instead of a UJ in the system (to me at least), would infer a much more even strain on the drive train.

I am a bear of little brain, but I have yet to hear my hypothesis shot down.

[Huzo]

Yes Orange, that is all quite true. You do accept though that the Guzzi arse end is not a parallelogram as is the model you constructed, do you ?
A damn interesting thing to play with all the same.
BTW, I reckon your spelling is damn good. Only two mistakes if you can accept "thru" as an acceptable abbreviation.
They are on line #4 and line #24 

[Huzo]

I thought that your post on the CV was a good time to stick a knife in mine and go on with your direction.
The pro's and con's of CV versus UJ are above my head but I'll bet my flat tappets that  Roper can educate us on the topic.
Sounded like a damn good talking point to me.

[mrrick]

So do we know why the CARC is going away? it's so-called non-serviceable nature ,maybe?
And are the new bikes going back to an earlier design, or a new improved one?

[pete roper]

Because it doesn't *look* like what crotchety old men and hipsters think the arse end of a motorbike should look like, because it's more expensive and because people, just generally, are stupid and as thick as pig dribble.

What will it be replaced with? 1950's technology to appeal to demographic #1 listed above.

Pete

[wheaties]

Orange,

Sounds like you're onto a brilliant piece of engineering deduction.  I wonder if your calculations take into account the wheel in contact with the pavement as opposed to being free wheeling, "floating", as the suspension goes up and down.  Not sure how to think about a wheel accelerating under load, but it can't spin up without transferring force to the road.

Well done,

Matt

[Orange Guzzi]

Orange,

Sounds like you're onto a brilliant piece of engineering deduction.  I wonder if your calculations take into account the wheel in contact with the pavement as opposed to being free wheeling, "floating", as the suspension goes up and down.  Not sure how to think about a wheel accelerating under load, but it can't spin up without transferring force to the road.

Well done,

Matt
 

Some times the shock is loaded from the top, sometimes the bottom.  Bumps push the shock up and wide open throttle push the shock down.   Shifting all the weight to the road. 

I measured between the axle and swing arm pivot point.  The swing arm pivot point is fixed and the axle can move forwards and backwards as it moves thru the range of motion allowed by the shock length while extended and fully compressed. 

We are talking Magni, not Carc.

[wheaties]

Some times the shock is loaded from the top, sometimes the bottom.  Bumps push the shock up and wide open throttle push the shock down.   Shifting all the weight to the road. 

I measured between the axle and swing arm pivot point.  The swing arm pivot point is fixed and the axle can move forwards and backwards as it moves thru the range of motion allowed by the shock length while extended and fully compressed. 

We are talking Magni, not Carc.

I think I get what you're saying.  In all fairness, you're way out ahead here.  I am humbly reminded of my personal light bulb going off long ago when I realized "Oh, the differential does it's job in part because the wheels are in contact with the road", or "Oh... the gears in the transmission are still turning because the wheels are turning too".  Thus my not so surprising insight is, "The cantilever mechanism (CARC or Magni)  will behave differently depending on whether the wheel is in contact with the ground or not".  I'm reasonably certain you've already thought of that.

Matt