R1100S - GS length torque arm (365 mm).

[Tapio]

Pinning the strips together half way will triple this load capacity to 7,100 lbs

I'm not sure if I agree with you here.
Yes, if the left strip wants to buckle to the left, and the right strip to the to the right, or the other way around: the left wants right and the right wants left. Then your screw and spacer will prevent this.
But what if both strips wants to buckle in the same direction? Your screw and spacer can do nothing to stop this from happening. Bin it.

[Blackal]

Great to see all the different opinions and concerns.

"As I've said in earlier posts, this is a short term temporary arrangement until I get a genuine GS arm. ...... ........... ........ ....... so the bike is being used in town (smooth streets) just to tootle around doing errands etc."

For those number-doubters, I presume you've driven over bridges like the Clifton Bridge, Forth Road Bridge, Humber Bridge, or that you've flown in those huge airliners with the bendy wings. Then there are those skyscraper lifts. Errrk.

Cheers.

I sense that you might have taken the hump.

But sure, as an experiment on smooth roads - the risk is perhaps mitigated, and in fact -is your risk in any case.


Al

[Archie]

A fault with a similar piece of kit left a mate of mine unconscious in the outside lane of the M5.

Let us know which hospital ward you end up in and we'll have a whip-round for a card.

[mh374]

Surely the short term temporary arrangement is to leave the original BMW part on the bloody bike!! Plod and insurance company will have a field time if it all goes tits up....

some people........

[HerrFlick]

Great to see all the different opinions and concerns.

"As I've said in earlier posts, this is a short term temporary arrangement until I get a genuine GS arm. ...... ........... ........ ....... so the bike is being used in town (smooth streets) just to tootle around doing errands etc."


Cheers.

I sense that you might have taken the hump.

Al

"Taken the hump". Had to look that up.

Oh heck no. Not at all.

Just trying to get message out to everyone that I'm only tootling about to the shops and 'the high street' at about 35 mph or less.

Cheers Al.

.

[Corvus]

There is one force that herrflick does not have appeared to have considered. Why was the paralever introduced in the first place? Unless my memory deceives me (wouldn't be the first time) it was as an answer to shaft jacking (insert jokes using myleene klaas here). Is that true or not?

So, does the shaft jacking counter force place the link bar under compression or tension when accelerating? As far as I can fathom, it will place it under compression. Is that the reason it was subsequently moved on top? Or am I well and truly barking up the wrong tree?

Anybody actually seen what happens, say on a rolling road?

[Corvus]

Here's a thought.

Is the link bar pulled or pushed with the effect of the weight of the machine and rider etc? It seems as if it is pulled? Under tension.

If my previous post and the above suggestion are correct (maybe they're not) then the two forces (transmission reaction vs machine plus rider weight) tend towards cancelling each other. To some degree or other.

In a theoretical sense, assuming general truth in what I've suggested, then if the machine and rider weighed a certain amount and the engine could generate a certain accelartive force, then the link bar could be irrelevant at that point. Purely theoretical and assuming I'm on the right lines. The swingarm holding itself up by its boot strings! Hee Hee.

[HerrFlick]

There is one force that herrflick does not have appeared to have considered. Why was the paralever introduced in the first place? Unless my memory deceives me (wouldn't be the first time) it was as an answer to shaft jacking (insert jokes using myleene klaas here). Is that true or not?

So, does the shaft jacking counter force place the link bar under compression or tension when accelerating? As far as I can fathom, it will place it under compression. Is that the reason it was subsequently moved on top? Or am I well and truly barking up the wrong tree?

Anybody actually seen what happens, say on a rolling road?

Et tu Corvè?

Well, ahem koff koff, I have considered compression loading and written about it at length, since compression loads are what cause column buckling.

That's what all the calculations were about: to determine ultimate failure loads and the margin of safety I had with my bits of 'ally'.

A 10x margin as it happens, without including the effects of big isolating rubber bushes. These take the sharp edge off sharp impact loads to the tune of 5x and more.


Now - back to jacking, and other stuff:

R1200 and position of torque arm: I wrote about this too. It was moved up to increase ground clearance and so avoid failure by rock. Seemples.

Why was paralever introduced?

- because with the old swinging shaft (did I just say that?) system, the pinion climbed on the ring gear, which in turn forced the drive shaft to rise and so lift the chassis. The reverse on throttle over-run. Bike rocked like a rocking horse.

- with the second drive joint at the rear wheel (paralever), that rise/fall now takes place around the second joint, without affecting the swing arm position (and the bike attitude).

Back to the R1200: with the overhead torque arm there is now compression under braking and tension under acceleration.

As for shock loading over rough surfaces, intuitively I think it's much of a muchness: ABS off and rear wheel locked as it hits the other edge of that big pothole (and we're not off road yet), will produce severe impact loading on the torque arm: compression for the R1200 and tension for the R11x0.


As I think about this situation, two points come to mind:

- the peak kinetic energy available from an engine to produce wheel spin (over potholes say) is limited to the maximum momentary energy available from that engine.

- by contrast, that same engine, applying that energy input over a longer time, can cumulitively raise the total kinetic energy (high road speed) of the bike/rider system to well beyond the energy available for momentary wheel spin.

Point being that once travelling at high road speed, any braking or brake lock through potholes will produce huge shock loads, and will far exceed the loads produced under acceleration over the same potholes.

In the case of the R1200 these will become compression forces in the stay arm and tensile forcess in the R11x0 stay arm.

As for a rolling road view: well a funny thing happened on my way to the forum: I got his brilliant idea of mounting (ohhh do be quiet) my action cam such that I can record the behaviour of my Heath Robinson creation as I ride. (Won't be long Dear - just dashing out to the garidge for a moment - have you seen my duct tape? )

('Garidge' is how you Poms pronounce the French 'gar-arrrge'). Love it.

With any luck, those in the Coliseum corporate boxes won't be disappointed.

Did I mention I'm 6'5" tall and my initials are 'JC'. No. Probably not. But they ARE.

Cheers

John C.

PS: once replaced with a GS arm I'm planning a load test (to destruction) of my Heath Robinson torque arm.

I'm quite looking forward to what it will tell Us and of what everyone can learn from it, but unless we experiment and analyse we learn nothing of use for the everyday man. Enough said there.

[HerrFlick]

Lot's of "experts" screamin' and shoutin' and tarrin' and featherin' just 'cos of everyone else.

I have a confession to make:

I made the strips from wet cardboard and painted them silver to look like ally, jost te get ye all really going eh?

And d'jnow waht? Y'all fell fer it. Arses over tits.

What a bunch of dunderheeds.!

Come back when you've attained a few relevant 'O' levels and successfully completed couple of years of pre-graduate fundamental engineering principles.

Otherwise, if all you have to offer to the discussion are scary thoughts or tales of when your mate fell off because he went over a cliff, then would you all please just go away.

Cheers.

JC

[HerrFlick]

Pinning the strips together half way will triple this load capacity to 7,100 lbs

I'm not sure if I agree with you here.
Yes, if the left strip wants to buckle to the left, and the right strip to the to the right, or the other way around: the left wants right and the right wants left. Then your screw and spacer will prevent this.
But what if both strips wants to buckle in the same direction? Your screw and spacer can do nothing to stop this from happening. Bin it.

All true Tapio.

Once I had linked the two sides, intuitively, I just didn't like the look, and transverse hand deflection only reinforced your ideas.

In the interest of engineering analysis, and lying awake in the early hours pondering the duality of the photon (as one does), it dawned on me that a zig-zag linking between each strut was the way to go.

Will incorporate this into destructive load testing. And the more destructive the better.! Muaahh harrhh harrrhhh.

[Corvus]

There is one force that herrflick does not have appeared to have considered. Why was the paralever introduced in the first place? Unless my memory deceives me (wouldn't be the first time) it was as an answer to shaft jacking (insert jokes using myleene klaas here). Is that true or not?

So, does the shaft jacking counter force place the link bar under compression or tension when accelerating? As far as I can fathom, it will place it under compression. Is that the reason it was subsequently moved on top? Or am I well and truly barking up the wrong tree?

Anybody actually seen what happens, say on a rolling road?

Et tu Corvè?

Well, ahem koff koff, I have considered compression loading and written about it at length, since compression loads are what cause column buckling.

That's what all the calculations were about: to determine ultimate failure loads and the margin of safety I had with my bits of 'ally'.

A 10x margin as it happens, without including the effects of big isolating rubber bushes. These take the sharp edge off sharp impact loads to the tune of 5x and more.


Now - back to jacking, and other stuff:

R1200 and position of torque arm: I wrote about this too. It was moved up to increase ground clearance and so avoid failure by rock. Seemples.

Why was paralever introduced?

- because with the old swinging shaft (did I just say that?) system, the pinion climbed on the ring gear, which in turn forced the drive shaft to rise and so lift the chassis. The reverse on throttle over-run. Bike rocked like a rocking horse.

- with the second drive joint at the rear wheel (paralever), that rise/fall now takes place around the second joint, without affecting the swing arm position (and the bike attitude).

Back to the R1200: with the overhead torque arm there is now compression under braking and tension under acceleration.

As for shock loading over rough surfaces, intuitively I think it's much of a muchness: ABS off and rear wheel locked as it hits the other edge of that big pothole (and we're not off road yet), will produce severe impact loading on the torque arm: compression for the R1200 and tension for the R11x0.


As I think about this situation, two points come to mind:

- the peak kinetic energy available from an engine to produce wheel spin (over potholes say) is limited to the maximum momentary energy available from that engine.

- by contrast, that same engine, applying that energy input over a longer time, can cumulitively raise the total kinetic energy (high road speed) of the bike/rider system to well beyond the energy available for momentary wheel spin.

Point being that once travelling at high road speed, any braking or brake lock through potholes will produce huge shock loads, and will far exceed the loads produced under acceleration over the same potholes.

In the case of the R1200 these will become compression forces in the stay arm and tensile forcess in the R11x0 stay arm.

As for a rolling road view: well a funny thing happened on my way to the forum: I got his brilliant idea of mounting (ohhh do be quiet) my action cam such that I can record the behaviour of my Heath Robinson creation as I ride. (Won't be long Dear - just dashing out to the garidge for a moment - have you seen my duct tape? )

('Garidge' is how you Poms pronounce the French 'gar-arrrge'). Love it.

With any luck, those in the Coliseum corporate boxes won't be disappointed.

Did I mention I'm 6'5" tall and my initials are 'JC'. No. Probably not. But they ARE.

Cheers

John C.

PS: once replaced with a GS arm I'm planning a load test (to destruction) of my Heath Robinson torque arm.

I'm quite looking forward to what it will tell Us and of what everyone can learn from it, but unless we experiment and analyse we learn nothing of use for the everyday man. Enough said there.

Ok, so you considered it. But you didn't say you had.

Re the pinion climbing thing. I agree with what you said here. The implications of that are pretty staggering. The bike is being hoisted up at the swingarm pivot by the pinion teeth levering against the wheel teeth, using the pinion bearings for stability. Akin to lifting a shovel load of silver painted wet cardboard with your hands close together near the handle. Some strain on the pinion shaft or what?

Look forward to the camcorder results. Another test could be contrived by putting your front wheel against a wall and driving the machine until it stalls. This will show whether the thin strips of painted cardboard tend towards compressing or not.

The destructive test is a great idea. Before you test it to destruction how about trying some offset loads to see what happens.

[HerrFlick]

...

[Corvus]

"Ok, so you considered it. But you didn't say you had."

Arrrhh gee Corvus - from your response(s) I thought you were in no doubt re the dynamics of the situation and the importance I placed on compression loads. Very disappointing to hear your current outook.

However if that's your perspective then I have only myself to blame, in that I have not taken the time to clarify your understanding of each side of the argument.

Out of time now, but will return later.




JC.

I'm always in doubt, which why I haven't smugly hung up the slide rule and I'm still plugging away to try to get to the bottom of this. It's an interesting one.

My current line of thinking is that maybe the link is never under much in the way of compression and spends a reasonable amount of time pretty neutral. At least on hard Tarmac. My riding against a wall thought experiment lead me to think that maybe it is off road where the link can be subjected to the most compression. We need a scenario where there is no rearward weight transfer whilst full power is being called for. Apart from riding against a wall, off road conditions can give this circumstance.

Make sense or not?

[HerrFlick]

"Ok, so you considered it. But you didn't say you had."

Arrrhh gee Corvus - from your response(s) I thought you were in no doubt re the dynamics of the situation and the importance I placed on compression loads. Very disappointing to hear your current outook.

However if that's your perspective then I have only myself to blame, in that I have not taken the time to clarify your understanding of each side of the argument.

Out of time now, but will return later.




My reply was a bit thoughtless Corvus. My apologies. One too may sips of shiraz.

JC.

I'm always in doubt, which why I haven't smugly hung up the slide rule and I'm still plugging away to try to get to the bottom of this. It's an interesting one.

My current line of thinking is that maybe the link is never under much in the way of compression and spends a reasonable amount of time pretty neutral. At least on hard Tarmac. My riding against a wall thought experiment lead me to think that maybe it is off road where the link can be subjected to the most compression. We need a scenario where there is no rearward weight transfer whilst full power is being called for. Apart from riding against a wall, off road conditions can give this circumstance.

Make sense or not?

[HerrFlick]

"Ok, so you considered it. But you didn't say you had."

Arrrhh gee Corvus - from your response(s) I thought you were in no doubt re the dynamics of the situation and the importance I placed on compression loads. Very disappointing to hear your current outook.

However if that's your perspective then I have only myself to blame, in that I have not taken the time to clarify your understanding of each side of the argument.

Out of time now, but will return later.




My reply was a bit thoughtless Corvus. My apologies. One too may sips of shiraz.

JC.

I'm always in doubt, which why I haven't smugly hung up the slide rule and I'm still plugging away to try to get to the bottom of this. It's an interesting one.

My current line of thinking is that maybe the link is never under much in the way of compression and spends a reasonable amount of time pretty neutral. At least on hard Tarmac. My riding against a wall thought experiment lead me to think that maybe it is off road where the link can be subjected to the most compression. We need a scenario where there is no rearward weight transfer whilst full power is being called for. Apart from riding against a wall, off road conditions can give this circumstance.

Make sense or not?

Yes. Lots of sense. Off road or on bumpy tarmac will cause the greatest shock loads under braking or acceleration. Off road is the most likely place to get a sideways whack sufficient to make the 'column' collapse if it's under compression at that moment.

Your thought about the link never being under much pressure during steady riding etc is spot on. Is why I'm happy to tootle to the shops at 35 etc. , but would not consider a long trip etc.

But if I was stuck miles from anywhere with a broken stay arm, say on a an R11 GS, I'd have an idea of how to fix it 'enough' to get moving (slowly).

Throttling up against a wall would be a good one to see. How would Sir like his clutch? Medium rare or well done?