charlie.c
Member
Just a thought. When BMW and Kawasaki see fit to use paralever rear suspension to cancel out torque reaction, how does the Tenere get away without it?
what's the point of paralever
- Thread starter charlie.c
- Start date
Yamaha doesn't "get away" from using it, they just don't think the complexity of an addition ujoint justifies the benefit of less shaft jack raising/lowering of the bike. I'm glad they don't make the bike more complex for what it is. It's not like we use them for motogp racing.
EricV
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Wrong thinking on your part. Ask the question you asked in the subject line, instead of presuming incorrectly that BMW and Kawasaki have found the one true path.charlie.c said:
To answer your subject line question, there is no point. It's just what happens when there isn't any engineering oversight and you let them 'play' instead of teaching them to 'work'. The BMW design is a known flaw that continues to suffer failures, on every platform using it, even when new and low miles, in some cases. Sort of like single sided swing arms, again, no point, just a foolish waste of design efforts that lessens the integrity of the bike.
Have you ridden a Super Tenere yet? If so, did you notice any major issues with "torque reaction"? No one else has. Gee, no problem, why throw money, time and effort into fixing a non-existent problem? I suppose if you are trying to design in failure so your customers will "support" their dealers with repairs, then you have a reason! Drives the cost of the product up too. Win-win!!
Dogdaze
Well-Known Member
I agree with EricV on this point, but as BMW have implemented this system for such a long time they have 'branded' it theirs, so customers have come to expect it. Although on a personal note, I do like the look of the single sided swingarm, has it's uses for wheel removal, but other than that, pointless on a donkey like the S10, GS or the like.
Squibb
Well-Known Member
From my memories of old BMW's, pre paralever, they somehow rose up at the rear when accelerating hard. I am talking mid 1950s onwards through 1970s so relatively low powered bikes, with engine speed gearboxes & two sides on the swing arm. Back in the day, I was told it was all to do with the angle of the cut of the bevel drive gears, the direction of rotation of the shaft & the relatively unsophiticated suspension units we all endured. Presumably para lever came along to cancel this effect; I don't know?
Certainly Yamaha seem to have dealt with the issue well on my FJR & S10, without over-engineering the solution.
When it comes to single sided swing arms, these probably stretch back to the Elf Honda race bike experiment, reprised on the VFR & 916 Duke - they look OK, are convenient but otherwise pretty pointless.
............. KEN
Certainly Yamaha seem to have dealt with the issue well on my FJR & S10, without over-engineering the solution.
When it comes to single sided swing arms, these probably stretch back to the Elf Honda race bike experiment, reprised on the VFR & 916 Duke - they look OK, are convenient but otherwise pretty pointless.
............. KEN
Imagine holding ONE arm extended out in front of you.
Now clench a length of broomstick in your fist holding the stick either straight vertical or horizontal.
Now I walk up to you and grab that stick and attempt to twist it.
You are almost powerless to stop even my easiest efforts. The leverage is FAR in my favor.
Now you extend your other arm and hold that stick with both hands.
Now your ability to rigidly support that stick against the forces I exert has increased......what? 10 fold? More?
Single sided swingarms are a strange engineering request with nary a single legitimate payoff.
And putting one on a bike designed to be rugged? Designed to be a packmule? Designed to be RTW trusted\respected?
I never understood. And to do so is to risk the goodwill of the customer on a bike that otherwise is a marvel! (my opinion anyways)
I am so grateful the Tenere has that stout packmule swingarm-shaft drive design. Nothing "posing" about it!
Fair warning though to my Tenere brethren........If\when a GSA ever becomes available with a non-ego inspired double sided swingarm and conventional forks, I'M IN!
I know I know, that doesn't address everything suspect about modern BMW, but it'll darn sure point to a huge fundamental change internally. And in the right direction!
Now clench a length of broomstick in your fist holding the stick either straight vertical or horizontal.
Now I walk up to you and grab that stick and attempt to twist it.
You are almost powerless to stop even my easiest efforts. The leverage is FAR in my favor.
Now you extend your other arm and hold that stick with both hands.
Now your ability to rigidly support that stick against the forces I exert has increased......what? 10 fold? More?
Single sided swingarms are a strange engineering request with nary a single legitimate payoff.
And putting one on a bike designed to be rugged? Designed to be a packmule? Designed to be RTW trusted\respected?
I never understood. And to do so is to risk the goodwill of the customer on a bike that otherwise is a marvel! (my opinion anyways)
I am so grateful the Tenere has that stout packmule swingarm-shaft drive design. Nothing "posing" about it!
Fair warning though to my Tenere brethren........If\when a GSA ever becomes available with a non-ego inspired double sided swingarm and conventional forks, I'M IN!
I know I know, that doesn't address everything suspect about modern BMW, but it'll darn sure point to a huge fundamental change internally. And in the right direction!
The single sided swinging arm became a fashion after it was extensively used to enable quick tyre changes in endurance races.
EricV
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Ducati will have shaft drive on the Multistrada 1200 Enduro before BMW wakes up and stops making crap with single sided swingarms & Lever de jours . Note that the 1200 Endoro is the first Multi to have a double sided swingarm. Someone there really was paying attention. That bike, with the exception of the chain drive, is leaps and bounds ahead of the other poseur Multistradas.snakebitten said:
blitz11
Well-Known Member
As much as I enjoy Snakebitten's posts, his argument on torsion is wrong. (Sorry.)
The Single sided swingarm reacts against the swing arm axle at the two bearing points. On a BMW, those bearings are located outside of the driveshaft; on both side, those bearings are on the outside frame.
ON the Super 10, the swing arm bearings on the right side are in the outside frame on the right, but INBOARD of the drive shaft on the left side. This creates a smaller moment arm, increasing the forces on the bearings to react against the torsional force placed on the swing arm. If you think about how a rear tire handles torsional forces, single sided vs. double sided for this application makes very little difference. Making the cross section of the single side large enough to limit torsional deflection is all that is needed, and Honda, Ducati, BMW, etc., have it figured out. That is why the inboard swing arm bearing on the Super 10 is fine. In practice, torsional swingarm loads are quite low on the street. Forces are parallel to the vertical axis of the rear wheel, and the moment arm is very short (1/2 the tire width), so if you do the math, small loads. You just increase the diameter of the single side swingarm arm, and you have adequate strength and stiffness.
Back to Snakebitten's argument, attach a pipewrench to his broom handle, and THEN try to twist. The pipewrench is the swingarm axle. The longer the pipewrench, the less force i have to exert to react against that torque. The BMW is a long pipe wrench - the Super 10 is a shorter pipe wrench. Both react against torsion.
Having ridden old airhead BMWs for a long time, what inspired the Paralever was the relatively short swing arm used by BMW (and moto guzzi). Given their engine/transmission layout (not integrated, trans behind the engine), short swing arms were necessary for a bike to not handle like a barge. If you take the short swing arm, compound it with a cardan drive, and add horsepower and long-travel suspension, the rear rises with the application of engine torque. Moto Guzzi has their Compact Reactive Cardan Shaft Drive system, similar to the Paralever. You trade off swing arm jacking for more complexity in the drive shaft and swing arm.
If you look at the Super 10, the swing arm is very long (facilitated by the engine/transmission architecture, and by locating the swingarm bearing inboard of the driveshaft). The longer the swing arm, the less sensitive the bike is to swing arm jacking. Yamaha wisely went with long swing arm, only one universal joint, and no intermediate pivots in the swing arm. Does the job, reliable, and easy to maintain.
Where double-sided swing arms excel is when side loading (loads parallel to the rear wheel axle) exists - the axle clamped to the swing arm creates a very stiff structure. That's why you don't see a single-sided swingarm dirtbike. You don't see loading conditions like that on the street, so single-sided swing arms can be design to provide excellent performance under those conditions.
Tradeoffs. That's what makes engineering interesting.
The Single sided swingarm reacts against the swing arm axle at the two bearing points. On a BMW, those bearings are located outside of the driveshaft; on both side, those bearings are on the outside frame.
ON the Super 10, the swing arm bearings on the right side are in the outside frame on the right, but INBOARD of the drive shaft on the left side. This creates a smaller moment arm, increasing the forces on the bearings to react against the torsional force placed on the swing arm. If you think about how a rear tire handles torsional forces, single sided vs. double sided for this application makes very little difference. Making the cross section of the single side large enough to limit torsional deflection is all that is needed, and Honda, Ducati, BMW, etc., have it figured out. That is why the inboard swing arm bearing on the Super 10 is fine. In practice, torsional swingarm loads are quite low on the street. Forces are parallel to the vertical axis of the rear wheel, and the moment arm is very short (1/2 the tire width), so if you do the math, small loads. You just increase the diameter of the single side swingarm arm, and you have adequate strength and stiffness.
Back to Snakebitten's argument, attach a pipewrench to his broom handle, and THEN try to twist. The pipewrench is the swingarm axle. The longer the pipewrench, the less force i have to exert to react against that torque. The BMW is a long pipe wrench - the Super 10 is a shorter pipe wrench. Both react against torsion.
Having ridden old airhead BMWs for a long time, what inspired the Paralever was the relatively short swing arm used by BMW (and moto guzzi). Given their engine/transmission layout (not integrated, trans behind the engine), short swing arms were necessary for a bike to not handle like a barge. If you take the short swing arm, compound it with a cardan drive, and add horsepower and long-travel suspension, the rear rises with the application of engine torque. Moto Guzzi has their Compact Reactive Cardan Shaft Drive system, similar to the Paralever. You trade off swing arm jacking for more complexity in the drive shaft and swing arm.
If you look at the Super 10, the swing arm is very long (facilitated by the engine/transmission architecture, and by locating the swingarm bearing inboard of the driveshaft). The longer the swing arm, the less sensitive the bike is to swing arm jacking. Yamaha wisely went with long swing arm, only one universal joint, and no intermediate pivots in the swing arm. Does the job, reliable, and easy to maintain.
Where double-sided swing arms excel is when side loading (loads parallel to the rear wheel axle) exists - the axle clamped to the swing arm creates a very stiff structure. That's why you don't see a single-sided swingarm dirtbike. You don't see loading conditions like that on the street, so single-sided swing arms can be design to provide excellent performance under those conditions.
Tradeoffs. That's what makes engineering interesting.
blitz11
Well-Known Member
Good point. Sort of starting thinking about it, and became carried away.
I think that I addressed paralever vs. not (longer swing arm on the S-10 due to its engine architecture and location of swing arm bearings) and Snakebitten's discussion of single vs. double swing arms.
I think that I addressed paralever vs. not (longer swing arm on the S-10 due to its engine architecture and location of swing arm bearings) and Snakebitten's discussion of single vs. double swing arms.
Squibb said:
............. KENYou are correct about the bikes rising under acceleration and you really didn't have to be accelerating all that hard. BMWs from that era had long travel soft suspensions. They would also settle downward when closing the throttle. You (I) learned very quickly not to chop the throttle closed in a corner. This sometimes caused metal parts to get ground on the pavement. Stiffer aftermarket suspension components really helped control this rising and falling. I had several of these old R series air heads back then and loved everyone of them. Now with my S10, I have never really given it a second thought. I'm sure it happens, but it's not that noticeable.
Because like Squib wrote, BMW wanted plush suspension and to get it had long travel forks that would dive and flex. Paralever was their answer.
Mama Yama, Honda, and others didn't got past the long and soft diving suspension issues before BMW went to paralever so it wasn't an issue for them.
Mama Yama, Honda, and others didn't got past the long and soft diving suspension issues before BMW went to paralever so it wasn't an issue for them.
No reason to be sorry blitz11!
I don't even pretend to understand engineering terms like "torsion", and the well thought out explanation you provided.
But perhaps my barnyard analogy implied I did.
To be clear though, I wasn't arguing for or against the paralever, or whatever that thing is. I don't understand clearly how it works. (or other clever engineering that BMW or anyone else uses to make a single sided swingarm work)
But I WAS pointing out that my analogy made me believe that with "2 arms" (double sided swingarm) holding the broomstick (rear wheel axle, not swingarm pivot axle), it seems far less likely that either arm could be twisted, or broken, or cracked. (seen plenty of pictures of damaged BMW 1-arm swingarms)
And as oversimplified as the picture in my head might be, attaching that wheel to that single sided swingarm creates a very different load on the wheel bearing, compared to a conventional axle\bearing layout. Again, loads of GS "wheel bearing" stories.
Regardless, I still might be way off on what causes all the GS single sided swingarm problem. I sure couldn't show the math!
Still, I've never made it a secret, my lust for the GSA. But I'm 60. They're starting to run out of time. Lol
I don't even pretend to understand engineering terms like "torsion", and the well thought out explanation you provided.
But perhaps my barnyard analogy implied I did.
To be clear though, I wasn't arguing for or against the paralever, or whatever that thing is. I don't understand clearly how it works. (or other clever engineering that BMW or anyone else uses to make a single sided swingarm work)
But I WAS pointing out that my analogy made me believe that with "2 arms" (double sided swingarm) holding the broomstick (rear wheel axle, not swingarm pivot axle), it seems far less likely that either arm could be twisted, or broken, or cracked. (seen plenty of pictures of damaged BMW 1-arm swingarms)
And as oversimplified as the picture in my head might be, attaching that wheel to that single sided swingarm creates a very different load on the wheel bearing, compared to a conventional axle\bearing layout. Again, loads of GS "wheel bearing" stories.
Regardless, I still might be way off on what causes all the GS single sided swingarm problem. I sure couldn't show the math!
Still, I've never made it a secret, my lust for the GSA. But I'm 60. They're starting to run out of time. Lol
Cycledude
Well-Known Member
After riding Goldwings with single sided swing arm for almost 600,000 miles trouble free the dual sided swing arm on the Tenere seems outdated when it comes time to change tires, but in my opinion the Yamaha dual swing arm system is very well put together and there ain't nothing wrong with it.
2daMax
Active Member
I have never heard of the paralever until now. Guess I wasn't reading too many BMW articles. My understanding is that the purpose is to reduce the swingarm jack up effect which also can be achieved with a longer monolever when acceleration is applied or when presence of a torque from the wheels. It looks more complex and have more part$ involved. I couldn't feel I was being lifted up when on the S10 or feel mono altitude when test riding a GS. A lot of effort in the design for very little advantage gains IMO.
scott123007
Well-Known Member
It's winter in Malaysia too?
SilverBullet
Well-Known Member
I'm not an engineer and won't discuss the physics but I don't believe I've ever heard of a conventional swingarm failure on any big adventure bike. Let alone a catastrophic occurance such as this. Plenty more similar photos out there. And contrary to popular belief duct tape doesn't fix everything.
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