Gents,
I've been looking at images of, and reading about the different vendors and DIY braced swingarms and have a few thoughts and a few questions. I've read very little about the intent behind different designs, other than "stiffer is better". Is it? Or would some limited, remaining flex reduce strain on the main frame and swingarm pivot points?
For background, I'm not interested in extended swingarms, but interested in an optimal swingarm for spirited canyon-carving type riding (stock length, but improved). Looks are less important to me - function wins on this topic.
What I've noticed is that the approach to bracing the swingarm varies a lot between different vendors and DIY'ers.
Materials:
For tubing, I see round tubing in 1 inch OD up to 1.5inch OD tubing, others use boxed tubing. Wall thickness of the tubing can range from around .065 up to .1 inch thickness.. maybe more. Others have no idea what tubing they're using other than "it's free or cheap, let's use it!" (I'm really tempted by this approach BTW :biglaugh: ).
Questions I have here are: Why choose a certain diameter, and why choose a certain wall thickness/ gauge of tubing? At what point is extra thickness and weight actively working-AGAINST you by making the swingarm so heavy that handling and responsiveness to road conditions is compromised? Based on the limited chassis / motorcycle suspension theory I've ready, the ideal suspension is light and stiff (helping it to be responsive)
Bracing points:
Most all the braces follow the similar approach of a 180 deg bent tubing (or 2 pieces welded to comprise a 180 bend) with arms going either all the way to the ends of the swingarm ends, but some stop short of going the full length, and instead stop on both sides just before the pumpkin / final drive housing. Most braces I've seen have at least 3 attachment points (at ends of swingarm, and somewhere near the pivot area, typically the cross brace), and a few have 4, maybe 5 points of attachment. I assume more is better, but this involves more work, but importantly more weight. Is it best to brace it along the arms, cross brace, or along the main tube holding the bearings? Seems to me it'd be best to transfer the flexing forces as close to the pivot area as possible. True?
example:
and one where the cross brace is used as an attachment on a lengthened arm:
also:
(seems to be missing a connection to the cross brace or pivot area?)
Distance above swingarm / angle of brace:
Is there an optimal distance from the swingarm for the brace to be installed/welded? Should it run parralel, or increasingly away from the swingarm as it approaches the pivot area? Where are the main points of stress and main points of flex on the swingarm? I suppose some designs consider clearance with OEM exhaust. Too many questions, right?
Examples:
http://www.flickr.com/photos/44543013@N06/4960360594/
Boxing / gusset ideas:
Some braced swingarms have boxed in or gusseted that area between the pivot and the cross brace. Another design boxes in the outside, sides of the arms about 3-4inches from the pivot, along the arms. Is this over-kill?
Example:
Other reinforcement:
Necessary to weld in a section of 3in OD pipe inside the driveshaft entry point (from trans)? It's been mentioned in a few posts in the old tech-list/ mailing list I used to subscribe to.
Weight:
Curious if anyone has weighed their swingarm, and compared it to the weight of current day sport bike swingarms?
Or.... anything is better than nothing.. stop analyzing? :bang head:
Currently I think my preference is something like this, but with the right side brace going the length of the arm:
Thoughts? Opinions? Experiences good or bad?
Cheers! :cheers:
I've been looking at images of, and reading about the different vendors and DIY braced swingarms and have a few thoughts and a few questions. I've read very little about the intent behind different designs, other than "stiffer is better". Is it? Or would some limited, remaining flex reduce strain on the main frame and swingarm pivot points?
For background, I'm not interested in extended swingarms, but interested in an optimal swingarm for spirited canyon-carving type riding (stock length, but improved). Looks are less important to me - function wins on this topic.
What I've noticed is that the approach to bracing the swingarm varies a lot between different vendors and DIY'ers.
Materials:
For tubing, I see round tubing in 1 inch OD up to 1.5inch OD tubing, others use boxed tubing. Wall thickness of the tubing can range from around .065 up to .1 inch thickness.. maybe more. Others have no idea what tubing they're using other than "it's free or cheap, let's use it!" (I'm really tempted by this approach BTW :biglaugh: ).
Questions I have here are: Why choose a certain diameter, and why choose a certain wall thickness/ gauge of tubing? At what point is extra thickness and weight actively working-AGAINST you by making the swingarm so heavy that handling and responsiveness to road conditions is compromised? Based on the limited chassis / motorcycle suspension theory I've ready, the ideal suspension is light and stiff (helping it to be responsive)
Bracing points:
Most all the braces follow the similar approach of a 180 deg bent tubing (or 2 pieces welded to comprise a 180 bend) with arms going either all the way to the ends of the swingarm ends, but some stop short of going the full length, and instead stop on both sides just before the pumpkin / final drive housing. Most braces I've seen have at least 3 attachment points (at ends of swingarm, and somewhere near the pivot area, typically the cross brace), and a few have 4, maybe 5 points of attachment. I assume more is better, but this involves more work, but importantly more weight. Is it best to brace it along the arms, cross brace, or along the main tube holding the bearings? Seems to me it'd be best to transfer the flexing forces as close to the pivot area as possible. True?
example:
and one where the cross brace is used as an attachment on a lengthened arm:
also:
(seems to be missing a connection to the cross brace or pivot area?)
Distance above swingarm / angle of brace:
Is there an optimal distance from the swingarm for the brace to be installed/welded? Should it run parralel, or increasingly away from the swingarm as it approaches the pivot area? Where are the main points of stress and main points of flex on the swingarm? I suppose some designs consider clearance with OEM exhaust. Too many questions, right?
Examples:
Boxing / gusset ideas:
Some braced swingarms have boxed in or gusseted that area between the pivot and the cross brace. Another design boxes in the outside, sides of the arms about 3-4inches from the pivot, along the arms. Is this over-kill?
Example:
Other reinforcement:
Necessary to weld in a section of 3in OD pipe inside the driveshaft entry point (from trans)? It's been mentioned in a few posts in the old tech-list/ mailing list I used to subscribe to.
Weight:
Curious if anyone has weighed their swingarm, and compared it to the weight of current day sport bike swingarms?
Or.... anything is better than nothing.. stop analyzing? :bang head:
Currently I think my preference is something like this, but with the right side brace going the length of the arm:
Thoughts? Opinions? Experiences good or bad?
Cheers! :cheers:
