Something y'all may want to consider when experimenting with carrying stuff on your bike - mass centralisation. This has become popular with motorcycle manufacturers as a way of improving handling.The idea being to keep as much of the weight of the bike, near the centre of the vehicle as possible. Honda <http://en.wikipedia.org/wiki/Honda_CBR1000RR> and Buell <http://www.redline.co.za/Buell%20Firebolt%20XB12R.htm>for instance are both keen. When discussing load carrying on bicycles, people often talk about keeping the weight low to keep the bike stable, but a recent poster to this list referred to preferring the weight to be carried on his back so as not to compromise the handling of the bike. That's putting the weight HIGH up. Then there's is also the randoneur crowd who like the weight up on the front.
So I think there's more to this and it may be worth thinking about (and experimenting with) - if you want to preserve the handling of your bike, keep the heavy things you're carrying, near you. In a seat bag perhaps?
I think loading of the bicycle is depends on the geometry of the bicycle meaning, how much trail you have on the bicycle. A bicycle with little trail 44 to 40in favor more weight up front than in the back due to lower trail numbers resists more stearing inputs of the rider. In addition, with the weight up front, it falls with the movement of bicycle and does not lag behind the turning of the bicycle as if you had majority of the weight in the rear. Better handling of the bicycle when it favors this geometry. Keeping the weight lower on the bicycle creates stability to the bicycle by lowering the center of gravity. The geometry in the other direction meaning high trail favor rear geometry but you also get the affect of wagging the tail when peddling with rear heavy loads with high trail.
I am sure others here can make this alot clearer but I am going by memory. If you search online, look up Jan Heine and front loads and there will be a better explanation of why heavy front bicycles are better than heavy rear loaded bicycles.
L.
On Sun, Oct 30, 2011 at 9:21 PM, Alex Mazonowicz <a...@mazonowicz.com>wrote:
> Something y'all may want to consider when experimenting with carrying > stuff on your bike - mass centralisation. This has become popular with > motorcycle manufacturers as a way of improving handling. The idea being > to keep as much of the weight of the bike, near the centre of the vehicle > as possible. Honda <http://en.wikipedia.org/wiki/Honda_CBR1000RR> and > Buell <http://www.redline.co.za/Buell%20Firebolt%20XB12R.htm> for > instance are both keen. When discussing load carrying on bicycles, people > often talk about keeping the weight low to keep the bike stable, but a > recent poster to this list referred to preferring the weight to be carried > on his back so as not to compromise the handling of the bike. That's > putting the weight HIGH up. Then there's is also the randoneur crowd who > like the weight up on the front.
> So I think there's more to this and it may be worth thinking about (and > experimenting with) - if you want to preserve the handling of your bike, > keep the heavy things you're carrying, near you. In a seat bag perhaps?
> Alex
> -- > You received this message because you are subscribed to the Google Groups > "Bicycle Lifestyle" group. > To post to this group, send email to bicyclelifestyle@googlegroups.com. > To unsubscribe from this group, send email to > bicyclelifestyle+unsubscribe@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/bicyclelifestyle?hl=en.
Back in the early '80s, I read an article by Jim Blackburn about
weight distribution. At that time, most of us cycle tourists had a
great big set of panniers in the rear, and a heavy, high-mounted
handlebar bag in front. Blackburn found that putting some of the
weight in front panniers greatly improved handling (stability), which
was certainly my experience.
Perhaps less well-remembered is an experiment he did with low-rider
rear racks. To lower the center of gravity (as in front low-riders),
he built rear racks that carried the bags much lower. But to maintain
clearance, he had to move the racks backward, away from the rider's
heels. This put much of the weight behind the rear axle. The center
of gravity went down, but the handling was awful. The weight in the
back had too much leverage in that position. That's probably why you
don't see many rear racks that carry the weight that low. (I realize
there are racks that lower the weight a bit, like some Tubus models.)
I have no idea whether moving the weight further forward than the rear
axle would help. As a practical matter, space in the center of a bike
is rather limited, though one could put some heavy items, like tools,
in a frame bag.
Longtail (xtracycle, big dummy) riders get to perform these experiments all the time. Behind the axle is not good. Ahead of the rear axle is just fine. Lower is better.
First time I carried one of my kids on the back, he decided to slide fore-and-aft (again and again) on the deck. Handling went from just fine, to astonishingly bad, and back again, over and over.
> Perhaps less well-remembered is an experiment he did with low-rider > rear racks. To lower the center of gravity (as in front low-riders), > he built rear racks that carried the bags much lower. But to maintain > clearance, he had to move the racks backward, away from the rider's > heels. This put much of the weight behind the rear axle. The center > of gravity went down, but the handling was awful. The weight in the > back had too much leverage in that position. That's probably why you > don't see many rear racks that carry the weight that low. (I realize > there are racks that lower the weight a bit, like some Tubus models.) > I have no idea whether moving the weight further forward than the rear > axle would help. As a practical matter, space in the center of a bike > is rather limited, though one could put some heavy items, like tools, > in a frame bag.
For best handling; you want the center of mass within the axles - ideally close to centered, and to minimize the polar moment of inertia - meaning keep the mass as close to the center of gravity as possible.
On a bicycle or motorcycle, height of the center of gravity is not as critical as say a car, because our vehicles lean into curves.
----- Original Message ----- From: "David Chase" <dr2ch...@gmail.com> To: bicyclelifestyle@googlegroups.com Sent: Monday, October 31, 2011 11:32:59 AM Subject: Re: {BL} Re: Carrying stuff on a bicycle
Longtail (xtracycle, big dummy) riders get to perform these experiments all the time. Behind the axle is not good. Ahead of the rear axle is just fine. Lower is better.
First time I carried one of my kids on the back, he decided to slide fore-and-aft (again and again) on the deck. Handling went from just fine, to astonishingly bad, and back again, over and over.
David
On 2011-10-30, at 10:59 PM, Jon wrote: > Perhaps less well-remembered is an experiment he did with low-rider > rear racks. To lower the center of gravity (as in front low-riders), > he built rear racks that carried the bags much lower. But to maintain > clearance, he had to move the racks backward, away from the rider's > heels. This put much of the weight behind the rear axle. The center > of gravity went down, but the handling was awful. The weight in the > back had too much leverage in that position. That's probably why you > don't see many rear racks that carry the weight that low. (I realize > there are racks that lower the weight a bit, like some Tubus models.)
> I have no idea whether moving the weight further forward than the rear > axle would help. As a practical matter, space in the center of a bike > is rather limited, though one could put some heavy items, like tools, > in a frame bag.
-- You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. To post to this group, send email to bicyclelifestyle@googlegroups.com. To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/bicyclelifestyle?hl=en.
On Mon, Oct 31, 2011 at 12:04 AM, <nfmi...@comcast.net> wrote: > For best handling; you want the center of mass within the axles - > ideally close to centered, and to minimize the polar moment of inertia - > meaning keep the mass as close to the center of gravity as possible.
> On a bicycle or motorcycle, height of the center of gravity is not as > critical as say a car, because our vehicles lean into curves.
> Nigel > (yes I am a Mechanical Design Engineer)
> ------------------------------ > *From: *"David Chase" <dr2ch...@gmail.com> > *To: *bicyclelifestyle@googlegroups.com > *Sent: *Monday, October 31, 2011 11:32:59 AM > *Subject: *Re: {BL} Re: Carrying stuff on a bicycle
> Longtail (xtracycle, big dummy) riders get to perform these experiments > all the time. > Behind the axle is not good. Ahead of the rear axle is just fine. Lower > is better.
> First time I carried one of my kids on the back, he decided to slide > fore-and-aft (again and again) on the deck. > Handling went from just fine, to astonishingly bad, and back again, over > and over.
> David
> On 2011-10-30, at 10:59 PM, Jon wrote: > > Perhaps less well-remembered is an experiment he did with low-rider > > rear racks. To lower the center of gravity (as in front low-riders), > > he built rear racks that carried the bags much lower. But to maintain > > clearance, he had to move the racks backward, away from the rider's > > heels. This put much of the weight behind the rear axle. The center > > of gravity went down, but the handling was awful. The weight in the > > back had too much leverage in that position. That's probably why you > > don't see many rear racks that carry the weight that low. (I realize > > there are racks that lower the weight a bit, like some Tubus models.)
> > I have no idea whether moving the weight further forward than the rear > > axle would help. As a practical matter, space in the center of a bike > > is rather limited, though one could put some heavy items, like tools, > > in a frame bag.
> -- > You received this message because you are subscribed to the Google Groups > "Bicycle Lifestyle" group. > To post to this group, send email to bicyclelifestyle@googlegroups.com. > To unsubscribe from this group, send email to > bicyclelifestyle+unsubscribe@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/bicyclelifestyle?hl=en.
> -- > You received this message because you are subscribed to the Google Groups > "Bicycle Lifestyle" group. > To post to this group, send email to bicyclelifestyle@googlegroups.com. > To unsubscribe from this group, send email to > bicyclelifestyle+unsubscribe@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/bicyclelifestyle?hl=en.
I would think that you still want to keep the mass as low as
practicable on the bike. If you imagine having a 50 foot pole
attached to the frame so it is pointing directly up over the cyclist
and with your saddlebag attached at the top, then it's true that as
you lean into turns the saddlebag's mass still presses down "in line"
through the frame into the wheels. But getting that pole to lean is
going to take longer than if the saddlebag is attached to the saddle.
So handling will be a little less lively. (Plus the pole keeps
getting caught on electric lines but that is a different problem.)
> For best handling; you want the center of mass within the axles - ideally close to centered, and to minimize the polar moment of inertia - meaning keep the mass as close to the center of gravity as possible.
> On a bicycle or motorcycle, height of the center of gravity is not as critical as say a car, because our vehicles lean into curves.
> Nigel
> (yes I am a Mechanical Design Engineer)
> ----- Original Message -----
> From: "David Chase" <dr2ch...@gmail.com>
> To: bicyclelifestyle@googlegroups.com
> Sent: Monday, October 31, 2011 11:32:59 AM
> Subject: Re: {BL} Re: Carrying stuff on a bicycle
> Longtail (xtracycle, big dummy) riders get to perform these experiments all the time.
> Behind the axle is not good. Ahead of the rear axle is just fine. Lower is better.
> First time I carried one of my kids on the back, he decided to slide fore-and-aft (again and again) on the deck.
> Handling went from just fine, to astonishingly bad, and back again, over and over.
> David
> On 2011-10-30, at 10:59 PM, Jon wrote:
> > Perhaps less well-remembered is an experiment he did with low-rider
> > rear racks. To lower the center of gravity (as in front low-riders),
> > he built rear racks that carried the bags much lower. But to maintain
> > clearance, he had to move the racks backward, away from the rider's
> > heels. This put much of the weight behind the rear axle. The center
> > of gravity went down, but the handling was awful. The weight in the
> > back had too much leverage in that position. That's probably why you
> > don't see many rear racks that carry the weight that low. (I realize
> > there are racks that lower the weight a bit, like some Tubus models.)
> > I have no idea whether moving the weight further forward than the rear
> > axle would help. As a practical matter, space in the center of a bike
> > is rather limited, though one could put some heavy items, like tools,
> > in a frame bag.
> --
> You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group.
> To post to this group, send email to bicyclelifestyle@googlegroups.com.
> To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com.
> For more options, visit this group athttp://groups.google.com/group/bicyclelifestyle?hl=en.
> For best handling; you want the center of mass within the axles - ideally close to centered, and to minimize the polar moment of inertia - meaning keep the mass as close to the center of gravity as possible.
> On a bicycle or motorcycle, height of the center of gravity is not as critical as say a car, because our vehicles lean into curves.
I think you have it backwards, you want the Cg as low as possible, so
when you lean the bike over, the Cg location changes as little as
possible per given degree of bank angle. The further (and faster) the
Cg moves, the more effort it takes to start and stop the movement of
the mass at the Cg.
As far as location fore/aft, that is less clear, just where is the
center of rotation when a bike arcs into a turn, at the frame headset,
or midway between the contact patches? Could be different places
during the turn depending on whether the handlebars are cranked to
initiate the turn or straight as the bike rolls through a turn.
> As far as location fore/aft, that is less clear, just where is the > center of rotation when a bike arcs into a turn, at the frame headset, > or midway between the contact patches? Could be different places > during the turn depending on whether the handlebars are cranked to > initiate the turn or straight as the bike rolls through a turn.
At least on a cargo bike (where a heavy load makes subtle effects not-so-subtle) it is more a matter of oscillation. That is, not that it is hard to turn by itself, but that the bike can have a decaying vibration (in the .5-2 Hz range) which if large enough makes your steering kinda wonky, and this can appear even when riding "straight" (since we all wobble a little). Net weight behind the axle seems to be especially good at provoking those.
Obviously a "normal" (shorter, more lightly loaded) bicycle would not see such gross effects, but I suspect the subtle version of this is one thing people perceive as "bad handling".
Interestingly, you can automatically adapt; one of my worst loads (a load of firewood, some of it long-ish and sticking out the back) had me unsure if I could stay on a 12-foot wide trail at first, but within a hundred yards or so I was comfortably in a 6-foot lane, and at a half mile I was steering a straight line. None of this with a conscious micromanaged effort, other than a desire to not weave.
David Chase wrote: > Net weight behind the axle seems to be especially good at provoking those > [oscillations].
For a while I used my go-fast bike for commuting. I used P-clamps to fasten the rack to the seat stays, with a single strap to the brake bolt. To solve heel strike, the panniers had to ride as far back as mechanically possible on the side rails.
With any significant weight back there, it was almost uncontrollable with my normal out of the saddle style. I had to adopt a very stable starting and pedaling style, not tossing the bike side-to-side at all, very straight up and down. If you've ever captained a tandem, it's almost exactly the same thing.
Actually about 30 years ago, there was a lot of research done on this subject for racing motorcycles (close enough to bikes). Within a reasonable range of c.g. vertical location (say under 4 feet); the vertical location of the c.g. is a 2nd or 3rd order effect, while location a long the center line between the axles is a 1st order effect.
Focus on getting the mass between the axles, and as close to center as possible.
Next; reduce the polar moment of inertia.
And lastly height.
As usual; you can only have two of the three........
----- Original Message ----- From: "NickBull" <nick.bike.b...@gmail.com> To: "Bicycle Lifestyle" <bicyclelifestyle@googlegroups.com> Sent: Monday, October 31, 2011 11:47:34 PM Subject: Re: {BL} Re: Carrying stuff on a bicycle
Nigel,
I would think that you still want to keep the mass as low as practicable on the bike. If you imagine having a 50 foot pole attached to the frame so it is pointing directly up over the cyclist and with your saddlebag attached at the top, then it's true that as you lean into turns the saddlebag's mass still presses down "in line" through the frame into the wheels. But getting that pole to lean is going to take longer than if the saddlebag is attached to the saddle. So handling will be a little less lively. (Plus the pole keeps getting caught on electric lines but that is a different problem.)
Nick
On Oct 31, 12:04 am, nfmi...@comcast.net wrote: > For best handling; you want the center of mass within the axles - ideally close to centered, and to minimize the polar moment of inertia - meaning keep the mass as close to the center of gravity as possible.
> On a bicycle or motorcycle, height of the center of gravity is not as critical as say a car, because our vehicles lean into curves.
> Nigel > (yes I am a Mechanical Design Engineer)
> ----- Original Message ----- > From: "David Chase" <dr2ch...@gmail.com> > To: bicyclelifestyle@googlegroups.com > Sent: Monday, October 31, 2011 11:32:59 AM > Subject: Re: {BL} Re: Carrying stuff on a bicycle
> Longtail (xtracycle, big dummy) riders get to perform these experiments all the time. > Behind the axle is not good. Ahead of the rear axle is just fine. Lower is better.
> First time I carried one of my kids on the back, he decided to slide fore-and-aft (again and again) on the deck. > Handling went from just fine, to astonishingly bad, and back again, over and over.
> David
> On 2011-10-30, at 10:59 PM, Jon wrote: > > Perhaps less well-remembered is an experiment he did with low-rider > > rear racks. To lower the center of gravity (as in front low-riders), > > he built rear racks that carried the bags much lower. But to maintain > > clearance, he had to move the racks backward, away from the rider's > > heels. This put much of the weight behind the rear axle. The center > > of gravity went down, but the handling was awful. The weight in the > > back had too much leverage in that position. That's probably why you > > don't see many rear racks that carry the weight that low. (I realize > > there are racks that lower the weight a bit, like some Tubus models.)
> > I have no idea whether moving the weight further forward than the rear > > axle would help. As a practical matter, space in the center of a bike > > is rather limited, though one could put some heavy items, like tools, > > in a frame bag.
> -- > You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. > To post to this group, send email to bicyclelifestyle@googlegroups.com. > To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com. > For more options, visit this group athttp://groups.google.com/group/bicyclelifestyle?hl=en.
-- You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. To post to this group, send email to bicyclelifestyle@googlegroups.com. To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/bicyclelifestyle?hl=en.
Would you not be kicking your panniers if you got your bags between the axles of a bike? Also, can you explain what is the 2nd and 3rd order effects you speak of? Just curious.
On Mon, Oct 31, 2011 at 7:04 PM, <nfmi...@comcast.net> wrote: > Actually about 30 years ago, there was a lot of research done on this > subject for racing motorcycles (close enough to bikes). Within a > reasonable range of c.g. vertical location (say under 4 feet); the vertical > location of the c.g. is a 2nd or 3rd order effect, while location a long > the center line between the axles is a 1st order effect.
> Focus on getting the mass between the axles, and as close to center as > possible.
> Next; reduce the polar moment of inertia.
> And lastly height.
> As usual; you can only have two of the three........
> *Subject: *Re: {BL} Re: Carrying stuff on a bicycle
> Nigel,
> I would think that you still want to keep the mass as low as > practicable on the bike. If you imagine having a 50 foot pole > attached to the frame so it is pointing directly up over the cyclist > and with your saddlebag attached at the top, then it's true that as > you lean into turns the saddlebag's mass still presses down "in line" > through the frame into the wheels. But getting that pole to lean is > going to take longer than if the saddlebag is attached to the saddle. > So handling will be a little less lively. (Plus the pole keeps > getting caught on electric lines but that is a different problem.)
> Nick
> On Oct 31, 12:04 am, nfmi...@comcast.net wrote: > > For best handling; you want the center of mass within the axles - > ideally close to centered, and to minimize the polar moment of inertia - > meaning keep the mass as close to the center of gravity as possible.
> > On a bicycle or motorcycle, height of the center of gravity is not as > critical as say a car, because our vehicles lean into curves.
> > Nigel > > (yes I am a Mechanical Design Engineer)
> > ----- Original Message ----- > > From: "David Chase" <dr2ch...@gmail.com> > > To: bicyclelifestyle@googlegroups.com > > Sent: Monday, October 31, 2011 11:32:59 AM > > Subject: Re: {BL} Re: Carrying stuff on a bicycle
> > Longtail (xtracycle, big dummy) riders get to perform these experiments > all the time. > > Behind the axle is not good. Ahead of the rear axle is just fine. Lower > is better.
> > First time I carried one of my kids on the back, he decided to slide > fore-and-aft (again and again) on the deck. > > Handling went from just fine, to astonishingly bad, and back again, over > and over.
> > David
> > On 2011-10-30, at 10:59 PM, Jon wrote: > > > Perhaps less well-remembered is an experiment he did with low-rider > > > rear racks. To lower the center of gravity (as in front low-riders), > > > he built rear racks that carried the bags much lower. But to maintain > > > clearance, he had to move the racks backward, away from the rider's > > > heels. This put much of the weight behind the rear axle. The center > > > of gravity went down, but the handling was awful. The weight in the > > > back had too much leverage in that position. That's probably why you > > > don't see many rear racks that carry the weight that low. (I realize > > > there are racks that lower the weight a bit, like some Tubus models.)
> > > I have no idea whether moving the weight further forward than the rear > > > axle would help. As a practical matter, space in the center of a bike > > > is rather limited, though one could put some heavy items, like tools, > > > in a frame bag.
> > -- > > You received this message because you are subscribed to the Google > Groups "Bicycle Lifestyle" group. > > To post to this group, send email to bicyclelifestyle@googlegroups.com. > > To unsubscribe from this group, send email to > bicyclelifestyle+unsubscribe@googlegroups.com. > > For more options, visit this group athttp:// > groups.google.com/group/bicyclelifestyle?hl=en.
> -- > You received this message because you are subscribed to the Google Groups > "Bicycle Lifestyle" group. > To post to this group, send email to bicyclelifestyle@googlegroups.com. > To unsubscribe from this group, send email to > bicyclelifestyle+unsubscribe@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/bicyclelifestyle?hl=en.
> -- > You received this message because you are subscribed to the Google Groups > "Bicycle Lifestyle" group. > To post to this group, send email to bicyclelifestyle@googlegroups.com. > To unsubscribe from this group, send email to > bicyclelifestyle+unsubscribe@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/bicyclelifestyle?hl=en.
this is on of the reasons why touring bicycles tend to have longer chainstays -- it moves the rear axle back so more of the weight will be forward of the axle. I have loaded panniers with heavy stuff in the back of the back bags and it REALLY makes a difference. I was popping wheelies on any hill over about 4% And if I tried to lift it over a curb while walking it or trying to lock it up, it would almost flip itself once the front wheel was above a certain height! The load was better balanced the next day, believe me. That was before I had a front rack, too, so there was NOTHING to help counter balance the weight.
----- Original Message ----- From: Lee Legrand To: bicyclelifestyle@googlegroups.com Sent: Monday, October 31, 2011 8:54 PM Subject: Re: {BL} Re: Carrying stuff on a bicycle
Would you not be kicking your panniers if you got your bags between the axles of a bike? Also, can you explain what is the 2nd and 3rd order effects you speak of? Just curious.
On Mon, Oct 31, 2011 at 7:04 PM, <nfmi...@comcast.net> wrote:
Actually about 30 years ago, there was a lot of research done on this subject for racing motorcycles (close enough to bikes). Within a reasonable range of c.g. vertical location (say under 4 feet); the vertical location of the c.g. is a 2nd or 3rd order effect, while location a long the center line between the axles is a 1st order effect.
Focus on getting the mass between the axles, and as close to center as possible.
Next; reduce the polar moment of inertia.
And lastly height.
As usual; you can only have two of the three........
Nigel
--------------------------------------------------------------------------- - From: "NickBull" <nick.bike.b...@gmail.com> To: "Bicycle Lifestyle" <bicyclelifestyle@googlegroups.com> Sent: Monday, October 31, 2011 11:47:34 PM
Subject: Re: {BL} Re: Carrying stuff on a bicycle
Nigel,
I would think that you still want to keep the mass as low as practicable on the bike. If you imagine having a 50 foot pole attached to the frame so it is pointing directly up over the cyclist and with your saddlebag attached at the top, then it's true that as you lean into turns the saddlebag's mass still presses down "in line" through the frame into the wheels. But getting that pole to lean is going to take longer than if the saddlebag is attached to the saddle. So handling will be a little less lively. (Plus the pole keeps getting caught on electric lines but that is a different problem.)
Nick
On Oct 31, 12:04 am, nfmi...@comcast.net wrote: > For best handling; you want the center of mass within the axles - ideally close to centered, and to minimize the polar moment of inertia - meaning keep the mass as close to the center of gravity as possible.
> On a bicycle or motorcycle, height of the center of gravity is not as critical as say a car, because our vehicles lean into curves.
> Nigel > (yes I am a Mechanical Design Engineer)
> ----- Original Message ----- > From: "David Chase" <dr2ch...@gmail.com> > To: bicyclelifestyle@googlegroups.com > Sent: Monday, October 31, 2011 11:32:59 AM > Subject: Re: {BL} Re: Carrying stuff on a bicycle
> Longtail (xtracycle, big dummy) riders get to perform these experiments all the time. > Behind the axle is not good. Ahead of the rear axle is just fine. Lower is better.
> First time I carried one of my kids on the back, he decided to slide fore-and-aft (again and again) on the deck. > Handling went from just fine, to astonishingly bad, and back again, over and over.
> David
> On 2011-10-30, at 10:59 PM, Jon wrote: > > Perhaps less well-remembered is an experiment he did with low-rider > > rear racks. To lower the center of gravity (as in front low-riders), > > he built rear racks that carried the bags much lower. But to maintain > > clearance, he had to move the racks backward, away from the rider's > > heels. This put much of the weight behind the rear axle. The center > > of gravity went down, but the handling was awful. The weight in the > > back had too much leverage in that position. That's probably why you > > don't see many rear racks that carry the weight that low. (I realize > > there are racks that lower the weight a bit, like some Tubus models.)
> > I have no idea whether moving the weight further forward than the rear > > axle would help. As a practical matter, space in the center of a bike > > is rather limited, though one could put some heavy items, like tools, > > in a frame bag.
> -- > You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. > To post to this group, send email to bicyclelifestyle@googlegroups.com. > To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com. > For more options, visit this group athttp://groups.google.com/group/bicyclelifestyle?hl=en.
-- You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. To post to this group, send email to bicyclelifestyle@googlegroups.com. To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/bicyclelifestyle?hl=en.
-- You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. To post to this group, send email to bicyclelifestyle@googlegroups.com. To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/bicyclelifestyle?hl=en.
-- You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. To post to this group, send email to bicyclelifestyle@googlegroups.com. To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/bicyclelifestyle?hl=en.
A 1st order effect is one that covers the vast majority of the thing of interest. In this case, bicycle handling is the thing of interest. One of the 1st order effects is location of the center of mass (c.g) with respect to the axles.
A 2nd order effect is on that has some noticeable effect on the thing of interest, but is overwhelmed by the 1st order effect if the 1st order effect is far from ideal.
A 3rd order effect has a similar relationship to the 2nd and the 2nd has to the 1st.
In practical terms - if you don't have the center of mass close to the center of the space between the axles and the polar moment of inertia to a reasonable low level, the height of the center of mass is of no practical importance.
----- Original Message ----- From: "Lee Legrand" <krm2...@gmail.com> To: bicyclelifestyle@googlegroups.com Sent: Tuesday, November 1, 2011 8:54:24 AM Subject: Re: {BL} Re: Carrying stuff on a bicycle
Would you not be kicking your panniers if you got your bags between the axles of a bike? Also, can you explain what is the 2nd and 3rd order effects you speak of? Just curious.
On Mon, Oct 31, 2011 at 7:04 PM, < nfmi...@comcast.net > wrote:
Actually about 30 years ago, there was a lot of research done on this subject for racing motorcycles (close enough to bikes). Within a reasonable range of c.g. vertical location (say under 4 feet); the vertical location of the c.g. is a 2nd or 3rd order effect, while location a long the center line between the axles is a 1st order effect.
Focus on getting the mass between the axles, and as close to center as possible.
Next; reduce the polar moment of inertia.
And lastly height.
As usual; you can only have two of the three........
Nigel
From: "NickBull" < nick.bike.b...@gmail.com > To: "Bicycle Lifestyle" < bicyclelifestyle@googlegroups.com > Sent: Monday, October 31, 2011 11:47:34 PM
Subject: Re: {BL} Re: Carrying stuff on a bicycle
Nigel,
I would think that you still want to keep the mass as low as practicable on the bike. If you imagine having a 50 foot pole attached to the frame so it is pointing directly up over the cyclist and with your saddlebag attached at the top, then it's true that as you lean into turns the saddlebag's mass still presses down "in line" through the frame into the wheels. But getting that pole to lean is going to take longer than if the saddlebag is attached to the saddle. So handling will be a little less lively. (Plus the pole keeps getting caught on electric lines but that is a different problem.)
Nick
On Oct 31, 12:04 am, nfmi...@comcast.net wrote: > For best handling; you want the center of mass within the axles - ideally close to centered, and to minimize the polar moment of inertia - meaning keep the mass as close to the center of gravity as possible.
> On a bicycle or motorcycle, height of the center of gravity is not as critical as say a car, because our vehicles lean into curves.
> Nigel > (yes I am a Mechanical Design Engineer)
> ----- Original Message ----- > From: "David Chase" < dr2ch...@gmail.com > > To: bicyclelifestyle@googlegroups.com > Sent: Monday, October 31, 2011 11:32:59 AM > Subject: Re: {BL} Re: Carrying stuff on a bicycle
> Longtail (xtracycle, big dummy) riders get to perform these experiments all the time. > Behind the axle is not good. Ahead of the rear axle is just fine. Lower is better.
> First time I carried one of my kids on the back, he decided to slide fore-and-aft (again and again) on the deck. > Handling went from just fine, to astonishingly bad, and back again, over and over.
> David
> On 2011-10-30, at 10:59 PM, Jon wrote: > > Perhaps less well-remembered is an experiment he did with low-rider > > rear racks. To lower the center of gravity (as in front low-riders), > > he built rear racks that carried the bags much lower. But to maintain > > clearance, he had to move the racks backward, away from the rider's > > heels. This put much of the weight behind the rear axle. The center > > of gravity went down, but the handling was awful. The weight in the > > back had too much leverage in that position. That's probably why you > > don't see many rear racks that carry the weight that low. (I realize > > there are racks that lower the weight a bit, like some Tubus models.)
> > I have no idea whether moving the weight further forward than the rear > > axle would help. As a practical matter, space in the center of a bike > > is rather limited, though one could put some heavy items, like tools, > > in a frame bag.
> -- > You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. > To post to this group, send email to bicyclelifestyle@googlegroups.com . > To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com . > For more options, visit this group athttp:// groups.google.com/group/bicyclelifestyle?hl=en .
-- You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. To post to this group, send email to bicyclelifestyle@googlegroups.com . To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com . For more options, visit this group at http://groups.google.com/group/bicyclelifestyle?hl=en .
-- You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. To post to this group, send email to bicyclelifestyle@googlegroups.com . To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com . For more options, visit this group at http://groups.google.com/group/bicyclelifestyle?hl=en .
-- You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. To post to this group, send email to bicyclelifestyle@googlegroups.com. To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/bicyclelifestyle?hl=en.
I have not see a good design for a frame bag to fit in the main triangle - but that would be the ideal location for the most dense cargo (tools, water, etc). The width is a bit of a challenge, and it would have to provide water bottle mounts. The other challenge is the differences between various bikes.
----- Original Message ----- From: "Larry Parker" <LParker_0...@fuse.net> To: bicyclelifestyle@googlegroups.com Sent: Tuesday, November 1, 2011 9:06:22 AM Subject: Re: {BL} Re: Carrying stuff on a bicycle
this is on of the reasons why touring bicycles tend to have longer chainstays -- it moves the rear axle back so more of the weight will be forward of the axle. I have loaded panniers with heavy stuff in the back of the back bags and it REALLY makes a difference. I was popping wheelies on any hill over about 4% And if I tried to lift it over a curb while walking it or trying to lock it up, it would almost flip itself once the front wheel was above a certain height! The load was better balanced the next day, believe me. That was before I had a front rack, too, so there was NOTHING to help counter balance the weight.
Larry
----- Original Message ----- From: Lee Legrand To: bicyclelifestyle@googlegroups.com Sent: Monday, October 31, 2011 8:54 PM Subject: Re: {BL} Re: Carrying stuff on a bicycle
Would you not be kicking your panniers if you got your bags between the axles of a bike? Also, can you explain what is the 2nd and 3rd order effects you speak of? Just curious.
On Mon, Oct 31, 2011 at 7:04 PM, < nfmi...@comcast.net > wrote:
<blockquote>
Actually about 30 years ago, there was a lot of research done on this subject for racing motorcycles (close enough to bikes). Within a reasonable range of c.g. vertical location (say under 4 feet); the vertical location of the c.g. is a 2nd or 3rd order effect, while location a long the center line between the axles is a 1st order effect.
Focus on getting the mass between the axles, and as close to center as possible.
Next; reduce the polar moment of inertia.
And lastly height.
As usual; you can only have two of the three........
Nigel
From: "NickBull" < nick.bike.b...@gmail.com > To: "Bicycle Lifestyle" < bicyclelifestyle@googlegroups.com > Sent: Monday, October 31, 2011 11:47:34 PM
Subject: Re: {BL} Re: Carrying stuff on a bicycle
Nigel,
I would think that you still want to keep the mass as low as practicable on the bike. If you imagine having a 50 foot pole attached to the frame so it is pointing directly up over the cyclist and with your saddlebag attached at the top, then it's true that as you lean into turns the saddlebag's mass still presses down "in line" through the frame into the wheels. But getting that pole to lean is going to take longer than if the saddlebag is attached to the saddle. So handling will be a little less lively. (Plus the pole keeps getting caught on electric lines but that is a different problem.)
Nick
On Oct 31, 12:04 am, nfmi...@comcast.net wrote: > For best handling; you want the center of mass within the axles - ideally close to centered, and to minimize the polar moment of inertia - meaning keep the mass as close to the center of gravity as possible.
> On a bicycle or motorcycle, height of the center of gravity is not as critical as say a car, because our vehicles lean into curves.
> Nigel > (yes I am a Mechanical Design Engineer)
> ----- Original Message ----- > From: "David Chase" < dr2ch...@gmail.com > > To: bicyclelifestyle@googlegroups.com > Sent: Monday, October 31, 2011 11:32:59 AM > Subject: Re: {BL} Re: Carrying stuff on a bicycle
> Longtail (xtracycle, big dummy) riders get to perform these experiments all the time. > Behind the axle is not good. Ahead of the rear axle is just fine. Lower is better.
> First time I carried one of my kids on the back, he decided to slide fore-and-aft (again and again) on the deck. > Handling went from just fine, to astonishingly bad, and back again, over and over.
> David
> On 2011-10-30, at 10:59 PM, Jon wrote: > > Perhaps less well-remembered is an experiment he did with low-rider > > rear racks. To lower the center of gravity (as in front low-riders), > > he built rear racks that carried the bags much lower. But to maintain > > clearance, he had to move the racks backward, away from the rider's > > heels. This put much of the weight behind the rear axle. The center > > of gravity went down, but the handling was awful. The weight in the > > back had too much leverage in that position. That's probably why you > > don't see many rear racks that carry the weight that low. (I realize > > there are racks that lower the weight a bit, like some Tubus models.)
> > I have no idea whether moving the weight further forward than the rear > > axle would help. As a practical matter, space in the center of a bike > > is rather limited, though one could put some heavy items, like tools, > > in a frame bag.
> -- > You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. > To post to this group, send email to bicyclelifestyle@googlegroups.com . > To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com . > For more options, visit this group athttp:// groups.google.com/group/bicyclelifestyle?hl=en .
-- You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. To post to this group, send email to bicyclelifestyle@googlegroups.com . To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com . For more options, visit this group at http://groups.google.com/group/bicyclelifestyle?hl=en .
-- You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. To post to this group, send email to bicyclelifestyle@googlegroups.com . To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com . For more options, visit this group at http://groups.google.com/group/bicyclelifestyle?hl=en .
-- You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. To post to this group, send email to bicyclelifestyle@googlegroups.com. To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/bicyclelifestyle?hl=en.
</blockquote>
-- You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. To post to this group, send email to bicyclelifestyle@googlegroups.com. To unsubscribe from this group, send email to bicyclelifestyle+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/bicyclelifestyle?hl=en.
David's kid provided a great experiment to prove the point that Nigel
made.
I recall that Blackburn said that while lowrider racks were better
than standard front racks, the difference was small. That also
supports the point that the height of the load has a modest effect
compared to the fore-aft distribution.
I remembered where I saw a rear low-rider. Nitto makes a low-rider
attachment for rear racks. Not something I want to try.
Jon
On Oct 30, 8:32 pm, David Chase <dr2ch...@gmail.com> wrote:
> Longtail (xtracycle, big dummy) riders get to perform these experiments all the time.
> Behind the axle is not good. Ahead of the rear axle is just fine. Lower is better.
> First time I carried one of my kids on the back, he decided to slide fore-and-aft (again and again) on the deck.
> Handling went from just fine, to astonishingly bad, and back again, over and over.
> I have not see a good design for a frame bag to fit in the main triangle - but > that would be the ideal location for the most dense cargo (tools, water, etc). > The width is a bit of a challenge, and it would have to provide water bottle > mounts. The other challenge is the differences between various bikes.
I just bought one. I'm having to make adjustments for the tubing but it took 100 ozs of water, about 6-7 pounds with pack, off my back. I bought a revelate design bag https://www.revelatedesigns.com/index.cfm?fuseaction=store.catalog&Ca... and outfitted it with a camelback bladder. I'm still working through all the technical details before I post on my blog. So far I'm liking it.
I had some email correspondence with Eric at Revelate and he was quite responsive.
>> I have not see a good design for a frame bag to fit in the main triangle - but >> that would be the ideal location for the most dense cargo (tools, water, etc). >> The width is a bit of a challenge, and it would have to provide water bottle >> mounts. The other challenge is the differences between various bikes.
> I just bought one. I'm having to make adjustments for the tubing but it took > 100 ozs of water, about 6-7 pounds with pack, off my back. I bought a revelate > design bag > https://www.revelatedesigns.com/index.cfm?fuseaction=store.catalog&Ca... > and outfitted it with a camelback bladder. I'm still working through all the > technical details before I post on my blog. So far I'm liking it.
> I had some email correspondence with Eric at Revelate and he was quite > responsive.
I had a frame bag for a time, it didn't work for me because I couldn't find anywhere else for water bottles. Also, 21in frames don't give as much space as 25in. I did try rolling the bivvy bag round the top tube for a weekend camping with a saddlebag, but my knees brushed it while pedalling and it drove me nuts. -- Keith Ayres Oxfordshire, UK Thorn Raven, Argos, Trevor Jarvis Flying Gate
> Actually about 30 years ago, there was a lot of research done on this subject for
> racing motorcycles (close enough to bikes).
Maybe a racing motorcycle is akin to how you ride a bike, but it
certainly isn't how I ride a bicycle. Modeling a bicycle on any
bicycle would be closer, and modeling a touring bike on a touring bike
would be even closer still.
As the guy hauling the firewood posted, you can adapt to pretty much
anything, and any particulars are dependent on the bike's geometry and
personal preference.
Just because you can adapt to pretty much anything, it does not necessarily mean the bicycle is well designed for purpose of its use. For example, if were a pizza delivery guy that delivery pizza on a bicycle. You could probable do the job with a track bike, a racing bike (assuming fender mounts are there) and a porteur bicycle. You could adapt to how the all three bicycle handle stacks of pizza but would you say they are all equal or would pizza delivery be better on the porteur.
On Tue, Nov 1, 2011 at 12:15 PM, RicodJour <ricodj...@aol.com> wrote: > On Oct 31, 7:04 pm, nfmi...@comcast.net wrote:
> > Actually about 30 years ago, there was a lot of research done on this > subject for > > racing motorcycles (close enough to bikes).
> Maybe a racing motorcycle is akin to how you ride a bike, but it > certainly isn't how I ride a bicycle. Modeling a bicycle on any > bicycle would be closer, and modeling a touring bike on a touring bike > would be even closer still.
> As the guy hauling the firewood posted, you can adapt to pretty much > anything, and any particulars are dependent on the bike's geometry and > personal preference.
> R
> -- > You received this message because you are subscribed to the Google Groups > "Bicycle Lifestyle" group. > To post to this group, send email to bicyclelifestyle@googlegroups.com. > To unsubscribe from this group, send email to > bicyclelifestyle+unsubscribe@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/bicyclelifestyle?hl=en.
>> Actually about 30 years ago, there was a lot of research done on this >> subject for racing motorcycles (close enough to bikes).
> Maybe a racing motorcycle is akin to how you ride a bike, but it certainly > isn't how I ride a bicycle. Modeling a bicycle on any bicycle would be > closer, and modeling a touring bike on a touring bike would be even closer > still.
As single-track devices, bicycles and motorcycles are almost identical. They share the same parameters of geometry and weight and suspension and adhesion, and the same techniques of dynamic balance and control. Competitive endeavors such as racing and the military often fund research in various fields, because that's where the money is, and because that's the application that benefits most and first from expanding the known performance envelope.
On Nov 1, 12:24 pm, Lee Legrand <krm2...@gmail.com> wrote:
> Just because you can adapt to pretty much anything, it does not necessarily
> mean the bicycle is well designed for purpose of its use. For example, if
> were a pizza delivery guy that delivery pizza on a bicycle. You could
> probable do the job with a track bike, a racing bike (assuming fender
> mounts are there) and a porteur bicycle. You could adapt to how the all
> three bicycle handle stacks of pizza but would you say they are all equal
> or would pizza delivery be better on the porteur.
That's exactly my point, Lee. Generalities about bike handling with
respect to bag loads are almost meaningless. In this case, it _is_
about the bike, and it is about personal preference. Extrapolating
data from a racing motorcycle model isn't going to work for a
bicycle. Other than the two wheels, there are almost no similarities.
> >> Actually about 30 years ago, there was a lot of research done on this
> >> subject for racing motorcycles (close enough to bikes).
> > Maybe a racing motorcycle is akin to how you ride a bike, but it certainly
> > isn't how I ride a bicycle. Modeling a bicycle on any bicycle would be
> > closer, and modeling a touring bike on a touring bike would be even closer
> > still.
> As single-track devices, bicycles and motorcycles are almost identical.
> They share the same parameters of geometry and weight and suspension and
> adhesion, and the same techniques of dynamic balance and control.
Saying that is akin to saying that since both data can be plotted on x-
y axes, then the lines plotted must be similar. The differences in
weight and its distribution are huge. The rider weight on a bicycle
is probably at least double that of the bike and load (Big Dummies
excepted). The motorcycle scenario is almost exactly opposite that.
We're talking about riding a loaded bike at what - 15 MPH? with an
extremely limited power supply. I can't just twist my wrist and add a
few dozen horsepower to straighten things out. You can't stop
motorcycle shimmy by laying a thigh against the tank.
In essence you seem to be saying that handling is independent of
geometry and load.
> Competitive endeavors such as racing and the military often fund research
> in various fields, because that's where the money is, and because that's
> the application that benefits most and first from expanding the known
> performance envelope.
Agreed. I wish all conflicts could be settled by how fast someone was
on a bike, or how much load they could carry up a mountain.
On Tue, Nov 1, 2011 at 10:13 AM, RicodJour <ricodj...@aol.com> wrote: > On Nov 1, 12:30 pm, Bob Sutterfield <b...@sutterfields.us> wrote: > > RicodJour <ricodj...@aol.com> wrote: > > > Nigel <nfmi...@comcast.net> wrote: > > >> Actually about 30 years ago, there was a lot of research done on this > > >> subject for racing motorcycles (close enough to bikes).
> > > Maybe a racing motorcycle is akin to how you ride a bike, but it > certainly > > > isn't how I ride a bicycle. Modeling a bicycle on any bicycle would be > > > closer, and modeling a touring bike on a touring bike would be even > closer > > > still.
> > As single-track devices, bicycles and motorcycles are almost identical. > > They share the same parameters of geometry and weight and suspension and > > adhesion, and the same techniques of dynamic balance and control.
> Saying that is akin to saying that since both data can be plotted on x- > y axes, then the lines plotted must be similar. The differences in > weight and its distribution are huge. The rider weight on a bicycle > is probably at least double that of the bike and load (Big Dummies > excepted). The motorcycle scenario is almost exactly opposite that. > We're talking about riding a loaded bike at what - 15 MPH? with an > extremely limited power supply. I can't just twist my wrist and add a > few dozen horsepower to straighten things out. You can't stop > motorcycle shimmy by laying a thigh against the tank.
> In essence you seem to be saying that handling is independent of > geometry and load.
No, I'm saying those are the parameters that matter. Motorcycles might have different values than bicycles for parameters like trail, rake, wheelbase, rigidity, and unsprung mass, but neither bicycles or motorcycles have parameters like camber (on a multi-track vehicle, this measures how far a wheel is off vertical). Yes, the differences in weight and weight distribution are huge between bicycles and motorcycles. But when you're analyzing and modeling the dynamics of balance and control, those are just different values to plug into the same parameters.
As a motorcycle and bicycle rider, they ride noticeably different, in
addition to have lots of thrust available at the rear wheel to change
how a motorcycle turns, the difference is how a bicycle and motorcycle
counter steer is enormous at least from my perspective. I counter
steer my motorcycle and the bike will lean it self over and arc into
the turn. On a bicycle, I have to lean the bike first and then apply
counter steer, and even then it is pretty dicey compared to how steady
the motorbike is under a counter steer.
