Mounting your battery, Center of Gravity.

[Ypedal]

It took an X5302 in a 20" wheel with 48v 12ah sla in a backpack, going WELL OVER 40 mph before countersteer became aparent.. :lol: ( I still remember the front tire bulging as my eyes were watering like mad.. )

*deleted my own 400 word piece of mind regarding safe's contributions to this thread...

 

[John in CR]

I'm just curious....

There's a lot of talk here about countersteering. How many folks here actually use countersteering with their e-bikes (not e-cycles)? Because the OP was asking about where to mount on a bicycle. I can't say that I've ever used countersteering on my bike. I would hazard to guess that most folks here are using their e-bikes for commuting, not racing. So aren't we getting a little off track here?

Michael,
Countersteer isn't something you consciously do. You do it too naturally I'm sure, because the alternative is turning by only leaning which requires more of a conscious effort. It's such a subconscious thing that early in the thread my knee jerk reaction didn't consider it. It's just a subtle turn of the handlebars briefly that sets up the turn in a very natural way.
John

 

[lostcoyote]

Countersteer isn't something you consciously do. You do it too naturally I'm sure, because the alternative is turning by only leaning which requires more of a conscious effort. It's such a subconscious thing that early in the thread my knee jerk reaction didn't consider it. It's just a subtle turn of the handlebars briefly that sets up the turn in a very natural way.
John

exactly. and you would probably not even notice a countersteer if it was say, only a few millimeters - but it exists in all bike turns. like driving a car, it iks probably subconscious, if even that.
also, safe, there is more than simple linear momentum in your arguments. you need to include several angular momentum terms, all of which must be superimposed to correctly model what you're attempting to do rather simplistically.
(read the physics paper several posts above to see why)

what the h*ll does it matter anyways as far as this topic goes?

 

[marvingalaxy]

"I can't say that I've ever used countersteering on my bike."

Yep, every time you turn you use countersteer. You don't even realize it because it is automated in your brain. It is incredibly complex and you figured out how to do it probably when you were about 6 years old without understanding a bit of the physics in any intellectual fashion. That is how good our brains are at balance and upright mobility. In fact, the more you sit upright and don't lean like a racer the more you are depending on countersteer. If you don't counter, you would go over the handlebars as your bike would be pulled toward the turn and your body momentum would keep you moving in a straight line. If you don't lean your body in relation to the bike, you must first force the bike to lean a bit in the opposite direction to force your momentum to start pulling you into a fall. Then, you immediately correct the fall by steering toward the turn and at the end of the turn you oversteer to force your weight back upright. If you don't oversteer at the end of the turn, you will go in a circle.

Where countersteer turning is relevant to the mounting of a battery box is how weight effects handling.

Great weight down low will cause slow steering response in rapid maneuvers as that mass must shift left and right. Too much non-dynamic weight up high will cause the bike to tip over on it's kickstand or while pushing. Is it okay to have weight down low or up high? Yes. Just be aware that the handling will be different for both. If you like the feel of scooters with their heavy batteries down low, that is the place for you. If you like the fast steering response of weight up high in the center, guess where to put your battery box?

Unless you weigh less than your bike, the momentum pivots mostly around your body. Fastest response means putting the weight in the center with you. Having a battery in your lap is not practical.

Regardless of any weight, the bike changes direction due to the contact patches of the tires. If it doesn't, you are in a skid.

The momentum and contact patches are used against each other to accomplish the goal of keeping our body's momentum going in directions of our choosing. If you have the impression from reading this thread that momentum, gyroscopic forces, and contact patches are all doing the same thing, they are not. The rider takes advantage of these different forces to maintain stability in a straight line and to control the chaos of a turn.

************************

BTW! It is entirely possible to turn without leaning the bike and using countersteer. You must move your body way into the inside of the turn to keep the momentum flowing correctly but it is uncomfortable. I've even turned right while leaning the bike left. If you sit still in your seat and don't lean your body, you must lean the bike and the rider together by using countersteer at the beginning. Since your battery box is fixed to the bike, you must factor in how it effects the leaning characteristics of the bike.

 

[John in CR]

also, safe, there is more than simple linear momentum in your arguments. you need to include several angular momentum terms, all of which must be superimposed to correctly model what you're attempting to do rather simplistically.
(read the physics paper several posts above to see why)

what the h*ll does it matter anyways as far as this topic goes?

lostcoyote,

There's a simple way to explain what Safe is trying to get at, and which is that you want the center of mass to go in as straight a line as possible, but then if he made a simple and correct statement like that, he wouldn't get the arguments that he loves. Where exactly you place the batteries on the bike to achieve that, become far more complex due to the rider's greater mass and flexible connection to the bike, not to mention how different riding conditions will affect the optimum too. eg The member with the commute up a rocky mountain road dodging river stones will require significantly different handling than someone with nice smooth bike paths for their commute.

btw, I couldn't get through on your link above.

John

 

[TylerDurden]

Ja, the Berkeley paper describes a process:

• Counter-steering is employed
  by both motorcyclists and bicyclists, though most bicyclists
  counter-steer unconsciously. You may have noticed, however,
  that while on a bicycle, it is surprisingly difficult to ride
  clear of a nearby high curb or sharp drop. This is because
  you must steer towards the edge to get away from the edge.
  It is easy to directly demonstrate counter-steering on a bicycle.
  While riding at a brisk pace ~possibly downhill to
  avoid the complications of peddling!, let go with your left
  hand while pushing the right handlebar with the open palm
  of your right hand. Since your hand is open, you can only
  turn the handlebar left, but the bike will turn right.

 

[John in CR]

"I can't say that I've ever used countersteering on my bike."

Yep, every time you turn you use countersteer. You don't even realize it because it is automated in your brain. It is incredibly complex and you figured out how to do it probably when you were about 6 years old without understanding a bit of the physics in any intellectual fashion. That is how good our brains are at balance and upright mobility. In fact, the more you sit upright and don't lean like a racer the more you are depending on countersteer. If you don't counter, you would go over the handlebars as your bike would be pulled toward the turn and your body momentum would keep you moving in a straight line. If you don't lean your body in relation to the bike, you must first force the bike to lean a bit in the opposite direction to force your momentum to start pulling you into a fall. Then, you immediately correct the fall by steering toward the turn and at the end of the turn you oversteer to force your weight back upright. If you don't oversteer at the end of the turn, you will go in a circle.

Where countersteer turning is relevant to the mounting of a battery box is how weight effects handling.

Great weight down low will cause slow steering response in rapid maneuvers as that mass must shift left and right. Too much non-dynamic weight up high will cause the bike to tip over on it's kickstand or while pushing. Is it okay to have weight down low or up high? Yes. Just be aware that the handling will be different for both. If you like the feel of scooters with their heavy batteries down low, that is the place for you. If you like the fast steering response of weight up high in the center, guess where to put your battery box?

Unless you weigh less than your bike, the momentum pivots mostly around your body. Fastest response means putting the weight in the center with you. Having a battery in your lap is not practical.

Regardless of any weight, the bike changes direction due to the contact patches of the tires. If it doesn't, you are in a skid.

The momentum and contact patches are used against each other to accomplish the goal of keeping our body's momentum going in directions of our choosing. If you have the impression from reading this thread that momentum, gyroscopic forces, and contact patches are all doing the same thing, they are not. The rider takes advantage of these different forces to maintain stability in a straight line and to control the chaos of a turn.

************************

BTW! It is entirely possible to turn without leaning the bike and using countersteer. You must move your body way into the inside of the turn to keep the momentum flowing correctly but it is uncomfortable. I've even turned right while leaning the bike left. If you sit still in your seat and don't lean your body, you must lean the bike and the rider together by using countersteer at the beginning. Since your battery box is fixed to the bike, you must factor in how it effects the leaning characteristics of the bike.

Nice post Marvin. I've got to try some of your turning tricks. Some of that may come in handy when I don't see a missing manhole cover early enough, which are incredibly common down here.

John

 

[marvingalaxy]

John, the missing manhole is a perfect example of where you want no weight down low to do this kind of maneuver. If you have the guts to practice this, you can eventually get to a point where you can keep your upper body moving in a straight line but throw the bike way out from under you. Of course, you must QUICKLY counter this maneuver by yanking the bike the other way so your body doesn't fall to the ground. An interesting exercise might be to use a light bike and ride over a point trying to keep your body still but have the tires go around that point. Slalom the bike but keep the rider still. Of course, do this with protective gear like a helmet and gloves in an area without traffic.

Think of a snow skier (sp?) going downhill. Often you will see them moving their skis and legs left and right rapidly to avoid moguls or to bleed off speed but their body stays almost in a straight line. If they had 50-pound skis (like a bike with 50 pounds down low), they wouldn't be able to do those maneuvers.

I have noticed another odd behavior while watching motorcycle riders and I have sometimes done it myself. I have actually leaned into the turn a bit like the fast motorcycle riders as this keeps the bike more upright. Keeping the bike a bit more upright in a very sharp turn can help keep the good contact area of the tire on the ground. Some tires don't have much grip on the sides and a severe lean will cause the bike to go out from under you when you hit this area of the sidewall. Leaning your body instead of the bike keeps the contact closer to the center of the tire where there is better grip. This only needs to be done if your are in severe riding and know you are exceeding the limits of your sidewalls. I haven't done anything like that in 20 years.

I forgot to mention that weight in the back won't prevent the front from weaving quickly. My guess is that a lot of weight out back will increase inertia back there and a fast weave maneuver might cause the rear to start the weave more slowly and to maybe skid out once it gets moving and wants to keep moving sideways. I'm guessing people put weight in the back because it is much safer for your back tire to slide. If it slides, you will see riders stick their leg out and catch themselves in a turn and keep going. If the front tire slides, you tend to land not on your foot but on your hands and face. Also, as long as the front tire is unencumbered it will get around the obstacle and prevent an endover from a pothole. As the back tire moves more slowly, it may hit that pothole but with forces that are less likely to damage the rider and that is the ultimate goal. Of course, if you maneuver the front tire to the side and the rear hits a pothole, you might not be able to perform the opposite steering maneuver to get the bike upright again. You will probably fall flat on your face on the opposite side of the bike from where the front tire went and past the pothole/manhole. Anything is better than an endover.

 

[TylerDurden]

Think of a snow skier (sp?) going downhill. Often you will see them moving their skis and legs left and right rapidly to avoid moguls or to bleed off speed but their body stays almost in a straight line. If they had 50-pound skis (like a bike with 50 pounds down low), they wouldn't be able to do those maneuvers.

Another good example would be the sharp turns hockey players make: legs waaayyy out... hips & torso extremely low, at the center of rotation.

 

[michaelplogue]

Ah.... I was thinking Counter Steering - when you're leaning the bike down low and turning your wheel in the opposite direction of the turn...... The counter turn you speak of is a widening of the turn in order to get a better angle of attack at it...... Gotcha!

 

[gogo]

Then there is the matter of looking where you want to go. If you look at a pothole, you will drive straight over it. If you look at a path that goes to the side of the pothole, you will go around the pothole. Try it.

 

[John in CR]

Guys,

I'm not too sure about either the skier or skater comparisons, since the rear wheel is fixed. I'd have to defer to your greater experience relating to such an aggressive bike maneuver. I think such an emergency or off road move bears further discussion regarding best battery placement on the bike to pull it off (in your backpack doesn't count.).

I'd think anywhere forward is out, since it's going to require a strong turn and push of the handlebars. It seems that high over the tire is going to slow what you do with the front. It really just leaves the rear and low, which assuming no lift or slip is going only where the front leads it weight or not. Please help me analyze this, because while it's far more radical than I'm likely to encounter, smaller but quite similar moves may be common, ie get the bike around something while your body maintains a mostly straight line.

John

 

[jmygann]

can a 48 volt 20ahr LIFEPO4 pack be split into 2 connected packs with 1 charger and bms by lengthing the wires ?
I want to put the 2 packs on each side of the bike tube - 3 in

 

[John in CR]

can a 48 volt 20ahr LIFEPO4 pack be split into 2 connected packs with 1 charger and bms by lengthing the wires ?
I want to put the 2 packs on each side of the bike tube - 3 in

Yes, and it's pretty simple. I just split one of my ping packs in half for exactly that purpose. I just very carefully cut through the duct tape, and split the BMS ribbon cable in half. I only had one hard soldered tab connection to separate and add a length of thick wire to restore the connection. Add some duct tape and it's ready for some kind of small saddlebag type rack.

John

 

[marvingalaxy]

"I'm not too sure about either the skier or skater comparisons, since the rear wheel is fixed."

The skier and skater are a good analogy for the front tire only. Bikes certainly differ in that they have a trailing wheel. The longer the wheelbase the less reactive that rear wheel becomes. I'm trying to find some good bicycling youtube videos but most of the slalom that is not at a crawling pace is with motorcycles. I noticed that the front wheel moves dramatically more than the rear wheel and the rider. The horizontal pivot axis does seem to be at about the riders hips.

 

[SteveMush]

....Now if somone could do a dynamic analysis of the path my body took 15 years ago after I went over the handlebars at speed after getting hit in a turn and split ny helmet against a mailbox....

I wasn't awake for the flight and I've always been curious if I flipped before I woke up on the grass...

 

[TylerDurden]

"I'm not too sure about either the skier or skater comparisons, since the rear wheel is fixed."
The skier and skater are a good analogy for the front tire only. Bikes certainly differ in that they have a trailing wheel.

Actually, the skater analogy is better than the skier... the fastest skate turns require the feet to be in a straight line (one ahead of the other), equal weight on both skates. Getting the blades (contact-patches) far out from under the skater allows significant lateral force against the momentum of the body. 250lbs of skater going 20mph can turn 180* in ~6' of space.

@JCR: I'll attach the pdf here, to see if you can download... it is science-heavy but reads well for non-techies like meeself.
It should answer all questions about the dynamics involved.
View attachment SteerBikeAJP.pdf

 

[John in CR]

TD,

Good paper and incorporated movement and bending of the body, but on first pass doesn't tell me the best place for batteries on the bike for pothole dodging. wrt the hockey player, it's like a bike where both wheels turn enabling both contact patches at the skate to get both out from under your weight. On a bike the rear wheel just follows. Since we will likely have to whip the frame to one side or the other combined with a handlebar turn, I can't get past the idea that the rear wheel contact patch being the single ideal place for added weight in terms of bike handling without being in a backpack.

Weight up high will slow side to side movement of the frame, which is anchored at the rear contact patch (front patch too). Weight in front will slow turning the frame left or right, which is also anchored at the rear contact patch. Anything done with the bike with both wheels on the ground, including countersteer etc., is one or a combination of these two things regardless of speed, and regardless of what you do with your body weight. Of course we can't put the batteries there, but it's a starting point for where they belong, though I'm sure there are things like front to rear weight distribution for best traction and other stuff that should be discussed.

John

 

[safe]

Adding Some Humor

Just a reminder not to take this too seriously... enjoy! :lol:

 

[John in CR]

Safe,

No need to say "Adding Some Humor". I find humor in almost all of your posts. How about an original thought instead of copy paste of some marketing hype. Other than a sucker, who would believe anything said by people selling bikes for $13K anyway?

John

 

[safe]

Aprilia Enjoy

Aprilia has a long history of success in motorcycle road racing. Their best engineers took all their combined knowledge over the years and basically came up with the same result as the Optibike.

The future of ebikes will be the pasts "best wisdom"... it will be "reform" of todays incorrect designs in favor of the more well established earlier designs.

It's inevitable... right now these bikes are rare, but eventually they will be the new "status quo". (it might take 10 years to get there though :? )

 

[TylerDurden]

TD,

Good paper and incorporated movement and bending of the body, but on first pass doesn't tell me the best place for batteries on the bike for pothole dodging. wrt the hockey player, it's like a bike where both wheels turn enabling both contact patches at the skate to get both out from under your weight. On a bike the rear wheel just follows. Since we will likely have to whip the frame to one side or the other combined with a handlebar turn, I can't get past the idea that the rear wheel contact patch being the single ideal place for added weight in terms of bike handling without being in a backpack.

Weight up high will slow side to side movement of the frame, which is anchored at the rear contact patch (front patch too). Weight in front will slow turning the frame left or right, which is also anchored at the rear contact patch. Anything done with the bike with both wheels on the ground, including countersteer etc., is one or a combination of these two things regardless of speed, and regardless of what you do with your body weight. Of course we can't put the batteries there, but it's a starting point for where they belong, though I'm sure there are things like front to rear weight distribution for best traction and other stuff that should be discussed.

Forgive my oversimplification:
The front contact patch is the only control you have, so giving it the most mobility should provide the most control. Having weight down near the front CP will slow the rider's ability to move the CP about. If the weight in front is higher, the CP can be more easily positioned for greater force against the mass' momentum.

More mass near the rear contact patch delays the influence the front CP can provide. At higher speed, the mass will continue in it's original direction, so even if you have enough weight up front to keep the front CP from slipping in a fast turn, the back will try to wag the dog, since the rear wheel turns more slowly with the frame (as opposed to turning like the fork).

 

[lostcoyote]

maybe you guys can do some experimentation with a conventional bike using weights placed a bag that gets attched at various locations you set up for comparison.
use like a 20 pound weight and try these comparisons:

1. on the handle bars - lol
2. above the rear tire
3. low at the crank
4. low at the rear axle
5. low in the middle of the downtube


and then just see what you like best - set up a course where the turns are consistant and at the same speed.

(it would be a subjectiuve call in some of the comparisons)

 

[TylerDurden]

On the handlebars ain't that bad when you're moving (as long as it is close to the steering tube)... totally sux when parked.

 

[jmygann]

can a 48 volt 20ahr LIFEPO4 pack be split into 2 connected packs with 1 charger and bms by lengthing the wires ?
I want to put the 2 packs on each side of the bike tube - 3 in

Yes, and it's pretty simple. I just split one of my ping packs in half for exactly that purpose. I just very carefully cut through the duct tape, and split the BMS ribbon cable in half. I only had one hard soldered tab connection to separate and add a length of thick wire to restore the connection. Add some duct tape and it's ready for some kind of small saddlebag type rack.

John

I figure it would look like this

[imghttp://i12.ebayimg.com/06/i/001/06/20/efb8_10.JPG][/img]