Howzabout putting batteries in front? Not on the handlebars mind you but maybe the center pole via panniers. It seems thats the general ebike layout calls for too much weight in back. What woulld be the pros & cons of redistributing 10 or more pounds towards the front?
Front mounted batteries?
- Thread starter mst3kpimp
- Start date
Yeah but, then your steering effort gets weird. Also, large gauge wires tend to be less flexible, so you're sitting there flexing your battery wires all day.. not preferred!
Also, like rear mounting, you are putting the weight up high which is no good.
Frame mount is far, far better if you have the space.
You can build your own battery box from Home Depot parts, ya know. I am building one out of aluminum strips and sheet from home depot.. bolting the thing together. etc.
There is a guy on here who did a front handlebar battery mount though. I forget his name. He calls it a 'burrito pack' or something.
Also, like rear mounting, you are putting the weight up high which is no good.
Frame mount is far, far better if you have the space.
You can build your own battery box from Home Depot parts, ya know. I am building one out of aluminum strips and sheet from home depot.. bolting the thing together. etc.
There is a guy on here who did a front handlebar battery mount though. I forget his name. He calls it a 'burrito pack' or something.
I dont think there would be much 'flexing" of wires. they along with the batteries would mostly be static on the centerpole and not actually attached to any steering. I also wonder if the type of bike would be more of a factor. A beach cruiser seems to have the rider positioned more to the rear. Also in the case of a front hub motor setup the extra weight may help traction. Of course you could argue it would pose a threat to the strength of said fork.
ah, you mean front/mid mount.
Well, the lower you can mount the batteries, the better. This usually means mounting the batteries mid-frame or mid-rear, because on most bikes you don't have a lot of space in the front of the triangle..
My Currie Mongoose bike has a mid-rear battery and rear motor ( very heavy sort ) and it actually handles extremely well.
Rear motor is always best because rear dropouts are always stronger.
Well, the lower you can mount the batteries, the better. This usually means mounting the batteries mid-frame or mid-rear, because on most bikes you don't have a lot of space in the front of the triangle..
My Currie Mongoose bike has a mid-rear battery and rear motor ( very heavy sort ) and it actually handles extremely well.
Rear motor is always best because rear dropouts are always stronger.
TylerDurden
100 GW
Batteries up front near the headset are good, especially if you have a rear motor.
The challenge is usually keeping them from obstructing your knees.
There are numerous discussions here about battery placement, well worth reading.
The challenge is usually keeping them from obstructing your knees.
There are numerous discussions here about battery placement, well worth reading.
Tiberius
10 kW
TylerDurden said:
Exactly as TD says.
Have a search back through some of the discussions. There are cases where we go into some of the maths, and, be warned, cases where the discussion gets heated. For some reason, for a subject that is amenable to the maths, it gets controversial.
The idea that weight should always be down low keeps coming up but it is wrong. It applies to 4 wheeled vehicles and displacement vessels so it gets ingrained into everyone's consciousness and taken as obvious but it does not apply to 2 wheeled vehicles.
Have a look at the bike in my avatar. The batteries are built around the headset. They don't move with the handlebars so there isn't a wire flexing problem. They sit inside the volume swept by the drop handlebars.
Nick
liveforphysics
100 TW
That's very true. Leaning machines need to lean less to find the balance equilibrium needed to turn at a given rate if the weight is higher up. This enables higher cornering limits for a given tire profile.
The downside is technical manoverability though. There is certianly a reason why a trials motorcycle seats the engine just a few inches from the ground. Higher COG bikes also deliver the illusion of a heavier bike for the person riding, where very low COG bikes feel like riding a feather.
For myself, on a superbike weight up high is a winner. For a dirtbike, I like it as low as I can get it.
The downside is technical manoverability though. There is certianly a reason why a trials motorcycle seats the engine just a few inches from the ground. Higher COG bikes also deliver the illusion of a heavier bike for the person riding, where very low COG bikes feel like riding a feather.
For myself, on a superbike weight up high is a winner. For a dirtbike, I like it as low as I can get it.
dogman dan
1 PW
Well said, when the job is different, the tool should be different. Having ridden some now, on quite a few different builds, I think the problem is not so much too high as too far back on rear rack batteries. High or low carry is not nearly the issue carrying extremely front of back is.
One of my bikes had 8 pounds of nicac on the handlebars, mounted almost like a number plate. It was not so bad, but seemed to slow down steering imput reaction time. On that particular bike keeping the front wheel on the ground was the main problem, so the weight there was worth it.
One of my bikes had 8 pounds of nicac on the handlebars, mounted almost like a number plate. It was not so bad, but seemed to slow down steering imput reaction time. On that particular bike keeping the front wheel on the ground was the main problem, so the weight there was worth it.
Tiberius said:
hi/lo aside, what of the fore/aft?
the whole spinning bowling ball vs spinning a barbell momentum thing.
a bike of equal power & weight but centrally located will be more flickable & take u in the corners of a race.
tell me where i'm rong.
liveforphysics
100 TW
Toorbough ULL-Zeveigh said:
It's called polar moment.
It's the reason in a racing car, you want all the weight as low and in the center of the vehicle as possible.
Likewise, 50/50 weight distribution is NEVER optimal (for a car at least, I'm not sure about for a bike).
FWD vehicles tend to be optimized for everything from road racing to drag racing at roughly a 75% front, 25% rear split.
RWD vehicles tend to optimize for all driving conditions(except rally) somewhere around 30-40% front, to 70-60% rear.
The ideal percentage has a lot to do with the height of the COG of the vehicle and the tire compound.
The reason for this is that the traction you've got when the vehicle is not trying to change speed or direction in some way doesn't matter a bit. Think about that statement.
So, what conditions do you care about tire loading and traction etc? Braking. Turning. Accelerating. What happens to the weight balance during this events? Well, in braking, it all shifts up on the fronts, ideally the rear wheels should be on the verge of leaving the ground, or even leaving the ground in the case of FWD slick-tire road raceing cars. Then, as you're going through the turn, if you're racing, you were trail braking on entry to shift the weight to the front tires when they need to bite, then after you apex, you're rolling on the throttle to set the weight on the back tires. In other words, the tire static loading is never the conditions the vehicle is seeing during the times it requires traction, it's always dynamic tire loading that matters.
What I'm getting at here, is the ideal front/rear balance is going vary depending on the application.
would anyone care to pass judgment on the validity of this diagram?
it seems wrong but supposedly it's the result of trial & error from years of road racing experience.
every motorcycle magazine whenever the subject comes up always recommends hanging any kind of additional weight like jerry cans as close to axle height as possible.
and to avoid placing any unnecessary weight ahead of the steering axis, not even so much as a small light leather tool pouch hanging from the steer tubes below the headlight like i've seen sometimes.
it seems wrong but supposedly it's the result of trial & error from years of road racing experience.
every motorcycle magazine whenever the subject comes up always recommends hanging any kind of additional weight like jerry cans as close to axle height as possible.
and to avoid placing any unnecessary weight ahead of the steering axis, not even so much as a small light leather tool pouch hanging from the steer tubes below the headlight like i've seen sometimes.
Tiberius
10 kW
Toorbough ULL-Zeveigh said:
Ah yes, that's our old friend safe, and its the thread I was thinking of. Like it or not, safe was pretty much right all the way through that thread, when he stayed on technical matters.
Let's not repeat the whole discussion here, please. Let's just note that high up above the rear wheel is about the worst place to put weight, and, for some reason, a favourite place for batteries.
Nick
dogman dan
1 PW
Safe did have some correct stuff. I agree with the diagram too. Oddly though, it does seem to help if you've loaded one corner, to load the other. So the battery high rear combined with motor low front is tolerable. Not desireable, just tolerable. Desireable is more like the green diagram, rear hub, and frame mount battery. Still not the best it could be though, with all the wheel weight.
Tiberius said:
hmm, yes... if 'safe' were to say the sky is blu sure he happens to be right but whenever he sez it i'll always rush out to verify for myself that it's still the case.
and it don't make it safe's blu sky just cuz it came from his lips.
well i'd rather side with Tony Foale that the green zone for optimal weight placement to minimize impact on handling is right at axle height.
like it or not there's several thousand practitioners out there of this configuration ebike with 25 lbs centered on each axle that have been rolling along just fine for over half a decade now.
but rather than continually debate this it should be verifiable experimentally.
what sort of evidence would it take that you would be willing to accept?
wrest the Tour de Presteigne title from your clenched fingers?
If you look at Evoforce's build3, you'll see his battery boxes are along the sides of the toptube from the seatpost up to and just forward of the headtube. Despite their weight it appears to handle well, based on what I saw at the Undead Race.
My own CrazyBike2 has it's batteries in the same place as a motorcycle engine would be, down low in the center of the frame between my legs, in front of the seat, but behind the pedals. For it's length, it handles pretty well. They are about at axle height.
DayGlo Avenger has the batteries in a side-pannier below and in front of the rear axle, just behind the pedals. It handles pretty well but would be better if they were on the centerline of the bike--you can feel the difference in turns. I've had them forward, in the triangle, with heavy SLA, and it was ok but because I had them much higher vertically it didn't feel as "right" as they do down low even though they're farther rearward. Part of that is probably because the heavy 9C front hubmotor helps balance that rearward weight, and I had no front wheel weight with the SLA. When I had the SLA in rear baskets, above the axle, it was nowhere near as good as now.
Same principles apply to cargo loading, which is what I learned before I ever started the ebike quest.
My own CrazyBike2 has it's batteries in the same place as a motorcycle engine would be, down low in the center of the frame between my legs, in front of the seat, but behind the pedals. For it's length, it handles pretty well. They are about at axle height.
DayGlo Avenger has the batteries in a side-pannier below and in front of the rear axle, just behind the pedals. It handles pretty well but would be better if they were on the centerline of the bike--you can feel the difference in turns. I've had them forward, in the triangle, with heavy SLA, and it was ok but because I had them much higher vertically it didn't feel as "right" as they do down low even though they're farther rearward. Part of that is probably because the heavy 9C front hubmotor helps balance that rearward weight, and I had no front wheel weight with the SLA. When I had the SLA in rear baskets, above the axle, it was nowhere near as good as now.
Same principles apply to cargo loading, which is what I learned before I ever started the ebike quest.
Tiberius
10 kW
Toorbough ULL-Zeveigh said:....but rather than continually debate this it should be verifiable experimentally.
what sort of evidence would it take that you would be willing to accept?
wrest the Tour de Presteigne title from your clenched fingers?
The key word there is evidence. It's so much better to test a hypothesis than to judge it according to who you heard it from.
Personally, I place a lot of weight on maths and science. If the equations hang together and produce useful results then I tend to trust them and use them. A lot of the stuff spoken and written on this subject doesn't even accord with Newton's First Law, let alone anything more complicated.
I also agree that race results are a lot better indicators than people's anecdotes. But remember there are different types of race. The point has already been made that hard surface racing is different to trials riding and people use different weight placements.
Nick
dingoEsride
100 kW
Some very good quotes on the law of P.
Yeah I remember someone with bags low down over his front wheel, it was used for long uphills, but don't think it would be good for low speed manouvers
neptronix said:
Yeah I remember someone with bags low down over his front wheel, it was used for long uphills, but don't think it would be good for low speed manouvers
Tiberius said:
it's why i question everything regardless of who said it be it 'safe', foale or sir isaac.
even the math can be misapplied resulting in nothing more than gigo, reality trumps theory & math.
to answer the OP, when tested against my own experience i find that it's very consistent with what's in foale's book on Motorcycle handling and chassis design.
which i provided u the link in a previous thread but i guess nobody bothered to read the one relevant page on weight distribution so i'll paraphrase some of the key points (imo):
BALANCElo COG facilitates good balance, the unbalancing couple is directly proportional to COG height.
otoh hi COG is easier to stay balanced upright at lo speed due to the longer lever moment than a lo COG.
LOAD TRANSFERlowering the mass centre height decreases the load transfer.
load transfer is not affected by the longitudinal location of the COG.
TRACTIONrear weight bias increases traction.
front weight bias improvess directional stability as it does in a dart or an arrow.
stated in another way, having weight out front resists quickly changing direction, i.e. harder to 'flik'.
LEAN ANGLEthe lean angle for balance when cornering is slightly affected by the COG height.
higher COG requires more lean than a lo COG for the same radius turn.
if u go by that then for casual cruising mostly in a straight line as on ur typical commuter & be prepared to take sharp turns a little slower then mounting the battery up hi near the front is all good.
FWIW i've had my batteries exclusively in safe's red zones for the last 10k miles.
with the batteries mounted lo forward it's very docile whereas up on the rear rack the bike really carves but u quickly acclimate to either setup.
that's why i tend to agree with this sentiment (actually i've agreed with just about everything he's ever said, it's always just good common sense) that a few extra pounds (<20 even?) can be put just about anywhere on a bike without drastic change in handling, unless ur racing & absolutely require every last little advantage.
Drunkskunk said:
MadRhino
100 GW
I mounted the weight on my Marzocchi triple crown fork with 3 u-bolts. The bag has a rigid PVC box inside, containing the batteries (18s 3p lipo), I also carry some tools, a big 4pd cable lock, and even the lunch sometimes. If you look at the picture, the bag is under my handlebar, in the axis between handlebar mount and wheel axle. It does not affect steering and it's weight is no disturbance at all, the bike still jumps in balance cause the weight of the full bag is about the same as my Clyte motor.
The only downsides: The bag hides the front wheel from my sight on rough downhill trails, it also makes the bike heavy to handle when not seated on it, but not so much of a broblem there. I need to see my front wheel, that is why I plan to mount the batteries on the frame, but keeping them as much in the front as I can.
The only downsides: The bag hides the front wheel from my sight on rough downhill trails, it also makes the bike heavy to handle when not seated on it, but not so much of a broblem there. I need to see my front wheel, that is why I plan to mount the batteries on the frame, but keeping them as much in the front as I can.
dumbass
100 kW
On this bike I can run ether twin 24v 18ah SLAs or twin 24v 20ah lifepo4 packs.
docnjoj
1 GW
I have found that on a tadpole trike the weight should be mounted low and central, more like a race car. I noticed a clear detrimental change when mounting 15-20 lbs of batteries on my rear carrier. The rear end oversteered to a significant degree while in current configuration (lexan mount low and under seat) the trike drifts in a neutral steering stance. Needless to say I have "slowed down" in recent years and only tip over about once a month! 
otherDoc
otherDoc
